There are two CSRF variations scenarios that I see. I can attack you and give my client access to your resources (original attack on the "resource").
I can attack you and give your client access to my resource (new attack on the "client"). Attack on the client vs. attack on the resource may be misleading here. Draft 20 only referred to attacks on the "resource" in its original CSRF description. Phil @independentid www.independentid.com phil.h...@oracle.com On 2011-08-13, at 7:30 AM, Eran Hammer-Lahav wrote: > All OAuth CSRF attacks are on the client. > > EHL > > From: Phil Hunt <phil.h...@oracle.com> > Date: Sat, 13 Aug 2011 00:21:50 -0700 > To: Torsten Lodderstedt <tors...@lodderstedt.net> > Cc: Eran Hammer-lahav <e...@hueniverse.com>, "OAuth WG (oauth@ietf.org)" > <oauth@ietf.org> > Subject: Re: [OAUTH-WG] Auth Code Swap Attack > >> +1 (to putting more detail in the Threat Model document) >> >> Yes, this is another CSRF attack (hence the change to 10.2). >> >> What is *new* is this is an attack on the client application rather than the >> resource server. As such, I agree this new attack vector is well deserving >> of wider review and discussion before finalizing the draft. >> >> Phil >> >> @independentid >> www.independentid.com >> phil.h...@oracle.com >> >> >> >> >> >> On 2011-08-12, at 11:58 PM, Torsten Lodderstedt wrote: >> >>> >>> >>> Am 12.08.2011 23:52, schrieb Eran Hammer-Lahav: >>>> >>>> This is really just a flavor of CSRF attacks. I have no objections to >>>> better documenting it (though I feel the current text is already >>>> sufficient), but we can't realistically expect to identify and close every >>>> possible browser-based attack. A new one is invented every other week. >>>> >>>> The problem with this text is that developers who do no understand CSRF >>>> attacks are not likely to implement it correctly with this >>>> information. Those who understand it do not need the extra verbiage which >>>> is more confusing than helpful. >>> >>> We are constantly facing the fact that a comprehensive description of >>> security threats needs more space than we have in the core draft. That's >>> the reason why the security document has 63 pages and that's also the >>> reason why we decided to let the core spec refer to this document for >>> in-depth explanations. This holds true for this threat as well. >>> >>> regards, >>> Torsten. >>> >>>> >>>> As for the new requirements, they are insufficient to actually accomplish >>>> what the authors propose without additional requirements on state local >>>> storage and verification to complete the flow. Also, the proposed text >>>> needs clarifications as noted below. >>>> >>>> >>>> From: Anthony Nadalin <tony...@microsoft.com> >>>> Date: Fri, 12 Aug 2011 12:06:36 -0700 >>>> To: "OAuth WG (oauth@ietf.org)" <oauth@ietf.org> >>>> Subject: [OAUTH-WG] Auth Code Swap Attack >>>> >>>> >>>> >>>> >>>>> Recommended Changes to draft-ietf-oauth-v2 >>>>> >>>>> In section 4, request options (e.g. 4.1.1) featuring "state" should >>>>> change from: >>>>> >>>>> state >>>>> OPTIONAL. An opaque value used by the client to maintain state between >>>>> the request and callback. The authorization server includes this value >>>>> when redirecting the user-agent back to the client. >>>>> >>>>> to: >>>>> >>>>> state >>>>> REQUIRED. An opaque value used by the client to maintain state between >>>>> the request and callback. The authorization server includes this value >>>>> when redirecting the user-agent back to the client. The encoded value >>>>> SHOULD enable the client application to determine the user-context that >>>>> was active at the time of the request (see section 10.12). The value >>>>> MUST NOT be guessable or predictable, and MUST be kept confidential. >>>>> >>>> >>>> >>>> Making the parameter required without making its usage required (I.e. >>>> "value SHOULD enable") accomplishes nothing. Also, what does "MUST >>>> be kept confidential" mean? Confidential from what? Why specify an >>>> "encoded value"? >>>> >>>> >>>>> Section 10.12 Cross-Site Request Forgery >>>>> >>>>> Change to: >>>>> >>>>> Cross-site request forgery (CSRF) is a web-based attack whereby HTTP >>>>> requests are transmitted from the user-agent of an end-user the server >>>>> trusts or has authenticated. CSRF attacks enable the attacker to intermix >>>>> the attacker's security context with that of the resource owner resulting >>>>> in a compromise of either the resource server or of the client >>>>> application itself. In the OAuth context, such attacks allow an attacker >>>>> to inject their own authorization code or access token into a client, >>>>> which can result in the client using an access token associated with the >>>>> attacker's account rather than the victim's. Depending on the nature of >>>>> the client and the protected resources, this can have undesirable and >>>>> damaging effects. >>>>> >>>>> In order to prevent such attacks, the client application MUST encode a >>>>> non-guessable, confidential end-user artifact and submit as the "state" >>>>> parameter to authorization and access token requests to the authorization >>>>> server. The client MUST keep the state value in a location accessible >>>>> only by the client or the user-agent (i.e., protected by same-origin >>>>> policy), for example, using a DOM variable, HTTP cookie, or HTML5 >>>>> client-side storage. >>>>> >>>>> The authorization server includes the value of the "state" parameter when >>>>> redirecting the user-agent back to the client. Upon receiving a redirect, >>>>> the client application MUST confirm that returned value of "state" >>>>> corresponds to the state value of the user-agent's user session. If the >>>>> end-user session represents an authenticated user-identity, the client >>>>> MUST ensure that the user-identity has NOT changed. >>>>> >>>> >>>> >>>> The above text uses 'user-context' and this 'user-identity'. Neither term >>>> is defined. >>>> >>>> EHL >>>> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.orghttps://www.ietf.org/mailman/listinfo/oauth >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org >>> https://www.ietf.org/mailman/listinfo/oauth >>
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