CVE-2012-4406: Code Injection

Sebastian Krahmer (krahmer) reports:

swift uses pickle to store and load meta data. pickle is insecure and allows to execute arbitrary code in loads(). [...] BTW, you can read more on executing code via pickle or cPickle here: http://nadiana.com/python-pickle-insecure

https://bugs.launchpad.net/swift/+bug/1006414

Additionally:

== Pickle is insecure in a model where an untrusted user can provide the pickled data. In the Swift model the data is pickled by Swift itself and stored in memcache, so the attack vector would suppose direct write access by an untrusted user to memcached data ?

== memcached on Swift runs on every proxy servers and shared a cache so it bind on the internal network ip. For swift we always assume that the internal network needs to be secure since Swift has been designed this way.

== The commit message for the fix:

Reviewed: https://review.openstack.org/9105 Committed: http://github.com/openstack/swift/commit/e1ff51c04554d51616d2845f92ab726cb0e5831a Submitter: Jenkins Branch: master

commit e1ff51c04554d51616d2845f92ab726cb0e5831a Author: Vincent Untz <vuntz> Date: Thu Jun 21 14:37:41 2012 +0200

Do not use pickle for serialization in memcache, but JSON

We don't want to use pickle as it can execute arbitrary code. JSON is safer. However, note that it supports serialization for only some specific subset of object types; this should be enough for what we need, though.

To avoid issues on upgrades (unability to read pickled values, and cache poisoning for old servers not understanding JSON), we add a memcacheserializationsupport configuration option, with the following values:

0 = older, insecure pickle serialization 1 = json serialization but pickles can still be read (still insecure) 2 = json serialization only (secure and the default)

To avoid an instant full cache flush, existing installations should upgrade with 0, then set to 1 and reload, then after some time (24 hours) set to 2 and reload. Support for 0 and 1 will be removed in future versions.

Part of bug 1006414.

Change-Id: Id7d6d547b103b4f23ebf5be98b88f09ec6027ce4

— Red Hat