draft-ietf-acme-acme-02.txt   draft-ietf-acme-acme-03.txt 
Network Working Group R. Barnes Network Working Group R. Barnes
Internet-Draft Mozilla Internet-Draft Mozilla
Intended status: Standards Track J. Hoffman-Andrews Intended status: Standards Track J. Hoffman-Andrews
Expires: September 22, 2016 EFF Expires: January 9, 2017 EFF
J. Kasten J. Kasten
University of Michigan University of Michigan
March 21, 2016 July 08, 2016
Automatic Certificate Management Environment (ACME) Automatic Certificate Management Environment (ACME)
draft-ietf-acme-acme-02 draft-ietf-acme-acme-03
Abstract Abstract
Certificates in the Web's X.509 PKI (PKIX) are used for a number of Certificates in the Web's X.509 PKI (PKIX) are used for a number of
purposes, the most significant of which is the authentication of purposes, the most significant of which is the authentication of
domain names. Thus, certificate authorities in the Web PKI are domain names. Thus, certificate authorities in the Web PKI are
trusted to verify that an applicant for a certificate legitimately trusted to verify that an applicant for a certificate legitimately
represents the domain name(s) in the certificate. Today, this represents the domain name(s) in the certificate. Today, this
verification is done through a collection of ad hoc mechanisms. This verification is done through a collection of ad hoc mechanisms. This
document describes a protocol that a certificate authority (CA) and document describes a protocol that a certificate 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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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 22, 2016. This Internet-Draft will expire on January 9, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Deployment Model and Operator Experience . . . . . . . . . . 4 2. Deployment Model and Operator Experience . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
5. Message Transport . . . . . . . . . . . . . . . . . . . . . . 9 5. Message Transport . . . . . . . . . . . . . . . . . . . . . . 8
5.1. HTTPS Requests . . . . . . . . . . . . . . . . . . . . . 9 5.1. HTTPS Requests . . . . . . . . . . . . . . . . . . . . . 9
5.2. Request Authentication . . . . . . . . . . . . . . . . . 9 5.2. Request Authentication . . . . . . . . . . . . . . . . . 9
5.3. Request URI Type Integrity . . . . . . . . . . . . . . . 10 5.3. Request URI Integrity . . . . . . . . . . . . . . . . . . 10
5.3.1. "url" (URL) JWS header parameter . . . . . . . . . . 10
5.4. Replay protection . . . . . . . . . . . . . . . . . . . . 11 5.4. Replay protection . . . . . . . . . . . . . . . . . . . . 11
5.4.1. Replay-Nonce . . . . . . . . . . . . . . . . . . . . 12 5.4.1. Replay-Nonce . . . . . . . . . . . . . . . . . . . . 11
5.4.2. "nonce" (Nonce) JWS header parameter . . . . . . . . 12 5.4.2. "nonce" (Nonce) JWS header parameter . . . . . . . . 12
5.5. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.5. Rate limits . . . . . . . . . . . . . . . . . . . . . . . 12
5.6. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. Certificate Management . . . . . . . . . . . . . . . . . . . 14 6. Certificate Management . . . . . . . . . . . . . . . . . . . 14
6.1. Resources . . . . . . . . . . . . . . . . . . . . . . . . 14 6.1. Resources . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1.1. Registration Objects . . . . . . . . . . . . . . . . 16 6.1.1. Directory . . . . . . . . . . . . . . . . . . . . . . 16
6.1.2. Authorization Objects . . . . . . . . . . . . . . . . 17 6.1.2. Registration Objects . . . . . . . . . . . . . . . . 17
6.2. Directory . . . . . . . . . . . . . . . . . . . . . . . . 18 6.1.3. Application Objects . . . . . . . . . . . . . . . . . 19
6.3. Registration . . . . . . . . . . . . . . . . . . . . . . 20 6.1.4. Authorization Objects . . . . . . . . . . . . . . . . 21
6.3.1. Account Key Roll-over . . . . . . . . . . . . . . . . 22 6.2. Registration . . . . . . . . . . . . . . . . . . . . . . 23
6.3.2. Deleting an Account . . . . . . . . . . . . . . . . . 23 6.2.1. Account Key Roll-over . . . . . . . . . . . . . . . . 25
6.4. Identifier Authorization . . . . . . . . . . . . . . . . 24 6.2.2. Account deactivation . . . . . . . . . . . . . . . . 27
6.4.1. Responding to Challenges . . . . . . . . . . . . . . 26 6.3. Applying for Certificate Issuance . . . . . . . . . . . . 28
6.4.2. Deleting an Authorization . . . . . . . . . . . . . . 28 6.3.1. Downloading the Certificate . . . . . . . . . . . . . 30
6.5. Certificate Issuance . . . . . . . . . . . . . . . . . . 29 6.4. Identifier Authorization . . . . . . . . . . . . . . . . 31
6.6. Certificate Revocation . . . . . . . . . . . . . . . . . 32 6.4.1. Responding to Challenges . . . . . . . . . . . . . . 33
7. Identifier Validation Challenges . . . . . . . . . . . . . . 33 6.4.2. Deactivating an Authorization . . . . . . . . . . . . 35
7.1. Key Authorizations . . . . . . . . . . . . . . . . . . . 35 6.5. Certificate Revocation . . . . . . . . . . . . . . . . . 36
7.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7. Identifier Validation Challenges . . . . . . . . . . . . . . 38
7.3. TLS with Server Name Indication (TLS SNI) . . . . . . . . 38 7.1. Key Authorizations . . . . . . . . . . . . . . . . . . . 39
7.4. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 7.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 7.3. TLS with Server Name Indication (TLS SNI) . . . . . . . . 42
9. Well-Known URI for the HTTP Challenge . . . . . . . . . . . . 41 7.4. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.1. Replay-Nonce HTTP Header . . . . . . . . . . . . . . . . 41 7.5. Out-of-Band . . . . . . . . . . . . . . . . . . . . . . . 45
9.2. "nonce" JWS Header Parameter . . . . . . . . . . . . . . 41 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46
9.3. URN Sub-namespace for ACME (urn:ietf:params:acme) . . . . 42 8.1. Well-Known URI for the HTTP Challenge . . . . . . . . . . 46
9.4. New Registries . . . . . . . . . . . . . . . . . . . . . 42 8.2. Replay-Nonce HTTP Header . . . . . . . . . . . . . . . . 47
9.4.1. Error Codes . . . . . . . . . . . . . . . . . . . . . 42 8.3. "url" JWS Header Parameter . . . . . . . . . . . . . . . 47
9.4.2. Identifier Types . . . . . . . . . . . . . . . . . . 43 8.4. "nonce" JWS Header Parameter . . . . . . . . . . . . . . 47
9.4.3. Challenge Types . . . . . . . . . . . . . . . . . . . 43 8.5. URN Sub-namespace for ACME (urn:ietf:params:acme) . . . . 48
10. Security Considerations . . . . . . . . . . . . . . . . . . . 44 8.6. New Registries . . . . . . . . . . . . . . . . . . . . . 48
10.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 44 8.6.1. Error Codes . . . . . . . . . . . . . . . . . . . . . 48
10.2. Integrity of Authorizations . . . . . . . . . . . . . . 45 8.6.2. Resource Types . . . . . . . . . . . . . . . . . . . 49
10.3. Denial-of-Service Considerations . . . . . . . . . . . . 48 8.6.3. Identifier Types . . . . . . . . . . . . . . . . . . 49
10.4. CA Policy Considerations . . . . . . . . . . . . . . . . 49 8.6.4. Challenge Types . . . . . . . . . . . . . . . . . . . 50
11. Operational Considerations . . . . . . . . . . . . . . . . . 49 9. Security Considerations . . . . . . . . . . . . . . . . . . . 50
11.1. Default Virtual Hosts . . . . . . . . . . . . . . . . . 49 9.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 51
11.2. Use of DNSSEC Resolvers . . . . . . . . . . . . . . . . 50 9.2. Integrity of Authorizations . . . . . . . . . . . . . . . 52
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 50 9.3. Denial-of-Service Considerations . . . . . . . . . . . . 54
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 51 9.4. Server-Side Request Forgery . . . . . . . . . . . . . . . 55
13.1. Normative References . . . . . . . . . . . . . . . . . . 51 9.5. CA Policy Considerations . . . . . . . . . . . . . . . . 55
13.2. Informative References . . . . . . . . . . . . . . . . . 53 10. Operational Considerations . . . . . . . . . . . . . . . . . 56
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54 10.1. DNS over TCP . . . . . . . . . . . . . . . . . . . . . . 56
10.2. Default Virtual Hosts . . . . . . . . . . . . . . . . . 56
10.3. Use of DNSSEC Resolvers . . . . . . . . . . . . . . . . 57
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 57
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 58
12.1. Normative References . . . . . . . . . . . . . . . . . . 58
12.2. Informative References . . . . . . . . . . . . . . . . . 60
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 61
1. Introduction 1. Introduction
Certificates in the Web PKI [RFC5280] are most commonly used to Certificates in the Web PKI [RFC5280] 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.
Existing Web PKI certificate authorities tend to run on a set of ad Existing Web PKI certificate authorities tend to run on a set of ad
hoc protocols for certificate issuance and identity verification. A hoc protocols for certificate issuance and identity verification. A
typical user experience is something like: typical user experience is something like:
o Generate a PKCS#10 [RFC2314] Certificate Signing Request (CSR). o Generate a PKCS#10 [RFC2986] Certificate Signing Request (CSR).
o Cut-and-paste the CSR into a CA web page. o Cut-and-paste the CSR into a CA web page.
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.
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In ACME, the account is represented by an account key pair. The "add In ACME, the account is represented by an account key pair. The "add
a domain" function is accomplished by authorizing the key pair for a a domain" function is accomplished by authorizing the key pair for a
given domain. Certificate issuance and revocation are authorized by given domain. Certificate issuance and revocation are authorized by
a signature with the key pair. a signature with the key pair.
The first phase of ACME is for the client to register with the ACME The first phase of ACME is for the client to register with the ACME
server. The client generates an asymmetric key pair and associates server. The client generates an asymmetric key pair and associates
this key pair with a set of contact information by signing the this key pair with a set of contact information by signing the
contact information. The server acknowledges the registration by contact information. The server acknowledges the registration by
replying with a registration object echoing the client's input. replying with a registration object echoing the client's input. The
server can also provide terms of service at this stage, which the
client can present to a human user.
Client Server Client Server
Contact Information Contact Information
Signature -------> Signature ------->
<------- Registration <------- Registration
Terms of Service
Before a client can issue certificates, it must establish an Once the client is registered, there are three major steps it needs
authorization with the server for an account key pair to act for the to take to get a certificate:
identifier(s) that it wishes to include in the certificate. To do
this, the client must demonstrate to the server both (1) that it
holds the private key of the account key pair, and (2) that it has
authority over the identifier being claimed.
Proof of possession of the account key is built into the ACME 1. Apply for a certificate to be issued
protocol. All messages from the client to the server are signed by
the client, and the server verifies them using the public key of the
account key pair.
To verify that the client controls the identifier being claimed, the 2. Fulfill the server's requirements for issuance
server issues the client a set of challenges. Because there are many
different ways to validate possession of different types of
identifiers, the server will choose from an extensible set of
challenges that are appropriate for the identifier being claimed.
The client responds with a set of responses that tell the server
which challenges the client has completed. The server then validates
the challenges to check that the client has accomplished the
challenge.
For example, if the client requests a domain name, the server might 3. Finalize the application and request issuance
challenge the client to provision a record in the DNS under that
name, or to provision a file on a web server referenced by an A or
AAAA record under that name. The server would then query the DNS for
the record in question, or send an HTTP request for the file. If the
client provisioned the DNS or the web server as expected, then the
server considers the client authorized for the domain name.
Client Server The client's application for a certificate describes the desired
certificate using a PKCS#10 Certificate Signing Request (CSR) plus a
few additional fields that capture semantics that are not supported
in the CSR format. If the server is willing to consider issuing such
a certificate, it responds with a list of requirements that the
client must satisfy before the certificate will be issued.
Identifier For example, in most cases, the server will require the client to
Signature -------> demonstrate that it controls the identifiers in the requested
certificate. Because there are many different ways to validate
possession of different types of identifiers, the server will choose
from an extensible set of challenges that are appropriate for the
identifier being claimed. The client responds with a set of
responses that tell the server which challenges the client has
completed. The server then validates the challenges to check that
the client has accomplished the challenge.
<------- Challenges Once the validation process is complete and the server is satisfied
that the client has met its requirements, the server can either
proactively issue the requested certificate or wait for the client to
request that the application be "finalized", at which point the
certificate will be issued and provided to the client.
Responses Application
Signature -------> Signature ------->
<------- Requirements
(e.g., Challenges)
<------- Updated Challenge Responses
Signature ------->
<~~~~~~~~Validation~~~~~~~~> <~~~~~~~~Validation~~~~~~~~>
Poll -------> Finalize application
Signature ------->
<------- Authorization <------- Certificate
Once the client has authorized an account key pair for an identifier,
it can use the key pair to authorize the issuance of certificates for
the identifier. To do this, the client sends a PKCS#10 Certificate
Signing Request (CSR) to the server (indicating the identifier(s) to
be included in the issued certificate) and a signature over the CSR
by the private key of the account key pair.
Note that as a result, the CSR is signed twice: One by the private
key corresponding to the public key in the CSR, and once by the
private key of the account key pair. The former signature indicates
that the holder of the key in the CSR is willing to act for the
indicated identifiers, and the latter signature indicates to the
server that the issuance of the certificate is authorized by the
client (i.e., the domain holder).
If the server agrees to issue the certificate, then it creates the
certificate and provides it in its response. The certificate is
assigned a URI, which the client can use to fetch updated versions of
the certificate.
Client Server
CSR
Signature -------->
<-------- Certificate
To revoke a certificate, the client simply sends a revocation request To revoke a certificate, the client simply sends a revocation request
indicating the certificate to be revoked, signed with an authorized indicating the certificate to be revoked, signed with an authorized
key pair. The server indicates whether the request has succeeded. key pair. The server indicates whether the request has succeeded.
Client Server Client Server
Revocation request Revocation request
Signature --------> Signature -------->
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addressed by this document is the case where domain names are used as addressed by this document is the case where domain names are used as
identifiers. For example, all of the identifier validation identifiers. For example, all of the identifier validation
challenges described in Section 7 below address validation of domain challenges described in Section 7 below address validation of domain
names. The use of ACME for other protocols will require further names. The use of ACME for other protocols will require further
specification, in order to describe how these identifiers are encoded specification, in order to describe how these identifiers are encoded
in the protocol, and what types of validation challenges the server in the protocol, and what types of validation challenges the server
might require. might require.
5. Message Transport 5. Message Transport
ACME uses a combination of HTTPS and JWS to create a messaging layer
with a few important security properties.
