draft-ietf-acme-acme-05.txt   draft-ietf-acme-acme-06.txt 
Network Working Group R. Barnes ACME Working Group R. Barnes
Internet-Draft Mozilla Internet-Draft Mozilla
Intended status: Standards Track J. Hoffman-Andrews Intended status: Standards Track J. Hoffman-Andrews
Expires: August 7, 2017 EFF Expires: September 14, 2017 EFF
J. Kasten J. Kasten
University of Michigan University of Michigan
February 03, 2017 March 13, 2017
Automatic Certificate Management Environment (ACME) Automatic Certificate Management Environment (ACME)
draft-ietf-acme-acme-05 draft-ietf-acme-acme-06
Abstract Abstract
Certificates in the Web's X.509 PKI (PKIX) are used for a number of Certificates in PKI using X.509 (PKIX) are used for a number of
purposes, the most significant of which is the authentication of purposes, the most significant of which is the authentication of
domain names. Thus, certificate authorities in the Web PKI are domain names. Thus, certificate authorities in the Web PKI are
trusted to verify that an applicant for a certificate legitimately trusted to verify that an applicant for a certificate legitimately
represents the domain name(s) in the certificate. Today, this represents the domain name(s) in the certificate. Today, this
verification is done through a collection of ad hoc mechanisms. This verification is done through a collection of ad hoc mechanisms. This
document describes a protocol that a certificate authority (CA) and document describes a protocol that a certification authority (CA) and
an applicant can use to automate the process of verification and an applicant can use to automate the process of verification and
certificate issuance. The protocol also provides facilities for certificate issuance. The protocol also provides facilities for
other certificate management functions, such as certificate other certificate management functions, such as certificate
revocation. revocation.
DISCLAIMER: This is a work in progress draft of ACME and has not yet DISCLAIMER: This is a work in progress draft of ACME and has not yet
had a thorough security analysis. had a thorough security analysis.
RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH: The source for RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH: The source for
this draft is maintained in GitHub. Suggested changes should be this draft is maintained in GitHub. Suggested changes should be
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 7, 2017. This Internet-Draft will expire on September 14, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Deployment Model and Operator Experience . . . . . . . . . . 5 2. Deployment Model and Operator Experience . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
5. Message Transport . . . . . . . . . . . . . . . . . . . . . . 8 5. Character Encoding . . . . . . . . . . . . . . . . . . . . . 8
5.1. HTTPS Requests . . . . . . . . . . . . . . . . . . . . . 8 6. Message Transport . . . . . . . . . . . . . . . . . . . . . . 8
5.2. Request Authentication . . . . . . . . . . . . . . . . . 9 6.1. HTTPS Requests . . . . . . . . . . . . . . . . . . . . . 9
5.3. Equivalence of JWKs . . . . . . . . . . . . . . . . . . . 11 6.2. Request Authentication . . . . . . . . . . . . . . . . . 9
5.4. Request URI Integrity . . . . . . . . . . . . . . . . . . 11 6.3. Request URI Integrity . . . . . . . . . . . . . . . . . . 10
5.4.1. "url" (URL) JWS header parameter . . . . . . . . . . 12 6.3.1. "url" (URL) JWS header parameter . . . . . . . . . . 11
5.5. Replay protection . . . . . . . . . . . . . . . . . . . . 12 6.4. Replay protection . . . . . . . . . . . . . . . . . . . . 11
5.5.1. Replay-Nonce . . . . . . . . . . . . . . . . . . . . 13 6.4.1. Replay-Nonce . . . . . . . . . . . . . . . . . . . . 12
5.5.2. "nonce" (Nonce) JWS header parameter . . . . . . . . 13 6.4.2. "nonce" (Nonce) JWS header parameter . . . . . . . . 12
5.6. Rate limits . . . . . . . . . . . . . . . . . . . . . . . 13 6.5. Rate limits . . . . . . . . . . . . . . . . . . . . . . . 13
5.7. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.6. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Certificate Management . . . . . . . . . . . . . . . . . . . 16 7. Certificate Management . . . . . . . . . . . . . . . . . . . 15
6.1. Resources . . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Resources . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1.1. Directory . . . . . . . . . . . . . . . . . . . . . . 18 7.1.1. Directory . . . . . . . . . . . . . . . . . . . . . . 17
6.1.2. Account Objects . . . . . . . . . . . . . . . . . . . 20 7.1.2. Account Objects . . . . . . . . . . . . . . . . . . . 19
6.1.3. Order Objects . . . . . . . . . . . . . . . . . . . . 21 7.1.3. Order Objects . . . . . . . . . . . . . . . . . . . . 20
6.1.4. Authorization Objects . . . . . . . . . . . . . . . . 23 7.1.4. Authorization Objects . . . . . . . . . . . . . . . . 22
6.2. Getting a Nonce . . . . . . . . . . . . . . . . . . . . . 24 7.2. Getting a Nonce . . . . . . . . . . . . . . . . . . . . . 23
6.3. Account Creation . . . . . . . . . . . . . . . . . . . . 25 7.3. Account Creation . . . . . . . . . . . . . . . . . . . . 24
6.3.1. Changes of Terms of Service . . . . . . . . . . . . . 27 7.3.1. Changes of Terms of Service . . . . . . . . . . . . . 26
6.3.2. External Account Binding . . . . . . . . . . . . . . 28 7.3.2. External Account Binding . . . . . . . . . . . . . . 27
6.3.3. Account Key Roll-over . . . . . . . . . . . . . . . . 30 7.3.3. Account Key Roll-over . . . . . . . . . . . . . . . . 29
6.3.4. Account deactivation . . . . . . . . . . . . . . . . 32 7.3.4. Account deactivation . . . . . . . . . . . . . . . . 31
6.4. Applying for Certificate Issuance . . . . . . . . . . . . 33 7.4. Applying for Certificate Issuance . . . . . . . . . . . . 32
6.4.1. Pre-Authorization . . . . . . . . . . . . . . . . . . 35 7.4.1. Pre-Authorization . . . . . . . . . . . . . . . . . . 34
6.4.2. Downloading the Certificate . . . . . . . . . . . . . 37 7.4.2. Downloading the Certificate . . . . . . . . . . . . . 36
6.5. Identifier Authorization . . . . . . . . . . . . . . . . 39 7.5. Identifier Authorization . . . . . . . . . . . . . . . . 37
6.5.1. Responding to Challenges . . . . . . . . . . . . . . 40 7.5.1. Responding to Challenges . . . . . . . . . . . . . . 38
6.5.2. Deactivating an Authorization . . . . . . . . . . . . 42 7.5.2. Deactivating an Authorization . . . . . . . . . . . . 40
6.6. Certificate Revocation . . . . . . . . . . . . . . . . . 43 7.6. Certificate Revocation . . . . . . . . . . . . . . . . . 41
7. Identifier Validation Challenges . . . . . . . . . . . . . . 45 8. Identifier Validation Challenges . . . . . . . . . . . . . . 43
7.1. Key Authorizations . . . . . . . . . . . . . . . . . . . 47 8.1. Key Authorizations . . . . . . . . . . . . . . . . . . . 45
7.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . . 47 8.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7.3. TLS with Server Name Indication (TLS SNI) . . . . . . . . 50 8.3. TLS with Server Name Indication (TLS SNI) . . . . . . . . 48
7.4. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 8.4. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
7.5. Out-of-Band . . . . . . . . . . . . . . . . . . . . . . . 54 8.5. Out-of-Band . . . . . . . . . . . . . . . . . . . . . . . 52
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 53
8.1. Well-Known URI for the HTTP Challenge . . . . . . . . . . 55 9.1. MIME Type: application/pem-certificate-chain . . . . . . 53
8.2. Replay-Nonce HTTP Header . . . . . . . . . . . . . . . . 55 9.2. Well-Known URI for the HTTP Challenge . . . . . . . . . . 54
8.3. "url" JWS Header Parameter . . . . . . . . . . . . . . . 56 9.3. Replay-Nonce HTTP Header . . . . . . . . . . . . . . . . 54
8.4. "nonce" JWS Header Parameter . . . . . . . . . . . . . . 56 9.4. "url" JWS Header Parameter . . . . . . . . . . . . . . . 54
8.5. URN Sub-namespace for ACME (urn:ietf:params:acme) . . . . 56 9.5. "nonce" JWS Header Parameter . . . . . . . . . . . . . . 55
8.6. New Registries . . . . . . . . . . . . . . . . . . . . . 57 9.6. URN Sub-namespace for ACME (urn:ietf:params:acme) . . . . 55
8.6.1. Fields in Account Objects . . . . . . . . . . . . . . 57 9.7. New Registries . . . . . . . . . . . . . . . . . . . . . 55
8.6.2. Fields in Order Objects . . . . . . . . . . . . . . . 58 9.7.1. Fields in Account Objects . . . . . . . . . . . . . . 56
8.6.3. Error Codes . . . . . . . . . . . . . . . . . . . . . 59 9.7.2. Fields in Order Objects . . . . . . . . . . . . . . . 57
8.6.4. Resource Types . . . . . . . . . . . . . . . . . . . 59 9.7.3. Error Types . . . . . . . . . . . . . . . . . . . . . 58
8.6.5. Identifier Types . . . . . . . . . . . . . . . . . . 60 9.7.4. Resource Types . . . . . . . . . . . . . . . . . . . 58
8.6.6. Challenge Types . . . . . . . . . . . . . . . . . . . 60 9.7.5. Identifier Types . . . . . . . . . . . . . . . . . . 59
9. Security Considerations . . . . . . . . . . . . . . . . . . . 61 9.7.6. Challenge Types . . . . . . . . . . . . . . . . . . . 59
9.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 62 10. Security Considerations . . . . . . . . . . . . . . . . . . . 60
9.2. Integrity of Authorizations . . . . . . . . . . . . . . . 63 10.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 61
9.3. Denial-of-Service Considerations . . . . . . . . . . . . 65 10.2. Integrity of Authorizations . . . . . . . . . . . . . . 62
9.4. Server-Side Request Forgery . . . . . . . . . . . . . . . 65 10.3. Denial-of-Service Considerations . . . . . . . . . . . . 64
9.5. CA Policy Considerations . . . . . . . . . . . . . . . . 66 10.4. Server-Side Request Forgery . . . . . . . . . . . . . . 65
10. Operational Considerations . . . . . . . . . . . . . . . . . 67 10.5. CA Policy Considerations . . . . . . . . . . . . . . . . 65
10.1. DNS over TCP . . . . . . . . . . . . . . . . . . . . . . 67 11. Operational Considerations . . . . . . . . . . . . . . . . . 66
10.2. Default Virtual Hosts . . . . . . . . . . . . . . . . . 67 11.1. DNS security . . . . . . . . . . . . . . . . . . . . . . 66
10.3. Use of DNSSEC Resolvers . . . . . . . . . . . . . . . . 68 11.2. Default Virtual Hosts . . . . . . . . . . . . . . . . . 67
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 68 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 67
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 69 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 68
12.1. Normative References . . . . . . . . . . . . . . . . . . 69 13.1. Normative References . . . . . . . . . . . . . . . . . . 68
12.2. Informative References . . . . . . . . . . . . . . . . . 71 13.2. Informative References . . . . . . . . . . . . . . . . . 70
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 71
1. Introduction 1. Introduction
Certificates in the Web PKI [RFC5280] are most commonly used to Certificates [RFC5280] in the Web PKI are most commonly used to
authenticate domain names. Thus, certificate authorities in the Web authenticate domain names. Thus, certificate authorities in the Web
PKI are trusted to verify that an applicant for a certificate PKI are trusted to verify that an applicant for a certificate
legitimately represents the domain name(s) in the certificate. legitimately represents the domain name(s) in the certificate.
Different types of certificates reflect different kinds of CA Different types of certificates reflect different kinds of CA
verification of information about the certificate subject. "Domain verification of information about the certificate subject. "Domain
Validation" (DV) certificates are by far the most common type. For Validation" (DV) certificates are by far the most common type. For
DV validation, the CA merely verifies that the requester has DV validation, the CA merely verifies that the requester has
effective control of the web server and/or DNS server for the domain, effective control of the web server and/or DNS server for the domain,
but does not explicitly attempt to verify their real-world identity. but does not explicitly attempt to verify their real-world identity.
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This document describes an extensible framework for automating the This document describes an extensible framework for automating the
issuance and domain validation procedure, thereby allowing servers issuance and domain validation procedure, thereby allowing servers
and infrastructural software to obtain certificates without user and infrastructural software to obtain certificates without user
interaction. Use of this protocol should radically simplify the interaction. Use of this protocol should radically simplify the
deployment of HTTPS and the practicality of PKIX authentication for deployment of HTTPS and the practicality of PKIX authentication for
other protocols based on TLS [RFC5246]. other protocols based on TLS [RFC5246].
2. Deployment Model and Operator Experience 2. Deployment Model and Operator Experience
The guiding use case for ACME is obtaining certificates for Web sites The guiding use case for ACME is obtaining certificates for websites
(HTTPS [RFC2818]). In this case, the user's web server is intended (HTTPS [RFC2818]). In this case, the user's web server is intended
to speak for one or more domains, and the process of certificate to speak for one or more domains, and the process of certificate
issuance is intended to verify that this server actually speaks for issuance is intended to verify that this web server actually speaks
the domain(s). for the domain(s).
DV certificate validation commonly checks claims about properties DV certificate validation commonly checks claims about properties
related to control of a domain name - properties that can be observed related to control of a domain name - properties that can be observed
by the issuing authority in an interactive process that can be by the certificate issuer in an interactive process that can be
conducted purely online. That means that under typical conducted purely online. That means that under typical
circumstances, all steps in the request, verification, and issuance circumstances, all steps in the request, verification, and issuance
process can be represented and performed by Internet protocols with process can be represented and performed by Internet protocols with
no out-of-band human intervention. no out-of-band human intervention.
At time of writing, when deploying an HTTPS server, an operator Prior to ACME, when deploying an HTTPS server, an operator typically
typically gets a prompt to generate a self-signed certificate. If gets a prompt to generate a self-signed certificate. If the operator
the operator were instead deploying an ACME-compatible web server, were instead deploying an ACME-compatible web server, the experience
the experience would be something like this: would be something like this:
o The ACME client prompts the operator for the intended domain o The ACME client prompts the operator for the intended domain
name(s) that the web server is to stand for. name(s) that the web server is to stand for.
o The ACME client presents the operator with a list of CAs from o The ACME client presents the operator with a list of CAs from
which it could get a certificate. (This list will change over which it could get a certificate. (This list will change over
time based on the capabilities of CAs and updates to ACME time based on the capabilities of CAs and updates to ACME
configuration.) The ACME client might prompt the operator for configuration.) The ACME client might prompt the operator for
payment information at this point. payment information at this point.
o The operator selects a CA. o The operator selects a CA.
o In the background, the ACME client contacts the CA and requests o In the background, the ACME client contacts the CA and requests
that a certificate be issued for the intended domain name(s). that it issue a certificate for the intended domain name(s).
o Once the CA is satisfied, the certificate is issued and the ACME o Once the CA is satisfied, the certificate is issued and the ACME
client automatically downloads and installs it, potentially client automatically downloads and installs it, potentially
notifying the operator via e-mail, SMS, etc. notifying the operator via e-mail, SMS, etc.
o The ACME client periodically contacts the CA to get updated o The ACME client periodically contacts the CA to get updated
certificates, stapled OCSP responses, or whatever else would be certificates, stapled OCSP responses, or whatever else would be
required to keep the server functional and its credentials up-to- required to keep the web server functional and its credentials up-
date. to-date.
In this way, it would be nearly as easy to deploy with a CA-issued In this way, it would be nearly as easy to deploy with a CA-issued
certificate as with a self-signed certificate. Furthermore, the certificate as with a self-signed certificate. Furthermore, the
maintenance of that CA-issued certificate would require minimal maintenance of that CA-issued certificate would require minimal
manual intervention. Such close integration of ACME with HTTPS manual intervention. Such close integration of ACME with HTTPS
servers would allow the immediate and automated deployment of servers would allow the immediate and automated deployment of
certificates as they are issued, sparing the human administrator from certificates as they are issued, sparing the human administrator from
much of the time-consuming work described in the previous section. much of the time-consuming work described in the previous section.
3. Terminology 3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
The two main roles in ACME are "client" and "server". The ACME The two main roles in ACME are "client" and "server". The ACME
client uses the protocol to request certificate management actions, client uses the protocol to request certificate management actions,
such as issuance or revocation. An ACME client therefore typically such as issuance or revocation. An ACME client therefore typically
runs on a web server, mail server, or some other server system which runs on a web server, mail server, or some other server system which
requires valid TLS certificates. The ACME server runs at a requires valid TLS certificates. The ACME server runs at a
certificate authority, and responds to client requests, performing certification authority, and responds to client requests, performing
the requested actions if the client is authorized. the requested actions if the client is authorized.
An ACME client is represented by an "account key pair". The client An ACME client is represented by an "account key pair". The client
uses the private key of this key pair to sign all messages sent to uses the private key of this key pair to sign all messages sent to
the server. The server uses the public key to verify the the server. The server uses the public key to verify the
authenticity and integrity of messages from the client. authenticity and integrity of messages from the client.
4. Protocol Overview 4. Protocol Overview
ACME allows a client to request certificate management actions using ACME allows a client to request certificate management actions using
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Revocation request Revocation request
Signature --------> Signature -------->
<-------- Result <-------- Result
Note that while ACME is defined with enough flexibility to handle Note that while ACME is defined with enough flexibility to handle
different types of identifiers in principle, the primary use case different types of identifiers in principle, the primary use case
addressed by this document is the case where domain names are used as addressed by this document is the case where domain names are used as
identifiers. For example, all of the identifier validation identifiers. For example, all of the identifier validation
challenges described in Section 7 below address validation of domain challenges described in Section 8 below address validation of domain
names. The use of ACME for other identifiers will require further names. The use of ACME for other identifiers will require further
specification, in order to describe how these identifiers are encoded specification, in order to describe how these identifiers are encoded
in the protocol, and what types of validation challenges the server in the protocol, and what types of validation challenges the server
might require. might require.
5. Message Transport 5. Character Encoding
All requests and responses sent via HTTP by ACME clients, ACME
servers, and validation servers as well as any inputs for digest
computations MUST be encoded using the UTF-8 [RFC3629] character set.
6. Message Transport
Communications between an ACME client and an ACME server are done Communications between an ACME client and an ACME server are done
over HTTPS, using JSON Web Signature (JWS) [RFC7515] to provide some over HTTPS, using JSON Web Signature (JWS) [RFC7515] to provide some
additional security properties for messages sent from the client to additional security properties for messages sent from the client to
the server. HTTPS provides server authentication and the server. HTTPS provides server authentication and
confidentiality. With some ACME-specific extensions, JWS provides confidentiality. With some ACME-specific extensions, JWS provides
authentication of the client's request payloads, anti-replay authentication of the client's request payloads, anti-replay
protection, and integrity for the HTTPS request URI. protection, and integrity for the HTTPS request URI.
5.1. HTTPS Requests 6.1. HTTPS Requests
Each ACME function is accomplished by the client sending a sequence Each ACME function is accomplished by the client sending a sequence
of HTTPS requests to the server, carrying JSON messages of HTTPS requests to the server, carrying JSON messages
[RFC2818][RFC7159]. Use of HTTPS is REQUIRED. Clients SHOULD [RFC2818][RFC7159]. Use of HTTPS is REQUIRED. Each subsection of
support HTTP public key pinning [RFC7469], and servers SHOULD emit Section 7 below describes the message formats used by the function
pinning headers. Each subsection of Section 6 below describes the and the order in which messages are sent.
message formats used by the function, and the order in which messages
are sent.
In most HTTPS transactions used by ACME, the ACME client is the HTTPS In most HTTPS transactions used by ACME, the ACME client is the HTTPS
client and the ACME server is the HTTPS server. The ACME server acts client and the ACME server is the HTTPS server. The ACME server acts
as an HTTP and HTTPS client when validating challenges via HTTP. as an HTTP and HTTPS client when validating challenges via HTTP.
ACME clients SHOULD send a User-Agent header in accordance with ACME clients SHOULD send a User-Agent header in accordance with
[RFC7231], including the name and version of the ACME software in [RFC7231], including the name and version of the ACME software in
addition to the name and version of the underlying HTTP client addition to the name and version of the underlying HTTP client
software. software.
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Cross-Origin Resource Sharing (CORS) in order to be accessible from Cross-Origin Resource Sharing (CORS) in order to be accessible from
browser-based clients [W3C.CR-cors-20130129]. Such servers SHOULD browser-based clients [W3C.CR-cors-20130129]. Such servers SHOULD
set the Access-Control-Allow-Origin header field to the value "*". set the Access-Control-Allow-Origin header field to the value "*".
