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Date: Fri, 4 Oct 2013 11:11:08 +0300
From: Andri Möll <>
Subject: Re: A note on cookie based sessions

A lot of these frameworks or libraries also offer password remembering features which are often implemented as separate long lived token cookies that can't be invalidated server-side or can't be invalidated per-machine.

Devise for Ruby on Rails does this too, for example, but because of a side-effect of the implementation it can be invalidated by changing the password — the token is a substring of the password hash.


On Oct 4, 2013, at 9:07 AM, Kurt Seifried <> wrote:

> Hash: SHA1
> On 10/03/2013 11:26 PM, Donald Stufft wrote:
>> I don't think this really is a vulnerability is it? I mean it's
>> basically how the internet works. The only difference between a
>> cooke backed session and a regular session is that there's no
>> server side session to destroy. At least in Django's case, It's not
>> a permanent session though, they are only good for a limited amount
>> of time before the signature on the cookie expires.
>> If you have access to the session cookie you've already won the
>> game, you've gotten an XSS or MITM and can do much worse then a
>> session cookie.
> Apologies I should have been more explicit. The difference is that
> with a stateful backend when the user  hits log out they are logged
> out in the back end, so the cookie can't be used any more. With these
> stateless solutions there is no way to prevent cookie reply other than
> encoding a time out in the cookie (so I guess you could encode like a
> short time out and keep rotating the cookie to close the window of
> opportunity).
> The concern is people using public terminals, cookie stealing attacks,
> XSS in the website you're using, etc allowing an attacker to snag your
> cookie and use it post "log out".
> - -- 
> Kurt Seifried Red Hat Security Response Team (SRT)
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