Re: [OAUTH-WG] problem statement

[Justin Richer <[e-mail]>]

Mike,

The basic argument here is that if the app wants to do bad things, and
you go through the process of authorizing it, it's going to be able to
do bad things. Not just to your stolen credentials, either, since it's
now got an access token too.

OAuth's trust model does work with installed applications -- however,
there are several caveats. This is one of them, as is the fact that they
can't be shipped with secured secrets (ie, client secrets). And it's
exactly this acquiescence to their limitations that opens the way for
things like the username/password flow in OAuth2. In this flow, the app
just asks for the user's username and password directly and exchanges
them for an access token. There is still a distinction from logging in
directly with the user's credentials to the API endpoint though. First,
the user's credentials don't get tossed out onto the wire with every
request. This lessens the susceptibility to theft in transmission.
Second, the app doesn't *have* to store the credentials. After the first
step goes through and the app gets a token, it can toss them. That way
nobody can steal the credentials out of an on-disk store after the fact.
If it wants to hang on to them, then yeah, you're absolutely right -- it
has your credentials and you're hosed. But nothing in the OAuth protocol
is going to force a misbehaving application to not do that. Just like
nothing in the OAuth protocol is going to stop phishing attempts to look
like the Twitter login screen. 

A solution to not letting an app steal your credentials is to not use
credentials in the first place and to use things like a rotating token
or a client-side certificate instead of a username/password to
authenticate the user during the authoirzation flow. Since OAuth doesn't
care how the user authenticates in the verification code flow, you don't
even have to change your client code. We actually had this happen
locally when developers moved from one environment that used
username/password and into another that used OpenID. The OAuth code
didn't change at all between them.

But ultimately, a bad app is going to be a bad app, and you need to be
careful what software you run and where you type your password. I think
it's a mistake of this group to flippantly ignore the threat, but at the
same token this reality does not make the OAuth protocol or its
underlying model useless.

 -- Justin



On Tue, 2011-09-06 at 14:34 -0400, Michael Thomas wrote:
> Eran Hammer-Lahav wrote:
> > Don't install crap on you device or computer. OAuth is the least of your concern if you install bad software. 
> > 
> > If there was a solution to this we would not need an antivirus. 
> 
> How exactly does an end user know what is "crap" or not? Or are you just dismissive of apps in
> general? I don't think that apple and google are going to close up shop because it breaks oauth's
> trust model.
> 
> Mike
> 
> > 
> > EHL 
> > 
> > On Sep 6, 2011, at 11:23, "Michael Thomas" <[e-mail]> wrote:
> > 
> >> Eran Hammer-Lahav wrote:
> >>> I agree. If you are going to install a native app, you better trust it not to do bad things. Grabbing your password is the least interesting thing such an app can abuse. I don't see any need to change the v2 draft. 
> >> How, exactly, is the user supposed to protect themselves against rogue apps?
> >> It sounds like the solution is to tell them to never use oauth in an app at all.
> >>
> >> Is oauth only intended to be used on standalone trustable web browsers? I don't recall
> >> seeing that anywhere.
> >>
> >> Mike
> >>
> >>> EHL
> >>>
> >>> On Sep 6, 2011, at 11:10, "Igor Faynberg" <[e-mail]> wrote:
> >>>
> >>>> Mike,
> >>>>
> >>>> You've got the problem statement right: allowing the user to authorize  
> >>>> resource access to another party without divulging user's credentials is 
> >>>> the objective of OAuth. You are also right in that the attack you have 
> >>>> described defies the whole purpose of OAuth.  I do not think though that 
> >>>> it is related to OAuth per se.
> >>>>
> >>>> To this end, the security work led by Torsten has thoroughly analyzed 
> >>>> the protocol and specified protection against multiple protocol 
> >>>> attacks.  From what you described, it appears to me that the attack you 
> >>>> mention is not related to the protocol but rather to the user's 
> >>>> environment.  There is no possible protection from key loggers that a 
> >>>> protocol can implement. I could be mistaken; in any case, it looks like 
> >>>> the problem rests with the implementation of WebView.
> >>>>
> >>>> If I am wrong, I would appreciate a detailed description of what happened.
> >>>>
> >>>> Igor
> >>>>
> >>>> On 9/6/2011 1:40 PM, Michael Thomas wrote:
> >>>>> Hi all,
> >>>>>
> >>>>> Barry suggested that I might subscribe and explain what I sent him.
> >>>>>
> >>>>> My basic problem is that in neither the protocol nor the threats drafts,
> >>>>> I can't seem to find what problem is actually trying to be solved with
> >>>>> oauth, and what assumptions you're making about various elements.
> >>>>>
> >>>>> Here's what I did. I've written an app, and I wanted re-integrate the
> >>>>> ability to send tweets after they deprecated Basic. So the app has a
> >>>>> webView (android, iphone...) which it obviously completely controls.
> >>>>> With oauth, the webview UA will ultimately redirect off to Twitter's
> >>>>> site to collect the user's credentials and grant my app's backend an
> >>>>> access token (sorry if I get terminology screwed up, i'm just coming
> >>>>> up to speed).
> >>>>>
> >>>>> What occurs to me is that webview affords exactly zero protection from
> >>>>> my client (ie, the app) from getting the user's twitter credentials. All
> >>>>> I have to do is set up a keypress handler on that webview and in a few
> >>>>> minutes of hacking I have a key logger. etc.
> >>>>>
> >>>>> So what I can't tell is whether this is a "problem" or not, because I
> >>>>> don't know what problem you're trying to solve. If the object of oauth
> >>>>> isn't to keep user/server credentials out of the hands of a third party,
> >>>>> then what is it trying to solve? Is there an expectation that the
> >>>>> UA is trusted by the user/server? What happens when that's not the case?
> >>>>>
> >>>>> Regardless of whether I'm misunderstanding, it would sure be nice to have
> >>>>> both the problem and your assumptions laid out, hopefully with some 
> >>>>> prominence
> >>>>> so you don't get these sort of dumb questions.
> >>>>>
> >>>>> Mike
> >>>>> _______________________________________________
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