draft-ietf-oauth-mtls-02.txt   draft-ietf-oauth-mtls-03.txt 
OAuth Working Group B. Campbell OAuth Working Group B. Campbell
Internet-Draft J. Bradley Internet-Draft Ping Identity
Intended status: Standards Track Ping Identity Intended status: Standards Track J. Bradley
Expires: December 31, 2017 N. Sakimura Expires: January 28, 2018 Yubico
N. Sakimura
Nomura Research Institute Nomura Research Institute
T. Lodderstedt T. Lodderstedt
YES Europe AG YES Europe AG
June 29, 2017 July 27, 2017
Mutual TLS Profile for OAuth 2.0 Mutual TLS Profile for OAuth 2.0
draft-ietf-oauth-mtls-02 draft-ietf-oauth-mtls-03
Abstract Abstract
This document describes Transport Layer Security (TLS) mutual This document describes Transport Layer Security (TLS) mutual
authentication using X.509 certificates as a mechanism for both OAuth authentication using X.509 certificates as a mechanism for OAuth
client authentication to the token endpoint as well as for sender client authentication to the token endpoint as well as for
constrained access to OAuth protected resources. certificate bound sender constrained access tokens.
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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 31, 2017. This Internet-Draft will expire on January 28, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Notation and Conventions . . . . . . . . . . 3 1.1. Requirements Notation and Conventions . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Mutual TLS for Client Authentication . . . . . . . . . . . . 3 2. Mutual TLS for Client Authentication . . . . . . . . . . . . 4
2.1. Mutual TLS Client Authentication to the Token Endpoint . 3 2.1. Mutual TLS Client Authentication to the Token Endpoint . 4
2.2. Authorization Server Metadata . . . . . . . . . . . . . . 4 2.2. Authorization Server Metadata . . . . . . . . . . . . . . 5
2.3. Dynamic Client Registration . . . . . . . . . . . . . . . 4 2.3. Dynamic Client Registration . . . . . . . . . . . . . . . 5
3. Mutual TLS Sender Constrained Resources Access . . . . . . . 5 3. Mutual TLS Sender Constrained Resources Access . . . . . . . 6
3.1. X.509 Certificate SHA-256 Thumbprint Confirmation Method 3.1. X.509 Certificate SHA-256 Thumbprint Confirmation Method
for JWT . . . . . . . . . . . . . . . . . . . . . . . . . 5 for JWT . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Confirmation Method for Token Introspection . . . . . . . 6 3.2. Confirmation Method for Token Introspection . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4. Implementation Considerations . . . . . . . . . . . . . . . . 9
4.1. JWT Confirmation Methods Registration . . . . . . . . . . 7 4.1. Authorization Server . . . . . . . . . . . . . . . . . . 9
4.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 7 4.2. Resource Server . . . . . . . . . . . . . . . . . . . . . 9
4.2. Token Endpoint Authentication Method Registration . . . . 7 4.3. Sender Constrained Access Tokens Without Client
4.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 8 Authentication . . . . . . . . . . . . . . . . . . . . . 10
4.3. OAuth Token Introspection Response Registration . . . . . 8 4.4. Certificate Bound Access Tokens . . . . . . . . . . . . . 10
4.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
4.4. OAuth Dynamic Client Registration Metadata Registration . 8 5.1. JWT Confirmation Methods Registration . . . . . . . . . . 10
4.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 8 5.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5.2. OAuth Authorization Server Metadata Registration . . . . 11
5.1. TLS Versions and Best Practices . . . . . . . . . . . . . 8 5.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 11
5.2. Client Identity Binding by the Authorization Server . . . 9 5.3. Token Endpoint Authentication Method Registration . . . . 11
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 11
6.1. Normative References . . . . . . . . . . . . . . . . . . 9 5.4. OAuth Token Introspection Response Registration . . . . . 11
6.2. Informative References . . . . . . . . . . . . . . . . . 10 5.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11 5.5. OAuth Dynamic Client Registration Metadata Registration . 12
Appendix B. Document(s) History . . . . . . . . . . . . . . . . 11 5.5.1. Registry Contents . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6.1. TLS Versions and Best Practices . . . . . . . . . . . . . 12
6.2. X.509 Certificate Spoofing . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 15
Appendix B. Document(s) History . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
This document describes Transport Layer Security (TLS) mutual This document describes Transport Layer Security (TLS) mutual
authentication using X.509 certificates as a mechanism for both OAuth authentication using X.509 certificates as a mechanism for OAuth
client authentication to the token endpoint as well as for sender client authentication to the token endpoint as well as for sender
constrained access to OAuth protected resources. constrained access to OAuth protected resources.
