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Date: Fri, 14 Aug 2009 20:12:00 +0200
From: Nico Golde <oss-security+ml@...lde.de>
To: oss-security@...ts.openwall.com
Cc: groff@....org, coley@...re.org
Subject: Re: CVE id request: groff (pdfroff)

Hi,
* Solar Designer <solar@...nwall.com> [2009-08-14 18:54]:
> Thank you for forwarding this info in here - it has helped.
> 
> Have you notified Werner LEMBERG, the upstream maintainer?

No I just dumped this on the list so far and hope that our 
maintainer did this. However I CCed groff@....org now.
> 
> I have some comments on "the first bug" and on groff's temporary file
> handling in general:
> 
> On Sun, Aug 09, 2009 at 03:48:17PM +0200, Nico Golde wrote:
> > First one:
> > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=538330
> > pdfroff tool of groff is creating files in a insecure manner 
> > in the /tmp directory.
> 
> There's a mitigating factor: pdfroff will use $TMPDIR (or one of three
> other env vars that it checks) if set.  On Owl, pam_mktemp sets $TMPDIR
> to point to the user's private temporary file directory upon PAM session
> setup, which is invoked on both remote and console logins, and on cron
> job invocations.

Yes I saw this, unfortunately those variables aren't set on 
Debian.

> I found your trivial patch (pdfroff.sh.diff, 389 bytes) a bit unfinished:
> 
> -  WRKFILE=${GROFF_TMPDIR=${TMPDIR-${TMP-${TEMP-"."}}}}/pdf$$.tmp
> +  WRKFILE=${GROFF_TMPDIR=$(mktemp -t -d groffXXXXXX)}/pdf$$.tmp

True this is quick and dirty and can't be considered 
complete.

> - no check for a possible mktemp error;
> - will leave the directory around upon pdfroff termination;

True, I didn't do this as groff removes the files via a trap 
before the patch and I missed that GROFF_TMPDIR is not 
pointing to a directory that was created for this usage.

> - changes semantics, but does not update documentation (the man page is
> explicit on what temporary file directories pdfroff uses).

Ok, I didn't read the manpage while writing the patch.

> I included more elaborate changes to pdfroff (both the script and the
> man page) in groff-1.20.1-owl-tmp.diff available here:
> 
> http://cvsweb.openwall.com/cgi/cvsweb.cgi/Owl/packages/groff/

The patch looks great and way more clean than my 
quick-and-dirty one. Thanks! I forwarded this to the Debian 
bug report.

[not stripping this because of the new CC]
Can someone please assign CVE ids to these issues?

> Other issues I found (and patched in groff-1.20.1-owl-tmp.diff) are:
> 
> Bugs in eqn2graph.sh, grap2graph.sh, pic2graph.sh (duplicated code)
> where these scripts would fail to properly handle the case when all
> attempts to create a temporary directory fail.  In that case, they would
> proceed to use the last-tried pathname.  Hopefully, this would just fail
> in some weird way, but it is also possible that the directory would in
> fact exist and be under someone else's control.  Since this was the last
> thing I dealt with today and I was already tired, I opted for the
> simplest fix, which was to reset the variable at the end of each loop
> iteration.  At a later time, I may drop all non-mktemp code from these
> scripts, like I did in other places.
> 
> gendef.sh and doc/fixinfo.sh created files in $TMPDIR (if defined) or in
> the current directory without any precautions.  Not an issue if $TMPDIR
> is safe or is not set, and these are only used during groff build, but
> it is an issue if someone sets $TMPDIR to /tmp or to another shared
> directory.  I've patched these to use mktemp(1).  gendef.sh is on my
> list of files accessed during groff build (which means that it could
> have been run but this is not certain); fixinfo.sh is not (so it was
> certainly not run during my build but this does not mean much for other
> builds).
> 
> contrib/gdiffmk/tests/runtests.in created files in /tmp in the worst way
> possible.  I've patched it to use mktemp(1), although maybe it should
> just use the current directory since it does so in other places anyway.
> It is on my list of files accessed during groff build.
> 
> contrib/groffer/perl/groffer.pl and contrib/groffer/perl/roff2.pl used
> only four X'es in filename patterns.  The reasonable minimum is
> considered 6; we typically use 10.  Patched to use 10.
> 
> doc/groff.texinfo (source) and doc/groff.info-2 (pre-compiled) contained
> an example for invoking an external program with ".sy", saving its
> output to a file under /tmp.  Patched to use a file in the current
> directory instead, even though this is not perfect.
> 
> Finally, we're patching configure and config.guess to use the
> mktemp-only code just to be fail-close, even though I understand the
> rationale behind the original portable code.  I am also adding a #error
> comment to src/roff/groff/pipeline.c, just to save a few minutes next
> time I or someone else looks at this code.
> 
> That's all for the patch.  However, my grep's also identified potential
> issues in install-sh and contrib/groffer/shell/*.  Since these files
> were not used during our groff package builds, I opted to remove rather
> than patch them.  So I added:
> 
> # Remove/disable unused files with temporary file handling issues in them to
> # make sure that these are in fact unused.
> rm -r contrib/groffer/shell
> echo -e '#!/bin/sh\nexit 1' > install-sh
> 
> to our groff.spec, and I also had to add
> groff-1.20.1-owl-groffer-Makefile.diff to allow groff to build without
> the contrib/groffer/shell/* files (their presence was checked by make
> even though they were not read).  On systems with Perl, groff uses the
> version of groffer written in Perl instead of this shell version, but
> there's some risk of it falling back to the shell version if Perl can't
> be run for whatever reason.
> 
> A related detail is that we force the configure script to detect the
> presence of mkstemp(3), we don't take chances:
> 
> export ac_cv_func_mkstemp=yes \
> %configure
> 
> In the case of groff, the fallback code (when mkstemp(3) is not present)
> is not that bad, though.
> 
> Speaking of my grep's, I used:
> 
> fgrep -rl /tmp .
> fgrep -rl mktemp .
> fgrep -rl tmpnam .
> fgrep -rl tempnam .
> fgrep -rl TMPDIR .
> 
> Then I briefly reviewed the files identified in this way.  Of course, I
> could have missed something, yet this would have caught the pdfroff
> issue.  We updated Owl-current to this version of groff with pdfroff in
> it just 8 days ago, and we were not as careful right away...
> 
> Alexander

Cheers
Nico
-- 
Nico Golde - http://www.ngolde.de - nion@...ber.ccc.de - GPG: 0xA0A0AAAA
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