Re: [OAUTH-WG] Report an authentication issue

[Phil Hunt <[e-mail]>]

That sounds like the recent Twitter / thunderclap issue (thunderclap collected multiple twitter update tokens on a single server to allow simultaneous tweets to occur from huge numbers of twitter accounts).

If BobApp was previously approved as a client and the SP discovered BobApp was mis-behaving (witness the recent thunderclap twitter scenario), the SP can simply revoke to tokens issued to BobApp.

This just demonstrates why a server should never depend on parseable bearer tokens by themselves. SPs should check for token revocation.

Phil

@independentid
www.independentid.com
[e-mail]





On 2012-06-15, at 4:22 PM, Shuo Chen (MSR) wrote:

> The attack does not involve sniffing. It is about an app (let’s call it BobApp) running on victim Alice’s tablet, which is able to get the access token.
> Note that BobApp getting this access token on Alice’s device is NOT a security issue, but the natural consequence of the design of OAuth.
>  
> However, the real problem we concern about is that server-side authentication logic takes this access token from the client app, then queries the user's profile data from the IdP in order to "authenticate" the user into the server. This implementation pattern causes the real security problem, because BobApp could send the token to the attacker Bob, who can now authenticate into the server as Alice on Bob’s tablet.
>  
> Ø  and then letting another client use that token
> So “letting another client use the token” is not THE vulnerability, but an attack step that BobApp voluntarily does to exploit the server-side vulnerability.
>  
> Thanks,
> -Shuo
>  
> From: Phil Hunt [mailto:[e-mail]] 
> Sent: Friday, June 15, 2012 3:59 PM
> To: rui wang
> Cc: Francisco Corella; matake nov; Yuchen Zhou; oauth; Shuo Chen (MSR)
> Subject: Re: [OAUTH-WG] Report an authentication issue
>  
> I am a bit confused.
>  
> It sounds like you are sniffing a bearer token from an unsecured connection to a resource server and then letting another client use that token.
>  
> Is this correct?
>  
> Phil
>  
> @independentid
> www.independentid.com
> [e-mail]
> 
>  
> 
> 
>  
> On 2012-06-15, at 3:06 PM, rui wang wrote:
> 
> 
> Hi, Francisco
>  
> Thank you for your reply. Here is our response for your questions.
> 
> Ø  the attack you describe can be carried out against any app that uses the OAuth "implicit grant flow", which Facebook calls "client-side authentication".
>  
> The main concern we raised here is not about attacking client-side apps. We don’t think it is a meaningful security consequence when a client-side application (e.g., a Win8 Metro app, iPhone/iPad app) on the attacker’s tablet misidentifies the user as the victim user. Therefore, you are right about “this kind of attack can be carried out against any app  using the OAuth ‘implicit grant flow’”. In fact we won’t even call this consequence as an attack.
> The real problem is that in multiple occasions, we found that the server-side authentication logic takes an access token from the client app, then queries the user's profile data from the IdP in order to "authenticate" the user into the server. We have confirmed that the servers for Soluto Metro App, Givit Metro App and EuroCup2012 Metro App make this mistake. These are apps in the official Windows 8 App Store. We only sampled a small portion of the available apps, but believe this is a vulnerability pattern due to a common misunderstanding of the usage of the access token.
>  
> Ø  I followed the link in your message to the Sophos post, and from there the link to the article in
> The Register.  The article in The Register says that Facebook had
> "fixed the vulnerability promptly".  How did they fix it?  The
> instructions that Facebook provides for implementing "Client-side
> authentication without the JS SDK" at
> https://developers.facebook.com/docs/authentication/client-side/#no-jssdk
> still allows the attack.
>  
> I am very sorry for the confusion. The link to Sophos has nothing to do with this problem. It is about another issue we reported last year. I mentioned this because the email yesterday was sent to Facebook and the OAuth mailing list at the same time. I was trying to let the Facebook team know we had previous communication before. I should have removed this part in the version sent to OAuth. Again, sorry for not removing this reference. Please ignore it.
>  
> Thanks,
> Rui
> On Fri, Jun 15, 2012 at 1:34 PM, Francisco Corella <[e-mail]> wrote:
> Hi Nat and Rui,
> 
> Rui, you say that the vulnerability that you found was due to a
> "common misunderstanding among developers", but the attack you
> describe can be carried out against any app that uses the OAuth
> "implicit grant flow", which Facebook calls "client-side
