draft-ietf-oauth-mtls-16.txt   draft-ietf-oauth-mtls-17.txt 
OAuth Working Group B. Campbell OAuth Working Group B. Campbell
Internet-Draft Ping Identity Internet-Draft Ping Identity
Intended status: Standards Track J. Bradley Intended status: Standards Track J. Bradley
Expires: February 14, 2020 Yubico Expires: February 23, 2020 Yubico
N. Sakimura N. Sakimura
Nomura Research Institute Nomura Research Institute
T. Lodderstedt T. Lodderstedt
YES.com AG YES.com AG
August 13, 2019 August 22, 2019
OAuth 2.0 Mutual TLS Client Authentication and Certificate-Bound OAuth 2.0 Mutual-TLS Client Authentication and Certificate-Bound
Access Tokens Access Tokens
draft-ietf-oauth-mtls-16 draft-ietf-oauth-mtls-17
Abstract Abstract
This document describes OAuth client authentication and certificate- This document describes OAuth client authentication and certificate-
bound access and refresh tokens using mutual Transport Layer Security bound access and refresh tokens using mutual Transport Layer Security
(TLS) authentication with X.509 certificates. OAuth clients are (TLS) authentication with X.509 certificates. OAuth clients are
provided a mechanism for authentication to the authorization server provided a mechanism for authentication to the authorization server
using mutual TLS, based on either self-signed certificates or public using mutual TLS, based on either self-signed certificates or public
key infrastructure (PKI). OAuth authorization servers are provided a key infrastructure (PKI). OAuth authorization servers are provided a
mechanism for binding access tokens to a client's mutual TLS mechanism for binding access tokens to a client's mutual-TLS
certificate, and OAuth protected resources are provided a method for certificate, and OAuth protected resources are provided a method for
ensuring that such an access token presented to it was issued to the ensuring that such an access token presented to it was issued to the
client presenting the token. client presenting the token.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 14, 2020. This Internet-Draft will expire on February 23, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 26 skipping to change at page 2, line 26
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
1.1. Requirements Notation and Conventions . . . . . . . . . . 5 1.1. Requirements Notation and Conventions . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Mutual TLS for OAuth Client Authentication . . . . . . . . . 5 2. Mutual TLS for OAuth Client Authentication . . . . . . . . . 5
2.1. PKI Mutual TLS Method . . . . . . . . . . . . . . . . . . 6 2.1. PKI Mutual-TLS Method . . . . . . . . . . . . . . . . . . 6
2.1.1. PKI Method Metadata Value . . . . . . . . . . . . . . 7 2.1.1. PKI Method Metadata Value . . . . . . . . . . . . . . 7
2.1.2. Client Registration Metadata . . . . . . . . . . . . 7 2.1.2. Client Registration Metadata . . . . . . . . . . . . 7
2.2. Self-Signed Certificate Mutual TLS Method . . . . . . . . 8 2.2. Self-Signed Certificate Mutual-TLS Method . . . . . . . . 8
2.2.1. Self-Signed Method Metadata Value . . . . . . . . . . 8 2.2.1. Self-Signed Method Metadata Value . . . . . . . . . . 8
2.2.2. Client Registration Metadata . . . . . . . . . . . . 8 2.2.2. Client Registration Metadata . . . . . . . . . . . . 8
3. Mutual TLS Client Certificate-Bound Access Tokens . . . . . . 9 3. Mutual-TLS Client Certificate-Bound Access Tokens . . . . . . 9
3.1. JWT Certificate Thumbprint Confirmation Method . . . . . 9 3.1. JWT Certificate Thumbprint Confirmation Method . . . . . 10
3.2. Confirmation Method for Token Introspection . . . . . . . 10 3.2. Confirmation Method for Token Introspection . . . . . . . 11
3.3. Authorization Server Metadata . . . . . . . . . . . . . . 11 3.3. Authorization Server Metadata . . . . . . . . . . . . . . 12
3.4. Client Registration Metadata . . . . . . . . . . . . . . 11 3.4. Client Registration Metadata . . . . . . . . . . . . . . 12
4. Public Clients and Certificate-Bound Tokens . . . . . . . . . 12 4. Public Clients and Certificate-Bound Tokens . . . . . . . . . 13
5. Metadata for Mutual TLS Endpoint Aliases . . . . . . . . . . 12 5. Metadata for Mutual-TLS Endpoint Aliases . . . . . . . . . . 13
6. Implementation Considerations . . . . . . . . . . . . . . . . 14 6. Implementation Considerations . . . . . . . . . . . . . . . . 15
6.1. Authorization Server . . . . . . . . . . . . . . . . . . 14 6.1. Authorization Server . . . . . . . . . . . . . . . . . . 15
6.2. Resource Server . . . . . . . . . . . . . . . . . . . . . 15 6.2. Resource Server . . . . . . . . . . . . . . . . . . . . . 16
6.3. Certificate Expiration and Bound Access Tokens . . . . . 15 6.3. Certificate Expiration and Bound Access Tokens . . . . . 16
6.4. Implicit Grant Unsupported . . . . . . . . . . . . . . . 15 6.4. Implicit Grant Unsupported . . . . . . . . . . . . . . . 16
6.5. TLS Termination . . . . . . . . . . . . . . . . . . . . . 16 6.5. TLS Termination . . . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7.1. Certificate-Bound Refresh Tokens . . . . . . . . . . . . 16 7.1. Certificate-Bound Refresh Tokens . . . . . . . . . . . . 17
7.2. Certificate Thumbprint Binding . . . . . . . . . . . . . 16 7.2. Certificate Thumbprint Binding . . . . . . . . . . . . . 17
7.3. TLS Versions and Best Practices . . . . . . . . . . . . . 17 7.3. TLS Versions and Best Practices . . . . . . . . . . . . . 18
7.4. X.509 Certificate Spoofing . . . . . . . . . . . . . . . 17 7.4. X.509 Certificate Spoofing . . . . . . . . . . . . . . . 18
7.5. X.509 Certificate Parsing and Validation Complexity . . . 17 7.5. X.509 Certificate Parsing and Validation Complexity . . . 18
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 18 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9.1. JWT Confirmation Methods Registration . . . . . . . . . . 18 9.1. JWT Confirmation Methods Registration . . . . . . . . . . 19
9.2. Authorization Server Metadata Registration . . . . . . . 18 9.2. Authorization Server Metadata Registration . . . . . . . 19
9.3. Token Endpoint Authentication Method Registration . . . . 19 9.3. Token Endpoint Authentication Method Registration . . . . 20
9.4. Token Introspection Response Registration . . . . . . . . 19 9.4. Token Introspection Response Registration . . . . . . . . 20
9.5. Dynamic Client Registration Metadata Registration . . . . 20 9.5. Dynamic Client Registration Metadata Registration . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.1. Normative References . . . . . . . . . . . . . . . . . . 21 10.1. Normative References . . . . . . . . . . . . . . . . . . 22
10.2. Informative References . . . . . . . . . . . . . . . . . 22 10.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. Example "cnf" Claim, Certificate and JWK . . . . . . 23 Appendix A. Example "cnf" Claim, Certificate and JWK . . . . . . 25
Appendix B. Relationship to Token Binding . . . . . . . . . . . 24 Appendix B. Relationship to Token Binding . . . . . . . . . . . 26
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 25 Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 26
Appendix D. Document(s) History . . . . . . . . . . . . . . . . 25 Appendix D. Document(s) History . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
The OAuth 2.0 Authorization Framework [RFC6749] enables third-party The OAuth 2.0 Authorization Framework [RFC6749] enables third-party
client applications to obtain delegated access to protected client applications to obtain delegated access to protected
resources. In the prototypical abstract OAuth flow, illustrated in resources. In the prototypical abstract OAuth flow, illustrated in
Figure 1, the client obtains an access token from an entity known as Figure 1, the client obtains an access token from an entity known as
an authorization server and then uses that token when accessing an authorization server and then uses that token when accessing
protected resources, such as HTTPS APIs. protected resources, such as HTTPS APIs.
skipping to change at page 4, line 20 skipping to change at page 4, line 20
issued or otherwise established a set of client credentials) the issued or otherwise established a set of client credentials) the
request must be authenticated. In the response, the request must be authenticated. In the response, the
authorization server issues an access token to the client. authorization server issues an access token to the client.
