(RHSA-2012:1379) Important: openstack-swift security update

OpenStack Swift (http://swift.openstack.org) is a highly available,
distributed, eventually consistent object/blob store.

It was found that OpenStack Swift used the Python pickle module in an
insecure way to serialize and deserialize data from memcached. As
memcached does not have authentication, an attacker on the local network,
or possibly an unprivileged user in a virtual machine hosted on OpenStack,
could use this flaw to inject specially-crafted data that would lead to
arbitrary code execution. (CVE-2012-4406)

Red Hat would like to thank Sebastian Krahmer of the SUSE Security Team for
reporting this issue.

Note: The fix for CVE-2012-4406 is not enabled by default, and requires
manual action on the affected Proxy nodes. This update adds a
“memcache_serialization_support” option. It is configured in
“/etc/swift/proxy-server.conf” and is set to “0” by default. This default
setting is vulnerable to CVE-2012-4406.

To enable the fix, this option must be changed; however, the required
changes can have a temporary, large performance impact. The following
instructions aim to minimize performance issues:

1. Install the updated openstack-swift packages.

2. In “/etc/swift/proxy-server.conf”, set the
   “memcache_serialization_support” option in the memcache/[filter:cache]
   section to “1”. (The default value, “0”, leaves you vulnerable to
   CVE-2012-4406.) When set to “1”, the JSON (JavaScript Object Notation)
   format is used but pickle is still supported. This configuration is still
   vulnerable, but new data will be stored in JSON format.

3. After setting the option to “1”, run “service openstack-swift-proxy
   restart”.

4. After 24 hours, set the “memcache_serialization_support” option in
   “/etc/swift/proxy-server.conf” to “2”. “2” is the secure option: only JSON
   is used.

5. After setting the option to “2”, run “service openstack-swift-proxy
   restart”.

If “memcache_serialization_support” is set directly from “0” to “2”, all
data in memcached will be flushed and re-created. This can lead to a
temporary, large performance impact.

All users of openstack-swift are advised to upgrade to these updated
packages, which correct this issue.