The OAuth 2.0 Authorization Framework [RFC6749] defines a shared The OAuth 2.0 Authorization Framework [RFC6749] defines a shared
secret method of client authentication but also allows for the secret method of client authentication but also allows for the
definition and use of additional client authentication mechanisms definition and use of additional client authentication mechanisms
when interacting with the authorization server's token endpoint. when interacting with the authorization server's token endpoint.
This document describes an additional mechanism of client This document describes an additional mechanism of client
authentication utilizing mutual TLS [RFC5246] certificate-based authentication utilizing mutual TLS [RFC5246] certificate-based
authentication, which provides better security characteristics than authentication, which provides better security characteristics than
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For all access token requests to the token endpoint, regardless of For all access token requests to the token endpoint, regardless of
the grant type used, the client MUST include the "client_id" the grant type used, 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 and allows for trust models to vary as appropriate of the certificate and allows for trust models to vary as appropriate
for a given deployment. The authorization server can locate the for a given deployment. The authorization server can locate the
client configuration by the client identifier and check the client configuration by the client identifier and check the
certificate presented in the TLS Handshake against the expected certificate presented in the TLS Handshake against the expected
credentials for that client. As described in Section 5.2, the credentials for that client. The authorization server MUST enforce
authorization server MUST enforce some method of binding a some method of binding a certificate to a client. The following two
certificate to a client. binding methods are defined:
PKI The PKI method uses a distinguished name (DN) to identify the
client. The TLS handshake is utilized to validate the client's
possession of the private key corresponding to the public key in
the certificate and to validate the corresponding certificate
chain. The client is successfully authenticated if the subject
information in the certificate matches the configured DN. The
client may prescribe the DN of the issuer of its certificates.
The authorization server will enforce this restriction after the
TLS handshake took place. Setting the issuer to a certain CA
securely scopes the DN of the client to this CA and shall prevent
an attacker from impersonating a client by using a certificate for
the client's DN obtained from a different CA. The PKI method
facilitates the way X.509 certificates are traditionally being
used for authentication. It also allows the client to rotate its
X.509 certificates without the need to modify its respective
authentication data at the authorization server.
Public Key The Public Key method uses public keys to identify
clients. As pre-requisite, the client registers a X.509
certificate or a trusted source for its X.509 certificates (jwks
uri as defined in [RFC7591]) with the authorization server.
During authentication, TLS is utilized to validate the client's
possession of the private key corresponding to the public key
presented in the respective TLS handshake. In contrast to the PKI
method, the certificate chain is not validated in this case. The
client is successfully authenticated, if the subject public key
info of the validated certificate matches the subject public key
info of one the certificates configured for that particular
client. The Public Key method allows to use mutual TLS to
authenticate clients without the need to maintain a PKI. When
used in conjunction with a trusted X.509 certificate source, it
also allows the client to rotate its X.509 certificates without
the need to change its respective authentication data at the
authorization server.
2.2. Authorization Server Metadata 2.2. Authorization Server Metadata
"tls_client_auth" is used as a new value of the In authorization server metadata, such as [OpenID.Discovery] and
"token_endpoint_auth_methods_supported" metadata parameter to [I-D.ietf-oauth-discovery], the
indicate server support for mutual TLS as a client authentication "token_endpoint_auth_methods_supported" parameter indicates client
method in authorization server metadata such as [OpenID.Discovery] authentication methods to the token endpoint supported by the
and [I-D.ietf-oauth-discovery]. authorization server. This document introduces the value
"tls_client_auth" for use in "token_endpoint_auth_methods_supported"
to indicate server support for mutual TLS client authentication
utilizing the PKI method. And for the support of mutual TLS client
authentication utilizing the Public Key method, the value
"pub_key_tls_client_auth" is used in
"token_endpoint_auth_methods_supported".
