draft-ietf-acme-acme-06.txt   draft-ietf-acme-acme-07.txt 
ACME Working Group R. Barnes ACME Working Group R. Barnes
Internet-Draft Mozilla Internet-Draft Cisco
Intended status: Standards Track J. Hoffman-Andrews Intended status: Standards Track J. Hoffman-Andrews
Expires: September 14, 2017 EFF Expires: December 23, 2017 EFF
J. Kasten J. Kasten
University of Michigan University of Michigan
March 13, 2017 June 21, 2017
Automatic Certificate Management Environment (ACME) Automatic Certificate Management Environment (ACME)
draft-ietf-acme-acme-06 draft-ietf-acme-acme-07
Abstract Abstract
Certificates in PKI using X.509 (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 certification authority (CA) and document describes a protocol that a certification authority (CA) and
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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 September 14, 2017. This Internet-Draft will expire on December 23, 2017.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
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. Character Encoding . . . . . . . . . . . . . . . . . . . . . 8 5. Character Encoding . . . . . . . . . . . . . . . . . . . . . 8
6. Message Transport . . . . . . . . . . . . . . . . . . . . . . 8 6. Message Transport . . . . . . . . . . . . . . . . . . . . . . 8
6.1. HTTPS Requests . . . . . . . . . . . . . . . . . . . . . 9 6.1. HTTPS Requests . . . . . . . . . . . . . . . . . . . . . 9
6.2. Request Authentication . . . . . . . . . . . . . . . . . 9 6.2. Request Authentication . . . . . . . . . . . . . . . . . 9
6.3. Request URI Integrity . . . . . . . . . . . . . . . . . . 10 6.3. Request URL Integrity . . . . . . . . . . . . . . . . . . 10
6.3.1. "url" (URL) JWS header parameter . . . . . . . . . . 11 6.3.1. "url" (URL) JWS header parameter . . . . . . . . . . 11
6.4. Replay protection . . . . . . . . . . . . . . . . . . . . 11 6.4. Replay protection . . . . . . . . . . . . . . . . . . . . 11
6.4.1. Replay-Nonce . . . . . . . . . . . . . . . . . . . . 12 6.4.1. Replay-Nonce . . . . . . . . . . . . . . . . . . . . 12
6.4.2. "nonce" (Nonce) JWS header parameter . . . . . . . . 12 6.4.2. "nonce" (Nonce) JWS header parameter . . . . . . . . 12
6.5. Rate limits . . . . . . . . . . . . . . . . . . . . . . . 13 6.5. Rate limits . . . . . . . . . . . . . . . . . . . . . . . 13
6.6. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.6. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Certificate Management . . . . . . . . . . . . . . . . . . . 15 7. Certificate Management . . . . . . . . . . . . . . . . . . . 15
7.1. Resources . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. Resources . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1.1. Directory . . . . . . . . . . . . . . . . . . . . . . 17 7.1.1. Directory . . . . . . . . . . . . . . . . . . . . . . 17
7.1.2. Account Objects . . . . . . . . . . . . . . . . . . . 19 7.1.2. Account Objects . . . . . . . . . . . . . . . . . . . 19
7.1.3. Order Objects . . . . . . . . . . . . . . . . . . . . 20 7.1.3. Order Objects . . . . . . . . . . . . . . . . . . . . 20
7.1.4. Authorization Objects . . . . . . . . . . . . . . . . 22 7.1.4. Authorization Objects . . . . . . . . . . . . . . . . 21
7.2. Getting a Nonce . . . . . . . . . . . . . . . . . . . . . 23 7.2. Getting a Nonce . . . . . . . . . . . . . . . . . . . . . 23
7.3. Account Creation . . . . . . . . . . . . . . . . . . . . 24 7.3. Account Creation . . . . . . . . . . . . . . . . . . . . 24
7.3.1. Changes of Terms of Service . . . . . . . . . . . . . 26 7.3.1. Finding an Account URL Given a Key . . . . . . . . . 26
7.3.2. External Account Binding . . . . . . . . . . . . . . 27 7.3.2. Account Update . . . . . . . . . . . . . . . . . . . 26
7.3.3. Account Key Roll-over . . . . . . . . . . . . . . . . 29 7.3.3. Account Information . . . . . . . . . . . . . . . . . 27
7.3.4. Account deactivation . . . . . . . . . . . . . . . . 31 7.3.4. Changes of Terms of Service . . . . . . . . . . . . . 27
7.4. Applying for Certificate Issuance . . . . . . . . . . . . 32 7.3.5. External Account Binding . . . . . . . . . . . . . . 27
7.4.1. Pre-Authorization . . . . . . . . . . . . . . . . . . 34 7.3.6. Account Key Roll-over . . . . . . . . . . . . . . . . 30
7.4.2. Downloading the Certificate . . . . . . . . . . . . . 36 7.3.7. Account Deactivation . . . . . . . . . . . . . . . . 32
7.5. Identifier Authorization . . . . . . . . . . . . . . . . 37 7.4. Applying for Certificate Issuance . . . . . . . . . . . . 33
7.5.1. Responding to Challenges . . . . . . . . . . . . . . 38 7.4.1. Pre-Authorization . . . . . . . . . . . . . . . . . . 36
7.5.2. Deactivating an Authorization . . . . . . . . . . . . 40 7.4.2. Downloading the Certificate . . . . . . . . . . . . . 38
7.6. Certificate Revocation . . . . . . . . . . . . . . . . . 41 7.5. Identifier Authorization . . . . . . . . . . . . . . . . 39
8. Identifier Validation Challenges . . . . . . . . . . . . . . 43 7.5.1. Responding to Challenges . . . . . . . . . . . . . . 40
8.1. Key Authorizations . . . . . . . . . . . . . . . . . . . 45 7.5.2. Deactivating an Authorization . . . . . . . . . . . . 42
8.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.6. Certificate Revocation . . . . . . . . . . . . . . . . . 43
8.3. TLS with Server Name Indication (TLS SNI) . . . . . . . . 48 8. Identifier Validation Challenges . . . . . . . . . . . . . . 45
8.4. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 8.1. Key Authorizations . . . . . . . . . . . . . . . . . . . 47
8.5. Out-of-Band . . . . . . . . . . . . . . . . . . . . . . . 52 8.2. Retrying Challenges . . . . . . . . . . . . . . . . . . . 47
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 53 8.3. HTTP Challenge . . . . . . . . . . . . . . . . . . . . . 48
9.1. MIME Type: application/pem-certificate-chain . . . . . . 53 8.4. TLS with Server Name Indication (TLS SNI) Challenge . . . 50
9.2. Well-Known URI for the HTTP Challenge . . . . . . . . . . 54 8.5. DNS Challenge . . . . . . . . . . . . . . . . . . . . . . 52
9.3. Replay-Nonce HTTP Header . . . . . . . . . . . . . . . . 54 8.6. Out-of-Band Challenge . . . . . . . . . . . . . . . . . . 54
9.4. "url" JWS Header Parameter . . . . . . . . . . . . . . . 54 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55
9.5. "nonce" JWS Header Parameter . . . . . . . . . . . . . . 55 9.1. MIME Type: application/pem-certificate-chain . . . . . . 55
9.6. URN Sub-namespace for ACME (urn:ietf:params:acme) . . . . 55 9.2. Well-Known URI for the HTTP Challenge . . . . . . . . . . 56
9.7. New Registries . . . . . . . . . . . . . . . . . . . . . 55 9.3. Replay-Nonce HTTP Header . . . . . . . . . . . . . . . . 56
9.7.1. Fields in Account Objects . . . . . . . . . . . . . . 56 9.4. "url" JWS Header Parameter . . . . . . . . . . . . . . . 56
9.7.2. Fields in Order Objects . . . . . . . . . . . . . . . 57 9.5. "nonce" JWS Header Parameter . . . . . . . . . . . . . . 57
9.7.3. Error Types . . . . . . . . . . . . . . . . . . . . . 58 9.6. URN Sub-namespace for ACME (urn:ietf:params:acme) . . . . 57
9.7.4. Resource Types . . . . . . . . . . . . . . . . . . . 58 9.7. New Registries . . . . . . . . . . . . . . . . . . . . . 57
9.7.5. Identifier Types . . . . . . . . . . . . . . . . . . 59 9.7.1. Fields in Account Objects . . . . . . . . . . . . . . 58
9.7.6. Challenge Types . . . . . . . . . . . . . . . . . . . 59 9.7.2. Fields in Order Objects . . . . . . . . . . . . . . . 59
10. Security Considerations . . . . . . . . . . . . . . . . . . . 60 9.7.3. Error Types . . . . . . . . . . . . . . . . . . . . . 60
10.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 61 9.7.4. Resource Types . . . . . . . . . . . . . . . . . . . 60
10.2. Integrity of Authorizations . . . . . . . . . . . . . . 62 9.7.5. Identifier Types . . . . . . . . . . . . . . . . . . 61
10.3. Denial-of-Service Considerations . . . . . . . . . . . . 64 9.7.6. Challenge Types . . . . . . . . . . . . . . . . . . . 61
10.4. Server-Side Request Forgery . . . . . . . . . . . . . . 65 10. Security Considerations . . . . . . . . . . . . . . . . . . . 62
10.5. CA Policy Considerations . . . . . . . . . . . . . . . . 65 10.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 63
11. Operational Considerations . . . . . . . . . . . . . . . . . 66 10.2. Integrity of Authorizations . . . . . . . . . . . . . . 64
