Re: [OAUTH-WG] WGLC on draft-ietf-oauth-v2-threatmodel-01, ends 9 Dec 2011

[Michael Thomas <[e-mail]>]

On 12/16/2011 03:02 AM, Mark Mcgloin wrote:
> Michael,
>
> I will review the comments from Phil where he suggests some changes in
> section 4.1.4 of the threat model
>
> I am unclear exactly what you are proposing. If you want to propose a
> clearly worded revamp of that section in the next couple of days, I am
> willing to review and accept legitimate changes. Clearly worded means
> concise, technically accurate and devoid of alarmist phrases and words used
> out of context, such as existential. Can I suggest you review with a
> colleague before posting here.
>    

Barry -- I have gone through this section and made comments
and was blown off seemingly without reading them at all, and
now I'm being told to come up with text for which I can be blown
off again: "Can I suggest you review..."

The fact of the matter is that my comments say that the
threats are understated and mitigations that are proposed do not
work. It's not my job alone to fix this. It's the working group's.
In fact if I were to propose text, it would be along the lines of
"can't be mitigated" because I do not know how to fix them. If
nobody else can come up with a better mitigation, then that
*is* what should be there, not some hand waving nonsense that
doesn't work.

Mike, "instruct users..." feh

> Regards
> Mark
>
> [e-mail] wrote on 15/12/2011 18:15:45:
>
>    
>> From:
>>
>> Michael Thomas<[e-mail]>
>>
>> To:
>>
>> Phil Hunt<[e-mail]>
>>
>> Cc:
>>
>> Barry Leiba<[e-mail]>, oauth WG<[e-mail]>
>>
>> Date:
>>
>> 15/12/2011 18:16
>>
>> Subject:
>>
>> Re: [OAUTH-WG] WGLC on draft-ietf-oauth-v2-threatmodel-01, ends 9 Dec
>>      
> 2011
>    
>> Sent by:
>>
>> [e-mail]
>>
>> On 12/15/2011 09:54 AM, Phil Hunt wrote:
>>      
>>> Note: one change recommended below...
>>>
>>> With regards to 4.1.4…
>>> 4.1.4.  Threat: End-user credentials phished using compromised or
>>>           embedded browser
>>>
>>>      A malicious application could attempt to phish end-user passwords
>>>        
> by
>    
>>>      misusing an embedded browser in the end-user authorization process,
>>>      or by presenting its own user-interface instead of allowing trusted
>>>      system browser to render the authorization user interface.  By
>>>        
> doing
>    
>>>      so, the usual visual trust mechanisms may be bypassed (e.g.  TLS
>>>      confirmation, web site mechanisms).  By using an embedded or
>>>        
> internal
>    
>>>      client application user interface, the client application has
>>>        
> access
>    
>>>      to additional information it should not have access to (e.g. uid/
>>>      password).
>>>
>>>
>>> [mat] I think it's also worth mentioning either here, or in another
>>> threat that there is a further social engineering misuse/attack where
>>>        
> an
>    
>>> app offers/demands to keep your credentials so that you don't have to
>>>        
> go
>    
>>> through the authorization rigmarole. Users are already conditioned to
>>> give their credentials up to do things -- just this morning I
>>>        
>> noticed facebook
>>      
>>> asking for my email password which they promise with sugar on top to
>>>        
> not
>    
>>> store. It might be worth mentioning that things like CAPTCHA could be
>>> deployed to defend against that sort of attack/misuse.
>>>
>>> [Phil] I don't think we need to really add much here. We could
>>>        
>> write whole essays on this topic and likely will.
>>      
>>> I think the point is simply to educate the client developer that
>>>        
>> there is no need for a client application to ever have access to a
>> raw uid/password (or any other user credential).
>>      
>>> [/Phi]
>>>
>>>        
>> Remember: I came here not understanding whether this threat was real or
>>      
> not.
>    
>> A threat document that can't be bothered to elaborate on one of the
>>      
> biggest
>    
>> existential  threats to the protocol is worthless. The way it is worded
>> now does
>> not make it crystal clear that, yes, this means UIWebView's in iPhone
>> apps, etc too.
>> It should because it needs to scream: THIS THREAT APPLIES TO YOU, AUTH
>> SERVER.
>>
>>
>>      
>>> [snip]
>>>
>>>      Countermeasures:
>>>
>>>      o  Client developers and end-user can be educated to trust an
>>>         external System-Browser only.
>>>
>>>
>>> [mat] I assume that this is in here just for the amusement factor
>>>        
> because
>    
>>> it is not a credible countermeasure.
>>>
>>> [Phil] I agree, Firefox recently demonstrated how poorly users
>>>        
>> recognize the security signals in the browser by dropping the "lock"
>> icon without announcement. When I found out, I had already been
>> using it for some time and hadn't noticed.  This counter measure
>> should be changed to:
>>      
>>> o The OAuth flow is designed so that client applications never
>>>        
>> need to know user passwords. Where possible Client applications
>> SHOULD avoid directly asking for user credentials during an
>> authorization flow.
>>      
>>> [/Phil]
>>>
>>>        
>> The basic problem here is that the client app is not trusted. So if it's
>> a bad
>> actor this admonition will be ignored. If it's a good actor, there
>> wasn't a threat
>> in first place. So the mitigation completely misses the mark.
>>
>>      
>>>      o  Client applications could be validated prior publication in a
>>>         application market.
>>>
>>> [mat] How would this be done in practice?
>>> [Phil] I think this needs to change to:
>>>
>>> o Client applications could be validated for acceptable practices
>>>        
>> by the Resource Site provider prior to issuing production Client
>>      
> Credentials.
>    
>>>        
>> When, exactly, can we expect to see this in the field? Neither Twitter
>> or Facebook
>> do this. And even if they were so inclined, the draft provides exactly
>> zero guidance
>> as to what exactly that "validated" might mean in practice. The way I
>> read this is:
>> "we don't know how to mitigate this".
>>      
>>> [/Phil]
>>>      o  Client developers should not collect authentication information
>>>         directly from users and should instead use redirects to and back
>>>         from a trusted external system-browser.
>>>
>>>
>>> [mat] How would the resource/authentication server enforce such a
>>>        
> thing?
>    
>>> [Phil] This is a best practice for the client developer. [Phil]
>>>
>>>
>>>        
>> I don't even know what that means in the context of embedded apps.
>> Has anybody even tried this? At the very least, an example flow might
>> be useful for the uninitiated client developer.
>>
>> Mike
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>>      
> >