[PATCH] passdb: handle UPN in lookup_name correctly

[Rowland Penny]

On Fri, 15 Feb 2019 18:07:40 +0100
Ralph Wuerthner <ralphw at de.ibm.com> wrote:

> On 15.02.19 17:23, Rowland Penny wrote:
> > On Fri, 15 Feb 2019 17:06:04 +0100
> > Ralph Wuerthner via samba-technical
> > <samba-technical at lists.samba.org> wrote:
> > 
> >> On 13.02.19 16:18, Andreas Schneider wrote:
> >>> On Tuesday, February 12, 2019 1:38:09 PM CET Ralph Wuerthner via
> >>> samba- technical wrote:
> >>>> Hi Andreas!
> >>>>
> >>>> On 12.02.19 10:39, Andreas Schneider wrote:
> >>>>> On Monday, February 11, 2019 5:39:33 PM CET Ralph Wuerthner
> >>>>> wrote:
> >>>>>> Hi Andreas!
> >>>>>>
> >>>>>> On 11.02.19 16:07, Andreas Schneider wrote:
> >>>>>>> Hi Ralph,
> >>>>>>>
> >>>>>>>> Please see attached patchset:
> >>>>>>>> The fix for Samba bugzilla 13312 (commit 1775ac8aa4) caused a
> >>>>>>>> regression
> >>>>>>>> when looking up names in UPN notation: Because
> >>>>>>>> winbind_lookup_name is called with lp_workgroup as domain
> >>>>>>>> name the lookup is now failing and the SID for an unmapped
> >>>>>>>> Unix user is returned by lookup_name. Fixed by calling
> >>>>>>>> winbind_lookup_name with an empty domain name in case the
> >>>>>>>> name is in UPN notation.
> >>>>>>>>
> >>>>>>>> The patchset already passed a CI run:
> >>>>>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__gitlab.com_samba-2Dteam_devel_samba_pipelines_46689980&d=DwICAg&c=jf_iaSHvJObTbx-siA1ZOg&r=91G8BCIr_Gua7QkxI_O-dlz8T-mXwIVnjFb7EjeIK7M&m=cE08ROyNiXvMje49eaTVj5qguLqqeNc9L0waXJZlLU8&s=HzsOgBRt8y3O1Jco7WX-FCBZUY8W7L24Vwu5jmYeGP8&e=
> >>>>>>>
> >>>>>>> Thanks for your contribution!
> >>>>>>>
> >>>>>>> Please use DGB_DEBUG() instead of DEBUG(10, ...)
> >>>>>>>
> >>>>>>> In lookup_upn() use a helper variable 'bool ok'. And check
> >>>>>>> talloc_strdup()
> >>>>>>> for NULL.
> >>>>>>
> >>>>>> Thanks for your feedback! I prepared a new version of the
> >>>>>> patchset with the following changes:
> >>>>>> - using a helper variable in lookup_upn()
> >>>>>> - use DBG_DEBUG() instead of DEBUG(10, ...)
> >>>>>>
> >>>>>> I didn't add a NULL check for talloc_strdup() because there is
> >>>>>> already a NULL check right after the ok: label. This check is
> >>>>>> used by other sequence steps in lookup_name() too.
> >>>>>
> >>>>> But then the function would need documentation that the caller
> >>>>> is responsible for the NULL check.
> >>>>>
> >>>>> I think this is strange code and we should do the check in place
> >>>>> and not defer it to later.
> >>>>
> >>>> Ahh, I got your point. I thought you were referring to the
> >>>> talloc_strdup() call from patch #2 in lookup_name(), instead you
> >>>> are referring to the talloc_strdup() call in lookup_upn(). You
> >>>> are right, there should be a check in lookup_upn(). I didn't pay
> >>>> much attention to this because patch #3 is elimination the
> >>>> talloc_strdup() call in lookup_upn(). Please see the attached
> >>>> patchset with the missing check (though it will be gone after
> >>>> applying patch #3).
> >>>
> >>> This looks good. Now we need tests which verify this :-)
> >>
> >> This will be the harder part...
> >>
> >> I tried to recreate this in the ad_member test environment but
> >> without success. Samba's AD DC seems to behave slightly different
> >> than a Windows AD server. With or without my patchset I get the
> >> same results:
> >>
> >> ./bin/rpcclient 127.0.0.29 -U% -c 'lookupnames "alice at ADDOMAIN"'
> >> alice at ADDOMAIN S-1-5-21-2858285458-1632643436-2480850723-1106
> >> (User: 1)
> >>
> >> But when doing this on my test system (without my patchset) I get a
> >> Unix SID when querying a Samba AD member:
> >>
> >> rpcclient localhost -U'virtual1\administrator%*****' -c
> >> 'lookupnames "testuser1 at virtual1.com"'
> >> testuser1 at virtual1.com S-1-22-1-12001118 (User: 1)
> >>
> >> and the expected SID when querying the AD server directly:
> >>
> >> rpcclient 10.0.100.8 -U'virtual1\administrator%*****' -c
> >> 'lookupnames "testuser1 at virtual1.com"'
> >> testuser1 at virtual1.com
> >> S-1-5-21-3478218634-1770281059-659661689-1118 (User: 1)
> >>
> >> Do we have to change the behavior of the Samba AD DC or what's the
> >> way forward here?
> >>
> >>
> > 
> > Could there be something wrong with your test system:
> > 
> > rowland at devstation:~$ rpcclient localhost
> > -U'samdom\administrator%xxxxxxxxxx' -c 'lookupnames
> > "rowland at samdom.example.com"' rowland at samdom.example.com
> > S-1-5-21-1768301897-3342589593-1064908849-1107 (User: 1)
> > rowland at devstation:~$ rpcclient 192.168.0.6
> > -U'samdom\administrator%xxxxxxxxxx' -c 'lookupnames
> > "rowland at samdom.example.com"' rowland at samdom.example.com
> > S-1-5-21-1768301897-3342589593-1064908849-1107 (User: 1)
> > 
> > devstation is a Unix domain member
> > 192.168.0.6 is a Samba AD DC
> 
> Maybe I was not precises enough above: when querying a Samba domain 
> member joined to a Samba AD DC everything is fine. But when querying
> a Samba domain member joined to a Windows AD server I get a Unix SID.
> 

I have been doing further testing (just out of curiosity) with a 2012R2
DC and a Samba Unix domain member:

root at fileserver:~# rpcclient 192.168.0.43 -U'example\administrator%xxxxxxxxxx' -c 'lookupnames "rowland at example.com"'
rowland at example.com S-1-5-21-1739413417-3060112075-1959733387-1104 (User: 1)

fileserver is the Samba Unix domain member
192.168.0.43 is the 2012R2 DC

So I repeat, could there be something wrong with the test or the Unix
domain member ?

Rowland