Re: [PATCH] SELinux: Use unknown perm handling to handle unknown netlink msg types

[Paul Moore <paul.moore@hp.com>]

On Friday 07 November 2008 11:07:41 am Eric Paris wrote:
> On Wed, 2008-11-05 at 11:38 -0500, Paul Moore wrote:
> > On Wednesday 05 November 2008 9:34:42 am Eric Paris wrote:
> > > Currently when SELinux has not been updated to handle a netlink
> > > message type the operation is denied with EINVAL.  This patch
> > > will leave the audit/warning message so things get fixed but if
> > > policy chose to allow unknowns this will allow the netlink
> > > operation.
> > >
> > > Signed-off-by: Eric Paris <eparis@redhat.com>
> > > ---
> > >
> > >  security/selinux/hooks.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > >
> > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > > index f85597a..c6f8f3e 100644
> > > --- a/security/selinux/hooks.c
> > > +++ b/security/selinux/hooks.c
> > > @@ -4387,7 +4387,7 @@ static int selinux_nlmsg_perm(struct sock
> > > *sk, struct sk_buff *skb) "SELinux:  unrecognized netlink
> > > message" " type=%hu for sclass=%hu\n",
> > >  				  nlh->nlmsg_type, isec->sclass);
> > > -			if (!selinux_enforcing)
> > > +			if (!selinux_enforcing || security_get_allow_unknown())
> > >  				err = 0;
> > >  		}
> >
> > What about moving the security_get_allow_unknown() call to the
> > default switch clause of selinux_nlmsg_lookup()?  Something like
> > this:
> >
> >         /* No messaging from userspace, or class unknown/unhandled
> > */ default:
> >                 if (!security_get_allow_unknown())
> > 			err = -ENOENT;
> >                 break;
> >
> > This seems like a more natural fit to me (although maybe the audit
> > message should be moved to selinux_nlmsg_lookup() too?) and it has
> > the benefit of still checking the socket permissions via
> > socket_has_perm() in the event that the netlink message is unknown.
>
> We already just blindly allow the case where a new/unknown sclass is
> used which is what this part of the switch statement hits.  I wanted
> to get the case where a known class has a new mesg type (aka
> nlmsg_perm returns -EINVAL)

Fair enough, I thought you were trying to solve a different problem.

-- 
paul moore
linux @ hp

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