Re: [OAUTH-WG] Call for Adoption: OAuth 2.0 Mix-Up Mitigation

Nat Sakimura <sakimura@gmail.com> Wed, 27 January 2016 01:58 UTC

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From: Nat Sakimura <sakimura@gmail.com>
Date: Wed, 27 Jan 2016 01:58:08 +0000
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To: John Bradley <ve7jtb@ve7jtb.com>, "Phil Hunt (IDM)" <phil.hunt@oracle.com>
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Subject: Re: [OAUTH-WG] Call for Adoption: OAuth 2.0 Mix-Up Mitigation
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John,

Nov is not talking about the redirection endpoint. I just noticed that
3.1.2.1 of RFC 6749 is just asking TLS by "SHOULD" and I think it needs to
be changed to "MUST" but that is not what he is talking about.

Instead, he is talking about before starting the RFC 6749 flow.

In many cases, a non TLS protected sites have "Login with HIdP" button
linked to a URI that initiates the RFC 6749 flow. This portion is not
within  RFC 6749 and this endpoint has no name or no requirement to be TLS
protected. Right, it is very stupid, but there are many sites like that.
As a result, the attacker can insert itself as a proxy, say by providing a
free wifi hotspot, and either re-write the button or the request so that
the RP receives "Login with AIdP" instead of "Login with HIdP".

I have add a note explaining this to
http://nat.sakimura.org/2016/01/15/idp-mix-up-attack-on-oauth-rfc6749/

I also have added a bit of risk analysis on it and considered other risk
control measures as well.

It does not seem to be worthwhile to introduce a new wire-protocol element
to deal with this particular attack. (I regard code cut-and-paste attack a
separate attack.) I am inclining to think that just to TLS protect the
pre-RFC6749 flow portion and add a check to disallow the ASs that has
different authority section for the Auhtz EP and Token EP would be
adequate.

Nat

2016年1月27日(水) 2:18 John Bradley <ve7jtb@ve7jtb.com>om>:

