Re: post to bugtraq about "session fixation"

[securityarchitect () hush com]

With respect I think its a great marketing paper but nothing more. You should never allow the same token to be used 
over HTTP that is then valid over SSL. At least one variant of this attack relies on that assumption.

Correct way if for the user to enter username and password over SSL and session cookie is set to that browser session 
over SSL. A pre-fixed cookie would get you to the public site (which maybe customized for a user experience but not 
show logged in details) but shouldn't get you to anywhere other than a login screen.

This paper also assumes that application session management is closely tied to web server session management. IMHO its 
not and this is a good reason why not. People think it is cause IIS and others still sends ASPSession IDs by default 
but just because the cookie protcol says they get returned if the domain path matches, doesn't mean to say they get 
processed by an app.

This is nothing new (although a good write-up).

On Wed, 18 Dec 2002 12:13:26 -0800 Alex Russell <alex () netWindows org> wrote:
> I don't know if anyone else has seen this yet:
>
>       http://online.securityfocus.com/archive/1/303838/2002-12-15/2002-
> 12-21/0
>
> but I thought it would be on topic here. I realize that it's something 
> of a 
> rehash of the session authentication discussions we've had before,
> but I'd 
> like to point out that it does expose a weak property of the "one 
> sessionID 
> for everything" model that's been proposed thust far, which is that 
> it does 
> not allow a interaction with the client to re-instate whatever security 
> may 
> have been previously broken.
>
> I think that in earlier discussions, I wasn't able to adequately 
> articulate 
> why I felt that issuing a new nonce for ever privledged operation 
> made more 
> sense (and why, correspondingly, you should never send the "real" 
> session 
> ID along with said nonce), but this article confirms what my gut 
> was 
> telling me: if you guard each action individually and require that 
> there is 
> a continuious line of known good iteractions, you'll be safer in 
> the long 
> run. 
>
> The paper also points out the folly of assuming that client input 
> is somehow 
> "right" without validating it. Why in the world would an app server 
> ever 
> allow the end user to present to it the session ID that it will 
> use for 
> that client's continued interactions?
>
> -- 
> Alex Russell
> alex () netWindows org
> alex () SecurePipe com



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