(B) The client includes the access token when making a request to (B) The client includes the access token when making a request to
access a protected resource. access a protected resource.
(C) The protected resource validates the access token in order to (C) The protected resource validates the access token in order to
authorize the request. In some cases, such as when the token is authorize the request. In some cases, such as when the token is
self-contained and cryptographically secured, the validation can self-contained and cryptographically secured, the validation can
be done locally by the protected resource. While other cases be done locally by the protected resource. Other cases require
require that the protected resource call out to the that the protected resource call out to the authorization server
authorization server to determine the state of the token and to determine the state of the token and obtain meta-information
obtain meta-information about it. about it.
Layering on the abstract flow above, this document standardizes Layering on the abstract flow above, this document standardizes
enhanced security options for OAuth 2.0 utilizing client certificate enhanced security options for OAuth 2.0 utilizing client-certificate-
based mutual TLS. Section 2 provides options for authenticating the based mutual TLS. Section 2 provides options for authenticating the
request in step (A). While step (C) is supported with semantics to request in step (A). Step (C) is supported with semantics to express
express the binding of the token to the client certificate for both the binding of the token to the client certificate for both local and
local and remote processing in Section 3.1 and Section 3.2 remote processing in Section 3.1 and Section 3.2 respectively. This
respectively. This ensures that, as described in Section 3, ensures that, as described in Section 3, protected resource access in
protected resource access in step (B) is only possible by the step (B) is only possible by the legitimate client using a
legitimate client bearing the access token and holding the private certificate-bound token and holding the private key corresponding to
key corresponding to the certificate. the certificate.
OAuth 2.0 defines a shared secret method of client authentication but OAuth 2.0 defines a shared-secret method of client authentication but
also allows for definition and use of additional client also allows for definition and use of additional client
authentication mechanisms when interacting directly with the authentication mechanisms when interacting directly with the
authorization server. This document describes an additional authorization server. This document describes an additional
mechanism of client authentication utilizing mutual TLS certificate- mechanism of client authentication utilizing mutual-TLS certificate-
based authentication, which provides better security characteristics based authentication, which provides better security characteristics
than shared secrets. While [RFC6749] documents client authentication than shared secrets. While [RFC6749] documents client authentication
for requests to the token endpoint, extensions to OAuth 2.0 (such as for requests to the token endpoint, extensions to OAuth 2.0 (such as
Introspection [RFC7662], Revocation [RFC7009], and the Backchannel Introspection [RFC7662], Revocation [RFC7009], and the Backchannel
Authentication Endpoint in [OpenID.CIBA]) define endpoints that also Authentication Endpoint in [OpenID.CIBA]) define endpoints that also
utilize client authentication and the mutual TLS methods defined utilize client authentication and the mutual TLS methods defined
herein are applicable to those endpoints as well. herein are applicable to those endpoints as well.
Mutual TLS certificate-bound access tokens ensure that only the party Mutual-TLS certificate-bound access tokens ensure that only the party
in possession of the private key corresponding to the certificate can in possession of the private key corresponding to the certificate can
utilize the token to access the associated resources. Such a utilize the token to access the associated resources. Such a
constraint is sometimes referred to as key confirmation, proof-of- constraint is sometimes referred to as key confirmation, proof-of-
possession, or holder-of-key and is unlike the case of the bearer possession, or holder-of-key and is unlike the case of the bearer
token described in [RFC6750], where any party in possession of the token described in [RFC6750], where any party in possession of the
access token can use it to access the associated resources. Binding access token can use it to access the associated resources. Binding
an access token to the client's certificate prevents the use of an access token to the client's certificate prevents the use of
stolen access tokens or replay of access tokens by unauthorized stolen access tokens or replay of access tokens by unauthorized
parties. parties.
Mutual TLS certificate-bound access tokens and mutual TLS client Mutual-TLS certificate-bound access tokens and mutual-TLS client
authentication are distinct mechanisms, which are complementary but authentication are distinct mechanisms, which are complementary but
don't necessarily need to be deployed or used together. don't necessarily need to be deployed or used together.
Additional client metadata parameters are introduced by this document Additional client metadata parameters are introduced by this document
in support of certificate-bound access tokens and mutual TLS client in support of certificate-bound access tokens and mutual-TLS client
authentication. The authorization server can obtain client metadata authentication. The authorization server can obtain client metadata
via the Dynamic Client Registration Protocol [RFC7591], which defines via the Dynamic Client Registration Protocol [RFC7591], which defines
mechanisms for dynamically registering OAuth 2.0 client metadata with mechanisms for dynamically registering OAuth 2.0 client metadata with
authorization servers. Also the metadata defined by RFC7591, and authorization servers. Also the metadata defined by RFC7591, and
registered extensions to it, imply a general data model for clients registered extensions to it, imply a general data model for clients
that is useful for authorization server implementations even when the that is useful for authorization server implementations even when the
Dynamic Client Registration Protocol isn't in play. Such Dynamic Client Registration Protocol isn't in play. Such
implementations will typically have some sort of user interface implementations will typically have some sort of user interface
available for managing client configuration. available for managing client configuration.
skipping to change at page 5, line 38 skipping to change at page 5, line 38
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. Terminology 1.2. Terminology
Throughout this document the term "mutual TLS" refers to the process Throughout this document the term "mutual TLS" refers to the process
whereby a client presents its X.509 certificate and proves possession whereby, in addition to the normal TLS server authentication with a
of the corresponding private key to a server when negotiating a TLS certificate, a client presents its X.509 certificate and proves
session. In contemporary versions of TLS [RFC8446] [RFC5246] this possession of the corresponding private key to a server when
requires that the client send the Certificate and CertificateVerify negotiating a TLS session. In contemporary versions of TLS [RFC8446]
messages during the handshake and for the server to verify the [RFC5246] this requires that the client send the Certificate and
CertificateVerify and Finished messages. CertificateVerify messages during the handshake and for the server to
verify the CertificateVerify and Finished messages.
2. Mutual TLS for OAuth Client Authentication 2. Mutual TLS for OAuth Client Authentication
This section defines, as an extension of OAuth 2.0, Section 2.3 This section defines, as an extension of OAuth 2.0, Section 2.3
[RFC6749], two distinct methods of using mutual TLS X.509 client [RFC6749], two distinct methods of using mutual-TLS X.509 client
certificates as client credentials. The requirement of mutual TLS certificates as client credentials. The requirement of mutual TLS
for client authentication is determined by the authorization server for client authentication is determined by the authorization server
based on policy or configuration for the given client (regardless of based on policy or configuration for the given client (regardless of
whether the client was dynamically registered, statically configured, whether the client was dynamically registered, statically configured,
or otherwise established). or otherwise established).
In order to utilize TLS for OAuth client authentication, the TLS In order to utilize TLS for OAuth client authentication, the TLS
connection between the client and the authorization server MUST have connection between the client and the authorization server MUST have
been established or reestablished with mutual TLS X.509 certificate been established or reestablished with mutual-TLS X.509 certificate
authentication (i.e. the Client Certificate and Certificate Verify authentication (i.e. the Client Certificate and Certificate Verify
messages are sent during the TLS Handshake). messages are sent during the TLS Handshake).
For all requests to the authorization server utilizing mutual TLS For all requests to the authorization server utilizing mutual-TLS
client authentication, the client MUST include the "client_id" client authentication, the client MUST include the "client_id"
parameter, described in OAuth 2.0, Section 2.2 [RFC6749]. The parameter, described in OAuth 2.0, Section 2.2 [RFC6749]. The
presence of the "client_id" parameter enables the authorization presence of the "client_id" parameter enables the authorization
server to easily identify the client independently from the content server to easily identify the client independently from the content
of the certificate. The authorization server can locate the client of the certificate. The authorization server can locate the client
configuration using the client identifier and check the certificate configuration using the client identifier and check the certificate
presented in the TLS Handshake against the expected credentials for presented in the TLS Handshake against the expected credentials for
that client. The authorization server MUST enforce the binding that client. The authorization server MUST enforce the binding
between client and certificate as described in either Section 2.1 or between client and certificate as described in either Section 2.1 or
Section 2.2 below. If the presented certificate doesn't match that Section 2.2 below. If no certificate is presented or that which is
which is expected for the given "client_id", the authorization server presented doesn't match that which is expected for the given
returns a normal OAuth 2.0 error response per Section 5.2 of RFC6749 "client_id", the authorization server returns a normal OAuth 2.0
[RFC6749] with the "invalid_client" error code to indicate failed error response per Section 5.2 of RFC6749 [RFC6749] with the
client authentication. "invalid_client" error code to indicate failed client authentication.