11.1. DNS security . . . . . . . . . . . . . . . . . . . . . . 66 10.3. Denial-of-Service Considerations . . . . . . . . . . . . 66
11.2. Default Virtual Hosts . . . . . . . . . . . . . . . . . 67 10.4. Server-Side Request Forgery . . . . . . . . . . . . . . 67
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 67 10.5. CA Policy Considerations . . . . . . . . . . . . . . . . 67
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 68 11. Operational Considerations . . . . . . . . . . . . . . . . . 68
13.1. Normative References . . . . . . . . . . . . . . . . . . 68 11.1. DNS security . . . . . . . . . . . . . . . . . . . . . . 68
13.2. Informative References . . . . . . . . . . . . . . . . . 70 11.2. Default Virtual Hosts . . . . . . . . . . . . . . . . . 69
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 71 11.3. Token Entropy . . . . . . . . . . . . . . . . . . . . . 69
11.4. Malformed Certificate Chains . . . . . . . . . . . . . . 70
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 70
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 71
13.1. Normative References . . . . . . . . . . . . . . . . . . 71
13.2. Informative References . . . . . . . . . . . . . . . . . 73
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 74
1. Introduction 1. Introduction
Certificates [RFC5280] in the Web PKI 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
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o Prove ownership of the domain by one of the following methods: o Prove ownership of the domain by one of the following methods:
* Put a CA-provided challenge at a specific place on the web * Put a CA-provided challenge at a specific place on the web
server. server.
* Put a CA-provided challenge at a DNS location corresponding to * Put a CA-provided challenge at a DNS location corresponding to
the target domain. the target domain.
* Receive CA challenge at a (hopefully) administrator-controlled * Receive CA challenge at a (hopefully) administrator-controlled
e-mail address corresponding to the domain and then respond to email address corresponding to the domain and then respond to
it on the CA's web page. it on the CA's web page.
o Download the issued certificate and install it on their Web o Download the issued certificate and install it on their Web
Server. Server.
With the exception of the CSR itself and the certificates that are With the exception of the CSR itself and the certificates that are
issued, these are all completely ad hoc procedures and are issued, these are all completely ad hoc procedures and are
accomplished by getting the human user to follow interactive natural- accomplished by getting the human user to follow interactive natural-
language instructions from the CA rather than by machine-implemented language instructions from the CA rather than by machine-implemented
published protocols. In many cases, the instructions are difficult published protocols. In many cases, the instructions are difficult
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case, the lack of published, standardized mechanisms presents an case, the lack of published, standardized mechanisms presents an
obstacle to the wide deployment of HTTPS and other PKIX-dependent obstacle to the wide deployment of HTTPS and other PKIX-dependent
systems because it inhibits mechanization of tasks related to systems because it inhibits mechanization of tasks related to
certificate issuance, deployment, and revocation. certificate issuance, deployment, and revocation.
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 Transport Layer Security (TLS) [RFC5246].
2. Deployment Model and Operator Experience 2. Deployment Model and Operator Experience
The guiding use case for ACME is obtaining certificates for websites 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 web server actually speaks issuance is intended to verify that this web server actually speaks
for 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 certificate issuer 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.
Prior to ACME, when deploying an HTTPS server, an operator typically Prior to ACME, when deploying an HTTPS server, an operator typically
gets a prompt to generate a self-signed certificate. If the operator gets a prompt to generate a self-signed certificate. If the operator
were instead deploying an ACME-compatible web server, the experience were instead deploying an HTTPS server using ACME, 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 it issue a certificate for the intended domain name(s). that it issue a certificate for the intended domain name(s).
o The CA verifies that the client controls the requested 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 email, 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 web server functional and its credentials up- required to keep the web server functional and its credentials up-
to-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
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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 may run on a web
runs on a web server, mail server, or some other server system which server, mail server, or some other server system which requires valid
requires valid TLS certificates. The ACME server runs at a TLS certificates. Or, it may run on a separate server that does not
certification authority, and responds to client requests, performing consume the certificate, but is authorized to respond to a CA-
the requested actions if the client is authorized. provided challenge. The ACME server runs at a certification
authority, and responds to client requests, performing 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
a set of JSON messages carried over HTTPS. In many ways, ACME a set of JavaScript Object Notation (JSON) messages carried over
functions much like a traditional CA, in which a user creates an HTTPS. In many ways, ACME functions much like a traditional CA, in
account, requests a certificate, and proves control of the domains in which a user creates an account, requests a certificate, and proves
that certificate in order for the CA to sign the requested control of the domains in that certificate in order for the CA to
certificate. sign the requested certificate.
The first phase of ACME is for the client to request an account with The first phase of ACME is for the client to request an account with
the ACME server. The client generates an asymmetric key pair and the ACME server. The client generates an asymmetric key pair and
requests a new account, optionally providing contact information, requests a new account, optionally providing contact information,
agreeing to terms of service, and/or associating the account with an agreeing to terms of service, and/or associating the account with an
existing account in another system. The creation request is signed existing account in another system. The creation request is signed
with the generated private key to prove that the client controls it. with the generated private key to prove that the client controls it.
Client Server Client Server
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client must satisfy before the certificate will be issued. client must satisfy before the certificate will be issued.
For example, in most cases, the server will require the client to For example, in most cases, the server will require the client to
demonstrate that it controls the identifiers in the requested demonstrate that it controls the identifiers in the requested
certificate. Because there are many different ways to validate certificate. Because there are many different ways to validate
possession of different types of identifiers, the server will choose possession of different types of identifiers, the server will choose
from an extensible set of challenges that are appropriate for the from an extensible set of challenges that are appropriate for the
identifier being claimed. The client responds with a set of identifier being claimed. The client responds with a set of
responses that tell the server which challenges the client has responses that tell the server which challenges the client has
completed. The server then validates the challenges to check that completed. The server then validates the challenges to check that
the client has accomplished the challenge. the client has accomplished them.
