[Samba] Exporting keytab for SPN failure

Fri Sep 16 21:10:41 UTC 2016

On Fri, 16 Sep 2016 22:58:43 +0200
Achim Gottinger via samba <samba at lists.samba.org> wrote:

> 
> 
> Am 16.09.2016 um 22:43 schrieb Achim Gottinger via samba:
> >
> >
> > Am 16.09.2016 um 22:00 schrieb Robert Moulton via samba:
> >> Achim Gottinger via samba wrote on 9/15/16 1:20 AM:
> >>>
> >>>
> >>> Am 15.09.2016 um 09:35 schrieb Rowland Penny via samba:
> >>>> On Wed, 14 Sep 2016 16:23:27 -0500
> >>>> Michael A Weber via samba <samba at lists.samba.org> wrote:
> >>>>
> >>>>>> On Sep 14, 2016, at 2:00 PM, Achim Gottinger <achim at ag-web.biz>
> >>>>>> wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> Am 14.09.2016 um 20:33 schrieb Michael A Weber:
> >>>>>>>> On Sep 14, 2016, at 1:10 PM, Achim Gottinger
> >>>>>>>> <achim at ag-web.biz <mailto:achim at ag-web.biz>> wrote:
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Am 14.09.2016 um 19:53 schrieb Michael A Weber:
> >>>>>>>>>> On Sep 14, 2016, at 12:23 PM, Achim Gottinger via samba
> >>>>>>>>>> <samba at lists.samba.org <mailto:samba at lists.samba.org>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> Am 14.09.2016 um 18:23 schrieb Michael A Weber:
> >>>>>>>>>>> Question though, just for my curiosity:
> >>>>>>>>>>>
> >>>>>>>>>>> The encryption algorithms specified after each SPN:  I see
> >>>>>>>>>>> that aes-256 is listed when I export the user, but not the
> >>>>>>>>>>> SPN.  Are those expected, or have I done something wrong
> >>>>>>>>>>> and used incorrect algorithms somewhere?  I recall
> >>>>>>>>>>> reading that DES is not secure enough and that AES-256 (I
> >>>>>>>>>>> think I read this during TLS enablement) is what should
> >>>>>>>>>>> be used.
> >>>>>>>>>> I get the same behaviour here. If i do nout use the FQDN
> >>>>>>>>>> and only the hostname without the domain part the aes keys
> >>>>>>>>>> are included. In your case --principal HTTP/intranet.
> >>>>>>>>> So, now I’m a little more confused.  I’ve added the SPN to
> >>>>>>>>> the user without the realm part, which succeeds.  I listed
> >>>>>>>>> it to verify, and it’s there (sanitized here):
> >>>>>>>>>
> >>>>>>>>> samba-tool spn list web-intranet-macmini
> >>>>>>>>> web-intranet-macmini
> >>>>>>>>> User
> >>>>>>>>> CN=web-intranet-macmini,CN=Users,DC=domain2,DC=domain1,DC=tld
> >>>>>>>>> has the following servicePrincipalName:
> >>>>>>>>> HTTP/intranet.domain2.domain1.tld
> >>>>>>>>>
> >>>>>>>>> Then, if I go to export the keytab as you have indicated
> >>>>>>>>> above with —principal=HTTP/intranet it errors:
> >>>>>>>>>
> >>>>>>>>> samba-tool domain exportkeytab ~/intranet-macmini.keytab
> >>>>>>>>> --principal=HTTP/intranet ERROR(runtime): uncaught
> >>>>>>>>> exception - Key table entry not found File
> >>>>>>>>> "/usr/lib64/python2.6/site-packages/samba/netcmd/__init__.py",
> >>>>>>>>> line 175, in _run return self.run(*args, **kwargs) File
> >>>>>>>>> "/usr/lib64/python2.6/site-packages/samba/netcmd/domain.py",
> >>>>>>>>> line 129, in run net.export_keytab(keytab=keytab,
> >>>>>>>>> principal=principal)
> >>>>>>>>>