2.1. PKI Mutual TLS Method 2.1. PKI Mutual-TLS Method
The PKI (public key infrastructure) method of mutual TLS OAuth client The PKI (public key infrastructure) method of mutual-TLS OAuth client
authentication adheres to the way in which X.509 certificates are authentication adheres to the way in which X.509 certificates are
traditionally used for authentication. It relies on a validated traditionally used for authentication. It relies on a validated
certificate chain [RFC5280] and a single subject distinguished name certificate chain [RFC5280] and a single subject distinguished name
(DN) or a single subject alternative name (SAN) to authenticate the (DN) or a single subject alternative name (SAN) to authenticate the
client. Only one subject name value of any type is used for each client. Only one subject name value of any type is used for each
client. The TLS handshake is utilized to validate the client's client. The TLS handshake is utilized to validate the client's
possession of the private key corresponding to the public key in the possession of the private key corresponding to the public key in the
certificate and to validate the corresponding certificate chain. The certificate and to validate the corresponding certificate chain. The
client is successfully authenticated if the subject information in client is successfully authenticated if the subject information in
the certificate matches the single expected subject configured or the certificate matches the single expected subject configured or
skipping to change at page 7, line 7 skipping to change at page 7, line 9
client's registered DN). Revocation checking is possible with the client's registered DN). Revocation checking is possible with the
PKI method but if and how to check a certificate's revocation status PKI method but if and how to check a certificate's revocation status
is a deployment decision at the discretion of the authorization is a deployment decision at the discretion of the authorization
server. Clients can rotate their X.509 certificates without the need server. Clients can rotate their X.509 certificates without the need
to modify the respective authentication data at the authorization to modify the respective authentication data at the authorization
server by obtaining a new certificate with the same subject from a server by obtaining a new certificate with the same subject from a
trusted certificate authority (CA). trusted certificate authority (CA).
2.1.1. PKI Method Metadata Value 2.1.1. PKI Method Metadata Value
For the PKI method of mutual TLS client authentication, this For the PKI method of mutual-TLS client authentication, this
specification defines and registers the following authentication specification defines and registers the following authentication
method metadata value into the "OAuth Token Endpoint Authentication method metadata value into the "OAuth Token Endpoint Authentication
Methods" registry [IANA.OAuth.Parameters]. Methods" registry [IANA.OAuth.Parameters].
tls_client_auth tls_client_auth
Indicates that client authentication to the authorization server Indicates that client authentication to the authorization server
will occur with mutual TLS utilizing the PKI method of associating will occur with mutual TLS utilizing the PKI method of associating
a certificate to a client. a certificate to a client.
2.1.2. Client Registration Metadata 2.1.2. Client Registration Metadata
In order to convey the expected subject of the certificate, the In order to convey the expected subject of the certificate, the
following metadata parameters are introduced for the OAuth 2.0 following metadata parameters are introduced for the OAuth 2.0
Dynamic Client Registration Protocol [RFC7591] in support of the PKI Dynamic Client Registration Protocol [RFC7591] in support of the PKI
method of mutual TLS client authentication. A client using the method of mutual-TLS client authentication. A client using the
"tls_client_auth" authentication method MUST use exactly one of the "tls_client_auth" authentication method MUST use exactly one of the
below metadata parameters to indicate the certificate subject value below metadata parameters to indicate the certificate subject value
that the authorization server is to expect when authenticating the that the authorization server is to expect when authenticating the
respective client. respective client.
tls_client_auth_subject_dn tls_client_auth_subject_dn
An [RFC4514] string representation of the expected subject An [RFC4514] string representation of the expected subject
distinguished name of the certificate, which the OAuth client will distinguished name of the certificate, which the OAuth client will
use in mutual TLS authentication. use in mutual-TLS authentication.
tls_client_auth_san_dns tls_client_auth_san_dns
A string containing the value of an expected dNSName SAN entry in A string containing the value of an expected dNSName SAN entry in
the certificate, which the OAuth client will use in mutual TLS the certificate, which the OAuth client will use in mutual-TLS
authentication. authentication.
tls_client_auth_san_uri tls_client_auth_san_uri
A string containing the value of an expected A string containing the value of an expected
uniformResourceIdentifier SAN entry in the certificate, which the uniformResourceIdentifier SAN entry in the certificate, which the
OAuth client will use in mutual TLS authentication. OAuth client will use in mutual-TLS authentication.
tls_client_auth_san_ip tls_client_auth_san_ip
A string representation of an IP address in either dotted decimal A string representation of an IP address in either dotted decimal
notation (for IPv4) or colon-delimited hexadecimal (for IPv6, as notation (for IPv4) or colon-delimited hexadecimal (for IPv6, as
defined in [RFC4291] section 2.2) that is expected to be present defined in [RFC5952]) that is expected to be present as an
as an iPAddress SAN entry in the certificate, which the OAuth iPAddress SAN entry in the certificate, which the OAuth client
client will use in mutual TLS authentication. will use in mutual-TLS authentication. Per section 8 of [RFC5952]
the IP address comparison of the value in this parameter and the
SAN entry in the certificate is to be done in binary format.
tls_client_auth_san_email tls_client_auth_san_email
A string containing the value of an expected rfc822Name SAN entry A string containing the value of an expected rfc822Name SAN entry
in the certificate, which the OAuth client will use in mutual TLS in the certificate, which the OAuth client will use in mutual-TLS
authentication. authentication.
2.2. Self-Signed Certificate Mutual TLS Method 2.2. Self-Signed Certificate Mutual-TLS Method
This method of mutual TLS OAuth client authentication is intended to This method of mutual-TLS OAuth client authentication is intended to
support client authentication using self-signed certificates. As a support client authentication using self-signed certificates. As a
prerequisite, the client registers its X.509 certificates (using prerequisite, the client registers its X.509 certificates (using
"jwks" defined in [RFC7591]) or a reference to a trusted source for "jwks" defined in [RFC7591]) or a reference to a trusted source for
its X.509 certificates (using "jwks_uri" from [RFC7591]) with the its X.509 certificates (using "jwks_uri" from [RFC7591]) with the
authorization server. During authentication, TLS is utilized to authorization server. During authentication, TLS is utilized to
validate the client's possession of the private key corresponding to validate the client's possession of the private key corresponding to
the public key presented within the certificate in the respective TLS the public key presented within the certificate in the respective TLS
handshake. In contrast to the PKI method, the client's certificate handshake. In contrast to the PKI method, the client's certificate
chain is not validated by the server in this case. The client is chain is not validated by the server in this case. The client is
successfully authenticated if the certificate that it presented successfully authenticated if the certificate that it presented
during the handshake matches one of the certificates configured or during the handshake matches one of the certificates configured or
registered for that particular client. The Self-Signed Certificate registered for that particular client. The Self-Signed Certificate
method allows the use of mutual TLS to authenticate clients without method allows the use of mutual TLS to authenticate clients without
the need to maintain a PKI. When used in conjunction with a the need to maintain a PKI. When used in conjunction with a
"jwks_uri" for the client, it also allows the client to rotate its "jwks_uri" for the client, it also allows the client to rotate its
X.509 certificates without the need to change its respective X.509 certificates without the need to change its respective
authentication data directly with the authorization server. authentication data directly with the authorization server.
2.2.1. Self-Signed Method Metadata Value 2.2.1. Self-Signed Method Metadata Value
For the Self-Signed Certificate method of mutual TLS client For the Self-Signed Certificate method of mutual-TLS client
authentication, this specification defines and registers the authentication, this specification defines and registers the
following authentication method metadata value into the "OAuth Token following authentication method metadata value into the "OAuth Token
Endpoint Authentication Methods" registry [IANA.OAuth.Parameters]. Endpoint Authentication Methods" registry [IANA.OAuth.Parameters].
self_signed_tls_client_auth self_signed_tls_client_auth
Indicates that client authentication to the authorization server Indicates that client authentication to the authorization server
will occur using mutual TLS with the client utilizing a self- will occur using mutual TLS with the client utilizing a self-
signed certificate. signed certificate.