Once the validation process is complete and the server is satisfied Once the validation process is complete and the server is satisfied
that the client has met its requirements, the server will issue the that the client has met its requirements, the server will issue the
requested certificate and make it available to the client. requested certificate and make it available to the client.
Order Order
Signature -------> Signature ------->
Required Required
<------- Authorizations <------- Authorizations
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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 8 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. Character Encoding 5. Character Encoding
All requests and responses sent via HTTP by ACME clients, ACME All requests and responses sent via HTTP by ACME clients, ACME
servers, and validation servers as well as any inputs for digest servers, and validation servers as well as any inputs for digest
computations MUST be encoded using the UTF-8 [RFC3629] character set. computations MUST be encoded using the UTF-8 [RFC3629] character set.
6. Message Transport 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 URL.
6.1. 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. Each subsection of [RFC2818][RFC7159]. Use of HTTPS is REQUIRED. Each subsection of
Section 7 below describes the message formats used by the function Section 7 below describes the message formats used by the function
and the order in which messages are sent. 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
skipping to change at page 9, line 49 skipping to change at page 9, line 49
payload in a JSON Web Signature (JWS) [RFC7515] object, signed using payload in a JSON Web Signature (JWS) [RFC7515] object, signed using
the account's private key unless otherwise specified. The server the account's private key unless otherwise specified. The server
MUST verify the JWS before processing the request. Encapsulating MUST verify the JWS before processing the request. Encapsulating
request bodies in JWS provides 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 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 Message Authentication Code (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" (Algorithm)
* "jwk" (only for requests to new-account and revoke-cert * "jwk" (JSON Web Key, only for requests to new-account and
resources) revoke-cert resources)
* "kid" (for all other requests). * "kid" (Key ID, for all other requests)
* "nonce" (defined below) * "nonce" (defined in Section 6.4 below)
* "url" (defined below) * "url" (defined in Section 6.3 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-account requests, and for revoke-cert requests authenticated For new-account requests, and for revoke-cert requests authenticated
by 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-account contain the account URL received by POSTing to the new-account
resource. 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. Account requests for resources that might be considered sensitive. Account
resources are the only sensitive resources defined in this resources are the only sensitive resources defined in this
specification. 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.
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. that the content is readable.
6.3. Request URI Integrity 6.3. Request URL 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 URL and headers.
ACME uses JWS to provide an integrity mechanism, which protects ACME uses JWS to provide an integrity mechanism, which protects
against an intermediary changing the request URI to another ACME URI. against an intermediary changing the request URL to another ACME URL.
As noted above, all ACME request objects carry a "url" parameter in As noted in Section 6.2 above, all ACME request objects carry a "url"
their protected header. This header parameter encodes the URL to header parameter in their protected header. This header parameter
which the client is directing the request. On receiving such an encodes the URL to which the client is directing the request. On
object in an HTTP request, the server MUST compare the "url" receiving such an object in an HTTP request, the server MUST compare
parameter to the request URI. If the two do not match, then the the "url" header parameter to the request URL. If the two do not
server MUST reject the request as unauthorized. match, then the server MUST reject the request as unauthorized.
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" header parameter to the exact string
the server (rather than performing any re-encoding on the URL). The provided by the server (rather than performing any re-encoding on the
server SHOULD perform the corresponding string equality check, URL). The server SHOULD perform the corresponding string equality
configuring each resource with the URL string provided to clients and check, configuring each resource with the URL string provided to
having the resource check that requests have the same string in their clients and having the resource check that requests have the same
"url" fields. string in their "url" header parameter.
6.3.1. "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" header parameter MUST be carried
protected header of the JWS. The value of the "url" header MUST be a in the protected header of the JWS. The value of the "url" header
string representing the URL. parameter MUST be a string representing the URL.
6.4. 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 in Section 6.4.1 below. The server MUST
Nonce header field in every successful response to a POST request and include a Replay-Nonce header field in every successful response to a
SHOULD provide it in error responses as well. POST request and 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 in
As part of JWS verification, the ACME server MUST verify that the Section 6.4.2 below. As part of JWS verification, the ACME server
value of the "nonce" header is a value that the server previously MUST verify that the value of the "nonce" header is a value that the
provided in a Replay-Nonce header field. Once a nonce value has server previously provided in a Replay-Nonce header field. Once a
appeared in an ACME request, the server MUST consider it invalid, in nonce value has appeared in an ACME request, the server MUST consider
the same way as a value it had never issued. it invalid, in 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 type (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 type 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.
6.4.1. 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 MUST 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. For instance, it is acceptable to generate Replay-
Nonces randomly.
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
skipping to change at page 13, line 24 skipping to change at page 13, line 24
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 "urn:ietf:params:acme:documentation" relation. using the "urn:ietf:params:acme:documentation" relation.
6.6. Errors 6.6. Errors
Errors can be reported in ACME both at the HTTP layer and within Errors can be reported in ACME both at the HTTP layer and within
challenge objects as defined in {{identifier-validation-challenges}. challenge objects as defined in Section 8. ACME servers can return
ACME servers can return responses with an HTTP error response code responses with an HTTP error response code (4XX or 5XX). For
(4XX or 5XX). For example: If the client submits a request using a example: If the client submits a request using a method not allowed
method not allowed in this document, then the server MAY return in this document, then the server MAY return status code 405 (Method
status code 405 (Method Not Allowed). 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 a 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):
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
| Type | 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 |
| | | | | |
| invalidContact | The contact URI for an account was | | invalidContact | A contact URL for an account was invalid |
| | invalid | | | |
| unsupportedContact | A contact URL for an account used an |
| | unsupported protocol scheme |
| | |
| accountDoesNotExist | The request specified an account that |
| | does not exist |
| | | | | |
| 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 |
| | | | | |
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| | | | | |
| unsupportedIdentifier | Identifier is not supported, but may be | | unsupportedIdentifier | Identifier is not supported, but may be |
| | in future | | | in future |
| | | | | |
| userActionRequired | Visit the "instance" URL and take actions | | userActionRequired | Visit the "instance" URL and take actions |
| | specified there | | | specified there |
| | | | | |
| badRevocationReason | The revocation reason provided is not | | badRevocationReason | The revocation reason provided is not |
| | allowed by the server | | | allowed by the server |
| | | | | |
| caa | CAA records forbid the CA from issuing | | caa | Certification Authority Authorization |
| | (CAA) records forbid the CA from issuing |
| | | | | |
| dns | There was a problem with a DNS query | | dns | There was a problem with a DNS query |
| | | | | |
| connection | The server could not connect to | | connection | The server could not connect to |
| | validation target | | | validation target |
| | | | | |
| tls | The server received a TLS error during | | tls | The server received a TLS error during |
| | validation | | | validation |
| | | | | |
| incorrectResponse | Response received didn't match the | | incorrectResponse | Response received didn't match the |
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| | | | | |
| connection | The server could not connect to | | connection | The server could not connect to |
| | validation target | | | validation target |
| | | | | |
| tls | The server received a TLS error during | | tls | The server received a TLS error during |
| | validation | | | validation |
| | | | | |
| incorrectResponse | Response received didn't match the | | incorrectResponse | Response received didn't match the |
| | challenge's requirements | | | 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 [RFC3553] namespace for errors other than
standard types. Clients SHOULD display the "detail" field of all the standard types. Clients SHOULD display the "detail" field of all
errors. errors.