This document also introduces a new authorization server metadata
parameter:
mutual_tls_sender_constrained_access_tokens
OPTIONAL. Boolean value indicating server support for mutual TLS
sender constrained access tokens. If omitted, the default value
is "false".
2.3. Dynamic Client Registration 2.3. Dynamic Client Registration
This draft adds the following values and metadata parameters to OAuth This document adds the following values and metadata parameters to
2.0 Dynamic Client Registration [RFC7591]. OAuth 2.0 Dynamic Client Registration [RFC7591].
The value "tls_client_auth" is used to indicate the client's The client metadata parameter
intention to use mutual TLS as an authentication method to the token "mutual_tls_sender_constrained_access_tokens" is a Boolean value used
endpoint for the "token_endpoint_auth_method" client metadata field. to indicate the client's intention to use mutual TLS sender
constrained access tokens. If omitted, the default value is "false".
For authorization servers that associate certificates with clients For the PKI method of binding a certificate to a client, the value
using subject information in the certificate, the following two new "tls_client_auth" is used to indicate the client's intention to use
metadata parameters can be used: mutual TLS as an authentication method to the token endpoint for the
"token_endpoint_auth_method" client metadata parameter. And the
following two metadata parameters are introduced in support of the
PKI method of binding a certificate to a 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 the OAuth client will use in distinguished name of the certificate the OAuth client will use in
mutual TLS authentication. mutual TLS authentication.
tls_client_auth_root_dn tls_client_auth_root_dn
An [RFC4514] string representation of a distinguished name that OPTIONAL. An [RFC4514] string representation of a distinguished
can optionally be used to constrain, for the given client, the name that can optionally be used to constrain, for the given
expected distinguished name of the root issuer of the client client, the expected distinguished name of the root issuer of the
certificate. client certificate.
For authorization servers that use the key or full certificate to With the Public Key method of binding a certificate to a client, the
associate clients with certificates, the existing "jwks_uri" or value "pub_key_tls_client_auth" is used for the
"jwks" metadata parameters from [RFC7591] should be used. "token_endpoint_auth_method" client metadata parameter to indicate
the client's intention to use mutual TLS with a self-signed
certificate as an authentication method. For the Public Key method,
the existing "jwks_uri" or "jwks" metadata parameters from [RFC7591]
are used to convey client's public keys, where the X.509 certificates
are represented using the "x5c" parameter from [RFC7517].
3. Mutual TLS Sender Constrained Resources Access 3. Mutual TLS Sender Constrained Resources Access
When mutual TLS is used at the token endpoint, the authorization When mutual TLS is used at the token endpoint, the authorization
server is able to bind the issued access token to the client server is able to bind the issued access token to the client
certificate. Such a binding is accomplished by associating the certificate. Such a binding is accomplished by associating the
certificate with the token in a way that can be accessed by the certificate with the token in a way that can be accessed by the
protected resource, such as embedding the certificate hash in the protected resource, such as embedding the certificate hash in the
issued access token directly, using the syntax described in issued access token directly, using the syntax described in
Section 3.1, or through token introspection as described in Section 3.1, or through token introspection as described in
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specification. specification.
The client makes protected resource requests as described in The client makes protected resource requests as described in
[RFC6750], however, those requests MUST be made over a mutually [RFC6750], however, those requests MUST be made over a mutually
authenticated TLS connection using the same certificate that was used authenticated TLS connection using the same certificate that was used
for mutual TLS at the token endpoint. for mutual TLS at the token endpoint.
The protected resource MUST obtain the client certificate used for The protected resource MUST obtain the client certificate used for
mutual TLS authentication and MUST verify that the certificate mutual TLS authentication and MUST verify that the certificate
matches the certificate associated with the access token. If they do matches the certificate associated with the access token. If they do
not match, the resource access attempt MUST be rejected with an not match, the resource access attempt MUST be rejected with an error
error. per [RFC6750] using an HTTP 401 status code and the "invalid_token"
error code.