2.2.2. Client Registration Metadata 2.2.2. Client Registration Metadata
skipping to change at page 9, line 11 skipping to change at page 9, line 15
"jwks_uri" parameter is a URL that references a client's JWK Set. A "jwks_uri" parameter is a URL that references a client's JWK Set. A
certificate is represented with the "x5c" parameter of an individual certificate is represented with the "x5c" parameter of an individual
JWK within the set. Note that the members of the JWK representing JWK within the set. Note that the members of the JWK representing
the public key (e.g. "n" and "e" for RSA, "x" and "y" for EC) are the public key (e.g. "n" and "e" for RSA, "x" and "y" for EC) are
required parameters per [RFC7518] so will be present even though they required parameters per [RFC7518] so will be present even though they
are not utilized in this context. Also note that that Section 4.7 of are not utilized in this context. Also note that that Section 4.7 of
[RFC7517] requires that the key in the first certificate of the "x5c" [RFC7517] requires that the key in the first certificate of the "x5c"
parameter match the public key represented by those other members of parameter match the public key represented by those other members of
the JWK. the JWK.
3. Mutual TLS Client Certificate-Bound Access Tokens 3. Mutual-TLS Client Certificate-Bound Access Tokens
When mutual TLS is used by the client on the connection to the token When mutual TLS is used by the client on the connection to the token
endpoint, the authorization server is able to bind the issued access endpoint, the authorization server is able to bind the issued access
token to the client certificate. Such a binding is accomplished by token to the client certificate. Such a binding is accomplished by
associating the certificate with the token in a way that can be associating the certificate with the token in a way that can be
accessed by the protected resource, such as embedding the certificate accessed by the protected resource, such as embedding the certificate
hash in the issued access token directly, using the syntax described hash in the issued access token directly, using the syntax described
in Section 3.1, or through token introspection as described in in Section 3.1, or through token introspection as described in
Section 3.2. Binding the access token to the client certificate in Section 3.2. Binding the access token to the client certificate in
that fashion has the benefit of decoupling that binding from the that fashion has the benefit of decoupling that binding from the
client's authentication with the authorization server, which enables client's authentication with the authorization server, which enables
mutual TLS during protected resource access to serve purely as a mutual TLS during protected resource access to serve purely as a
proof-of-possession mechanism. Other methods of associating a proof-of-possession mechanism. Other methods of associating a
certificate with an access token are possible, per agreement by the certificate with an access token are possible, per agreement by the
authorization server and the protected resource, but are beyond the authorization server and the protected resource, but are beyond the
scope of this specification. scope of this specification.
The client makes protected resource requests as described in In order for a resource server to use certificate-bound access
[RFC6750], however, those requests MUST be made over a mutually tokens, it must have advance knowledge that mutual TLS is to be used
authenticated TLS connection using the same certificate that was used for some or all resource accesses. In particular, the access token
for mutual TLS at the token endpoint. itself cannot be used as input to the decision of whether or not to
request mutual TLS, since from the TLS perspective those are
"Application Data", only exchanged after the TLS handshake has been
completed, and the initial CertificateRequest occurs during the
handshake, before the Application Data is available. Although
subsequent opportunities for a TLS client to present a certificate
may be available, e.g., via TLS 1.2 renegotiation [RFC5246] or TLS
1.3 post-handshake authentication [RFC8446], this document makes no
provision for their usage. It is expected to be common that a
mutual-TLS-using resource server will require mutual TLS for all
resources hosted thereupon, or will serve mutual-TLS-protected and
regular resources on separate hostname+port combinations, though
other workflows are possible. How resource server policy is
synchronized with the AS is out of scope for this document.
Within the scope of an mutual-TLS-protected resource-access flow, the
client makes protected resource requests as described in [RFC6750],
however, those requests MUST be made over a mutually authenticated
TLS connection using the same certificate that was used for mutual
TLS at the token endpoint.
The protected resource MUST obtain, from its TLS implementation The protected resource MUST obtain, from its TLS implementation
layer, the client certificate used for mutual TLS and MUST verify layer, the client certificate used for mutual TLS and MUST verify
that the certificate matches the certificate associated with the that the certificate matches the certificate associated with the
access token. If they do not match, the resource access attempt MUST access token. If they do not match, the resource access attempt MUST
be rejected with an error per [RFC6750] using an HTTP 401 status code be rejected with an error per [RFC6750] using an HTTP 401 status code
and the "invalid_token" error code. and the "invalid_token" error code.
Metadata to convey server and client capabilities for mutual TLS Metadata to convey server and client capabilities for mutual-TLS
client certificate-bound access tokens is defined in Section 3.3 and client certificate-bound access tokens is defined in Section 3.3 and
Section 3.4 respectively. Section 3.4 respectively.
3.1. JWT Certificate Thumbprint Confirmation Method 3.1. JWT Certificate Thumbprint Confirmation Method
When access tokens are represented as JSON Web Tokens (JWT)[RFC7519], When access tokens are represented as JSON Web Tokens (JWT)[RFC7519],
the certificate hash information SHOULD be represented using the the certificate hash information SHOULD be represented using the
"x5t#S256" confirmation method member defined herein. "x5t#S256" confirmation method member defined herein.
To represent the hash of a certificate in a JWT, this specification To represent the hash of a certificate in a JWT, this specification
skipping to change at page 10, line 41 skipping to change at page 11, line 25
Figure 2: Example JWT Claims Set with an X.509 Certificate Thumbprint Figure 2: Example JWT Claims Set with an X.509 Certificate Thumbprint
Confirmation Method Confirmation Method
3.2. Confirmation Method for Token Introspection 3.2. Confirmation Method for Token Introspection
OAuth 2.0 Token Introspection [RFC7662] defines a method for a OAuth 2.0 Token Introspection [RFC7662] defines a method for a
protected resource to query an authorization server about the active protected resource to query an authorization server about the active
state of an access token as well as to determine meta-information state of an access token as well as to determine meta-information
about the token. about the token.
For a mutual TLS client certificate-bound access token, the hash of For a mutual-TLS client certificate-bound access token, the hash of
the certificate to which the token is bound is conveyed to the the certificate to which the token is bound is conveyed to the
protected resource as meta-information in a token introspection protected resource as meta-information in a token introspection
response. The hash is conveyed using the same "cnf" with "x5t#S256" response. The hash is conveyed using the same "cnf" with "x5t#S256"
member structure as the certificate SHA-256 thumbprint confirmation member structure as the certificate SHA-256 thumbprint confirmation
method, described in Section 3.1, as a top-level member of the method, described in Section 3.1, as a top-level member of the
introspection response JSON. The protected resource compares that introspection response JSON. The protected resource compares that
certificate hash to a hash of the client certificate used for mutual certificate hash to a hash of the client certificate used for mutual-
TLS authentication and rejects the request, if they do not match. TLS authentication and rejects the request, if they do not match.
The following is an example of an introspection response for an The following is an example of an introspection response for an
active token with an "x5t#S256" certificate thumbprint confirmation active token with an "x5t#S256" certificate thumbprint confirmation
method. The new introspection response content introduced by this method. The new introspection response content introduced by this
specification is the "cnf" confirmation method at the bottom of the specification is the "cnf" confirmation method at the bottom of the
example that has the "x5t#S256" confirmation method member containing example that has the "x5t#S256" confirmation method member containing
the value that is the hash of the client certificate to which the the value that is the hash of the client certificate to which the
access token is bound. access token is bound.
skipping to change at page 11, line 30 skipping to change at page 12, line 25
"x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2" "x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2"
} }
} }
Figure 3: Example Introspection Response for a Certificate-Bound Figure 3: Example Introspection Response for a Certificate-Bound
Access Token Access Token
3.3. Authorization Server Metadata 3.3. Authorization Server Metadata
This document introduces the following new authorization server This document introduces the following new authorization server
metadata parameter to signal the server's capability to issue metadata [RFC8414] parameter to signal the server's capability to
certificate bound access tokens: issue certificate bound access tokens:
tls_client_certificate_bound_access_tokens tls_client_certificate_bound_access_tokens
OPTIONAL. Boolean value indicating server support for mutual TLS OPTIONAL. Boolean value indicating server support for mutual-TLS
client certificate-bound access tokens. If omitted, the default client certificate-bound access tokens. If omitted, the default
value is "false". value is "false".
