Internet DRAFT - draft-campbell-oauth-tls-client-auth
draft-campbell-oauth-tls-client-auth
OAuth Working Group B. Campbell
Internet-Draft J. Bradley
Intended status: Standards Track Ping Identity
Expires: April 13, 2017 October 10, 2016
Mutual X.509 Transport Layer Security (TLS) Authentication for OAuth
Clients
draft-campbell-oauth-tls-client-auth-00
Abstract
This document describes X.509 certificates as OAuth client
credentials using Transport Layer Security (TLS) mutual
authentication as a mechanism for client authentication to the
authorization server's token endpoint.
Status of This Memo
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This Internet-Draft will expire on April 13, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Notation and Conventions . . . . . . . . . . 2
2. Mutual TLS for Client Authentication . . . . . . . . . . . . 2
3. Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4.1. Token Endpoint Authentication Method Registration . . . . 3
4.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5.1. TLS Versions and Best Practices . . . . . . . . . . . . . 3
5.2. Client Identity Binding . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
Appendix B. Document History . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The OAuth 2.0 Authorization Framework [RFC6749] defines a shared
secret method of client authentication but also allows for the
definition and use of additional client authentication mechanisms
when interacting with the authorization server's token endpoint.
This document describes an additional mechanism of client
authentication utilizing mutual TLS [RFC5246] certificate-based
authentication.
1.1. Requirements Notation and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].
2. Mutual TLS for Client Authentication
The following section defines, as an extension of OAuth 2.0,
Section 2.3 [RFC6749], the use of mutual TLS as client credentials.
OAuth 2.0 requires that access token requests by the client to the
token endpoint use TLS. In order to utilize TLS for client
authentication, the TLS connection MUST have been established or
reestablished with mutual X.509 certificate authentication (i.e. the
Client Certificate and Certificate Verify messages are sent during
the TLS Handshake [RFC5246]).
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For all access token requests to the token endpoint, regardless of
the grant type used, the client MUST include the "client_id"
parameter, described in OAuth 2.0, Section 2.2 [RFC6749]. The
presence of the "client_id" parameter enables the authorization
server to easily identify the client independently from the content
of the certificate and allows for trust models to vary as appropriate
for a given deployment. The authorization server can locate the
client configuration by the client identifier and check the
certificate presented in the TLS Handshake against the expected
credentials for that client.
3. Metadata
The value "tls_client_auth" is used to indicate mutual TLS as an
authentication method to the token endpoint for the
"token_endpoint_auth_methods_supported" client metadata field defined
in [RFC7591], Section 2.
The same "tls_client_auth" value can also indicate server support for
mutual TLS as a client authentication method in authorization server
metadata such as [OpenID.Discovery] and [I-D.ietf-oauth-discovery].
4. IANA Considerations
4.1. Token Endpoint Authentication Method Registration
This specification requests registration of the following value in
the IANA "OAuth Token Endpoint Authentication Methods" registry
[IANA.OAuthTEAuthnMeths] established by [RFC7591].
4.1.1. Registry Contents
o Token Endpoint Authentication Method Name: "tls_client_auth"
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
5. Security Considerations
5.1. TLS Versions and Best Practices
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
document is applicable with other TLS versions supporting
certificate-based client authentication. Implementation security
considerations for TLS, including version recommendations, can be
found in Recommendations for Secure Use of Transport Layer Security
(TLS) and Datagram Transport Layer Security (DTLS) [BCP195].
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5.2. Client Identity Binding
No specifc method of binding a certificate to a client identifier is
prescribed by this document. However, some method should employed so
that, in addition to proving possession of 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
or the subjectAltName extension and possibly a restricted set of
trust anchors. 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
6.1. Normative References
[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/bcp195>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
6.2. Informative References
[I-D.ietf-oauth-discovery]
Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", draft-ietf-oauth-
discovery-04 (work in progress), August 2016.
[IANA.OAuthTEAuthnMeths]
IANA, "OAuth Token Endpoint Authentication Methods",
<http://www.iana.org/assignments/oauth-parameters/
oauth-parameters.xhtml#token-endpoint-auth-method>.
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[OpenID.Discovery]
Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID
Connect Discovery 1.0", February 2014.
[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,
<http://www.rfc-editor.org/info/rfc7591>.
Appendix A. Acknowledgements
Scott "not Tomlinson" Tomilson and Matt Peterson were involved in the
original design and implementation work that informed the content of
this document.
Appendix B. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-00
o Initial draft.
Authors' Addresses
Brian Campbell
Ping Identity
Email: brian.d.campbell@gmail.com
John Bradley
Ping Identity
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/
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