samba - Jul 2016 - How to GSSAPI/Kerberos authenticate with Dovecot [formerly Where is krb5.keytab or equivalent?]

On Thu, 2016-07-14 at 22:05 +0100, Rowland penny wrote:
> On 14/07/16 21:52, Andrew Bartlett wrote:
> > 
> > Rowland:
> > 
> > Running samba-tool domain exportkeytab for a specific user is quite
> > a
> > reasonable thing to do, and is entirely sensible to recommand as
> > part
> > of adding a new user with an SPN.  They keytab can then be deployed
> > as
> > required.
> > 
> > Running the exportkeytab file is not the same as loading up the DC
> > with
> > other services.  Not that this is a total disaster (particularly
> > for
> > small sites trying to replace SBS), but we do try and make folks
> > think
> > before creating mega-servers.
> > 
> > I'm very happy for such information to be in our wiki, as I do
> > refer to
> > it and refer others to the apache page, which shows the same
> > pattern as
> > required for mod_auth_kerb.
> > 
> > https://wiki.samba.org/index.php/Authenticating_Apache_against_Acti
> > ve_D
> > irectory
> > 
> > Indeed, we need to make this page easier to find.
> > 
> > Andrew Bartlett
> > 
> 
> Andrew, I know all this, but in this instance. the OP is going to
> run 
> Dovecot on the DC. Now, if you are happy to say that Samba is now 
> recommending using the Samba AD DC as a fileserver etc, I am quite
> happy 
> to trawl the wiki, removing any references to not using the DC as a 
> fileserver etc, otherwise, I will go back to my plan of creating a
> wiki 
> page for Dovecot similar to the Apache one.
I didn't see anything in the instructions that were specific to running
on a DC, and in any case, we can afford to be a little less dogmatic
about this.  Please don't go trawling the wiki one way or the other. 

To be clear: I'm happy with the statement currently on the wiki:

Whilst the Domain Controller seems capable of running as a full file
server, it is suggested that organisations run a distinct file server
to allow upgrades of each without disrupting the other. It is also
suggested that medium-sized sites should run more than one DC. It also
makes sense to have the DC's distinct from any file servers that may
use the Domain Controllers. Additionally using distinct file servers
avoids the idiosyncrasies in the winbindd configuration on the Active
Directory Domain Controller. The Samba team does not recommend using a
Samba-based Domain Controller as a file server, and recommend that
users run a separate Domain Member with file shares. 

Thanks,

Andrew Bartlett

-- 
Andrew Bartlett
https://samba.org/~abartlet/
Authentication Developer, Samba Team         https://samba.org
Samba Development and Support, Catalyst IT   
https://catalyst.net.nz/services/samba

On 15/07/16 00:34, Andrew Bartlett wrote:
> On Thu, 2016-07-14 at 22:05 +0100, Rowland penny wrote:
>> On 14/07/16 21:52, Andrew Bartlett wrote:
>>>   
>>> Rowland:
>>>
>>> Running samba-tool domain exportkeytab for a specific user is quite
>>> a
>>> reasonable thing to do, and is entirely sensible to recommand as
>>> part
>>> of adding a new user with an SPN.  They keytab can then be deployed
>>> as
>>> required.
>>>
>>> Running the exportkeytab file is not the same as loading up the DC
>>> with
>>> other services.  Not that this is a total disaster (particularly
>>> for
>>> small sites trying to replace SBS), but we do try and make folks
>>> think
>>> before creating mega-servers.
>>>
>>> I'm very happy for such information to be in our wiki, as I do
>>> refer to
>>> it and refer others to the apache page, which shows the same
>>> pattern as
>>> required for mod_auth_kerb.
>>>
>>> https://wiki.samba.org/index.php/Authenticating_Apache_against_Acti
>>> ve_D
>>> irectory
>>>
>>> Indeed, we need to make this page easier to find.
>>>
>>> Andrew Bartlett
>>>
>> Andrew, I know all this, but in this instance. the OP is going to
>> run
>> Dovecot on the DC. Now, if you are happy to say that Samba is now
>> recommending using the Samba AD DC as a fileserver etc, I am quite
>> happy
>> to trawl the wiki, removing any references to not using the DC as a
>> fileserver etc, otherwise, I will go back to my plan of creating a
>> wiki
>> page for Dovecot similar to the Apache one.
> I didn't see anything in the instructions that were specific to running
> on a DC, and in any case, we can afford to be a little less dogmatic
> about this.  Please don't go trawling the wiki one way or the other.
>
> To be clear: I'm happy with the statement currently on the wiki:
>
> Whilst the Domain Controller seems capable of running as a full file
> server, it is suggested that organisations run a distinct file server
> to allow upgrades of each without disrupting the other. It is also
> suggested that medium-sized sites should run more than one DC. It also
> makes sense to have the DC's distinct from any file servers that may
> use the Domain Controllers. Additionally using distinct file servers
> avoids the idiosyncrasies in the winbindd configuration on the Active
> Directory Domain Controller. The Samba team does not recommend using a
> Samba-based Domain Controller as a file server, and recommend that
> users run a separate Domain Member with file shares.
>
> Thanks,
>
> Andrew Bartlett
>
OK, now we have sorted that out, I will put creating a wiki page for 
Dovecot on my TODO list, it will be based around the Apache page i.e. it 
will say what user & SPN to create and then say howto transfer the 
resultant keytab to another machine, leaving it up to the sysadmin to 
read between the lines.

