selinux + livecd-creator, May 20, 2008

[Daniel J Walsh]

Eric Paris wrote:
> ***passwd:
> running a system with selinux enforcing/permissive (doesn't matter) and
> attempting to run livecd-creator with selinux --disabled results in
> passwd espoloding.  passwd called is_selinux_enabled() which says yes
> since /proc/mounts has an selinuxfs and the passwd calls
> selinux_enforcing() which explodes when it can't find
> a /selinux/enforce.  First discussion was to change /proc/mounts to hide
> the selinuxfs, sounds like a good plan until I realize /proc/mounts is
> actually link to /proc/self/mounts and that its getting way to complex
> tying to set up FS namespaces or whatever this is going to take.  Right
> now I'm thinking of creating a /selinux with enforce=0 in all cases
> inside the chroot, anyone see a problem with that?  (I could also work
> on fixing passwd, but i'm trying to be as 'backwards compatible' as
> possible....
> 
> ***restorecon:
> do we have an interface to see what is actually in security.xattr?
> Making use of the wonderful new deferred selinux context patch set from
> the kernel I get beautiful message like:
> 
> /sbin/restorecon reset /sbin/dump context
> system_u:object_r:unlabeled_t:s0->system_u:object_r:eparis_exec_t:s0
> 
> The file wasn't really "unlabeled_t" it just wasn't a valid label on the
> host machine.  Since restorecon/fixfiles runs over the same files like 3
> times during a livecd creation this gets rather annoying.  Do we have an
> interface I could use to make restorecon do the right comparison here?
> 
> ***allow unlabeled_t fs_t:filesystem associate:
> anyone have thoughts on how we want to handle this?  I can probably do
> some sort of fscontext= mount magic once i figure out the right fs we
> are talking about and where the script does the mount.  But then host
> policy is going to need rules to allow everything that can associate
> with fs_t with fs_allow_unlabeled_t.  Is that hard?  I assume Dan can
> help me out there.  Does this sound like a good way to solve it?  Is
> hard coding some 'fscontext=' line into livecd-creator a good idea?
> Should I just generically allow it?  Should I make livecd-creator load a
> policy module to start off and unload it at the end?   (I don't like
> this idea since I've learned livecd-creator can be pretty fragile and
> leave things half done/half undone...)
> 
> ***Invalid prefix *
> On rawhide we just dropped that stuff altogether.  Can we do the same on
> F8?  Is it actually causing a problem?  Dan, any hints on how I can make
> the system lie to you?
Can't you just mount /dev/null on /selinux/context to get this to always
succeed?
> 
> Needless to say, I successfully built an F8 livecd with types not known
> tot he host system on rawhide today, booted, and logged in.
> 
> tomorrow I spend more time typing to make the policy for livecd-creator
> a bit better.....
> 
> -Eric
>