• kerberos client on windows not being able to access credentials cache (

    From Tomas Pospisek@21:1/5 to All on Mon Feb 20 14:11:55 2023
    Hello all,

    tldr:

    D:\>C:\OSGeo4W\bin\psql.exe service=the_db
    psql: error: connection to server at "dbserver.example.lan
    (192.168.4.104), port 5432 failed: could not initiate GSSAPI
    security context: No credentials were supplied, or the credentials
    were unavailable or inaccessible: Internal credentials cache error

    Goal
    ====

    I want to have my Postgresql clients (in this case psql.exe) on Windows
    to authenticate against Active Directory.

    Steps taken so far
    ==================

    Linux client -> Active Directory -> Linux server works ------------------------------------------------------

    I was able to get psql on Linux to authenticate against Active Directory
    and with the service ticket that it got from Active Directory to
    authenticate to the Postgresql service and server.

    Windows client -> Active Directory does not work ------------------------------------------------

    I do know that psql.exe (on Windows) is linked and is using GSS to do
    Kerberos authentication.

    A psql.exe that is not linked against GSS will tell me: "gssencmode
    value "require" invalid when GSSAPI support is not compiled in"

    A psql.exe that is linked against GSS will not tell me that. I'm
    evidently now using the latter - a psql.exe that is linked against GSS.

    So I know that the psql.exe that I'm using is linked against GSS.

    Also, in the Windows shell I can issue a klist, and I see the Ticket
    Granting Ticket and I see various service tickets (mainly to mount CIFS shares).

    Also on Windows shell I can issue a

    klist get postgres/dbserver.example.lan@EXAMPLE.LAN

    and I see the ticket listed when I issue klist.

    So I know that getting the service ticket on the Windows client does
    indeed work.

    When using psql.exe without setting `gssencmode = require` I am able to authenticate with username/password and connect to the Postgresql
    service on the DB server just fine.

    So I know that there is no problem with psql.exe wrt to connecting to
    the Postgresql server and there is no problem with authentication per se.

    I tried to trace psql.exe with the "Process Monitor" tool. I see that
    (for whatever reason), psql.exe will open a TCP connection to the
    Postgresql server. But it will *NOT* open a connection to the Active
    Directory server.

    Maybe it *shoud* connect to a local (that is on the local host) authentication/active directory service, but I do not know enough
    Windows to know how I would see that in the "Process Monitor" trace.

    I can see that psql.exe is accessing the Windows Registry and that it's accessing various DLLs, among others the kerberos library, and various
    config files, such as the krb5.conf file, but I can not see it accessing
    a keytab.

    Again I do not know *exactly* how Active Directory/Kerberos access works
    on Windows, but I *suspect* that the protocol on a Windows client is
    *not* using keytab file.

    I do see that `psql.exe` is trying to access a `ccapiserver.exe` file,
    that is not there.

    Question: is a `ccapiserver.exe` executable required in order to be able
    to access tickets from a Kerberos client on a Windows client?

    Other question: is the error "Internal credentials cache error" the root
    cause of psql.exe not being able to authenticate against Active
    Directory (I am supposing that the error "Internal credentials cache
    error" refers to the kerberos client not being able to access the
    *existing* tickets. But in "theory" psql.exe could try getting a ticket *without* accessing the existing tickets? So it wouldn't have to
    forcibly fail there?).

    And another question: is there any way to make GSS more talkative? At
    this moment all that I can get as logs is the above "computer says no".
    I was able to set the kerberos log to a local file, but that just tells
    me that the client now wants to do authentication and that's that.

    So that's as far as I got and I'm a bit at the end of my wisdom and a
    would very, very much appreciate:

    * help on how to proceed from here
    * pointers to how configure krb5.conf-wise a given Windows executable
    that links against GSS so that it can authenticate against active directory
    * any help and pointer or debugging help
    * has anybody been able to authenticate from Windows against Active
    Directory and how did you do that respectively how did you set it up?

    Any help would be very, very much appreciated, thank you.
    *t

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