Binary fields in the JSON objects used by ACME are encoded using Binary fields in the JSON objects used by ACME are encoded using
base64url encoding described in [RFC4648] Section 5, according to the base64url encoding described in [RFC4648] Section 5, according to the
profile specified in JSON Web Signature [RFC7515] Section 2. This profile specified in JSON Web Signature [RFC7515] Section 2. This
encoding uses a URL safe character set. Trailing '=' characters MUST encoding uses a URL safe character set. Trailing '=' characters MUST
be stripped. be stripped.
5.2. Request Authentication 6.2. Request Authentication
All ACME requests with a non-empty body MUST encapsulate their All ACME requests with a non-empty body MUST encapsulate their
payload in a JWS object, signed (in most cases) using the account's payload in a JSON Web Signature (JWS) [RFC7515] object, signed using
private key. The server MUST verify the JWS before processing the the account's private key unless otherwise specified. The server
request. Encapsulating request bodies in JWS provides a simple MUST verify the JWS before processing the request. Encapsulating
authentication of requests. request bodies in JWS provides authentication of requests.
JWS objects sent in ACME requests MUST meet the following additional JWS objects sent in ACME requests MUST meet the following additional
criteria: criteria:
o The JWS MUST be encoded using UTF-8
o The JWS MUST NOT have the value "none" in its "alg" field o The JWS MUST NOT have the value "none" in its "alg" field
o The JWS MUST NOT have a MAC-based algorithm in its "alg" field o The JWS MUST NOT have a MAC-based algorithm in its "alg" field
o The JWS Protected Header MUST include the following fields: o The JWS Protected Header MUST include the following fields:
* "alg" * "alg"
* "jwk" (only for requests to new-reg and revoke-cert resources)
* "jwk" (only for requests to new-account and revoke-cert
resources)
* "kid" (for all other requests). * "kid" (for all other requests).
* "nonce" (defined below) * "nonce" (defined below)
* "url" (defined below) * "url" (defined below)
The "jwk" and "kid" fields are mutually exclusive. Servers MUST The "jwk" and "kid" fields are mutually exclusive. Servers MUST
reject requests that contain both. reject requests that contain both.
For new-reg requests, and for revoke-cert requests authenticated by For new-account requests, and for revoke-cert requests authenticated
certificate key, there MUST be a "jwk" field. by certificate key, there MUST be a "jwk" field.
For all other requests, there MUST be a "kid" field. This field must For all other requests, there MUST be a "kid" field. This field must
contain the account URI received by POSTing to the new-reg resource. contain the account URI received by POSTing to the new-account
resource.
Note that authentication via signed JWS request bodies implies that Note that authentication via signed JWS request bodies implies that
GET requests are not authenticated. Servers MUST NOT respond to GET GET requests are not authenticated. Servers MUST NOT respond to GET
requests for resources that might be considered sensitive. requests for resources that might be considered sensitive. Account
resources are the only sensitive resources defined in this
specification.
If the client sends a JWS signed with an algorithm that the server If the client sends a JWS signed with an algorithm that the server
does not support, then the server MUST return an error with status does not support, then the server MUST return an error with status
code 400 (Bad Request) and type code 400 (Bad Request) and type
"urn:ietf:params:acme:error:badSignatureAlgorithm". The problem "urn:ietf:params:acme:error:badSignatureAlgorithm". The problem
document returned with the error MUST include an "algorithms" field document returned with the error MUST include an "algorithms" field
with an array of supported "alg" values. with an array of supported "alg" values.
HTTP/1.1 400 Bad Request
Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw
Content-Type: application/problem+json
Content-Language: en
{
"type": "urn:ietf:params:acme:error:badSignatureAlgorithm",
"detail": "Algorithm 'ES384' is not supported",
"algorithms": ["RS256", "RS384", "ES256"]
}
In the examples below, JWS objects are shown in the JSON or flattened In the examples below, JWS objects are shown in the JSON or flattened
JSON serialization, with the protected header and payload expressed JSON serialization, with the protected header and payload expressed
as base64url(content) instead of the actual base64-encoded value, so as base64url(content) instead of the actual base64-encoded value, so
that the content is readable. Some fields are omitted for brevity, that the content is readable.
marked with "...".
5.3. Equivalence of JWKs
At some points in the protocol, it is necessary for the server to
determine whether two JSON Web Key (JWK) [RFC7517] objects represent
the same key. In performing these checks, the server MUST consider
two JWKs to match if and only if they have the identical values in
all fields included in the computation of a JWK thumbprint for that
key. That is, the keys must have the same "kty" value and contain
identical values in the fields used in the computation of a JWK
thumbprint for that key type:
o "RSA": "n", "e"
o "EC": "crv", "x", "y"
Note that this comparison is equivalent to computing the JWK
thumbprints of the two keys and comparing thumbprints. The only
difference is that there is no requirement for a hash computation
(and thus it is independent of the choice of hash function) and no
risk of hash collision.
5.4. Request URI Integrity 6.3. Request URI Integrity
It is common in deployment for the entity terminating TLS for HTTPS It is common in deployment for the entity terminating TLS for HTTPS
to be different from the entity operating the logical HTTPS server, to be different from the entity operating the logical HTTPS server,
with a "request routing" layer in the middle. For example, an ACME with a "request routing" layer in the middle. For example, an ACME
CA might have a content delivery network terminate TLS connections CA might have a content delivery network terminate TLS connections
from clients so that it can inspect client requests for denial-of- from clients so that it can inspect client requests for denial-of-
service protection. service protection.
These intermediaries can also change values in the request that are These intermediaries can also change values in the request that are
not signed in the HTTPS request, e.g., the request URI and headers. not signed in the HTTPS request, e.g., the request URI and headers.
skipping to change at page 12, line 7 skipping to change at page 11, line 26
Except for the directory resource, all ACME resources are addressed Except for the directory resource, all ACME resources are addressed
with URLs provided to the client by the server. For these resources, with URLs provided to the client by the server. For these resources,
the client MUST set the "url" field to the exact string provided by the client MUST set the "url" field to the exact string provided by
the server (rather than performing any re-encoding on the URL). The the server (rather than performing any re-encoding on the URL). The
server SHOULD perform the corresponding string equality check, server SHOULD perform the corresponding string equality check,
configuring each resource with the URL string provided to clients and configuring each resource with the URL string provided to clients and
having the resource check that requests have the same string in their having the resource check that requests have the same string in their
"url" fields. "url" fields.
5.4.1. "url" (URL) JWS header parameter 6.3.1. "url" (URL) JWS header parameter
The "url" header parameter specifies the URL [RFC3986] to which this The "url" header parameter specifies the URL [RFC3986] to which this
JWS object is directed. The "url" parameter MUST be carried in the JWS object is directed. The "url" parameter MUST be carried in the
protected header of the JWS. The value of the "url" header MUST be a protected header of the JWS. The value of the "url" header MUST be a
JSON string representing the URL. string representing the URL.
5.5. Replay protection 6.4. Replay protection
In order to protect ACME resources from any possible replay attacks, In order to protect ACME resources from any possible replay attacks,
ACME requests have a mandatory anti-replay mechanism. This mechanism ACME requests have a mandatory anti-replay mechanism. This mechanism
is based on the server maintaining a list of nonces that it has is based on the server maintaining a list of nonces that it has
issued to clients, and requiring any signed request from the client issued to clients, and requiring any signed request from the client
to carry such a nonce. to carry such a nonce.
An ACME server provides nonces to clients using the Replay-Nonce An ACME server provides nonces to clients using the Replay-Nonce
header field, as specified below. The server MUST include a Replay- header field, as specified below. The server MUST include a Replay-
Nonce header field in every successful response to a POST request, Nonce header field in every successful response to a POST request and
and SHOULD provide it in error responses as well. SHOULD provide it in error responses as well.
Every JWS sent by an ACME client MUST include, in its protected Every JWS sent by an ACME client MUST include, in its protected
header, the "nonce" header parameter, with contents as defined below. header, the "nonce" header parameter, with contents as defined below.
As part of JWS verification, the ACME server MUST verify that the As part of JWS verification, the ACME server MUST verify that the
value of the "nonce" header is a value that the server previously value of the "nonce" header is a value that the server previously
provided in a Replay-Nonce header field. Once a nonce value has provided in a Replay-Nonce header field. Once a nonce value has
appeared in an ACME request, the server MUST consider it invalid, in appeared in an ACME request, the server MUST consider it invalid, in
the same way as a value it had never issued. the same way as a value it had never issued.
When a server rejects a request because its nonce value was When a server rejects a request because its nonce value was
unacceptable (or not present), it MUST provide HTTP status code 400 unacceptable (or not present), it MUST provide HTTP status code 400
(Bad Request), and indicate the ACME error code (Bad Request), and indicate the ACME error type
"urn:ietf:params:acme:error:badNonce". An error response with the "urn:ietf:params:acme:error:badNonce". An error response with the
"badNonce" error code MUST include a Replay-Nonce header with a fresh "badNonce" error type MUST include a Replay-Nonce header with a fresh
nonce. On receiving such a response, a client SHOULD retry the nonce. On receiving such a response, a client SHOULD retry the
request using the new nonce. request using the new nonce.
The precise method used to generate and track nonces is up to the The precise method used to generate and track nonces is up to the
server. For example, the server could generate a random 128-bit server. For example, the server could generate a random 128-bit
value for each response, keep a list of issued nonces, and strike value for each response, keep a list of issued nonces, and strike
nonces from this list as they are used. nonces from this list as they are used.
5.5.1. Replay-Nonce 6.4.1. Replay-Nonce
The "Replay-Nonce" header field includes a server-generated value The "Replay-Nonce" header field includes a server-generated value
that the server can use to detect unauthorized replay in future that the server can use to detect unauthorized replay in future
client requests. The server should generate the value provided in client requests. The server should generate the value provided in
Replay-Nonce in such a way that they are unique to each message, with Replay-Nonce in such a way that they are unique to each message, with
high probability. high probability.
The value of the Replay-Nonce field MUST be an octet string encoded The value of the Replay-Nonce field MUST be an octet string encoded
according to the base64url encoding described in Section 2 of according to the base64url encoding described in Section 2 of
[RFC7515]. Clients MUST ignore invalid Replay-Nonce values. [RFC7515]. Clients MUST ignore invalid Replay-Nonce values.
base64url = [A-Z] / [a-z] / [0-9] / "-" / "_" base64url = [A-Z] / [a-z] / [0-9] / "-" / "_"
Replay-Nonce = *base64url Replay-Nonce = *base64url
The Replay-Nonce header field SHOULD NOT be included in HTTP request The Replay-Nonce header field SHOULD NOT be included in HTTP request
messages. messages.
5.5.2. "nonce" (Nonce) JWS header parameter 6.4.2. "nonce" (Nonce) JWS header parameter
The "nonce" header parameter provides a unique value that enables the The "nonce" header parameter provides a unique value that enables the
verifier of a JWS to recognize when replay has occurred. The "nonce" verifier of a JWS to recognize when replay has occurred. The "nonce"
header parameter MUST be carried in the protected header of the JWS. header parameter MUST be carried in the protected header of the JWS.
The value of the "nonce" header parameter MUST be an octet string, The value of the "nonce" header parameter MUST be an octet string,
encoded according to the base64url encoding described in Section 2 of encoded according to the base64url encoding described in Section 2 of
[RFC7515]. If the value of a "nonce" header parameter is not valid [RFC7515]. If the value of a "nonce" header parameter is not valid
according to this encoding, then the verifier MUST reject the JWS as according to this encoding, then the verifier MUST reject the JWS as
malformed. malformed.
5.6. Rate limits 6.5. Rate limits
Creation of resources can be rate limited to ensure fair usage and Creation of resources can be rate limited to ensure fair usage and
prevent abuse. Once the rate limit is exceeded, the server MUST prevent abuse. Once the rate limit is exceeded, the server MUST
respond with an error with the type respond with an error with the type
"urn:ietf:params:acme:error:rateLimited". Additionally, the server "urn:ietf:params:acme:error:rateLimited". Additionally, the server
SHOULD send a "Retry-After" header indicating when the current SHOULD send a "Retry-After" header indicating when the current
request may succeed again. If multiple rate limits are in place, request may succeed again. If multiple rate limits are in place,
that is the time where all rate limits allow access again for the that is the time where all rate limits allow access again for the
current request with exactly the same parameters. current request with exactly the same parameters.
In addition to the human readable "detail" field of the error In addition to the human readable "detail" field of the error
response, the server MAY send one or multiple tokens in the "Link" response, the server MAY send one or multiple tokens in the "Link"
header pointing to documentation about the specific hit rate limits header pointing to documentation about the specific hit rate limits
using the "rate-limit" relation. using the "urn:ietf:params:acme:documentation" relation.
5.7. Errors 6.6. Errors
Errors can be reported in ACME both at the HTTP layer and within ACME Errors can be reported in ACME both at the HTTP layer and within
payloads. ACME servers can return responses with an HTTP error challenge objects as defined in {{identifier-validation-challenges}.
response code (4XX or 5XX). For example: If the client submits a ACME servers can return responses with an HTTP error response code
request using a method not allowed in this document, then the server (4XX or 5XX). For example: If the client submits a request using a
MAY return status code 405 (Method Not Allowed). method not allowed in this document, then the server MAY return
status code 405 (Method Not Allowed).
When the server responds with an error status, it SHOULD provide When the server responds with an error status, it SHOULD provide
additional information using problem document [RFC7807]. To additional information using a problem document [RFC7807]. To
facilitate automatic response to errors, this document defines the facilitate automatic response to errors, this document defines the
following standard tokens for use in the "type" field (within the following standard tokens for use in the "type" field (within the
"urn:ietf:params:acme:error:" namespace): "urn:ietf:params:acme:error:" namespace):
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
| Code | Description | | Type | Description |
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
| badCSR | The CSR is unacceptable (e.g., due to a | | badCSR | The CSR is unacceptable (e.g., due to a |
| | short key) | | | short key) |
| | | | | |
| badNonce | The client sent an unacceptable anti- | | badNonce | The client sent an unacceptable anti- |
| | replay nonce | | | replay nonce |
| | | | | |
| badSignatureAlgorithm | The JWS was signed with an algorithm the | | badSignatureAlgorithm | The JWS was signed with an algorithm the |
| | server does not support | | | server does not support |
| | | | | |
| caa | CAA records forbid the CA from issuing | | invalidContact | The contact URI for an account was |
| | |
| connection | The server could not connect to |
| | validation target |
| | |
| dnssec | DNSSEC validation failed |
| | |
| invalidContact | The contact URI for a registration was |
| | invalid | | | invalid |
| | | | | |
| malformed | The request message was malformed | | malformed | The request message was malformed |
| | | | | |
| rateLimited | The request exceeds a rate limit | | rateLimited | The request exceeds a rate limit |
| | | | | |
| rejectedIdentifier | The server will not issue for the | | rejectedIdentifier | The server will not issue for the |
| | identifier | | | identifier |
| | | | | |
| serverInternal | The server experienced an internal error | | serverInternal | The server experienced an internal error |
| | | | | |
| tls | The server received a TLS error during |
| | validation |
| | |
| unauthorized | The client lacks sufficient authorization | | unauthorized | The client lacks sufficient authorization |
| | | | | |
| unknownHost | The server could not resolve a domain |
| | name |
| | |
| unsupportedIdentifier | Identifier is not supported, but may be | | unsupportedIdentifier | Identifier is not supported, but may be |
| | in future | | | in future |
| | | | | |
| userActionRequired | The user visit the "instance" URL and | | userActionRequired | Visit the "instance" URL and take actions |
| | take actions specified there | | | specified there |
| | |
| badRevocationReason | The revocation reason provided is not |
| | allowed by the server |
| | |
| caa | CAA records forbid the CA from issuing |
| | |
| dns | There was a problem with a DNS query |
| | |
| connection | The server could not connect to |
| | validation target |
| | |
| tls | The server received a TLS error during |
| | validation |
| | |
| incorrectResponse | Response received didn't match the |
| | challenge's requirements |
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
This list is not exhaustive. The server MAY return errors whose This list is not exhaustive. The server MAY return errors whose
"type" field is set to a URI other than those defined above. Servers "type" field is set to a URI other than those defined above. Servers
MUST NOT use the ACME URN namespace for errors other than the MUST NOT use the ACME URN namespace for errors other than the
standard types. Clients SHOULD display the "detail" field of all standard types. Clients SHOULD display the "detail" field of all
errors. errors.
Authorization and challenge objects can also contain error 7. Certificate Management
information to indicate why the server was unable to validate
authorization.
6. Certificate Management
In this section, we describe the certificate management functions In this section, we describe the certificate management functions
that ACME enables: that ACME enables:
o Account Creation o Account Creation
o Ordering a Certificate o Ordering a Certificate
o Identifier Authorization o Identifier Authorization
o Certificate Issuance o Certificate Issuance
o Certificate Revocation o Certificate Revocation
6.1. Resources 7.1. Resources
ACME is structured as a REST application with a few types of ACME is structured as a REST application with a few types of
resources: resources:
o Account resources, representing information about an account o Account resources, representing information about an account
(Section 7.1.2, Section 7.3)
o Order resources, representing an account's requests to issue o Order resources, representing an account's requests to issue
certificates certificates (Section 7.1.3)
o Authorization resources, representing an account's authorization o Authorization resources, representing an account's authorization
to act for an identifier to act for an identifier (Section 7.1.4)
o Challenge resources, representing a challenge to prove control of o Challenge resources, representing a challenge to prove control of
an identifier an identifier (Section 7.5, Section 8)
o Certificate resources, representing issued certificates o Certificate resources, representing issued certificates
(Section 7.4.2)
o A "directory" resource o A "directory" resource (Section 7.1.1)
o A "new-nonce" resource o A "new-nonce" resource (Section 7.2)
o A "new-account" resource o A "new-account" resource (Section 7.3)
o A "new-order" resource o A "new-order" resource (Section 7.4)
o A "revoke-certificate" resource o A "revoke-certificate" resource (Section 7.6)
o A "key-change" resource o A "key-change" resource (Section 7.3.3)
The server MUST provide "directory" and "new-nonce" resources. The server MUST provide "directory" and "new-nonce" resources.
ACME uses different URIs for different management functions. Each ACME uses different URIs for different management functions. Each
function is listed in a directory along with its corresponding URI, function is listed in a directory along with its corresponding URI,
so clients only need to be configured with the directory URI. These so clients only need to be configured with the directory URI. These
URIs are connected by a few different link relations [RFC5988]. URIs are connected by a few different link relations [RFC5988].
The "up" link relation is used with challenge resources to indicate The "up" link relation is used with challenge resources to indicate
the authorization resource to which a challenge belongs. It is also the authorization resource to which a challenge belongs. It is also
used from certificate resources to indicate a resource from which the used from certificate resources to indicate a resource from which the
client may fetch a chain of CA certificates that could be used to client may fetch a chain of CA certificates that could be used to
validate the certificate in the original resource. validate the certificate in the original resource.
The "directory" link relation is present on all resources other than The "index" link relation is present on all resources other than the
the directory and indicates the directory URL. directory and indicates the URL of the directory.
The following diagram illustrates the relations between resources on The following diagram illustrates the relations between resources on
an ACME server. For the most part, these relations are expressed by an ACME server. For the most part, these relations are expressed by
URLs provided as strings in the resources' JSON representations. URLs provided as strings in the resources' JSON representations.
Lines with labels in quotes indicate HTTP link relations Lines with labels in quotes indicate HTTP link relations.
directory directory
| |
|--> new-nonce |--> new-nonce
| |
--------------------------------------------------+ ----------------------------------+
| | | | | | | |
| | | | | | | |
V V V V V V V V
new-account new-authz new-order revoke-cert new-account new-authz new-order revoke-cert
| | | ^ | | |
| | | "author" | "revoke" | | |
V | V <-------- | V | V
acct | order --------> cert ---------+ acct | order --------> cert
| | ^ | | | ^ |
| | | "up" | "up" | | | "up" | "up"
| V | V | V | V
+------> authz cert-chain +------> authz cert-chain
| ^ | ^
| | "up" | | "up"
V | V |
challenge challenge
The following table illustrates a typical sequence of requests The following table illustrates a typical sequence of requests
skipping to change at page 18, line 32 skipping to change at page 17, line 32
| Respond to challenge | POST challenge | 200 | | Respond to challenge | POST challenge | 200 |
| | | | | | | |
| Poll for status | GET authz | 200 | | Poll for status | GET authz | 200 |
| | | | | | | |
| Check for new cert | GET cert | 200 | | Check for new cert | GET cert | 200 |
+----------------------+------------------+----------------+ +----------------------+------------------+----------------+
The remainder of this section provides the details of how these The remainder of this section provides the details of how these
resources are structured and how the ACME protocol makes use of them. resources are structured and how the ACME protocol makes use of them.