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 JWS to provide som additional security properties over HTTPS, using JWS to provide some additional security properties
for messages sent from the client to the server. HTTPS provides for messages sent from the client to the server. HTTPS provides
server authentication and confidentiality. With some ACME-specific server authentication and confidentiality. With some ACME-specific
extensions, JWS provides authentication of the client's request extensions, JWS provides authentication of the client's request
payloads, anti-replay protection, and a degree of integrity for the payloads, anti-replay protection, and integrity for the HTTPS request
HTTPS request URI. URI.
5.1. HTTPS Requests 5.1. HTTPS Requests
Each ACME function is accomplished by the client sending a sequence Each ACME function is accomplished by the client sending a sequence
of HTTPS requests to the server, carrying JSON messages of HTTPS requests to the server, carrying JSON messages
[RFC2818][RFC7159]. Use of HTTPS is REQUIRED. Clients SHOULD [RFC2818][RFC7159]. Use of HTTPS is REQUIRED. Clients SHOULD
support HTTP public key pinning [RFC7469], and servers SHOULD emit support HTTP public key pinning [RFC7469], and servers SHOULD emit
pinning headers. Each subsection of Section 6 below describes the pinning headers. Each subsection of Section 6 below describes the
message formats used by the function, and the order in which messages message formats used by the function, and the order in which messages
are sent. are sent.
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All ACME requests with a non-empty body MUST encapsulate the body in All ACME requests with a non-empty body MUST encapsulate the body in
a JWS object, signed using the account key pair. The server MUST a JWS object, signed using the account key pair. The server MUST
verify the JWS before processing the request. (For readability, verify the JWS before processing the request. (For readability,
however, the examples below omit this encapsulation.) Encapsulating however, the examples below omit this encapsulation.) Encapsulating
request bodies in JWS provides a simple authentication of requests by request bodies in JWS provides a simple authentication of requests by
way of key continuity. way of key continuity.
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 use the Flattened JSON Serialization
o The JWS MUST be encoded using UTF-8 o The JWS MUST be encoded using UTF-8
o The JWS Header or Protected Header MUST include "alg" and "jwk"
fields
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 Protected Header MUST include the "nonce" field (defined o The JWS Protected Header MUST include the following fields:
below)
* "alg"
* "jwk"
* "nonce" (defined below)
* "url" (defined below)
Note that this implies that GET requests are not authenticated. Note that this implies that GET requests are not authenticated.
Servers MUST NOT respond to GET requests for resources that might be Servers MUST NOT respond to GET requests for resources that might be
considered sensitive. considered sensitive.
5.3. Request URI Type Integrity In the examples below, JWS objects are shown in the JSON or flattened
JSON serialization, with the protected header and payload expressed
as base64url(content) instead of the actual base64-encoded value, so
that the content is readable. Some fields are omitted for brevity,
marked with "...".
5.3. Request URI Integrity
It is common in deployment the entity terminating TLS for HTTPS to be It is common in deployment the entity terminating TLS for HTTPS to be
different from the entity operating the logical HTTPS server, with a different from the entity operating the logical HTTPS server, with a
"request routing" layer in the middle. For example, an ACME CA might "request routing" layer in the middle. For example, an ACME CA might
have a content delivery network terminate TLS connections from have a content delivery network terminate TLS connections from
clients so that it can inspect client requests for denial-of-service clients so that it can inspect client requests for denial-of-service
protection. protection.
These intermediaries can also change values in the request that are These intermediaries can also change values in the request that are
not signed in the HTTPS request, e.g., the request URI and headers. not signed in the HTTPS request, e.g., the request URI and headers.
ACME uses JWS to provides a limited integrity mechanism, which ACME uses JWS to provide a limited integrity mechanism, which
protects against an intermediary changing the request URI to anothe protects against an intermediary changing the request URI to another
ACME URI of a different type. (It does not protect against changing ACME URI of a different type. (It does not protect against changing
between URIs of the same type, e.g., from one authorization URI to between URIs of the same type, e.g., from one authorization URI to
another). another).
An ACME request carries a JSON dictionary that provides the details As noted above, all ACME request object carry a "url" parameter in
of the client's request to the server. Each request object MUST have their protected header. This header parameter encodes the URL to
a "resource" field that indicates what type of resource the request which the client is directing the request. On receiving such an
is addressed to, as defined in the below table: object in an HTTP request, the server MUST compare the "url"
parameter to the request URI. If the two do not match, then the
server MUST reject the request as unauthorized.
+--------------------+------------------+ Except for the directory resource, all ACME resources are addressed
| Resource type | "resource" value | with URLs provided to the client by the server. In such cases, the
+--------------------+------------------+ client MUST set the "url" field to the exact string provided by the
| New registration | new-reg | server (rather than performing any re-encoding on the URL).
| | |
| New authorization | new-authz |
| | |
| New certificate | new-cert |
| | |
| Revoke certificate | revoke-cert |
| | |
| Registration | reg |
| | |
| Authorization | authz |
| | |
| Challenge | challenge |
| | |
| Certificate | cert |
+--------------------+------------------+
Other fields in ACME request bodies are described below. 5.3.1. "url" (URL) JWS header parameter
The "url" header parameter specifies the URL to which this JWS object
is directed [RFC3986]. The "url" parameter MUST be carried in the
protected header of the JWS. The value of the "nonce" header MUST be
a JSON string representing the URL.
5.4. Replay protection 5.4. 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 MUST include a Replay-Nonce header field in each An ACME server MUST include a Replay-Nonce header field in each
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The "nonce" header parameter provides a unique value that enables the The "nonce" header parameter provides a unique value that enables the
verifier of a JWS to recognize when replay has occurred. The "nonce" verifier of a JWS to recognize when replay has occurred. The "nonce"
header parameter MUST be carried in the protected header of the JWS. header parameter MUST be carried in the protected header of the JWS.
The value of the "nonce" header parameter MUST be an octet string, The value of the "nonce" header parameter MUST be an octet string,
encoded according to the base64url encoding described in Section 2 of encoded according to the base64url encoding described in Section 2 of
[RFC7515]. If the value of a "nonce" header parameter is not valid [RFC7515]. If the value of a "nonce" header parameter is not valid
according to this encoding, then the verifier MUST reject the JWS as according to this encoding, then the verifier MUST reject the JWS as
malformed. malformed.
5.5. Errors 5.5. Rate limits
Creation of resources can be rate limited to ensure fair usage and
prevent abuse. Once the rate limit is exceeded, the server MUST
respond with an error with the code "rateLimited". Additionally, the
server SHOULD send a "Retry-After" header indicating when the current
request may succeed again. If multiple rate limits are in place,
that is the time where all rate limits allow access again for the
current request with exactly the same parameters.
In addition to the human readable "detail" field of the error
response, the server MAY send one or multiple tokens in the "Link"
header pointing to documentation about the specific hit rate limits
using the "rate-limit" relation.
5.6. Errors
Errors can be reported in ACME both at the HTTP layer and within ACME Errors can be reported in ACME both at the HTTP layer and within ACME
payloads. ACME servers can return responses with an HTTP error payloads. ACME servers can return responses with an HTTP error
response code (4XX or 5XX). For example: If the client submits a response code (4XX or 5XX). For example: If the client submits a
request using a method not allowed in this document, then the server request using a method not allowed in this document, then the server
MAY return status code 405 (Method Not Allowed). MAY return status code 405 (Method Not Allowed).
When the server responds with an error status, it SHOULD provide When the server responds with an error status, it SHOULD provide
additional information using problem document additional information using problem document [RFC7807]. To
[I-D.ietf-appsawg-http-problem]. To facilitate automatic response to facilitate automatic response to errors, this document defines the
errors, this document defines the following standard tokens for use following standard tokens for use in the "type" field (within the
in the "type" field (within the "urn:ietf:params:acme:error:" "urn:ietf:params:acme:error:" namespace):
namespace):
+----------------+--------------------------------------------------+ +-----------------------+-------------------------------------------+
| Code | Description | | Code | Description |
+----------------+--------------------------------------------------+ +-----------------------+-------------------------------------------+
| badCSR | The CSR is unacceptable (e.g., due to a short | | badCSR | The CSR is unacceptable (e.g., due to a |
| | key) | | | short key) |
| | | | | |
| badNonce | The client sent an unacceptable anti-replay | | badNonce | The client sent an unacceptable anti- |
| | nonce | | | replay nonce |
| | | | | |
| connection | The server could not connect to the client for | | connection | The server could not connect to |
| | validation | | | validation target |
| | | | | |
| dnssec | The server could not validate a DNSSEC signed | | dnssec | DNSSEC validation failed |
| | domain | | | |
| | | | caa | CAA records forbid the CA from issuing |
| malformed | The request message was malformed | | | |
| | | | malformed | The request message was malformed |
| serverInternal | The server experienced an internal error | | | |
| | | | serverInternal | The server experienced an internal error |
| tls | The server experienced a TLS error during | | | |
| | validation | | tls | The server received a TLS error during |
| | | | | validation |
| unauthorized | The client lacks sufficient authorization | | | |
| | | | unauthorized | The client lacks sufficient authorization |
| unknownHost | The server could not resolve a domain name | | | |
| | | | unknownHost | The server could not resolve a domain |
| rateLimited | The request exceeds a rate limit | | | name |
| | | | | |
| invalidContact | The provided contact URI for a registration was | | rateLimited | The request exceeds a rate limit |
| | invalid | | | |
+----------------+--------------------------------------------------+ | invalidContact | The contact URI for a registration was |
| | invalid |
| | |
| rejectedIdentifier | The server will not issue for the |
| | identifier |
| | |
| unsupportedIdentifier | Identifier is not supported, but may be |
| | in future |
+-----------------------+-------------------------------------------+
This list is not exhaustive. The server MAY return errors whose This list is not exhaustive. The server MAY return errors whose
"type" field is set to a URI other than those defined above. Servers "type" field is set to a URI other than those defined above. Servers
MUST NOT use the ACME URN namespace for errors other than the MUST NOT use the ACME URN namespace for errors other than the
standard types. Clients SHOULD display the "detail" field of such standard types. Clients SHOULD display the "detail" field of such
errors. errors.
Authorization and challenge objects can also contain error Authorization and challenge objects can also contain error
information to indicate why the server was unable to validate information to indicate why the server was unable to validate
authorization. authorization.
6. Certificate Management 6. Certificate Management
In this section, we describe the certificate management functions In this section, we describe the certificate management functions
that ACME enables: that ACME enables:
o Account Key Registration o Account Key Registration
o Application for a Certificate
o Account Key Authorization o Account Key Authorization
o Certificate Issuance o Certificate Issuance
o Certificate Renewal
o Certificate Revocation o Certificate Revocation
6.1. Resources 6.1. Resources
ACME is structured as a REST application with a few types of ACME is structured as a REST application with a few types of
resources: resources:
o Registration resources, representing information about an account o Registration resources, representing information about an account
o Application resources, represnting an account's requests to issue
certificates
o Authorization resources, representing an account's authorization o Authorization resources, representing an account's authorization
to act for an identifier to act for an identifier
o Challenge resources, representing a challenge to prove control of o Challenge resources, representing a challenge to prove control of
an identifier an identifier
o Certificate resources, representing issued certificates o Certificate resources, representing issued certificates
o A "directory" resource o A "directory" resource
o A "new-registration" resource o A "new-registration" resource
o A "new-authorization" resource o A "new-application" resource
o A "new-certificate" resource
o A "revoke-certificate" resource o A "revoke-certificate" resource
o A "key-change" resource
For the "new-X" resources above, the server MUST have exactly one For the "new-X" resources above, the server MUST have exactly one
resource for each function. This resource may be addressed by resource for each function. This resource may be addressed by
multiple URIs, but all must provide equivalent functionality. multiple URIs, but all must provide equivalent functionality.
ACME uses different URIs for different management functions. Each ACME uses different URIs for different management functions. Each
function is listed in a directory along with its corresponding URI, function is listed in a directory along with its corresponding URI,
so clients only need to be configured with the directory URI. These so clients only need to be configured with the directory URI. These
URIs are connected by a few different link relations [RFC5988]. URIs are connected by a few different link relations [RFC5988].
The "up" link relation is used with challenge resources to indicate The "up" link relation is used with challenge resources to indicate
the authorization resource to which a challenge belongs. It is also the authorization resource to which a challenge belongs. It is also
used from certificate resources to indicate a resource from which the used from certificate resources to indicate a resource from which the
client may fetch a chain of CA certificates that could be used to client may fetch a chain of CA certificates that could be used to
validate the certificate in the original resource. validate the certificate in the original resource.
The "directory" link relation is present on all resources other than The "directory" link relation is present on all resources other than
the directory and indicates the directory URL. the directory and indicates the directory URL.
The following diagram illustrates the relations between resources on The following diagram illustrates the relations between resources on
an ACME server. The solid lines indicate link relations, and the an ACME server. For the most part, these relations are expressed by
dotted lines correspond to relationships expressed in other ways, URLs provided as strings in the resources' JSON representations.
e.g., the Location header in a 201 (Created) response. Lines with labels in quotes indicate HTTP link relations
directory directory
. |
. |
.................................................... ----------------------------------------------------
. . . . | | |
. . . . | | |
V "next" V "next" V V V V V
new-reg ---+----> new-authz ---+----> new-cert revoke-cert new-reg new-app revoke-cert
. | . | . ^ | | ^
. | . | . | "revoke" | | | "revoke"
V | V | V | V V |
reg* ----+ authz -----+ cert-----------+ reg -------------> app -------------> cert ---------+
. ^ | | ^ |
. | "up" | "up" | | "up" | "up"
V | V V | V
challenge cert-chain authz cert-chain
| ^
| | "up"
V |
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.
+--------------------+----------------+--------------+ +--------------------+----------------+------------+
| Action | Request | Response | | Action | Request | Response |
+--------------------+----------------+--------------+ +--------------------+----------------+------------+
| Register | POST new-reg | 201 -> reg | | Register | POST new-reg | 201 -> reg |
| | | | | | | |
| Request challenges | POST new-authz | 201 -> authz | | Apply for a cert | POST new-app | 201 -> app |
| | | | | | | |
| Answer challenges | POST challenge | 200 | | Fetch challenges | GET authz | 200 |
| | | | | | | |
| Poll for status | GET authz | 200 | | Answer challenges | POST challenge | 200 |
| | | | | | | |
| Request issuance | POST new-cert | 201 -> cert | | Poll for status | GET authz | 200 |
| | | | | | | |
| Check for new cert | GET cert | 200 | | Request issuance | POST app | 200 |
+--------------------+----------------+--------------+ | | | |
| Check for new cert | GET cert | 200 |
+--------------------+----------------+------------+
The remainder of this section provides the details of how these The remainder of this section provides the details of how these
resources are structured and how the ACME protocol makes use of them. resources are structured and how the ACME protocol makes use of them.
