Last Call Review of draft-ietf-oauth-v2-bearer-
|Requested rev.||no specific revision (document currently at 23)|
|Type||Last Call Review|
|Team||General Area Review Team (Gen-ART) (genart)|
Genart Telechat review of - by Alexey Melnikov (diff)
Genart Last Call review of - by Alexey Melnikov (diff)
|Draft last updated||2012-01-29|
I am the assigned Gen-ART reviewer for this draft. For background on Gen-ART, please see the FAQ at < http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. Please resolve these comments along with any other Last Call comments you may receive. Document: draft-ietf-oauth-v2-bearer-15.txt Reviewer: Alexey Melnikov Review Date: 29 Jan 2012 IETF LC End Date: 7 Feb 2012 IESG Telechat date: (if known) - Summary: Mostly ready, with a couple of things that should be addressed. Major Issues: I have 2 issues in section 3: 3. The WWW-Authenticate Response Header Field If the protected resource request does not include authentication credentials or does not contain an access token that enables access to the protected resource, the resource server MUST include the HTTP "WWW-Authenticate" response header field; it MAY include it in response to other conditions as well. The "WWW-Authenticate" header field uses the framework defined by HTTP/1.1, Part 7 [I-D.ietf-httpbis-p7-auth] as follows: challenge = "Bearer" [ 1*SP 1#param ] param = realm / scope / error / error-desc / error-uri / auth-param scope = "scope" "=" quoted-string error = "error" "=" quoted-string error-desc = "error_description" "=" quoted-string error-uri = "error_uri" "=" quoted-string 1). I am agreeing with Julian about redefinition of ABNF from HTTPBis documents. I believe there is a proposal to fix that but the new draft hasn't been posted yet. 2). My 2nd major issue is about the following paragraph: The "scope" attribute is a space-delimited list of scope values indicating the required scope of the access token for accessing the requested resource. In some cases, the "scope" value will be used when requesting a new access token with sufficient scope of access to utilize the protected resource. The "scope" attribute MUST NOT appear more than once. The "scope" value is intended for programmatic use and is not meant to be displayed to end users. I don't think this provide enough information about what this is, how it is to be used and which values are allowed. As this is not meant to be displayed to end users, then you need to say what values are allowed and which entity can allocate them. Is there a registry for these tokens, e.g. an IANA registry? Minor Issues: 1). 2.2. Form-Encoded Body Parameter When sending the access token in the HTTP request entity-body, the client adds the access token to the request body using the "access_token" parameter. The client MUST NOT use this method unless all of the following conditions are met: o The HTTP request entity-body is single-part. o The entity-body follows the encoding requirements of the "application/x-www-form-urlencoded" content-type as defined by HTML 4.01 [W3C.REC-html401-19991224]. o The HTTP request entity-header includes the "Content-Type" header field set to "application/x-www-form-urlencoded". I would combine the first and the third bullet into a single statement, because they seem to be a bit confusing while being read separately. (I.e., is it possible to have Content-Type of "application/x-www-form-urlencoded" with something which is multipart?) 2). Section "3.1. Error Codes" I recommend creating an IANA registry for these or explain why one is not needed. 3). 4.2. Threat Mitigation To protect against token disclosure, confidentiality protection MUST be applied using TLS [RFC5246] with a ciphersuite that provides confidentiality and integrity protection. This requires that the communication interaction between the client and the authorization server, as well as the interaction between the client and the resource server, utilize confidentiality and integrity protection. Since TLS is mandatory to implement and to use with this specification, it is the preferred approach for preventing token disclosure via the communication channel. For those cases where the client is prevented from observing the contents of the token, token encryption MUST be applied in addition to the usage of TLS protection. As a further defense against token disclosure, the client MUST validate the TLS certificate chain when making requests to protected resources. and To deal with token capture and replay, the following recommendations are made: First, the lifetime of the token MUST be limited; one means of achieving this is by putting a validity time field inside the protected part of the token. Note that using short-lived (one hour or less) tokens reduces the impact of them being leaked. Second, confidentiality protection of the exchanges between the client and the authorization server and between the client and the resource server MUST be applied. As a consequence, no eavesdropper along the communication path is able to observe the token exchange. Consequently, such an on-path adversary cannot replay the token. Furthermore, when presenting the token to a resource server, the client MUST verify the identity of that resource server, as per Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS) [RFC6125]. Firstly, I would move the RFC 6125 reference to the first paragraph quoted above (but see below). Secondly, you should either normatively reference RFC 2818 (HTTP over TLS) instead of RFC 6125, or you need to provide more information about how RFC 6125 is to be used, because it has several options which need to be described (use of SRV-IDs, URI-IDs, DNS-IDs, use of wildcards). I suspect you should just reference RFC 2818. Nits: 2.2. Form-Encoded Body Parameter o The content to be encoded in the entity-body MUST consist entirely of ASCII characters. ASCII needs a reference. ID-nits reports: == The document seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords -- however, there's a paragraph with a matching beginning. Boilerplate error? (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). and: Found 'MUST not' in this paragraph: o Stated that bearer tokens MUST not be stored in cookies that can be sent in the clear in the Threat Mitigation section.