Re: SELinux last straw

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On 10/17/07, Les Mikesell <[email protected]> wrote:
> Jacques B. wrote:
> >
> > 3 - How can you effectively troubleshoot an existing problem when a
> > past one was not dealt in such a manner as to ensure that it was
> > corrected
>
> How can you use a system that does not have an effective troubleshooting
> mechanism regardless of how it got into its current state?  The simple
> traditional unix mechanism is something you can easily understand and
> verify.

Ok, now we are arguing for the sake of arguing.  It depends on what
your definition is of a troubleshooting mechanism.  Some would argue
that a listserv is a troubleshooting mechanism.  You post your
problem.  More experienced people provide you advice on what to try or
what to post to help them help you.  This list has served as a
troubleshooting mechanism for many, many people.

But like any other troubleshooting mechanism it will only work if you
follow the steps, in this case those recommended to you by more
experienced people.

>
> >(the intrusion incident being the most notable one but I'm
> > sure others on the list could identify other past issues that were
> > potentially not dealt with adequately based on what was posted in
> > those threads).  The existing problem could be a domino effect from a
> > past problem and may never be properly dealt with until the underlying
> > issue is dealt with.
>
> Regardless, you should have a way to check and fix it, unless what you
> are running is unimportant and you can abandon it.

There are ways to check and patch an intrusion.  But it is beyond the
abilities of most to be able to do so with confidence that there isn't
still a vulnerability left behind as a result of the intrusion.

And to the contrary, if you are running something important then that
is when you will most likely wipe and re-install and/or restore from
backups.  Because if it's important then you cannot risk trying to
clean the system and hope you didn't miss anything.

Re-read the thread where Karl reported the intrusion and you will see
the advice offered (I'm not going to re-post all that here).  Things
that would have to be checked if he opted to not wipe & re-install.
Did he do all that?  All indications from his postings is no, he just
turned off sshd and changed his account password.  Running a rootkit
revealer would be one thing among many others he should have done
(ideally from a bootable Linux CD).  Whereas a wipe guarantees a clean
system (of course you back up your user files and possibly some config
files that you may use as reference when creating the new ones).

If his system is compromised how do we know that there isn't some info
being excluded from the logs?  How do we know that some of the running
processes are not hidden?  How do we know that some open ports are
hidden?  Of course all this thanks to compromised binaries that
purposely exclude that info from the output.  So how can you properly
troubleshoot an issue when you don't know if you can trust what's in
your logs and what's being reported by ls, ps, mount, fdisk, etc...?

You can't honestly suggest that there should be a tool that can check
your entire system for any evidence of intrusion and fix it?  What if
you are using ssh?  web server?  sendmail?  procmail?  mysql? php?
telnet? custom applications that require uncommon ports open? check
the config files for those services and know if there is a problem in
them?  check all the binaries including custom kernel?  Check all the
shell scripts?  Check drive partition and drive mapping? Check all
alias settings?  Check for user accounts that don't belong?  Check the
users' path to ensure it is still right?  Check SELinux settings?
Check iptables settings?  Check hosts.allow, hosts.deny, and hosts
files?  Check the routing file?  check for static arp entries?  and
the list goes on and on and on.  Do you honestly believe that such a
tool could be written?  And I'm sure I've missed lots of other stuff.

If a person keeps using a system that was compromised after having
only turned off sshd and changed the user's password, then that person
likes to live dangerously.  And any problems that arise after this
intrusion becomes potentially more difficult to troubleshoot.  Because
you don't know if you can rely on your binaries, on your logs, on
anything...

That incident was just one other example (along with this one with
SELinux and others from the past) where troubleshooting advice was not
properly followed therefore properly troubleshooting it becomes
impossible.

I've said all I can say on this issue.  After this I'll be engaging in
warmed over arguments which I don't wish to do.

We have taken off on a tangent from the original topic.  We may have
to agree to disagree.  Clearly there are two camps on this issue and
neither is prepare to concede any of their arguments.

I'm moving on...

Jacques B.


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