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SubjectRe: [PATCH BUGFIX -rc4] Smack: Respect 'unlabeled' netlabel mode
Hi Casey,

On Fri, May 30, 2008 at 04:10:37PM -0700, Casey Schaufler wrote:
> To date the behavior of a Smack system running with nltype
> unlabeled has been carefully undefined.

In the early days (before the 'Smack: unlabeled outgoing ambient packets'
patch - 4bc87e62), I used '$ echo unlabeled > /smack/nltype' in my startup
scripts to avoid sending cipso-affected packets. When I upgraded this
machine's kernel, I faced the -EPERM problem mentiond above.

> The way you're defining
> it will result in a system in which only processes running with
> the ambient label will be able to use sockets, unless I'm reading
> the code incorrectly.

I've tried to see the relation but failed, any help?

I'm noticing the opposite though, without defining nltype=unlabeled,
we're forcing every smack-labeled process to send cipso-affected
packets (and usually no machine around understands cipso).

_Assuming_ the concept is accepted, depending on the ambient label
may actually lead to a race condition though:

- A packet is set with the ambient label domain
- Ambient label changes
- old ambient-label netlabel domain is deleted
- new ambient-label is set
- new ambient-label netlabel domain is created
- call netlabel_sock_setattr(), uses the old ambient label, leads
to the -EPERM problem.
-- Rare, but can happen

There are two possible solutions in my mind:

- Using a predefined netlabel domain to denote to unlabeled packets.
Defect: May collide with a user chosen label and used to break security.
Solution: Use a domain name that can't become a label (Hackery ?)

- I've tried first to use what was done before the 'Smack: unlabeled outgoing
ambient packets' patch, which honored nltype=unlabeled, but ignored netlabel

int rc = 0;
if (secattr.flags != NETLBL_SECATTR_NONE)
rc = netlbl_sock_setattr(sk, &secattr);
return rc

Paul, would this be right from a netlabel perspective ?

Ahmed S. Darwish

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