3.1. X.509 Certificate SHA-256 Thumbprint Confirmation Method for JWT 3.1. X.509 Certificate SHA-256 Thumbprint Confirmation Method for JWT
When access tokens are represented as a JSON Web Tokens When access tokens are represented as a JSON Web Tokens
(JWT)[RFC7519], the certificate hash information SHOULD be (JWT)[RFC7519], the certificate hash information SHOULD be
represented using the "x5t#S256" confirmation method member defined represented using the "x5t#S256" confirmation method member defined
herein. 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
defines the new JWT Confirmation Method RFC 7800 [RFC7800] member defines the new JWT Confirmation Method RFC 7800 [RFC7800] member
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"sub": "ty.webb@example.com", "sub": "ty.webb@example.com",
"exp": 1493726400, "exp": 1493726400,
"nbf": 1493722800, "nbf": 1493722800,
"cnf":{ "cnf":{
"x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2" "x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2"
} }
} }
Figure 1: Example claims of a Certificate Thumbprint Constrained JWT Figure 1: Example claims of a Certificate Thumbprint Constrained JWT
If, in the future, certificate thumbprints need to be computed using
hash functions other than SHA-256, it is suggested that additional
related JWT confirmation methods members be defined for that purpose.
For example, a new "x5t#S512" (X.509 Certificate Thumbprint using
SHA-512) confirmation method member could be defined by registering
it in the the IANA "JWT Confirmation Methods" registry
[IANA.JWT.Claims] for JWT "cnf" member values established by
[RFC7800].
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 sender constrained access token, the hash of the For a mutual TLS sender constrained access token, the hash of the
certificate to which the token is bound is conveyed to the protected certificate to which the token is bound is conveyed to the protected
resource as meta-information in a token introspection response. The resource as meta-information in a token introspection response. The
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"exp": 1493726400, "exp": 1493726400,
"nbf": 1493722800, "nbf": 1493722800,
"cnf":{ "cnf":{
"x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2" "x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2"
} }
} }
Figure 2: Example Introspection Response for a Certificate Figure 2: Example Introspection Response for a Certificate
Constrained Access Token Constrained Access Token
4. IANA Considerations 4. Implementation Considerations
4.1. JWT Confirmation Methods Registration 4.1. Authorization Server
The authorization server needs to setup its TLS configuration
appropriately for the binding methods it supports.
If the authorization server wants to support mutual TLS client
authentication and other client authentication methods in parallel,
it should make mutual TLS optional on the token endpoint.
If the authorization server supports the Public Key method, it should
configure the TLS stack in a way that it does not verify whether the
certificate presented by the client during the handshake is signed by
a trusted CA certificate.
Please note: the Public Key method is intended to support client
authentication using self-signed certificates.
The authorization server may also consider hosting the token endpoint
on a separate host name in order to prevent unintended impact on the
TLS behavior of its other endpoints, e.g. authorization or
registration.
4.2. Resource Server
From the perspective of the resource server, TLS client
authentication is used as a proof of possession method only. For the
purpose of client authentication, the resource server may completely
rely on the authorization server. So there is no need to validate
the trust chain of the client's certificate in any of the methods
defined in this document. The resource server should therefore
configure the TLS stack in a way that it does not verify whether the
certificate presented by the client during the handshake is signed by
a trusted CA certificate.
4.3. Sender Constrained Access Tokens Without Client Authentication
This document allows for the use of client authentication only or
client authentication in combination with sender constraint access
tokens. Use of mutual TLS sender constrained access tokens without
client authentication (e.g. to support binding access tokens to a TLS
client certificate for public clients) is also possible. The
authorization server would configure the TLS stack in the same manor
as for the Public Key method such that it does not verify that the
certificate presented by the client during the handshake is signed by
a trusted CA. Individual instances of a public client would then
create a self-signed certificate for mutual TLS with the
authorization server and resource server. The authorization server
would not authenticate the client at the OAuth layer but would bind
issued access tokens to the certificate, which the client has proven
possession of the corresponding private key. The access token is
then mutual TLS sender constrained and can only be used by the client
possessing the certificate and private key and utilizing them to
negotiate mutual TLS on connections to the resource server.
