[Samba] KRB5 pam_winbind using KEYRING does not work

[Rowland Penny]

On Tue, 28 Oct 2025 18:08:26 +0100
Rainer Meier via samba <samba at lists.samba.org> wrote:

> Your config looks basically identical to my one.
> 
>  > I run Debian as standard, so normally the kerberos cache goes into
>  > /tmp
>  > and just works, but it should work.
> 
> Actually yes, using files it works out of the box. But not when using 
> KEYRING.
> 
> 
>  > so I set that up using your
>  > /etc/security/pam_winbind.conf settings and added
>  > 'default_ccache_name = KEYRING:persistent:%{uid}' to the
>  > '[libdefaults]' section of the /etc/krb5.conf file.
> 
> Actually as soon as I insert "krb5_ccache_type = KEYRING" into ghe 
> GLobal section of /etc/security/pam_winbind.conf then winbind fails
> to create the cache entries in KEYRING. There is also no KRB5CCNAME 
> variable defined.
> 
> 
>  > I logged in and ran this: echo "$KRB5CCNAME"
> 
> Are you by any chance also having pam_krb5.so enabled in your PAM 
> configuration? If yes, then it is perhaps not pam_winbind.so setting 
> KRB5CCNAME but pam_krb5 instead.

If you are referring to libpam-krb5, then my first thought was, I
will have to check, until I remembered, redhat stopped providing it,
so no, I am not using it.

> 
> Yes I can do this and it works fine using pam_krb5 but purely using 
> pam_winbind it does not.
> 
> It should not be required to run pam_krb5 before invoking pam_winbind
> in order to set the KRB5CCNAME and somehow force pam_winbind to use
> the KEYRING.

It isn't, I found this out quite a few years ago.

> 
> I will do some more tests with and without pam_krb5 enabled. But I
> was unable yet to convince pam_winbind to write anything to the
> keyring. Even if I manually set KRB5CCNAME=KEYRING:persistent:<UID>
> it is simply empty. So pam_winbind does not populate it.
> 

Looks like I will have to install Arch.

Rowland