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Date: Mon, 11 Sep 2017 15:58:45 -0400
From: Michael Orlitzky <michael@...itzky.com>
To: oss-security@...ts.openwall.com
Cc: Daniel Kahn Gillmor <dkg@...thhorseman.net>
Subject: Re: CVE-2017-12847: nagios-core privilege escalation
 via PID file manipulation

On 09/07/2017 12:22 PM, Daniel Kahn Gillmor wrote:
> 
>> I've found services that run with *two* PID files...
> 
> sigh.  are you cataloging these somewhere?  this is really valuable
> work, and it'd be great to see a list of common failures.  Do you know
> if any of them are collected under CWE or any other widely-accepted
> taxonomy?

I collected a bunch of common problems into a pull request for OpenRC:

   https://github.com/OpenRC/openrc/pull/162

I would like to have something more comprehensive for init script
writers, but we would need to consolidate some of the existing
documentation from both OpenRC and various Gentoo sources. With OpenRC
we get to cheat a little, because we always have the option to run the
daemon in the foreground and supervise it. A comparable document for
SysV init script writers would need different workarounds for the
problems that OpenRC services solve in that manner.

The motivation for those tips can be found in the Gentoo bugs I've been
filing on bugs.gentoo.org. You can find most of them by searching for
"pid" in the summary with "mjo@...too.org" as the reporter (don't forget
to include resolved bugs). It's slow going because I'm trying to provide
either a complete list of suggestions, or a rewritten init script that
does things right.


> Is there any way to automate these tests, or do we need a human to read
> each initscript and look for flaws?  Are other people helping you in
> this review?  how are you tracking/coordinating your reviews?

It's just me as far as I know. I stumbled onto this by accident while
cleaning up an OpenRC init script that was shipped as part of an
upstream package. I updated it, and then noticed that my init script was
vulnerable to the PID file trick. Then I realized that everybody else
has the same problem.

You probably need a human to make the final decision on whether or not
an init script is vulnerable, but my lame heuristic so far has been
hilariously accurate: does the init script mess with file/directory
ownership? If so, it's probably vulnerable to *something*.

I've still got a list of 100 or so to investigate that change ownership
of a directory under /var/run. Very few of those will be false positives
-- it's OK to put a socket or lock file there, but not a PID file.



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