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Re: [RFC][PATCH v2] selinux: change the handling of unknown classes
From: Stephen Smalley <sds_at_nospam>Date: Thu Jan 14 2010 - 20:37:11 GMT
To: Paul Moore <paul.moore@hp.com>
On Thu, 2010-01-14 at 14:48 -0500, Paul Moore wrote:
> On Friday 08 January 2010 12:43:06 pm Stephen Smalley wrote:
> > If allow_unknown==deny, SELinux treats an undefined kernel security
> > class as an error condition rather than as a typical permission denial
> > and thus does not allow permissions on undefined classes even when in
> > permissive mode. Change the SELinux logic so that this case is handled
> > as a typical permission denial, subject to the usual permissive mode
> > and permissive domain handling.
> >
> > Also drop the 'requested' argument from security_compute_av() and
> > helpers as it is a legacy of the original security server interface and
> > is unused.
> >
> > Changes:
> > - Handle permissive domains consistently by moving up the test for a
> > permissive domain.
> > - Make security_compute_av_user() consistent with security_compute_av();
> > the only difference now is that security_compute_av() performs mapping
> > between the kernel-private class and permission indices and the policy
> > values. In the userspace case, this mapping is handled by libselinux.
> >
> > Based in part on a patch by Paul Moore <paul.moore@hp.com>.
> >
> > Reported-by: Andrew Worsley <amworsley@gmail.com>
> > Signed-off-by: Stephen D. Smalley <sds@tycho.nsa.gov>
>
> ...
>
> > -static int security_compute_av_core(u32 ssid,
> > - u32 tsid,
> > - u16 tclass,
> > - u32 requested,
> > - struct av_decision *avd)
> > +static void avd_init(struct av_decision *avd)
> > {
> > - struct context *scontext = NULL, *tcontext = NULL;
> > - int rc = 0;
> > -
> > - scontext = sidtab_search(&sidtab, ssid);
> > - if (!scontext) {
> > - printk(KERN_ERR "SELinux: %s: unrecognized SID %d\n",
> > - __func__, ssid);
> > - return -EINVAL;
> > - }
> > - tcontext = sidtab_search(&sidtab, tsid);
> > - if (!tcontext) {
> > - printk(KERN_ERR "SELinux: %s: unrecognized SID %d\n",
> > - __func__, tsid);
> > - return -EINVAL;
> > - }
> > -
> > - rc = context_struct_compute_av(scontext, tcontext, tclass,
> > - requested, avd);
> > -
> > - /* permissive domain? */
> > - if (ebitmap_get_bit(&policydb.permissive_map, scontext->type))
> > - avd->flags |= AVD_FLAGS_PERMISSIVE;
> > -
> > - return rc;
> > + avd->allowed = 0;
> > + avd->auditallow = 0;
> > + avd->auditdeny = 0xffffffff;
> > + avd->seqno = latest_granting;
> > + avd->flags = 0;
> > }
> >
> > +
> > /**
> > * security_compute_av - Compute access vector decisions.
> > * @ssid: source security identifier
> > * @tsid: target security identifier
> > * @tclass: target security class
> > - * @requested: requested permissions
> > * @avd: access vector decisions
> > *
> > * Compute a set of access vector decisions based on the
> > * SID pair (@ssid, @tsid) for the permissions in @tclass.
> > - * Return -%EINVAL if any of the parameters are invalid or %0
> > - * if the access vector decisions were computed successfully.
> > */
> > -int security_compute_av(u32 ssid,
> > - u32 tsid,
> > - u16 orig_tclass,
> > - u32 orig_requested,
> > - struct av_decision *avd)
> > +void security_compute_av(u32 ssid,
> > + u32 tsid,
> > + u16 orig_tclass,
> > + struct av_decision *avd)
> > {
> > u16 tclass;
> > - u32 requested;
> > - int rc;
> > + struct context *scontext = NULL, *tcontext = NULL;
> >
> > + avd_init(avd);
> > read_lock(&policy_rwlock);
>
> The only thing that is jumping out at me right now is that you are calling
> avd_init() outside the policy lock and 'latest_granting' appears to be
> protected by the lock. Maybe not a huge deal since it is just a scalar but
> thought I would mention it; the same applies below in
> security_compute_av_user().
Good catch, I'll move it inside the lock. -- Stephen Smalley National Security Agency -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@tycho.nsa.gov with the words "unsubscribe selinux" without quotes as the message.