3.4. Client Registration Metadata 3.4. Client Registration Metadata
The following new client metadata parameter is introduced to convey The following new client metadata parameter is introduced to convey
the client's intention to use certificate bound access tokens: the client's intention to use certificate bound access tokens:
tls_client_certificate_bound_access_tokens tls_client_certificate_bound_access_tokens
OPTIONAL. Boolean value used to indicate the client's intention OPTIONAL. Boolean value used to indicate the client's intention
to use mutual TLS client certificate-bound access tokens. If to use mutual-TLS client certificate-bound access tokens. If
omitted, the default value is "false". omitted, the default value is "false".
Note that, if a client that has indicated the intention to use
mutual-TLS client certificate-bound tokens makes a request to the
token endpoint over a non-mutual-TLS connection, it is at the
authorization server's discretion as to whether to return an error or
issue an unbound token.
4. Public Clients and Certificate-Bound Tokens 4. Public Clients and Certificate-Bound Tokens
Mutual TLS OAuth client authentication and certificate-bound access Mutual-TLS OAuth client authentication and certificate-bound access
tokens can be used independently of each other. Use of certificate- tokens can be used independently of each other. Use of certificate-
bound access tokens without mutual TLS OAuth client authentication, bound access tokens without mutual-TLS OAuth client authentication,
for example, is possible in support of binding access tokens to a TLS for example, is possible in support of binding access tokens to a TLS
client certificate for public clients (those without authentication client certificate for public clients (those without authentication
credentials associated with the "client_id"). The authorization credentials associated with the "client_id"). The authorization
server would configure the TLS stack in the same manner as for the server would configure the TLS stack in the same manner as for the
Self-Signed Certificate method such that it does not verify that the Self-Signed Certificate method such that it does not verify that the
certificate presented by the client during the handshake is signed by certificate presented by the client during the handshake is signed by
a trusted CA. Individual instances of a client would create a self- a trusted CA. Individual instances of a client would create a self-
signed certificate for mutual TLS with both the authorization server signed certificate for mutual TLS with both the authorization server
and resource server. The authorization server would not use the and resource server. The authorization server would not use the
mutual TLS certificate to authenticate the client at the OAuth layer mutual-TLS certificate to authenticate the client at the OAuth layer
but would bind the issued access token to that certificate, for which but would bind the issued access token to that certificate, for which
the client has proven possession of the corresponding private key. the client has proven possession of the corresponding private key.
The access token is then bound to the certificate and can only be The access token is then bound to the certificate and can only be
used by the client possessing the certificate and corresponding used by the client possessing the certificate and corresponding
private key and utilizing them to negotiate mutual TLS on connections private key and utilizing them to negotiate mutual TLS on connections
to the resource server. When the authorization server issues a to the resource server. When the authorization server issues a
refresh token to such a client, it SHOULD also bind the refresh token refresh token to such a client, it SHOULD also bind the refresh token
to the respective certificate. And check the binding when the to the respective certificate. And check the binding when the
refresh token is presented to get new access tokens. The refresh token is presented to get new access tokens. The
implementation details of the binding the refresh token are at the implementation details of the binding the refresh token are at the
discretion of the authorization server. discretion of the authorization server.
5. Metadata for Mutual TLS Endpoint Aliases 5. Metadata for Mutual-TLS Endpoint Aliases
The process of negotiating client certificate-based mutual TLS The process of negotiating client certificate-based mutual TLS
involves a TLS server requesting a certificate from the TLS client involves a TLS server requesting a certificate from the TLS client
(the client does not provide one unsolicited). Although a server can (the client does not provide one unsolicited). Although a server can
be configured such that client certificates are optional, meaning be configured such that client certificates are optional, meaning
that the connection is allowed to continue when the client does not that the connection is allowed to continue when the client does not
provide a certificate, the act of a server requesting a certificate provide a certificate, the act of a server requesting a certificate
can result in undesirable behavior from some clients. This is can result in undesirable behavior from some clients. This is
particularly true of web browsers as TLS clients, which will particularly true of web browsers as TLS clients, which will
typically present the end-user with an intrusive certificate typically present the end-user with an intrusive certificate
selection interface when the server requests a certificate. selection interface when the server requests a certificate.
Authorization servers supporting both clients using mutual TLS and Authorization servers supporting both clients using mutual TLS and
conventional clients MAY chose to isolate the server side mutual TLS conventional clients MAY chose to isolate the server side mutual-TLS
behaviour to only clients intending to do mutual TLS, thus avoiding behavior to only clients intending to do mutual TLS, thus avoiding
any undesirable effects it might have on conventional clients. The any undesirable effects it might have on conventional clients. The
following authorization server metadata parameter is introduced to following authorization server metadata parameter is introduced to
facilitate such separation: facilitate such separation:
mtls_endpoint_aliases mtls_endpoint_aliases
OPTIONAL. A JSON object containing alternative authorization OPTIONAL. A JSON object containing alternative authorization
server endpoints that, when present, an OAuth client intending to server endpoints that, when present, an OAuth client intending to
do mutual TLS uses in preference to the conventional endpoints. do mutual TLS uses in preference to the conventional endpoints.
The parameter value itself consists of one or more endpoint The parameter value itself consists of one or more endpoint
parameters, such as "token_endpoint", "revocation_endpoint", parameters, such as "token_endpoint", "revocation_endpoint",
skipping to change at page 13, line 30 skipping to change at page 14, line 30
do not define endpoints to which an OAuth client makes a direct do not define endpoints to which an OAuth client makes a direct
request have no meaning and SHOULD be ignored. request have no meaning and SHOULD be ignored.
Below is an example of an authorization server metadata document with Below is an example of an authorization server metadata document with
the "mtls_endpoint_aliases" parameter, which indicates aliases for the "mtls_endpoint_aliases" parameter, which indicates aliases for
the token, revocation, and introspection endpoints that an OAuth the token, revocation, and introspection endpoints that an OAuth
client intending to do mutual TLS would in preference to the client intending to do mutual TLS would in preference to the
conventional token, revocation, and introspection endpoints. Note conventional token, revocation, and introspection endpoints. Note
that the endpoints in "mtls_endpoint_aliases" use a different host that the endpoints in "mtls_endpoint_aliases" use a different host
than their conventional counterparts, which allows the authorization than their conventional counterparts, which allows the authorization
server (via SNI or actual distinct hosts) to differentiate its TLS server (via TLS "server_name" extension [RFC6066] or actual distinct
behavior as appropriate. hosts) to differentiate its TLS behavior as appropriate.
{ {
"issuer": "https://server.example.com", "issuer": "https://server.example.com",
"authorization_endpoint": "https://server.example.com/authz", "authorization_endpoint": "https://server.example.com/authz",
"token_endpoint": "https://server.example.com/token", "token_endpoint": "https://server.example.com/token",
"introspection_endpoint": "https://server.example.com/introspect", "introspection_endpoint": "https://server.example.com/introspect",
"revocation_endpoint": "https://server.example.com/revo", "revocation_endpoint": "https://server.example.com/revo",
"jwks_uri": "https://server.example.com/jwks", "jwks_uri": "https://server.example.com/jwks",
"response_types_supported": ["code"], "response_types_supported": ["code"],
"response_modes_supported": ["fragment","query","form_post"], "response_modes_supported": ["fragment","query","form_post"],
skipping to change at page 14, line 25 skipping to change at page 15, line 25
"token_endpoint_auth_methods_supported": "token_endpoint_auth_methods_supported":
["tls_client_auth","client_secret_basic","none"], ["tls_client_auth","client_secret_basic","none"],
"tls_client_certificate_bound_access_tokens": true "tls_client_certificate_bound_access_tokens": true
"mtls_endpoint_aliases": { "mtls_endpoint_aliases": {
"token_endpoint": "https://mtls.example.com/token", "token_endpoint": "https://mtls.example.com/token",
"revocation_endpoint": "https://mtls.example.com/revo", "revocation_endpoint": "https://mtls.example.com/revo",
"introspection_endpoint": "https://mtls.example.com/introspect" "introspection_endpoint": "https://mtls.example.com/introspect"
} }
} }
Figure 4: Example Authorization Server Metadata with Mutual TLS Figure 4: Example Authorization Server Metadata with Mutual-TLS
Endpoint Aliases Endpoint Aliases
6. Implementation Considerations 6. Implementation Considerations
6.1. Authorization Server 6.1. Authorization Server
The authorization server needs to set up its TLS configuration The authorization server needs to set up its TLS configuration
appropriately for the OAuth client authentication methods it appropriately for the OAuth client authentication methods it
supports. supports.
