Re: [PATCH] LSM hooks for audit

Thanks.  Too bad, having the checks on the receiving side would have
been nice.

I will see if I can come up with a clean solution through dummy.c on the
netlink_send side before I leave this weekend.  The use of the
CAP_SYS_ADMIN checks on the receiving side in the mainline code should
be fixed...

-serge

On Wed, 2004-09-15 at 14:39, Stephen Smalley wrote:
> On Wed, 2004-09-15 at 15:31, Serge E. Hallyn wrote:
> > > Sorry, I wasn't thinking in my initial response.  These operations are
> > > exported via netlink, which is async, right?  Hence, permission checks
> > 
> > I was wondering about that.  Based on the original code I assumed that
> > it was synchronous.
> > 
> > Taking a second look at net/netlink, I guess not.
> > 
> > Is there any reason why we can't find the task belonging to
> > NETLINK_CREDS(skb)->pid and send that along to the security_* hooks?
> 
> Race conditions.  Untrusted sender fires off a netlink message to set
> some value, then immediately exec's a privilege-changing program so that
> when the receiver evaluates the task's credentials, the task is running
> privileged.  I think you either have to do all of your mediation at
> netlink_send time (as in the SELinux code) or get a security field into
> netlink_skb_parms (but then you have lifecycle management issues, which
> seems difficult to separate from having a general security field in the
> sk_buff itself).
-- 
=======================================================
Serge Hallyn
Security Software Engineer, IBM Linux Technology Center
serue@xxxxxxxxxx