On Fri, 2019-01-11 at 13:10 +0100, Sumit Bose wrote:
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> 
> On Wed, Jan 09, 2019 at 11:28:24PM -0000, Carwyn Edwards wrote:
> > We've just been bitten by the Samba 4.8 rebase in CentOS/RHEL 7.6, 
> > specifically this bit from the RHEL 7.6 release notes:
> > 
> > "The smbd service no longer queries user and group information from Active 
> > Directory domain controllers and NT4 primary domain controllers directly. 
> > Installations with the security parameter set to ads or domain now require 
> > that the winbindd service is running."
> > 
> > Which stems from the Samba 4.8 release notes:
> > 
> > "Domain member setups require winbindd - Setups with "security = domain" or 
> > "security = ads" require a
> > running 'winbindd' now. The fallback that smbd directly contacts domain 
> > controllers is gone."
> > 
> > The RHEL 7 Systems Administration Guide now states:
> > 
> > "Red Hat only supports running Samba as a server with the winbindd service 
> > to provide domain users and groups to the local system. Due to certain 
> > limitations, such as missing Windows access control list (ACL) support and 
> > NT LAN Manager (NTLM) fallback, the System Security Services Daemon (SSSD) 
> > is not supported."
> > 
> > Now in RHEL 7.5 we were managing to use SSSD with Samba, the only real 
> > glitch (we think) was that SIDs rather than names showing up in the share 
> > ACLs. Unfortunately Red Hat support are sticking to the above like glue so 
> > far.
> > 
> > My question to this list is, given the changes to Samba from 4.8, is there 
> > a way to get RHEL 7.6 winbind (for Samba) to use SSSD for the lookups that 
> > works?
> > 
> > I noticed that the package sssd-winbind-idmap that ships in RHEL 7.6 
> > contains the library /usr/lib64/samba/idmap/sss.so which from the idmap_sss 
> > man page states:
> > 
> > "The idmap_sss module provides a way to call SSSD to map UIDs/GIDs and 
> > SIDs."
> > 
> > With a config example:
> > 
> > [global]
> >            ...
> >            idmap config * : backend        = sss
> > 
> > (There an open bugzilla and pagure bug about this example being wrong as 
> > sss is read only).
> > 
> > There's also the following file in the package sssd-client
> > 
> > /usr/lib64/cifs-utils/cifs_idmap_sss.so
> > 
> > Which is controlled via the alternatives system.
> > 
> > I'm not entirely sure how these differ yet but I get the impression that 
> > the intention somewhere is to re-enable Samba to Winbind to SSSD lookups? 
> > Am I on the right track? Could this be made to work with the versions in 
> > RHEL 7.6 if so?
> 
> Yes, you are right.
> 
> I updated the idmap_sss man page in a very recent commit
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpagure.io%2FSSSD%2Fsssd%2Fc%2Fea7ada6c0629df45348f699e30acc44194550801%3Fbranch%3Dmaster&data=02%7C01%7Cjoakim.tjernlund%40infinera.com%7C4f53e5c3fceb44e20aa508d677bdc6c1%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C0%7C636828054310018393&sdata=lQX415HKOyxp5kETxiw%2F511BGUHUR03Q07GztFiNaM8%3D&reserved=0.
> 
> With idmap_sss you can make sure that winbind will use the same ID
> mapping as SSSD so that there is no need to change the ownership of
> files or directories.

I never managed to work out the difference between SSSD's idmap and winbind's 
ad idmap,
what is the difference ?

> 
> Besides the idmap configuration in smb.conf you have to make sure that
> the system is joined the AD with the 'net ads join' command which is
> also used by realmd in the default RHEL/CentOS settings. This is needed
> because winbind expects some extra data added to some internal libraries
> to be able to work properly.

Should not the in git adcli work as well? When will you release it?

> 
> If you have SSSD's version of libwbclient installed please remove the
> sssd-libwbclient package and install Samba's libwbclient package if it
> is missing (but I guess it is already present as a dependency of
> winbind).

Is SSSD's wbclient obsolete or just not finished yet?

> 
> There is also a nice summary by Erinn earlier on this list
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.fedoraproject.org%2Farchives%2Flist%2Fsssd-users%40lists.fedorahosted.org%2Fmessage%2FHSOPA6J7AKUFHPLM2MA6T3P3SJN7TFNW%2F&data=02%7C01%7Cjoakim.tjernlund%40infinera.com%7C4f53e5c3fceb44e20aa508d677bdc6c1%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C0%7C636828054310018393&sdata=RGNMqIOn9%2BkzPBMWzhoUDQGp4zmERL6cnFpYWcAomLM%3D&reserved=0
> which describes some current pitfalls. In this posting the idmap
> 'backend = ad' is used. As long as you are not using SSSD's id-mapping
> (ldap_id_mapping = false) or overrides 'backend = ad' will work as well
> because both winbind and SSSD will use the IDs stored in AD.
> 
> 
> 
> 
> /usr/lib64/cifs-utils/cifs_idmap_sss.so is a helper for the cifs.ko
> kernel module which uses an upcall to let the user-space map SIDs to
> POSIX IDs and back. It is needed on clients where you want to mount
> CIFS/SMB shares into the file-system. Winbind is not needed for this
> use-case.
> 
> 
> HTH
> 
> bye,
> Sumit
> 

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