Regarding retrieving user group membership using wbinfo.

[Hemanth Thummala]

Infact "wbinfo -a" updating the incorrect cache entry in
netlogon_cache.tdb. I did enable the winbindd log to 10. But couldn't see
any log dumping this request and response. Also I did not any code that is
dumping the details at debug level 10.

Thanks,
Hemanth.


On Thu, Jun 5, 2014 at 8:28 PM, Volker Lendecke <Volker.Lendecke at sernet.de>
wrote:

> Hi!
>
> Can you fix the entry by a successful wbinfo -a?
>
> A winbind debug level 10 log will show what winbind puts
> into the netsamlogon cache. You can bump up the debuglevel
> temporarily with
>
> smbcontrol winbindd debug 10
>
> Yes, it's the logon_ex routine that will update the info3
> structure. In the debug level 10 output you will see it
> decrypted and unmarshalled.
>
> With best regards,
>
> Volker Lendecke
>
> On Thu, Jun 05, 2014 at 07:56:33PM +0530, Hemanth Thummala 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
> > >
>
> --
> 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
>