On 03/18/2013 12:03 PM, Jakub Hrozek wrote:
>On Fri, Mar 08, 2013 at 09:10:24PM +0100, Michal Židek wrote:
>>>On Mon, Mar 04, 2013 at 04:13:31PM +0100, Michal Židek wrote:
>>>>On 03/04/2013 02:53 PM, Pavel Březina wrote:
>>>>>On 03/01/2013 04:13 PM, Michal Židek wrote:
>>>>>>Patch 1: Right now, we have SELinux procesing split between the
provider
>>>>>>and responder. This patch moves it to provider only. So no
partial
>>>>>>results are sent to responder for further processing, which makes
the
>>>>>>processing steps easier to follow. (Originally the idea was to
move the
>>>>>>processing to the responder, but completely removing the
procesing from
>>>>>>provider and let it just update db turned to be more invasive
than
>>>>>>completely removing the procesing from responder.) If this patch
is
>>>>>>accepted, SELinux policy needs to be modified to allow sssd_be to
write
>>>>>>the selinux login files.
>>>>>>https://fedorahosted.org/sssd/ticket/1743
>>>>>>
>>>
>>>Even though we would have to tailor the SELinux policy, I'm not opposed
>>>to moving the logic to provider. Originally I proposed responder because
>>>I simply wanted all the processing to happen on one place.
>>>
>>>The whole intent of the refactor is to get rid of passing some
>>>information from provider by writing data to sysdb in provider and
>>>reading them in responder. If we get rid of that architectural bug, I'm
>>>fine with any solution.
>>>
>>>FWIW, the other alternative that we were discussing with Michal was to
>>>done the processing in provider and then send the resulting string to
>>>responder via DBus. But it seemed kind of pointless to send the result
>>>with DBus just to avoid moving the write of the file.
>>>
>>>>>>
>>>>>>Patch 2, 3: Reuse cached selinux maps. Patch 2 shows how it is
done with
>>>>>>refresh interval fixed to 120 seconds. Patch 3 adds ipa option
to
>>>>>>configure this interval (I didn't want to merge these patches
for better
>>>>>>readability). Default value is 30 seconds.
>>>>>>https://fedorahosted.org/sssd/ticket/1744
>>>>>>
>>>>>>
>>>>>>Patches are attached.
>>>>>>
>>>>>>Thanks
>>>>>>Michal
>>>>>
>>>>>Hi,
>>>>>switch the order of the second and third patch. So the flow is: add
new
>>>>>option, then use it.
>>>>
>>>>I don't think this is good idea. If the option is present, the logic
>>>>to implement it's effect should be present too. It is also easier to
>>>>test the patches one by one this way (first test the mechanism with
>>>>fixed time interval, then make it configurable and test if interval
>>>>is changing). For now I only changed the 120 seconds in the 2nd
>>>>patch to 5 seconds (so it is not that aggressive).
>>>>>
>>>>>Do we want to use it anyway? Shouldn't be SELinux maps always
updated?
>>>>>
>>>>
>>>>Well, we can still make 0 seconds the default value (or 5 seconds,
>>>>which is used by IPA_HBAC_REFRESH). But selinux maps are not changed
>>>>frequently on ipa side, so having this option is IMO good thing. In
>>>>the new attached patches the default value is changed to 5.
>>>>
>>>>Michal
>>>
>>>Good start, but a nack, sorry.
