Gentoo: sharutils Insecure temporary file creation
Posted by Benjamin D. Thomas   
Gentoo The unshar utility is vulnerable to symlink attacks, potentially allowing a local user to overwrite arbitrary files.
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Gentoo Linux Security Advisory                           GLSA 200504-06
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                                            http://security.gentoo.org/
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  Severity: Normal
     Title: sharutils: Insecure temporary file creation
      Date: April 06, 2005
      Bugs: #87939
        ID: 200504-06

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Synopsis
========

The unshar utility is vulnerable to symlink attacks, potentially
allowing a local user to overwrite arbitrary files.

Background
==========

sharutils is a collection of tools to deal with shar archives.

Affected packages
=================

    -------------------------------------------------------------------
     Package             /   Vulnerable   /                 Unaffected
    -------------------------------------------------------------------
  1  app-arch/sharutils      < 4.2.1-r11                  >= 4.2.1-r11

Description
===========

Joey Hess has discovered that the program unshar, which is a part of
sharutils, creates temporary files in a world-writable directory with
predictable names.

Impact
======

A local attacker could create symbolic links in the temporary files
directory, pointing to a valid file somewhere on the filesystem. When
unshar is executed, this would result in the file being overwritten
with the rights of the user running the utility, which could be the
root user.

Workaround
==========

There is no known workaround at this time.

Resolution
==========

All sharutils users should upgrade to the latest version:

    # emerge --sync
    # emerge --ask --oneshot --verbose ">=app-arch/sharutils-4.2.1-r11"

References
==========

  [ 1 ] Ubuntu Advisory
        http://www.ubuntulinux.org/support/documentation/usn/usn-104-1

Availability
============

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

  http://security.gentoo.org/glsa/glsa-200504-06.xml

Concerns?
=========

Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
=======

Copyright 2005 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

http://creativecommons.org/licenses/by-sa/2.0