An authorization server that supports mutual TLS client An authorization server that supports mutual-TLS client
authentication and other client authentication methods or public authentication and other client authentication methods or public
clients in parallel would make mutual TLS optional (i.e. allowing a clients in parallel would make mutual TLS optional (i.e. allowing a
handshake to continue after the server requests a client certificate handshake to continue after the server requests a client certificate
but the client does not send one). but the client does not send one).
In order to support the Self-Signed Certificate method, the In order to support the Self-Signed Certificate method alone, the
authorization server would configure the TLS stack in such a way that authorization server would configure the TLS stack in such a way that
it does not verify whether the certificate presented by the client it does not verify whether the certificate presented by the client
during the handshake is signed by a trusted CA certificate. during the handshake is signed by a trusted CA certificate.
As described in Section 3, the authorization server binds the issued As described in Section 3, the authorization server binds the issued
access token to the TLS client certificate, which means that it will access token to the TLS client certificate, which means that it will
only issue certificate-bound tokens for a certificate which the only issue certificate-bound tokens for a certificate which the
client has proven possession of the corresponding private key. client has proven possession of the corresponding private key.
The authorization server may also consider hosting the token The authorization server may also consider hosting the token
skipping to change at page 15, line 23 skipping to change at page 16, line 23
mutual TLS will use in preference to the conventional endpoints. mutual TLS will use in preference to the conventional endpoints.
6.2. Resource Server 6.2. Resource Server
OAuth divides the roles and responsibilities such that the resource OAuth divides the roles and responsibilities such that the resource
server relies on the authorization server to perform client server relies on the authorization server to perform client
authentication and obtain resource owner (end-user) authorization. authentication and obtain resource owner (end-user) authorization.
The resource server makes authorization decisions based on the access The resource server makes authorization decisions based on the access
token presented by the client but does not directly authenticate the token presented by the client but does not directly authenticate the
client per se. The manner in which an access token is bound to the client per se. The manner in which an access token is bound to the
client certificate decouples it from the specific method that the client certificate and how a protected resource verifies the proof-
client used to authenticate with the authorization server. Mutual of-possession decouples that from the specific method that the client
TLS during protected resource access can therefore serve purely as a used to authenticate with the authorization server. Mutual TLS
during protected resource access can therefore serve purely as a
proof-of-possession mechanism. As such, it is not necessary for the proof-of-possession mechanism. As such, it is not necessary for the
resource server to validate the trust chain of the client's resource server to validate the trust chain of the client's
certificate in any of the methods defined in this document. The certificate in any of the methods defined in this document. The
resource server would therefore configure the TLS stack in a way that resource server would therefore configure the TLS stack in a way that
it does not verify whether the certificate presented by the client it does not verify whether the certificate presented by the client
during the handshake is signed by a trusted CA certificate. during the handshake is signed by a trusted CA certificate.
6.3. Certificate Expiration and Bound Access Tokens 6.3. Certificate Expiration and Bound Access Tokens
As described in Section 3, an access token is bound to a specific As described in Section 3, an access token is bound to a specific
skipping to change at page 16, line 27 skipping to change at page 17, line 28
7. Security Considerations 7. Security Considerations
7.1. Certificate-Bound Refresh Tokens 7.1. Certificate-Bound Refresh Tokens
The OAuth 2.0 Authorization Framework [RFC6749] requires that an The OAuth 2.0 Authorization Framework [RFC6749] requires that an
authorization server bind refresh tokens to the client to which they authorization server bind refresh tokens to the client to which they
were issued and that confidential clients (those having established were issued and that confidential clients (those having established
authentication credentials with the authorization server) authentication credentials with the authorization server)
authenticate to the AS when presenting a refresh token. As a result, authenticate to the AS when presenting a refresh token. As a result,
refresh tokens are indirectly certificate-bound when issued to refresh tokens are indirectly certificate-bound by way of the client
clients utilizing the "tls_client_auth" or ID and the associated requirement for (certificate-based)
"self_signed_tls_client_auth" methods of client authentication. authentication to the authorization server when issued to clients
Section 4 describes certificate-bound refresh tokens issued to public utilizing the "tls_client_auth" or "self_signed_tls_client_auth"
clients (those without authentication credentials associated with the methods of client authentication. Section 4 describes certificate-
"client_id"). bound refresh tokens issued to public clients (those without
authentication credentials associated with the "client_id").
7.2. Certificate Thumbprint Binding 7.2. Certificate Thumbprint Binding
The binding between the certificate and access token specified in The binding between the certificate and access token specified in
Section 3.1 uses a cryptographic hash of the certificate. It relies Section 3.1 uses a cryptographic hash of the certificate. It relies
on the hash function having sufficient preimage and second-preimage on the hash function having sufficient second-preimage resistance so
resistance so as to make it computationally infeasible to find or as to make it computationally infeasible to find or create another
create another certificate that produces to the same hash output certificate that produces to the same hash output value. The SHA-256
value. The SHA-256 hash function was used because it meets the hash function was used because it meets the aforementioned
aforementioned requirement while being widely available. If, in the requirement while being widely available. If, in the future,
future, certificate thumbprints need to be computed using hash certificate thumbprints need to be computed using hash function(s)
function(s) other than SHA-256, it is suggested that additional other than SHA-256, it is suggested that additional related JWT
related JWT confirmation methods members be defined for that purpose confirmation methods members be defined for that purpose and
and registered in the IANA "JWT Confirmation Methods" registry registered in the IANA "JWT Confirmation Methods" registry
[IANA.JWT.Claims] for JWT "cnf" member values. [IANA.JWT.Claims] for JWT "cnf" member values.
Community knowledge about the strength of various algorithms and
feasible attacks can change suddenly, and experience shows that a
document about security is a point-in-time statement. Readers are
advised to seek out any errata or updates that apply to this
document.
7.3. TLS Versions and Best Practices 7.3. TLS Versions and Best Practices
In the abstract this document is applicable with any TLS version In the abstract this document is applicable with any TLS version
supporting certificate-based client authentication. Both TLS 1.3 supporting certificate-based client authentication. Both TLS 1.3
[RFC8446] and TLS 1.2 [RFC5246] are cited herein because, at the time [RFC8446] and TLS 1.2 [RFC5246] are cited herein because, at the time
of writing, 1.3 is the newest version while 1.2 is the most widely of writing, 1.3 is the newest version while 1.2 is the most widely
deployed. General implementation and security considerations for deployed. General implementation and security considerations for
TLS, including version recommendations, can be found in [BCP195]. TLS, including version recommendations, can be found in [BCP195].
TLS certificate validation (for both client and server certificates)
requires a local database of trusted certificate authorities (CAs).
Decisions about what CAs to trust and how to make such a
determination of trust are out of scope for this document.
7.4. X.509 Certificate Spoofing 7.4. X.509 Certificate Spoofing
If the PKI method of client authentication is used, an attacker could If the PKI method of client authentication is used, an attacker could
try to impersonate a client using a certificate with the same subject try to impersonate a client using a certificate with the same subject
(DN or SAN) but issued by a different CA, which the authorization (DN or SAN) but issued by a different CA, which the authorization
server trusts. To cope with that threat, the authorization server server trusts. To cope with that threat, the authorization server
SHOULD only accept as trust anchors a limited number of CAs whose SHOULD only accept as trust anchors a limited number of CAs whose
certificate issuance policy meets its security requirements. There certificate issuance policy meets its security requirements. There
is an assumption then that the client and server agree on the set of is an assumption then that the client and server agree out of band on
trust anchors that the server uses to create and validate the the set of trust anchors that the server uses to create and validate
certificate chain. Without this assumption the use of a subject to the certificate chain. Without this assumption the use of a subject
identify the client certificate would open the server up to to identify the client certificate would open the server up to
certificate spoofing attacks. certificate spoofing attacks.