7. Certificate Management 7. 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
7.1. Resources 7.1. Resources
ACME is structured as a REST application with a few types of ACME is structured as a REST application with the following 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) (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 (Section 7.1.3) 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 (Section 7.1.4) to act for an identifier (Section 7.1.4)
skipping to change at page 16, line 4 skipping to change at page 15, line 47
o Certificate resources, representing issued certificates o Certificate resources, representing issued certificates
(Section 7.4.2) (Section 7.4.2)
o A "directory" resource (Section 7.1.1) o A "directory" resource (Section 7.1.1)
o A "new-nonce" resource (Section 7.2) o A "new-nonce" resource (Section 7.2)
o A "new-account" resource (Section 7.3) o A "new-account" resource (Section 7.3)
o A "new-order" resource (Section 7.4) o A "new-order" resource (Section 7.4)
o A "revoke-certificate" resource (Section 7.6)
o A "key-change" resource (Section 7.3.3) o A "revoke-cert" resource (Section 7.6)
o A "key-change" resource (Section 7.3.6)
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 URLs 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 URL,
so clients only need to be configured with the directory URI. These so clients only need to be configured with the directory URL. These
URIs are connected by a few different link relations [RFC5988]. URLs 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 "index" link relation is present on all resources other than the The "index" link relation is present on all resources other than the
directory and indicates the URL of the directory. directory and indicates the URL of the directory.
skipping to change at page 16, line 41 skipping to change at page 16, line 36
|--> 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
| | | | | |
| | | | | |
V | V V | V
acct | order --------> cert account | order -----> cert
| | ^ | | |
| | | "up" | "up" | |
| V | V | V
+------> authz cert-chain +------> authz
| ^ | ^
| | "up" | | "up"
V | V |
challenge challenge
The following table illustrates a typical sequence of requests The following table illustrates a typical sequence of requests
required to establish a new account with the server, prove control of required to establish a new account with the server, prove control of
an identifier, issue a certificate, and fetch an updated certificate an identifier, issue a certificate, and fetch an updated certificate
some time after issuance. The "->" is a mnemonic for a Location some time after issuance. The "->" is a mnemonic for a Location
header pointing to a created resource. header pointing to a created resource.
skipping to change at page 17, line 34 skipping to change at page 17, line 28
| 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.
7.1.1. 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 URLs 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
object, whose keys are drawn from the following table and whose object, whose fields names are drawn from the following table and
values are the corresponding URLs. whose values are the corresponding URLs.
+-------------+--------------------+ +-------------+--------------------+
| Key | URL in value | | Field | 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 |
| | | | | |
| new-authz | New authorization | | new-authz | New authorization |
| | | | | |
| 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 URL 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' URLs,
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 functions as both an ACME and a Web server may want o a host which functions as both an ACME and a Web server may want
to keep the root path "/" for an HTML "front page", and place the to keep the root path "/" for an HTML "front page", and place the
ACME directory under the 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 the path "/". directory under the path "/".
The object MAY additionally contain a key "meta". If present, it The object MAY additionally contain a field "meta". If present, it
MUST be a JSON object; each field in the object 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 URL 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 recognizes 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 records. 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 URL.
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",
"new-order": "https://example.com/acme/new-order", "new-order": "https://example.com/acme/new-order",
"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/2017-5-30",
"website": "https://www.example.com/", "website": "https://www.example.com/",
"caa-identities": ["example.com"] "caa-identities": ["example.com"]
} }
} }
7.1.2. Account Objects 7.1.2. Account Objects
An ACME account resource represents a set of metadata associated with 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:
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 client-initiated
deactivation whereas "revoked" should be used to indicate deactivation whereas "revoked" should be used to indicate server-
administratively initiated deactivation. initiated deactivation.
contact (optional, array of string): An array of URIs that the contact (optional, array of string): An array of URLs 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 URL 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 7.1.2.1. described in Section 7.1.2.1.
{ {
"status": "valid",
"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"
} }
7.1.2.1. 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" URL 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 URLs, 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 URLs. The server MAY
return an incomplete list, along with a Link header with a "next" return an incomplete list, along with a Link header with a "next"
link relation indicating where further entries can be acquired. 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",
skipping to change at page 22, line 10 skipping to change at page 21, line 37
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 fulfilled 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 orders.
7.1.4. 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.
skipping to change at page 22, line 40 skipping to change at page 22, line 18
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". and "revoked".
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 URL 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. the authorization expires.
challenges (required, array of objects): The challenges that the challenges (required, array of objects): For pending authorizations,
client can fulfill in order to prove possession of the identifier the challenges that the client can fulfill in order to prove
(for pending authorizations). For final authorizations, the possession of the identifier. For final authorizations, the
challenges that were used. Each array entry is an object with challenges that were used. Each array entry is an object with
parameters required to validate the challenge. A client should parameters required to validate the challenge. A client should
attempt to fulfill one of these challenges, and a server should attempt to fulfill one of these challenges, and a server should
consider any one of the challenges sufficient to make the consider any one of the challenges sufficient to make the
authorization valid. For final authorizations it contains the authorization valid. For final authorizations it contains the
challenges that were completed. challenges that were successfully 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"). If a domain name contains non- qualified domain name (type: "dns"). If a domain name contains non-
ASCII Unicode characters it MUST be encoded using the rules defined ASCII Unicode characters it MUST be encoded using the rules defined
in [RFC3492]. Servers MUST verify any identifier values that begin in [RFC3492]. Servers MUST verify any identifier values that begin
with the ASCII Compatible Encoding prefix "xn-" as defined in 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. Section 8 describes a set of challenges for domain name validation.
skipping to change at page 23, line 28 skipping to change at page 23, line 16
"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": [
{ {
"url": "https://example.com/authz/1234/0",
"type": "http-01", "type": "http-01",
"status": "valid", "status": "valid",
"token": "DGyRejmCefe7v4NfDGDKfA"
"validated": "2014-12-01T12:05:00Z", "validated": "2014-12-01T12:05:00Z",
"keyAuthorization": "SXQe-2XODaDxNR...vb29HhjjLPSggwiE" "keyAuthorization": "SXQe-2XODaDxNR...vb29HhjjLPSggwiE"
} }
] ]
} }
7.2. 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
skipping to change at page 24, line 21 skipping to change at page 24, line 10
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.
7.3. 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 URL. The body of the request is
a stub account object containing the "contact" field and optionally a stub account object containing the "contact" field and optionally
the "terms-of-service-agreed" field. the "terms-of-service-agreed" field.
contact (optional, array of string): Same meaning as the
corresponding server field defined in Section 7.1.2
terms-of-service-agreed (optional, boolean): Same meaning as the
corresponding server field defined in Section 7.1.2
only-return-existing (optional, boolean): If this field is present
with the value "true", then the server MUST NOT create a new
account if one does not already exist. This allows a client to
look up an account URL based on an account key (see
Section 7.3.1).
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",
"url": "https://example.com/acme/new-account" "url": "https://example.com/acme/new-account"
skipping to change at page 25, line 11 skipping to change at page 25, line 11
it does not recognize. If new fields are specified in the future, it does not recognize. If new fields are specified in the future,
the specification of those fields MUST describe whether they can be the specification of those fields MUST describe whether they can 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 server validates
the server with an invalid or unsupported contact URL, then the contact URLs it MUST support the "mailto" scheme. If the server
server MUST return an error of type "invalidContact", with a rejects a contact URL for using an unsupported scheme it MUST return
description describing the error and what types of contact URL the an error of type "unsupportedContact", with a description describing
server considers acceptable. the error and what types of contact URLs the server considers
acceptable. If the server rejects a contact URL for using a
The server creates an account and stores the public key used to supported scheme but an invalid value then the server MUST return an
verify the JWS (i.e., the "jwk" element of the JWS header) to error of type "invalidContact".
authenticate future requests from the account. The server returns
this account object in a 201 (Created) response, with the account URI
in a Location header field.
