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Re: Fedora buildsys and SELinux



On Tue, 2008-04-22 at 16:58 +0200, Tomas Mraz wrote:
> > Bill Nottingham wrote:
> > > James Morris (jmorris namei org) said: 
> > >>> * All the parties are here now needed to figure this out
> > >>> * Someone better than me is going to reply with specifics about what is
> > >>> not working in the buildsys
> > >>> * We all agree it's pretty important to get this figured out in a good
> > >>> way
> > >> Can you please explain specifically what the problem is?
> > > 
> > > You cannot create files in a chroot of a context not known by the
> > > host policy. This means that if your host is running RHEL 5, you are
> > > unable to compose any trees/images/livecds with SELinux enabled for
> > > later releases.
> > > 
> > > Bill
> > > 
> > > --
> > > fedora-selinux-list mailing list
> > > fedora-selinux-list redhat com
> > > https://www.redhat.com/mailman/listinfo/fedora-selinux-list
> > Just catching up on this email chain.
> > 
> > The far more insidious problem is the act of loading policy in the
> > chroot effects the kernel of the host.  So processes that are running in
> > the host become invalidated when the client loads a policy.  This
> > happens even in the case where you are building a chroot environment on
> > the SAME os.  Since the spec file is running semanage commands to modify
> > and add unconfined_t users, the unconfined processes of the parent and
> > potential labels become unknown to the kernel for a period of time,
> > which ends up labeling the files and processes as unlabeled_t.  When
> > this happens files labeled unlabeled_t can not be accesses by confined
> > process and if a process becomes unlabeled_t it will not be allowed any
> > access on the box, which can cause the process to crash or go into in
> > infinite loop.  If I build a livedvd, I end
> > 
> > setenforce 0
> > livedvd ...
> > load_policy
> > setenforce 1
> > And sometimes I still need to
> > fixfiles restore
> 
> Could it be solved by kernel preventing loading the policy when the
> process which tries that is in the chroot? It seems to me that it
> doesn't make any sense to allow that. Then with enabling creating files
> with a context unknown to the policy the machine could run in enforcing
> mode although the process which does the compose would of course have to
> be unconfined.

How about changes to selinuxfs?  

mount selinuxfs /chroot/selinux -t selinuxfs -o ro

if we are mounted with ro we make everything inside ro so the process
inside the chroot using the chroot version of selinuxfs couldn't screw
the system.

Still doesn't allow laying down invalid types on disk, is that a problem
today?  Although I didn't like the rpm demands for illegal types this
seems like a case where we might want to take that patch...

-Eric


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