bugtraq - tar preserves setuid bit

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Date: Fri, 5 Aug 2005 00:52:50 +0100
From: Imran Ghory <imranghory@...il.com>
To: bugtraq@...urityfocus.com
Subject: tar preserves setuid bit

(essentially the same as the unzip vulnerability CAN-2005-0602 except
that it only works against the root user)

================================
tar preserves setuid bit
================================

Software: tar
Version: 1.15.1
Software URL: <www.gnu.org/software/tar/tar.html>
Platform:  Unix, Linux.
Severity: Medium

Vulnerable software
====================

tar 1.15.1 and previous versions running on unix.

Vulnerability
==============

If running as the root user tar restores the original permissions to
extracted files, this includes the setuid bit. No warning is given to
the user that this has happened.

The default behaviour of tar under root is not to change ownership of
the file to root. However owner information is extracted from the tar
file, so a trivialy modified tar file can ensure the owner of the
extracted files is the root user.

This allows for the creation of arbitary setuid executable owned by
the root user if the root user extracts the files from a malliciously
crafted tar file.

---
Imran Ghory