On Tue, December 30, 2014 6:41 pm, Ned Slider wrote:
> On 30/12/14 22:07, Valeri Galtsev wrote:
>>
>> I have that vague feeling that what I'm about to say will probably be
>> declared wrong... Still. From the very beginning I do not consider
>> SELinux
>> adding to the security of the system. How can it if it can be turned off
>> on the fly? On the other hand, it adds hundreds of thousands of lines to
>> kernel code which does exactly opposite: deteriorates security by
>> potentially introducing bugs. I discovered at some point that there are
>> other people out there who share this opinion ;-)
>>
>> So, my question is: can someone design attack scenario which would be
>> successful if it were not for SELinux, and which is thwarted by SELinux.
>> Note that the fact that script kiddie just forgot to put as a first line
>>
>> /usr/sbin/setenforce 0
>>
>> doesn't make such example a solid case pro SELinux for me.
>>
>> Thanks a lot for your insight! (Always hoping to learn ;-)
>>
First of all, thanks for your input!
>
> Disabling SELinux requires root privileges at which point most all
> security implimentations are pretty useless.
Not necessarily. There was (or still is?) kernel patch by Purdue
University folks, called LIDS (Linux Intrusion Detection System, if my
memory doesn't fail me). It is slightly different from what the name
suggests. Basically, upon successful boot root is demoted to user nobody.
That's it, you can be root, you can not do anything. Administering such
system is a bitch (you only can make changes off line). But try to break
into this. So, there is at least one implementation. Incidentally, LIDS
was too a candidate into mainstream kernel, but somehow SELinux won, or
maybe the last didn't affect it...
>
> Firewalls add much code to the kernel and can also be "turned off on the
> fly" by any "script kiddie" with root privileges. Should we discount
> them too?
>
> IMHO your arguments are weak with bad examples. The questions you should
> be asking is how effective would SELinux be in preventing an initial
> remote exploit, or preventing an attacker gaining further escalation of
> privileges once they have gained access to the system.
I wouldn't argue on that. My teaches kept repeating there are no stupid
questions, stupid is not to ask questions... To learn what good something
does _is_ helpful, no argument. To ask what can do better than existing
solution may be more productive as encouraging to move farther.
>
> In answer to your question, you will find lots of good real life
> examples in Dans' blog here:
>
> http://danwalsh.livejournal.com/
>
Thanks for the link, I'll do my careful reading, I likely will change my
opinion some... we'll see. My trouble may be: I definitely will compare
what I read with LISD subconsciously ;-(
Thanks again!
Valeri
++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++
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