I have successfully joined an ubuntu machine (Ubuntu 20.04 LTS) to an Active Directory.
Therefore, I can log in with AD-Accounts, obtain and renew the ticket grantin ticket for the user, and access network shares with Kerberos authentication.
However, I struggle to obtain the initial credentials for the computer account:
admin@comp01:~$ sudo KRB5_TRACE=/dev/stdout kinit -kt /etc/krb5.keytab
[sudo] password for admin:
[232252] 1645435537.855061: Getting initial credentials for host/[email protected]
[232252] 1645435537.855062: Looked up etypes in keytab: rc4-hmac, aes128-cts, aes256-cts
[232252] 1645435537.855064: Sending unauthenticated request
[232252] 1645435537.855065: Sending request (187 bytes) to COMPANY.LAN
[232252] 1645435537.855066: Sending initial UDP request to dgram 172.27.17.6:88
[232252] 1645435537.855067: Received answer (84 bytes) from dgram 172.27.17.6:88
[232252] 1645435537.855068: Response was from master KDC
[232252] 1645435537.855069: Received error from KDC: -1765328378/Client not found in Kerberos database
kinit: Client 'host/[email protected]' not found in Kerberos database while getting initial credentials
I have spent several hours on that issue without progress. Probably I am missing some essential steps.
The requested principal is contained in the local keytab on the ubuntu machine:
root@comp01:~$ klist -kte
Keytab name: FILE:/etc/krb5.keytab
KVNO Timestamp Principal
---- ------------------- ---------------------------------------------
4 02/17/2022 07:34:59 [email protected] (arcfour-hmac)
4 02/17/2022 07:34:59 [email protected] (aes128-cts-hmac-sha1-96)
4 02/17/2022 07:34:59 [email protected] (aes256-cts-hmac-sha1-96)
4 02/17/2022 07:34:59 host/[email protected] (arcfour-hmac)
4 02/17/2022 07:34:59 host/[email protected] (aes128-cts-hmac-sha1-96)
4 02/17/2022 07:34:59 host/[email protected] (aes256-cts-hmac-sha1-96)
4 02/17/2022 07:34:59 host/[email protected] (arcfour-hmac)
4 02/17/2022 07:34:59 host/[email protected] (aes128-cts-hmac-sha1-96)
4 02/17/2022 07:35:00 host/[email protected] (aes256-cts-hmac-sha1-96)
4 02/17/2022 07:35:00 RestrictedKrbHost/[email protected] (arcfour-hmac)
4 02/17/2022 07:35:00 RestrictedKrbHost/[email protected] (aes128-cts-hmac-sha1-96)
4 02/17/2022 07:35:00 RestrictedKrbHost/[email protected] (aes256-cts-hmac-sha1-96)
4 02/17/2022 07:35:00 RestrictedKrbHost/[email protected] (arcfour-hmac)
4 02/17/2022 07:35:00 RestrictedKrbHost/[email protected] (aes128-cts-hmac-sha1-96)
4 02/17/2022 07:35:00 RestrictedKrbHost/[email protected] (aes256-cts-hmac-sha1-96)
And the principal is also registered on the AD-Domain controller:
> setspn -L comp01
Registrierte Dienstprinzipalnamen (SPN) für CN=COMP01,CN=Computers,DC=company,DC=lan:
RestrictedKrbHost/comp01.company.lan
host/comp01.company.lan
RestrictedKrbHost/COMP01
host/COMP01
The ubuntu machine has been joined to the AD-Domain using
> realm join company.lan
And the Kerberos configuration file is as follows:
[libdefaults]
default_realm = COMPANY.LAN
ccache_type = 4
forwardable = true
proxiable = true
fcc-mit-ticketflags = true
[realms]
COMPANY.LAN = {
kdc = DC.company.lan
admin_server = DC.company.lan
default_domain = company.lan
}
[domain_realm]
.company.lan = COMPANY.LAN
company.lan = COMPANY.LAN
Forward and reverse DNS are also looking good:
> nslookup comp01
Server: DC.company.lan
Address: 172.27.17.41
Name: comp01.company.lan
Address: 172.27.17.131
> nslookup 172.27.17.131
Server: DC.company.lan
Address: 172.27.17.41
Name: comp01.company.lan
Address: 172.27.17.131
I am really thankful for any hint that guides me in the right direction.
