Internet DRAFT - draft-erdtman-ace-rpcc
draft-erdtman-ace-rpcc
ACE Working Group L. Seitz
Internet-Draft RISE SICS
Intended status: Informational S. Erdtman
Expires: May 3, 2018 Spotify AB
October 30, 2017
Raw-Public-Key and Pre-Shared-Key as OAuth client credentials
draft-erdtman-ace-rpcc-02
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.
Status of This Memo
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This Internet-Draft will expire on May 3, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Pre-Shared-Key for Client Authentication . . . . . . . . . . 3
3. Raw-Public-Key for Client Authentication . . . . . . . . . . 3
4. Dynamic Registration . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6.1. OAuth Dynamic Client Registration Metadata Registration . 4
6.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 5
6.2. Token Endpoint Authentication Method Registration . . . . 5
6.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
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 requiring 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.
To get most bennefits and improved security with these new client
credential types it is recomended to use the 'one credential per
Client Software Instance' paradigm. This can be achived by letting
the client dynamicly register as described in [RFC7591].
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].
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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. If this method is to be used, the client and the
Authorization Server MUST share a secret key, and they MUST agree on
an identifier for this key.
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 the authorization server to select the
correct pre-shared-key the client MUST send the key identifier in the
psk-identity field of the ClientKeyExchange message. How the
authorization server maps the identifier to a pre-shared-key, and to
a specific client is out of scope for this specification.
Note that the key identifier 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 or key
identifier in the handshake, the authorization server MUST derive a
client identifier from RPK that the client uses.
Note to implementers: Authorization servers can 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.
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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
4. Dynamic Registration
For dynamic registration of a RPK this specification registers the
new parameter 'rpk' to the Client Registration Metadata Registry.
When used this parameter MUST contain a JSON Web Key representing the
public key of the client. When 'rpk' is present in the registration
request 'token_endpoint_auth_method' MUST include 'tls_client_rpk'.
For dynamic registration of a PSK this specification registers the
new parameter 'psk' to the Client Registration Metadata Registry.
When used this parameter MUST contain a JSON Web Key representing the
key of the client. When registering the client can include the key
in the registrations request or the authorisation can generate the
key and return it. If the 'psk' attribute is present in a request
'token_endpoint_auth_method' MUST include 'tls_client_psk'. To
request the authorisation server to generate the key the client
includes 'tls_client_psk' in 'token_endpoint_auth_method' but does
not send 'psk' attribute.
The 'jwks' and 'jwks_uri' is not used to avoid conflict and confusion
with application layer keys.
5. Acknowledgements
This document is highly inspired by [I-D.ietf-oauth-mtls] written by
B. Campbell, J. Bradley, N. Sakimura and T. Lodderstedt.
6. IANA Considerations
6.1. OAuth Dynamic Client Registration Metadata Registration
This specification requests registration of the following value in
the IANA "OAuth Dynamic Client Registration Metadata" registry
[IANA.OAuth.Parameters] established by [RFC7591].
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6.1.1. Registry Contents
o Client Metadata Name: "rpk"
o Client Metadata Description: JWK for client Raw-Public-Key, can be
included in request.
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
o Client Metadata Name: "psk"
o Client Metadata Description: JWK for client Pre-Shared-Key, can be
included both in request and response.
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
6.2. 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].
6.2.1. Registry Contents
o Token Endpoint Authentication Method Name: "tls_client_rpk"
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
o Token Endpoint Authentication Method Name: "tls_client_psk"
o Change Controller: IESG
o Specification Document(s): [[ this specification ]]
7. Security Considerations
TBD
8. References
8.1. 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,
<https://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>.
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[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.
[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,
<https://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>.
8.2. 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-04 (work in progress), October 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
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Samuel Erdtman
Spotify AB
Birger Jarlsgatan 61, 4tr
Stockholm 113 56
Sweden
Email: erdtman@spotify.com
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