If the server already has an account registered with the provided
account key, then it MUST return a response with a 200 (OK) status
code and provide the URI of that account in the Location header
field. This allows a client that has an account key but not the
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 URL 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.
The server creates an account and stores the public key used to
verify the JWS (i.e., the "jwk" element of the JWS header) to
authenticate future requests from the account. The server returns
this account object in a 201 (Created) response, with the account URL
in a Location header field.
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="index" Link: <https://example.com/acme/some-directory>;rel="index"
{ {
"status": "valid", "status": "valid",
"contact": [ "contact": [
"mailto:cert-admin@example.com", "mailto:cert-admin@example.com",
"tel:+12025551212" "tel:+12025551212"
] ]
} }
7.3.1. Finding an Account URL Given a Key
If the server already has an account registered with the provided
account key, then it MUST return a response with a 200 (OK) status
code and provide the URL of that account in the Location header
field. This allows a client that has an account key but not the
corresponding account URL to recover the account URL.
If a client wishes to find the URL for an existing account and does
not want an account to be created if one does not already exist, then
it SHOULD do so by sending a POST request to the new-account URL with
a JWS whose payload has an "only-return-existing" field set to "true"
({"only-return-existing": true}). If a client sends such a request
and an account does not exist, then the server MUST return an error
response with status code 400 (Bad Request) and type
"urn:ietf:params:acme:error:accountDoesNotExist".
7.3.2. Account Update
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 URL.
The server MUST ignore any updates to "order" fields or any other The server MUST ignore any updates to "order" fields or any other
fields it does not recognize. fields it does not recognize. If the server accepts the update, it
MUST return a response with a 200 (OK) status code and the resulting
account object.
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 26, line 32 skipping to change at page 27, line 5
}), }),
"payload": base64url({ "payload": base64url({
"contact": [ "contact": [
"mailto:certificates@example.com", "mailto:certificates@example.com",
"tel:+12125551212" "tel:+12125551212"
] ]
}), }),
"signature": "hDXzvcj8T6fbFbmn...rDzXzzvzpRy64N0o" "signature": "hDXzvcj8T6fbFbmn...rDzXzzvzpRy64N0o"
} }
7.3.3. Account Information
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 an empty object ({}). whose payload is an empty object ({}).
7.3.1. Changes of Terms of Service 7.3.4. 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
include a Link header with link relation "terms-of-service" and the include a Link header with link relation "terms-of-service" and the
latest terms-of-service URL. latest terms-of-service URL.
The problem document returned with the error MUST also include an The problem document returned with the error MUST also include an
"instance" field, indicating a URL that the client should direct a "instance" field, indicating a URL that the client should direct a
human user to visit in order for instructions on how to agree to the human user to visit in order for instructions on how to agree to the
terms. terms.
HTTP/1.1 403 Forbidden HTTP/1.1 403 Forbidden
Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw
Content-Type: application/problem+json Link: <https://example.com/acme/terms/2017-6-02>;rel="terms-of-service"
Content-Language: en Content-Type: application/problem+json
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"
} }
7.3.2. External Account Binding 7.3.5. 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 12 skipping to change at page 30, line 12
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-account any of these checks fail, then the CA MUST reject the new-account
request. request.
7.3.3. Account Key Roll-over 7.3.6. Account Key Roll-over
A client may wish to change the public key that is associated with an 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
skipping to change at page 29, line 37 skipping to change at page 30, line 37
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 6.2). 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" header 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" header parameter.
server MUST ignore any value provided for the "nonce" header The 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
agree to the change. The signatures are nested to preserve the agree to the change. The signatures are nested to preserve the
property that all signatures on POST messages are signed by exactly property that all signatures on POST messages are signed by exactly
one key. one key.
POST /acme/key-change HTTP/1.1 POST /acme/key-change 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": /* old key */, "kid": "https://example.com/acme/acct/1",
"nonce": "K60BWPrMQG9SDxBDS_xtSw", "nonce": "K60BWPrMQG9SDxBDS_xtSw",
"url": "https://example.com/acme/key-change" "url": "https://example.com/acme/key-change"
}), }),
"payload": base64url({ "payload": base64url({
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"jwk": /* new key */, "jwk": /* new key */,
"url": "https://example.com/acme/key-change" "url": "https://example.com/acme/key-change"
}), }),
"payload": base64url({ "payload": base64url({
skipping to change at page 30, line 35 skipping to change at page 31, line 35
}), }),
"signature": "Xe8B94RD30Azj2ea...8BmZIRtcSKPSd8gU" "signature": "Xe8B94RD30Azj2ea...8BmZIRtcSKPSd8gU"
}), }),
"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 Section 6.
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.
skipping to change at page 31, line 11 skipping to change at page 32, line 11
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 also 8. Check that the "newKey" field of the key-change object also
verifies the inner JWS. verifies the inner JWS.
9. Check that no account exists whose account key is the same as the
key in the "newKey" field.
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 (OK). 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. If there is an existing account with the new key
provided, then the server SHOULD use status code 409 (Conflict).
7.3.4. Account deactivation Note that changing the account key for an account SHOULD NOT have any
other impact on the account. For example, the server MUST NOT
invalidate pending orders or authorization transactions based on a
change of account key.
7.3.7. Account Deactivation
A client can 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 or decommissioned. 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
{ {
skipping to change at page 31, line 45 skipping to change at page 33, line 6
"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 replies with a 200 If the server accepts the deactivation request, it replies with a 200
(OK) status code and the current contents of the account object. (OK) status code and the current contents of the account 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. A server may take a requests authorized by that account's key. The server SHOULD cancel
variety of actions in response to an account deactivation, e.g., any pending operations authorized by the account's key, such as
deleting data related to that account or sending mail to the certificate orders. A server may take a variety of actions in
account's contacts. Servers SHOULD NOT revoke certificates issued by response to an account deactivation, e.g., deleting data related to
the deactivated account, since this could cause operational that account or sending mail to the account's contacts. Servers
disruption for servers using these certificates. ACME does not SHOULD NOT revoke certificates issued by the deactivated account,
provide a way to reactivate a deactivated account. since this could cause operational disruption for servers using these
certificates. ACME does not provide a way to reactivate a
deactivated account.
7.4. Applying for Certificate Issuance 7.4. Applying for Certificate Issuance
The client requests certificate issuance by sending a POST request to The client requests certificate issuance 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 7.1.3, 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
skipping to change at page 33, line 42 skipping to change at page 35, line 34
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 7.5). 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 begin the issuance process for the requested
resource with a URL for the certificate shortly after the client has certificate and update the order resource with a URL for the
fulfilled the server's requirements. If the client has already certificate once the client has fulfilled the server's requirements.
satisfied the server's requirements at the time of this request If the client has already satisfied the server's requirements at the
(e.g., by obtaining authorization for all of the identifiers in the time of this request (e.g., by obtaining authorization for all of the
certificate in previous transactions), then the server MUST identifiers in the certificate in previous transactions), then the
proactively issue the requested certificate and provide a URL for it server MUST proactively issue the requested certificate and provide a
in the "certificate" field of the order. The server MUST, however, URL for it in the "certificate" field of the order. The server MUST,
still list the completed authorizations in the "authorizations" however, still list the completed authorizations in the
array. "authorizations" array.
