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..
+ if (file_content == NULL) {
+ ret = ENOMEM;
+ goto done;
+ }