CVE Request - pimd - Insecure file creation in /var/tmp

[Steve Kemp <steve () steve org uk>]

  We received this report recently:

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Hi!

There is a simple security hole in pimd allowing a user to destroy any
file in the filesystem. On USR1, pimd will write to /var/tmp/pimd.dump
a dump of the multicast route table. Since /var/tmp is writable by any
user, a user can create a symlink to any file he wants to destroy with
the content of the multicast routing table.

Attached is a simple patch that will instruct pimd to write the dump
to /var/lib/misc which is writable by root only and seems a valid
target according to the FHS (state files that don't need a
subdirectory).

This patch may cause tools that were sending USR1 and waiting for a
/var/tmp/pimd.dump file fail. I don't have a solution for this.

The patch also applies to /var/tmp/pimd.cache which is not implemented
yet but still creates the file when receiving USR2 signal. Despite its
name, this is also a state file, not a cache. The patch also just
drops the possibility to use /usr/tmp/pimd.dump based on some C
preprocessor conditions since I don't know if the preconditions would
work correctly on Debian/kFreeBSD.

Attachment: pimd-insecure-file-creation.patch
Description: