Re: SMACK netfilter smacklabel socket match

[Casey Schaufler]

Tilman Baumann wrote:
> Casey Schaufler wrote:
> > Tilman Baumann wrote:
>
> > > > Hmm. It looks as if your code will do what you're asking it to do.
> > > > Are you going to be happy with the access restrictions that will be
> > > > imposed by Smack?
> > >
> > > I helped myself with rules like this.
> > > _ foo rwx
> > > But i wanted to add some security stuff like selinux for years,
> > > and SMACK seems to be just great.
> > > So i will spend some time making security rules after i got this 
> > > routing
> > > stuff to work. :)
> > I confess that I'm still not completely sure what you're up too,
> > but you might want to look at smackpolyport (it's in the smack-util
> > tarball) and might make your life easier if you want to have a
> > single server (running at foo) that deals with connections from
> > processes with multiple labels.
>
> I'm essentially using this as some kind of iptables owner-match on 
> steroids.
> Owner match allows to filter on the processes uid, gid, and some other 
> process attributes.
> Unfortunately owner match is pretty much useless because of it's 
> limited matching capabilities.
>
> I'm really just abusing the way how security contexts of processes are 
> transfered to all it's sockets.
> This way I can label a process with a specific label which then gets 
> transfered to all of it's sockets.
> With this match I can look at the label via the socket of any packet 
> in  iptables.
> I'm pretty much ignoring the Security aspect of SMACK right now  and 
> just use it as some label that I can stick to processes.

If you really want to be abusive you could replace the smack_access()
function in security/smack/smack_access.c (of all places) with a no-op
returning 0 in all cases.

> What I then to is write iptables OUTPUT chain matches which match for 
> any of these labels and set some connection marks and firewall marks.
> Which I then can use in routing rules to give different routing rules 
> to specific processes. (Like all proxy traffic over a second DSL line)
>
> I know, it's totally crazy. But it seems to work. :)
> I just hope the security part of this all will not break anything. But 
> it does not look like it would right now.

Smack will eventually bite you if you're not careful, but users of
MAC systems wouldn't be surprised by that. I don't think it's crazy,
I think it's a matter of using what's available in novel ways. Don't
hesitate if there's anything I can do to be helpful.

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