6.1.1. Directory 7.1.1. Directory
In order to help clients configure themselves with the right URIs for In order to help clients configure themselves with the right URIs for
each ACME operation, ACME servers provide a directory object. This each ACME operation, ACME servers provide a directory object. This
should be the only URL needed to configure clients. It is a JSON should be the only URL needed to configure clients. It is a JSON
dictionary, whose keys are drawn from the following table and whose object, whose keys are drawn from the following table and whose
values are the corresponding URLs. values are the corresponding URLs.
+-------------+--------------------+ +-------------+--------------------+
| Key | URL in value | | Key | URL in value |
+-------------+--------------------+ +-------------+--------------------+
| new-nonce | New nonce | | new-nonce | New nonce |
| | | | | |
| new-account | New account | | new-account | New account |
| | | | | |
| new-order | New order | | new-order | New order |
skipping to change at page 19, line 25 skipping to change at page 18, line 25
| | | | | |
| revoke-cert | Revoke certificate | | revoke-cert | Revoke certificate |
| | | | | |
| key-change | Key change | | key-change | Key change |
+-------------+--------------------+ +-------------+--------------------+
There is no constraint on the actual URI of the directory except that There is no constraint on the actual URI of the directory except that
it should be different from the other ACME server resources' URIs, it should be different from the other ACME server resources' URIs,
and that it should not clash with other services. For instance: and that it should not clash with other services. For instance:
o a host which function as both an ACME and Web server may want to o a host which functions as both an ACME and a Web server may want
keep the root path "/" for an HTML "front page", and and place the to keep the root path "/" for an HTML "front page", and place the
ACME directory under path "/acme". ACME directory under the path "/acme".
o a host which only functions as an ACME server could place the o a host which only functions as an ACME server could place the
directory under path "/". directory under the path "/".
The dictionary MAY additionally contain a key "meta". If present, it The object MAY additionally contain a key "meta". If present, it
MUST be a JSON dictionary; each item in the dictionary is an item of MUST be a JSON object; each field in the object is an item of
metadata relating to the service provided by the ACME server. metadata relating to the service provided by the ACME server.
The following metadata items are defined, all of which are OPTIONAL: The following metadata items are defined, all of which are OPTIONAL:
"terms-of-service" (optional, string): A URI identifying the current "terms-of-service" (optional, string): A URI identifying the current
terms of service. terms of service.
"website" (optional, string): An HTTP or HTTPS URL locating a "website" (optional, string): An HTTP or HTTPS URL locating a
website providing more information about the ACME server. website providing more information about the ACME server.
"caa-identities" (optional, array of string): Each string MUST be a "caa-identities" (optional, array of string): Each string MUST be a
lowercase hostname which the ACME server recognises as referring lowercase hostname which the ACME server recognizes as referring
to itself for the purposes of CAA record validation as defined in to itself for the purposes of CAA record validation as defined in
[RFC6844]. This allows clients to determine the correct issuer [RFC6844]. This allows clients to determine the correct issuer
domain name to use when configuring CAA record. domain name to use when configuring CAA records.
Clients access the directory by sending a GET request to the Clients access the directory by sending a GET request to the
directory URI. directory URI.
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
{ {
"new-nonce": "https://example.com/acme/new-nonce", "new-nonce": "https://example.com/acme/new-nonce",
"new-account": "https://example.com/acme/new-account", "new-account": "https://example.com/acme/new-account",
skipping to change at page 20, line 22 skipping to change at page 19, line 22
"new-authz": "https://example.com/acme/new-authz", "new-authz": "https://example.com/acme/new-authz",
"revoke-cert": "https://example.com/acme/revoke-cert", "revoke-cert": "https://example.com/acme/revoke-cert",
"key-change": "https://example.com/acme/key-change", "key-change": "https://example.com/acme/key-change",
"meta": { "meta": {
"terms-of-service": "https://example.com/acme/terms", "terms-of-service": "https://example.com/acme/terms",
"website": "https://www.example.com/", "website": "https://www.example.com/",
"caa-identities": ["example.com"] "caa-identities": ["example.com"]
} }
} }
6.1.2. Account Objects 7.1.2. Account Objects
An ACME account resource represents a set of metadata associated to An ACME account resource represents a set of metadata associated with
an account. Account resources have the following structure: an account. Account resources have the following structure:
key (required, dictionary): The public key of the account's key
pair, encoded as a JSON Web Key object [RFC7517]. The client may
not directly update this field, but must use the key-change
resource instead.
status (required, string): The status of this account. Possible status (required, string): The status of this account. Possible
values are: "valid", "deactivated", and "revoked". The value values are: "valid", "deactivated", and "revoked". The value
"deactivated" should be used to indicate user initiated "deactivated" should be used to indicate user initiated
deactivation whereas "revoked" should be used to indicate deactivation whereas "revoked" should be used to indicate
administratively initiated deactivation. administratively initiated deactivation.
contact (optional, array of string): An array of URIs that the contact (optional, array of string): An array of URIs that the
server can use to contact the client for issues related to this server can use to contact the client for issues related to this
account. For example, the server may wish to notify the client account. For example, the server may wish to notify the client
about server-initiated revocation or certificate expiration. about server-initiated revocation or certificate expiration.
terms-of-service-agreed (optional, boolean): Including this field in terms-of-service-agreed (optional, boolean): Including this field in
a new-account request, with a value of true, indicates the a new-account request, with a value of true, indicates the
client's agreement with the terms of service. This field is not client's agreement with the terms of service. This field is not
updateable by the client. updateable by the client.
orders (required, string): A URI from which a list of orders orders (required, string): A URI from which a list of orders
submitted by this account can be fetched via a GET request, as submitted by this account can be fetched via a GET request, as
described in Section 6.1.2.1 described in Section 7.1.2.1.
{ {
"contact": [ "contact": [
"mailto:cert-admin@example.com", "mailto:cert-admin@example.com",
"tel:+12025551212" "tel:+12025551212"
], ],
"terms-of-service-agreed": true, "terms-of-service-agreed": true,
"orders": "https://example.com/acme/acct/1/orders" "orders": "https://example.com/acme/acct/1/orders"
} }
6.1.2.1. Orders List 7.1.2.1. Orders List
Each account object includes an "orders" URI from which a list of Each account object includes an "orders" URI from which a list of
orders created by the account can be fetched via GET request. The orders created by the account can be fetched via GET request. The
result of the GET request MUST be a JSON object whose "orders" field result of the GET request MUST be a JSON object whose "orders" field
is an array of URIs, each identifying an order belonging to the is an array of URIs, each identifying an order belonging to the
account. The server SHOULD include pending orders, and SHOULD NOT account. The server SHOULD include pending orders, and SHOULD NOT
include orders that are invalid in the array of URIs. The server MAY include orders that are invalid in the array of URIs. The server MAY
return an incomplete list, along with a Link header with link return an incomplete list, along with a Link header with a "next"
relation "next" indicating a URL to retrieve further entries. link relation indicating where further entries can be acquired.
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Link: href="/acme/acct/1/orders?cursor=2", rel="next" Link: href="/acme/acct/1/orders?cursor=2", rel="next"
{ {
"orders": [ "orders": [
"https://example.com/acme/acct/1/order/1", "https://example.com/acme/acct/1/order/1",
"https://example.com/acme/acct/1/order/2", "https://example.com/acme/acct/1/order/2",
/* 47 more URLs not shown for example brevity */ /* 47 more URLs not shown for example brevity */
"https://example.com/acme/acct/1/order/50" "https://example.com/acme/acct/1/order/50"
] ]
} }
6.1.3. Order Objects 7.1.3. Order Objects
An ACME order object represents a client's request for a certificate, An ACME order object represents a client's request for a certificate
and is used to track the progress of that order through to issuance. and is used to track the progress of that order through to issuance.
Thus, the object contains information about the requested Thus, the object contains information about the requested
certificate, the authorizations that the server requires the client certificate, the authorizations that the server requires the client
to complete, and any certificates that have resulted from this order. to complete, and any certificates that have resulted from this order.
status (required, string): The status of this order. Possible status (required, string): The status of this order. Possible
values are: "pending", "processing", "valid", and "invalid". values are: "pending", "processing", "valid", and "invalid".
expires (optional, string): The timestamp after which the server expires (optional, string): The timestamp after which the server
will consider this order invalid, encoded in the format specified will consider this order invalid, encoded in the format specified
in RFC 3339 [RFC3339]. This field is REQUIRED for objects with in RFC 3339 [RFC3339]. This field is REQUIRED for objects with
"pending" or "valid" in the status field. "pending" or "valid" in the status field.
csr (required, string): A CSR encoding the parameters for the csr (required, string): A CSR encoding the parameters for the
certificate being requested [RFC2986]. The CSR is sent in the certificate being requested [RFC2986]. The CSR is sent in the
base64url-encoded version of the DER format. (Note: Because this base64url-encoded version of the DER format. (Note: Because this
field uses base64url, and does not include headers, it is field uses base64url, and does not include headers, it is
different from PEM.) different from PEM.)
notBefore (optional, string): The requested value of the notBefore notBefore (optional, string): The requested value of the notBefore
field in the certificate, in the date format defined in [RFC3339] field in the certificate, in the date format defined in [RFC3339].
notAfter (optional, string): The requested value of the notAfter notAfter (optional, string): The requested value of the notAfter
field in the certificate, in the date format defined in [RFC3339] field in the certificate, in the date format defined in [RFC3339].
error (optional, object): The error that occurred while processing
the order, if any. This field is structured as a problem document
[RFC7807].
authorizations (required, array of string): For pending orders, the authorizations (required, array of string): For pending orders, the
authorizations that the client needs to complete before the authorizations that the client needs to complete before the
requested certificate can be issued (see Section 6.5). For final requested certificate can be issued (see Section 7.5). For final
orders, the authorizations that were completed. Each entry is a orders, the authorizations that were completed. Each entry is a
URL from which an authorization can be fetched with a GET request. URL from which an authorization can be fetched with a GET request.
certificate (optional, string): A URL for the certificate that has certificate (optional, string): A URL for the certificate that has
been issued in response to this order. been issued in response to this order.
{ {
"status": "pending", "status": "pending",
"expires": "2015-03-01T14:09:00Z", "expires": "2015-03-01T14:09:00Z",
skipping to change at page 23, line 4 skipping to change at page 22, line 9
The elements of the "authorizations" array are immutable once set. The elements of the "authorizations" array are immutable once set.
The server MUST NOT change the contents of the "authorizations" array The server MUST NOT change the contents of the "authorizations" array
after it is created. If a client observes a change in the contents after it is created. If a client observes a change in the contents
of the "authorizations" array, then it SHOULD consider the order of the "authorizations" array, then it SHOULD consider the order
invalid. invalid.
The "authorizations" array in the challenge SHOULD reflect all The "authorizations" array in the challenge SHOULD reflect all
authorizations that the CA takes into account in deciding to issue, authorizations that the CA takes into account in deciding to issue,
even if some authorizations were fulfilled in earlier orders or in even if some authorizations were fulfilled in earlier orders or in
pre-authorization transactions. For example, if a CA allows multiple pre-authorization transactions. For example, if a CA allows multiple
orders to be fufilled based on a single authorization transaction, orders to be fulfilled based on a single authorization transaction,
then it SHOULD reflect that authorization in all of the order. then it SHOULD reflect that authorization in all of the order.
6.1.4. Authorization Objects 7.1.4. Authorization Objects
An ACME authorization object represents a server's authorization for An ACME authorization object represents a server's authorization for
an account to represent an identifier. In addition to the an account to represent an identifier. In addition to the
identifier, an authorization includes several metadata fields, such identifier, an authorization includes several metadata fields, such
as the status of the authorization (e.g., "pending", "valid", or as the status of the authorization (e.g., "pending", "valid", or
"revoked") and which challenges were used to validate possession of "revoked") and which challenges were used to validate possession of
the identifier. the identifier.
The structure of an ACME authorization resource is as follows: The structure of an ACME authorization resource is as follows:
identifier (required, dictionary of string): The identifier that the identifier (required, object): The identifier that the account is
account is authorized to represent authorized to represent
type (required, string): The type of identifier. type (required, string): The type of identifier.
value (required, string): The identifier itself. value (required, string): The identifier itself.
status (required, string): The status of this authorization. status (required, string): The status of this authorization.
Possible values are: "pending", "processing", "valid", "invalid" Possible values are: "pending", "processing", "valid", "invalid"
and "revoked". If this field is missing, then the default value and "revoked".
is "pending".
expires (optional, string): The timestamp after which the server expires (optional, string): The timestamp after which the server
will consider this authorization invalid, encoded in the format will consider this authorization invalid, encoded in the format
specified in RFC 3339 [RFC3339]. This field is REQUIRED for specified in RFC 3339 [RFC3339]. This field is REQUIRED for
objects with "valid" in the "status" field. objects with "valid" in the "status" field.
scope (optional, string): If this field is present, then it MUST scope (optional, string): If this field is present, then it MUST
contain a URI for an order resource, such that this authorization contain a URI for an order resource, such that this authorization
is only valid for that resource. If this field is absent, then is only valid for that resource. If this field is absent, then
the CA MUST consider this authorization valid for all orders until the CA MUST consider this authorization valid for all orders until
the authorization expires. [[ Open issue: More flexible scoping? the authorization expires.
]]
challenges (required, array): The challenges that the client can challenges (required, array of objects): The challenges that the
fulfill in order to prove possession of the identifier (for client can fulfill in order to prove possession of the identifier
pending authorizations). For final authorizations, the challenges (for pending authorizations). For final authorizations, the
that were used. Each array entry is a dictionary with parameters challenges that were used. Each array entry is an object with
required to validate the challenge, as specified in Section 7. A parameters required to validate the challenge. A client should
client should attempt to fulfill at most one of these challenges, attempt to fulfill one of these challenges, and a server should
and a server should consider any one of the challenges sufficient consider any one of the challenges sufficient to make the
to make the authorization valid. authorization valid. For final authorizations it contains the
challenges that were completed.
The only type of identifier defined by this specification is a fully- The only type of identifier defined by this specification is a fully-
qualified domain name (type: "dns"). The value of the identifier qualified domain name (type: "dns"). If a domain name contains non-
MUST be the ASCII representation of the domain name. If a domain ASCII Unicode characters it MUST be encoded using the rules defined
name contains Unicode characters it MUST be encoded using the rules in [RFC3492]. Servers MUST verify any identifier values that begin
defined in [RFC3492]. Servers MUST verify any identifier values that with the ASCII Compatible Encoding prefix "xn-" as defined in
begin with the ASCII Compatible Encoding prefix "xn-" as defined in
[RFC5890] are properly encoded. Wildcard domain names (with "*" as [RFC5890] are properly encoded. Wildcard domain names (with "*" as
the first label) MUST NOT be included in authorization objects. the first label) MUST NOT be included in authorization objects.
Section 8 describes a set of challenges for domain name validation.
{ {
"status": "valid", "status": "valid",
"expires": "2015-03-01T14:09:00Z", "expires": "2015-03-01T14:09:00Z",
"identifier": { "identifier": {
"type": "dns", "type": "dns",
"value": "example.org" "value": "example.org"
}, },
"challenges": [ "challenges": [
{ {
"type": "http-01", "type": "http-01",
"status": "valid", "status": "valid",
"validated": "2014-12-01T12:05:00Z", "validated": "2014-12-01T12:05:00Z",
"keyAuthorization": "SXQe-2XODaDxNR...vb29HhjjLPSggwiE" "keyAuthorization": "SXQe-2XODaDxNR...vb29HhjjLPSggwiE"
} }
] ]
} }
6.2. Getting a Nonce 7.2. Getting a Nonce
Before sending a POST request to the server, an ACME client needs to Before sending a POST request to the server, an ACME client needs to
have a fresh anti-replay nonce to put in the "nonce" header of the have a fresh anti-replay nonce to put in the "nonce" header of the
JWS. In most cases, the client will have gotten a nonce from a JWS. In most cases, the client will have gotten a nonce from a
previous request. However, the client might sometimes need to get a previous request. However, the client might sometimes need to get a
new nonce, e.g., on its first request to the server or if an existing new nonce, e.g., on its first request to the server or if an existing
nonce is no longer valid. nonce is no longer valid.
To get a fresh nonce, the client sends a HEAD request to the new- To get a fresh nonce, the client sends a HEAD request to the new-
nonce resource on the server. The server's response MUST include a nonce resource on the server. The server's response MUST include a
Replay-Nonce header field containing a fresh nonce, and SHOULD have Replay-Nonce header field containing a fresh nonce, and SHOULD have
status code 204 (No Content). The server SHOULD also respond to GET status code 204 (No Content). The server SHOULD also respond to GET
requests for this resource, returning an empty body (while still requests for this resource, returning an empty body (while still
providing a Replay-Nonce header). providing a Replay-Nonce header) with a 204 (No Content) status.
HEAD /acme/new-nonce HTTP/1.1 HEAD /acme/new-nonce HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 204 No Content HTTP/1.1 204 No Content
Replay-Nonce: oFvnlFP1wIhRlYS2jTaXbA Replay-Nonce: oFvnlFP1wIhRlYS2jTaXbA
Cache-Control: no-store Cache-Control: no-store
Proxy caching of responses from the new-nonce resource can cause Proxy caching of responses from the new-nonce resource can cause
clients receive the same nonce repeatedly, leading to badNonce clients receive the same nonce repeatedly, leading to badNonce
errors. The server MUST include a Cache-Control header field with errors. The server MUST include a Cache-Control header field with
the "no-store" directive in responses for the new-nonce resource, in the "no-store" directive in responses for the new-nonce resource, in
order to prevent caching of this resource. order to prevent caching of this resource.
6.3. Account Creation 7.3. Account Creation
A client creates a new account with the server by sending a POST A client creates a new account with the server by sending a POST
request to the server's new-account URI. The body of the request is request to the server's new-account URI. The body of the request is
a stub account object containing only the "contact" field. a stub account object containing the "contact" field and optionally
the "terms-of-service-agreed" field.
POST /acme/new-account HTTP/1.1 POST /acme/new-account HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"jwk": {...}, "jwk": {...},
"nonce": "6S8IqOGY7eL2lsGoTZYifg", "nonce": "6S8IqOGY7eL2lsGoTZYifg",
skipping to change at page 25, line 45 skipping to change at page 24, line 46
"payload": base64url({ "payload": base64url({
"terms-of-service-agreed": true, "terms-of-service-agreed": true,
"contact": [ "contact": [
"mailto:cert-admin@example.com", "mailto:cert-admin@example.com",
"tel:+12025551212" "tel:+12025551212"
] ]
}), }),
"signature": "RZPOnYoPs1PhjszF...-nh6X1qtOFPB519I" "signature": "RZPOnYoPs1PhjszF...-nh6X1qtOFPB519I"
} }
The server MUST ignore any values provided in the "key", and "orders" The server MUST ignore any values provided in the "orders" fields in
fields in account bodies sent by the client, as well as any other account bodies sent by the client, as well as any other fields that
fields that it does not recognize. If new fields are specified in it does not recognize. If new fields are specified in the future,
the future, the specification of those fields MUST describe whether the specification of those fields MUST describe whether they can be
they may be provided by the client. provided by the client.
In general, the server MUST ignore any fields in the request object In general, the server MUST ignore any fields in the request object
that it does not recognize. In particular, it MUST NOT reflect that it does not recognize. In particular, it MUST NOT reflect
unrecognized fields in the resulting account object. This allows unrecognized fields in the resulting account object. This allows
clients to detect when servers do not support an extension field. clients to detect when servers do not support an extension field.
The server SHOULD validate that the contact URLs in the "contact" The server SHOULD validate that the contact URLs in the "contact"
field are valid and supported by the server. If the client provides field are valid and supported by the server. If the client provides
the server with an invalid or unsupported contact URL, then the the server with an invalid or unsupported contact URL, then the
server MUST return an error of type "invalidContact", with a server MUST return an error of type "invalidContact", with a
description describing the error and what types of contact URL the description describing the error and what types of contact URL the
server considers acceptable. server considers acceptable.