7.5. X.509 Certificate Parsing and Validation Complexity 7.5. X.509 Certificate Parsing and Validation Complexity
Parsing and validation of X.509 certificates and certificate chains Parsing and validation of X.509 certificates and certificate chains
is complex and implementation mistakes have previously exposed is complex and implementation mistakes have previously exposed
security vulnerabilities. Complexities of validation include (but security vulnerabilities. Complexities of validation include (but
are not limited to) [CX5P] [DCW] [RFC5280]: are not limited to) [CX5P] [DCW] [RFC5280]:
o checking of Basic Constraints, basic and extended Key Usage o checking of Basic Constraints, basic and extended Key Usage
constraints, validity periods, and critical extensions; constraints, validity periods, and critical extensions;
o handling of null-terminator bytes and non-canonical string o handling of embedded NUL bytes in ASN.1 counted-length strings,
representations in subject names; and non-canonical or non-normalized string representations in
subject names;
o handling of wildcard patterns in subject names; o handling of wildcard patterns in subject names;
o recursive verification of certificate chains and checking o recursive verification of certificate chains and checking
certificate revocation. certificate revocation.
For these reasons, implementors SHOULD use an established and well- For these reasons, implementors SHOULD use an established and well-
tested X.509 library (such as one used by an established TLS library) tested X.509 library (such as one used by an established TLS library)
for validation of X.509 certificate chains and SHOULD NOT attempt to for validation of X.509 certificate chains and SHOULD NOT attempt to
write their own X.509 certificate validation procedures. write their own X.509 certificate validation procedures.
skipping to change at page 18, line 34 skipping to change at page 19, line 44
JWT "cnf" member values established by [RFC7800]. JWT "cnf" member values established by [RFC7800].
o Confirmation Method Value: "x5t#S256" o Confirmation Method Value: "x5t#S256"
o Confirmation Method Description: X.509 Certificate SHA-256 o Confirmation Method Description: X.509 Certificate SHA-256
Thumbprint Thumbprint
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this specification ]] o Specification Document(s): Section 3.1 of [[ this specification ]]
9.2. Authorization Server Metadata Registration 9.2. Authorization Server Metadata Registration
This specification requests registration of the following value in This specification requests registration of the following values in
the IANA "OAuth Authorization Server Metadata" registry the IANA "OAuth Authorization Server Metadata" registry
[IANA.OAuth.Parameters] established by [RFC8414]. [IANA.OAuth.Parameters] established by [RFC8414].
o Metadata Name: "tls_client_certificate_bound_access_tokens" o Metadata Name: "tls_client_certificate_bound_access_tokens"
o Metadata Description: Indicates authorization server support for o Metadata Description: Indicates authorization server support for
mutual TLS client certificate-bound access tokens. mutual-TLS client certificate-bound access tokens.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 3.3 of [[ this specification ]] o Specification Document(s): Section 3.3 of [[ this specification ]]
o Metadata Name: "mtls_endpoint_aliases" o Metadata Name: "mtls_endpoint_aliases"
o Metadata Description: JSON object containing alternative o Metadata Description: JSON object containing alternative
authorization server endpoints, which a client intending to do authorization server endpoints, which a client intending to do
mutual TLS will use in preference to the conventional endpoints. mutual TLS will use in preference to the conventional endpoints.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 5 of [[ this specification ]] o Specification Document(s): Section 5 of [[ this specification ]]
9.3. Token Endpoint Authentication Method Registration 9.3. Token Endpoint Authentication Method Registration
This specification requests registration of the following value in This specification requests registration of the following values in
the IANA "OAuth Token Endpoint Authentication Methods" registry the IANA "OAuth Token Endpoint Authentication Methods" registry
[IANA.OAuth.Parameters] established by [RFC7591]. [IANA.OAuth.Parameters] established by [RFC7591].
o Token Endpoint Authentication Method Name: "tls_client_auth" o Token Endpoint Authentication Method Name: "tls_client_auth"
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 2.1.1 of [[ this specification o Specification Document(s): Section 2.1.1 of [[ this specification
]] ]]
o Token Endpoint Authentication Method Name: o Token Endpoint Authentication Method Name:
"self_signed_tls_client_auth" "self_signed_tls_client_auth"
skipping to change at page 20, line 13 skipping to change at page 21, line 16
o Specification Document(s): [RFC7800] and [[ this specification ]] o Specification Document(s): [RFC7800] and [[ this specification ]]
9.5. Dynamic Client Registration Metadata Registration 9.5. Dynamic Client Registration Metadata Registration
This specification requests registration of the following client This specification requests registration of the following client
metadata definitions in the IANA "OAuth Dynamic Client Registration metadata definitions in the IANA "OAuth Dynamic Client Registration
Metadata" registry [IANA.OAuth.Parameters] established by [RFC7591]: Metadata" registry [IANA.OAuth.Parameters] established by [RFC7591]:
o Client Metadata Name: "tls_client_certificate_bound_access_tokens" o Client Metadata Name: "tls_client_certificate_bound_access_tokens"
o Client Metadata Description: Indicates the client's intention to o Client Metadata Description: Indicates the client's intention to
use mutual TLS client certificate-bound access tokens. use mutual-TLS client certificate-bound access tokens.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 3.4 of [[ this specification ]] o Specification Document(s): Section 3.4 of [[ this specification ]]
o Client Metadata Name: "tls_client_auth_subject_dn" o Client Metadata Name: "tls_client_auth_subject_dn"
o Client Metadata Description: String value specifying the expected o Client Metadata Description: String value specifying the expected
subject DN of the client certificate. subject DN of the client certificate.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 2.1.2 of [[ this specification o Specification Document(s): Section 2.1.2 of [[ this specification
]] ]]
skipping to change at page 21, line 49 skipping to change at page 23, line 5
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012, RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>. <https://www.rfc-editor.org/info/rfc6749>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization [RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750, Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012, DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/info/rfc6750>. <https://www.rfc-editor.org/info/rfc6750>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)", Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016, RFC 7800, DOI 10.17487/RFC7800, April 2016,
<https://www.rfc-editor.org/info/rfc7800>. <https://www.rfc-editor.org/info/rfc7800>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/info/rfc8414>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
[SHS] National Institute of Standards and Technology, "Secure [SHS] National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", FIPS PUB 180-4, March 2012, Hash Standard (SHS)", FIPS PUB 180-4, March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/ <http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>. fips-180-4.pdf>.
[X690] International Telephone and Telegraph Consultative [X690] International Telephone and Telegraph Consultative
skipping to change at page 23, line 5 skipping to change at page 24, line 38
IANA, "OAuth Parameters", IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>. <http://www.iana.org/assignments/oauth-parameters>.
[OpenID.CIBA] [OpenID.CIBA]
Fernandez, G., Walter, F., Nennker, A., Tonge, D., and B. Fernandez, G., Walter, F., Nennker, A., Tonge, D., and B.
Campbell, "OpenID Connect Client Initiated Backchannel Campbell, "OpenID Connect Client Initiated Backchannel
Authentication Flow - Core 1.0", January 2019, Authentication Flow - Core 1.0", January 2019,
<https://openid.net/specs/openid-client-initiated- <https://openid.net/specs/openid-client-initiated-
backchannel-authentication-core-1_0.html>. backchannel-authentication-core-1_0.html>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4517] Legg, S., Ed., "Lightweight Directory Access Protocol [RFC4517] Legg, S., Ed., "Lightweight Directory Access Protocol
(LDAP): Syntaxes and Matching Rules", RFC 4517, (LDAP): Syntaxes and Matching Rules", RFC 4517,
DOI 10.17487/RFC4517, June 2006, DOI 10.17487/RFC4517, June 2006,
<https://www.rfc-editor.org/info/rfc4517>. <https://www.rfc-editor.org/info/rfc4517>.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952,
DOI 10.17487/RFC5952, August 2010,
<https://www.rfc-editor.org/info/rfc5952>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>.
[RFC7009] Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth [RFC7009] Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth
2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009, 2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009,
August 2013, <https://www.rfc-editor.org/info/rfc7009>. August 2013, <https://www.rfc-editor.org/info/rfc7009>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://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,
<https://www.rfc-editor.org/info/rfc7518>. <https://www.rfc-editor.org/info/rfc7518>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/info/rfc8414>.
