PostgreSQL (linux) configuration with GSSAPI to a Windows domain

I'm trying to configure authentication between PostgreSQL database server on linux and Windows Active Directory.

First part of configuration is working but when I'm trying to authenticate from Windows client, it is not working with message: Can't obtain database list from the server. SSPI continuation error. The specified target is unknown or unreachable (80090303)

On Windows:

Domain is AD.CORP.COM

Host is: WIN.AD.CORP.COM, IP is 192.168.1.173

On Linux (Ubuntu 16.04)

hostname is UBUNTU.ad.corp.com, IP is 192.168.1.143

DNS are configured to reach the AD sytem (.173)

PostgreSQL 9.6.9 on x86_64-pc-linux-gnu (Ubuntu 9.6.9-2.pgdg16.04+1), compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609, 64-bit

I've created à service user called POSTGRES and a normal user in AD called ubuntupg. 

Finally I've created the SPN:

setspn -A POSTGRES/UBUNTU.ad.corp.com POSTGRES

Generated the keytab to put on the linux server:

ktpass -out postgres.keytab -princ POSTGRES/UBUNTU.ad.corp.com@AD.CORP.COM -mapUser POSTGRES -pass 'thepassword' -crypto all -ptype KRB5_NT_PRINCIPAL

On the linux /etc/krb5.conf:

[libdefaults]
  debug=true
  default_realm = AD.CORP.COM
  dns_lookup_realm = false
  dns_lookup_kdc = false
  ticket_lifetime = 24h
  renew_lifetime = 7d
  forwardable = true

[realms]
  AD.CORP.COM = {

    kdc = WIN.AD.CORP.COM
  }

[domain_realm]
  ad.corp.com = AD.CORP.COM

  .ad.corp.com = AD.CORP.COM

Making this command work and klist return a ticket:

kinit -V -k -t /etc/postgresql/9.6/main/postgres.keytab POSTGRES/UBUNTU.ad.corp.com@AD.CORP.COM

klist -k /etc/postgresql/9.6/main/postgres.keytab

POSTGRES/UBUNTU.ad.corp.com@AD.CORP.COM

Here is the added onfiguration to postgresql.conf

krb_server_keyfile = '/etc/postgresql/9.6/main/postgres.keytab'

Here is the configuration of pg_hba.conf

host    all              all            0.0.0.0/0 gss

Up to here, all is working as expected, kinit with ubuntupg is also working well. ubuntupg and ubuntupg@ad.corp.com is also created on the database. The probleme is when I try, from a Windows client, connecting to the DB.

psql.exe -h 192.168.1.143 -U ubuntupg

Can't obtain database list from the server. SSPI continuation error. The specified target is unknown or unreachable (80090303)

PostgreSQL log file show:

2019-02-28 14:02:54.178 EST [6747] [unknown]@[unknown] LOG:  00000: connection received: host=192.168.1.176 port=57254
2019-02-28 14:02:54.178 EST [6747] [unknown]@[unknown] LOCATION:  BackendInitialize, postmaster.c:4188
2019-02-28 14:02:54.331 EST [6747] ubuntupg@ubuntupg FATAL:  28000: GSSAPI authentication failed for user "ubuntupg"
2019-02-28 14:02:54.331 EST [6747] ubuntupg@ubuntupg DETAIL:  Connection matched pg_hba.conf line 92: "host    all              all            0.0.0.0/0 gss"
2019-02-28 14:02:54.331 EST [6747] ubuntupg@ubuntupg LOCATION:  auth_failed, auth.c:307

psql.exe -h 192.168.1.143 -U ubuntupg@ad.corp.com

2019-02-28 14:06:35.992 EST [6866] [unknown]@[unknown] LOG:  00000: connection received: host=192.168.1.176 port=57282

2019-02-28 14:06:35.992 EST [6866] [unknown]@[unknown] LOCATION:  BackendInitialize, postmaster.c:4188

2019-02-28 14:06:36.148 EST [6866] ubuntupg@ad.corp.com@ubuntupg@ad.corp.com FATAL:  28000: GSSAPI authentication failed for user "ubuntupg@ad.corp.com"

2019-02-28 14:06:36.148 EST [6866] ubuntupg@ad.corp.com@ubuntupg@ad.corp.com DETAIL:  Connection matched pg_hba.conf line 96: "host    all              all            0.0.0.0/0 gss"

2019-02-28 14:06:36.148 EST [6866] ubuntupg@ad.corp.com@ubuntupg@ad.corp.com LOCATION:  auth_failed, auth.c:307

Thank you very much for your help.

Best regards,