The server creates an account object with the included contact The server creates an account and stores the public key used to
information. The "key" element of the account is set to the public verify the JWS (i.e., the "jwk" element of the JWS header) to
key used to verify the JWS (i.e., the "jwk" element of the JWS authenticate future requests from the account. The server returns
header). The server returns this account object in a 201 (Created) this account object in a 201 (Created) response, with the account URI
response, with the account URI in a Location header field. in a Location header field.
If the server already has an account registered with the provided If the server already has an account registered with the provided
account key, then it MUST return a 200 (OK) response and provide the account key, then it MUST return a response with a 200 (OK) status
URI of that account in a Content-Location header field. This allows code and provide the URI of that account in the Location header
a client that has an account key but not the corresponding account field. This allows a client that has an account key but not the
URI to recover the account URI. corresponding account URI to recover the account URI.
If the server wishes to present the client with terms under which the If the server wishes to present the client with terms under which the
ACME service is to be used, it MUST indicate the URI where such terms ACME service is to be used, it MUST indicate the URI where such terms
can be accessed in the "terms-of-service" subfield of the "meta" can be accessed in the "terms-of-service" subfield of the "meta"
field in the directory object, and the server MUST reject new-account field in the directory object, and the server MUST reject new-account
requests that do not have the "terms-of-service-agreed" set to requests that do not have the "terms-of-service-agreed" set to
"true". Clients SHOULD NOT automatically agree to terms by default. "true". Clients SHOULD NOT automatically agree to terms by default.
Rather, they SHOULD require some user interaction for agreement to Rather, they SHOULD require some user interaction for agreement to
terms. terms.
HTTP/1.1 201 Created HTTP/1.1 201 Created
Content-Type: application/json Content-Type: application/json
Replay-Nonce: D8s4D2mLs8Vn-goWuPQeKA Replay-Nonce: D8s4D2mLs8Vn-goWuPQeKA
Location: https://example.com/acme/acct/1 Location: https://example.com/acme/acct/1
Link: <https://example.com/acme/some-directory>;rel="directory" Link: <https://example.com/acme/some-directory>;rel="index"
{ {
"key": { /* JWK from JWS header */ },
"status": "valid", "status": "valid",
"contact": [ "contact": [
"mailto:cert-admin@example.com", "mailto:cert-admin@example.com",
"tel:+12025551212" "tel:+12025551212"
] ]
} }
If the client wishes to update this information in the future, it If the client wishes to update this information in the future, it
sends a POST request with updated information to the account URI. sends a POST request with updated information to the account URI.
The server MUST ignore any updates to the "key", or "order" fields or The server MUST ignore any updates to "order" fields or any other
any other fields it does not recognize. The server MUST verify that fields it does not recognize.
the request is signed with the private key corresponding to the "key"
field of the request before updating the registration.
For example, to update the contact information in the above account, For example, to update the contact information in the above account,
the client could send the following request: the client could send the following request:
POST /acme/acct/1 HTTP/1.1 POST /acme/acct/1 HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
skipping to change at page 27, line 39 skipping to change at page 26, line 37
] ]
}), }),
"signature": "hDXzvcj8T6fbFbmn...rDzXzzvzpRy64N0o" "signature": "hDXzvcj8T6fbFbmn...rDzXzzvzpRy64N0o"
} }
Servers SHOULD NOT respond to GET requests for account resources as Servers SHOULD NOT respond to GET requests for account resources as
these requests are not authenticated. If a client wishes to query these requests are not authenticated. If a client wishes to query
the server for information about its account (e.g., to examine the the server for information about its account (e.g., to examine the
"contact" or "certificates" fields), then it SHOULD do so by sending "contact" or "certificates" fields), then it SHOULD do so by sending
a POST request with an empty update. That is, it should send a JWS a POST request with an empty update. That is, it should send a JWS
whose payload is trivial ({}). whose payload is an empty object ({}).
6.3.1. Changes of Terms of Service 7.3.1. Changes of Terms of Service
As described above, a client can indicate its agreement with the CA's As described above, a client can indicate its agreement with the CA's
terms of service by setting the "terms-of-service-agreed" field in terms of service by setting the "terms-of-service-agreed" field in
its account object to "true". its account object to "true".
If the server has changed its terms of service since a client If the server has changed its terms of service since a client
initially agreed, and the server is unwilling to process a request initially agreed, and the server is unwilling to process a request
without explicit agreement to the new terms, then it MUST return an without explicit agreement to the new terms, then it MUST return an
error response with status code 403 (Forbidden) and type error response with status code 403 (Forbidden) and type
"urn:ietf:params:acme:error:userActionRequired". This response MUST "urn:ietf:params:acme:error:userActionRequired". This response MUST
skipping to change at page 28, line 23 skipping to change at page 27, line 21
Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw
Content-Type: application/problem+json Content-Type: application/problem+json
Content-Language: en Content-Language: en
{ {
"type": "urn:ietf:params:acme:error:userActionRequired", "type": "urn:ietf:params:acme:error:userActionRequired",
"detail": "Terms of service have changed", "detail": "Terms of service have changed",
"instance": "http://example.com/agreement/?token=W8Ih3PswD-8" "instance": "http://example.com/agreement/?token=W8Ih3PswD-8"
} }
6.3.2. External Account Binding 7.3.2. External Account Binding
The server MAY require a value to be present for the "external- The server MAY require a value to be present for the "external-
account-binding" field. This can be used to an ACME account with an account-binding" field. This can be used to an ACME account with an
existing account in a non-ACME system, such as a CA customer existing account in a non-ACME system, such as a CA customer
database. database.
To enable ACME account binding, a CA needs to provision the ACME To enable ACME account binding, a CA needs to provision the ACME
client with a MAC key and a key identifier. The key identifier MUST client with a MAC key and a key identifier. The key identifier MUST
be an ASCII string. The MAC key SHOULD be provided in base64url- be an ASCII string. The MAC key SHOULD be provided in base64url-
encoded form, to maximize compatibility between provisioning systems encoded form, to maximize compatibility between provisioning systems
skipping to change at page 29, line 5 skipping to change at page 28, line 5
o The "kid" field MUST contain the key identifier provided by the CA o The "kid" field MUST contain the key identifier provided by the CA
o The "nonce" field MUST NOT be present o The "nonce" field MUST NOT be present
o The "url" field MUST be set to the same value as the outer JWS o The "url" field MUST be set to the same value as the outer JWS
The "signature" field of the JWS will contain the MAC value computed The "signature" field of the JWS will contain the MAC value computed
with the MAC key provided by the CA. with the MAC key provided by the CA.
POST /acme/new-reg HTTP/1.1 POST /acme/new-account HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"jwk": /* account key */, "jwk": /* account key */,
"nonce": "K60BWPrMQG9SDxBDS_xtSw", "nonce": "K60BWPrMQG9SDxBDS_xtSw",
"url": "https://example.com/acme/new-account" "url": "https://example.com/acme/new-account"
}), }),
skipping to change at page 29, line 34 skipping to change at page 28, line 34
"url": "https://example.com/acme/new-account" "url": "https://example.com/acme/new-account"
}), }),
"payload": base64url(/* same as in "jwk" above */), "payload": base64url(/* same as in "jwk" above */),
"signature": /* MAC using MAC key from CA */ "signature": /* MAC using MAC key from CA */
} }
}), }),
"signature": "5TWiqIYQfIDfALQv...x9C2mg8JGPxl5bI4" "signature": "5TWiqIYQfIDfALQv...x9C2mg8JGPxl5bI4"
} }
When a CA receives a new-account request containing an "external- When a CA receives a new-account request containing an "external-
account-binding" field, it must decide whether or not to verify the account-binding" field, it decides whether or not to verify the
binding. If the CA does not verify the binding, then it MUST NOT binding. If the CA does not verify the binding, then it MUST NOT
reflect the "external-account-binding" field in the resulting account reflect the "external-account-binding" field in the resulting account
object (if any). To verify the account binding, the CA MUST take the object (if any). To verify the account binding, the CA MUST take the
following steps: following steps:
1. Verify that the value of the field is a well-formed JWS 1. Verify that the value of the field is a well-formed JWS
2. Verify that the JWS protected meets the above criteria 2. Verify that the JWS protected meets the above criteria
3. Retrieve the MAC key corresponding to the key identifier in the 3. Retrieve the MAC key corresponding to the key identifier in the
"kid" field "kid" field
4. Verify that the MAC on the JWS verifies using that MAC key 4. Verify that the MAC on the JWS verifies using that MAC key
5. Verify that the payload of the JWS represents the same key as was 5. Verify that the payload of the JWS represents the same key as was
used to verify the outer JWS (i.e., the "jwk" field of the outer used to verify the outer JWS (i.e., the "jwk" field of the outer
JWS) JWS)
If all of these checks pass and the CA creates a new account, then If all of these checks pass and the CA creates a new account, then
the CA may consider the new account associated with the external the CA may consider the new account associated with the external
account corresponding to the MAC key, and MUST reflect value of the account corresponding to the MAC key and MUST reflect value of the
"external-account-binding" field in the resulting account object. If "external-account-binding" field in the resulting account object. If
any of these checks fail, then the CA MUST reject the new- any of these checks fail, then the CA MUST reject the new-account
registration request. request.
6.3.3. Account Key Roll-over 7.3.3. Account Key Roll-over
A client may wish to change the public key that is associated with a A client may wish to change the public key that is associated with an
account in order to recover from a key compromise or proactively account in order to recover from a key compromise or proactively
mitigate the impact of an unnoticed key compromise. mitigate the impact of an unnoticed key compromise.
To change the key associated with an account, the client first To change the key associated with an account, the client first
constructs a key-change object describing the change that it would constructs a key-change object describing the change that it would
like the server to make: like the server to make:
account (required, string): The URL for account being modified. The account (required, string): The URL for account being modified. The
content of this field MUST be the exact string provided in the content of this field MUST be the exact string provided in the
Location header field in response to the new-account request that Location header field in response to the new-account request that
created the account. created the account.
newKey (required, JWK): The JWK representation of the new key newKey (required, JWK): The JWK representation of the new key
The client then encapsulates the key-change object in a JWS, signed The client then encapsulates the key-change object in a JWS, signed
with the requested new account key (i.e., the key matching the with the requested new account key (i.e., the key matching the
"newKey" value). "newKey" value).
The outer JWS MUST meet the normal requirements for an ACME JWS (see The outer JWS MUST meet the normal requirements for an ACME JWS (see
Section 5.2). The inner JWS MUST meet the normal requirements, with Section 6.2). The inner JWS MUST meet the normal requirements, with
the following exceptions: the following exceptions:
o The inner JWS MUST have the same "url" parameter as the outer JWS. o The inner JWS MUST have the same "url" parameter as the outer JWS.
o The inner JWS is NOT REQUIRED to have a "nonce" parameter. The o The inner JWS is NOT REQUIRED to have a "nonce" parameter. The
server MUST ignore any value provided for the "nonce" header server MUST ignore any value provided for the "nonce" header
parameter. parameter.
This transaction has signatures from both the old and new keys so This transaction has signatures from both the old and new keys so
that the server can verify that the holders of the two keys both that the server can verify that the holders of the two keys both
skipping to change at page 31, line 38 skipping to change at page 30, line 38
"signature": "5TWiqIYQfIDfALQv...x9C2mg8JGPxl5bI4" "signature": "5TWiqIYQfIDfALQv...x9C2mg8JGPxl5bI4"
} }
On receiving key-change request, the server MUST perform the On receiving key-change request, the server MUST perform the
following steps in addition to the typical JWS validation: following steps in addition to the typical JWS validation:
1. Validate the POST request belongs to a currently active account, 1. Validate the POST request belongs to a currently active account,
as described in Message Transport. as described in Message Transport.
2. Check that the payload of the JWS is a well-formed JWS object 2. Check that the payload of the JWS is a well-formed JWS object
(the "inner JWS") (the "inner JWS").
3. Check that the JWS protected header of the inner JWS has a "jwk" 3. Check that the JWS protected header of the inner JWS has a "jwk"
field. field.
4. Check that the inner JWS verifies using the key in its "jwk" 4. Check that the inner JWS verifies using the key in its "jwk"
field field.
5. Check that the payload of the inner JWS is a well-formed key- 5. Check that the payload of the inner JWS is a well-formed key-
change object (as described above) change object (as described above).
6. Check that the "url" parameters of the inner and outer JWSs are 6. Check that the "url" parameters of the inner and outer JWSs are
the same the same.
7. Check that the "account" field of the key-change object contains 7. Check that the "account" field of the key-change object contains
the URL for the account matching the old key the URL for the account matching the old key
8. Check that the "newKey" field of the key-change object contains 8. Check that the "newKey" field of the key-change object also
the key used to sign the inner JWS. verifies the inner JWS.
If all of these checks pass, then the server updates the If all of these checks pass, then the server updates the
corresponding account by replacing the old account key with the new corresponding account by replacing the old account key with the new
public key and returns status code 200. Otherwise, the server public key and returns status code 200. Otherwise, the server
responds with an error status code and a problem document describing responds with an error status code and a problem document describing
the error. the error.
6.3.4. Account deactivation 7.3.4. Account deactivation
A client may deactivate an account by posting a signed update to the A client can deactivate an account by posting a signed update to the
server with a status field of "deactivated." Clients may wish to do server with a status field of "deactivated." Clients may wish to do
this when the account key is compromised. this when the account key is compromised or decommissioned.
POST /acme/acct/1 HTTP/1.1 POST /acme/acct/1 HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/1", "kid": "https://example.com/acme/acct/1",
"nonce": "ntuJWWSic4WVNSqeUmshgg", "nonce": "ntuJWWSic4WVNSqeUmshgg",
"url": "https://example.com/acme/acct/1" "url": "https://example.com/acme/acct/1"
}), }),
"payload": base64url({ "payload": base64url({
"status": "deactivated" "status": "deactivated"
}), }),
"signature": "earzVLd3m5M4xJzR...bVTqn7R08AKOVf3Y" "signature": "earzVLd3m5M4xJzR...bVTqn7R08AKOVf3Y"
} }
The server MUST verify that the request is signed by the account key. The server MUST verify that the request is signed by the account key.
If the server accepts the deactivation request, it should reply with If the server accepts the deactivation request, it replies with a 200
a 200 (OK) status code and the current contents of the account (OK) status code and the current contents of the account object.
object.
Once an account is deactivated, the server MUST NOT accept further Once an account is deactivated, the server MUST NOT accept further
requests authorized by that account's key. It is up to server policy requests authorized by that account's key. A server may take a
how long to retain data related to that account, whether to revoke variety of actions in response to an account deactivation, e.g.,
certificates issued by that account, and whether to send email to deleting data related to that account or sending mail to the
that account's contacts. ACME does not provide a way to reactivate a account's contacts. Servers SHOULD NOT revoke certificates issued by
deactivated account. the deactivated account, since this could cause operational
disruption for servers using these certificates. ACME does not
provide a way to reactivate a deactivated account.
6.4. Applying for Certificate Issuance 7.4. Applying for Certificate Issuance
A client may use ACME to submit an order for a certificate to be The client requests certificate issuance by sending a POST request to
issued. The client makes this request by sending a POST request to
the server's new-order resource. The body of the POST is a JWS the server's new-order resource. The body of the POST is a JWS
object whose JSON payload is a subset of the order object defined in object whose JSON payload is a subset of the order object defined in
Section 6.1.3, containing the fields that describe the certificate to Section 7.1.3, containing the fields that describe the certificate to
be issued: be issued:
csr (required, string): A CSR encoding the parameters for the csr (required, string): A CSR encoding the parameters for the
certificate being requested [RFC2986]. The CSR is sent in the certificate being requested [RFC2986]. The CSR is sent in the
base64url-encoded version of the DER format. (Note: Because this base64url-encoded version of the DER format. (Note: Because this
field uses base64url, and does not include headers, it is field uses base64url, and does not include headers, it is
different from PEM.) different from PEM.)
notBefore (optional, string): The requested value of the notBefore notBefore (optional, string): The requested value of the notBefore
field in the certificate, in the date format defined in [RFC3339] field in the certificate, in the date format defined in [RFC3339]
skipping to change at page 33, line 51 skipping to change at page 32, line 50
}), }),
"signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g" "signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g"
} }
The CSR encodes the client's requests with regard to the content of The CSR encodes the client's requests with regard to the content of
the certificate to be issued. The CSR MUST indicate the requested the certificate to be issued. The CSR MUST indicate the requested
identifiers, either in the commonName portion of the requested identifiers, either in the commonName portion of the requested
subject name, or in an extensionRequest attribute [RFC2985] subject name, or in an extensionRequest attribute [RFC2985]
requesting a subjectAltName extension. requesting a subjectAltName extension.
The server MUST return an error if it cannot fulfil the request as The server MUST return an error if it cannot fulfill the request as
specified, and MUST NOT issue a certificate with contents other than specified, and MUST NOT issue a certificate with contents other than
those requested. If the server requires the request to be modified those requested. If the server requires the request to be modified
in a certain way, it should indicate the required changes using an in a certain way, it should indicate the required changes using an
appropriate error code and description. appropriate error type and description.
If the server is willing to issue the requested certificate, it If the server is willing to issue the requested certificate, it
responds with a 201 (Created) response. The body of this response is responds with a 201 (Created) response. The body of this response is
an order object reflecting the client's request and any an order object reflecting the client's request and any
authorizations the client must complete before the certificate will authorizations the client must complete before the certificate will
be issued. be issued.
HTTP/1.1 201 Created HTTP/1.1 201 Created
Replay-Nonce: MYAuvOpaoIiywTezizk5vw Replay-Nonce: MYAuvOpaoIiywTezizk5vw
Location: https://example.com/acme/order/asdf Location: https://example.com/acme/order/asdf
skipping to change at page 34, line 38 skipping to change at page 33, line 37
"https://example.com/acme/authz/2345" "https://example.com/acme/authz/2345"
] ]
} }
The order object returned by the server represents a promise that if The order object returned by the server represents a promise that if
the client fulfills the server's requirements before the "expires" the client fulfills the server's requirements before the "expires"
time, then the server will issue the requested certificate. In the time, then the server will issue the requested certificate. In the
order object, any authorization referenced in the "authorizations" order object, any authorization referenced in the "authorizations"
array whose status is "pending" represents an authorization array whose status is "pending" represents an authorization
transaction that the client must complete before the server will transaction that the client must complete before the server will
issue the certificate (see Section 6.5). If the client fails to issue the certificate (see Section 7.5). If the client fails to
complete the required actions before the "expires" time, then the complete the required actions before the "expires" time, then the
server SHOULD change the status of the order to "invalid" and MAY server SHOULD change the status of the order to "invalid" and MAY
delete the order resource. delete the order resource.
The server MUST issue the requested certificate and update the order The server MUST issue the requested certificate and update the order
resource with a URL for the certificate shortly after the client has resource with a URL for the certificate shortly after the client has
fulfilled the server's requirements. If the client has already fulfilled the server's requirements. If the client has already
satisfied the server's requirements at the time of this request satisfied the server's requirements at the time of this request
(e.g., by obtaining authorization for all of the identifiers in the (e.g., by obtaining authorization for all of the identifiers in the
certificate in previous transactions), then the server MUST certificate in previous transactions), then the server MUST
skipping to change at page 35, line 25 skipping to change at page 34, line 23
o "pending": The server does not believe that the client has o "pending": The server does not believe that the client has
fulfilled the requirements. Check the "authorizations" array for fulfilled the requirements. Check the "authorizations" array for
entries that are still pending. entries that are still pending.
o "processing": The server agrees that the requirements have been o "processing": The server agrees that the requirements have been
fulfilled, and is in the process of generating the certificate. fulfilled, and is in the process of generating the certificate.
Retry after the time given in the "Retry-After" header field of Retry after the time given in the "Retry-After" header field of
the response, if any. the response, if any.
o "valid": The server has issued the certificate and provisioned its o "valid": The server has issued the certificate and provisioned its
URL to the "certificate" field of the order. Download the URL to the "certificate" field of the order.
certificate.
6.4.1. Pre-Authorization 7.4.1. Pre-Authorization
The order process described above presumes that authorization objects The order process described above presumes that authorization objects
are created reactively, in response to a certificate order. Some are created reactively, in response to a certificate order. Some
servers may also wish to enable clients to obtain authorization for servers may also wish to enable clients to obtain authorization for
an identifier proactively, outside of the context of a specific an identifier proactively, outside of the context of a specific
issuance. For example, a client hosting virtual servers for a issuance. For example, a client hosting virtual servers for a
collection of names might wish to obtain authorization before any collection of names might wish to obtain authorization before any
servers are created, and only create a certificate when a server virtual servers are created and only create a certificate when a
starts up. virtual server starts up.