> >>>>>>>>> Should that command work?  Or, was that for
> >>>>>>>>> demonstration/explanation purposes only?  I’m assuming it
> >>>>>>>>> worked for you since you referenced my specific case.
> >>>>>>>>>
> >>>>>>>>> I feel I’m missing something.
> >>>>>>>>>
> >>>>>>>>>> The encryption methods used can be controlled with net ads
> >>>>>>>>>> enctypes.
> >>>>>>>>>>
> >>>>>>>>>> If i run (after kinit Administrator)
> >>>>>>>>>> net ads enctypes list dc1$
> >>>>>>>>>> i get
> >>>>>>>>>> 'dc1$' uses "msDS-SupportedEncryptionTypes": 31
> >>>>>>>>>> (0x0000001f) [X] 0x00000001 DES-CBC-CRC
> >>>>>>>>>> [X] 0x00000002 DES-CBC-MD5
> >>>>>>>>>> [X] 0x00000004 RC4-HMAC
> >>>>>>>>>> [X] 0x00000008 AES128-CTS-HMAC-SHA1-96
> >>>>>>>>>> [X] 0x00000010 AES256-CTS-HMAC-SHA1-96
> >>>>>>>>>>
> >>>>>>>>> I get this as well.
> >>>>>>>>>
> >>>>>>>>>> If i use
> >>>>>>>>>> net ads enctypes list dc1.domain.local$
> >>>>>>>>>> i get
> >>>>>>>>>> no account found with filter:
> >>>>>>>>>> (&(objectclass=user)(sAMAccountName=dc1.domain.local$))
> >>>>>>>>>>
> >>>>>>>>> Again, I get this as well.
> >>>>>>>>>
> >>>>>>>>>> Seems "samba-tool domain exportkeytab" uses an similar
> >>>>>>>>>> algorythm and therefore does not find the account and uses
> >>>>>>>>>> des and arcfour keys per default.
> >>>>>>>>>>
> >>>>>>>>>> -- 
> >>>>>>>>>> To unsubscribe from this list go to the following URL and
> >>>>>>>>>> read the instructions:
> >>>>>>>>>> https://lists.samba.org/mailman/options/samba
> >>>>>>>>>> <https://lists.samba.org/mailman/options/samba>
> >>>>>>>>> Mike
> >>>>>>>> Try this
> >>>>>>>> net ads enctypes set web-intranet-macmini 31
> >>>>>>>>
> >>>>>>>> Afterwards "domain export" will export also aes keys for the
> >>>>>>>> SPN's.
> >>>>>>> And, this is why I addressed you as “experts” earlier.
> >>>>>>> Indeed, it did!
> >>>>>>>
> >>>>>>> Now, I’m going to use ktutil to pull these into my existing
> >>>>>>> keytab on the destination machine and begin my testing.
> >>>>>>>
> >>>>>>> Thank you tremendously (although I think we may have created
> >>>>>>> hell for Rowland with the wiki documentation)!
> >>>>>>>
> >>>>>>> Mike
> >>>>>> I was wondering about the missing aes keys for an while. So
> >>>>>> thanks for bringing it up on the list.
> >>>>>>
> >>>>>> If an user gets created the attribute
> >>>>>> msDS-SupportedEncryptionTypes remains undefined and in this
> >>>>>> case only des and rc4 keys are exported.
> >>>>>>
> >>>>>> net ads enctypes set [hostname] [key value] can be used to
> >>>>>> define the valid keys for an accound (and it's spn's).
> >>>>>>
> >>>>>> The key value is repesented as
> >>>>>> 0x00000001 DES-CBC-CRC
> >>>>>> 0x00000002 DES-CBC-MD5
> >>>>>> 0x00000004 RC4-HMAC
> >>>>>> 0x00000008 AES128-CTS-HMAC-SHA1-96
> >>>>>> 0x00000010 AES256-CTS-HMAC-SHA1-96
> >>>>> (you mean, 0x00000016, for the last entry)
> >>>>>
> >>>>>> So using 31 enables all of them. samba-tool domain exportkeytab
> >>>>>> does always export des and rc4 keys but honours 0x8 for aes128
> >>>>>> and 0x10 for aes256. I assume if enctypes are set to 24 for