Appendix A. Example "cnf" Claim, Certificate and JWK Appendix A. Example "cnf" Claim, Certificate and JWK
For reference, an "x5t#S256" value and the X.509 Certificate from For reference, an "x5t#S256" value and the X.509 Certificate from
which it was calculated are provided in the following examples, which it was calculated are provided in the following examples,
Figure 5 and Figure 6 respectively. A JWK representation of the Figure 5 and Figure 6 respectively. A JWK representation of the
certificate's public key along with the "x5c" member is also provided certificate's public key along with the "x5c" member is also provided
in Figure 7. in Figure 7.
"cnf":{"x5t#S256":"A4DtL2JmUMhAsvJj5tKyn64SqzmuXbMrJa0n761y5v0"} "cnf":{"x5t#S256":"A4DtL2JmUMhAsvJj5tKyn64SqzmuXbMrJa0n761y5v0"}
skipping to change at page 24, line 45 skipping to change at page 26, line 11
} }
Figure 7: JSON Web Key Figure 7: JSON Web Key
Appendix B. Relationship to Token Binding Appendix B. Relationship to Token Binding
OAuth 2.0 Token Binding [I-D.ietf-oauth-token-binding] enables the OAuth 2.0 Token Binding [I-D.ietf-oauth-token-binding] enables the
application of Token Binding to the various artifacts and tokens application of Token Binding to the various artifacts and tokens
employed throughout OAuth. That includes binding of an access token employed throughout OAuth. That includes binding of an access token
to a Token Binding key, which bears some similarities in motivation to a Token Binding key, which bears some similarities in motivation
and design to the mutual TLS client certificate-bound access tokens and design to the mutual-TLS client certificate-bound access tokens
defined in this document. Both documents define what is often called defined in this document. Both documents define what is often called
a proof-of-possession security mechanism for access tokens, whereby a a proof-of-possession security mechanism for access tokens, whereby a
client must demonstrate possession of cryptographic keying material client must demonstrate possession of cryptographic keying material
when accessing a protected resource. The details differ somewhat when accessing a protected resource. The details differ somewhat
between the two documents but both have the authorization server bind between the two documents but both have the authorization server bind
the access token that it issues to an asymmetric key pair held by the the access token that it issues to an asymmetric key pair held by the
client. The client then proves possession of the private key from client. The client then proves possession of the private key from
that pair with respect to the TLS connection over which the protected that pair with respect to the TLS connection over which the protected
resource is accessed. resource is accessed.
Token Binding uses bare keys that are generated on the client, which Token Binding uses bare keys that are generated on the client, which
avoids many of the difficulties of creating, distributing, and avoids many of the difficulties of creating, distributing, and
managing certificates used in this specification. However, at the managing certificates used in this specification. However, at the
time of writing, Token Binding is fairly new and there is relatively time of writing, Token Binding is fairly new and there is relatively
little support for it in available application development platforms little support for it in available application development platforms
and tooling. Until better support for the underlying core Token and tooling. Until better support for the underlying core Token
Binding specifications exists, practical implementations of OAuth 2.0 Binding specifications exists, practical implementations of OAuth 2.0
Token Binding are infeasible. Mutual TLS, on the other hand, has Token Binding are infeasible. Mutual TLS, on the other hand, has
been around for some time and enjoys widespread support in web been around for some time and enjoys widespread support in web
servers and development platforms. As a consequence, OAuth 2.0 servers and development platforms. As a consequence, OAuth 2.0
Mutual TLS Client Authentication and Certificate-Bound Access Tokens Mutual-TLS Client Authentication and Certificate-Bound Access Tokens
can be built and deployed now using existing platforms and tools. In can be built and deployed now using existing platforms and tools. In
the future, the two specifications are likely to be deployed in the future, the two specifications are likely to be deployed in
parallel for solving similar problems in different environments. parallel for solving similar problems in different environments.
Authorization servers may even support both specifications Authorization servers may even support both specifications
simultaneously using different proof-of-possession mechanisms for simultaneously using different proof-of-possession mechanisms for
tokens issued to different clients. tokens issued to different clients.
Appendix C. Acknowledgements Appendix C. Acknowledgements
Scott "not Tomlinson" Tomilson and Matt Peterson were involved in Scott "not Tomlinson" Tomilson and Matt Peterson were involved in
design and development work on a mutual TLS OAuth client design and development work on a mutual-TLS OAuth client
authentication implementation, which predates this document. authentication implementation, which predates this document.
Experience and learning from that work informed some of the content Experience and learning from that work informed some of the content
of this document. of this document.
This specification was developed within the OAuth Working Group under This specification was developed within the OAuth Working Group under
the chairmanship of Hannes Tschofenig and Rifaat Shekh-Yusef with the chairmanship of Hannes Tschofenig and Rifaat Shekh-Yusef with
Eric Rescorla, Benjamin Kaduk, and Roman Danyliw serving as Security Eric Rescorla, Benjamin Kaduk, and Roman Danyliw serving as Security
Area Directors. Additionally, the following individuals contributed Area Directors. Additionally, the following individuals contributed
ideas, feedback, and wording that helped shape this specification: ideas, feedback, and wording that helped shape this specification:
Vittorio Bertocci, Sergey Beryozkin, Ralph Bragg, Sophie Bremer, Vittorio Bertocci, Sergey Beryozkin, Ralph Bragg, Sophie Bremer,
Roman Danyliw, Vladimir Dzhuvinov, Samuel Erdtman, Evan Gilman, Leif Roman Danyliw, Vladimir Dzhuvinov, Samuel Erdtman, Evan Gilman, Leif
Johansson, Michael Jones, Phil Hunt, Benjamin Kaduk, Takahiko Johansson, Michael Jones, Phil Hunt, Benjamin Kaduk, Takahiko
Kawasaki, Sean Leonard, Kepeng Li, Neil Madden, James Manger, Jim Kawasaki, Sean Leonard, Kepeng Li, Neil Madden, James Manger, Jim
Manico, Nov Matake, Sascha Preibisch, Eric Rescorla, Justin Richer, Manico, Nov Matake, Sascha Preibisch, Eric Rescorla, Justin Richer,
Vincent Roca, Filip Skokan, Dave Tonge, and Hannes Tschofenig. Vincent Roca, Filip Skokan, Dave Tonge, and Hannes Tschofenig.
Appendix D. Document(s) History Appendix D. Document(s) History
[[ to be removed by the RFC Editor before publication as an RFC ]] [[ to be removed by the RFC Editor before publication as an RFC ]]
skipping to change at page 25, line 50 skipping to change at page 27, line 16
Roman Danyliw, Vladimir Dzhuvinov, Samuel Erdtman, Evan Gilman, Leif Roman Danyliw, Vladimir Dzhuvinov, Samuel Erdtman, Evan Gilman, Leif
Johansson, Michael Jones, Phil Hunt, Benjamin Kaduk, Takahiko Johansson, Michael Jones, Phil Hunt, Benjamin Kaduk, Takahiko
Kawasaki, Sean Leonard, Kepeng Li, Neil Madden, James Manger, Jim Kawasaki, Sean Leonard, Kepeng Li, Neil Madden, James Manger, Jim
Manico, Nov Matake, Sascha Preibisch, Eric Rescorla, Justin Richer, Manico, Nov Matake, Sascha Preibisch, Eric Rescorla, Justin Richer,
Vincent Roca, Filip Skokan, Dave Tonge, and Hannes Tschofenig. Vincent Roca, Filip Skokan, Dave Tonge, and Hannes Tschofenig.
Appendix D. Document(s) History Appendix D. Document(s) History
[[ to be removed by the RFC Editor before publication as an RFC ]] [[ to be removed by the RFC Editor before publication as an RFC ]]
draft-ietf-oauth-mtls-17
o Updates from IESG ballot position comments.
draft-ietf-oauth-mtls-16 draft-ietf-oauth-mtls-16
o Editorial updates from last call review. o Editorial updates from last call review.
draft-ietf-oauth-mtls-15 draft-ietf-oauth-mtls-15
o Editorial updates from second AD review. o Editorial updates from second AD review.
draft-ietf-oauth-mtls-14 draft-ietf-oauth-mtls-14
o Editorial clarifications around there being only a single subject o Editorial clarifications around there being only a single subject
registered/configured per client for the tls_client_auth method. registered/configured per client for the tls_client_auth method.
 End of changes. 76 change blocks. 
172 lines changed or deleted 225 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/