6.1.1. Registration Objects 6.1.1. Directory
In order to help clients configure themselves with the right URIs for
each ACME operation, ACME servers provide a directory object. This
should be the only URL needed to configure clients. It is a JSON
dictionary, whose keys are drawn from the following table and whose
values are the corresponding URLs.
+-------------+--------------------+
| Key | URL in value |
+-------------+--------------------+
| new-reg | New registration |
| | |
| new-app | New application |
| | |
| revoke-cert | Revoke certificate |
| | |
| key-change | Key change |
+-------------+--------------------+
There is no constraint on the actual URI of the directory except that
it should be different from the other ACME server resources' URIs,
and that it should not clash with other services. For instance:
o a host which function as both an ACME and Web server may want to
keep the root path "/" for an HTML "front page", and and place the
ACME directory under path "/acme".
o a host which only functions as an ACME server could place the
directory under path "/".
The dictionary MAY additionally contain a key "meta". If present, it
MUST be a JSON dictionary; each item in the dictionary is an item of
metadata relating to the service provided by the ACME server.
The following metadata items are defined, all of which are OPTIONAL:
"terms-of-service" (optional, string): A URI identifying the current
terms of service.
"website" (optional, string)): An HTTP or HTTPS URL locating a
website providing more information about the ACME server.
"caa-identities" (optional, array of string): Each string MUST be a
lowercase hostname which the ACME server recognises as referring
to itself for the purposes of CAA record validation as defined in
[RFC6844]. This allows clients to determine the correct issuer
domain name to use when configuring CAA record.
Clients access the directory by sending a GET request to the
directory URI.
HTTP/1.1 200 OK
Content-Type: application/json
{
"new-reg": "https://example.com/acme/new-reg",
"new-app": "https://example.com/acme/new-app",
"revoke-cert": "https://example.com/acme/revoke-cert",
"key-change": "https://example.com/acme/key-change",
"meta": {
"terms-of-service": "https://example.com/acme/terms",
"website": "https://www.example.com/",
"caa-identities": ["example.com"]
}
}
6.1.2. Registration Objects
An ACME registration resource represents a set of metadata associated An ACME registration resource represents a set of metadata associated
to an account key pair. Registration resources have the following to an account key pair. Registration resources have the following
structure: structure:
key (required, dictionary): The public key of the account key pair, key (required, dictionary): The public key of the account key pair,
encoded as a JSON Web Key object [RFC7517]. encoded as a JSON Web Key object [RFC7517].
status (required, string): "good" or "deactivated"
contact (optional, array of string): An array of URIs that the contact (optional, array of string): An array of URIs that the
server can use to contact the client for issues related to this server can use to contact the client for issues related to this
authorization. For example, the server may wish to notify the authorization. For example, the server may wish to notify the
client about server-initiated revocation. client about server-initiated revocation.
agreement (optional, string): A URI referring to a subscriber agreement (optional, string): A URI referring to a subscriber
agreement or terms of service provided by the server (see below). agreement or terms of service provided by the server (see below).
Including this field indicates the client's agreement with the Including this field indicates the client's agreement with the
referenced terms. referenced terms.
authorizations (required, string): A URI from which a list of applications (required, string): A URI from which a list of
authorizations granted to this account can be fetched via a GET authorizations submitted by this account can be fetched via a GET
request. The result of the GET request MUST be a JSON object request. The result of the GET request MUST be a JSON object
whose "authorizations" field is an array of strings, where each whose "applications" field is an array of strings, where each
string is the URI of an authorization belonging to this string is the URI of an authorization belonging to this
registration. The server SHOULD include pending authorizations, registration. The server SHOULD include pending applications, and
and SHOULD NOT include authorizations that are invalid or expired. SHOULD NOT include applications that are invalid. The server MAY
The server MAY return an incomplete list, along with a Link header return an incomplete list, along with a Link header with link
with link relation "next" indicating a URL to retrieve further relation "next" indicating a URL to retrieve further entries.
entries.
certificates (required, string): A URI from which a list of certificates (required, string): A URI from which a list of
certificates issued for this account can be fetched via a GET certificates issued for this account can be fetched via a GET
request. The result of the GET request MUST be a JSON object request. The result of the GET request MUST be a JSON object
whose "certificates" field is an array of strings, where each whose "certificates" field is an array of strings, where each
string is the URI of a certificate. The server SHOULD NOT include string is the URI of a certificate. The server SHOULD NOT include
expired or revoked certificates. The server MAY return an expired or revoked certificates. The server MAY return an
incomplete list, along with a Link header with link relation incomplete list, along with a Link header with link relation
"next" indicating a URL to retrieve further entries. "next" indicating a URL to retrieve further entries.
{ {
"resource": "new-reg",
"contact": [ "contact": [
"mailto:cert-admin@example.com", "mailto:cert-admin@example.com",
"tel:+12025551212" "tel:+12025551212"
], ],
"agreement": "https://example.com/acme/terms", "agreement": "https://example.com/acme/terms",
"authorizations": "https://example.com/acme/reg/1/authz", "authorizations": "https://example.com/acme/reg/1/authz",
"certificates": "https://example.com/acme/reg/1/cert", "certificates": "https://example.com/acme/reg/1/cert"
} }
6.1.2. Authorization Objects 6.1.3. Application Objects
An ACME registration resource represents a client's request for a
certificate, and is used to track the progress of that application
through to issuance. Thus, the object contains information about the
requested certificate, the server's requirements, and any
certificates that have resulted from this application.
status (required, string): The status of this authorization.
Possible values are: "unknown", "pending", "processing", "valid",
and "invalid".
expires (optional, string): The timestamp after which the server
will consider this application invalid, encoded in the format
specified in RFC 3339 [RFC3339]. This field is REQUIRED for
objects with "pending" or "valid" in the status field.
csr (required, string): A CSR encoding the parameters for the
certificate being requested [RFC2986]. The CSR is sent in the
Base64url-encoded version of the DER format. (Note: This field
uses the same modified Base64 encoding rules used elsewhere in
this document, so it is different from PEM.)
notBefore (optional, string): The requested value of the notBefore
field in the certificate, in the date format defined in [RFC3339]
notAfter (optional, string): The requested value of the notAfter
field in the certificate, in the date format defined in [RFC3339]
requirements (required, array): The requirements that the client
needs to fulfill before the requested certificate can be granted
(for pending applications). For final applications, the
requirements that were met. Each entry is a dictionary with
parameters describing the requirement (see below).
certificate (optional, string): A URL for the certificate that has
been issued in response to this application.
{
"status": "pending",
"expires": "2015-03-01T14:09:00Z",
"csr": "jcRf4uXra7FGYW5ZMewvV...rhlnznwy8YbpMGqwidEXfE",
"notBefore": "2016-01-01T00:00:00Z",
"notAfter": "2016-01-08T00:00:00Z",
"requirements": [
{
"type": "authorization",
"status": "valid",
"url": "https://example.com/acme/authz/1234"
},
{
"type": "out-of-band",
"status": "pending",
"url": "https://example.com/acme/payment/1234"
}
]
"certificate": "https://example.com/acme/cert/1234"
}
[[ Open issue: There are two possible behaviors for the CA here.
Either (a) the CA automatically issues once all the requirements are
fulfilled, or (b) the CA waits for confirmation from the client that
it should issue. If we allow both, we will need a signal in the
application object of whether confirmation is required. I would
prefer that auto-issue be the default, which would imply a syntax
like "confirm": true ]]
[[ Open issue: Should this syntax allow multiple certificates? That
would support reissuance / renewal in a straightforward way,
especially if the CSR / notBefore / notAfter could be updated. ]]
The elements of the "requirements" array are immutable once set,
except for their "status" fields. If any other part of the object
changes after the object is created, the client MUST consider the
application invalid.
The "requirements" array in the challenge SHOULD reflect everything
that the CA required the client to do before issuance, even if some
requirements were fulfilled in earlier applications. For example, if
a CA allows multiple applications to be fufilled based on a single
authorization transaction, then it must reflect that authorization in
all of the applications.
Each entry in the "requirements" array expresses a requirement from
the CA for the client to takek a particular action. All requirements
objects have the following basic fields:
type (required, string): The type of requirement (see below for
defined types)
status (required, string): The status of this requirement. Possible
values are: "pending", "valid", and "invalid".
All additional fields are specified by the requirement type.
6.1.3.1. Authorization Requirement
A requirement with type "authorization" requests that the ACME client
complete an authorization transaction. The server specifies the
authorization by pre-provisioning a pending authorization resource
and providing the URI for this resource in the requirement.
url (required, string): The URL for the authorization resource
To fulfill this requirement, the ACME client should fetch the
authorization object from the indicated URL, then follow the process
for obtaining authorization as specified in Section 6.4.
6.1.3.2. Out-of-Band Requirement
A requirement with type "out-of-band" requests that the ACME client
have a human user visit a web page in order to receive further
instructions for how to fulfill the requirement. The requirement
object provides a URI for the web page to be visited.
url (required, string): The URL to be visited. The scheme of this
URL MUST be "http" or "https"
To fulfill this requirement, the ACME client should direct the user
to the indicated web page.
6.1.4. Authorization Objects
An ACME authorization object represents server's authorization for an An ACME authorization object represents server's authorization for an
account to represent an identifier. In addition to the identifier, account to represent an identifier. In addition to the identifier,
an authorization includes several metadata fields, such as the status an authorization includes several metadata fields, such as the status
of the authorization (e.g., "pending", "valid", or "revoked") and of the authorization (e.g., "pending", "valid", or "revoked") and
which challenges were used to validate possession of the identifier. which challenges were used to validate possession of the identifier.
The structure of an ACME authorization resource is as follows: The structure of an ACME authorization resource is as follows:
identifier (required, dictionary of string): The identifier that the identifier (required, dictionary of string): The identifier that the
skipping to change at page 18, line 5 skipping to change at page 22, line 22
status (required, string): The status of this authorization. status (required, string): The status of this authorization.
Possible values are: "unknown", "pending", "processing", "valid", Possible values are: "unknown", "pending", "processing", "valid",
"invalid" and "revoked". If this field is missing, then the "invalid" and "revoked". If this field is missing, then the
default value is "pending". default value is "pending".
expires (optional, string): The timestamp after which the server expires (optional, string): The timestamp after which the server
will consider this authorization invalid, encoded in the format will consider this authorization invalid, encoded in the format
specified in RFC 3339 [RFC3339]. This field is REQUIRED for specified in RFC 3339 [RFC3339]. This field is REQUIRED for
objects with "valid" in the "status field. objects with "valid" in the "status field.
scope (optional, string): If this field is present, then it MUST
contain a URI for an application resource, such that this
authorization is only valid for that resource. If this field is
absent, then the CA MUST consider this authorization valid for all
applications until the authorization expires. [[ Open issue: More
flexible scoping? ]]
challenges (required, array): The challenges that the client needs challenges (required, array): The challenges that the client needs
to fulfill in order to prove possession of the identifier (for to fulfill in order to prove possession of the identifier (for
pending authorizations). For final authorizations, the challenges pending authorizations). For final authorizations, the challenges
that were used. Each array entry is a dictionary with parameters that were used. Each array entry is a dictionary with parameters
required to validate the challenge, as specified in Section 7. required to validate the challenge, as specified in Section 7.
combinations (optional, array of arrays of integers): A collection combinations (optional, array of arrays of integers): A collection
of sets of challenges, each of which would be sufficient to prove of sets of challenges, each of which would be sufficient to prove
possession of the identifier. Clients complete a set of possession of the identifier. Clients complete a set of
challenges that covers at least one set in this array. Challenges challenges that covers at least one set in this array. Challenges
are identified by their indices in the challenges array. If no are identified by their indices in the challenges array. If no
"combinations" element is included in an authorization object, the "combinations" element is included in an authorization object, the
client completes all challenges. client completes all challenges.
The only type of identifier defined by this specification is a fully- The only type of identifier defined by this specification is a fully-
qualified domain name (type: "dns"). The value of the identifier qualified domain name (type: "dns"). The value of the identifier
MUST be the ASCII representation of the domain name. Wildcard domain MUST be the ASCII representation of the domain name. Wildcard domain
names (with "*" as the first label) MUST NOT be included in names (with "*" as the first label) MUST NOT be included in
authorization requests. See Section 6.5 below for more information authorization requests.
about wildcard domains.
{ {
"status": "valid", "status": "valid",
"expires": "2015-03-01T14:09:00Z", "expires": "2015-03-01T14:09:00Z",
"identifier": { "identifier": {
"type": "dns", "type": "dns",
"value": "example.org" "value": "example.org"
}, },
"challenges": [ "challenges": [
{ {
"type": "http-01", "type": "http-01",
"status": "valid", "status": "valid",
"validated": "2014-12-01T12:05:00Z", "validated": "2014-12-01T12:05:00Z",
"keyAuthorization": "SXQe-2XODaDxNR...vb29HhjjLPSggwiE" "keyAuthorization": "SXQe-2XODaDxNR...vb29HhjjLPSggwiE"
} }
], ]
}
6.2. Directory
In order to help clients configure themselves with the right URIs for
each ACME operation, ACME servers provide a directory object. This
should be the only URL needed to configure clients. It is a JSON
dictionary, whose keys are the "resource" values listed in
Section 5.1, and whose values are the URIs used to accomplish the
corresponding function.
There is no constraint on the actual URI of the directory except that
it should be different from the other ACME server resources' URIs,
and that it should not clash with other services. For instance:
o a host which function as both an ACME and Web server may want to
keep the root path "/" for an HTML "front page", and and place the
ACME directory under path "/acme".
o a host which only functions as an ACME server could place the
directory under path "/".
The dictionary MAY additionally contain a key "meta". If present, it
MUST be a JSON dictionary; each item in the dictionary is an item of
metadata relating to the service provided by the ACME server.
The following metadata items are defined, all of which are OPTIONAL:
"terms-of-service" (optional, string): A URI identifying the current
terms of service.
"website" (optional, string)): An HTTP or HTTPS URL locating a
website providing more information about the ACME server.
"caa-identities" (optional, array of string): Each string MUST be a
lowercase hostname which the ACME server recognises as referring
to itself for the purposes of CAA record validation as defined in
[RFC6844]. This allows clients to determine the correct issuer
domain name to use when configuring CAA record.
Clients access the directory by sending a GET request to the
directory URI.
HTTP/1.1 200 OK
Content-Type: application/json
{
"new-reg": "https://example.com/acme/new-reg",
"new-authz": "https://example.com/acme/new-authz",
"new-cert": "https://example.com/acme/new-cert",
"revoke-cert": "https://example.com/acme/revoke-cert",
"meta": {
"terms-of-service": "https://example.com/acme/terms",
"website": "https://www.example.com/",
"caa-identities": ["example.com"]
}
} }
6.3. Registration 6.2. Registration
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-registration URI. The body of the request to the server's new-registration URI. The body of the
request is a stub registration object containing only the "contact" request is a stub registration object containing only the "contact"
field (along with the required "resource" field). field.