In some cases, a CA running an ACME server might have a completely In some cases, a CA running an ACME server might have a completely
external, non-ACME process for authorizing a client to issue for an external, non-ACME process for authorizing a client to issue for an
identifier. In these case, the CA should provision its ACME server identifier. In these case, the CA should provision its ACME server
with authorization objects corresponding to these authorizations and with authorization objects corresponding to these authorizations and
reflect them as already valid in any orders submitted by the client. reflect them as already valid in any orders submitted by the client.
If a CA wishes to allow pre-authorization within ACME, it can offer a If a CA wishes to allow pre-authorization within ACME, it can offer a
"new authorization" resource in its directory by adding the key "new- "new authorization" resource in its directory by adding the key "new-
authz" with a URL for the new authorization resource. authz" with a URL for the new authorization resource.
To request authorization for an identifier, the client sends a POST To request authorization for an identifier, the client sends a POST
request to the new-authorization resource specifying the identifier request to the new-authorization resource specifying the identifier
for which authorization is being requested and how the server should for which authorization is being requested and how the server should
behave with respect to existing authorizations for this identifier. behave with respect to existing authorizations for this identifier.
identifier (required, dictionary of string): The identifier that the identifier (required, object): The identifier that the account is
account is authorized to represent authorized to represent:
type (required, string): The type of identifier. type (required, string): The type of identifier.
value (required, string): The identifier itself. value (required, string): The identifier itself.
existing (optional, string): How an existing authorization should be
handled. Possible values are "accept" and "require".
POST /acme/new-authz HTTP/1.1 POST /acme/new-authz HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"jwk": {...}, "jwk": {...},
"nonce": "uQpSjlRb4vQVCjVYAyyUWg", "nonce": "uQpSjlRb4vQVCjVYAyyUWg",
"url": "https://example.com/acme/new-authz" "url": "https://example.com/acme/new-authz"
}), }),
"payload": base64url({ "payload": base64url({
"identifier": { "identifier": {
"type": "dns", "type": "dns",
"value": "example.net" "value": "example.net"
}, }
"existing": "accept"
}), }),
"signature": "nuSDISbWG8mMgE7H...QyVUL68yzf3Zawps" "signature": "nuSDISbWG8mMgE7H...QyVUL68yzf3Zawps"
} }
Before processing the authorization request, the server SHOULD Before processing the authorization request, the server SHOULD
determine whether it is willing to issue certificates for the determine whether it is willing to issue certificates for the
identifier. For example, the server should check that the identifier identifier. For example, the server should check that the identifier
is of a supported type. Servers might also check names against a is of a supported type. Servers might also check names against a
blacklist of known high-value identifiers. If the server is blacklist of known high-value identifiers. If the server is
unwilling to issue for the identifier, it SHOULD return a 403 unwilling to issue for the identifier, it SHOULD return a 403
(Forbidden) error, with a problem document describing the reason for (Forbidden) error, with a problem document describing the reason for
the rejection. the rejection.
If the authorization request specifies "existing" with a value of
"accept" or "require", before proceeding, the server SHOULD determine
whether there are any existing, valid authorization resources for the
account and given identifier. If one or more such authorizations
exists, a response SHOULD returned with status code 303 (See Other)
and a Location header pointing to the existing resource URL;
processing of the request then stops. If there are multiple such
authorizations, the authorization with the latest expiry date SHOULD
be returned. If no existing authorizations were found and the value
for "existing" was "require", then the server MUST return status code
404 (Not Found); if it was "accept" or was any other value or was
absent, processing continues as follows.
If the server is willing to proceed, it builds a pending If the server is willing to proceed, it builds a pending
authorization object from the inputs submitted by the client. authorization object from the inputs submitted by the client.
o "identifier" the identifier submitted by the client o "identifier" the identifier submitted by the client
o "status": MUST be "pending" unless the server has out-of-band o "status" MUST be "pending" unless the server has out-of-band
information about the client's authorization status information about the client's authorization status
o "challenges" and "combinations": As selected by the server's o "challenges" and "combinations" as selected by the server's policy
policy for this identifier for this identifier
The server allocates a new URI for this authorization, and returns a The server allocates a new URI for this authorization, and returns a
201 (Created) response, with the authorization URI in a Location 201 (Created) response, with the authorization URI in the Location
header field, and the JSON authorization object in the body. The header field, and the JSON authorization object in the body. The
client then follows the process described in Section 6.5 to complete client then follows the process described in Section 7.5 to complete
the authorization process. the authorization process.
6.4.2. Downloading the Certificate 7.4.2. Downloading the Certificate
To download the issued certificate, the client simply sends a GET To download the issued certificate, the client simply sends a GET
request to the certificate URL. request to the certificate URL.
The default format of the certificate is PEM (application/x-pem-file) The default format of the certificate is application/pem-certificate-
as specified by [RFC7468]. This format should contain the end-entity chain (see IANA Considerations).
certificate first, followed by any intermediate certificates that are
needed to build a path to a trusted root. Servers SHOULD NOT include
self-signed trust anchors. The client may request other formats by
including an Accept header in its request. For example, the client
may use the media type application/pkix-cert to request the end-
entity certificate in DER format.
The server MAY provide one or more link relation header fields The server MAY provide one or more link relation header fields
[RFC5988] with relation "alternate". Each such field should express [RFC5988] with relation "alternate". Each such field SHOULD express
an alternative certificate chain starting with the same end-entity an alternative certificate chain starting with the same end-entity
certificate. This can be used to express paths to various trust certificate. This can be used to express paths to various trust
anchors. Clients can fetch these alternates and use their own anchors. Clients can fetch these alternates and use their own
heuristics to decide which is optimal. heuristics to decide which is optimal.
The server MUST also provide a link relation header field with
relation "author" to indicate the order under which this certificate
was issued.
If the CA participates in Certificate Transparency (CT) [RFC6962],
then they may want to provide the client with a Signed Certificate
Timestamp (SCT) that can be used to prove that a certificate was
submitted to a CT log. An SCT can be included as an extension in the
certificate or as an extension to OCSP responses for the certificate.
The server can also provide the client with direct access to an SCT
for a certificate using a Link relation header field with relation
"ct-sct".
GET /acme/cert/asdf HTTP/1.1 GET /acme/cert/asdf HTTP/1.1
Host: example.com Host: example.com
Accept: application/pkix-cert Accept: application/pkix-cert
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/pkix-cert Content-Type: application/pem-certificate-chain
Link: <https://example.com/acme/ca-cert>;rel="up";title="issuer" Link: <https://example.com/acme/some-directory>;rel="index"
Link: <https://example.com/acme/revoke-cert>;rel="revoke"
Link: <https://example.com/acme/order/asdf>;rel="author"
Link: <https://example.com/acme/sct/asdf>;rel="ct-sct"
Link: <https://example.com/acme/some-directory>;rel="directory"
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[End-entity certificate contents] [End-entity certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[Issuer certificate contents] [Issuer certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[Other certificate contents] [Other certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
skipping to change at page 39, line 5 skipping to change at page 36, line 50
A certificate resource represents a single, immutable certificate. A certificate resource represents a single, immutable certificate.
If the client wishes to obtain a renewed certificate, the client If the client wishes to obtain a renewed certificate, the client
initiates a new order process to request one. initiates a new order process to request one.
Because certificate resources are immutable once issuance is Because certificate resources are immutable once issuance is
complete, the server MAY enable the caching of the resource by adding complete, the server MAY enable the caching of the resource by adding
Expires and Cache-Control headers specifying a point in time in the Expires and Cache-Control headers specifying a point in time in the
distant future. These headers have no relation to the certificate's distant future. These headers have no relation to the certificate's
period of validity. period of validity.
6.5. Identifier Authorization The ACME client MAY request other formats by including an Accept
header in its request. For example, the client could use the media
type "application/pkix-cert" [RFC2585] to request the end-entity
certificate in DER format. Server support for alternate formats is
OPTIONAL. For formats that can only express a single certificate,
the server SHOULD provide one or more "Link: rel="up"" headers
pointing to an issuer or issuers so that ACME clients can build a
certificate chain as defined in TLS.
7.5. Identifier Authorization
The identifier authorization process establishes the authorization of The identifier authorization process establishes the authorization of
an account to manage certificates for a given identifier. This an account to manage certificates for a given identifier. This
process must assure the server of two things: First, that the client process assures the server of two things:
controls the private key of the account key pair, and second, that
the client controls the identifier in question. This process may be 1. That the client controls the private key of the account key pair,
repeated to associate multiple identifiers to a key pair (e.g., to and
request certificates with multiple identifiers), or to associate
multiple accounts with an identifier (e.g., to allow multiple 2. That the client controls the identifier in question.
entities to manage certificates). The server may declare that an
authorization is only valid for a specific order by setting the This process may be repeated to associate multiple identifiers to a
"scope" field of the authorization to the URI for that order. key pair (e.g., to request certificates with multiple identifiers),
or to associate multiple accounts with an identifier (e.g., to allow
multiple entities to manage certificates). The server may declare
that an authorization is only valid for a specific order by setting
the "scope" field of the authorization to the URI for that order.
Authorization resources are created by the server in response to Authorization resources are created by the server in response to
certificate orders or authorization requests submitted by an account certificate orders or authorization requests submitted by an account
key holder; their URLs are provided to the client in the responses to key holder; their URLs are provided to the client in the responses to
these requests. The authorization object is implicitly tied to the these requests. The authorization object is implicitly tied to the
account key used to sign the request. account key used to sign the request.
When a client receives an order from the server it downloads the When a client receives an order from the server it downloads the
authorization resource by sending a GET request to the indicated URL. authorization resources by sending GET requests to the indicated
If the client initiates authorization using a request to the new URLs. If the client initiates authorization using a request to the
authorization resource, it will have already recevied the pending new authorization resource, it will have already received the pending
authorization object in the response to that request. authorization object in the response to that request.
GET /acme/authz/1234 HTTP/1.1 GET /acme/authz/1234 HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Link: <https://example.com/acme/some-directory>;rel="directory" Link: <https://example.com/acme/some-directory>;rel="index"
{ {
"status": "pending", "status": "pending",
"expires": "2018-03-03T14:09:00Z", "expires": "2018-03-03T14:09:00Z",
"identifier": { "identifier": {
"type": "dns", "type": "dns",
"value": "example.org" "value": "example.org"
}, },
skipping to change at page 40, line 40 skipping to change at page 38, line 40
"token": "DGyRejmCefe7v4NfDGDKfA" "token": "DGyRejmCefe7v4NfDGDKfA"
}, },
{ {
"type": "dns-01", "type": "dns-01",
"url": "https://example.com/authz/1234/2", "url": "https://example.com/authz/1234/2",
"token": "DGyRejmCefe7v4NfDGDKfA" "token": "DGyRejmCefe7v4NfDGDKfA"
} }
] ]
} }
6.5.1. Responding to Challenges 7.5.1. Responding to Challenges
To prove control of the identifier and receive authorization, the To prove control of the identifier and receive authorization, the
client needs to respond with information to complete the challenges. client needs to respond with information to complete the challenges.
To do this, the client updates the authorization object received from To do this, the client updates the authorization object received from
the server by filling in any required information in the elements of the server by filling in any required information in the elements of
the "challenges" dictionary. (This is also the stage where the the "challenges" dictionary.
client should perform any actions required by the challenge.)
The client sends these updates back to the server in the form of a The client sends these updates back to the server in the form of a
JSON object with the response fields required by the challenge type, JSON object with the response fields required by the challenge type,
carried in a POST request to the challenge URI (not authorization carried in a POST request to the challenge URI (not authorization
URI). This allows the client to send information only for challenges URI) once it is ready for the server to attempt validation.
it is responding to.
For example, if the client were to respond to the "http-01" challenge For example, if the client were to respond to the "http-01" challenge
in the above authorization, it would send the following request: in the above authorization, it would send the following request:
POST /acme/authz/asdf/0 HTTP/1.1 POST /acme/authz/asdf/0 HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
skipping to change at page 41, line 35 skipping to change at page 39, line 33
"signature": "9cbg5JO1Gf5YLjjz...SpkUfcdPai9uVYYQ" "signature": "9cbg5JO1Gf5YLjjz...SpkUfcdPai9uVYYQ"
} }
The server updates the authorization document by updating its The server updates the authorization document by updating its
representation of the challenge with the response fields provided by representation of the challenge with the response fields provided by
the client. The server MUST ignore any fields in the response object the client. The server MUST ignore any fields in the response object
that are not specified as response fields for this type of challenge. that are not specified as response fields for this type of challenge.
The server provides a 200 (OK) response with the updated challenge The server provides a 200 (OK) response with the updated challenge
object as its body. object as its body.
If the client's response is invalid for some reason, or does not If the client's response is invalid for any reason or does not
provide the server with appropriate information to validate the provide the server with appropriate information to validate the
challenge, then the server MUST return an HTTP error. On receiving challenge, then the server MUST return an HTTP error. On receiving
such an error, the client SHOULD undo any actions that have been such an error, the client SHOULD undo any actions that have been
taken to fulfill the challenge, e.g., removing files that have been taken to fulfill the challenge, e.g., removing files that have been
provisioned to a web server. provisioned to a web server.
The server is said to "finalize" the authorization when it has The server is said to "finalize" the authorization when it has
completed one of the validations, by assigning the authorization a completed one of the validations, by assigning the authorization a
status of "valid" or "invalid", corresponding to whether it considers status of "valid" or "invalid", corresponding to whether it considers
the account authorized for the identifier. If the final state is the account authorized for the identifier. If the final state is
skipping to change at page 42, line 15 skipping to change at page 40, line 10
Usually, the validation process will take some time, so the client Usually, the validation process will take some time, so the client
will need to poll the authorization resource to see when it is will need to poll the authorization resource to see when it is
finalized. For challenges where the client can tell when the server finalized. For challenges where the client can tell when the server
has validated the challenge (e.g., by seeing an HTTP or DNS request has validated the challenge (e.g., by seeing an HTTP or DNS request
from the server), the client SHOULD NOT begin polling until it has from the server), the client SHOULD NOT begin polling until it has
seen the validation request from the server. seen the validation request from the server.
To check on the status of an authorization, the client sends a GET To check on the status of an authorization, the client sends a GET
request to the authorization URI, and the server responds with the request to the authorization URI, and the server responds with the
current authorization object. In responding to poll requests while current authorization object. In responding to poll requests while
the validation is still in progress, the server MUST return a 202 the validation is still in progress, the server MUST return a 200
(Accepted) response, and MAY include a Retry-After header field to (OK) response and MAY include a Retry-After header field to suggest a
suggest a polling interval to the client. polling interval to the client.
GET /acme/authz/asdf HTTP/1.1 GET /acme/authz/asdf HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
{ {
"status": "valid", "status": "valid",
"expires": "2018-09-09T14:09:00Z", "expires": "2018-09-09T14:09:00Z",
skipping to change at page 42, line 45 skipping to change at page 40, line 40
"type": "http-01" "type": "http-01"
"url": "https://example.com/authz/asdf/0", "url": "https://example.com/authz/asdf/0",
"status": "valid", "status": "valid",
"validated": "2014-12-01T12:05:00Z", "validated": "2014-12-01T12:05:00Z",
"token": "IlirfxKKXAsHtmzK29Pj8A", "token": "IlirfxKKXAsHtmzK29Pj8A",
"keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE" "keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE"
} }
] ]
} }
6.5.2. Deactivating an Authorization 7.5.2. Deactivating an Authorization
If a client wishes to relinquish its authorization to issue If a client wishes to relinquish its authorization to issue
certificates for an identifier, then it may request that the server certificates for an identifier, then it may request that the server
deactivate each authorization associated with that identifier by deactivates each authorization associated with it by sending POST
sending a POST request with the static object {"status": requests with the static object {"status": "deactivated"} to each
"deactivated"}. authorization URI.
POST /acme/authz/asdf HTTP/1.1 POST /acme/authz/asdf HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/1", "kid": "https://example.com/acme/acct/1",
"nonce": "xWCM9lGbIyCgue8di6ueWQ", "nonce": "xWCM9lGbIyCgue8di6ueWQ",
skipping to change at page 43, line 25 skipping to change at page 41, line 25
}), }),
"payload": base64url({ "payload": base64url({
"status": "deactivated" "status": "deactivated"
}), }),
"signature": "srX9Ji7Le9bjszhu...WTFdtujObzMtZcx4" "signature": "srX9Ji7Le9bjszhu...WTFdtujObzMtZcx4"
} }
The server MUST verify that the request is signed by the account key The server MUST verify that the request is signed by the account key
corresponding to the account that owns the authorization. If the corresponding to the account that owns the authorization. If the
server accepts the deactivation, it should reply with a 200 (OK) server accepts the deactivation, it should reply with a 200 (OK)
status code and the current contents of the authorization object. status code and the updated contents of the authorization object.
The server MUST NOT treat deactivated authorization objects as The server MUST NOT treat deactivated authorization objects as
sufficient for issuing certificates. sufficient for issuing certificates.
6.6. Certificate Revocation 7.6. Certificate Revocation
To request that a certificate be revoked, the client sends a POST To request that a certificate be revoked, the client sends a POST
request to the ACME server's revoke-cert URI. The body of the POST request to the ACME server's revoke-cert URI. The body of the POST
is a JWS object whose JSON payload contains the certificate to be is a JWS object whose JSON payload contains the certificate to be
revoked: revoked:
certificate (required, string): The certificate to be revoked, in certificate (required, string): The certificate to be revoked, in
the base64url-encoded version of the DER format. (Note: Because the base64url-encoded version of the DER format. (Note: Because
this field uses base64url, and does not include headers, it is this field uses base64url, and does not include headers, it is
different from PEM.) different from PEM.)
reason (optional, int): One of the revocation reasonCodes defined in reason (optional, int): One of the revocation reasonCodes defined in
[RFC5280] Section 5.3.1 to be used when generating OCSP responses Section 5.3.1 of [RFC5280] to be used when generating OCSP
and CRLs. If this field is not set the server SHOULD use the responses and CRLs. If this field is not set the server SHOULD
unspecified (0) reasonCode value when generating OCSP responses use the unspecified (0) reasonCode value when generating OCSP
and CRLs. The server MAY disallow a subset of reasonCodes from responses and CRLs. The server MAY disallow a subset of
being used by the user. reasonCodes from being used by the user. If a request contains a
disallowed reasonCode the server MUST reject it with the error
type "urn:ietf:params:acme:error:badRevocationReason". The
problem document detail SHOULD indicate which reasonCodes are
allowed.
POST /acme/revoke-cert HTTP/1.1 POST /acme/revoke-cert HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/1", // OR "jwk" "kid": "https://example.com/acme/acct/1", // OR "jwk"
"nonce": "JHb54aT_KTXBWQOzGYkt9A", "nonce": "JHb54aT_KTXBWQOzGYkt9A",
"url": "https://example.com/acme/revoke-cert" "url": "https://example.com/acme/revoke-cert"
}), }),
"payload": base64url({ "payload": base64url({
"certificate": "MIIEDTCCAvegAwIBAgIRAP8...", "certificate": "MIIEDTCCAvegAwIBAgIRAP8...",
"reason": 1 "reason": 1
}), }),
"signature": "Q1bURgJoEslbD1c5...3pYdSMLio57mQNN4" "signature": "Q1bURgJoEslbD1c5...3pYdSMLio57mQNN4"
} }
Revocation requests are different from other ACME request in that Revocation requests are different from other ACME requests in that
they can be signed either with an account key pair or the key pair in they can be signed either with an account key pair or the key pair in
the certificate. Before revoking a certificate, the server MUST the certificate. Before revoking a certificate, the server MUST
verify that the key used to sign the request is authorized to revoke verify that the key used to sign the request is authorized to revoke
the certificate. The server SHOULD consider at least the following the certificate. The server SHOULD consider at least the following
accounts authorized for a given certificate: accounts authorized for a given certificate:
o the account that issued the certificate. o the account that issued the certificate.
o an account that holds authorizations for all of the identifiers in o an account that holds authorizations for all of the identifiers in
the certificate. the certificate.
skipping to change at page 45, line 22 skipping to change at page 43, line 22
Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw
Content-Type: application/problem+json Content-Type: application/problem+json
Content-Language: en Content-Language: en
{ {
"type": "urn:ietf:params:acme:error:unauthorized", "type": "urn:ietf:params:acme:error:unauthorized",
"detail": "No authorization provided for name example.net", "detail": "No authorization provided for name example.net",
"instance": "http://example.com/doc/unauthorized" "instance": "http://example.com/doc/unauthorized"
} }
7. Identifier Validation Challenges 8. Identifier Validation Challenges
There are few types of identifiers in the world for which there is a There are few types of identifiers in the world for which there is a
standardized mechanism to prove possession of a given identifier. In standardized mechanism to prove possession of a given identifier. In
all practical cases, CAs rely on a variety of means to test whether all practical cases, CAs rely on a variety of means to test whether
an entity applying for a certificate with a given identifier actually an entity applying for a certificate with a given identifier actually
controls that identifier. controls that identifier.
