On Wed, 2010-06-16 at 14:04 -0600, Eric Blake wrote:
I'm with Stefan - the whole point of mkstemp is that the created file has 0600 permissions, and /tmp is restricted-deletion, so no other user can either overwrite the file contents or unlink it and replace it with an alternate file. Then again, gnulib documents that glibc 2.0.7 or older would create a file with group/other permissions if the umask wasn't set prior to the mkstemp() call, and gnulib's mkstemp() does not work around this issue; but that's a rather old version of glibc to be worrying about.
This has nothing to do with mkstemp(). As I said, libvirt's use of it is fine and there is no symlink race or security vulnerability by itself. The issue is that use of /tmp is not required *and* it becomes difficult to properly confine libvirtd via a MAC if you must allow execution of files in /tmp. See my answer to Stefan's question for an example scenario. -- Jamie Strandboge | http://www.canonical.com