05 July 2010

SELinux sanity outline

Rusty Coker mentioned in a recent blog post that he had not found a COLO facility or VM provider that enabled SELinux in its hosts by default. People regularly whine: It's too hard, and I don't need it and disable the SELinux protections. Foo

I call: Bull on the latter As to the former I sent a private email to Rusty, and offered to 'comp' him an instance to break

If anyone knows of a virtual hosting company that runs Xen or KVM virtual machines with SE Linux support then please let me know, I'll write a blog post comparing such companies if there are some.

umm -- I would be embarrased to be a hosting provider which did NOT enable SElinux

Please feel free to set up a 'comp' account at:
at the green arrow. Use the [please do not repeat this] 'Offer Code' of: ...

... I repeated the offer at his blog's comment site

And the question came up today in the #centos IRC channel

13:52 Andro1d> orc_orc: how can i recompile a pp from a te ?
13:53 Andro1d> checkmodule -M -m -o vsftpd.mod vsftpd.te gives a lot of errors :-/
13:53 orc_orc> ehh?
13:53 wolfy> Andro1d:
http://wiki.centos.org/HowTos/SELinux [CentOS wiki]
13:53 orc_orc> make a working dir -- say:
mkdir -p /etc/selinux/targeted/foo
and cd into it
13:54 orc_orc> Gather all the selinux noise:
audit2allow -i /var/log/audit/audit.log* -m local > local.te
13:54 Andro1d> hm, I think I'm missing some types in my .te file
13:54 orc_orc> Note the '*' in that prior line, which reads all log files present
13:54 Andro1d> mom...
13:54 orc_orc> Install the selinux-devel package for the needed Makefile
13:54 Andro1d> don't wanna make a "huge" selinux policy :)
13:54 orc_orc> Then run:
make -f /usr/share/selinux/devel/Makefile
13:55 orc_orc> and apply it:
semodule -i local.pp
13:55 orc_orc> Test again
13:55 Andro1d> yop, mompl
13:55 orc_orc> When happy, be sure to save a versioned copy, because SELinux audit file ageing will cause you to forget what was needed in that merge
13:55 orc_orc> For extra credit, amend:
to retain a sensible universe of back logs
13:56 orc_orc> '4' is wayyy too small

wolfy (a channel regular who offers reliable answers), pointed to the CentOS secondary source answer in the wiki; this post will also pass into our planet as yet another piece of documention and 'cheatsheet'. You saw a self-described RHCE (and he was proud of it coming into the channel today) doing that whimpering for his mommy as I read him the 'riot act'. I don't care in the least that this is new and 'hard' -- growing and learning new tools is part of the Unix culture, always has been, and always will be. That is why I try to make #centos a learning venue rather than a drive-by 'spoon-feeding' shop

How many times do we need to bang the SELinux drum to get your attention?

Yes, you lazy slogs of alleged sysadmins who simply disable SELinux, I am talking to YOU! yep - words are hard to memorize, but this is a basic 'lather, rinse and repeat' cycle which one can solve experimentally if not predictively from knowledge of what is happening. Run a tail -f /var/log/audit/audit.log if you must to see when the rule set needs to be rebuilt

But stop disabling SELinux and stop making excuses