Challenges provide the server with assurance that an account holder Challenges provide the server with assurance that an account holder
is also the entity that controls an identifier. For each type of is also the entity that controls an identifier. For each type of
challenge, it must be the case that in order for an entity to challenge, it must be the case that in order for an entity to
successfully complete the challenge the entity must both: successfully complete the challenge the entity must both:
o Hold the private key of the account key pair used to respond to o Hold the private key of the account key pair used to respond to
the challenge the challenge
o Control the identifier in question o Control the identifier in question
Section 9 documents how the challenges defined in this document meet Section 10 documents how the challenges defined in this document meet
these requirements. New challenges will need to document how they these requirements. New challenges will need to document how they
do. do.
ACME uses an extensible challenge/response framework for identifier ACME uses an extensible challenge/response framework for identifier
validation. The server presents a set of challenges in the validation. The server presents a set of challenges in the
authorization object it sends to a client (as objects in the authorization object it sends to a client (as objects in the
"challenges" array), and the client responds by sending a response "challenges" array), and the client responds by sending a response
object in a POST request to a challenge URI. object in a POST request to a challenge URI.
This section describes an initial set of challenge types. Each This section describes an initial set of challenge types. Each
skipping to change at page 46, line 27 skipping to change at page 44, line 27
url (required, string): The URL to which a response can be posted. url (required, string): The URL to which a response can be posted.
status (required, string): The status of this authorization. status (required, string): The status of this authorization.
Possible values are: "pending", "valid", and "invalid". Possible values are: "pending", "valid", and "invalid".
validated (optional, string): The time at which this challenge was validated (optional, string): The time at which this challenge was
completed by the server, encoded in the format specified in RFC completed by the server, encoded in the format specified in RFC
3339 [RFC3339]. This field is REQUIRED if the "status" field is 3339 [RFC3339]. This field is REQUIRED if the "status" field is
"valid". "valid".
error (optional, dictionary of string): The error that occurred error (optional, object): The error that occurred while the server
while the server was validating the challenge, if any. This field was validating the challenge, if any. This field is structured as
is structured as a problem document [RFC7807]. a problem document [RFC7807].
All additional fields are specified by the challenge type. If the All additional fields are specified by the challenge type. If the
server sets a challenge's "status" to "invalid", it SHOULD also server sets a challenge's "status" to "invalid", it SHOULD also
include the "error" field to help the client diagnose why they failed include the "error" field to help the client diagnose why the
the challenge. challenge failed.
Different challenges allow the server to obtain proof of different Different challenges allow the server to obtain proof of different
aspects of control over an identifier. In some challenges, like aspects of control over an identifier. In some challenges, like
HTTP, TLS SNI, and DNS, the client directly proves its ability to do HTTP, TLS SNI, and DNS, the client directly proves its ability to do
certain things related to the identifier. The choice of which certain things related to the identifier. The choice of which
challenges to offer to a client under which circumstances is a matter challenges to offer to a client under which circumstances is a matter
of server policy. of server policy.
The identifier validation challenges described in this section all The identifier validation challenges described in this section all
relate to validation of domain names. If ACME is extended in the relate to validation of domain names. If ACME is extended in the
future to support other types of identifier, there will need to be future to support other types of identifiers, there will need to be
new challenge types, and they will need to specify which types of new challenge types, and they will need to specify which types of
identifier they apply to. identifier they apply to.
[[ Editor's Note: In pre-RFC versions of this specification, [[ Editor's Note: In pre-RFC versions of this specification,
challenges are labeled by type, and with the version of the draft in challenges are labeled by type, and with the version of the draft in
which they were introduced. For example, if an HTTP challenge were which they were introduced. For example, if an HTTP challenge were
introduced in version -03 and a breaking change made in version -05, introduced in version -03 and a breaking change made in version -05,
then there would be a challenge labeled "http-03" and one labeled then there would be a challenge labeled "http-03" and one labeled
"http-05" - but not one labeled "http-04", since challenge in version "http-05" - but not one labeled "http-04", since challenge in version
-04 was compatible with one in version -04. ]] -04 was compatible with one in version -03. ]]
7.1. Key Authorizations 8.1. Key Authorizations
Several of the challenges in this document makes use of a key Several of the challenges in this document make use of a key
authorization string. A key authorization is a string that expresses authorization string. A key authorization is a string that expresses
a domain holder's authorization for a specified key to satisfy a a domain holder's authorization for a specified key to satisfy a
specified challenge, by concatenating the token for the challenge specified challenge, by concatenating the token for the challenge
with a key fingerprint, separated by a "." character: with a key fingerprint, separated by a "." character:
key-authz = token || '.' || base64url(JWK\_Thumbprint(accountKey)) key-authz = token || '.' || base64url(JWK_Thumbprint(accountKey))
The "JWK_Thumbprint" step indicates the computation specified in The "JWK_Thumbprint" step indicates the computation specified in
[RFC7638], using the SHA-256 digest. As specified in the individual [RFC7638], using the SHA-256 digest [FIPS180-4]. As noted in JWA
challenges below, the token for a challenge is a JSON string [RFC7518] any prepended zero octets in the JWK object MUST be
comprised entirely of characters in the URL-safe base64 alphabet. stripped before doing the computation.
The "||" operator indicates concatenation of strings.
In computations involving key authorizations, such as the digest
computations required for the DNS and TLS SNI challenges, the key
authorization string MUST be represented in UTF-8 form (or,
equivalently, ASCII).
An example of how to compute a JWK thumbprint can be found in As specified in the individual challenges below, the token for a
Section 3.1 of [RFC7638]. Note that some cryptographic libraries challenge is a string comprised entirely of characters in the URL-
prepend a zero octet to the representation of the RSA public key safe base64 alphabet. The "||" operator indicates concatenation of
parameters N and E, in order to avoid ambiguity with regard to the strings.
sign of the number. As noted in JWA [RFC7518], a JWK object MUST NOT
include this zero octet. That is, any initial zero octets MUST be
stripped before the values are base64url-encoded.
7.2. HTTP 8.2. HTTP
With HTTP validation, the client in an ACME transaction proves its With HTTP validation, the client in an ACME transaction proves its
control over a domain name by proving that it can provision resources control over a domain name by proving that for that domain name it
on an HTTP server that responds for that domain name. The ACME can provision resources to be returned by an HTTP server. The ACME
server challenges the client to provision a file at a specific path, server challenges the client to provision a file at a specific path,
with a specific string as its content. with a specific string as its content.
As a domain may resolve to multiple IPv4 and IPv6 addresses, the As a domain may resolve to multiple IPv4 and IPv6 addresses, the
server will connect to at least one of the hosts found in A and AAAA server will connect to at least one of the hosts found in the DNS A
records, at its discretion. Because many webservers allocate a and AAAA records, at its discretion. Because many web servers
default HTTPS virtual host to a particular low-privilege tenant user allocate a default HTTPS virtual host to a particular low-privilege
in a subtle and non-intuitive manner, the challenge must be completed tenant user in a subtle and non-intuitive manner, the challenge must
over HTTP, not HTTPS. be completed over HTTP, not HTTPS.
type (required, string): The string "http-01" type (required, string): The string "http-01"
token (required, string): A random value that uniquely identifies token (required, string): A random value that uniquely identifies
the challenge. This value MUST have at least 128 bits of entropy, the challenge. This value MUST have at least 128 bits of entropy,
in order to prevent an attacker from guessing it. It MUST NOT in order to prevent an attacker from guessing it. It MUST NOT
contain any characters outside the base64url alphabet and MUST NOT contain any characters outside the base64url alphabet, including
contain any padding characters ("="). padding characters ("=").
GET /acme/authz/1234/0 HTTP/1.1 GET /acme/authz/1234/0 HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
{ {
"type": "http-01", "type": "http-01",
"url": "https://example.com/acme/authz/0", "url": "https://example.com/acme/authz/0",
"status": "pending", "status": "pending",
"token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA" "token": "evaGxfADs6pSRb2LAv9IZf17"
} }
A client responds to this challenge by constructing a key A client responds to this challenge by constructing a key
authorization from the "token" value provided in the challenge and authorization from the "token" value provided in the challenge and
the client's account key. The client then provisions the key the client's account key. The client then provisions the key
authorization as a resource on the HTTP server for the domain in authorization as a resource on the HTTP server for the domain in
question. question.
The path at which the resource is provisioned is comprised of the The path at which the resource is provisioned is comprised of the
fixed prefix ".well-known/acme-challenge/", followed by the "token" fixed prefix ".well-known/acme-challenge/", followed by the "token"
value in the challenge. The value of the resource MUST be the ASCII value in the challenge. The value of the resource MUST be the ASCII
representation of the key authorization. representation of the key authorization.
.well-known/acme-challenge/evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA GET .well-known/acme-challenge/evaGxfADs6pSRb2LAv9IZf17
Host: example.com
HTTP/1.1 200 OK
LoqXcYV8q5ONbJQxbmR7SCTNo3tiAXDfowyjxAjEuX0.9jg46WB3rR_AHD-EBXdN7cBkH1WOu0tA3M9fm21mqTI
The client's response to this challenge indicates its agreement to The client's response to this challenge indicates its agreement to
this challenge by sending the server the key authorization covering this challenge by sending the server the key authorization covering
the challenge's token and the client's account key. the challenge's token and the client's account key.
keyAuthorization (required, string): The key authorization for this keyAuthorization (required, string): The key authorization for this
challenge. This value MUST match the token from the challenge and challenge. This value MUST match the token from the challenge and
the client's account key. the client's account key.
POST /acme/authz/1234/0 POST /acme/authz/1234/0
skipping to change at page 49, line 32 skipping to change at page 47, line 32
On receiving a response, the server MUST verify that the key On receiving a response, the server MUST verify that the key
authorization in the response matches the "token" value in the authorization in the response matches the "token" value in the
challenge and the client's account key. If they do not match, then challenge and the client's account key. If they do not match, then
the server MUST return an HTTP error in response to the POST request the server MUST return an HTTP error in response to the POST request
in which the client sent the challenge. in which the client sent the challenge.
Given a challenge/response pair, the server verifies the client's Given a challenge/response pair, the server verifies the client's
control of the domain by verifying that the resource was provisioned control of the domain by verifying that the resource was provisioned
as expected. as expected.
1. Form a URI by populating the URI template [RFC6570] 1. Construct a URI by populating the URI template [RFC6570]
"http://{domain}/.well-known/acme-challenge/{token}", where: "http://{domain}/.well-known/acme-challenge/{token}", where:
* the domain field is set to the domain name being verified; and * the domain field is set to the domain name being verified; and
* the token field is set to the token in the challenge. * the token field is set to the token in the challenge.
2. Verify that the resulting URI is well-formed. 2. Verify that the resulting URI is well-formed.
3. Dereference the URI using an HTTP GET request. This request MUST 3. Dereference the URI using an HTTP GET request. This request MUST
be sent to TCP port 80 on the server. be sent to TCP port 80 on the HTTP server.
4. Verify that the body of the response is well-formed key 4. Verify that the body of the response is well-formed key
authorization. The server SHOULD ignore whitespace characters at authorization. The server SHOULD ignore whitespace characters at
the end of the body. the end of the body.
5. Verify that key authorization provided by the server matches the 5. Verify that key authorization provided by the HTTP server matches
token for this challenge and the client's account key. the token for this challenge and the client's account key.
The server SHOULD follow redirects when dereferencing the URI.
If all of the above verifications succeed, then the validation is If all of the above verifications succeed, then the validation is
successful. If the request fails, or the body does not pass these successful. If the request fails, or the body does not pass these
checks, then it has failed. checks, then it has failed.
7.3. TLS with Server Name Indication (TLS SNI) 8.3. TLS with Server Name Indication (TLS SNI)
The TLS with Server Name Indication (TLS SNI) validation method The TLS with Server Name Indication (TLS SNI) validation method
proves control over a domain name by requiring the client to proves control over a domain name by requiring the client to
configure a TLS server referenced by an A/AAAA record under the configure a TLS server referenced by the DNS A and AAAA resource
domain name to respond to specific connection attempts utilizing the records for the domain name to respond to specific connection
Server Name Indication extension [RFC6066]. The server verifies the attempts utilizing the Server Name Indication extension [RFC6066].
client's challenge by accessing the reconfigured server and verifying The server verifies the client's challenge by accessing the TLS
a particular challenge certificate is presented. server and verifying a particular certificate is presented.
type (required, string): The string "tls-sni-02" type (required, string): The string "tls-sni-02"
token (required, string): A random value that uniquely identifies token (required, string): A random value that uniquely identifies
the challenge. This value MUST have at least 128 bits of entropy, the challenge. This value MUST have at least 128 bits of entropy,
in order to prevent an attacker from guessing it. It MUST NOT in order to prevent an attacker from guessing it. It MUST NOT
contain any characters outside the base64url alphabet and MUST NOT contain any characters outside the base64url alphabet, including
contain any padding characters ("="). padding characters ("=").
GET /acme/authz/1234/1 HTTP/1.1 GET /acme/authz/1234/1 HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
{ {
"type": "tls-sni-02", "type": "tls-sni-02",
"url": "https://example.com/acme/authz/1234/1", "url": "https://example.com/acme/authz/1234/1",
"status": "pending", "status": "pending",
"token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA" "token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA"
} }
A client responds to this challenge by constructing a self-signed A client responds to this challenge by constructing a self-signed
certificate which the client MUST provision at the domain name certificate which the client MUST provision at the domain name
concerned in order to pass the challenge. concerned in order to pass the challenge.
The certificate may be constructed arbitrarily, except that each The certificate may be constructed arbitrarily, except that each
certificate MUST have exactly two subjectAlternativeNames, SAN A and certificate MUST have exactly two subjectAlternativeNames, SAN A and
SAN B. Both MUST be dNSNames. SAN B. Both MUST be dNSNames.
SAN A MUST be constructed as follows: compute the SHA-256 digest of SAN A MUST be constructed as follows: compute the SHA-256 digest
the UTF-8-encoded challenge token and encode it in lowercase [FIPS180-4] of the challenge token and encode it in lowercase
hexadecimal form. The dNSName is "x.y.token.acme.invalid", where x hexadecimal form. The dNSName is "x.y.token.acme.invalid", where x
is the first half of the hexadecimal representation and y is the is the first half of the hexadecimal representation and y is the
second half. second half.
SAN B MUST be constructed as follows: compute the SHA-256 digest of SAN B MUST be constructed as follows: compute the SHA-256 digest of
the UTF-8 encoded key authorization and encode it in lowercase the key authorization and encode it in lowercase hexadecimal form.
hexadecimal form. The dNSName is "x.y.ka.acme.invalid" where x is The dNSName is "x.y.ka.acme.invalid" where x is the first half of the
the first half of the hexadecimal representation and y is the second hexadecimal representation and y is the second half.
half.
The client MUST ensure that the certificate is served to TLS The client MUST ensure that the certificate is served to TLS
connections specifying a Server Name Indication (SNI) value of SAN A. connections specifying a Server Name Indication (SNI) value of SAN A.
The response to the TLS-SNI challenge simply acknowledges that the The response to the TLS-SNI challenge simply acknowledges that the
client is ready to fulfill this challenge. client is ready to fulfill this challenge.
keyAuthorization (required, string): The key authorization for this keyAuthorization (required, string): The key authorization for this
challenge. This value MUST match the token from the challenge and challenge. This value MUST match the token from the challenge and
the client's account key. the client's account key.
skipping to change at page 51, line 52 skipping to change at page 49, line 51
in which the client sent the challenge. in which the client sent the challenge.
Given a challenge/response pair, the ACME server verifies the Given a challenge/response pair, the ACME server verifies the
client's control of the domain by verifying that the TLS server was client's control of the domain by verifying that the TLS server was
configured appropriately, using these steps: configured appropriately, using these steps:
1. Compute SAN A and SAN B in the same way as the client. 1. Compute SAN A and SAN B in the same way as the client.
2. Open a TLS connection to the domain name being validated, 2. Open a TLS connection to the domain name being validated,
presenting SAN A in the SNI field. This connection MUST be sent presenting SAN A in the SNI field. This connection MUST be sent
to TCP port 443 on the server. In the ClientHello initiating the to TCP port 443 on the TLS server. In the ClientHello initiating
TLS handshake, the server MUST include a server_name extension the TLS handshake, the server MUST include a server_name
(i.e., SNI) containing SAN A. The server SHOULD ensure that it extension (i.e., SNI) containing SAN A. The server SHOULD ensure
does not reveal SAN B in any way when making the TLS connection, that it does not reveal SAN B in any way when making the TLS
such that the presentation of SAN B in the returned certificate connection, such that the presentation of SAN B in the returned
proves association with the client. certificate proves association with the client.
3. Verify that the certificate contains a subjectAltName extension 3. Verify that the certificate contains a subjectAltName extension
containing dNSName entries of SAN A and SAN B and no other containing dNSName entries of SAN A and SAN B and no other
entries. The comparison MUST be insensitive to case and ordering entries. The comparison MUST be insensitive to case and ordering
of names. of names.
It is RECOMMENDED that the server open multiple TLS connections from It is RECOMMENDED that the server opens multiple TLS connections from
various network perspectives, in order to make MitM attacks harder. various network perspectives, in order to make MitM attacks harder.
If all of the above verifications succeed, then the validation is If all of the above verifications succeed, then the validation is
successful. Otherwise, the validation fails. successful. Otherwise, the validation fails.
7.4. DNS 8.4. DNS
When the identifier being validated is a domain name, the client can When the identifier being validated is a domain name, the client can
prove control of that domain by provisioning a resource record under prove control of that domain by provisioning a TXT resource record
it. The DNS challenge requires the client to provision a TXT record containing a designated value for a specific validation domain name.
containing a designated value under a specific validation domain
name.
type (required, string): The string "dns-01" type (required, string): The string "dns-01"
token (required, string): A random value that uniquely identifies token (required, string): A random value that uniquely identifies
the challenge. This value MUST have at least 128 bits of entropy, the challenge. This value MUST have at least 128 bits of entropy,
in order to prevent an attacker from guessing it. It MUST NOT in order to prevent an attacker from guessing it. It MUST NOT
contain any characters outside the base64url alphabet and MUST NOT contain any characters outside the base64url alphabet, including
contain any padding characters ("="). padding characters ("=").
GET /acme/authz/1234/2 HTTP/1.1 GET /acme/authz/1234/2 HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
{ {
"type": "dns-01", "type": "dns-01",
"url": "https://example.com/acme/authz/1234/2", "url": "https://example.com/acme/authz/1234/2",
"status": "pending", "status": "pending",
"token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA" "token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA"
} }
A client responds to this challenge by constructing a key A client responds to this challenge by constructing a key
authorization from the "token" value provided in the challenge and authorization from the "token" value provided in the challenge and
the client's account key. The client then computes the SHA-256 the client's account key. The client then computes the SHA-256
digest of the key authorization. digest [FIPS180-4] of the key authorization.
The record provisioned to the DNS is the base64url encoding of this The record provisioned to the DNS is the base64url encoding of this
digest. The client constructs the validation domain name by digest. The client constructs the validation domain name by
prepending the label "_acme-challenge" to the domain name being prepending the label "_acme-challenge" to the domain name being
validated, then provisions a TXT record with the digest value under validated, then provisions a TXT record with the digest value under
that name. For example, if the domain name being validated is that name. For example, if the domain name being validated is
"example.com", then the client would provision the following DNS "example.com", then the client would provision the following DNS
record: record:
_acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM" _acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM"
skipping to change at page 53, line 48 skipping to change at page 51, line 45
} }
On receiving a response, the server MUST verify that the key On receiving a response, the server MUST verify that the key
authorization in the response matches the "token" value in the authorization in the response matches the "token" value in the
challenge and the client's account key. If they do not match, then challenge and the client's account key. If they do not match, then
the server MUST return an HTTP error in response to the POST request the server MUST return an HTTP error in response to the POST request
in which the client sent the challenge. in which the client sent the challenge.
