linux-kernel - SMACK netfilter smacklabel socket match

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Date:	Thu, 25 Sep 2008 19:25:53 +0200
From:	Tilman Baumann <tilman.baumann@...lax.com>
To:	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: SMACK netfilter smacklabel socket match

Hi all,

i made some SMACK related patches. I hope this list is the right place 
to post them.

The intention behind this patch is that i needed a way to (firewall) 
match for packets originating from specific processes.
The existing owner match did not work well enough, especially since the 
cmd-owner part is removed.
Then i thought about a way to tag processes and somehow match this tag 
in the firewall.
I recalled that SELinux can do this (SECMARK) but SELinux would have 
been way to complex for what i want. But the idea was born, i just 
needed something more simple.

SMACK seemed to be the right way. So i made a little primitive netfilter 
match to match against the security context of sockets.
SMACK does CIPSO labels, but this was not what i wanted, i wanted to 
label the socket not the packet (on the wire).
This of course only works for packets with a local socket, but this was 
my intention anyway.

This way i can label a process and all it's sockets carry the same label 
which i then can use to match against in the firewall.

The code is pretty much based on cargo cult coding from other netfilter 
matches, especially the owner match (which turned out to be a bad 
reference since it is crapped with tons of compat interfaces).

I have no kernel coding experience whatsoever and little C coding 
history. So i would really like you guys to look over it a bit.

Originally i intended to put this mask in the xtables_match structure.
.hooks = (1 << NF_INET_LOCAL_OUT) | (1 << NF_INET_LOCAL_IN)
But it turned out that i then could not longer put the rule in a chain 
which is called by the OUTPUT chain but only in OUTPUT directly.
I did not investigate much more since i did not really understand this 
part. Allowing the user to add this match wherever he wants to does not 
hurt, if there is no local socket there is no matching.
But maybe this is something that should be changed.

About the Files:
SMACK-netfilter-socket-label-match.patch
is a git patch for the current kernel.

iptables-smacklabel.patch
contains the iptables userspace part (applies to iptables-1.4.1.1)

Regards
  Tilman Baumann
-- 
Tilman Baumann
Software Developer
Collax GmbH . Boetzinger Strasse 60 . 79111 Freiburg . Germany

p: +49 (0) 89-990157-0
f: +49 (0) 89-990157-11

Geschaeftsfuehrer: William K. Hite / Boris Nalbach
AG Muenchen HRB 158898, Ust.-IdNr: DE 814464942

View attachment "SMACK-netfilter-socket-label-match.patch" of type "text/x-patch" (5430 bytes)

View attachment "iptables-smacklabel.patch" of type "text/x-patch" (4462 bytes)