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Date: Fri, 28 Mar 2014 08:33:38 -0700
From: Chris Steipp <csteipp@...imedia.org>
To: oss-security@...ts.openwall.com
Subject: Re: CVE request: MediaWiki 1.22.5 login csrf

On Mar 28, 2014 7:54 AM, "Florent Daigniere" <
florent.daigniere@...stmatta.com> wrote:
>
> Sorry to be thick here but it still doesn't make any sense to me...
>
> The session-id should be renewed upon login AND any credential/privilege
> change (that includes password changes). This protects against session
> fixation attacks (where the attacker coerce a user into using a session
> he controls).
>
> On these pages, there's usually no need for anti-CSRF protection as they
> tend to require credentials (something the attacker, by definition,
> doesn't have).

Slightly different attack. The attacker (who knows their own password and
chooses the reset-to password) was able to cause a logged out user (victim)
to login with the attacker's account via the change password form.

This attack is somewhat specific to mediawiki since we allow users to
define JavaScript that will be loaded on pages they visit while logged
in... So the victim in this case would run the attacker's personal
JavaScript.

>
> Are you saying that Mediawiki has a logic bug (some form of
> authorization bypass) allowing any authenticated user to change someone
> else's credentials without knowing them? If so, it's a different
> category of bug and there again, the control is unlikely to be "adding
> an anti-CSRF token".
>
> Florent
> PS: While we're at it: yes you should be comparing anti-CSRF tokens in
> constant-time, unlike what
> https://bugzilla.wikimedia.org/show_bug.cgi?id=62497#c13 is suggesting.
>
>
> On Fri, 2014-03-28 at 07:19 -0700, Chris Steipp wrote:
> > The session-id is renewed when the user successfully logs in with a
> > password reset. The issue that we patched was that the anti-CSRF token
for
> > non-authenticated users on the password change form was guessable, and
> > would remain that way even if we regenerated the user's session-id each
> > time they accessed the password rest / login form.
> >
> >
> >
> >
> > On Fri, Mar 28, 2014 at 2:23 AM, Florent Daigniere <
> > florent.daigniere@...stmatta.com> wrote:
> >
> > > On Thu, 2014-03-27 at 18:37 -0700, Chris Steipp wrote:
> > > > Hi, we just patched a login CSRF in MediaWiki today. An attacker
could
> > > > login a victim as the attacker. Can we get a cve assigned for this?
> > > >
> > > > Patch:
> > > >
> > >
https://gerrit.wikimedia.org/r/#/c/121517/1/includes/specials/SpecialChangePassword.php
> > > >
> > > > Release announcement:
> > > >
> > >
http://lists.wikimedia.org/pipermail/mediawiki-announce/2014-March/000145.html
> > > >
> > > > Wikimedia bug:
> > > > https://bugzilla.wikimedia.org/show_bug.cgi?id=62497
> > >
> > >
> > > That looks like a session-fixation bug to me; not a CSRF... and
> > > therefore it's the wrong control: the session-id should be "renewed",
> > > that's all.
> > >
> > > Florent
> > >
>

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