> Nov,
>
> Are you referring to Sec 3.1.2.1 of RFC 6749.
>
> Stating that the the redirection endpoint SHOULD require TLS, and that the
> AS should warn the user if the redirect URI is not over TLS (Something I
> have never seen done in the real world)
>
> Not using TLS is reasonable when the redirect URI is using a custom scheme
> for native apps.
>
> It might almost be reasonable for the token flow where the JS page itself
> is not loaded over TLS so the callback to extract the fragment would not be
> as well.
> Note that the token itself is never passed over a non https connection in
> tis case.
> I would argue now that it is irresponsible to have a non TLS protected
> site, but not everyone is going to go along with that.
>
> Using a http scheme URI for the redirect is allowed but is really stupid.
>   We did have a large debate about this when profiling OAuth for Connect.
> We did tighten connect to say that if you are using the code flow then a
> http scheme redirect URI is only allowed if the client is confidential.
>
> John B.
>
> On Jan 26, 2016, at 1:14 AM, Phil Hunt (IDM) <phil.hunt@oracle.com> wrote:
>
> Still don't see it. Though i think the diagram is wrong (the rp should
> redirct to the ua and not call the authz direct), the IDP should either
> return an error or redirect the RP to TLS.
>
> I don't see this as proper oauth protocol since the RP is MITM the UA
> rather than acting as a client.
>
> Phil
>
> On Jan 25, 2016, at 19:57, nov matake <matake@gmail.com> wrote:
>
> In this flow, AuthZ endpoint is forced to be TLS-protected.
> http://nat.sakimura.org/wp-content/uploads/2016/01/oauth-idp-mixup.png
>
> However, RP’s redirect response which causes following AuthZ request is
> still not TLS-protected, and modified on the attacker’s proxy.
>
> Section 3.2 of this report also describes the same flow.
> http://arxiv.org/pdf/1601.01229v2.pdf
>
> On Jan 26, 2016, at 12:37, Phil Hunt (IDM) <phil.hunt@oracle.com> wrote:
>
> Also the authz endpoint is required to force tls. So if the client doesn't
> do it the authz should reject (eg by upgrading to tls).
>
> Phil
>
> On Jan 25, 2016, at 19:29, Phil Hunt (IDM) <phil.hunt@oracle.com> wrote:
>
> When the RP acting as the client issues a authorize redirect to the UA it
> has to make it with TLS
>
> Phil
>
> On Jan 25, 2016, at 17:53, Nov Matake <matake@gmail.com> wrote:
>
> It doen't say anything about the first request which initiate the login
> flow.
> It is still a reasonable assumption that RP puts a "login with FB" button
> on a non TLS-protected page.
>
> nov
>
> On Jan 26, 2016, at 10:45, Phil Hunt <phil.hunt@oracle.com> wrote:
>
> I would find it hard to believe that is true.
>
> From 6749 Sec 3.1
>
>    Since requests to the authorization endpoint result in user
>    authentication and the transmission of clear-text credentials (in the
>    HTTP response), the authorization server MUST require the use of TLS
>    as described in Section 1.6 <https://tools.ietf.org/html/rfc6749#section-1.6> when sending requests to the
>    authorization endpoint.
>
>
> Sec 3.1.2.1
>
>    The redirection endpoint SHOULD require the use of TLS as described
>    in Section 1.6 <https://tools.ietf.org/html/rfc6749#section-1.6> when the requested response type is "code" or "token",
>    or when the redirection request will result in the transmission of
>    sensitive credentials over an open network.  This specification does
>    not mandate the use of TLS because at the time of this writing,
>    requiring clients to deploy TLS is a significant hurdle for many
>    client developers.  If TLS is not available, the authorization server
>    SHOULD warn the resource owner about the insecure endpoint prior to
>    redirection (e.g., display a message during the authorization
>    request).
>
>    Lack of transport-layer security can have a severe impact on the
>    security of the client and the protected resources it is authorized
>    to access.  The use of transport-layer security is particularly
>    critical when the authorization process is used as a form of
>    delegated end-user authentication by the client (e.g., third-party
>    sign-in service).
>
>
> Section 10.5 talks about transmission of authorization codes in connection
> with redirects.
>
> Also see 6819, Sec 4.4.1.1 regarding eavesdropping or leaking of authz
> codes.
>
>
> Phil
>
> @independentid
> www.independentid.com
> phil.hunt@oracle.com
>
>
>
>
>
> On Jan 25, 2016, at 4:52 PM, nov matake <matake@gmail.com> wrote:
>
> The first assumption is coming from the original security report at
> http://arxiv.org/abs/1601.01229.
> RFC 6749 requires TLS between RS and AS, and also between UA and AS, but
> not between UA and RS.
>
> The blog post is based on my Japanese post, and it describes multi-AS case.
> Nat's another post describes the case which can affect single-AS case too.
>
> http://nat.sakimura.org/2016/01/22/code-phishing-attack-on-oauth-2-0-rfc6749/
>
> nov
>
> On Jan 26, 2016, at 08:22, Phil Hunt <phil.hunt@oracle.com> wrote:
>
> Sorry, meant to reply-all.
>
> Phil
>
> @independentid
> www.independentid.com
> phil.hunt@oracle.com
>
>
>
>
>
> Begin forwarded message:
>
> *From: *Phil Hunt <phil.hunt@oracle.com>
> *Subject: **Re: [OAUTH-WG] Call for Adoption: OAuth 2.0 Mix-Up Mitigation*
> *Date: *January 25, 2016 at 3:20:19 PM PST
> *To: *Nat Sakimura <sakimura@gmail.com>
>
> I am having trouble with the very first assumption. The user-agent sets up
> a non TLS protected connection to the RP? That’s a fundamental violation of
> 6749.
>
> Also, the second statement says the RP (assuming it acts as OAuth client)
> is talking to two IDPs.  That’s still a multi-AS case is it not?
>
> Phil
>
> @independentid
> www.independentid.com
> phil.hunt@oracle.com
>
>
>
>
>
> On Jan 25, 2016, at 2:58 PM, Nat Sakimura <sakimura@gmail.com> wrote:
>
> Hi Phil,
>
> Since I was not in Darmstadt, I really do not know what was discussed
> there, but with the compromised developer documentation described in
> http://nat.sakimura.org/2016/01/15/idp-mix-up-attack-on-oauth-rfc6749/,
> all RFC6749 clients with a naive implementer will be affected. The client
> does not need to be talking to multiple IdPs.
>
> Nat
>
> 2016年1月26日(火) 3:58 Phil Hunt (IDM) <phil.hunt@oracle.com>om>:
>
>> I recall making this point in Germany. 99% of existing use is fine. OIDC
>> is probably the largest community that *might* have an issue.
>>
>> I recall proposing a new security document that covers oauth security for
>> dynamic scenarios. "Dynamic" being broadly defined to mean:
>> * clients who have configured at runtime or install time (including
>> clients that do discovery)
>> * clients that communicate with more than one endpoint
>> * clients that are deployed in large volume and may update frequently
>> (more discussion of "public" cases)
>> * clients that are script based (loaded into browser on the fly)
>> * others?
>>
>> Phil
>>
>> > On Jan 25, 2016, at 10:39, George Fletcher <gffletch@aol.com> wrote:
>> >
>> > would
>>
>> _______________________________________________
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>> OAuth@ietf.org
>> https://www.ietf.org/mailman/listinfo/oauth
>>
>
>
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