Regarding retrieving user group membership using wbinfo.

[Hemanth Thummala]

Also I would like to now if there is any "net" command that can be used to
request the same information mentioned as part of this specific DCE-RPC
call.

Thanks,
Hemanth.


On Thu, Jun 5, 2014 at 7:56 PM, Hemanth Thummala <hemanth.thummala at gmail.com
> wrote:

> Yes Volker. You are correct. netsamlogon_cache is getting updated on
> successful user login. And from the code I could see that a DCE-RPC call is
> made to get the group membership list and update netsamlogon_cache.tdb file.
>
> When I remove the cache entries related to this specific user(SID),
> listing is proper. Based on this I suspect that netsamlogon_cache is
> updated with incorrect data using the DCE-RPC response. I could not get
> what exactly the request and response contains as they are encrypted. But
> from code, it is rpccli_netlogon_sam_network_logon_ex() routine which is
> responsible for retrieving the info3 structure which includes the group
> membership information.
>
> And yes I forgot to mention that it is Samba 3.6.12+ stack that we are
> using here. Thanks for that Richard.
>
> Thanks,
> Hemanth.
>
>
>
>
> On Thu, Jun 5, 2014 at 7:44 PM, Volker Lendecke <Volker.Lendecke at sernet.de
> > wrote:
>
>> On Thu, Jun 05, 2014 at 06:43:59AM -0700, Richard Sharpe wrote:
>> > On Thu, Jun 5, 2014 at 3:41 AM, Hemanth Thummala
>> > <hemanth.thummala at gmail.com> wrote:
>> > > Hi,
>> > >
>> > > We are experiencing a strange problem with one of our customer setups
>> > > relating to user group memberships. Customer has multi-site AD setup
>> in
>> > > which our boxes are deployed in multiple sites.
>> > > In one particular site, we are seeing a difference in group membership
>> > > details with a user(wbinfo -r <user>). Able to retrieve only few
>> groups
>> > > than expected. Whereas other sites we are able to get the correct
>> results.
>> >
>> > A vital piece of info is that this is Samba 3.6.12+ you are talking
>> > about. The same problem might not exist in the latest sources.
>> >
>> > > Initially we thought its AD replication problem, but even after
>> > > forcing(blocked the traffic with site-local DC) our boxes to contact
>> PDC
>> > > did not help.
>> > >
>> > > Then I have removed the cache entries for this user from both
>> > > winbindd_cache.tdb and netsamlogon_cache.tdb. Then it started showing
>> the
>> > > correct entries. But after 5 to 6 hours this problem reappears. After
>> > > cleaning up cache entries in both tdb files, problem will go away.
>> > >
>> > > From the code walk-through and debug level logs this is what I
>> understood.
>> > > 1. Winbindd receives request GETGROUPS from the client.
>> > > 2. Initially it will lookup winbindd_cache.tdb and see if there is a
>> > > "UG/sid" entry for the user. it will return the information in cache
>> if
>> > > entry is not expired (I think expiry time is 5 mins).
>> > > 3. If the entry in winbindd_cache.tdb is expired, then
>> lookup_usergroups()
>> > > request will be made.
>> > > 4. Before contacting the DC to fetch the groups, will search for the
>> user
>> > > SID in netsamlogon_cache.tdb. If the entry is found, that information
>> will
>> > > be returned.
>> > > 5. If the entry is not found in netsamlogon_cache.tdb, then DCE-RPC
>> request
>> > > will be made using cached kerberos credentials.
>> > >
>> > > I came to know that there is no expiry time for the cached entries in
>> > > netsamlogon_cache.tdb. I have seen the expiry time calculation is
>> commented
>> > > out in netsamlogon_cache_get().
>> > >
>> > > But I am not really sure why the cache entry in
>> netsamlogon_cache.tdb() is
>> > > updated with wrong data due to which the problem is reappearing.
>>
>> If all goes well then the netsamlogon_cache is only written
>> after a successful login. This can happen when a client
>> authenticates via netlogon or presents a valid kerberos
>> ticket with a PAC. In the bad case, can you find out where
>> the bad information comes from? Is it really the netsamlogon
>> cache that is faulty?
>>
>> With best regards,
>>
>> Volker Lendecke
>>
>> --
>> SerNet GmbH, Bahnhofsallee 1b, 37081 Göttingen
>> phone: +49-551-370000-0, fax: +49-551-370000-9
>> AG Göttingen, HRB 2816, GF: Dr. Johannes Loxen
>> http://www.sernet.de, mailto:kontakt at sernet.de
>>
>
>