[kitten] Checking the transited list of a kerberos ticket in a transitive cross-realm trust situation...

[Simo Sorce]

On Wed, 2017-08-23 at 20:38 -0400, Greg Hudson wrote:
> On 08/23/2017 07:01 PM, Stefan Metzmacher wrote:
> > > I think we should first consider whether it would be sufficient
> > > for MIT
> > > krb5 to suppress the rd_req transited check if the
> > > TRANSITED-POLICY-CHECKED flag is set in the ticket.  MIT and
> > > Heimdal
> > > KDCs both appear to perform the transited check and set the flag
> > > by default.
> > 
> > But Windows KDCs doesn't set this bit (I guess because it's just
> > not
> > useful).
> 
> I don't agree at all that the bit isn't useful.  That bit is how a
> KDC
> communicates that it vouches for the transited path.  Unfortunately,
> you
> do appear to be correct about Windows KDCs.  MS-KILE says:
> 
>     The TRANSITED-POLICY-CHECKED flag ([RFC4120] section 2.7): KILE
>     MUST NOT check for transited domains on servers or a KDC.
>     Application servers MUST ignore the TRANSITED-POLICYCHECKED flag.
> 
> which basically means Microsoft has declined to conform to RFC 4120
> in
> this area, instead requiring servers to implement PACs to
> interoperate
> in a cross-realm environment.
> 
> I guess the proposed credential option is necessary, in that case.
> 

I think in this case ignoring the flag should probably be conditional
to whether a PAC is present.

My2c.

Simo.
-- 
Simo Sorce
Sr. Principal Software Engineer
Red Hat, Inc