4.4. Certificate Bound Access Tokens
As described in Section 3, an access token is bound to a specific
client certificate, which means that the same certificate must be
used for mutual TLS on protected resource access. It also implies
that access tokens are invalidated when a client updates the
certificate, which can be handled similar to expired access tokens
where the client requests a new access token (typically with a
refresh token) and retries the protected resource request.
5. IANA Considerations
5.1. JWT Confirmation Methods Registration
This specification requests registration of the following value in This specification requests registration of the following value in
the IANA "JWT Confirmation Methods" registry [IANA.JWT.Claims] for the IANA "JWT Confirmation Methods" registry [IANA.JWT.Claims] for
JWT "cnf" member values established by [RFC7800]. JWT "cnf" member values established by [RFC7800].
4.1.1. Registry Contents 5.1.1. Registry Contents
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 ]]
4.2. Token Endpoint Authentication Method Registration 5.2. OAuth Authorization Server Metadata Registration
This specification requests registration of the following value in
the IANA "OAuth Authorization Server Metadata" registry
[IANA.OAuth.Parameters] established by [I-D.ietf-oauth-discovery].
5.2.1. Registry Contents
o Metadata Name: "mutual_tls_sender_constrained_access_tokens"
o Metadata Description: Indicates server support for mutual TLS
sender constraint access tokens.
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [[ this specification ]]
5.3. Token Endpoint Authentication Method Registration
This specification requests registration of the following value in This specification requests registration of the following value 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].
4.2.1. Registry Contents 5.3.1. Registry Contents
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 2.2 of [[ this specification ]] o Specification Document(s): Section 2.2 of [[ this specification ]]
4.3. OAuth Token Introspection Response Registration o Token Endpoint Authentication Method Name:
"pub_key_tls_client_auth"
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [[ this specification ]]
5.4. OAuth Token Introspection Response Registration
This specification requests registration of the following value in This specification requests registration of the following value in
the IANA "OAuth Token Introspection Response" registry the IANA "OAuth Token Introspection Response" registry
[IANA.OAuth.Parameters] established by [RFC7662]. [IANA.OAuth.Parameters] established by [RFC7662].
4.3.1. Registry Contents 5.4.1. Registry Contents
o Claim Name: "cnf" o Claim Name: "cnf"
o Claim Description: Confirmation o Claim Description: Confirmation
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 3.2 of [[ this specification ]] o Specification Document(s): Section 3.2 of [[ this specification ]]
4.4. OAuth Dynamic Client Registration Metadata Registration 5.5. OAuth 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]:
4.4.1. Registry Contents 5.5.1. Registry Contents
o Client Metadata Name:
"mutual_tls_sender_constrained_access_tokens"
o Client Metadata Description: Indicates the client's intention to
use mutual TLS sender constraint access tokens.
o Change Controller: IESG
o Specification Document(s): Section 2.3 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 distinguished name of the client certificate. subject distinguished name of the client certificate.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 2.3 of [[ this specification ]] o Specification Document(s): Section 2.3 of [[ this specification ]]
o Client Metadata Name: "tls_client_auth_root_dn" o Client Metadata Name: "tls_client_auth_root_dn"
o Client Metadata Description: String value specifying the expected o Client Metadata Description: String value specifying the expected
distinguished name of the root issuer of the client certificate distinguished name of the root issuer of the client certificate
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): Section 2.3 of [[ this specification ]] o Specification Document(s): Section 2.3 of [[ this specification ]]
5. Security Considerations 6. Security Considerations
5.1. TLS Versions and Best Practices 6.1. TLS Versions and Best Practices
TLS 1.2 [RFC5246] is cited in this document because, at the time of TLS 1.2 [RFC5246] is cited in this document because, at the time of
writing, it is latest version that is widely deployed. However, this writing, it is latest version that is widely deployed. However, this
document is applicable with other TLS versions supporting document is applicable with other TLS versions supporting
certificate-based client authentication. Implementation security certificate-based client authentication. Implementation security
considerations for TLS, including version recommendations, can be considerations for TLS, including version recommendations, can be
found in Recommendations for Secure Use of Transport Layer Security found in Recommendations for Secure Use of Transport Layer Security
(TLS) and Datagram Transport Layer Security (DTLS) [BCP195]. (TLS) and Datagram Transport Layer Security (DTLS) [BCP195].