POST /acme/new-registration HTTP/1.1 POST /acme/new-reg HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json
{ {
"resource": "new-reg", "protected": base64url({
"contact": [ "alg": "ES256",
"mailto:cert-admin@example.com", "jwk": {...},
"tel:+12025551212" "nonce": "6S8IqOGY7eL2lsGoTZYifg",
], "url": "https://example.com/acme/new-reg"
})
"payload": base64url({
"contact": [
"mailto:cert-admin@example.com",
"tel:+12025551212"
]
}),
"signature": "RZPOnYoPs1PhjszF...-nh6X1qtOFPB519I"
} }
/* Signed as JWS */
The server MUST ignore any values provided in the "key", The server MUST ignore any values provided in the "key",
"authorizations", and "certificates" fields in registration bodies "authorizations", and "certificates" fields in registration bodies
sent by the client, as well as any other fields that it does not sent by the client, as well as any other fields that it does not
recognize. If new fields are specified in the future, the recognize. If new fields are specified in the future, the
specification of those fields MUST describe whether they may be specification of those fields MUST describe whether they may be
provided by the client. provided by the client.
The server creates a registration object with the included contact The server creates a registration object with the included contact
information. The "key" element of the registration is set to the information. The "key" element of the registration is set to the
public key used to verify the JWS (i.e., the "jwk" element of the JWS public key used to verify the JWS (i.e., the "jwk" element of the JWS
header). The server returns this registration object in a 201 header). The server returns this registration object in a 201
(Created) response, with the registration URI in a Location header (Created) response, with the registration URI in a Location header
field. The server SHOULD also indicate its new-authorization URI field.
using the "next" link relation.
If the server already has a registration object with the provided If the server already has a registration object with the provided
account key, then it MUST return a 409 (Conflict) response and account key, then it MUST return a 409 (Conflict) response and
provide the URI of that registration in a Location header field. provide the URI of that registration in a Location header field.
This allows a client that has an account key but not the This allows a client that has an account key but not the
corresponding registration URI to recover the registration URI. corresponding registration URI to recover the registration URI.
If the server wishes to present the client with terms under which the If the server wishes to present the client with terms under which the
ACME service is to be used, it MUST indicate the URI where such terms ACME service is to be used, it MUST indicate the URI where such terms
can be accessed in a Link header with link relation "terms-of- can be accessed in a Link header with link relation "terms-of-
service". As noted above, the client may indicate its agreement with service". As noted above, the client may indicate its agreement with
these terms by updating its registration to include the "agreement" these terms by updating its registration to include the "agreement"
field, with the terms URI as its value. When these terms change in a field, with the terms URI as its value. When these terms change in a
way that requires an agreement update, the server MUST use a way that requires an agreement update, the server MUST use a
different URI in the Link header. different URI in the Link header.
HTTP/1.1 201 Created HTTP/1.1 201 Created
Content-Type: application/json Content-Type: application/json
Location: https://example.com/acme/reg/asdf Location: https://example.com/acme/reg/asdf
Link: <https://example.com/acme/new-authz>;rel="next"
Link: <https://example.com/acme/terms>;rel="terms-of-service" Link: <https://example.com/acme/terms>;rel="terms-of-service"
Link: <https://example.com/acme/some-directory>;rel="directory" Link: <https://example.com/acme/some-directory>;rel="directory"
{ {
"key": { /* JWK from JWS header */ }, "key": { /* JWK from JWS header */ },
"status": "good",
"contact": [ "contact": [
"mailto:cert-admin@example.com", "mailto:cert-admin@example.com",
"tel:+12025551212" "tel:+12025551212"
] ]
} }
If the client wishes to update this information in the future, it If the client wishes to update this information in the future, it
sends a POST request with updated information to the registration sends a POST request with updated information to the registration
URI. The server MUST ignore any updates to the "key", URI. The server MUST ignore any updates to the "key",
"authorizations, or "certificates" fields, and MUST verify that the "authorizations, or "certificates" fields, and MUST verify that the
request is signed with the private key corresponding to the "key" request is signed with the private key corresponding to the "key"
field of the request before updating the registration. field of the request before updating the registration.
For example, to update the contact information in the above For example, to update the contact information in the above
registration, the client could send the following request: registration, the client could send the following request:
POST /acme/reg/asdf HTTP/1.1 POST /acme/reg/asdf HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json
{ {
"resource": "reg", "protected": base64url({
"contact": [ "alg": "ES256",
"mailto:certificates@example.com", "jwk": {...},
"tel:+12125551212" "nonce": "ax5RnthDqp_Yf4_HZnFLmA",
], "url": "https://example.com/acme/reg/asdf"
})
"payload": base64url({
"contact": [
"mailto:certificates@example.com",
"tel:+12125551212"
]
}),
"signature": "hDXzvcj8T6fbFbmn...rDzXzzvzpRy64N0o"
} }
/* Signed as JWS */
Servers SHOULD NOT respond to GET requests for registration resources Servers SHOULD NOT respond to GET requests for registration resources
as these requests are not authenticated. If a client wishes to query as these requests are not authenticated. If a client wishes to query
the server for information about its account (e.g., to examine the the server for information about its account (e.g., to examine the
"contact" or "certificates" fields), then it SHOULD do so by sending "contact" or "certificates" fields), then it SHOULD do so by sending
a POST request with an empty update. That is, it should send a JWS a POST request with an empty update. That is, it should send a JWS
whose payload is trivial ({"resource":"reg"}). In this case the whose payload is trivial ({}).
server reply MUST contain the same link headers sent for a new
registration, to allow a client to retrieve the "new-authorization"
and "terms-of-service" URI
6.3.1. Account Key Roll-over 6.2.1. Account Key Roll-over
A client may wish to change the public key that is associated with a A client may wish to change the public key that is associated with a
registration, e.g., in order to mitigate the risk of key compromise. registration in order to recover from a key compromise or proactively
To do this, the client first constructs a JSON object representing a mitigate the impact of an unnoticed key compromise.
request to update the registration:
resource (required, string): The string "reg", indicating an update To change the key associate with an account, the client sends a POST
to the registration. request containing a key-change object with the following fields:
oldKey (required, string): The JWK thumbprint of the old key oldKey (required, JWK): The JWK representation of the original key
[RFC7638], base64url-encoded (i.e., the client's current account key)
newKey (requrired, JWK): The JWK representation of the new key
The JWS of this POST must have two signatures: one signature from the
existing key on the account, and one signature from the new key that
the client proposes to use. This demonstrates that the client
actually has control of the private key corresponding to the new
public key. The protected header must contain a JWK field containing
the current account key.
POST /acme/key-change HTTP/1.1
Host: example.com
Content-Type: application/jose+json
{ {
"resource": "reg", "payload": base64url({
"oldKey": "D7J9RL1f-RWUl68JP-gW1KSl2TkIrJB7hK6rLFFeYMU" "oldKey": /* Old key in JWK form */
"newKey": /* New key in JWK form */
}),
"signatures": [{
"protected": base64url({
"alg": "ES256",
"jwk": /* old key */,
"nonce": "pq00v-D1KB0sReG4jFfqVg",
"url": "https://example.com/acme/key-change"
}),
"signature": "XFvVbo9diBlIBvhE...UI62sNT6MZsCJpQo"
}, {
"protected": base64url({
"alg": "ES256",
"jwk": /* new key */,
"nonce": "vYjyueEYhMjpVQHe_unw4g",
"url": "https://example.com/acme/key-change"
}),
"signature": "q20gG1f1r9cD6tBM...a48h0CkP11tl5Doo"
}]
} }
The client signs this object with the new key pair and encodes the On receiving key-change request, the server MUST perform the
object and signature as a JWS. The client then sends this JWS to the following steps in addition to the typical JWS validation:
server in the "newKey" field of a request to update the registration.
1. Check that the JWS protected header container a "jwk" field
containing a key that matches a currently active account.
2. Check that there are exactly two signatures on the JWS.
3. Check that one of the signatures validates using the account key
from (1).
4. Check that the "key" field contains a well-formed JWK that meets
key strength requirements.
5. Check that the "key" field is not equivalent to the current
account key or any other currently active account key.
6. Check that one of the two signatures on the JWS validates using
the JWK from the "key" field.
If all of these checks pass, then the server updates the
corresponding registration by replacing the old account key with the
new public key and returns status code 200. Otherwise, the server
responds with an error status code and a problem document describing
the error.
6.2.2. Account deactivation
A client may deactivate an account by posting a signed update to the
server with a status field of "deactivated." Clients may wish to do
this when the account key is compromised.
POST /acme/reg/asdf HTTP/1.1 POST /acme/reg/asdf HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json
{ {
"resource": "reg", "protected": base64url({
"newKey": /* JSON object signed as JWS with new key */ "alg": "ES256",
"jwk": {...},
"nonce": "ntuJWWSic4WVNSqeUmshgg",
"url": "https://example.com/acme/reg/asdf"
})
"payload": base64url({
"status": "deactivated"
}),
"signature": "earzVLd3m5M4xJzR...bVTqn7R08AKOVf3Y"
} }
/* Signed as JWS with original key */
On receiving a request to the registration URL with the "newKey"
attribute set, the server MUST perform the following steps:
1. Check that the contents of the "newKey" attribute are a valid JWS The server MUST verify that the request is signed by the account key.
If the server accepts the deactivation request, it should reply with
a 200 (OK) status code and the current contents of the registration
object.
2. Check that the "newKey" JWS verifies using the key in the "jwk" Once an account is deactivated, the server MUST NOT accept further
header parameter of the JWS requests authorized by that account's key. It is up to server policy
how long to retain data related to that account, whether to revoke
certificates issued by that account, and whether to send email to
that account's contacts. ACME does not provide a way to reactivate a
deactivated account.
3. Check that the payload of the JWS is a valid JSON object 6.3. Applying for Certificate Issuance
4. Check that the "resource" field of the object has the value "reg" The holder of an account key pair may use ACME to submit an
application for a certificate to be issued. The client makes this
request by sending a POST request to the server's new-application
resource. The body of the POST is a JWS object whose JSON payload is
a subset of the application object defined in Section 6.1.3,
containing the fields that describe the certificate to be issued:
5. Check that the "oldKey" field of the object contains the JWK csr (required, string): A CSR encoding the parameters for the
thumbprint of the account key for this registration certificate being requested [RFC2986]. The CSR is sent in the
Base64url-encoded version of the DER format. (Note: This field
uses the same modified Base64 encoding rules used elsewhere in
this document, so it is different from PEM.)
If all of these checks pass, then the server updates the registration notBefore (optional, string): The requested value of the notBefore
by replacing the old account key with the public key carried in the field in the certificate, in the date format defined in [RFC3339]
"jwk" header parameter of the "newKey" JWS object.
If the update was successful, then the server sends a response with notAfter (optional, string): The requested value of the notAfter
status code 200 (OK) and the updated registration object as its body. field in the certificate, in the date format defined in [RFC3339]
If the update was not successful, then the server responds with an
error status code and a problem document describing the error.
6.3.2. Deleting an Account POST /acme/new-app HTTP/1.1
Host: example.com
Content-Type: application/jose+json
If a client no longer wishes to have an account key registered with {
the server, it may request that the server delete its account by "protected": base64url({
sending a POST request to the account URI containing the "delete" "alg": "ES256",
field. "jwk": {...},
"nonce": "5XJ1L3lEkMG7tR6pA00clA",
"url": "https://example.com/acme/new-app"
})
"payload": base64url({
"csr": "5jNudRx6Ye4HzKEqT5...FS6aKdZeGsysoCo4H9P",
"notBefore": "2016-01-01T00:00:00Z",
"notAfter": "2016-01-08T00:00:00Z"
}),
"signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g"
}
delete (required, boolean): The boolean value "true". The CSR encodes the client's requests with regard to the content of
the certificate to be issued. The CSR MUST indicate the requested
identifiers, either in the commonName portion of the requested
subject name, or in an extensionRequest attribute [RFC2985]
requesting a subjectAltName extension.
The request object MUST contain the "resource" field as required The server MUST return an error if it cannot fulfil the request as
above (with the value "reg"). It MUST NOT contain any fields besides specified, and MUST NOT issue a certificate with contents other than
"resource" and "delete". those requested. If the server requires the request to be modified
in a certain way, it should indicate the required changes using an
appropriate error code and description.
Note that although this object is very simple, the risk of replay or If the server is willing to issue the requested certificate, it
fraudulent generation via signing oracles is mitigated by the need responds with a 201 (Created) response. The body of this response is
for an anti-replay token in the protected header of the JWS. an application object reflecting the client's request and any
requirements the client must fulfill before the certificate will be
issued.
POST /acme/reg/asdf HTTP/1.1 HTTP/1.1 201 Created
Host: example.com Location: https://example.com/acme/app/asdf
{ {
"resource": "reg", "status": "pending",
"delete": true, "expires": "2015-03-01T14:09:00Z",
"csr": "jcRf4uXra7FGYW5ZMewvV...rhlnznwy8YbpMGqwidEXfE",
"notBefore": "2016-01-01T00:00:00Z",
"notAfter": "2016-01-08T00:00:00Z",
"requirements": [
{
"type": "authorization",
"status": "valid",
"url": "https://example.com/acme/authz/1234"
},
{
"type": "out-of-band",
"status": "pending",
"url": "https://example.com/acme/payment/1234"
}
]
} }
/* Signed as JWS */
On receiving a POST to an account URI containing a "delete" field, The application object returned by the server represents a promise
the server MUST verify that no other fields were sent in the object that if the client fulfills the server's requirements before the
(other than "resource"), and it MUST verify that the value of the "expires" time, then the server will issue the requested certificate.
"delete" field is "true" (as a boolean, not a string). If either of In the application object, any object in the "requirements" array
these checks fails, then the server MUST reject the request with whose status is "pending" represents an action that the client must
status code 400 (Bad Request). perform before the server will issue the certificate. If the client
fails to complete the required actions before the "expires" time,
then the server SHOULD change the status of the application to
"invalid" and MAY delete the application resource.
If the server accepts the deletion request, then it MUST delete the The server SHOULD issue the requested certificate and update the
account and all related objects and send a response with a 200 (OK) application resource with a URL for the certificate as soon as the
status code and an empty body. The server SHOULD delete any client has fulfilled the server's requirements. If the client has
authorization objects related to the deleted account, since they can already satisfied the server's requirements at the time of this
no longer be used. The server SHOULD NOT delete certificate objects request (e.g., by obtaining authorization for all of the identifiers
related to the account, since certificates issued under the account in the certificate in previous transactions), then the server MAY
continue to be valid until they expire or are revoked. proactively issue the requested certificate and provide a URL for it
in the "certificate" field of the application. The server MUST,
however, still list the satisfied requirements in the "requirements"
array, with the state "valid".