Once the client believes it has fulfilled the server's requirements, Once the client believes it has fulfilled the server's requirements,
it should send a GET request to the order resource to obtain its it should send a GET request to the order resource to obtain its
current state. The status of the order will indicate what action the current state. The status of the order will indicate what action the
client should take: client should take:
o "invalid": The certificate will not be issued. Consider this o "invalid": The certificate will not be issued. Consider this
order process abandoned. order process abandoned.
o "pending": The server does not believe that the client has o "pending": The server does not believe that the client has
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virtual servers are created and only create a certificate when a virtual servers are created and only create a certificate when a
virtual server 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 field
authz" with a URL for the new authorization resource. "new-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, object): The identifier that the account is identifier (required, object): The identifier that the 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.
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": {...}, "kid": "https://example.com/acme/acct/1",
"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"
} }
}), }),
"signature": "nuSDISbWG8mMgE7H...QyVUL68yzf3Zawps" "signature": "nuSDISbWG8mMgE7H...QyVUL68yzf3Zawps"
skipping to change at page 35, line 46 skipping to change at page 37, line 42
the rejection. the rejection.
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 policy o "challenges" as selected by the server's policy for this
for this identifier identifier
The server allocates a new URI for this authorization, and returns a The server allocates a new URL for this authorization, and returns a
201 (Created) response, with the authorization URI in the Location 201 (Created) response, with the authorization URL 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 7.5 to complete client then follows the process described in Section 7.5 to complete
the authorization process. the authorization process.
7.4.2. 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 application/pem-certificate- The default format of the certificate is application/pem-certificate-
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1. That the client controls the private key of the account key pair, 1. That the client controls the private key of the account key pair,
and and
2. That the client controls the identifier in question. 2. That the client controls the identifier in question.
This process may be repeated to associate multiple identifiers to a This process may be repeated to associate multiple identifiers to a
key pair (e.g., to request certificates with multiple identifiers), key pair (e.g., to request certificates with multiple identifiers),
or to associate multiple accounts with an identifier (e.g., to allow or to associate multiple accounts with an identifier (e.g., to allow
multiple entities to manage certificates). The server may declare multiple entities to manage certificates). The server may declare
that an authorization is only valid for a specific order by setting that an authorization is only valid for a specific order by setting
the "scope" field of the authorization to the URI for that order. the "scope" field of the authorization to the URL 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 resources by sending GET requests to the indicated authorization resources by sending GET requests to the indicated
URLs. If the client initiates authorization using a request to the URLs. If the client initiates authorization using a request to the
skipping to change at page 38, line 50 skipping to change at page 40, line 50
7.5.1. 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. the "challenges" dictionary.
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 URL (not authorization
URI) once it is ready for the server to attempt validation. URL) once it is ready for the server to attempt validation.
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/1234/0 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": "Q_s3MWoqT05TrdkM2MTDcw", "nonce": "Q_s3MWoqT05TrdkM2MTDcw",
"url": "https://example.com/acme/authz/asdf/0" "url": "https://example.com/acme/authz/1234/0"
}), }),
"payload": base64url({ "payload": base64url({
"type": "http-01", "type": "http-01",
"keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE" "keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE"
}), }),
"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
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The server SHOULD NOT remove challenges with status "invalid". The server SHOULD NOT remove challenges with status "invalid".
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 URL, 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 200 the validation is still in progress, the server MUST return a 200
(OK) response and MAY include a Retry-After header field to suggest a (OK) response and MAY include a Retry-After header field to suggest a
polling interval to the client. polling interval to the client.
GET /acme/authz/asdf 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
{ {
"status": "valid", "status": "valid",
"expires": "2018-09-09T14:09:00Z", "expires": "2018-09-09T14:09:00Z",
"identifier": { "identifier": {
"type": "dns", "type": "dns",
"value": "example.org" "value": "example.org"
}, },
"challenges": [ "challenges": [
{ {
"type": "http-01" "type": "http-01"
"url": "https://example.com/authz/asdf/0", "url": "https://example.com/authz/1234/0",
"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"
} }
] ]
} }
7.5.2. 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
deactivates each authorization associated with it by sending POST deactivates each authorization associated with it by sending POST
requests with the static object {"status": "deactivated"} to each requests with the static object {"status": "deactivated"} to each
authorization URI. authorization URL.
POST /acme/authz/asdf HTTP/1.1 POST /acme/authz/1234 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",
"url": "https://example.com/acme/authz/asdf" "url": "https://example.com/acme/authz/1234"
}), }),
"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 updated 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.
7.6. 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 URL. 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
Section 5.3.1 of [RFC5280] to be used when generating OCSP Section 5.3.1 of [RFC5280] to be used when generating OCSP
skipping to change at page 42, line 12 skipping to change at page 44, line 12
problem document detail SHOULD indicate which reasonCodes are problem document detail SHOULD indicate which reasonCodes are
allowed. 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" "jwk": /* account key */,
"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 requests 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 MUST 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.
The server SHOULD also consider a revocation request valid if it is The server MUST also consider a revocation request valid if it is
signed with the private key corresponding to the public key in the signed with the private key corresponding to the public key in the
certificate. certificate.
If the revocation succeeds, the server responds with status code 200 If the revocation succeeds, the server responds with status code 200
(OK). If the revocation fails, the server returns an error. (OK). If the revocation fails, the server returns an error.
HTTP/1.1 200 OK HTTP/1.1 200 OK
Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw Replay-Nonce: IXVHDyxIRGcTE0VSblhPzw
Content-Length: 0 Content-Length: 0
skipping to change at page 43, line 48 skipping to change at page 45, line 48
o Control the identifier in question o Control the identifier in question
Section 10 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 URL.
This section describes an initial set of challenge types. Each This section describes an initial set of challenge types. Each
challenge must describe: challenge must describe:
1. Content of challenge objects 1. Content of challenge objects
2. Content of response objects 2. Content of response objects
3. How the server uses the challenge and response to verify control 3. How the server uses the challenge and response to verify control
of an identifier of an identifier
skipping to change at page 44, line 27 skipping to change at page 46, 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, object): The error that occurred while the server errors (optional, array of object): Errors that occurred while the
was validating the challenge, if any. This field is structured as server was validating the challenge, if any, structured as problem
a problem document [RFC7807]. documents [RFC7807]. The server MUST NOT modify the array except
by appending entries onto the end. The server can limit the size
of this object by limiting the number of times it will retry a
challenge.
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 the include the "error" field to help the client diagnose why the
challenge failed. 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 identifiers, 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,
challenges are labeled by type, and with the version of the draft in
which they were introduced. For example, if an HTTP challenge were
introduced in version -03 and a breaking change made in version -05,
then there would be a challenge labeled "http-03" and one labeled
"http-05" - but not one labeled "http-04", since challenge in version
-04 was compatible with one in version -03. ]]
8.1. Key Authorizations 8.1. Key Authorizations
Several of the challenges in this document make 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 [FIPS180-4]. As noted in JWA [RFC7638], using the SHA-256 digest [FIPS180-4]. As noted in JWA
[RFC7518] any prepended zero octets in the JWK object MUST be [RFC7518] any prepended zero octets in the JWK object MUST be
stripped before doing the computation. stripped before doing the computation.
As specified in the individual challenges below, the token for a As specified in the individual challenges below, the token for a
challenge is a string comprised entirely of characters in the URL- challenge is a string comprised entirely of characters in the URL-
safe base64 alphabet. The "||" operator indicates concatenation of safe base64 alphabet. The "||" operator indicates concatenation of
strings. strings.
8.2. HTTP 8.2. Retrying Challenges
ACME challenges typically require the client to set up some network-
accessible resource that the server can query in order to validate
that the client controls an identifier. In practice it is not
uncommon for the server's queries to fail while a resource is being
set up, e.g., due to information propagating across a cluster or
firewall rules not being in place.
Clients SHOULD NOT respond to challenges until they believe that the
server's queries will succeed. If a server's initial validation
query fails, the server SHOULD retry the query after some time.