To validate a DNS challenge, the server performs the following steps: To validate a DNS challenge, the server performs the following steps:
1. Compute the SHA-256 digest of the key authorization 1. Compute the SHA-256 digest [FIPS180-4] of the key authorization
2. Query for TXT records for the validation domain name
2. Query for TXT records under the validation domain name
3. Verify that the contents of one of the TXT records matches the 3. Verify that the contents of one of the TXT records matches the
digest value digest value
It is RECOMMENDED that the server perform multiple DNS queries from
various network perspectives, in order to make MitM attacks harder.
If all of the above verifications succeed, then the validation is If all of the above verifications succeed, then the validation is
successful. If no DNS record is found, or DNS record and response successful. If no DNS record is found, or DNS record and response
payload do not pass these checks, then the validation fails. payload do not pass these checks, then the validation fails.
7.5. Out-of-Band 8.5. Out-of-Band
There may be cases where a server cannot perform automated validation There may be cases where a server cannot perform automated validation
of an identifier, for example if validation requires some manual of an identifier, for example, if validation requires some manual
steps. In such cases, the server may provide an "out of band" (OOB) steps. In such cases, the server may provide an "out of band" (OOB)
challenge to request that the client perform some action outside of challenge to request that the client perform some action outside of
ACME in order to validate possession of the identifier. ACME in order to validate possession of the identifier.
The OOB challenge requests that the client have a human user visit a The OOB challenge requests that the client have a human user visit a
web page to receive instructions on how to validate possession of the web page to receive instructions on how to validate possession of the
identifier, by providing a URL for that web page. identifier, by providing a URL for that web page.
type (required, string): The string "oob-01" type (required, string): The string "oob-01"
skipping to change at page 54, line 43 skipping to change at page 52, line 38
GET /acme/authz/1234/3 HTTP/1.1 GET /acme/authz/1234/3 HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
{ {
"type": "oob-01", "type": "oob-01",
"href": "https://example.com/validate/evaGxfADs6pSRb2LAv9IZ" "href": "https://example.com/validate/evaGxfADs6pSRb2LAv9IZ"
} }
A client responds to this challenge by presenting the indicated URL A client responds to this challenge by presenting the indicated URL
for a human user to navigate to. If the user choses to complete this for a human user to navigate to. If the user chooses to complete
challege (by vising the website and completing its instructions), the this challenge (by visiting the website and completing its
client indicates this by sending a simple acknowledgement response to instructions), the client indicates this by sending a simple
the server. acknowledgement response to the server.
type (required, string): The string "oob-01" type (required, string): The string "oob-01"
POST /acme/authz/1234/3 POST /acme/authz/1234/3
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/1", "kid": "https://example.com/acme/acct/1",
skipping to change at page 55, line 26 skipping to change at page 53, line 26
"type": "oob-01" "type": "oob-01"
}), }),
"signature": "Q1bURgJoEslbD1c5...3pYdSMLio57mQNN4" "signature": "Q1bURgJoEslbD1c5...3pYdSMLio57mQNN4"
} }
On receiving a response, the server MUST verify that the value of the On receiving a response, the server MUST verify that the value of the
"type" field is "oob-01". Otherwise, the steps the server takes to "type" field is "oob-01". Otherwise, the steps the server takes to
validate identifier possession are determined by the server's local validate identifier possession are determined by the server's local
policy. policy.
8. IANA Considerations 9. IANA Considerations
8.1. Well-Known URI for the HTTP Challenge 9.1. MIME Type: application/pem-certificate-chain
The "Media Types" registry should be updated with the following
additional value:
MIME media type name: application
MIME subtype name: pem-certificate-chain
Required parameters: None
Optional parameters: None
Encoding considerations: None
Security considerations: Carries a cryptographic certificate
Interoperability considerations: None
Published specification: draft-ietf-acme-acme [[ RFC EDITOR: Please
replace draft-ietf-acme-acme above with the RFC number assigned to
this ]]
Applications which use this media type: Any MIME-complaint transport
Additional information:
File should contain one or more certificates encoded as PEM according
to RFC 7468. In order to provide easy interoperation with TLS, the
first certificate MUST be an end-entity certificate. Each following
certificate SHOULD directly certify one preceding it. Because
certificate validation requires that trust anchors be distributed
independently, a certificate that specifies a trust anchor MAY be
omitted from the chain, provided that supported peers are known to
possess any omitted certificates.
9.2. Well-Known URI for the HTTP Challenge
The "Well-Known URIs" registry should be updated with the following The "Well-Known URIs" registry should be updated with the following
additional value (using the template from [RFC5785]): additional value (using the template from [RFC5785]):
URI suffix: acme-challenge URI suffix: acme-challenge
Change controller: IETF Change controller: IETF
Specification document(s): This document, Section Section 7.2 Specification document(s): This document, Section Section 8.2
Related information: N/A Related information: N/A
8.2. Replay-Nonce HTTP Header 9.3. Replay-Nonce HTTP Header
The "Message Headers" registry should be updated with the following The "Message Headers" registry should be updated with the following
additional value: additional value:
| Header Field Name | Protocol | Status | Reference | +-------------------+----------+----------+---------------+
+:------------+:------+:------+:-----------+ | Replay-Nonce | http | | Header Field Name | Protocol | Status | Reference |
standard | Section 5.5.1 | +-------------------+----------+----------+---------------+
| Replay-Nonce | http | standard | Section 6.4.1 |
+-------------------+----------+----------+---------------+
8.3. "url" JWS Header Parameter 9.4. "url" JWS Header Parameter
The "JSON Web Signature and Encryption Header Parameters" registry The "JSON Web Signature and Encryption Header Parameters" registry
should be updated with the following additional value: should be updated with the following additional value:
o Header Parameter Name: "url" o Header Parameter Name: "url"
o Header Parameter Description: URL o Header Parameter Description: URL
o Header Parameter Usage Location(s): JWE, JWS o Header Parameter Usage Location(s): JWE, JWS
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 6.3.1 of RFC XXXX
o Specification Document(s): Section 5.4.1 of RFC XXXX
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
8.4. "nonce" JWS Header Parameter 9.5. "nonce" JWS Header Parameter
The "JSON Web Signature and Encryption Header Parameters" registry The "JSON Web Signature and Encryption Header Parameters" registry
should be updated with the following additional value: should be updated with the following additional value:
o Header Parameter Name: "nonce" o Header Parameter Name: "nonce"
o Header Parameter Description: Nonce o Header Parameter Description: Nonce
o Header Parameter Usage Location(s): JWE, JWS o Header Parameter Usage Location(s): JWE, JWS
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 5.5.2 of RFC XXXX o Specification Document(s): Section 6.4.2 of RFC XXXX
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
8.5. URN Sub-namespace for ACME (urn:ietf:params:acme) 9.6. URN Sub-namespace for ACME (urn:ietf:params:acme)
The "IETF URN Sub-namespace for Registered Protocol Parameter The "IETF URN Sub-namespace for Registered Protocol Parameter
Identifiers" registry should be updated with the following additional Identifiers" registry should be updated with the following additional
value, following the template in [RFC3553]: value, following the template in [RFC3553]:
Registry name: acme Registry name: acme
Specification: RFC XXXX Specification: RFC XXXX
Repository: URL-TBD Repository: URL-TBD
skipping to change at page 57, line 4 skipping to change at page 55, line 38
The "IETF URN Sub-namespace for Registered Protocol Parameter The "IETF URN Sub-namespace for Registered Protocol Parameter
Identifiers" registry should be updated with the following additional Identifiers" registry should be updated with the following additional
value, following the template in [RFC3553]: value, following the template in [RFC3553]:
Registry name: acme Registry name: acme
Specification: RFC XXXX Specification: RFC XXXX
Repository: URL-TBD Repository: URL-TBD
Index value: No transformation needed. Index value: No transformation needed.
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document, and replace URL-TBD with the URL assigned by IANA to this document, and replace URL-TBD with the URL assigned by IANA
for registries of ACME parameters. ]] for registries of ACME parameters. ]]
8.6. New Registries 9.7. New Registries
This document requests that IANA create the following new registries: This document requests that IANA create the following new registries:
1. ACME Error Codes 1. ACME Account Object Fields (Section 9.7.1)
2. ACME Resource Types 2. ACME Order Object Fields (Section 9.7.2)
3. ACME Error Types (Section 9.7.3)
3. ACME Identifier Types 4. ACME Resource Types (Section 9.7.4)
4. ACME Challenge Types 5. ACME Identifier Types (Section 9.7.5)
All of these registries should be administered under a Specification 6. ACME Challenge Types (Section 9.7.6)
Required policy [RFC5226].
8.6.1. Fields in Account Objects All of these registries are under a heading of "Automated Certificate
Management Environment (ACME) Protocol" and are administered under a
Specification Required policy [RFC5226].
9.7.1. Fields in Account Objects
This registry lists field names that are defined for use in ACME This registry lists field names that are defined for use in ACME
account objects. Fields marked as "configurable" may be included in account objects. Fields marked as "configurable" may be included in
a new-account request. a new-account request.
Template: Template:
o Field name: The string to be used as a key in the JSON dictionary o Field name: The string to be used as a key in the JSON object
o Field type: The type of value to be provided, e.g., string, o Field type: The type of value to be provided, e.g., string,
boolean, array of string boolean, array of string
o Client configurable: Boolean indicating whether the server should o Client configurable: Boolean indicating whether the server should
accept values provided by the client accept values provided by the client
o Reference: Where this field is defined o Reference: Where this field is defined
Initial contents: The fields and descriptions defined in Initial contents: The fields and descriptions defined in
Section 6.1.2. Section 7.1.2.
+--------------------------+-------------+--------------+-----------+ +--------------------------+-------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
+--------------------------+-------------+--------------+-----------+ +--------------------------+-------------+--------------+-----------+
| key | dictionary | false | RFC XXXX | | key | object | false | RFC XXXX |
| | | | | | | | | |
| status | string | false | RFC XXXX | | status | string | false | RFC XXXX |
| | | | | | | | | |
| contact | array of | true | RFC XXXX | | contact | array of | true | RFC XXXX |
| | string | | | | | string | | |
| | | | | | | | | |
| external-account-binding | dictionary | true | RFC XXXX | | external-account-binding | object | true | RFC XXXX |
| | | | | | | | | |
| terms-of-service-agreed | boolean | false | RFC XXXX | | terms-of-service-agreed | boolean | true | RFC XXXX |
| | | | | | | | | |
| orders | array of | false | RFC XXXX | | orders | array of | false | RFC XXXX |
| | string | | | | | string | | |
+--------------------------+-------------+--------------+-----------+ +--------------------------+-------------+--------------+-----------+
8.6.2. Fields in Order Objects 9.7.2. Fields in Order Objects
This registry lists field names that are defined for use in ACME This registry lists field names that are defined for use in ACME
order objects. Fields marked as "configurable" may be included in a order objects. Fields marked as "configurable" may be included in a
new-order request. new-order request.
Template: Template:
o Field name: The string to be used as a key in the JSON dictionary o Field name: The string to be used as a key in the JSON object
o Field type: The type of value to be provided, e.g., string, o Field type: The type of value to be provided, e.g., string,
boolean, array of string boolean, array of string
o Client configurable: Boolean indicating whether the server should o Client configurable: Boolean indicating whether the server should
accept values provided by the client accept values provided by the client
o Reference: Where this field is defined o Reference: Where this field is defined
Initial contents: The fields and descriptions defined in Initial contents: The fields and descriptions defined in
Section 6.1.3. Section 7.1.3.
+----------------+-------------------+--------------+-----------+ +----------------+-----------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
+----------------+-------------------+--------------+-----------+ +----------------+-----------------+--------------+-----------+
| status | string | false | RFC XXXX | | status | string | false | RFC XXXX |
| | | | | | | | | |
| expires | string | false | RFC XXXX | | expires | string | false | RFC XXXX |
| | | | | | | | | |
| csr | string | true | RFC XXXX | | csr | string | true | RFC XXXX |
| | | | | | | | | |
| notBefore | string | true | RFC XXXX | | notBefore | string | true | RFC XXXX |
| | | | | | | | | |
| notAfter | string | true | RFC XXXX | | notAfter | string | true | RFC XXXX |
| | | | | | | | | |
| authorizations | array of string | false | RFC XXXX | | authorizations | array of string | false | RFC XXXX |
| | | | | | | | | |
| certificate | string | false | RFC XXXX | | certificate | string | false | RFC XXXX |
+----------------+-------------------+--------------+-----------+ +----------------+-----------------+--------------+-----------+
8.6.3. Error Codes 9.7.3. Error Types
This registry lists values that are used within URN values that are This registry lists values that are used within URN values that are
provided in the "type" field of problem documents in ACME. provided in the "type" field of problem documents in ACME.
Template: Template:
o Code: The label to be included in the URN for this error, o Type: The label to be included in the URN for this error,
following "urn:ietf:params:acme:" following "urn:ietf:params:acme:error:"
o Description: A human-readable description of the error o Description: A human-readable description of the error
o Reference: Where the error is defined o Reference: Where the error is defined
Initial contents: The codes and descriptions in the table in Initial contents: The types and descriptions in the table in
Section 5.7 above, with the Reference field set to point to this Section 6.6 above, with the Reference field set to point to this
specification. specification.
8.6.4. Resource Types 9.7.4. Resource Types
This registry lists the types of resources that ACME servers may list This registry lists the types of resources that ACME servers may list
in their directory objects. in their directory objects.
Template: Template:
o Key: The value to be used as a dictionary key in the directory o Key: The value to be used as a field name in the directory object
object
o Resource type: The type of resource labeled by the key o Resource type: The type of resource labeled by the key
o Reference: Where the identifier type is defined
o Reference: Where the resource type is defined
Initial contents: Initial contents:
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
| Key | Resource type | Reference | | Key | Resource type | Reference |
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
| new-account | New account | RFC XXXX | | new-account | New account | RFC XXXX |
| | | | | | | |
| new-order | New order | RFC XXXX | | new-order | New order | RFC XXXX |
| | | | | | | |
| revoke-cert | Revoke certificate | RFC XXXX | | revoke-cert | Revoke certificate | RFC XXXX |
| | | | | | | |
| key-change | Key change | RFC XXXX | | key-change | Key change | RFC XXXX |
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
8.6.5. Identifier Types 9.7.5. Identifier Types
This registry lists the types of identifiers that ACME clients may This registry lists the types of identifiers in certificates that
request authorization to issue in certificates. ACME clients may request authorization to issue.
Template: Template:
o Label: The value to be put in the "type" field of the identifier o Label: The value to be put in the "type" field of the identifier
object object
o Reference: Where the identifier type is defined o Reference: Where the identifier type is defined
Initial contents: Initial contents:
+-------+-----------+ +-------+-----------+
| Label | Reference | | Label | Reference |
+-------+-----------+ +-------+-----------+
| dns | RFC XXXX | | dns | RFC XXXX |
+-------+-----------+ +-------+-----------+
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
8.6.6. Challenge Types 9.7.6. Challenge Types
This registry lists the ways that ACME servers can offer to validate This registry lists the ways that ACME servers can offer to validate
control of an identifier. The "Identifier Type" field in template control of an identifier. The "Identifier Type" field in the
must be contained in the Label column of the ACME Identifier Types template must be contained in the Label column of the ACME Identifier
registry. Types registry.
Template: Template:
o Label: The value to be put in the "type" field of challenge o Label: The value to be put in the "type" field of challenge
objects using this validation mechanism objects using this validation mechanism
o Identifier Type: The type of identifier that this mechanism o Identifier Type: The type of identifier that this mechanism
applies to applies to
o Reference: Where the challenge type is defined o Reference: Where the challenge type is defined
skipping to change at page 61, line 30 skipping to change at page 60, line 28
| http | dns | RFC XXXX | | http | dns | RFC XXXX |
| | | | | | | |
| tls-sni | dns | RFC XXXX | | tls-sni | dns | RFC XXXX |
| | | | | | | |
| dns | dns | RFC XXXX | | dns | dns | RFC XXXX |
+---------+-----------------+-----------+ +---------+-----------------+-----------+
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
9. Security Considerations 10. Security Considerations
ACME is a protocol for managing certificates that attest to ACME is a protocol for managing certificates that attest to
identifier/key bindings. Thus the foremost security goal of ACME is identifier/key bindings. Thus the foremost security goal of ACME is
to ensure the integrity of this process, i.e., to ensure that the to ensure the integrity of this process, i.e., to ensure that the
bindings attested by certificates are correct, and that only bindings attested by certificates are correct and that only
authorized entities can manage certificates. ACME identifies clients authorized entities can manage certificates. ACME identifies clients
by their account keys, so this overall goal breaks down into two more by their account keys, so this overall goal breaks down into two more
precise goals: precise goals:
1. Only an entity that controls an identifier can get an account key 1. Only an entity that controls an identifier can get an
authorized for that identifier authorization for that identifier
2. Once authorized, an account key's authorizations cannot be 2. Once authorized, an account key's authorizations cannot be
improperly transferred to another account key improperly used by another account
In this section, we discuss the threat model that underlies ACME and In this section, we discuss the threat model that underlies ACME and
the ways that ACME achieves these security goals within that threat the ways that ACME achieves these security goals within that threat
model. We also discuss the denial-of-service risks that ACME servers model. We also discuss the denial-of-service risks that ACME servers
face, and a few other miscellaneous considerations. face, and a few other miscellaneous considerations.
9.1. Threat model 10.1. Threat model
As a service on the Internet, ACME broadly exists within the Internet As a service on the Internet, ACME broadly exists within the Internet
threat model [RFC3552]. In analyzing ACME, it is useful to think of threat model [RFC3552]. In analyzing ACME, it is useful to think of
an ACME server interacting with other Internet hosts along two an ACME server interacting with other Internet hosts along two
"channels": "channels":
o An ACME channel, over which the ACME HTTPS requests are exchanged o An ACME channel, over which the ACME HTTPS requests are exchanged
o A validation channel, over which the ACME server performs o A validation channel, over which the ACME server performs
additional requests to validate a client's control of an additional requests to validate a client's control of an
skipping to change at page 62, line 40 skipping to change at page 61, line 40
+------------+ +------------+
In practice, the risks to these channels are not entirely separate, In practice, the risks to these channels are not entirely separate,
but they are different in most cases. Each channel, for example, but they are different in most cases. Each channel, for example,
uses a different communications pattern: the ACME channel will uses a different communications pattern: the ACME channel will
comprise inbound HTTPS connections to the ACME server and the comprise inbound HTTPS connections to the ACME server and the
validation channel outbound HTTP or DNS requests. validation channel outbound HTTP or DNS requests.
Broadly speaking, ACME aims to be secure against active and passive Broadly speaking, ACME aims to be secure against active and passive
attackers on any individual channel. Some vulnerabilities arise attackers on any individual channel. Some vulnerabilities arise
(noted below), when an attacker can exploit both the ACME channel and (noted below) when an attacker can exploit both the ACME channel and
one of the others. one of the others.
On the ACME channel, in addition to network-layer attackers, we also On the ACME channel, in addition to network layer attackers, we also
need to account for application-layer man in the middle attacks, and need to account for man-in-the-middle (MitM) attacks at the
for abusive use of the protocol itself. Protection against application layer, and for abusive use of the protocol itself.
application-layer MitM addresses potential attackers such as Content Protection against application layer MitM addresses potential
Distribution Networks (CDNs) and middleboxes with a TLS MitM attackers such as Content Distribution Networks (CDNs) and
function. Preventing abusive use of ACME means ensuring that an middleboxes with a TLS MitM function. Preventing abusive use of ACME
attacker with access to the validation channel can't obtain means ensuring that an attacker with access to the validation channel
illegitimate authorization by acting as an ACME client (legitimately, can't obtain illegitimate authorization by acting as an ACME client
in terms of the protocol). (legitimately, in terms of the protocol).
9.2. Integrity of Authorizations 10.2. Integrity of Authorizations
ACME allows anyone to request challenges for an identifier by ACME allows anyone to request challenges for an identifier by
registering an account key and sending a new-order request under that registering an account key and sending a new-order request using that
account key. The integrity of the authorization process thus depends account key. The integrity of the authorization process thus depends
on the identifier validation challenges to ensure that the challenge on the identifier validation challenges to ensure that the challenge
can only be completed by someone who both (1) holds the private key can only be completed by someone who both (1) holds the private key
of the account key pair, and (2) controls the identifier in question. of the account key pair, and (2) controls the identifier in question.