Once the client believes it has fulfilled the server's requirements,
it should send a GET request to the application resource to obtain
its current state. The status of the application will indicate what
action the client should take:
o "invalid": The certificate will not be issued. Consider this
application process abandoned.
o "pending": The server does not believe that the client has
fulfilled the requirements. Check the "requirements" array for
requirements that are still pending.
o "processing": The server agrees that the requirements have been
fulfilled, and is in the process of generating the certificate.
Retry after the time given in the "Retry-After" header field of
the response, if any.
o "valid": The server has issued the certificate and provisioned its
URL to the "certificate" field of the application. Download the
certificate.
6.3.1. Downloading the Certificate
To download the issued certificate, the client simply sends a GET
request to the certificate URL.
The default format of the certificate is DER (application/pkix-cert).
The client may request other formats by including an Accept header in
its request. For example, the client may use the media type
application/x-pem-file to request the certificate in PEM format.
The server provides metadata about the certificate in HTTP headers.
In particular, the server MUST send one or more link relation header
fields [RFC5988] with relation "up", each indicating a single
certificate resource for the issuer of this certificate. The server
MAY also include the "up" links from these resources to enable the
client to build a full certificate chain.
The server MUST also provide a link relation header field with
relation "author" to indicate the application under which this
certificate was issued.
If the CA participates in Certificate Transparency (CT) [RFC6962],
then they may want to provide the client with a Signed Certificate
Timestamp (SCT) that can be used to prove that a certificate was
submitted to a CT log. An SCT can be included as an extension in the
certificate or as an extension to OCSP responses for the certificate.
The server can also provide the client with direct access to an SCT
for a certificate using a Link relation header field with relation
"ct-sct".
GET /acme/cert/asdf HTTP/1.1
Host: example.com
Accept: application/pkix-cert
HTTP/1.1 200 OK
Content-Type: application/pkix-cert
Link: <https://example.com/acme/ca-cert>;rel="up";title="issuer"
Link: <https://example.com/acme/revoke-cert>;rel="revoke"
Link: <https://example.com/acme/app/asdf>;rel="author"
Link: <https://example.com/acme/sct/asdf>;rel="ct-sct"
Link: <https://example.com/acme/some-directory>;rel="directory"
[DER-encoded certificate]
A certificate resource represents a single, immutable certificate.
If the client wishes to obtain a renewed certificate, the client
initiates a new application process to request one.
Because certificate resources are immutable once issuance is
complete, the server MAY enable the caching of the resource by adding
Expires and Cache-Control headers specifying a point in time in the
distant future. These headers have no relation to the certificate's
period of validity.
6.4. Identifier Authorization 6.4. Identifier Authorization
The identifier authorization process establishes the authorization of The identifier authorization process establishes the authorization of
an account to manage certificates for a given identifier. This an account to manage certificates for a given identifier. This
process must assure the server of two things: First, that the client process must assure the server of two things: First, that the client
controls the private key of the account key pair, and second, that controls the private key of the account key pair, and second, that
the client holds the identifier in question. This process may be the client holds the identifier in question. This process may be
repeated to associate multiple identifiers to a key pair (e.g., to repeated to associate multiple identifiers to a key pair (e.g., to
request certificates with multiple identifiers), or to associate request certificates with multiple identifiers), or to associate
multiple accounts with an identifier (e.g., to allow multiple multiple accounts with an identifier (e.g., to allow multiple
entities to manage certificates). entities to manage certificates). The server may declare that an
authorization is only valid for a specific application by setting the
As illustrated by the figure in the overview section above, the "scope" field of the authorization to the URI for that application.
authorization process proceeds in two phases. The client first
requests a new authorization, and the server issues challenges, then
the client responds to those challenges and the server validates the
client's responses.
To begin the key authorization process, the client sends a POST Authorization resources are created by the server in response to
request to the server's new-authorization resource. The body of the certificate applications submitted by an account key holder; their
POST request MUST contain a JWS object, whose payload is a partial URLs are provided to the client in "authorization" requirement
authorization object. This JWS object MUST contain only the objects. The authorization object is implicitly tied to the account
"identifier" field, so that the server knows what identifier is being key used to sign the new-application request.
authorized. The server MUST ignore any other fields present in the
client's request object.
The authorization object is implicitly tied to the account key used When a client receives an application from the server with an
to sign the request. Once created, the authorization may only be "authorization" requirement, it downloads the authorization resource
updated by that account. by sending a GET request to the indicated URL.
POST /acme/new-authorization HTTP/1.1 GET /acme/authz/1234 HTTP/1.1
Host: example.com Host: example.com
{ HTTP/1.1 200 OK
"resource": "new-authz",
"identifier": {
"type": "dns",
"value": "example.org"
}
}
/* Signed as JWS */
Before processing the authorization further, the server SHOULD
determine whether it is willing to issue certificates for the
identifier. For example, the server should check that the identifier
is of a supported type. Servers might also check names against a
blacklist of known high-value identifiers. If the server is
unwilling to issue for the identifier, it SHOULD return a 403
(Forbidden) error, with a problem document describing the reason for
the rejection.
If the server is willing to proceed, it builds a pending
authorization object from the initial authorization object submitted
by the client.
o "identifier" the identifier submitted by the client
o "status": MUST be "pending" unless the server has out-of-band
information about the client's authorization status
o "challenges" and "combinations": As selected by the server's
policy for this identifier
The server allocates a new URI for this authorization, and returns a
201 (Created) response, with the authorization URI in a Location
header field, and the JSON authorization object in the body.
HTTP/1.1 201 Created
Content-Type: application/json Content-Type: application/json
Location: https://example.com/authz/asdf
Link: <https://example.com/acme/new-cert>;rel="next"
Link: <https://example.com/acme/some-directory>;rel="directory" Link: <https://example.com/acme/some-directory>;rel="directory"
{ {
"status": "pending", "status": "pending",
"identifier": { "identifier": {
"type": "dns", "type": "dns",
"value": "example.org" "value": "example.org"
}, },
skipping to change at page 26, line 30 skipping to change at page 32, line 43
{ {
"type": "http-01", "type": "http-01",
"uri": "https://example.com/authz/asdf/0", "uri": "https://example.com/authz/asdf/0",
"token": "IlirfxKKXAsHtmzK29Pj8A" "token": "IlirfxKKXAsHtmzK29Pj8A"
}, },
{ {
"type": "dns-01", "type": "dns-01",
"uri": "https://example.com/authz/asdf/1", "uri": "https://example.com/authz/asdf/1",
"token": "DGyRejmCefe7v4NfDGDKfA" "token": "DGyRejmCefe7v4NfDGDKfA"
} }
}, ],
"combinations": [[0], [1]] "combinations": [[0], [1]]
} }
6.4.1. Responding to Challenges 6.4.1. Responding to Challenges
To prove control of the identifer and receive authorization, the To prove control of the identifier and receive authorization, the
client needs to respond with information to complete the challenges. client needs to respond with information to complete the challenges.
To do this, the client updates the authorization object received from To do this, the client updates the authorization object received from
the server by filling in any required information in the elements of the server by filling in any required information in the elements of
the "challenges" dictionary. (This is also the stage where the the "challenges" dictionary. (This is also the stage where the
client should perform any actions required by the challenge.) client should perform any actions required by the challenge.)
The client sends these updates back to the server in the form of a The client sends these updates back to the server in the form of a
JSON object with the response fields required by the challenge type, JSON object with the response fields required by the challenge type,
carried in a POST request to the challenge URI (not authorization URI carried in a POST request to the challenge URI (not authorization
or the new-authorization URI). This allows the client to send URI). This allows the client to send information only for challenges
information only for challenges it is responding to. it is responding to.
For example, if the client were to respond to the "http-01" challenge For example, if the client were to respond to the "http-01" challenge
in the above authorization, it would send the following request: in the above authorization, it would send the following request:
POST /acme/authz/asdf/0 HTTP/1.1 POST /acme/authz/asdf/0 HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json
{ {
"resource": "challenge", "protected": base64url({
"type": "http-01", "alg": "ES256",
"keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE" "jwk": {...},
"nonce": "Q_s3MWoqT05TrdkM2MTDcw",
"url": "https://example.com/acme/authz/asdf/0"
})
"payload": base64url({
"type": "http-01",
"keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE"
}),
"signature": "9cbg5JO1Gf5YLjjz...SpkUfcdPai9uVYYQ"
} }
/* Signed as JWS */
The server updates the authorization document by updating its The server updates the authorization document by updating its
representation of the challenge with the response fields provided by representation of the challenge with the response fields provided by
the client. The server MUST ignore any fields in the response object the client. The server MUST ignore any fields in the response object
that are not specified as response fields for this type of challenge. that are not specified as response fields for this type of challenge.
The server provides a 200 (OK) response with the updated challenge The server provides a 200 (OK) response with the updated challenge
object as its body. object as its body.
If the client's response is invalid for some reason, or does not If the client's response is invalid for some reason, or does not
provide the server with appropriate information to validate the provide the server with appropriate information to validate the
skipping to change at page 28, line 32 skipping to change at page 35, line 30
{ {
"type": "http-01" "type": "http-01"
"status": "valid", "status": "valid",
"validated": "2014-12-01T12:05:00Z", "validated": "2014-12-01T12:05:00Z",
"token": "IlirfxKKXAsHtmzK29Pj8A", "token": "IlirfxKKXAsHtmzK29Pj8A",
"keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE" "keyAuthorization": "IlirfxKKXA...vb29HhjjLPSggwiE"
} }
] ]
} }
6.4.2. Deleting an Authorization 6.4.2. 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
delete the authorization. The client makes this request by sending a deactivate each authorization associated with that identifier by
POST request to the authorization URI containing a payload in the sending a POST request with the static object {"status":
same format as in Section 6.3.2. The only difference is that the "deactivated"}.
value of the "resource" field is "authz".
POST /acme/authz/asdf HTTP/1.1 POST /acme/authz/asdf HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/jose+json
{ {
"resource": "authz", "protected": base64url({
"delete": true, "alg": "ES256",
} "jwk": {...},
/* Signed as JWS */ "nonce": "xWCM9lGbIyCgue8di6ueWQ",
"url": "https://example.com/acme/authz/asdf"
The server MUST perform the same validity checks as in Section 6.3.2 })
and reject the request if they fail. If the server deletes the "payload": base64url({
account then it MUST send a response with a 200 (OK) status code and "status": "deactivated"
an empty body. }),
"signature": "srX9Ji7Le9bjszhu...WTFdtujObzMtZcx4"
6.5. Certificate Issuance
The holder of an account key pair authorized for one or more
identifiers may use ACME to request that a certificate be issued for
any subset of those identifiers. The client makes this request by
sending a POST request to the server's new-certificate resource. The
body of the POST is a JWS object whose JSON payload contains a
Certificate Signing Request (CSR) [RFC2986]. The CSR encodes the
parameters of the requested certificate; authority to issue is
demonstrated by the JWS signature by an account key, from which the
server can look up related authorizations. Some attributes which
cannot be reflected in a CSR are placed directly in the certificate
request.
csr (required, string): A CSR encoding the parameters for the
certificate being requested. The CSR is sent in the Base64url-
encoded version of the DER format. (Note: This field uses the
same modified Base64 encoding rules used elsewhere in this
document, so it is different from PEM.)
notBefore (optional, string): The requested value of the notBefore
field in the certificate, in the date format defined in [RFC3339]
notAfter (optional, string): The requested value of the notAfter
field in the certificate, in the date format defined in [RFC3339]
POST /acme/new-cert HTTP/1.1
Host: example.com
Accept: application/pkix-cert
{
"resource": "new-cert",
"csr": "5jNudRx6Ye4HzKEqT5...FS6aKdZeGsysoCo4H9P",
"notBefore": "2016-01-01T00:00:00Z",
"notAfter": "2016-01-08T00:00:00Z"
} }
/* Signed as JWS */
The CSR encodes the client's requests with regard to the content of
the certificate to be issued. The CSR MUST indicate the requested
identifiers, either in the commonName portion of the requested
subject name, or in an extensionRequest attribute [RFC2985]
requesting a subjectAltName extension.
The values provided in the CSR are only a request, and are not
guaranteed. The server SHOULD return an error if it cannot fulfil
the request as specified, but MAY issue a certificate with contents
other than those requested, according to its local policy (e.g.,
removing identifiers for which the client is not authorized).
It is up to the server's local policy to decide which names are
acceptable in a certificate, given the authorizations that the server
associates with the client's account key. A server MAY consider a
client authorized for a wildcard domain if it is authorized for the
underlying domain name (without the "*" label). Servers SHOULD NOT
extend authorization across identifier types. For example, if a
client is authorized for "example.com", then the server should not
allow the client to issue a certificate with an iPAddress
subjectAltName, even if it contains an IP address to which
example.com resolves.
If the CA decides to issue a certificate, then the server creates a
new certificate resource and returns a URI for it in the Location
header field of a 201 (Created) response.
HTTP/1.1 201 Created
Location: https://example.com/acme/cert/asdf
If the certificate is available at the time of the response, it is
provided in the body of the response. If the CA has not yet issued
the certificate, the body of this response will be empty. The client
should then send a GET request to the certificate URI to poll for the
certificate. As long as the certificate is unavailable, the server
MUST provide a 202 (Accepted) response and include a Retry-After
header to indicate when the server believes the certificate will be
issued (as in the example above).
GET /acme/cert/asdf HTTP/1.1
Host: example.com
Accept: application/pkix-cert
HTTP/1.1 202 Accepted
Retry-After: 120
The default format of the certificate is DER (application/pkix-cert).
The client may request other formats by including an Accept header in
its request.
The server provides metadata about the certificate in HTTP headers. The server MUST verify that the request is signed by the account key
In particular, the server MUST include a Link relation header field corresponding to the account that owns the authorization. If the
[RFC5988] with relation "up" to provide a certificate under which server accepts the deactivation, it should reply with a 200 (OK)
this certificate was issued, and one with relation "author" to status code and the current contents of the registration object.
indicate the registration under which this certificate was issued.
The server MAY include an Expires header as a hint to the client
about when to renew the certificate. (Of course, the real expiration
of the certificate is controlled by the notAfter time in the
certificate itself.)
If the CA participates in Certificate Transparency (CT) [RFC6962],
then they may want to provide the client with a Signed Certificate
Timestamp (SCT) that can be used to prove that a certificate was
submitted to a CT log. An SCT can be included as an extension in the
certificate or as an extension to OCSP responses for the certificate.
The server can also provide the client with direct access to an SCT
for a certificate using a Link relation header field with relation
"ct-sct".
GET /acme/cert/asdf HTTP/1.1
Host: example.com
Accept: application/pkix-cert
HTTP/1.1 200 OK
Content-Type: application/pkix-cert
Link: <https://example.com/acme/ca-cert>;rel="up";title="issuer"
Link: <https://example.com/acme/revoke-cert>;rel="revoke"
Link: <https://example.com/acme/reg/asdf>;rel="author"
Link: <https://example.com/acme/sct/asdf>;rel="ct-sct"
Link: <https://example.com/acme/some-directory>;rel="directory"
Location: https://example.com/acme/cert/asdf
Content-Location: https://example.com/acme/cert-seq/12345
[DER-encoded certificate]
A certificate resource always represents the most recent certificate
issued for the name/key binding expressed in the CSR. If the CA
allows a certificate to be renewed, then it publishes renewed
versions of the certificate through the same certificate URI.
