On Mon, Mar 27, 2023 at 4:02 PM Spike White <[email protected]> wrote:

> Pieter,
>
> I have Connection -> SSH -> Auth -> GSSAPI -> Allow GSSAPI ->
> credential delegation turned on in putty.
>
> As well as on the target Linux server, it has [libdefaults]
> forwardable = true.  The error I get when I ssh in is:
>
> [admspike_white@austgcore17 ~]$ klist
> klist: Credentials cache 'KCM:2025431' not found
> [admspike_white@austgcore17 ~]$
>
> where 2025431 is my UID.

PuTTY uses the Windows Kerberos libraries, which means it obeys their
restrictions.  One of those restrictions is that credentials may only
be delegated to a host whose UserAccountControl attribute (on the
host’s AD user account object) has the TRUSTED_FOR_DELEGATION flag
set.  See:

https://learn.microsoft.com/en-us/troubleshoot/windows-server/identity/useraccountcontrol-manipulate-account-properties

If the target host does not have the TRUSTED_FOR_DELEGATION flag set
on its UserAccountControl attribute, PuTTY silently refuses to
delegate credentials.

In contrast, MIT Kerberos (which OpenSSH typically links against) is
not AD-aware, so neither ssh nor sshd pay any attention to the target
host’s UserAccountControl attribute when deciding to forward (or
accept forwarded) credentials.

If you can query your AD domain, you can decipher the
UserAccountControl attribute of the target host user object.  E.g.:

Not set (WORKSTATION_TRUST_ACCOUNT only):

    userAccountControl: 4096

Set (WORKSTATION_TRUST_ACCOUNT + TRUSTED_FOR_DELEGATION):

    userAccountControl: 528384
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