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Re: Firewall rules using SELinux context (Was Re: RFE: FireKit)



'Content-Type: format=flowed' would be really nice, as opposed to the 'one line per paragraph' you sent...

Casey Dahlin wrote:
A couple of mentions of SELinux have cropped up in the FireKit thread, which got me thinking about the Firewall and SELinux and ways
in which they are similar. I had the following thought:

SELinux already has a lot of policy information from which we might like to determine whether ports should be open to a particular
program. The simplest mechanism I can see for doing that is to allow
SELinux context to be referenced in the firewall rules. This prevents
either system from having to be grotesquely modified.

An example rule might look like this:

-A INPUT -Z apache_t -j ACCEPT

Here we tell the firewall to allow incoming traffic that will be
intercepted in userspace by a process in the apache_t context.

My question is, can this even work? There is a reason I suggested that on the /INPUT/ side, iptables have no more smarts than 'is there a socket that will accept this packet'. (Then use SELinux to allow/prevent those sockets from being opened in the first place.)

I like the idea for the OUTPUT chain, however.

This does break in at least one way from traditional SELinux policy: something external to SELinux is interpreting the meaning of the context. The firewall rules can change while the actual SELinux
policy stays put. I don't know how serious a problem that is (if it
is one).

I think this makes sense. You may want the rules for $DAEMON to change based on network connectivity, or even intangible parameters (e.g. "I just called IT and they asked for ssh access, I want to enable it but only for the next five minutes"). This seems easier to express in iptables than changing the SELinux context to cope with such events. Especially since the SELinux context in this case really becomes more of a tag than a rule set; the user determines the rules.

That said, I'm not familiar with SECMARK, so it's hard to say if it can accomplish the same things. (It does, however, seem to be backwards w.r.t. how you want rules to be defined. Can I use SECMARK to e.g. allow Konqueror to browse YouTube, but block Firefox?)

--
Matthew
Please do not quote my e-mail address unobfuscated in message bodies.
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