Clients retrieve renewed versions of the certificate using a GET
query to the certificate URI, which the server should then return in
a 200 (OK) response. The server SHOULD provide a stable URI for each
specific certificate in the Content-Location header field, as shown
above. Requests to stable certificate URIs MUST always result in the
same certificate.
To avoid unnecessary renewals, the CA may choose not to issue a
renewed certificate until it receives such a request (if it even
allows renewal at all). In such cases, if the CA requires some time
to generate the new certificate, the CA MUST return a 202 (Accepted)
response, with a Retry-After header field that indicates when the new
certificate will be available. The CA MAY include the current (non-
renewed) certificate as the body of the response.
Likewise, in order to prevent unnecessary renewal due to queries by
parties other than the account key holder, certificate URIs should be
structured as capability URLs [W3C.WD-capability-urls-20140218].
From the client's perspective, there is no difference between a The server MUST NOT treat deactivated authorization objects as
certificate URI that allows renewal and one that does not. If the sufficient for issuing certificates.
client wishes to obtain a renewed certificate, and a GET request to
the certificate URI does not yield one, then the client may initiate
a new-certificate transaction to request one.
6.6. Certificate Revocation 6.5. Certificate Revocation
To request that a certificate be revoked, the client sends a POST To request that a certificate be revoked, the client sends a POST
request to the ACME server's revoke-cert URI. The body of the POST request to the ACME server's revoke-cert URI. The body of the POST
is a JWS object whose JSON payload contains the certificate to be is a JWS object whose JSON payload contains the certificate to be
revoked: revoked:
certificate (required, string): The certificate to be revoked, in certificate (required, string): The certificate to be revoked, in
the base64url-encoded version of the DER format. (Note: This the base64url-encoded version of the DER format. (Note: This
field uses the same modified Base64 encoding rules used elsewhere field uses the same modified Base64 encoding rules used elsewhere
in this document, so it is different from PEM.) in this document, so it is different from PEM.)
reason (optional, int): One of the revocation reasonCodes defined in
RFC 5280 [RFC5280] Section 5.3.1 to be used when generating OCSP
responses and CRLs. If this field is not set the server SHOULD
use the unspecified (0) reasonCode value when generating OCSP
responses and CRLs. The server MAY disallow a subset of
reasonCodes from being used by the user.
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
{ {
"resource": "revoke-cert", "protected": base64url({
"certificate": "MIIEDTCCAvegAwIBAgIRAP8..." "alg": "ES256",
"jwk": {...},
"nonce": "JHb54aT_KTXBWQOzGYkt9A",
"url": "https://example.com/acme/revoke-cert"
})
"payload": base64url({
"certificate": "MIIEDTCCAvegAwIBAgIRAP8...",
"reason": 1
}),
"signature": "Q1bURgJoEslbD1c5...3pYdSMLio57mQNN4"
} }
/* Signed as JWS */
Revocation requests are different from other ACME request in that Revocation requests are different from other ACME request in that
they can be signed either with an account key pair or the key pair in they can be signed either with an account key pair or the key pair in
the certificate. Before revoking a certificate, the server MUST the certificate. Before revoking a certificate, the server MUST
verify that the key used to sign the request is authorized to revoke verify that the key used to sign the request is authorized to revoke
the certificate. The server SHOULD consider at least the following the certificate. The server SHOULD consider at least the following
keys authorized for a given certificate: keys authorized for a given certificate:
o the public key in the certificate. o the public key in the certificate.
skipping to change at page 33, line 41 skipping to change at page 38, line 23
Challenges provide the server with assurance that an account key Challenges provide the server with assurance that an account key
holder is also the entity that controls an identifier. For each type holder is also the entity that controls an identifier. For each type
of challenge, it must be the case that in order for an entity to of challenge, it must be the case that in order for an entity to
successfully complete the challenge the entity must both: successfully complete the challenge the entity must both:
o Hold the private key of the account key pair used to respond to o Hold the private key of the account key pair used to respond to
the challenge the challenge
o Control the identifier in question o Control the identifier in question
Section 10 documents how the challenges defined in this document meet Section 9 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 challenge in the validation. The server presents a set of challenges in the
authorization object it sends to a client (as objects in the authorization object it sends to a client (as objects in the
"challenges" array), and the client responds by sending a response "challenges" array), and the client responds by sending a response
object in a POST request to a challenge URI. object in a POST request to a challenge URI.
This section describes an initial set of challenge types. Each This section describes an initial set of challenge types. Each
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
skipping to change at page 34, line 20 skipping to change at page 38, line 51
of an identifier of an identifier
Challenge objects all contain the following basic fields: Challenge objects all contain the following basic fields:
type (required, string): The type of challenge encoded in the type (required, string): The type of challenge encoded in the
object. object.
uri (required, string): The URI to which a response can be posted. uri (required, string): The URI 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". If this Possible values are: "pending", "valid", and "invalid".
field is missing, then the default value is "pending".
validated (optional, string): The time at which this challenge was validated (optional, string): The time at which this challenge was
completed by the server, encoded in the format specified in RFC completed by the server, encoded in the format specified in RFC
3339 [RFC3339]. This field is REQUIRED if the "status" field is 3339 [RFC3339]. This field is REQUIRED if the "status" field is
"valid". "valid".
error (optional, dictionary of string): The error that occurred error (optional, dictionary of string): The error that occurred
while the server was validating the challenge, if any. This field while the server was validating the challenge, if any. This field
is structured as a problem document is structured as a problem document [RFC7807].
[I-D.ietf-appsawg-http-problem].
All additional fields are specified by the challenge type. If the All additional fields are specified by the challenge type. If the
server sets a challenge's "status" to "invalid", it SHOULD also server sets a challenge's "status" to "invalid", it SHOULD also
include the "error" field to help the client diagnose why they failed include the "error" field to help the client diagnose why they failed
the challenge. the challenge.
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 HTTP aspects of control over an identifier. In some challenges, like HTTP
and TLS SNI, the client directly proves its ability to do certain and TLS SNI, the client directly proves its ability to do certain
things related to the identifier. The choice of which challenges to things related to the identifier. The choice of which challenges to
skipping to change at page 36, line 7 skipping to change at page 40, line 36
7.2. HTTP 7.2. HTTP
With HTTP validation, the client in an ACME transaction proves its With HTTP validation, the client in an ACME transaction proves its
control over a domain name by proving that it can provision resources control over a domain name by proving that it can provision resources
on an HTTP server that responds for that domain name. The ACME on an HTTP server that responds for that domain name. The ACME
server challenges the client to provision a file at a specific path, server challenges the client to provision a file at a specific path,
with a specific string as its content. with a specific string as its content.
As a domain may resolve to multiple IPv4 and IPv6 addresses, the As a domain may resolve to multiple IPv4 and IPv6 addresses, the
server will connect to at least one of the hosts found in A and AAAA server will connect to at least one of the hosts found in A and AAAA
records. Because many web servers allocate a default HTTPS virtual records, at its discretion. Because many webservers allocate a
host to a particular low-privilege tenant user in a subtle and non- default HTTPS virtual host to a particular low-privilege tenant user
intuitive manner, the challenge must be completed over HTTP, not in a subtle and non-intuitive manner, the challenge must be completed
HTTPS. over HTTP, not HTTPS.
type (required, string): The string "http-01" type (required, string): The string "http-01"
token (required, string): A random value that uniquely identifies token (required, string): A random value that uniquely identifies
the challenge. This value MUST have at least 128 bits of entropy, the challenge. This value MUST have at least 128 bits of entropy,
in order to prevent an attacker from guessing it. It MUST NOT in order to prevent an attacker from guessing it. It MUST NOT
contain any characters outside the URL-safe Base64 alphabet and contain any characters outside the URL-safe Base64 alphabet and
MUST NOT contain any padding characters ("="). MUST NOT contain any padding characters ("=").
{ {
"type": "http-01", "type": "http-01",
"token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA", "token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA"
} }
A client responds to this challenge by constructing a key A client responds to this challenge by constructing a key
authorization from the "token" value provided in the challenge and authorization from the "token" value provided in the challenge and
the client's account key. The client then 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.
skipping to change at page 36, line 48 skipping to change at page 41, line 27
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. In addition, the the challenge's token and the client's account key. In addition, the
client MAY advise the server at which IP the challenge is client MAY advise the server at which IP the challenge is
provisioned. provisioned.
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.
address (optional, string): An IPv4 or IPv6 address, in dotted /* BEGIN JWS-signed content */
decimal form or [RFC4291] form, respectively. If given, this
address MUST be included in the set of IP addresses to which the
domain name resolves when the server attempts validation. If
given, the server SHOULD connect to that specific IP address
instead of arbitrarily choosing an IP from the set of A and AAAA
records to which the domain name resolves.
{ {
"keyAuthorization": "evaGxfADs...62jcerQ" "keyAuthorization": "evaGxfADs...62jcerQ"
} }
/* Signed as JWS */ /* END JWS-signed content */
On receiving a response, the server MUST verify that the key On receiving a response, the server MUST verify that the key
authorization in the response matches the "token" value in the authorization in the response matches the "token" value in the
challenge and the client's account key. If they do not match, then challenge and the client's account key. If they do not match, then
the server MUST return an HTTP error in response to the POST request the server MUST return an HTTP error in response to the POST request
in which the client sent the challenge. in which the client sent the challenge.
Given a challenge/response pair, the server verifies the client's Given a challenge/response pair, the server verifies the client's
control of the domain by verifying that the resource was provisioned control of the domain by verifying that the resource was provisioned
as expected. as expected.
1. Form a URI by populating the URI template [RFC6570] 1. Form a URI by populating the URI template [RFC6570]
"http://{domain}/.well-known/acme-challenge/{token}", where: "http://{domain}/.well-known/acme-challenge/{token}", where:
* the domain field is set to the domain name being verified; and * the domain field is set to the domain name being verified; and
* the token field is set to the token in the challenge. * the token field is set to the token in the challenge.
2. Verify that the resulting URI is well-formed. 2. Verify that the resulting URI is well-formed.
3. If the client has supplied an address to use, verify that the 3. Dereference the URI using an HTTP GET request.
address is included in the A or AAAA records to which the domain
name resolves. If the address is not included in the result, the
validation fails.
4. Dereference the URI using an HTTP GET request. If an address was
supplied by the client, use that address to establish the HTTP
connection.
5. 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.
6. Verify that key authorization provided by the server matches the 5. Verify that key authorization provided by the server matches the
token for this challenge and the client's account key. token for this challenge and the client's account key.
If all of the above verifications succeed, then the validation is If all of the above verifications succeed, then the validation is
successful. If the request fails, or the body does not pass these successful. If the request fails, or the body does not pass these
checks, then it has failed. checks, then it has failed.
7.3. TLS with Server Name Indication (TLS SNI) 7.3. TLS with Server Name Indication (TLS SNI)
The TLS with Server Name Indication (TLS SNI) validation method The TLS with Server Name Indication (TLS SNI) validation method
proves control over a domain name by requiring the client to proves control over a domain name by requiring the client to
skipping to change at page 39, line 9 skipping to change at page 43, line 23
The client MUST ensure that the certificate is served to TLS The client MUST ensure that the certificate is served to TLS
connections specifying a Server Name Indication (SNI) value of SAN A. connections specifying a Server Name Indication (SNI) value of SAN A.
The response to the TLS-SNI challenge simply acknowledges that the The response to the TLS-SNI challenge simply acknowledges that the
client is ready to fulfill this challenge. client is ready to fulfill this challenge.
keyAuthorization (required, string): The key authorization for this keyAuthorization (required, string): The key authorization for this
challenge. This value MUST match the token from the challenge and challenge. This value MUST match the token from the challenge and
the client's account key. the client's account key.
/* BEGIN JWS-signed content */
{ {
"keyAuthorization": "evaGxfADs...62jcerQ", "keyAuthorization": "evaGxfADs...62jcerQ"
} }
/* Signed as JWS */ /* END JWS-signed content */
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 ACME server verifies the Given a challenge/response pair, the ACME server verifies the
client's control of the domain by verifying that the TLS server was client's control of the domain by verifying that the TLS server was
configured appropriately, using these steps: configured appropriately, using these steps:
skipping to change at page 40, line 32 skipping to change at page 45, line 4
The record provisioned to the DNS is the base64url encoding of this The record provisioned to the DNS is the base64url encoding of this
digest. The client constructs the validation domain name by digest. The client constructs the validation domain name by
prepending the label "_acme-challenge" to the domain name being prepending the label "_acme-challenge" to the domain name being
validated, then provisions a TXT record with the digest value under validated, then provisions a TXT record with the digest value under
that name. For example, if the domain name being validated is that name. For example, if the domain name being validated is
"example.com", then the client would provision the following DNS "example.com", then the client would provision the following DNS
record: record:
_acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM" _acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM"
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.
/* BEGIN JWS-signed content */
{ {
"keyAuthorization": "evaGxfADs...62jcerQ", "keyAuthorization": "evaGxfADs...62jcerQ"
} }
/* Signed as JWS */ /* END JWS-signed content */
On receiving a response, the server MUST verify that the key On receiving a response, the server MUST verify that the key
authorization in the response matches the "token" value in the authorization in the response matches the "token" value in the
challenge and the client's account key. If they do not match, then challenge and the client's account key. If they do not match, then
the server MUST return an HTTP error in response to the POST request the server MUST return an HTTP error in response to the POST request
in which the client sent the challenge. in which the client sent the challenge.
To validate a DNS challenge, the server performs the following steps: To validate a DNS challenge, the server performs the following steps:
1. Compute the SHA-256 digest of the key authorization 1. Compute the SHA-256 digest of the key authorization
2. Query for TXT records under the validation domain name 2. Query for TXT records under the validation domain name
3. Verify that the contents of one of the TXT records matches the 3. Verify that the contents of one of the TXT records matches the
digest value digest value
If all of the above verifications succeed, then the validation is If all of the above verifications succeed, then the validation is
successful. If no DNS record is found, or DNS record and response successful. If no DNS record is found, or DNS record and response
payload do not pass these checks, then the validation fails. payload do not pass these checks, then the validation fails.
7.5. Out-of-Band
There may be cases where a server cannot perform automated validation
of an identifier, for example if validation requires some manual
steps. In such cases, the server may provide an "out of band" (OOB)
challenge to request that the client perform some action outside of
ACME in order to validate possession of the identifier.
