Re: [PATCH] Dynamic port labeling V2

[Paul Moore]

On Friday 18 December 2009 12:33:24 am Kyle Moffett wrote:
> On Fri, Dec 4, 2009 at 11:03, Joshua Brindle <method@xxxxxxxxxxxxxxx> wrote:
> > Paul Nuzzi wrote:
> >> On Thu, 2009-12-03 at 14:31 -0500, Joshua Brindle wrote:
> >>> Paul Nuzzi wrote:
> >>>> Added a mechanism to add/delete/update port labels with an interface
> >>>> in the selinuxfs filesystem.  This will give administrators the
> >>>> ability to update port labels faster than reloading the entire policy
> >>>> with semanage.  The administrator will also need less privilege since
> >>>> they don't have to be authorized to reload the full policy.
> >>>>
> >>>> A listing of all port labels will be output if the file
> >>>> /selinux/portcon is read.  Labels could be added or deleted with the
> >>>> following commands
> >>>>
> >>>> echo -n "del system_u:object_r:ssh_port_t:s0 6 22 22">
> >>>> /selinux/portcon echo -n "add system_u:object_r:telnetd_port_t:s0 6 22
> >>>> 22"> /selinux/portcon
> >>>
> >>> Aside from the conversation Dave and Casey are having I still think
> >>> this isn't quite right. First, while you can atomically change a single
> >>> port label with the add command above you can't atomically change
> >>> multiple entries, which I think is completely necessary (you don't want
> >>> to have strange labeling states when changing a set of ports to a new
> >>> label.
> >>
> >> Can you think of a situation where we would need to atomically change
> >> multiple entries?  I envisioned a sys admin stopping their application
> >> or server, relabeling the ports and then restarting them.  Maybe there
> >> is a specific case you know about that I've overlooked?
> >
> > Maybe not, and it isn't like labeling filesystems is atomic so maybe I'm
> > out in left field here.
> >
> > [...]
> >
> > I actually was thinking about resizing a range. You just put the system
> > in a strange state by having to remove alot of labels and then readd
> > them. It seems most reliable to add the entire set of portcons every time
> > (using some file on disk and a text parser to parse them in to an
> > ocontext like struct then feeding it in), that way the ordering is always
> > exactly like it is in the file and there is a persistent file on disk
> > that can be loaded at policy load time.
> >
> > Users could literally do a setportcon -e to pop up an editor with all the
> > portcons and reorder, modify, re-range, etc and it would all take effect
> > at once.
> 
> Hrm, wow.... this seems like a whole lot of re-engineering of work
> that has already been done and works well, specifically iptables.
> 
> The iptables code already allows almost any combination of access
> rules, with conditionals, nested filters, ranges, etc... and it has a
> design that allows atomic replacement of the entire firewall ruleset.
> 
> Furthermore, using tools like Shorewall (http://shorewall.net), I can
> customize exactly what my filtering and forwarding rules are using
> simple human-readable configuration files.  Shorewall even generates
> an iptables restore file so I either get the old set of firewall rules
> or the new set, nothing halfway in-between.
> 
> I know that SELinux labeling is already partially supported through
> the security table... can't we figure out some way to extend that to
> this port-based labeling as well?

The SELinux packet labeling that is done via iptables, Secmark, is different 
from the SELinux port labeling that is done via policy/semanage.  The key here 
is that iptables is used by SELinux to label packets, not ports.  This 
approach seems to be consistent with everything I know about iptables, but if 
I'm missing something please let me know.

> Another thing that would be nice is to be able to apply some amount of
> discrete access control to firewall rule updates, so that a "network admin"
> could adjust most firewall rules, while the "security admin" would be
> responsible for packet and network interface labeling.

This is something that has been discussed in the past, although perhaps in 
person and not on any mailing lists, but no one has done any serious work on 
it as far as I know.  As usual, we're always open to patches :)

> Putting my various admin hats on, what I would *LOVE* to have from a
> security standpoint would be something along the lines of
> setroubleshoot, but designed to handle audits from many computer
> systems and to allow communication between people with different
> security roles.  Here's an example use-case:
> 
> So say a web developer is preparing to roll out a big application
> install, and needs to add a new HTTP listen port (say, 8083).  She
> tells apache to listen on that port and gets a "permission denied",
> along with a notification of some kind that her action has triggered a
> security warning.  As a result, she goes ahead and fills out a
> "network security" change request form, and then puts the ticket
> number into the SETroubleshoot interface tagged to the security
> warning.

I'm not really a SETroubleshoot or userspace guru, but I believe at least this 
part should be possible today ... although the change management 
infrastructure is left as an exercise for the reader :)
 
> A few minutes later, the network security guy sits down and opens up
> his audit window and sees the warning that his friendly web developer
> triggered.  He checks the trouble ticket and updates the HTTP
> type-enforcement rules to allow that port as well, then sends off a
> notice to the web developer that everything is OK.

I'm pretty sure some of the audit dispatcher/plugin stuff allows for sending 
security events to a central repository for reporting, analysis and other 
nefarious purposes.

> The web developer then works with his users to beta-test the web
> application and discovers that his software is unable to talk to one
> of its database backends on another server because that database has
> "sensitive financial" data and requires labelled IPsec connections to
> access it.  Those audit messages (even from the same server) then go
> to a separate "data security" person, who must himself add the new
> labelling rules to allow that software access to some financial data.

Sort of a "wash, rinse, repeat" of the previous issues.

> I could almost build this system today with a bunch of custom
> userspace firewall management and audit-log filtering software... but
> I have no real way of actually restricting my "data security" person
> from fiddling with the HTTP port labelling, nor can I prevent my basic
> network security guy from changing my fancy labelled IPsec rules.

I'll let the policy guys address this last bit ...

-- 
paul moore
linux @ hp
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