> authentication".  No misunderstanding seems necessary.  What
> misunderstanding are you referring to?  I followed the link in your
> message to the Sophos post, and from there the link to the article in
> The Register.  The article in The Register says that Facebook had
> "fixed the vulnerability promptly".  How did they fix it?  The
> instructions that Facebook provides for implementing "Client-side
> authentication without the JS SDK" at
> https://developers.facebook.com/docs/authentication/client-side/#no-jssdk
> still allows the attack.
> 
> Nat, I agree that the blog post by John Bradley that you link to
> refers to the same vulnerability reported by Rui.  You say that some
> apps have issued a patch to fix it.  Could you explain what the fix
> was?
> 
> Francisco
>  
> From: Nat Sakimura <[e-mail]>
> To: rui wang <[e-mail]> 
> Cc: matake nov <[e-mail]>; Yuchen Zhou <[e-mail]>; oauth <[e-mail]>; Shuo Chen (MSR) <[e-mail]> 
> Sent: Thursday, June 14, 2012 1:50 PM
> 
> Subject: Re: [OAUTH-WG] Report an authentication issue
>  
> This is a fairly well known (hopefully by now) issue. We, at the OpenID Foundation, call it "access_token phishing" attack these days. See: http://www.thread-safe.com/2012/01/problem-with-oauth-for-authentication.html
>  
> Nov Matake has actually built the code on iPhone to verify the problem, and has notified bunch of parties back in February including Facebook and Apple. We have the code that actually runs on a phone, and we have successfully logged in to bunch of apps, including very well known ones. They were all informed of the issue. Some immediately issued a patch to fix it while others have not.  
>  
> The problem is that even if these apps gets fixed, the problem does not go away. As long as the attacker has the vulnerable version of the app, he still can impersonate the victim. To stop it, the server side has to completely disable the older version, which means the service has to cut off many users pausing business problems. 
>  
> Nat
> 
> On Fri, Jun 15, 2012 at 2:18 AM, rui wang <[e-mail]> wrote:
> Dear Facebook Security Team and OAuth Standard group,
> We are a research team in Microsoft Research. In January, 2011, we reported a vulnerability in Facebook Connect which allowed everyone to sign into Facebook-secured relying parties without password. It was promptly fixed after reporting. (http://nakedsecurity.sophos.com/2011/02/02/facebook-flaw-websites-steal-personal-data/)
> Recently, we found a common misunderstanding among developers of mobile/metro apps when using OAuth (including Facebook’s OAuth) for authentication. The vulnerability resulted from this misunderstanding also allows an attacker to log into a victim user's account without password.
> Let's take Soluto's metro app as an example to describe the problem. The app supports Facebook Login. As an attacker, we can write a regular Facebook app. Once the victim user allows our app to access her Facebook data, we receive an access_token from the traffic. Then, on our own machine (i.e., the "attacker" machine), we run the metro app of Soluto, and use a HTTP proxy to insert the victim's access_token into the traffic of Facebook login. Through this way, we are able to log into the victim's Soluto account from our machine. Other than Soluto, we also have confirmed the same issue on another Windows 8 metro-app Givit.
> The Facebook SDK for Android apps (https://developers.facebook.com/docs/mobile/android/build/#sdk) seems to have the possibility to mislead developers too. At least, the issue that we found is not clearly mentioned. In the SDK, we ran the sample code called "Hackbook" using Android Emulator (imagine it is an attacker device). Note that we have already received the access token of the victim user from our regular Facebook app. We then inject the token to the traffic of Hackbook. Through this way, Hackbook app on our own machine recognizes us as the victim. Note that this is not a convincing security exploit yet, because this sample code does not include the server-side code. However, given that we have seen real server-side code having this problem, such as Soluto, Givit and others, we do believe that the sample code can mislead mobile/metro developers. We also suspect that this may be a general issue of many OAuth implementations on mobile platforms, so we send this message to OAuth Standard group as well.
> We have contacted the vendors of the two vulnerable metro-apps, Soluto and Gavit.
> Please kindly give us an ack when you receive this message. If you want to know more details, please let us know.
> Best Regards,
> Yuchen Zhou, Rui Wang, and Shuo Chen
> 
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> 
>  
> -- 
> Nat Sakimura (=nat)
> Chairman, OpenID Foundation
> http://nat.sakimura.org/
> @_nat_en
>  
> 
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