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
identifier, by providing a URL for that web page.
type (required, string): The string "oob-01"
url (required, string): The URL to be visited. The scheme of this
URL MUST be "http" or "https"
{
"type": "oob-01",
"url": "https://example.com/validate/evaGxfADs6pSRb2LAv9IZ"
}
A client responds to this challenge by presenting the indicated URL
for a human user to navigate to. If the user choses to complete this
challege (by vising the website and completing its instructions), the
client indicates this by sending a simple acknowledgement response to
the server.
type (required, string): The string "oob-01"
/* BEGIN JWS-signed content */
{
"type": "oob-01"
}
/* END JWS-signed content */
On receiving a response, the server MUST verify that the value of the
"type" field is as required. Otherwise, the steps the server takes
to validate identifier possession are determined by the server's
local policy.
8. IANA Considerations 8. IANA Considerations
[[ Editor's Note: Should we create a registry for tokens that go into [[ Editor's Note: Should we create a registry for tokens that go into
the various JSON objects used by this protocol, i.e., the field names the various JSON objects used by this protocol, i.e., the field names
in the JSON objects? ]] in the JSON objects? ]]
9. Well-Known URI for the HTTP Challenge 8.1. Well-Known URI for the HTTP Challenge
The "Well-Known URIs" registry should be updated with the following The "Well-Known URIs" registry should be updated with the following
additional value (using the template from [RFC5785]): additional value (using the template from [RFC5785]):
URI suffix: acme-challenge URI suffix: acme-challenge
Change controller: IETF Change controller: IETF
Specification document(s): This document, Section Section 7.2 Specification document(s): This document, Section Section 7.2
Related information: N/A Related information: N/A
9.1. Replay-Nonce HTTP Header 8.2. 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 |
+:------------+:------+:------+:-----------+ | Replay-Nonce | http | +:------------+:------+:------+:-----------+ | Replay-Nonce | http |
standard | Section 5.4.1 | standard | Section 5.4.1 |
9.2. "nonce" JWS Header Parameter 8.3. "url" JWS Header Parameter
The "JSON Web Signature and Encryption Header Parameters" registry
should be updated with the following additional value:
o Header Parameter Name: "url"
o Header Parameter Description: URL
o Header Parameter Usage Location(s): JWE, JWS
o Change Controller: IESG
o Specification Document(s): Section 5.3.1 of RFC XXXX
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]]
8.4. "nonce" JWS Header Parameter
The "JSON Web Signature and Encryption Header Parameters" registry The "JSON Web Signature and Encryption Header Parameters" registry
should be updated with the following additional value: should be updated with the following additional value:
o Header Parameter Name: "nonce" o Header Parameter Name: "nonce"
o Header Parameter Description: Nonce o Header Parameter Description: Nonce
o Header Parameter Usage Location(s): JWE, JWS o Header Parameter Usage Location(s): JWE, JWS
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 5.4.2 of RFC XXXX o Specification Document(s): Section 5.4.2 of RFC XXXX
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
9.3. URN Sub-namespace for ACME (urn:ietf:params:acme) 8.5. URN Sub-namespace for ACME (urn:ietf:params:acme)
The "IETF URN Sub-namespace for Registered Protocol Parameter The "IETF URN Sub-namespace for Registered Protocol Parameter
Identifiers" registry should be updated with the following additional Identifiers" registry should be updated with the following additional
value, following the template in [RFC3553]: value, following the template in [RFC3553]:
Registry name: acme Registry name: acme
Specification: RFC XXXX Specification: RFC XXXX
Repository: URL-TBD Repository: URL-TBD
Index value: No transformation needed. The Index value: No transformation needed. The
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document, and replace URL-TBD with the URL assigned by IANA to this document, and replace URL-TBD with the URL assigned by IANA
for registries of ACME parameters. ]] for registries of ACME parameters. ]]
9.4. New Registries 8.6. New Registries
This document requests that IANA create three new registries: This document requests that IANA create the following new registries:
1. ACME Error Codes 1. ACME Error Codes
2. ACME Identifier Types 2. ACME Resource Types
3. ACME Challenge Types 3. ACME Identifier Types
4. ACME Challenge Types
All of these registries should be administered under a Specification All of these registries should be administered under a Specification
Required policy [RFC5226]. Required policy [RFC5226].
9.4.1. Error Codes 8.6.1. Error Codes
This registry lists values that are used within URN values that are This registry lists values that are used within URN values that are
provided in the "type" field of problem documents in ACME. provided in the "type" field of problem documents in ACME.
Template: Template:
o Code: The label to be included in the URN for this error, o Code: The label to be included in the URN for this error,
following "urn:ietf:params:acme:" following "urn:ietf:params:acme:"
o Description: A human-readable description of the error o Description: A human-readable description of the error
skipping to change at page 43, line 11 skipping to change at page 49, line 4
provided in the "type" field of problem documents in ACME. provided in the "type" field of problem documents in ACME.
Template: Template:
o Code: The label to be included in the URN for this error, o Code: The label to be included in the URN for this error,
following "urn:ietf:params:acme:" following "urn:ietf:params:acme:"
o Description: A human-readable description of the error o Description: A human-readable description of the error
o Reference: Where the error is defined o Reference: Where the error is defined
Initial contents: The codes and descriptions in the table in Initial contents: The codes and descriptions in the table in
Section 5.5 above, with the Reference field set to point to this Section 5.6 above, with the Reference field set to point to this
specification. specification.
9.4.2. Identifier Types 8.6.2. Resource Types
This registry lists the types of resources that ACME servers may list
in their directory objects.
Template:
o Key: The value to be used as a dictionary key in the directory
object
o Resource type: The type of resource labeled by the key
o Reference: Where the identifier type is defined
Initial contents:
+-------------+--------------------+-----------+
| Key | Resource type | Reference |
+-------------+--------------------+-----------+
| new-reg | New registration | RFC XXXX |
| | | |
| new-app | New application | RFC XXXX |
| | | |
| revoke-cert | Revoke certificate | RFC XXXX |
| | | |
| key-change | Key change | RFC XXXX |
+-------------+--------------------+-----------+
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]]
8.6.3. Identifier Types
This registry lists the types of identifiers that ACME clients may This registry lists the types of identifiers that ACME clients may
request authorization to issue in certificates. request authorization to issue in certificates.
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
skipping to change at page 43, line 39 skipping to change at page 50, line 14
+-------+-----------+ +-------+-----------+
| Label | Reference | | Label | Reference |
+-------+-----------+ +-------+-----------+
| dns | RFC XXXX | | dns | RFC XXXX |
+-------+-----------+ +-------+-----------+
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
9.4.3. Challenge Types 8.6.4. Challenge Types
This registry lists the ways that ACME servers can offer to validate This registry lists the ways that ACME servers can offer to validate
control of an identifier. The "Identifier Type" field in template control of an identifier. The "Identifier Type" field in template
MUST be contained in the Label column of the ACME Identifier Types MUST be contained in the Label column of the ACME Identifier Types
registry. registry.
Template: Template:
o Label: The value to be put in the "type" field of challenge o Label: The value to be put in the "type" field of challenge
objects using this validation mechanism objects using this validation mechanism
skipping to change at page 44, line 22 skipping to change at page 50, line 46
| http | dns | RFC XXXX | | http | dns | RFC XXXX |
| | | | | | | |
| tls-sni | dns | RFC XXXX | | tls-sni | dns | RFC XXXX |
| | | | | | | |
| dns | dns | RFC XXXX | | dns | dns | RFC XXXX |
+---------+-----------------+-----------+ +---------+-----------------+-----------+
[[ RFC EDITOR: Please replace XXXX above with the RFC number assigned [[ RFC EDITOR: Please replace XXXX above with the RFC number assigned
to this document ]] to this document ]]
10. Security Considerations 9. Security Considerations
ACME is a protocol for managing certificates that attest to ACME is a protocol for managing certificates that attest to
identifier/key bindings. Thus the foremost security goal of ACME is identifier/key bindings. Thus the foremost security goal of ACME is
to ensure the integrity of this process, i.e., to ensure that the to ensure the integrity of this process, i.e., to ensure that the
bindings attested by certificates are correct, and that only bindings attested by certificates are correct, and that only
authorized entities can manage certificates. ACME identifies clients authorized entities can manage certificates. ACME identifies clients
by their account keys, so this overall goal breaks down into two more by their account keys, so this overall goal breaks down into two more
precise goals: precise goals:
1. Only an entity that controls an identifier can get an account key 1. Only an entity that controls an identifier can get an account key
authorized for that identifier authorized for that identifier
2. Once authorized, an account key's authorizations cannot be 2. Once authorized, an account key's authorizations cannot be
improperly transferred to another account key improperly transferred to another account key
In this section, we discuss the threat model that underlies ACME and In this section, we discuss the threat model that underlies ACME and
the ways that ACME achieves these security goals within that threat the ways that ACME achieves these security goals within that threat
model. We also discuss the denial-of-service risks that ACME servers model. We also discuss the denial-of-service risks that ACME servers
face, and a few other miscellaneous considerations. face, and a few other miscellaneous considerations.
10.1. Threat model 9.1. Threat model
As a service on the Internet, ACME broadly exists within the Internet As a service on the Internet, ACME broadly exists within the Internet
threat model [RFC3552]. In analyzing ACME, it is useful to think of threat model [RFC3552]. In analyzing ACME, it is useful to think of
an ACME server interacting with other Internet hosts along three an ACME server interacting with other Internet hosts along three
"channels": "channels":
o An ACME channel, over which the ACME HTTPS requests are exchanged o An ACME channel, over which the ACME HTTPS requests are exchanged
o A validation channel, over which the ACME server performs o A validation channel, over which the ACME server performs
additional requests to validate a client's control of an additional requests to validate a client's control of an
identifier identifier
o A contact channel, over which the ACME server sends messages to o A contact channel, over which the ACME server sends messages to
the registered contacts for ACME clients the registered contacts for ACME clients
+------------+ +------------+
| ACME | ACME Channel | ACME | ACME Channel
| Client |--------------------+ | Client |--------------------+
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On the ACME channel, in addition to network-layer attackers, we also On the ACME channel, in addition to network-layer attackers, we also
need to account for application-layer man in the middle attacks, and need to account for application-layer man in the middle attacks, and
for abusive use of the protocol itself. Protection against for abusive use of the protocol itself. Protection against
application-layer MitM addresses potential attackers such as Content application-layer MitM addresses potential attackers such as Content
Distribution Networks (CDNs) and middleboxes with a TLS MitM Distribution Networks (CDNs) and middleboxes with a TLS MitM
function. Preventing abusive use of ACME means ensuring that an function. Preventing abusive use of ACME means ensuring that an
attacker with access to the validation or contact channels can't attacker with access to the validation or contact channels can't
obtain illegitimate authorization by acting as an ACME client obtain illegitimate authorization by acting as an ACME client
(legitimately, in terms of the protocol). (legitimately, in terms of the protocol).
10.2. Integrity of Authorizations 9.2. Integrity of Authorizations
ACME allows anyone to request challenges for an identifier by ACME allows anyone to request challenges for an identifier by
registering an account key and sending a new-authorization request registering an account key and sending a new-application request
under that account key. The integrity of the authorization process under that account key. The integrity of the authorization process
thus depends on the identifier validation challenges to ensure that thus depends on the identifier validation challenges to ensure that
the challenge can only be completed by someone who both (1) holds the the challenge can only be completed by someone who both (1) holds the
private key of the account key pair, and (2) controls the identifier private key of the account key pair, and (2) controls the identifier
in question. in question.
Validation responses need to be bound to an account key pair in order Validation responses need to be bound to an account key pair in order
to avoid situations where an ACME MitM can switch out a legitimate to avoid situations where an ACME MitM can switch out a legitimate
domain holder's account key for one of his choosing, e.g.: domain holder's account key for one of his choosing, e.g.:
o Legitimate domain holder registers account key pair A o Legitimate domain holder registers account key pair A
o MitM registers account key pair B o MitM registers account key pair B
o Legitimate domain holder sends a new-authorization request signed o Legitimate domain holder sends a new-application request signed
under account key A under account key A
o MitM suppresses the legitimate request, but sends the same request o MitM suppresses the legitimate request, but sends the same request
signed under account key B signed under account key B
o ACME server issues challenges and MitM forwards them to the o ACME server issues challenges and MitM forwards them to the
legitimate domain holder legitimate domain holder
o Legitimate domain holder provisions the validation response o Legitimate domain holder provisions the validation response
o ACME server performs validation query and sees the response o ACME server performs validation query and sees the response
provisioned by the legitimate domain holder provisioned by the legitimate domain holder
o Because the challenges were issued in response to a message signed o Because the challenges were issued in response to a message signed
account key B, the ACME server grants authorization to account key account key B, the ACME server grants authorization to account key
B (the MitM) instead of account key A (the legitimate domain B (the MitM) instead of account key A (the legitimate domain
holder) holder)
All of the challenges above that require an out-of-band query by the All of the challenges above have a binding between the account
server have a binding to the account private key, such that only the private key and the validation query made by the server, via the key
account private key holder can successfully respond to the validation authorization. The key authorization is signed by the account
query: private key, reflects the corresponding public key, and is provided
to the server in the validation response.
o HTTP: The value provided in the validation request is signed by
the account private key.
o TLS SNI: The validation TLS request uses the account key pair as
the server's key pair.
o DNS: The MAC covers the account key, and the MAC key is derived
from an ECDH public key signed with the account private key.
The association of challenges to identifiers is typically done by The association of challenges to identifiers is typically done by
requiring the client to perform some action that only someone who requiring the client to perform some action that only someone who
effectively controls the identifier can perform. For the challenges effectively controls the identifier can perform. For the challenges
in this document, the actions are: in this document, the actions are:
o HTTP: Provision files under .well-known on a web server for the o HTTP: Provision files under .well-known on a web server for the
domain domain
o TLS SNI: Configure a TLS server for the domain o TLS SNI: Configure a TLS server for the domain
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DNS or web services to a hosting provider, there is nothing that can DNS or web services to a hosting provider, there is nothing that can
be done against tampering by the hosting provider. As far as the be done against tampering by the hosting provider. As far as the
outside world is concerned, the zone or web site provided by the outside world is concerned, the zone or web site provided by the
hosting provider is the real thing. hosting provider is the real thing.
More limited forms of delegation can also lead to an unintended party More limited forms of delegation can also lead to an unintended party
gaining the ability to successfully complete a validation gaining the ability to successfully complete a validation
transaction. For example, suppose an ACME server follows HTTP transaction. For example, suppose an ACME server follows HTTP
redirects in HTTP validation and a web site operator provisions a redirects in HTTP validation and a web site operator provisions a
catch-all redirect rule that redirects requests for unknown resources catch-all redirect rule that redirects requests for unknown resources
to different domain. Then the target of the redirect could use that to a different domain. Then the target of the redirect could use
to get a certificate through HTTP validation, since the validation that to get a certificate through HTTP validation, since the
path will not be known to the primary server. validation path will not be known to the primary server.
