Re: [v9.1] sepgsql - userspace access vector cache

Hello KaiGai-san,

I've been preparing to review this patch by reading both pgsql-hackers 
history on sepgsql, and also the RHEL 6 guide on SELinux this weekend, 
today I installed GIT HEAD with --with-selinux on Scientific Linux 6, 
developer installation, so far almost everything looking good.

These things should probably be added to the 9.1beta3 documentation branch:

1) the line with for DBNAME in ... do postgres --single etc, lacks a -D 
argument and hence gives the error:
postgres does not know where to find the server configuration file.

2) there is a dependency to objects outside of the postgresql 
installation tree in /etc/selinux/targeted/contexts/sepgsql_contexts, 
and that file has an error that is thrown when contrib/sepgsql is executed:
/etc/selinux/targeted/contexts/sepgsql_contexts:  line 33 has invalid 
object type db_blobs
(same for db_language)
I found your fix for the error on a forum on oss.tresys.com, but IMHO 
either the contrib/sepgsql should mention that the dependency exists and 
it might contain errors for (older) reference policies, or it should 
include a bugfree reference policy for sepgsql to replace the system 
installed refpolicy with (and mention that in the install documentation).

3) sepgsql is currently a bit hard to find in the documentation. 
www.postgresql.org website search doesn't find sepgsql and selinux only 
refers to an old PostgreSQL redhat bug in 2005 on bugzilla.redhat.com. I 
had to manually remember it was a contrib module. Also sepgsql isn't 
linked to at the SECURITY LABEL page. At the moment I'm unsure if I have 
seen all sepgsql related sgml-based documentation.

After fixing the refpolicy I proceeded with the contrib/sepgsql manual, 
with the goal to get something easy done, like create a top secret table 
like 'thisyearsbonusses', and a single user 'boss' and configure sepgsql 
in such a way that only the boss can access the top secret table. I've 
read the the contrib documentation, browsed links on the bottom of the 
page but until now I don't even have a clue how to proceed. Until I do 
so, I don't feel it's appropriate for me to review the avc patch.

Would you be willing to help me getting a bit started? Specific 
questions are:

1) The contrib doc under DML permissions talks about 'db_table:select' 
etc? What are these things? They are not labels since I do not see them 
listed in the output of 'select distinct label from pg_seclabel'.

2) The regression test label.sql introduces labels with types 
sepgsql_trusted_proc_exec_t, sepgsql_ro_table_t. My question is: where 
are these defined? What is their meaning? Can I define my own?

3) In the examples so far I've seen unconfined_u and system_u? Can I 
define my own?