This is what I planned to do.

Rowland

On 15/07/16 08:17, Rowland penny wrote:
> On 15/07/16 00:34, Andrew Bartlett wrote:
>> On Thu, 2016-07-14 at 22:05 +0100, Rowland penny wrote:
>>> On 14/07/16 21:52, Andrew Bartlett wrote:
>>>>   Rowland:
>>>>
>>>> Running samba-tool domain exportkeytab for a specific user is
quite
>>>> a
>>>> reasonable thing to do, and is entirely sensible to recommand
as
>>>> part
>>>> of adding a new user with an SPN.  They keytab can then be
deployed
>>>> as
>>>> required.
>>>>
>>>> Running the exportkeytab file is not the same as loading up the
DC
>>>> with
>>>> other services.  Not that this is a total disaster
(particularly
>>>> for
>>>> small sites trying to replace SBS), but we do try and make
folks
>>>> think
>>>> before creating mega-servers.
>>>>
>>>> I'm very happy for such information to be in our wiki, as I
do
>>>> refer to
>>>> it and refer others to the apache page, which shows the same
>>>> pattern as
>>>> required for mod_auth_kerb.
>>>>
>>>>
https://wiki.samba.org/index.php/Authenticating_Apache_against_Acti
>>>> ve_D
>>>> irectory
>>>>
>>>> Indeed, we need to make this page easier to find.
>>>>
>>>> Andrew Bartlett
>>>>
>>> Andrew, I know all this, but in this instance. the OP is going to
>>> run
>>> Dovecot on the DC. Now, if you are happy to say that Samba is now
>>> recommending using the Samba AD DC as a fileserver etc, I am quite
>>> happy
>>> to trawl the wiki, removing any references to not using the DC as a
>>> fileserver etc, otherwise, I will go back to my plan of creating a
>>> wiki
>>> page for Dovecot similar to the Apache one.
>> I didn't see anything in the instructions that were specific to
running
>> on a DC, and in any case, we can afford to be a little less dogmatic
>> about this.  Please don't go trawling the wiki one way or the
other.
>>
>> To be clear: I'm happy with the statement currently on the wiki:
>>
>> Whilst the Domain Controller seems capable of running as a full file
>> server, it is suggested that organisations run a distinct file server
>> to allow upgrades of each without disrupting the other. It is also
>> suggested that medium-sized sites should run more than one DC. It also
>> makes sense to have the DC's distinct from any file servers that
may
>> use the Domain Controllers. Additionally using distinct file servers
>> avoids the idiosyncrasies in the winbindd configuration on the Active
>> Directory Domain Controller. The Samba team does not recommend using a
>> Samba-based Domain Controller as a file server, and recommend that
>> users run a separate Domain Member with file shares.
>>
>> Thanks,
>>
>> Andrew Bartlett
>>
>
> OK, now we have sorted that out, I will put creating a wiki page for 
> Dovecot on my TODO list, it will be based around the Apache page i.e. 
> it will say what user & SPN to create and then say howto transfer the 
> resultant keytab to another machine, leaving it up to the sysadmin to 
> read between the lines.
>
> This is what I planned to do.
>
> Rowland
>
>
OK, just an update on the new wiki page for Dovecot, I started to write 
it and realised there is a potential problem.

The user created in AD is called 'dovecot' and the Dovecot packages also
want to create a user called 'dovecot' in /etc/passwd, they cannot both 
exist.

Not have having posting rights on the Dovecot list (and I don't want to 
sign up to ask one question), I have asked Marc to ask Dovecot if we can 
use a different name in AD.

Rowland