While the server is still trying, the status of the challenge remains
"pending"; it is only marked "invalid" once the server has given up.
The server MUST provide information about its retry state to the
client via the "errors" field in the challenge and the Retry-After
HTTP header field in response to requests to the challenge resource.
The server MUST add an entry to the "errors" field in the challenge
after each failed validation query. The server SHOULD set the Retry-
After header field to a time after the server's next validation
query, since the status of the challenge will not change until that
time.
Clients can explicitly request a retry by re-sending their response
to a challenge in a new POST request (with a new nonce, etc.). This
allows clients to request a retry when state has changed (e.g., after
firewall rules have been updated). Servers SHOULD retry a request
immediately on receiving such a POST request. In order to avoid
denial-of-service attacks via client-initiated retries, servers
SHOULD rate-limit such requests.
8.3. HTTP Challenge
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 for that domain name it control over a domain name by proving that for that domain name it
can provision resources to be returned by an HTTP server. 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 the DNS A server will connect to at least one of the hosts found in the DNS A
and AAAA records, at its discretion. Because many web servers and AAAA records, at its discretion. Because many web servers
allocate a default HTTPS virtual host to a particular low-privilege allocate a default HTTPS virtual host to a particular low-privilege
tenant user in a subtle and non-intuitive manner, the challenge must tenant user in a subtle and non-intuitive manner, the challenge must
be completed 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 It MUST NOT contain any characters outside the base64url alphabet,
contain any characters outside the base64url alphabet, including including 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": "evaGxfADs6pSRb2LAv9IZf17" "token": "LoqXcYV8q5ONbJQxbmR7SCTNo3tiAXDfowyjxAjEuX0"
} }
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.
GET .well-known/acme-challenge/evaGxfADs6pSRb2LAv9IZf17 GET .well-known/acme-challenge/LoqXcYV8q5ONbJQxbmR7SCTNo3tiAXDfowyjxAjEuX0
Host: example.com Host: example.org
HTTP/1.1 200 OK HTTP/1.1 200 OK
LoqXcYV8q5ONbJQxbmR7SCTNo3tiAXDfowyjxAjEuX0.9jg46WB3rR_AHD-EBXdN7cBkH1WOu0tA3M9fm21mqTI 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
skipping to change at page 47, line 32 skipping to change at page 49, line 46
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. Construct a URI by populating the URI template [RFC6570] 1. Construct a URL by populating the URL 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 URL is well-formed.
3. Dereference the URI using an HTTP GET request. This request MUST 3. Dereference the URL using an HTTP GET request. This request MUST
be sent to TCP port 80 on the HTTP 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 HTTP server matches 5. Verify that key authorization provided by the HTTP server matches
the token for this challenge and the client's account key. the key authorization provided by the client in its response to
the challenge.
The server SHOULD follow redirects when dereferencing the URI. The server SHOULD follow redirects when dereferencing the URL.
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.
8.3. TLS with Server Name Indication (TLS SNI) 8.4. TLS with Server Name Indication (TLS SNI) Challenge
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 the DNS A and AAAA resource configure a TLS server referenced by the DNS A and AAAA resource
records for the domain name to respond to specific connection records for the domain name to respond to specific connection
attempts utilizing the Server Name Indication extension [RFC6066]. attempts utilizing the Server Name Indication extension [RFC6066].
The server verifies the client's challenge by accessing the TLS The server verifies the client's challenge by accessing the TLS
server and verifying a particular 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 It MUST NOT contain any characters outside the base64url alphabet,
contain any characters outside the base64url alphabet, including including 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 [RFC5280].
SAN A MUST be constructed as follows: compute the SHA-256 digest SAN A MUST be constructed as follows: compute the SHA-256 digest
[FIPS180-4] of the 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 key authorization and encode it in lowercase hexadecimal form. the key authorization and encode it in lowercase hexadecimal form.
The dNSName is "x.y.ka.acme.invalid" where x is the first half of the The dNSName is "x.y.ka.acme.invalid" where x is the first half of the
skipping to change at page 50, line 14 skipping to change at page 52, line 25
extension (i.e., SNI) containing SAN A. The server SHOULD ensure extension (i.e., SNI) containing SAN A. The server SHOULD ensure
that it does not reveal SAN B in any way when making the TLS that it does not reveal SAN B in any way when making the TLS
connection, such that the presentation of SAN B in the returned connection, such that the presentation of SAN B in the returned
certificate 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 opens multiple TLS connections 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. Otherwise, the validation fails. successful. Otherwise, the validation fails.
8.4. DNS 8.5. DNS Challenge
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 TXT resource record prove control of that domain by provisioning a TXT resource record
containing a designated value for a specific validation domain name. containing a designated value for 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 It MUST NOT contain any characters outside the base64url alphabet,
contain any characters outside the base64url alphabet, including including 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"
skipping to change at page 51, line 7 skipping to change at page 53, line 14
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 [FIPS180-4] 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.org", then the client would provision the following DNS
record: record:
_acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM" _acme-challenge.example.org. 300 IN TXT "gfj9Xq...Rg85nM"
The response to the DNS challenge provides the computed key The response to the DNS challenge provides the computed key
authorization to acknowledge that the client is ready to fulfill this authorization to acknowledge that the client is ready to fulfill this
challenge. 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.
POST /acme/authz/1234/2 POST /acme/authz/1234/2
skipping to change at page 52, line 9 skipping to change at page 54, line 16
2. Query for TXT records for the validation domain name 2. Query for TXT records for 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
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.
8.5. Out-of-Band 8.6. Out-of-Band Challenge
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.
skipping to change at page 52, line 34 skipping to change at page 54, line 41
URL MUST be "http" or "https". Note that this field is distinct URL MUST be "http" or "https". Note that this field is distinct
from the "url" field of the challenge, which identifies the from the "url" field of the challenge, which identifies the
challenge itself. challenge itself.
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",
"url": "https://example.com/acme/authz/1234/3",
"status": "pending",
"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 chooses to complete for a human user to navigate to. If the user chooses to complete
this challenge (by visiting the website and completing its this challenge (by visiting the website and completing its
instructions), the client indicates this by sending a simple instructions), the client indicates this by sending a simple
acknowledgement response to the server. acknowledgement response to the server.
type (required, string): The string "oob-01" type (required, string): The string "oob-01"
skipping to change at page 53, line 43 skipping to change at page 55, line 43
MIME media type name: application MIME media type name: application
MIME subtype name: pem-certificate-chain MIME subtype name: pem-certificate-chain
Required parameters: None Required parameters: None
Optional parameters: None Optional parameters: None
Encoding considerations: None Encoding considerations: None
Security considerations: Carries a cryptographic certificate Security considerations: Carries a cryptographic certificate and its
associated certificate chain
Interoperability considerations: None Interoperability considerations: None
Published specification: draft-ietf-acme-acme [[ RFC EDITOR: Please Published specification: draft-ietf-acme-acme [[ RFC EDITOR: Please
replace draft-ietf-acme-acme above with the RFC number assigned to replace draft-ietf-acme-acme above with the RFC number assigned to
this ]] this ]]
Applications which use this media type: Any MIME-complaint transport Applications which use this media type: Any MIME-complaint transport
Additional information: Additional information:
File should contain one or more certificates encoded as PEM according File should contain one or more certificates encoded as PEM according
to RFC 7468. In order to provide easy interoperation with TLS, the to RFC 7468 [RFC7468]. In order to provide easy interoperation with
first certificate MUST be an end-entity certificate. Each following TLS, the first certificate MUST be an end-entity certificate. Each
certificate SHOULD directly certify one preceding it. Because following certificate SHOULD directly certify one preceding it.
certificate validation requires that trust anchors be distributed Because certificate validation requires that trust anchors be
independently, a certificate that specifies a trust anchor MAY be distributed independently, a certificate that specifies a trust
omitted from the chain, provided that supported peers are known to anchor MAY be omitted from the chain, provided that supported peers
possess any omitted certificates. are known to possess any omitted certificates.