Validation responses need to be bound to an account key pair in order Validation responses need to be bound to an account key pair in order
to avoid situations where an ACME MitM can switch out a legitimate to avoid situations where an ACME MitM can switch out a legitimate
domain holder's account key for one of his choosing, e.g.: domain holder's account key for one of his choosing, e.g.:
o Legitimate domain holder registers account key pair A o Legitimate domain holder registers account key pair A
o MitM registers account key pair B o MitM registers account key pair B
o Legitimate domain holder sends a new-order request signed under o Legitimate domain holder sends a new-order request signed using
account key A account key A
o MitM suppresses the legitimate request, but sends the same request o MitM suppresses the legitimate request but sends the same request
signed under account key B signed using account key B
o ACME server issues challenges and MitM forwards them to the o ACME server issues challenges and MitM forwards them to the
legitimate domain holder legitimate domain holder
o Legitimate domain holder provisions the validation response o Legitimate domain holder provisions the validation response
o ACME server performs validation query and sees the response o ACME server performs validation query and sees the response
provisioned by the legitimate domain holder provisioned by the legitimate domain holder
o Because the challenges were issued in response to a message signed o Because the challenges were issued in response to a message signed
skipping to change at page 64, line 13 skipping to change at page 63, line 13
in this document, the actions are: in this document, the actions are:
o HTTP: Provision files under .well-known on a web server for the o HTTP: Provision files under .well-known on a web server for the
domain domain
o TLS SNI: Configure a TLS server for the domain o TLS SNI: Configure a TLS server for the domain
o DNS: Provision DNS resource records for the domain o DNS: Provision DNS resource records for the domain
There are several ways that these assumptions can be violated, both There are several ways that these assumptions can be violated, both
by misconfiguration and by attack. For example, on a web server that by misconfiguration and by attacks. For example, on a web server
allows non-administrative users to write to .well-known, any user can that allows non-administrative users to write to .well-known, any
claim to own the server's hostname by responding to an HTTP user can claim to own the web server's hostname by responding to an
challenge, and likewise for TLS configuration and TLS SNI. HTTP challenge, and likewise for TLS configuration and TLS SNI.
The use of hosting providers is a particular risk for ACME The use of hosting providers is a particular risk for ACME
validation. If the owner of the domain has outsourced operation of validation. If the owner of the domain has outsourced operation of
DNS or web services to a hosting provider, there is nothing that can DNS or web services to a hosting provider, there is nothing that can
be done against tampering by the hosting provider. As far as the be done against tampering by the hosting provider. As far as the
outside world is concerned, the zone or web site provided by the outside world is concerned, the zone or website provided by the
hosting provider is the real thing. hosting provider is the real thing.
More limited forms of delegation can also lead to an unintended party More limited forms of delegation can also lead to an unintended party
gaining the ability to successfully complete a validation gaining the ability to successfully complete a validation
transaction. For example, suppose an ACME server follows HTTP transaction. For example, suppose an ACME server follows HTTP
redirects in HTTP validation and a web site operator provisions a redirects in HTTP validation and a website operator provisions a
catch-all redirect rule that redirects requests for unknown resources catch-all redirect rule that redirects requests for unknown resources
to a different domain. Then the target of the redirect could use to a different domain. Then the target of the redirect could use
that to get a certificate through HTTP validation, since the that to get a certificate through HTTP validation since the
validation path will not be known to the primary server. validation path will not be known to the primary server.
The DNS is a common point of vulnerability for all of these The DNS is a common point of vulnerability for all of these
challenges. An entity that can provision false DNS records for a challenges. An entity that can provision false DNS records for a
domain can attack the DNS challenge directly, and can provision false domain can attack the DNS challenge directly and can provision false
A/AAAA records to direct the ACME server to send its TLS SNI or HTTP A/AAAA records to direct the ACME server to send its TLS SNI or HTTP
validation query to a server of the attacker's choosing. There are a validation query to a remote server of the attacker's choosing.
few different mitigations that ACME servers can apply: There are a few different mitigations that ACME servers can apply:
o Always querying the DNS using a DNSSEC-validating resolver o Always querying the DNS using a DNSSEC-validating resolver
(enhancing security for zones that are DNSSEC-enabled) (enhancing security for zones that are DNSSEC-enabled)
o Querying the DNS from multiple vantage points to address local o Querying the DNS from multiple vantage points to address local
attackers attackers
o Applying mitigations against DNS off-path attackers, e.g., adding o Applying mitigations against DNS off-path attackers, e.g., adding
entropy to requests [I-D.vixie-dnsext-dns0x20] or only using TCP entropy to requests [I-D.vixie-dnsext-dns0x20] or only using TCP
Given these considerations, the ACME validation process makes it Given these considerations, the ACME validation process makes it
impossible for any attacker on the ACME channel, or a passive impossible for any attacker on the ACME channel or a passive attacker
attacker on the validation channel to hijack the authorization on the validation channel to hijack the authorization process to
process to authorize a key of the attacker's choice. authorize a key of the attacker's choice.
An attacker that can only see the ACME channel would need to convince An attacker that can only see the ACME channel would need to convince
the validation server to provide a response that would authorize the the validation server to provide a response that would authorize the
attacker's account key, but this is prevented by binding the attacker's account key, but this is prevented by binding the
validation response to the account key used to request challenges. A validation response to the account key used to request challenges. A
passive attacker on the validation channel can observe the correct passive attacker on the validation channel can observe the correct
validation response and even replay it, but that response can only be validation response and even replay it, but that response can only be
used with the account key for which it was generated. used with the account key for which it was generated.
An active attacker on the validation channel can subvert the ACME An active attacker on the validation channel can subvert the ACME
process, by performing normal ACME transactions and providing a process, by performing normal ACME transactions and providing a
validation response for his own account key. The risks due to validation response for his own account key. The risks due to
hosting providers noted above are a particular case. For identifiers hosting providers noted above are a particular case.
where the server already has some public key associated with the
domain this attack can be prevented by requiring the client to prove
control of the corresponding private key.
9.3. Denial-of-Service Considerations It is RECOMMENDED that the server perform DNS queries and make HTTP
and TLS connections from various network perspectives, in order to
make MitM attacks harder.
10.3. Denial-of-Service Considerations
As a protocol run over HTTPS, standard considerations for TCP-based As a protocol run over HTTPS, standard considerations for TCP-based
and HTTP-based DoS mitigation also apply to ACME. and HTTP-based DoS mitigation also apply to ACME.
At the application layer, ACME requires the server to perform a few At the application layer, ACME requires the server to perform a few
potentially expensive operations. Identifier validation transactions potentially expensive operations. Identifier validation transactions
require the ACME server to make outbound connections to potentially require the ACME server to make outbound connections to potentially
attacker-controlled servers, and certificate issuance can require attacker-controlled servers, and certificate issuance can require
interactions with cryptographic hardware. interactions with cryptographic hardware.
In addition, an attacker can also cause the ACME server to send In addition, an attacker can also cause the ACME server to send
validation requests to a domain of its choosing by submitting validation requests to a domain of its choosing by submitting
authorization requests for the victim domain. authorization requests for the victim domain.
All of these attacks can be mitigated by the application of All of these attacks can be mitigated by the application of
appropriate rate limits. Issues closer to the front end, like POST appropriate rate limits. Issues closer to the front end, like POST
body validation, can be addressed using HTTP request limiting. For body validation, can be addressed using HTTP request limiting. For
validation and certificate requests, there are other identifiers on validation and certificate requests, there are other identifiers on
which rate limits can be keyed. For example, the server might limit which rate limits can be keyed. For example, the server might limit
the rate at which any individual account key can issue certificates, the rate at which any individual account key can issue certificates
or the rate at which validation can be requested within a given or the rate at which validation can be requested within a given
subtree of the DNS. subtree of the DNS. And in order to prevent attackers from
circumventing these limits simply by minting new accounts, servers
would need to limit the rate at which accounts can be registered.
9.4. Server-Side Request Forgery 10.4. Server-Side Request Forgery
Server-Side Request Forgery (SSRF) attacks can arise when an attacker Server-Side Request Forgery (SSRF) attacks can arise when an attacker
can cause a server to perform HTTP requests to an attacker-chosen can cause a server to perform HTTP requests to an attacker-chosen
URL. In the ACME HTTP challenge validation process, the ACME server URL. In the ACME HTTP challenge validation process, the ACME server
performs an HTTP GET request to a URL in which the attacker can performs an HTTP GET request to a URL in which the attacker can
choose the domain. This request is made before the server has choose the domain. This request is made before the server has
verified that the client controls the domain, so any client can cause verified that the client controls the domain, so any client can cause
a query to any domain. a query to any domain.
Some server implementations include information from the validation Some server implementations include information from the validation
skipping to change at page 66, line 28 skipping to change at page 65, line 34
they control, then they can send the server an HTTP redirect (e.g., a they control, then they can send the server an HTTP redirect (e.g., a
302 response) which will cause the server to query an arbitrary URI. 302 response) which will cause the server to query an arbitrary URI.
In order to further limit the SSRF risk, ACME server operators should In order to further limit the SSRF risk, ACME server operators should
ensure that validation queries can only be sent to servers on the ensure that validation queries can only be sent to servers on the
public Internet, and not, say, web services within the server public Internet, and not, say, web services within the server
operator's internal network. Since the attacker could make requests operator's internal network. Since the attacker could make requests
to these public servers himself, he can't gain anything extra through to these public servers himself, he can't gain anything extra through
an SSRF attack on ACME aside from a layer of anonymization. an SSRF attack on ACME aside from a layer of anonymization.
9.5. CA Policy Considerations 10.5. CA Policy Considerations
The controls on issuance enabled by ACME are focused on validating The controls on issuance enabled by ACME are focused on validating
that a certificate applicant controls the identifier he claims. that a certificate applicant controls the identifier he claims.
Before issuing a certificate, however, there are many other checks Before issuing a certificate, however, there are many other checks
that a CA might need to perform, for example: that a CA might need to perform, for example:
o Has the client agreed to a subscriber agreement? o Has the client agreed to a subscriber agreement?
o Is the claimed identifier syntactically valid? o Is the claimed identifier syntactically valid?
skipping to change at page 67, line 15 skipping to change at page 66, line 19
CAs that use ACME to automate issuance will need to ensure that their CAs that use ACME to automate issuance will need to ensure that their
servers perform all necessary checks before issuing. servers perform all necessary checks before issuing.
CAs using ACME to allow clients to agree to terms of service should CAs using ACME to allow clients to agree to terms of service should
keep in mind that ACME clients can automate this agreement, possibly keep in mind that ACME clients can automate this agreement, possibly
not involving a human user. If a CA wishes to have stronger evidence not involving a human user. If a CA wishes to have stronger evidence
of user consent, it may present an out-of-band requirement or of user consent, it may present an out-of-band requirement or
challenge to require human involvement. challenge to require human involvement.
10. Operational Considerations 11. Operational Considerations
There are certain factors that arise in operational reality that There are certain factors that arise in operational reality that
operators of ACME-based CAs will need to keep in mind when operators of ACME-based CAs will need to keep in mind when
configuring their services. For example: configuring their services. For example:
10.1. DNS over TCP 11.1. DNS security
As noted above, DNS forgery attacks against the ACME server can As noted above, DNS forgery attacks against the ACME server can
result in the server making incorrect decisions about domain control result in the server making incorrect decisions about domain control
and thus mis-issuing certificates. Servers SHOULD verify DNSSEC when and thus mis-issuing certificates. Servers SHOULD perform DNS
it is available for a domain. When DNSSEC is not available, servers queries over TCP, which provides better resistance to some forgery
SHOULD perform DNS queries over TCP, which provides better resistance attacks than DNS over UDP.
to some forgery attacks than DNS over UDP.
10.2. Default Virtual Hosts An ACME-based CA will often need to make DNS queries, e.g., to
validate control of DNS names. Because the security of such
validations ultimately depends on the authenticity of DNS data, every
possible precaution should be taken to secure DNS queries done by the
CA. It is therefore RECOMMENDED that ACME-based CAs make all DNS
queries via DNSSEC-validating stub or recursive resolvers. This
provides additional protection to domains which choose to make use of
DNSSEC.
An ACME-based CA must use only a resolver if it trusts the resolver
and every component of the network route by which it is accessed. It
is therefore RECOMMENDED that ACME-based CAs operate their own
DNSSEC-validating resolvers within their trusted network and use
these resolvers both for both CAA record lookups and all record
lookups in furtherance of a challenge scheme (A, AAAA, TXT, etc.).
11.2. Default Virtual Hosts
In many cases, TLS-based services are deployed on hosted platforms In many cases, TLS-based services are deployed on hosted platforms
that use the Server Name Indication (SNI) TLS extension to that use the Server Name Indication (SNI) TLS extension to
distinguish between different hosted services or "virtual hosts". distinguish between different hosted services or "virtual hosts".
When a client initiates a TLS connection with an SNI value indicating When a client initiates a TLS connection with an SNI value indicating
a provisioned host, the hosting platform routes the connection to a provisioned host, the hosting platform routes the connection to
that host. that host.
When a connection comes in with an unknown SNI value, one might When a connection comes in with an unknown SNI value, one might
expect the hosting platform to terminate the TLS connection. expect the hosting platform to terminate the TLS connection.
skipping to change at page 68, line 8 skipping to change at page 67, line 29
In such cases, the owner of the default virtual host can complete a In such cases, the owner of the default virtual host can complete a
TLS-based challenge (e.g., "tls-sni-02") for any domain with an A TLS-based challenge (e.g., "tls-sni-02") for any domain with an A
record that points to the hosting platform. This could result in record that points to the hosting platform. This could result in
mis-issuance in cases where there are multiple hosts with different mis-issuance in cases where there are multiple hosts with different
owners resident on the hosting platform. owners resident on the hosting platform.
A CA that accepts TLS-based proof of domain control should attempt to A CA that accepts TLS-based proof of domain control should attempt to
check whether a domain is hosted on a domain with a default virtual check whether a domain is hosted on a domain with a default virtual
host before allowing an authorization request for this host to use a host before allowing an authorization request for this host to use a
TLS-based challenge. A default virtual host can be detected by TLS-based challenge. Typically, systems with default virtual hosts
initiating TLS connections to the host with random SNI values within do not allow the holder of the default virtual host to control what
the namespace used for the TLS-based challenge (the "acme.invalid" certificates are presented on a request-by-request basis. Rather,
namespace for "tls-sni-02"). the default virtual host can configure which certificate is presented
in TLS on a fairly static basis, so that the certificate presented
10.3. Use of DNSSEC Resolvers should be stable over small intervals.
An ACME-based CA will often need to make DNS queries, e.g., to
validate control of DNS names. Because the security of such
validations ultimately depends on the authenticity of DNS data, every
possible precaution should be taken to secure DNS queries done by the
CA. It is therefore RECOMMENDED that ACME-based CAs make all DNS
queries via DNSSEC-validating stub or recursive resolvers. This
provides additional protection to domains which choose to make use of
DNSSEC.
An ACME-based CA must use only a resolver if it trusts the resolver A CA can detect such a bounded default vhost by initiating TLS
and every component of the network route by which it is accessed. It connections to the host with random SNI values within the namespace
is therefore RECOMMENDED that ACME-based CAs operate their own used for the TLS-based challenge (the "acme.invalid" namespace for
DNSSEC-validating resolvers within their trusted network and use "tls-sni-02"). If it receives the same certificate on two different
these resolvers both for both CAA record lookups and all record connections, then it is very likely that the server is in a default
lookups in furtherance of a challenge scheme (A, AAAA, TXT, etc.). virtual host configuration. Conversely, if the TLS server returns an
unrecognized_name alert, then this is an indication that the server
is not in a default virtual host configuration.
11. Acknowledgements 12. Acknowledgements
In addition to the editors listed on the front page, this document In addition to the editors listed on the front page, this document
has benefited from contributions from a broad set of contributors, has benefited from contributions from a broad set of contributors,
all the way back to its inception. all the way back to its inception.
o Peter Eckersley, EFF o Peter Eckersley, EFF
o Eric Rescorla, Mozilla o Eric Rescorla, Mozilla
o Seth Schoen, EFF o Seth Schoen, EFF
o Alex Halderman, University of Michigan o Alex Halderman, University of Michigan
o Martin Thomson, Mozilla o Martin Thomson, Mozilla
o Jakub Warmuz, University of Oxford o Jakub Warmuz, University of Oxford
skipping to change at page 69, line 5 skipping to change at page 68, line 18
o Alex Halderman, University of Michigan o Alex Halderman, University of Michigan
o Martin Thomson, Mozilla o Martin Thomson, Mozilla
o Jakub Warmuz, University of Oxford o Jakub Warmuz, University of Oxford
This document draws on many concepts established by Eric Rescorla's This document draws on many concepts established by Eric Rescorla's
"Automated Certificate Issuance Protocol" draft. Martin Thomson "Automated Certificate Issuance Protocol" draft. Martin Thomson
provided helpful guidance in the use of HTTP. provided helpful guidance in the use of HTTP.
12. References 13. References
12.1. Normative References 13.1. Normative References
[FIPS180-4]
Department of Commerce, National., "NIST FIPS 180-4,
Secure Hash Standard", March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2585] Housley, R. and P. Hoffman, "Internet X.509 Public Key
Infrastructure Operational Protocols: FTP and HTTP",
RFC 2585, DOI 10.17487/RFC2585, May 1999,
<http://www.rfc-editor.org/info/rfc2585>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>. <http://www.rfc-editor.org/info/rfc2818>.
[RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object [RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
Classes and Attribute Types Version 2.0", RFC 2985, Classes and Attribute Types Version 2.0", RFC 2985,
DOI 10.17487/RFC2985, November 2000, DOI 10.17487/RFC2985, November 2000,
<http://www.rfc-editor.org/info/rfc2985>. <http://www.rfc-editor.org/info/rfc2985>.
[RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification [RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
skipping to change at page 69, line 37 skipping to change at page 69, line 14
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<http://www.rfc-editor.org/info/rfc3339>. <http://www.rfc-editor.org/info/rfc3339>.
[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, DOI 10.17487/RFC3492, March 2003, (IDNA)", RFC 3492, DOI 10.17487/RFC3492, March 2003,
<http://www.rfc-editor.org/info/rfc3492>. <http://www.rfc-editor.org/info/rfc3492>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>. <http://www.rfc-editor.org/info/rfc3986>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>. <http://www.rfc-editor.org/info/rfc4648>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>. <http://www.rfc-editor.org/info/rfc5280>.
skipping to change at page 70, line 44 skipping to change at page 70, line 29
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>. 2014, <http://www.rfc-editor.org/info/rfc7159>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>. <http://www.rfc-editor.org/info/rfc7231>.
[RFC7468] Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
April 2015, <http://www.rfc-editor.org/info/rfc7468>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>. 2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015, DOI 10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>. <http://www.rfc-editor.org/info/rfc7518>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK) [RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <http://www.rfc-editor.org/info/rfc7638>. 2015, <http://www.rfc-editor.org/info/rfc7638>.
[RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016, APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016,
<http://www.rfc-editor.org/info/rfc7807>. <http://www.rfc-editor.org/info/rfc7807>.
12.2. Informative References 13.2. Informative References
[I-D.vixie-dnsext-dns0x20] [I-D.vixie-dnsext-dns0x20]
Vixie, P. and D. Dagon, "Use of Bit 0x20 in DNS Labels to Vixie, P. and D. Dagon, "Use of Bit 0x20 in DNS Labels to
Improve Transaction Identity", draft-vixie-dnsext- Improve Transaction Identity", draft-vixie-dnsext-
dns0x20-00 (work in progress), March 2008. dns0x20-00 (work in progress), March 2008.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003, DOI 10.17487/RFC3552, July 2003,
<http://www.rfc-editor.org/info/rfc3552>. <http://www.rfc-editor.org/info/rfc3552>.
[RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
IETF URN Sub-namespace for Registered Protocol IETF URN Sub-namespace for Registered Protocol
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
2003, <http://www.rfc-editor.org/info/rfc3553>. 2003, <http://www.rfc-editor.org/info/rfc3553>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785, Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010, DOI 10.17487/RFC5785, April 2010,
<http://www.rfc-editor.org/info/rfc5785>. <http://www.rfc-editor.org/info/rfc5785>.
[RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate
Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
<http://www.rfc-editor.org/info/rfc6962>.
[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
2015, <http://www.rfc-editor.org/info/rfc7469>.
[W3C.CR-cors-20130129] [W3C.CR-cors-20130129]
Kesteren, A., "Cross-Origin Resource Sharing", World Wide Kesteren, A., "Cross-Origin Resource Sharing", World Wide
Web Consortium CR CR-cors-20130129, January 2013, Web Consortium CR CR-cors-20130129, January 2013,
<http://www.w3.org/TR/2013/CR-cors-20130129>. <http://www.w3.org/TR/2013/CR-cors-20130129>.
Authors' Addresses Authors' Addresses
Richard Barnes Richard Barnes
Mozilla Mozilla
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