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Message-ID: <20120209082436.GA14572@dztty>
Date: Thu, 9 Feb 2012 09:24:36 +0100
From: Djalal Harouni <tixxdz@...ndz.org>
To: oss-security@...ts.openwall.com
Subject: Re: Linux procfs infoleaks via self-read by a
SUID/SGID program (was: CVE-2011-3637 Linux kernel: proc: fix Oops on
invalid /proc/<pid>/maps access)
On Thu, Feb 09, 2012 at 10:55:23AM +0400, Solar Designer wrote:
> On Thu, Feb 09, 2012 at 03:31:34AM +0100, Jason A. Donenfeld wrote:
> > On Wed, Feb 8, 2012 at 11:12, Solar Designer <solar@...nwall.com> wrote:
> > > BTW, what version of chsh did you test this with and what behavior do
> > > you observe? I was not able to get anything useful in this way out of
> > > Owl's chsh (once enabled for non-root) - it just asks for the password,
> > > but somehow fails to read it if one is entered on the tty (perhaps
> > > there's some inconsistency in use of the tty vs. fd 0). I suppose I'd
> > > need to get past successful authentication for chsh's input to be
> > > treated as the new shell name, in which case it'd get printed out (such
> > > as in an error message) or/and put in /etc/passwd.
> >
> > zx2c4@...C4-Laptop ~/Projects/Ploits/Local/CVE-2012-0056 $ gcc maps.c
> > zx2c4@...C4-Laptop ~/Projects/Ploits/Local/CVE-2012-0056 $ ./a.out
> > Changing the login shell for zx2c4
> > Enter the new value, or press ENTER for the default
> > Login Shell [/bin/bash]: chsh: Invalid entry:
> > 00400000-00408000 r-xp 00000000 fd:00 1444794
> > /usr/bin/chsh
>
> Hmm. It does not even ask you for the password. Perhaps you have
> CHFN_AUTH in /etc/login.defs set to "no" or not set at all? (On Owl,
> it's "yes".)
Yes it seems that it does not require a password, and this is an
arbitrary /proc/<pid>/ info leak (at least for some of the files), I've
also experienced this.
In this case the config of /usr/bin/chsh will help, since we avoid the
lseek() which will fail on arbitrary files.
> Alexander
--
tixxdz
http://opendz.org
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