ACE Working Group L. Seitz
Internet-Draft RISE SICS
Intended status: Informational S. Erdtman
Expires: February 17, 2018 Spotify AB
August 16, 2017
Raw-Public-Key and Pre-Shared-Key as OAuth client credentials
draft-erdtman-ace-rpcc-01
Abstract
This document describes Transport Layer Security (TLS) authentication
using Raw-Public-Key and Pre-Shared-Key as new mechanisms for OAuth
client authentication. Although defined for TLS the mechanisms are
equally applicable for DTLS.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Pre-Shared-Key for Client Authentication . . . . . . . . . . 2
3. Raw-Public-Key for Client Authentication . . . . . . . . . . 3
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5.1. Token Endpoint Authentication Method Registration . . . . 4
5.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 4
5.1.2. Registry Contents . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
This document describes Transport Layer Security (TLS) authentication
using Raw-Public-Key and Pre-Shared-Key as the mechanism for OAuth
client authentication. Examples of endpoint requiering client
authentication are token and introspection.
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 two additional mechanisms of client
authentication utilizing Raw-Public-Key [RFC7250] and Pre-Shared-Key
TLS [RFC4279], which provide better security characteristics than
shared secrets.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Pre-Shared-Key for Client Authentication
The following section defines, as an extension of OAuth 2.0,
Section 2.3 [RFC6749], using Pre-Shared-Key with TLS [RFC4279] to
authenticate the client. This method is registered as
'tls_client_psk' in "OAuth Token Endpoint Authentication Methods"
registry.
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The (D)TLS handshake MUST be done according to [RFC4279], with the
client indicating support for one or more Pre-Shared-Key cipher
suites and authorization server selecting a Pre-Shared-Key cipher
suite. In order to enable authorization server to select the correct
pre-shared-key the client MUST send its client identifier in the psk-
identity field of the ClientKeyExchange message. How the
authorization server maps a client identifier to the pre-shared-key
is out of scope for this specification.
Note that the client identity MUST be 2^16 bytes or shorter, in order
to fit into the psk-identity field.
3. Raw-Public-Key for Client Authentication
The following section defines, as an extension of OAuth 2.0,
Section 2.3 [RFC6749], the use of Raw-Public-Key with (D)TLS
[RFC7250] to authenticate the client. This method is registered
as'tls_client_rpk' in "OAuth Token Endpoint Authentication Methods"
registry.
The (D)TLS handshake MUST be done according to [RFC7250], with the
client indicating support for Raw-Public-Key certificates and the
authorization server asking client send its Raw Public Key
certificate. Since the client cannot send an explicit client
identifier in the handshake, the authorization server MUST the derive
a client identifier from RPK that the client uses.
Authorization servers MAY use the following method to map a Raw
Public Key to a client identifier: The client identifier is generated
from the Raw Public Key using the procedure specified in section 3 of
[RFC6920]. The digest is calculated on the Raw Public Key only (not
on the SubjectPublicKeyInfo used in the handshake). An example is
shown in Figure 1.
Raw Public Key (Base64 encoded):
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEEtboxNKPgxEKV9JTNzy
tUvAbxEfkCTVB9kOzheF5wRAoOz2NKP+ln+XLVAQSp1D6jfo09tppvN
poQA1nnBNH6A==";
Encoding:
ni:///sha-256;xzLa24yOBeCkos3VFzD2gd83Urohr9TsXqY9nhdDN0
Figure 1: Example encoding of a raw public key in the Named
Information URI Format
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4. Acknowledgements
This document is highly inspired by [I-D.ietf-oauth-mtls] written by
B. Campbell, J. Bradley, N. Sakimura and T. Lodderstedt.
5. IANA Considerations
5.1. Token Endpoint Authentication Method Registration
This specification requests registration of the following value in
the IANA "OAuth Token Endpoint Authentication Methods" registry
[IANA.OAuth.Parameters] established by [RFC7591].
5.1.1. Registry Contents
o Token Endpoint Authentication Method Name: "tls_client_rpk"
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
5.1.2. Registry Contents
o Token Endpoint Authentication Method Name: "tls_client_psk"
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
6. Security Considerations
TBD
7. References
7.1. Normative References
[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>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>.
[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>.
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[RFC6920] Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
Keranen, A., and P. Hallam-Baker, "Naming Things with
Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,
<http://www.rfc-editor.org/info/rfc6920>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[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>.
7.2. Informative References
[I-D.ietf-oauth-mtls]
Campbell, B., Bradley, J., Sakimura, N., and T.
Lodderstedt, "Mutual TLS Profile for OAuth 2.0", draft-
ietf-oauth-mtls-03 (work in progress), July 2017.
[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.
Authors' Addresses
Ludwig Seitz
RISE SICS
Scheelevaegen 17
Lund 223 70
SWEDEN
Email: ludwig.seitz@ri.se
Samuel Erdtman
Spotify AB
Birger Jarlsgatan 61, 4tr
Stockholm 113 56
Sweden
Email: erdtman@spotify.com
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