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Advisory

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	     Xen Security Advisory CVE-2013-2007 / XSA-51
                              version 2

           qemu guest agent (qga) insecure file permissions

UPDATES IN VERSION 2
====================

Public release.

ISSUE DESCRIPTION
=================

The qemu guest agent creates files with insecure permissions when
started in daemon mode.

IMPACT
======

The qemu guest agent is not used by default in Xen systems.

If it is used in a particular guest, unprivileged guest processes
might be able to escalate their privilege to that of the guest.

VULNERABLE SYSTEMS
==================

We are not aware of any Xen installations using the qemu guest agent.

However, the program is built and installed (as the executable
`qemu-ga') as part of the Xen management tools by the Xen build
system.  It is possible that a system administrator, or downstream
system integrator, might have arranged to execute qemu-ga.

If you have not taken steps to run qemu-ga, you are not vulnerable.

MITIGATION
==========

Disabling the guest agent will eliminate the vulnerability.

RESOLUTION
==========

Patches to resolve this problem are available from the upstream qemu
project via the usual channels.  The Xen Project Security Team do not
intend to provide or distribute patches for this vulnerability.

DETAILS
=======

At the time of writing the information we have about this
vulnerability is as follows:

  Subject: [PATCH] qga: set umask 0077 when daemonizing (CVE-2013-2007)

  The qemu guest agent creates a bunch of files with insecure permissions
  when started in daemon mode. For example:

    -rw-rw-rw- 1 root root /var/log/qemu-ga.log
    -rw-rw-rw- 1 root root /var/run/qga.state
    -rw-rw-rw- 1 root root /var/log/qga-fsfreeze-hook.log

  In addition, at least all files created with the "guest-file-open" QMP
  command, and all files created with shell output redirection (or
  otherwise) by utilities invoked by the fsfreeze hook script are affected.

  ...

For authoritative further information, and patches, please refer to
the information provided by the qemu upstream project.
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