Re: [PATCH] selinux: deprecated fs ocon

[Paul Moore]

On Thu, May 18, 2023 at 1:56 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
> On May 11, 2023 =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@xxxxxxxxxxxxxx> wrote:
> >
> > The object context type `fs`, not to be confused with the well used
> > object context type `fscon`, was introduced in the initial git commit
> > 1da177e4c3f4 ("Linux-2.6.12-rc2") but never actually used since.
> >
> > The paper "A Security Policy Configuration for the Security-Enhanced
> > Linux" [1] mentions it under `7.2 File System Contexts` but also states:
> >
> >     Currently, this configuration is unused.
> >
> > The policy statement defining such object contexts is `fscon`, e.g.:
> >
> >     fscon 2 3 gen_context(system_u:object_r:conA_t,s0) gen_context(system_u:object_r:conB_t,s0)
> >
> > It is not documented at selinuxproject.org or in the SELinux notebook
> > and not supported by the Reference Policy buildsystem - the statement is
> > not properly sorted - and thus not used in the Reference or Fedora
> > Policy.
> >
> > Print a warning message at policy load for each such object context:
> >
> >     SELinux:  void and deprecated fs ocon 02:03
> >
> > This topic was initially highlighted by Nicolas Iooss [2].
> >
> > [1]: https://media.defense.gov/2021/Jul/29/2002815735/-1/-1/0/SELINUX-SECURITY-POLICY-CONFIGURATION-REPORT.PDF
> > [2]: https://lore.kernel.org/selinux/CAJfZ7=mP2eJaq2BfO3y0VnwUJaY2cS2p=HZMN71z1pKjzaT0Eg@xxxxxxxxxxxxxx/
> >
> > Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> > ---
> >  security/selinux/ss/policydb.c | 4 ++++
> >  security/selinux/ss/policydb.h | 2 +-
> >  2 files changed, 5 insertions(+), 1 deletion(-)
>
> Thanks, this is a nice catch, although some minor suggestions below ...
>
> > diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
> > index 97c0074f9312..31b08b34c722 100644
> > --- a/security/selinux/ss/policydb.c
> > +++ b/security/selinux/ss/policydb.c
> > @@ -2257,6 +2257,10 @@ static int ocontext_read(struct policydb *p, const struct policydb_compat_info *
> >                               if (rc)
> >                                       goto out;
> >
> > +                             if (i == OCON_FS)
> > +                                     pr_warn("SELinux:  void and deprecated fs ocon %s\n",
> > +                                             c->u.name);
>
> Instead of having to check if 'i == OCON_FS', why not simply put the
> pr_warn() call up in the OCON_FS case block on line ~2249 and let it
> continue to fallthrough to the OCON_NETIF block?

Bah, nevermind, you need to leave it here because of the 'c->u.name'
in the pr_warn().  If you're okay with me adjusting the deprecation
comment (below) during the merge I'll can merge this now ... ?

> >                               rc = context_read_and_validate(&c->context[0], p, fp);
> >                               if (rc)
> >                                       goto out;
> > diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
> > index ffc4e7bad205..39cd6222e1a8 100644
> > --- a/security/selinux/ss/policydb.h
> > +++ b/security/selinux/ss/policydb.h
> > @@ -225,7 +225,7 @@ struct genfs {
> >
> >  /* object context array indices */
> >  #define OCON_ISID    0 /* initial SIDs */
> > -#define OCON_FS              1 /* unlabeled file systems */
> > +#define OCON_FS              1 /* unlabeled file systems (deprecated in 6.5) */
>
> Since you are likely re-spinning this (see above), I would just leave
> it as "(deprecated)"; those that want to know where it was deprecated
> can always check the git log/tags.
>
> >  #define OCON_PORT    2 /* TCP and UDP port numbers */
> >  #define OCON_NETIF   3 /* network interfaces */
> >  #define OCON_NODE    4 /* nodes */
> > --
> > 2.40.1

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