5.2. Client Identity Binding by the Authorization Server 6.2. X.509 Certificate Spoofing
No specific method of binding a certificate to a client identifier at If the PKI method is used, an attacker could try to impersonate a
the token endpoint is prescribed by this document. However, some client using a certificate for the same DN issued by another CA,
method MUST be employed so that, in addition to proving possession of which the authorization server trusts.
the private key corresponding to the certificate, the client identity
is also bound to the certificate. One such binding would be to
configure for the client a value that the certificate must contain in
the subject field and possibly the expected trust anchor. An
alternative method would be to configure a public key for the client
directly that would have to match the subject public key info of the
certificate.
6. References There are two ways to cope with that threat: the authorization server
may decide to only accept a limited number of CAs whose certificate
issuance policy meets its security requirements. Alternatively or in
addition, the client may want to explicitly prescribe the CA it will
use for obtaining its certificates. The latter is supported by this
document with the client registration parameter
"tls_client_auth_root_dn".
6.1. Normative References 7. References
7.1. Normative References
[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre, [BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/bcp195>. 2015, <http://www.rfc-editor.org/info/bcp195>.
[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,
skipping to change at page 10, line 24 skipping to change at page 14, line 15
[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,
<http://www.rfc-editor.org/info/rfc7800>. <http://www.rfc-editor.org/info/rfc7800>.
[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>.
6.2. Informative References 7.2. Informative References
[I-D.ietf-oauth-discovery] [I-D.ietf-oauth-discovery]
Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0 Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", draft-ietf-oauth- Authorization Server Metadata", draft-ietf-oauth-
discovery-04 (work in progress), August 2016. discovery-04 (work in progress), August 2016.
[IANA.JWT.Claims] [IANA.JWT.Claims]
IANA, "JSON Web Token Claims", IANA, "JSON Web Token Claims",
<http://www.iana.org/assignments/jwt>. <http://www.iana.org/assignments/jwt>.
[IANA.OAuth.Parameters] [IANA.OAuth.Parameters]
IANA, "OAuth Parameters", IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>. <http://www.iana.org/assignments/oauth-parameters>.
[OpenID.Discovery] [OpenID.Discovery]
Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID
Connect Discovery 1.0", February 2014. Connect Discovery 1.0", February 2014.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://www.rfc-editor.org/info/rfc7519>. <http://www.rfc-editor.org/info/rfc7519>.
[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and [RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol", P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015, RFC 7591, DOI 10.17487/RFC7591, July 2015,
<http://www.rfc-editor.org/info/rfc7591>. <http://www.rfc-editor.org/info/rfc7591>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection", [RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
skipping to change at page 11, line 26 skipping to change at page 15, line 22
Additionally, the authors would like to thank the following people Additionally, the authors would like to thank the following people
for their input and contributions to the specification: Sergey for their input and contributions to the specification: Sergey
Beryozkin, Vladimir Dzhuvinov, Samuel Erdtman, Phil Hunt, Sean Beryozkin, Vladimir Dzhuvinov, Samuel Erdtman, Phil Hunt, Sean
Leonard, Kepeng Li, James Manger, Jim Manico, Nov Matake, Sascha Leonard, Kepeng Li, James Manger, Jim Manico, Nov Matake, Sascha
Preibisch, Justin Richer, Dave Tonge, and Hannes Tschofenig. Preibisch, Justin Richer, Dave Tonge, and Hannes Tschofenig.
