[Openstack-security] [Bug 1074087] Re: XenApi migration driver should not use shell=True with Popen
Euan Harris
euan.harris at citrix.com
Thu Jul 25 09:04:27 UTC 2013
The analysis in comment #2 suggests that, since the calls to Popen and
split don't take any user input, this bug doesn't allow an attack from
the outside. Therefore it isn't necessary to backport it.
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https://bugs.launchpad.net/bugs/1074087
Title:
XenApi migration driver should not use shell=True with Popen
Status in OpenStack Compute (Nova):
Fix Released
Bug description:
The XenApi drivers split a string to create an array for
subprocess.Popen, rather than passing an array directly. This invites
the potential for command injection / manipulation.
There is no clearly valid reason to use string splitting here when
arguments can be passed, as elsewhere, directly into Popen.
The behavior here is present in current Trunk, Folsom, and Essex. Per
Trunk and Folsom, _rsync_vhds calls plugins.utils.subprocess to
perform the splitting. In Essex, this behaviorism was present
directly in migration/transfer_vhd.py, rather than in utils.py.
Earlier releases have not been evaluated.
I am not certain if this is directly exploitable. The user field is
inserted into the generated strings used for command-line execution,
and it does seem that Keystone allows usernames to contain arbitrary
tokens/characters such as spaces. It is not clear to me if the user
field directly matches that in Keystone, if the user field is
otherwise validated in the API, etc. Other fields inserted into the
command string seem to be internally generated.
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