>>>
>>>I'm seeing a segfaut and valgrind says it's becuase of a
user-after-free
>>>bug:
>>>==28566== Invalid read of size 4
>>>==28566== at 0x5264CFE: sysdb_attrs_get_el_ext (sysdb.c:313)
>>>==28566== by 0x5264EC6: sysdb_attrs_get_string (sysdb.c:356)
>>>==28566== by 0x5280A75: sysdb_store_selinux_entity (sysdb_selinux.c:102)
>>>==28566== by 0x528153D: sysdb_store_selinux_usermap (sysdb_selinux.c:181)
>>>==28566== by 0x122AABE0: ipa_save_user_maps (ipa_selinux_common.c:48)
>>>==28566== by 0x122A55E1: ipa_selinux_handler_done (ipa_selinux.c:260)
>>>==28566== by 0x122A9943: ipa_get_selinux_maps_done (ipa_selinux.c:1149)
>>>==28566== by 0x122AA8DB: ipa_selinux_get_maps_done
(ipa_selinux_maps.c:203)
>>>==28566== by 0x12E2995C: sdap_get_generic_done (sdap_async.c:1558)
>>>==28566== by 0x12E29132: sdap_get_generic_ext_done (sdap_async.c:1449)
>>>==28566== by 0x12E2204B: sdap_process_message (sdap_async.c:366)
>>>==28566== by 0x12E21593: sdap_process_result (sdap_async.c:209)
>>>==28566== Address 0x17e416a0 is 80 bytes inside a block of size 96
free'd
>>>==28566== at 0x4C297A6: free (vg_replace_malloc.c:446)
>>>==28566== by 0x56E2880: _talloc_free_internal (talloc.c:876)
>>>==28566== by 0x122A5BB6: ipa_selinux_process_maps (ipa_selinux.c:355)
>>>==28566== by 0x122A4FFF: ipa_selinux_handler_done (ipa_selinux.c:224)
>>>==28566== by 0x122A9943: ipa_get_selinux_maps_done (ipa_selinux.c:1149)
>>>==28566== by 0x122AA8DB: ipa_selinux_get_maps_done
(ipa_selinux_maps.c:203)
>>>==28566== by 0x12E2995C: sdap_get_generic_done (sdap_async.c:1558)
>>>==28566== by 0x12E29132: sdap_get_generic_ext_done (sdap_async.c:1449)
>>>==28566== by 0x12E2204B: sdap_process_message (sdap_async.c:366)
>>>==28566== by 0x12E21593: sdap_process_result (sdap_async.c:209)
>>>==28566== by 0x12E20BE5: sdap_ldap_next_result (sdap_async.c:159)
>>>==28566== by 0x54DAD3F: tevent_common_loop_timer_delay (in
/usr/lib64/libtevent.so.0.9.17)
>>>
>>>Other tests passed, the use-after-free happens when there is a specific
>>>mapping rule only:
>>>
>>> Rule name: test_user1_specific_host
>>> SELinux User: staff_u:s0-s0:c0.c1023
>>> Enabled: TRUE
>>> Users: tuser3
>>> Hosts:
client.example.com
>>>
>>
>>Fixed.
>>
>>>The code looks OK to me, I would just change two things:
>>>1) Split the function prepare_selinux_file_content() into one that
>>>creates the order array and one that evaluates the matched rules based
>>>on the order. Currently the function does two different tasks and is too
>>>long.
>>>
>>>2) Rename the prepare_selinux_file_content() function so that it is
>>>clear it picks a single rule from a set of rules with same priority
>>>based on the configured order.
>>>
>>
>>I split the function into two new functions (create_order_array,
>>choose_best_seuser) and added some comments.
>>
>>New patches attached.
>>
>>Thanks
>>Michal
>
>Nack,
>
>>+/* Choose best selinux user based on given order and write
>>+ * the user to selinux login file. */
>>+static errno_t choose_best_seuser(struct sysdb_attrs **usermaps,
>>+ struct pam_data *pd,
>>+ char **order_array, int order_count,
>>+ const char *default_user)
>>+{
>>+ TALLOC_CTX *tmp_ctx;
>>+ char *file_content = NULL;
>>+ const char *tmp_str;
>>+ errno_t ret, err;
>>+ int i, j;
>>+
>>+ /* If no maps match, we'll use the default SELinux user from the
>>+ * config */
>>+ file_content = talloc_strdup(tmp_ctx, default_user);
>
>This is clearly wrong, tmp_ctx is never assigned to. The code may work
>only by chance without optimizations becaues tmp_ctx would have been NULL..
>
Good catch. Sorry for that.
>>+ if (file_content == NULL) {
>>+ ret = ENOMEM;
>>+ goto done;
>>+ }
I also changed the behaviour if HAVE_SELINUX_LOGIN_DIR is not defined.
In that case, the processing is skipped and the ipa_selinux_handler just
returns success.
New patches attached.
Thanks
Michal
All my tests passed now. Ack.
Please open a bug in Fedora against selinux-policy-targeted asking them
to allow sssd_be to write to the logins directory. It would be best to
paste them the complete AVC.