Re: [Gen-art] [OAUTH-WG] Gen-ART review of draft-ietf-oauth-v2-bearer-15.txt

Stephen Farrell <stephen.farrell@cs.tcd.ie> Fri, 03 February 2012 13:17 UTC

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Date: Fri, 03 Feb 2012 13:17:41 +0000
From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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To: Alexey Melnikov <alexey.melnikov@isode.com>
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Cc: Mike Jones <Michael.Jones@microsoft.com>, IETF-Discussion Discussion <ietf@ietf.org>, General Area Review Team <gen-art@ietf.org>, "draft-ietf-oauth-v2-bearer.all@tools.ietf.org" <draft-ietf-oauth-v2-bearer.all@tools.ietf.org>, "oauth@ietf.org" <oauth@ietf.org>
Subject: Re: [Gen-art] [OAUTH-WG] Gen-ART review of draft-ietf-oauth-v2-bearer-15.txt
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That looks fine to me fwiw,
Thanks,
S.

On 02/03/2012 01:14 PM, Alexey Melnikov wrote:
> On 31/01/2012 10:33, Alexey Melnikov wrote:
>> On 30/01/2012 05:20, Mike Jones wrote:
> [...]
>>> About your third minor issue on RFC 6125 versus RFC 2818, you'll find
>>> that, per the history entries, a previous reference to RFC 2818 was
>>> changed to RFC 6125 in draft 14 at the request of Security Area
>>> Director Stephen Farrell.
> I've quickly chatted with Stephen and he said that he only asked the
> question and didn't necessarily instructed the WG to do the change from
> RFC 2818 to RFC 6125. Keeping this in mind...
>>> If you'd like to see this reference reintroduced, I'd request that
>>> you work with Stephen on specific alternative proposed wording that
>>> is acceptable to both of you.
>> Ok, I can work with Stephen and Peter Saint-Andre (RFC 6125 co-author)
>> on some text.
>
> So, here are the proposed changes:
>
> 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.
>
> I suggest inserting "[RFC5280]" at the end of the last sentence above.
>
> 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].
>
> Please replace the last sentence quoted above with:
>
> Furthermore, when presenting the token to a resource server, the
> client MUST verify the identity of that resource server, as per
> section 3.1 of [RFC2818].
>
> [Expanded motivation for the change:
> I think the reference to RFC 6125 needs to be replaced with the
> reference to section 3.1 of RFC 2818. Firstly, the procedure described
> in RFC 6125 differs slightly from RFC 2818 (matching of IP addresses is
> allowed, wildcards can be used with partial hostnames (e.g. foo* is
> allowed, where RFC 6125 doesn't allow for that). Secondly, if RFC 6125
> is referenced, then the OAuth document needs to say whether
> SRV-ID/URI-IDs are allowed and whether wildcards are allowed.]
>
>