Обсуждение: GSSAPI authentication

Hello all

 

We are running Postgres 14 on Ubuntu. Our Windows users connect passwordless using GSSAPI. This works great.

 

Now we want users on Linux client to also connect passwordless using GSSAPI. Users on Linux log on using their Active Directory credentials, as the Linux host (Ubuntu 22.04) is joined to the domain. Logon to Linux works fine, access to Windows cifs shares works fine authentication with Kerberos.

 

But psql won't connect using GSSAPI. It does hit the right pg_hba.conf line and the username is translated via pg_ident.conf, just fine. But psql says

 

psql: error: connection to server at "srvpostgres4.xxx.local" (172.30.33.30), port 1609 failed: could not initiate GSSAPI security context: Unspecified GSS failure.  Minor code may provide more information: Server not found in Kerberos database connection to server at "srvpostgres4.xxx.local" (172.30.33.30), port 1609 failed: GSSAPI continuation error: Unspecified GSS failure.  Minor code may provide more information: Server not found in Kerberos database

 

Server log is like this

 

2022-06-06 08:14:01.176 CEST,"yyy","db1",474094,"172.30.32.213:33556",627e83c9.73bee,2,"authentication",2022-06-06 08:14:01 CEST,2/14544,0,FATAL,28000,"GSSAPI authentication failed for user ""yyy""","Connection matched pg_hba.conf line 15: ""host    all             all             172.0.0.0/8             gss map=xxxlocal include_realm=0 krb_realm=""XXX.LOCAL""""",,,,,,,,"","client backend",,-3382135431624836920

 

We are a bit lost here. What are we missing?

 

Regards Niels Jespersen

 

 

 

 

 

 

 

 

 

This sounds like your PG service was unable to authenticate itself to AD.

There's probably a trick to that somewhere - AD doesn't really want to be a Kerberos server, it just happens to use it 😉

On Mon, 6 June 2022, 10:05 pm Niels Jespersen, <NJN@dst.dk> wrote:

Hello all

 

We are running Postgres 14 on Ubuntu. Our Windows users connect passwordless using GSSAPI. This works great.

 

Now we want users on Linux client to also connect passwordless using GSSAPI. Users on Linux log on using their Active Directory credentials, as the Linux host (Ubuntu 22.04) is joined to the domain. Logon to Linux works fine, access to Windows cifs shares works fine authentication with Kerberos.

 

But psql won't connect using GSSAPI. It does hit the right pg_hba.conf line and the username is translated via pg_ident.conf, just fine. But psql says

 

psql: error: connection to server at "srvpostgres4.xxx.local" (172.30.33.30), port 1609 failed: could not initiate GSSAPI security context: Unspecified GSS failure.  Minor code may provide more information: Server not found in Kerberos database connection to server at "srvpostgres4.xxx.local" (172.30.33.30), port 1609 failed: GSSAPI continuation error: Unspecified GSS failure.  Minor code may provide more information: Server not found in Kerberos database

 

Server log is like this

 

2022-06-06 08:14:01.176 CEST,"yyy","db1",474094,"172.30.32.213:33556",627e83c9.73bee,2,"authentication",2022-06-06 08:14:01 CEST,2/14544,0,FATAL,28000,"GSSAPI authentication failed for user ""yyy""","Connection matched pg_hba.conf line 15: ""host    all             all             172.0.0.0/8             gss map=xxxlocal include_realm=0 krb_realm=""XXX.LOCAL""""",,,,,,,,"","client backend",,-3382135431624836920

 

We are a bit lost here. What are we missing?

 

Regards Niels Jespersen

 

 

 

 

 

 

 

 

 

Fra: Michael van der Kolff <mvanderkolff@gmail.com>
Sendt: 6. juni 2022 14:26
Til: Niels Jespersen <NJN@dst.dk>
Cc: pgsql-general list <pgsql-general@lists.postgresql.org>
Emne: Re: GSSAPI authentication

 

>This sounds like your PG service was unable to authenticate itself to AD.

> 

>There's probably a trick to that somewhere - AD doesn't really want to be a Kerberos server, it just happens to use it 😉

 

But it works fine when the same AD-user connects from Windows to the same postgres (Linux) server. Auth fails when the user initiates login from a Linux box (that otherwise uses Kerberized ressources just fine).

 

Niels

The part that you're missing, I think, is that Kerberized services require a service account.

The SPN (service principal name) is the name that is used in Kerberos contexts for that service account. PostgreSQL uses postgres/${hostname}@${realm} by default - see https://www.postgresql.org/docs/14/gssapi-auth.html.

The important part to note here is that $hostname must match what is registered in the SPN for the user that you're using as the service account in AD. It might (I don't know) have to match what AD believes about the host from its PTR records for that domain as well.

--Michael

On Mon, Jun 6, 2022 at 11:33 PM Niels Jespersen <NJN@dst.dk> wrote:

Fra: Michael van der Kolff <mvanderkolff@gmail.com>
Sendt: 6. juni 2022 14:26
Til: Niels Jespersen <NJN@dst.dk>
Cc: pgsql-general list <pgsql-general@lists.postgresql.org>
Emne: Re: GSSAPI authentication

 

>This sounds like your PG service was unable to authenticate itself to AD.

> 

>There's probably a trick to that somewhere - AD doesn't really want to be a Kerberos server, it just happens to use it 😉

 

But it works fine when the same AD-user connects from Windows to the same postgres (Linux) server. Auth fails when the user initiates login from a Linux box (that otherwise uses Kerberized ressources just fine).

 

Niels

Oh wait, I see.

On Mon, Jun 6, 2022 at 11:41 PM Michael van der Kolff <mvanderkolff@gmail.com> wrote:

The part that you're missing, I think, is that Kerberized services require a service account.

The SPN (service principal name) is the name that is used in Kerberos contexts for that service account. PostgreSQL uses postgres/${hostname}@${realm} by default - see https://www.postgresql.org/docs/14/gssapi-auth.html.

The important part to note here is that $hostname must match what is registered in the SPN for the user that you're using as the service account in AD. It might (I don't know) have to match what AD believes about the host from its PTR records for that domain as well.

--Michael

On Mon, Jun 6, 2022 at 11:33 PM Niels Jespersen <NJN@dst.dk> wrote:

Fra: Michael van der Kolff <mvanderkolff@gmail.com>
Sendt: 6. juni 2022 14:26
Til: Niels Jespersen <NJN@dst.dk>
Cc: pgsql-general list <pgsql-general@lists.postgresql.org>
Emne: Re: GSSAPI authentication

 

>This sounds like your PG service was unable to authenticate itself to AD.

> 

>There's probably a trick to that somewhere - AD doesn't really want to be a Kerberos server, it just happens to use it 😉

 

But it works fine when the same AD-user connects from Windows to the same postgres (Linux) server. Auth fails when the user initiates login from a Linux box (that otherwise uses Kerberized ressources just fine).

 

Niels