> >>>>>> example (only aes128/256) the server will honour this and
> >>>>>> decline des and rc4 attempts.
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>> That’s interesting, indeed.
> >>>>>
> >>>>> Rowland—
> >>>>>
> >>>>> This whole thing seems to me like we are duplicating the
> >>>>> functionality of the ktpass command on a Windows AD.  With that
> >>>>> command, one would need to include an encoding type, and I’m
> >>>>> just wondering if it should be included in the wiki pages as
> >>>>> well rather than trying to add it back manually after the
> >>>>> export. Also, something tells me that the ktpass command, when
> >>>>> creating the SPN for a user, also sets the required encoding
> >>>>> type.
> >>>>>
> >>>>> Thoughts?
> >>>>>
> >>>>> Mike
> >>>> The problem is the command 'samba-tool spn add' does just that,
> >>>> it only
> >>>> adds the 'servicePrincipalName', no enctypes are mentioned.
> >>>>
> >>>> Exporting the keytab is the same, there is no mention of enctypes
> >>>>
> >>>> So, until this changes, the wiki can only document what actually
> >>>> happens.
> >>>>
> >>>> Rowland
> >>>>
> >>> Hello Rowland,
> >>>
> >>> As I wrote before you can use the command
> >>>
> >>> net ads enctypes set [username] 31
> >>>
> >>> to convince domain export to export also the aes keys for the
> >>> SPN's assigned to [username] like it is done for [username].
> >>> If only aes keys are wanted in the keytab file unwanted keys can
> >>> be removed from the keytab file with ktutil.
> >>>
> >>> See here for more info about "net ads enctypes"
> >>> https://www.mail-archive.com/cifs-protocol@lists.samba.org/msg00062.html. 
> >>>
> >>> It controls which encryption types are used for ticket generation
> >>> on the
> >>> server.
> >>>
> >>> achim~
> >>
> >> I've been trying to follow this thread but admit I'm still missing 
> >> something. Given the example below, what needs to be done to get
> >> the aes keys in the keytab, exactly?
> >>
> >> # net ads enctypes list hostname$
> >> 'hostname$' uses "msDS-SupportedEncryptionTypes": 31 (0x0000001f)
> >> [X] 0x00000001 DES-CBC-CRC
> >> [X] 0x00000002 DES-CBC-MD5
> >> [X] 0x00000004 RC4-HMAC
> >> [X] 0x00000008 AES128-CTS-HMAC-SHA1-96
> >> [X] 0x00000010 AES256-CTS-HMAC-SHA1-96
> >>
> >> # samba-tool domain exportkeytab test --principal=hostname$
> >>
> >> # klist -ke test
> >> Keytab name: FILE:test
> >> KVNO Principal
> >> ---- 
> >> --------------------------------------------------------------------------
> >>    1 hostname$@EXAMPLE.COM (des-cbc-crc)
> >>    1 hostname$@EXAMPLE.COM (des-cbc-md5)
> >>    1 hostname$@EXAMPLE.COM (arcfour-hmac)
> >>
> > What version of samba are you using? For my tests i used 4.4.5.
> > "net enctypes" was added wth version 4.2.10.
> > Setting enctypes was only necessary here for aes keys with spn's as 
> > principals. upn's/usernames always export the aes keys here.
> >
> Just tested with 4.2.10 and i get your results no aes keys in export.
> 

Ah, I wonder if Robert's AD has been upgraded to 4.4.5 ? and the
enctypes have never been added during the upgrade.

Rowland