oss-security - [CVE-2015-0839] hp-plugin binary driver verification

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Message-ID: <20150529130035.GA28407@enricozini.org>
Date: Fri, 29 May 2015 15:00:35 +0200
From: Enrico Zini <enrico@...icozini.org>
To: oss-security@...ts.openwall.com
Subject: [CVE-2015-0839] hp-plugin binary driver verification

Hello,

background history:

2015-03-10: I reported this issue to the Debian security team
2015-03-12: The Debian security team assigned CVE-2015-0839 from the
            Debian pool
2015-03-16: I reported this issue upstream, privately, at
            https://bugs.launchpad.net/bugs/1432516
2015-05-29: There has been no reply from upstream so far, so I am making
            a public report.

The issue:

I was forced to run hp-plugin to download a binary driver for the new
printer, and I noticed this bit:

  Downloading plug-in from:
  Receiving digital keys: /usr/bin/gpg --homedir /home/enrico/.hplip/.gnupg --no-permission-warning --keyserver pgp.mit.edu --recv-keys 0xA59047B9
  Creating directory plugin_tmp
  Verifying archive integrity... All good.

The use of a short key ID worries me, because it is now trivial to
generate keys with arbitrary key IDs, and gpg --recv-keys will happily
download all those it finds. Also, pgp.mit.edu is a keyserver where
everyone can upload arbitrary keys.

You can run "gpg --recv 70096AD1" to play with multiple keys having the
same key ID.

I assume hp-plugin is open to downloading and verifying plugins signed
by any key that one can verify that have that short key ID, and that
with that and some fiddling with DNS one can cause systems running
hp-plugin to download and run malicious code.

A quick fix would be to use the full fingerprint instead of the key id.

Regards,

Enrico

-- 
GPG key: 4096R/E7AD5568 2009-05-08 Enrico Zini <enrico@...icozini.org>

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