Thanks,
Yeb Havinga


On 2011-07-14 21:46, Kohei KaiGai wrote:
> Sorry, the syscache part was mixed to contrib/sepgsql part
> in my previous post.
> Please see the attached revision.
>
> Although its functionality is enough simple (it just reduces
> number of system-call invocation), its performance
> improvement is obvious.
> So, I hope someone to volunteer to review these patches.
>
> Thanks,
>
> 2011/7/11 Kohei KaiGai<kaigai@kaigai.gr.jp>:
>> I rebased the userspace access vector cache patch to the latest tree.
>>
>> I'll describe the background of this patch because this thread has not been
>> active more than a week.
>> The sepgsql asks in-kernel selinux when it needs to make its access control
>> decison, so it always causes system call invocations.
>> However, access control decision of selinux for a particular pair of security
>> label is consistent as long as its security policy is not reloaded.
>> Thus, it is a good idea to cache access control decisions recently used in
>> userspace.
>> In addition, current GetSecurityLabel() always open pg_seclabel catalog and
>> scan to fetch security label of database objects, although it is a situation we
>> can utilize syscache mechanism.
>>
>> The "uavc-syscache" patch adds a new SECLABELOID syscache.
>> It also redefine pg_seclabel.provide as Name, instead of Text, according to
>> the suggestion from Tom.
>> (To avoid collation conscious datatype)
>>
>> The "uavc-selinux-cache" patch adds cache mechanism of contrib/sepgsql.
>> Its internal api to communicate with selinux (sepgsql_check_perms) was
>> replaced by newer sepgsql_avc_check_perms that checks cached access
>> control decision at first, prior to system call invocations.
>>
>> The result of performance improvement is obvious.
>>
>> * Test 2. time to run 50,000 of SELECT from empty tables
>>   selinux | SECLABELOID syscache
>>   avc   |   without |   with
>> ---------+-----------------------
>>   without | 185.59[s] | 178.38[s]
>> ---------+-----------------------
>>   with    |  23.58[s] |  21.79[s]
>> ---------+-----------------------
>>
>> I strongly hope this patch (and security label support on shared objects) to
>> get unstreamed  in this commit-fest, because it will perform as a basis of
>> other upcoming features.
>> Please volunteer the reviewing!
>>
>> Thanks,
>>
>> 2011/7/2 Kohei KaiGai<kaigai@kaigai.gr.jp>:
>>> The attached patch re-defines pg_seclabel.provider as NameData, instead of Text,
>>> and revert changes of catcache.c about collations; to keep consistency with the
>>> security label support on shared objects.
>>> All the format changes are hidden by (Get|Set)SecurityLabel(), so no
>>> need to change
>>> on the patch to contrib/sepgsql.
>>>
>>> Thanks,
>>>
>>> 2011/6/13 Kohei KaiGai<kaigai@kaigai.gr.jp>:
>>>> 2011/6/13 Robert Haas<robertmhaas@gmail.com>:
>>>>> On Mon, Jun 13, 2011 at 7:51 AM, Kohei KaiGai<kaigai@kaigai.gr.jp>  wrote:
>>>>>> For syscache, length of a typical security label in selinux is
>>>>>> less than 64 bytes. If we assume an entry consume 128bytes
>>>>>> including Oid pairs or pointers, its consumption is 128KBytes
>>>>>> per 1,000 of tables or others.
>>>>>> (Do we have a way to confirm syscache status?)
>>>>> I was thinking you might start a new session, SELECT pg_backendd_pid()
>>>>> to get the PID, use top/ps to get its memory usage; then do a bunch of
>>>>> stuff and see how much it's grown.  The difference between how much it
>>>>> grows with and without the patch is the amount of additional memory
>>>>> the patch consumes.
>>>>>
>>>> I checked memory consumption of the backend with / without
>>>> patches. Because sepgsql_restorecon() tries to reset security
>>>> label of all the schemas, relations, columns and procedures,
>>>> an execution of this function is suitable to emphasize differences
>>>> between two cases in maximum.
>>>>
>>>> The results shows us about 3MB of additional consumption
>>>> in VmRSS, even if it caches all the security label of the objects
>>>> being created in the default (3331 entries).
>>>>
>>>> * without patches before/after sepgsql_restorecon()
>>>>
>>>> VmPeak:   150812 kB ->  170864 kB
>>>> VmSize:   150804 kB ->  154712 kB
>>>> VmLck:         0 kB ->  0kB
>>>> VmHWM:      3800 kB ->  22248 kB
>>>> VmRSS:      3800 kB ->  10620 kB
>>>> VmData:     1940 kB ->    5820 kB
>>>> VmStk:       196 kB ->  196 kB
>>>> VmExe:      5324 kB ->  5324 kB
>>>> VmLib:      2468 kB ->  2468 kB
>>>> VmPTE:       108 kB ->  120 kB
>>>> VmSwap:        0 kB ->  0kB
>>>>
>>>> * with patches before/after sepgsql_restorecon()
>>>> VmPeak:   150816 kB ->  175092 kB
>>>> VmSize:   150808 kB ->  158804 kB
>>>> VmLck:         0 kB ->  0 kB
>>>> VmHWM:      3868 kB ->  25956 kB
>>>> VmRSS:      3868 kB ->  13736 kB
>>>> VmData:     1944 kB ->  9912 kB
>>>> VmStk:       192 kB ->  192 kB
>>>> VmExe:      5324 kB ->  5324 kB
>>>> VmLib:      2472 kB ->  2472 kB
>>>> VmPTE:       100 kB ->  124 kB
>>>> VmSwap:        0 kB ->  0 kB
>>>>
>>>> Thanks,
>>>> --
>>>> KaiGai Kohei<kaigai@kaigai.gr.jp>
>>>>
>>>
>>>
>>> --
>>> KaiGai Kohei<kaigai@kaigai.gr.jp>
>>>
>>
>>
>> --
>> KaiGai Kohei<kaigai@kaigai.gr.jp>
>>
>
>
>
>