atheme.org Security Advisory
ASA-2012-03-01

Original release: March 20, 2012.
Last update: March 20, 2012.

Copyright (c) 2012 atheme.org and it's contributors.
All rights reserved.

Distribution of this document in full, or in part is allowed,
provided that it remains in unmodified form and the above
copyright notice and this permission notice remain unchanged.

Topic: Improper cleanup of CertFP entries may result in undefined
       behaviour (privilege escalation or crash).

Versions affected: 5.2.0 - 5.2.6, 6.0.0 - 6.0.9, 7.0.0-alpha1 - 7.0.0-beta1

CVSSv2 vector: AV:N/AC:M/Au:M/C:C/I:P/A:C/E:F/RL:O/RC:C

CVSSv2 base score: 7.5

Access vector: network
Access complexity: medium
Authentication requirement: multiple instances

Confidentiality impact: complete
Integrity impact: partial
Availability impact: complete

CVSSv2 temporal score: 6.2

Exploitability: functional exploit exists
Remediation level: official fix
Report confidence: confirmed

Summary:

Improper cleanup of CertFP entries may result in undefined behaviour for
an IRC system using Atheme IRC Services as an IRC services implementation.

If an account is expired or dropped, CertFP entries will linger, occasionally
pointing to an unallocated object (which triggers an exceptional condition)
or another account object.  Thusly, if an attacker creates an account and then
registers their CertFP fingerprint with that account and deletes it, they may
be able to gain access to another account in the future without that account
being aware of it.

Such a condition can also cause inconsistencies in the object store when
marshalled to disk, resulting in an exceptional condition on demarshalling,
such as when services is restarted.

This vulnerability was introduced when CertFP support was added to Atheme
IRC Services.

A denial of service against an IRC network's services daemon can have
devastating effects as a typical IRC network is dependent on the
availability of services for directory, nickname and channel ACL
enforcement.

This vulnerability was discovered by "Aaron M. D. Jones" and was reported
to us by him.  The bug report is at: http://jira.atheme.org/browse/SRV-166

Upgrading to the latest release for the branch you are using is strongly
encouraged.

A patch release for all currently maintained versions of Atheme IRC
Services was released on the same day, March 20th.

Mitigation:

If your current version of Atheme is maintained, patch releases are
available from the Atheme website at http://www.atheme.net/. These
versions are Atheme 5.2.7, Atheme 6.0.10 and Atheme 7.0.0-beta2.

The SHA256 checksums for these versions are:

atheme-services-5.2.7.tar.bz2:
  8451472fd23b9bbc6dd9c989b4d68c4d50ba1e827b621776533781e9fbfa8319

atheme-services-6.0.10.tar.bz2:
  9a2b3954316d29ae0cd546edc9c2b6169bae448f982dbd76ca3efd84c271d0c8

atheme-services-7.0.0-beta2.tar.bz2:
  d8a52d96d4466f3e5a1ef28ddd562d38575b768b63ad17ced470ec2a1f0e17f1

This bug does not exist in any unmaintained version of Atheme as far
as we are aware.

Details:

The account destructor did not call mycertfp_delete() on the CertFP entries
associated with an account object.  As a result, the certfp entries linger.

To exploit, register an account with your CertFP entry and then delete it.
Then reconnect to the network after a couple of new accounts are registered.
You may be authenticated to one of those new accounts, or services will crash.

Contact:

For further information about this security advisory, please contact
the Atheme developers at irc.atheme.org #atheme.

For more information about atheme.org, please visit the following resources:

  - IRC: irc.atheme.org #atheme-project
  - Web: http://www.atheme.org/