9.2. Well-Known URI for the HTTP Challenge 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 8.2 Specification document(s): This document, Section Section 8.3
Related information: N/A Related information: N/A
9.3. 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 | | Header Field Name | Protocol | Status | Reference |
skipping to change at page 56, line 24 skipping to change at page 58, line 26
Specification Required policy [RFC5226]. Specification Required policy [RFC5226].
9.7.1. Fields in Account Objects 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 object o Field name: The string to be used as a field name 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 7.1.2. Section 7.1.2.
+--------------------------+-------------+--------------+-----------+ +--------------------------+-------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
+--------------------------+-------------+--------------+-----------+ +--------------------------+-------------+--------------+-----------+
| 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 | object | true | RFC XXXX | | external-account-binding | object | true | RFC XXXX |
| | | | | | | | | |
| terms-of-service-agreed | boolean | true | RFC XXXX | | terms-of-service-agreed | boolean | true | RFC XXXX |
| | | | | | | | | |
| orders | array of | false | RFC XXXX | | orders | array of | false | RFC XXXX |
skipping to change at page 57, line 31 skipping to change at page 59, line 29
+--------------------------+-------------+--------------+-----------+ +--------------------------+-------------+--------------+-----------+
9.7.2. 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 object o Field name: The string to be used as a field name 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
skipping to change at page 58, line 48 skipping to change at page 60, line 48
Section 6.6 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.
9.7.4. 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 field name in the directory object o Field name: The value to be used as a field name in the directory
object
o Resource type: The type of resource labeled by the key
o Resource type: The type of resource labeled by the field
o Reference: Where the resource type is defined o Reference: Where the resource type is defined
Initial contents: Initial contents:
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
| Key | Resource type | Reference | | Field Name | 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 ]]
9.7.5. Identifier Types 9.7.5. Identifier Types
This registry lists the types of identifiers in certificates that This registry lists the types of identifiers that can be present in
ACME clients may request authorization to issue. ACME authorization objects.
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:
skipping to change at page 60, line 15 skipping to change at page 62, line 17
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
Initial Contents Initial Contents
+---------+-----------------+-----------+ +------------+-----------------+-----------+
| Label | Identifier Type | Reference | | Label | Identifier Type | Reference |
+---------+-----------------+-----------+ +------------+-----------------+-----------+
| http | dns | RFC XXXX | | http-01 | dns | RFC XXXX |
| | | | | | | |
| tls-sni | dns | RFC XXXX | | tls-sni-02 | dns | RFC XXXX |
| | | | | | | |
| dns | dns | RFC XXXX | | dns-01 | dns | RFC XXXX |
+---------+-----------------+-----------+ | | | |
| oob-01 | 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 ]]
10. 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
skipping to change at page 65, line 25 skipping to change at page 67, line 25
Some server implementations include information from the validation Some server implementations include information from the validation
server's response (in order to facilitate debugging). Such server's response (in order to facilitate debugging). Such
implementations enable an attacker to extract this information from implementations enable an attacker to extract this information from
any web server that is accessible to the ACME server, even if it is any web server that is accessible to the ACME server, even if it is
not accessible to the ACME client. not accessible to the ACME client.
It might seem that the risk of SSRF through this channel is limited It might seem that the risk of SSRF through this channel is limited
by the fact that the attacker can only control the domain of the URL, by the fact that the attacker can only control the domain of the URL,
not the path. However, if the attacker first sets the domain to one not the path. However, if the attacker first sets the domain to one
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 URL.
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.
10.5. CA Policy Considerations 10.5. CA Policy Considerations
skipping to change at page 66, line 10 skipping to change at page 68, line 10
* Is the name on the Public Suffix List? * Is the name on the Public Suffix List?
* Is the name a high-value name? * Is the name a high-value name?
* Is the name a known phishing domain? * Is the name a known phishing domain?
o Is the key in the CSR sufficiently strong? o Is the key in the CSR sufficiently strong?
o Is the CSR signed with an acceptable algorithm? o Is the CSR signed with an acceptable algorithm?
o Has issuance been authorized or forbidden by a Certficate
Authority Authorization (CAA) record? [RFC6844]
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.
11. Operational Considerations 11. Operational Considerations
skipping to change at page 67, line 45 skipping to change at page 69, line 45
A CA can detect such a bounded default vhost by initiating TLS A CA can detect such a bounded default vhost by initiating TLS
connections to the host with random SNI values within the namespace connections to the host with random SNI values within the namespace
used for the TLS-based challenge (the "acme.invalid" namespace for used for the TLS-based challenge (the "acme.invalid" namespace for
"tls-sni-02"). If it receives the same certificate on two different "tls-sni-02"). If it receives the same certificate on two different
connections, then it is very likely that the server is in a default connections, then it is very likely that the server is in a default
virtual host configuration. Conversely, if the TLS server returns an virtual host configuration. Conversely, if the TLS server returns an
unrecognized_name alert, then this is an indication that the server unrecognized_name alert, then this is an indication that the server
is not in a default virtual host configuration. is not in a default virtual host configuration.
11.3. Token Entropy
The http-01, tls-sni-02 and dns-01 validation methods mandate the
usage of a random token value to uniquely identify the challenge.
The value of the token is required to contain at least 128 bits of
entropy for the following security properties. First, the ACME
client should not be able to influence the ACME server's choice of
token as this may allow an attacker to reuse a domain owner's
previous challenge responses for a new validation request. Secondly,
the entropy requirement prevents ACME clients from implementing a
"naive" validation server that automatically replies to challenges
without participating in the creation of the intial authorization
request.
11.4. Malformed Certificate Chains
ACME provides certificate chains in the widely-used format known
colloquially as PEM (though it may diverge from the actual Privacy
Enhanced Mail specifications [RFC1421], as noted in [RFC7468]). Some
current software will allow the configuration of a private key and a
certificate in one PEM file, by concatenating the textual encodings
of the two objects. In the context of ACME, such software might be
vulnerable to "key replacement" attacks. A malicious ACME server
could cause a client to use a private key of its choosing by
including the key in the PEM file returned in response to a query for
a certificate URL.
When processing an file of type "application/pem-certificate-chain",
a client SHOULD verify that the file contains only encoded
certificates. If anything other than a certificate is found (i.e.,
if the string "---BEGIN" is ever followed by anything other than
"CERTIFICATE"), then the client MUST reject the file as invalid.
12. 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 28 skipping to change at page 72, line 15
[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 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <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
skipping to change at page 70, line 29 skipping to change at page 73, line 14
[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>.
[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
skipping to change at page 71, line 5 skipping to change at page 73, line 41
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>.
13.2. 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.
[RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic
Mail: Part I: Message Encryption and Authentication
Procedures", RFC 1421, DOI 10.17487/RFC1421, February
1993, <http://www.rfc-editor.org/info/rfc1421>.
[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>.
skipping to change at page 71, line 28 skipping to change at page 74, line 23
<http://www.rfc-editor.org/info/rfc5785>. <http://www.rfc-editor.org/info/rfc5785>.
[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 Cisco
Email: rlb@ipv.sx Email: rlb@ipv.sx
Jacob Hoffman-Andrews Jacob Hoffman-Andrews
EFF EFF
Email: jsha@eff.org Email: jsha@eff.org
James Kasten James Kasten
University of Michigan University of Michigan
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