Appendix B. Document(s) History Appendix B. 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-03
o Introduced metadata and client registration parameter to publish
and request support for mutual TLS sender constrained access
tokens
o Added description of two methods of binding the cert and client,
PKI and Public Key.
o Indicated that the "tls_client_auth" authentication method is for
the PKI method and introduced "pub_key_tls_client_auth" for the
Public Key method
o Added implementation considerations, mainly regarding TLS stack
configuration and trust chain validation, as well as how to to do
binding of access tokens to a TLS client certificate for public
clients, and considerations around certificate bound access tokens
o Added new section to security considerations on cert spoofing
o Add text suggesting that a new cnf member be defined in the
future, if hash function(s) other than SHA-256 need to be used for
certificate thumbprints
draft-ietf-oauth-mtls-02 draft-ietf-oauth-mtls-02
o Fixed editorial issue https://mailarchive.ietf.org/arch/msg/oauth/ o Fixed editorial issue https://mailarchive.ietf.org/arch/msg/oauth/
U46UMEh8XIOQnvXY9pHFq1MKPns U46UMEh8XIOQnvXY9pHFq1MKPns
o Changed the title (hopefully "Mutual TLS Profile for OAuth 2.0" is o Changed the title (hopefully "Mutual TLS Profile for OAuth 2.0" is
better than "Mutual TLS Profiles for OAuth Clients"). better than "Mutual TLS Profiles for OAuth Clients").
draft-ietf-oauth-mtls-01 draft-ietf-oauth-mtls-01
o Added more explicit details of using RFC 7662 token introspection o Added more explicit details of using RFC 7662 token introspection
skipping to change at page 12, line 5 skipping to change at page 16, line 21
o Changed the text in the Section 3 to not be specific about using a o Changed the text in the Section 3 to not be specific about using a
hash of the cert. hash of the cert.
o Changed the abbreviated title to 'OAuth Mutual TLS' (previously o Changed the abbreviated title to 'OAuth Mutual TLS' (previously
was the acronym MTLSPOC). was the acronym MTLSPOC).
draft-ietf-oauth-mtls-00 draft-ietf-oauth-mtls-00
o Created the initial working group version from draft-campbell- o Created the initial working group version from draft-campbell-
oauth-mtls oauth-mtls
draft-campbell-oauth-mtls-01
o Fix some typos. o Fix some typos.
o Add to the acknowledgements list. o Add to the acknowledgements list.
draft-campbell-oauth-mtls-00 draft-campbell-oauth-mtls-00
o Add a Mutual TLS sender constrained protected resource access o Add a Mutual TLS sender constrained protected resource access
method and a x5t#S256 cnf method for JWT access tokens (concepts method and a x5t#S256 cnf method for JWT access tokens (concepts
taken in part from draft-sakimura-oauth-jpop-04). taken in part from draft-sakimura-oauth-jpop-04).
o Fixed "token_endpoint_auth_methods_supported" to o Fixed "token_endpoint_auth_methods_supported" to
"token_endpoint_auth_method" for client metadata. "token_endpoint_auth_method" for client metadata.
skipping to change at page 12, line 34 skipping to change at page 17, line 4
draft-campbell-oauth-tls-client-auth-00 draft-campbell-oauth-tls-client-auth-00
o Initial draft. o Initial draft.
Authors' Addresses Authors' Addresses
Brian Campbell Brian Campbell
Ping Identity Ping Identity
Email: brian.d.campbell@gmail.com Email: brian.d.campbell@gmail.com
John Bradley John Bradley
Ping Identity Yubico
Email: ve7jtb@ve7jtb.com Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/ URI: http://www.thread-safe.com/
Nat Sakimura Nat Sakimura
Nomura Research Institute Nomura Research Institute
Email: n-sakimura@nri.co.jp Email: n-sakimura@nri.co.jp
URI: https://nat.sakimura.org/ URI: https://nat.sakimura.org/
Torsten Lodderstedt Torsten Lodderstedt
YES Europe AG YES Europe AG
Email: torsten@lodderstedt.net Email: torsten@lodderstedt.net
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