Help with standalone samba SID-uid mapping

[Chris Roehrig]

On Mon Jan 17 2022, at 4:04 AM, Corinna Vinschen <corinna-cygwin@cygwin.com> wrote:

> On Jan 14 11:57, Chris Roehrig wrote:
>> On Fri Jan 14 2022, at 2:04 AM, Corinna Vinschen <corinna-cygwin@cygwin.com> wrote:
>>> These look like your standard Windows SIDs, so they are your SIDs for
>>> users cristina and croehrig on Windows.  They should show up as such in
>>> ls -l output, unless the SID is actuall wrong, e. g., they map to your
>>> accounts on another machine or something like that.
>> 
>> No those are the SIDs supplied by the Samba server (see below for my local Windows SIDs).   Here they are directly on the Linux machine:
>> housesrv[11]% smbcacls --numeric //housesrv/Users croehrig
>> Enter WORKGROUP\croehrig's password: 
>> REVISION:1
>> CONTROL:0x9004
>> OWNER:S-1-5-21-751087815-2087572193-42305691-1000
>> GROUP:S-1-22-2-601
>> ACL:S-1-5-21-751087815-2087572193-42305691-1000:0/0x0/0x001f01ff
>> ACL:S-1-22-2-601:0/0x0/0x001200a9
>> ACL:S-1-1-0:0/0x0/0x001200a9
>> 
>> (I think that Samba now uses a more complex IDMAP algorithm than when
>> the Cygwin document above was written and now provides a full domain
>> component to its SIDs.)
> 
> That may be so, but in my installation, Samba reports the Unix User ID
> as owner, i. e.
> 
>  $ icacls \\\\server\\corinna\\foo
>  \\server\corinna\foo S-1-22-1-500:(R,W,D,WDAC,WO)
>                       S-1-22-2-11125:(R)
>                       Everyone:(R)
> 
> and that's with Samba 4.15.3.  I'm doing the mapping via the AD
> uidNumber and gidNumber fields.  I'm using this setup for so long that I
> don't remember if I ever saw a "normal", Windows-like SID for the user
> returned by Samba.  I never ran winbindd, up until Samba 4.15.3, which
> was the first one forcing me to do so when using AD support.

I'm no Samba expert, but maybe your /var/lib/samba/private/secrets.tdb file predates that IDMAP change...?
What does 'net getdomainsid' say on your samba host?
housesrv[2]% sudo net getdomainsid
SID for local machine HOUSESRV is: S-1-5-21-751087815-2087572193-42305691
SID for domain WORKGROUP is: S-1-5-21-..........


> 
>> I just added those SIDs to  /etc/passwd and /etc/groups (double
>> entries now) and it now works for the user, but (oddly) not the group:
>> 
>> tyto[6]% ls -l //housesrv/Users/				## NB: this is a UNC path to the samba share
>> total 0
>> drwxr-xr-x 1 cristina Unix_Group+603 0 Jan 12 16:06 cristina
>> drwxr-xr-x 1 croehrig Unix_Group+601 0 Jan 14 09:18 croehrig
>> [...]
>> tyto[10]% cat /etc/group
>> croehrig:S-1-22-2-601:601:
>> cristina:S-1-22-2-603:603:
>> croehrig:S-1-5-21-1290748074-662758565-4273641972-1006:601:
>> cristina:S-1-5-21-1290748074-662758565-4273641972-1008:603:
> 
> Hmm, that's weird.  I just tried this myself.  First I created a stock
> /etc/group file with all local and AD accounts.  Next I changed
> /etc/nsswitch.conf:
> 
>  - group: db
>  + group: files
> 
> Exit/restart Cygwin. `ls -l' now prints
> 
>  -rw-r--r-- 1 corinna Unknown+Group 13342 Jan 17 10:46 //calimero/corinna/foo
> 
> Now I add this line to /etc/group:
> 
>  mygroup:S-1-22-2-11125:11125:
> 
> Exit/restart Cygwin.  Now `ls -l' prints
> 
>  -rw-r--r-- 1 corinna mygroup 13342 Jan 17 10:46 //calimero/corinna/foo
> 
> So it works, apparently.  Did you set `group: db' in /etc/nsswitch.conf,
> by any chance?

That did the trick.   My nsswitch.conf was the default (no lines; only comments), but everything works great now once I change it to
group: files
Seems odd that changing it back to 'group: files db' causes the groups to revert to the Unix_Group+601 form (as if the files weren't resolving it satisfactorily).

Thanks for your help looking into this!

[Update:   cygsshd service no longer permits logins (closes connection immediately) when using 'group: files' (but it does work when running as /var/sbin/sshd -Dd).    I'll have to get syslog-ng set up to try do debug this further...]



> 
> 
> Corinna
> 
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