The DNS is a common point of vulnerability for all of these The DNS is a common point of vulnerability for all of these
challenges. An entity that can provision false DNS records for a challenges. An entity that can provision false DNS records for a
domain can attack the DNS challenge directly, and can provision false domain can attack the DNS challenge directly, and can provision false
A/AAAA records to direct the ACME server to send its TLS SNI or HTTP A/AAAA records to direct the ACME server to send its TLS SNI or HTTP
validation query to a server of the attacker's choosing. There are a validation query to a server of the attacker's choosing. There are a
few different mitigations that ACME servers can apply: few different mitigations that ACME servers can apply:
o Always querying the DNS using a DNSSEC-validating resolver o Always querying the DNS using a DNSSEC-validating resolver
(enhancing security for zones that are DNSSEC-enabled) (enhancing security for zones that are DNSSEC-enabled)
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used with the account key for which it was generated. used with the account key for which it was generated.
An active attacker on the validation channel can subvert the ACME An active attacker on the validation channel can subvert the ACME
process, by performing normal ACME transactions and providing a process, by performing normal ACME transactions and providing a
validation response for his own account key. The risks due to validation response for his own account key. The risks due to
hosting providers noted above are a particular case. For identifiers hosting providers noted above are a particular case. For identifiers
where the server already has some public key associated with the where the server already has some public key associated with the
domain this attack can be prevented by requiring the client to prove domain this attack can be prevented by requiring the client to prove
control of the corresponding private key. control of the corresponding private key.
10.3. Denial-of-Service Considerations 9.3. Denial-of-Service Considerations
As a protocol run over HTTPS, standard considerations for TCP-based As a protocol run over HTTPS, standard considerations for TCP-based
and HTTP-based DoS mitigation also apply to ACME. and HTTP-based DoS mitigation also apply to ACME.
At the application layer, ACME requires the server to perform a few At the application layer, ACME requires the server to perform a few
potentially expensive operations. Identifier validation transactions potentially expensive operations. Identifier validation transactions
require the ACME server to make outbound connections to potentially require the ACME server to make outbound connections to potentially
attacker-controlled servers, and certificate issuance can require attacker-controlled servers, and certificate issuance can require
interactions with cryptographic hardware. interactions with cryptographic hardware.
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All of these attacks can be mitigated by the application of All of these attacks can be mitigated by the application of
appropriate rate limits. Issues closer to the front end, like POST appropriate rate limits. Issues closer to the front end, like POST
body validation, can be addressed using HTTP request limiting. For body validation, can be addressed using HTTP request limiting. For
validation and certificate requests, there are other identifiers on validation and certificate requests, there are other identifiers on
which rate limits can be keyed. For example, the server might limit which rate limits can be keyed. For example, the server might limit
the rate at which any individual account key can issue certificates, the rate at which any individual account key can issue certificates,
or the rate at which validation can be requested within a given or the rate at which validation can be requested within a given
subtree of the DNS. subtree of the DNS.
10.4. CA Policy Considerations 9.4. Server-Side Request Forgery
Server-Side Request Forgery (SSRF) attacks can arise when an attacker
can cause a server to perform HTTP requests to an attacker-chosen
URL. In the ACME HTTP challenge validation process, the ACME server
performs an HTTP GET request to a URL in which the attacker can
choose the domain. This request is made before the server has
verified that the client controls the domain, so any client can cause
a query to any domain.
Some server implementations include information from the validation
server's response (in order to facilitate debugging). Such
implementations enable an attacker to extract this information from
any web server that is accessible to the ACME server, even if it is
not accessible to the ACME client.
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,
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
302 response) which will cause the server to query an arbitrary URI.
In order to further limit the SSRF risk, ACME server operators should
ensure that validation queries can only be sent to servers on the
public Internet, and not, say, web services within the server
operator's internal network. Since the attacker could make requests
to these public servers himself, he can't gain anything extra through
an SSRF attack on ACME aside from a layer of anonymization.
9.5. CA Policy Considerations
The controls on issuance enabled by ACME are focused on validating The controls on issuance enabled by ACME are focused on validating
that a certificate applicant controls the identifier he claims. that a certificate applicant controls the identifier he claims.
Before issuing a certificate, however, there are many other checks Before issuing a certificate, however, there are many other checks
that a CA might need to perform, for example: that a CA might need to perform, for example:
o Has the client agreed to a subscriber agreement? o Has the client agreed to a subscriber agreement?
o Is the claimed identifier syntactically valid? o Is the claimed identifier syntactically valid?
skipping to change at page 49, line 34 skipping to change at page 56, line 27
* 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?
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.
11. Operational Considerations 10. Operational Considerations
There are certain factors that arise in operational reality that There are certain factors that arise in operational reality that
operators of ACME-based CAs will need to keep in mind when operators of ACME-based CAs will need to keep in mind when
configuring their services. For example: configuring their services. For example:
o It is advisable to perform DNS queries via TCP to mitigate DNS 10.1. DNS over TCP
forgery attacks over UDP
[[ TODO: Other operational considerations ]] As noted above, DNS forgery attacks against the ACME server can
result in the server making incorrect decisions about domain control
and thus mis-issuing certificates. Servers SHOULD verify DNSSEC when
it is available for a domain. When DNSSEC is not available, servers
SHOULD perform DNS queries over TCP, which provides better resistance
to some forgery attacks than DNS over UDP.
11.1. Default Virtual Hosts 10.2. Default Virtual Hosts
In many cases, TLS-based services are deployed on hosted platforms In many cases, TLS-based services are deployed on hosted platforms
that use the Server Name Indication (SNI) TLS extension to that use the Server Name Indication (SNI) TLS extension to
distinguish between different hosted services or "virtual hosts". distinguish between different hosted services or "virtual hosts".
When a client initiates a TLS connection with an SNI value indicating When a client initiates a TLS connection with an SNI value indicating
a provisioned host, the hosting platform routes the connection to a provisioned host, the hosting platform routes the connection to
that host. that host.
When a connection come in with an unknown SNI value, one might expect When a connection comes in with an unknown SNI value, one might
the hosting platform to terminate the TLS connection. However, some expect the hosting platform to terminate the TLS connection.
hosting platforms will choose a virtual host to be the "default", and
route connections with unknown SNI values to that host. However, some hosting platforms will choose a virtual host to be the
"default", and route connections with unknown SNI values to that
host.
In such cases, the owner of the default virtual host can complete a In such cases, the owner of the default virtual host can complete a
TLS-based challenge (e.g., "tls-sni-02") for any domain with an A TLS-based challenge (e.g., "tls-sni-02") for any domain with an A
record that points to the hosting platform. This could result in record that points to the hosting platform. This could result in
mis-issuance in cases where there are multiple hosts with different mis-issuance in cases where there are multiple hosts with different
owners resident on the hosting platform. owners resident on the hosting platform.
A CA that accepts TLS-based proof of domain control should attempt to A CA that accepts TLS-based proof of domain control should attempt to
check whether a domain is hosted on a domain with a default virtual check whether a domain is hosted on a domain with a default virtual
host before allowing an authorization request for this host to use a host before allowing an authorization request for this host to use a
TLS-based challenge. A default virtual host can be detected by TLS-based challenge. A default virtual host can be detected by
initiating TLS connections to the host with random SNI values within initiating TLS connections to the host with random SNI values within
the namespace used for the TLS-based challenge (the "acme.invalid" the namespace used for the TLS-based challenge (the "acme.invalid"
namespace for "tls-sni-02"). namespace for "tls-sni-02").
11.2. Use of DNSSEC Resolvers 10.3. Use of DNSSEC Resolvers
An ACME-based CA will often need to make DNS queries, e.g., to An ACME-based CA will often need to make DNS queries, e.g., to
validate control of DNS names. Because the security of such validate control of DNS names. Because the security of such
validations ultimately depends on the authenticity of DNS data, every validations ultimately depends on the authenticity of DNS data, every
possible precaution should be taken to secure DNS queries done by the possible precaution should be taken to secure DNS queries done by the
CA. It is therefore RECOMMENDED that ACME-based CAs make all DNS CA. It is therefore RECOMMENDED that ACME-based CAs make all DNS
queries via DNSSEC-validating stub or recursive resolvers. This queries via DNSSEC-validating stub or recursive resolvers. This
provides additional protection to domains which choose to make use of provides additional protection to domains which choose to make use of
DNSSEC. DNSSEC.
An ACME-based CA must use only a resolver if it trusts the resolver An ACME-based CA must use only a resolver if it trusts the resolver
and every component of the network route by which it is accessed. It and every component of the network route by which it is accessed. It
is therefore RECOMMENDED that ACME-based CAs operate their own is therefore RECOMMENDED that ACME-based CAs operate their own
DNSSEC-validating resolvers within their trusted network and use DNSSEC-validating resolvers within their trusted network and use
these resolvers both for both CAA record lookups and all record these resolvers both for both CAA record lookups and all record
lookups in furtherance of a challenge scheme (A, AAAA, TXT, etc.). lookups in furtherance of a challenge scheme (A, AAAA, TXT, etc.).
12. Acknowledgements 11. 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
This document draws on many concepts established by Eric Rescorla's This document draws on many concepts established by Eric Rescorla's
"Automated Certificate Issuance Protocol" draft. Martin Thomson "Automated Certificate Issuance Protocol" draft. Martin Thomson
provided helpful guidance in the use of HTTP. provided helpful guidance in the use of HTTP.
13. References 12. References
13.1. Normative References
[I-D.ietf-appsawg-http-problem] 12.1. Normative References
mnot, m. and E. Wilde, "Problem Details for HTTP APIs",
draft-ietf-appsawg-http-problem-03 (work in progress),
January 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2314] Kaliski, B., "PKCS #10: Certification Request Syntax
Version 1.5", RFC 2314, DOI 10.17487/RFC2314, March 1998,
<http://www.rfc-editor.org/info/rfc2314>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>. <http://www.rfc-editor.org/info/rfc2818>.
[RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object [RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
Classes and Attribute Types Version 2.0", RFC 2985, Classes and Attribute Types Version 2.0", RFC 2985,
DOI 10.17487/RFC2985, November 2000, DOI 10.17487/RFC2985, November 2000,
<http://www.rfc-editor.org/info/rfc2985>. <http://www.rfc-editor.org/info/rfc2985>.
[RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification [RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986, Request Syntax Specification Version 1.7", RFC 2986,
DOI 10.17487/RFC2986, November 2000, DOI 10.17487/RFC2986, November 2000,
<http://www.rfc-editor.org/info/rfc2986>. <http://www.rfc-editor.org/info/rfc2986>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<http://www.rfc-editor.org/info/rfc3339>. <http://www.rfc-editor.org/info/rfc3339>.
[RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
IETF URN Sub-namespace for Registered Protocol Resource Identifier (URI): Generic Syntax", STD 66,
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June RFC 3986, DOI 10.17487/RFC3986, January 2005,
2003, <http://www.rfc-editor.org/info/rfc3553>. <http://www.rfc-editor.org/info/rfc3986>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>. <http://www.rfc-editor.org/info/rfc4648>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>. <http://www.rfc-editor.org/info/rfc5280>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010,
<http://www.rfc-editor.org/info/rfc5785>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, [RFC5988] Nottingham, M., "Web Linking", RFC 5988,
DOI 10.17487/RFC5988, October 2010, DOI 10.17487/RFC5988, October 2010,
<http://www.rfc-editor.org/info/rfc5988>. <http://www.rfc-editor.org/info/rfc5988>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066, Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011, DOI 10.17487/RFC6066, January 2011,
<http://www.rfc-editor.org/info/rfc6066>. <http://www.rfc-editor.org/info/rfc6066>.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M., [RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570, and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012, DOI 10.17487/RFC6570, March 2012,
<http://www.rfc-editor.org/info/rfc6570>. <http://www.rfc-editor.org/info/rfc6570>.
[RFC6844] Hallam-Baker, P. and R. Stradling, "DNS Certification [RFC6844] Hallam-Baker, P. and R. Stradling, "DNS Certification
Authority Authorization (CAA) Resource Record", RFC 6844, Authority Authorization (CAA) Resource Record", RFC 6844,
DOI 10.17487/RFC6844, January 2013, DOI 10.17487/RFC6844, January 2013,
<http://www.rfc-editor.org/info/rfc6844>. <http://www.rfc-editor.org/info/rfc6844>.
[RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate
Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
<http://www.rfc-editor.org/info/rfc6962>.
[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>.
[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
2015, <http://www.rfc-editor.org/info/rfc7469>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>. 2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, [RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015, DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>. <http://www.rfc-editor.org/info/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015, DOI 10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>. <http://www.rfc-editor.org/info/rfc7518>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK) [RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <http://www.rfc-editor.org/info/rfc7638>. 2015, <http://www.rfc-editor.org/info/rfc7638>.
13.2. Informative References [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016,
<http://www.rfc-editor.org/info/rfc7807>.
12.2. Informative References
[I-D.vixie-dnsext-dns0x20] [I-D.vixie-dnsext-dns0x20]
Vixie, P. and D. Dagon, "Use of Bit 0x20 in DNS Labels to Vixie, P. and D. Dagon, "Use of Bit 0x20 in DNS Labels to
Improve Transaction Identity", draft-vixie-dnsext- Improve Transaction Identity", draft-vixie-dnsext-
dns0x20-00 (work in progress), March 2008. dns0x20-00 (work in progress), March 2008.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003, DOI 10.17487/RFC3552, July 2003,
<http://www.rfc-editor.org/info/rfc3552>. <http://www.rfc-editor.org/info/rfc3552>.
[RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
IETF URN Sub-namespace for Registered Protocol
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
2003, <http://www.rfc-editor.org/info/rfc3553>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010,
<http://www.rfc-editor.org/info/rfc5785>.
[RFC6962] Laurie, B., Langley, A., and E. Kasper, "Certificate
Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
<http://www.rfc-editor.org/info/rfc6962>.
[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
2015, <http://www.rfc-editor.org/info/rfc7469>.
[W3C.CR-cors-20130129] [W3C.CR-cors-20130129]
Kesteren, A., "Cross-Origin Resource Sharing", World Wide Kesteren, A., "Cross-Origin Resource Sharing", World Wide
Web Consortium CR CR-cors-20130129, January 2013, Web Consortium CR CR-cors-20130129, January 2013,
<http://www.w3.org/TR/2013/CR-cors-20130129>. <http://www.w3.org/TR/2013/CR-cors-20130129>.
[W3C.WD-capability-urls-20140218]
Tennison, J., "Good Practices for Capability URLs", World
Wide Web Consortium WD WD-capability-urls-20140218,
February 2014,
<http://www.w3.org/TR/2014/WD-capability-urls-20140218>.
Authors' Addresses Authors' Addresses
Richard Barnes Richard Barnes
Mozilla Mozilla
Email: rlb@ipv.sx Email: rlb@ipv.sx
Jacob Hoffman-Andrews Jacob Hoffman-Andrews
EFF EFF
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