Kerberos Ticket not renewed anymore after being forwarded.

[Simo Sorce]

kadmin is not involved with ticket renewal or delegation.
more likely MacOSX GSSAPI implementation requests a forwardable TGT that
is not renewable and then forwards that one to the remote server.
It is not a bad idea to limit forwarded tickets that way.

Simo.

On Thu, 2016-10-27 at 13:37 +0200, vm at c4k3.space wrote:
> So far my attempt to ask it to the community :-)
> But I think I finally managed to find the explanation.
> So in case someone else ever has the same problem, searches why and 
> stumbles onto this page...
> 
> The kadmin-protocol that differs between the heimdal-implementation used 
> in Mac OS and the MIT-implementation on linux seems to be the culprit.
> 
> http://kerberos.996246.n3.nabble.com/Lion-problems-tc13877.html
> 
> |
> | Mar 12, 2012; 9:52pm  Arthur Prokosch-2 Arthur Prokosch-2
> | ...
> | We've wandered into Heimdal territory here and should probably switch
> | to [hidden email] or discussions.apple.com.  In the meantime:
> | if anyone else has seen Mac OS 10.7 Heimdal tickets lose their
> | Forwardable and Proxiable flags in the process of initiating GSSAPI
> | ssh connections or has an explanation, I'd be quite interested to hear
> | off-list.
> |
> | best,
> | -arthur prokosch
> | system administrator
> | [1]MIT Computer Science and Artificial Intelligence Lab.
> | ...
> 
> 
> In the meantime I also tested it on MacOS Sierra. Problem is still 
> there.
> 
> I don't know if there is any solution though.
> 
> P.S. Anybody who confirms my hypothesis?
> 
> 
> 
> vm at c4k3.space schreef op 2016-10-26 14:21:
> > Hi,
> > 
> > I hope I'm at the right place here for my issue.
> > 
> > This is the case:
> > 
> > 
> > On my macbook (Mac OS X 10.11), I have a renewable Kerberos-ticket:
> > 
> > ---
> > macbook013:~ vm$ klist -v
> >   Credentials cache: API:EF9959E6-85DF-446F-9B21-3CEEC606FA2D
> >           Principal: vm at REALM.COM
> >       Cache version: 0
> > 
> >   Server: krbtgt/REALM.COM at REALM.COM
> >   Client: vm at REALM.COM
> >   Ticket etype: aes256-cts-hmac-sha1-96, kvno 1
> >   Ticket length: 342
> >   Auth time:  Oct 26 13:55:09 2016
> >   End time:   Nov 25 12:55:05 2016
> >   Renew till: Jan 26 12:55:05 2017
> >   Ticket flags: enc-pa-rep, pre-authent, initial, renewable, proxiable,
> > forwardable
> >   Addresses: addressless
> > ---
> > 
> > If I do a ssh (GSSAPIAuthentication yes,GSSAPIDelegateCredentials yes)
> > to a linux-server, the ticket there is not renewable anymore:
> > 
> > ---
> >   macbook013:~ vm$ ssh linuxserver2
> >   linuxserver2 ~ # klist -f
> >   Ticket cache: FILE:/tmp/krb5cc_1379_BZVstF6000
> >   Default principal: vm at REALM.COM
> > 
> >   Valid starting     Expires            Service principal
> >   10/26/16 14:00:30  11/25/16 12:55:05  krbtgt/REALM.COM at REALM.COM
> >          Flags: FfPAT
> >   linuxserver2 ~ # krenew
> >   krenew: error renewing credentials: KDC can't fulfill requested 
> > option
> >   linuxserver2 ~ # kinit -R
> >   kinit: KDC can't fulfill requested option while renewing credentials
> > ---
> > 
> > If I do a kinit on linuxserver1 and get a renewable ticket there and 
> > ssh
> > to linuxserver2, the forwarded ticket stays renewable.
> > 
> > I guess it has something to do with the ssh-client on Mac OS X? (but
> > copying the ssh_config from linuxserver1 to the macbook does not solve
> > it. Copying the krb5.conf doesn't solve it either)
> > Or should I search the cause in another direction?
> > Maybe I'm missing something obvious.
> > 
> > 
> > Thank you for thinking with me!
> > 
> > VM
> > ________________________________________________
> > Kerberos mailing list           Kerberos at mit.edu
> > https://mailman.mit.edu/mailman/listinfo/kerberos
> 
> ________________________________________________
> Kerberos mailing list           Kerberos at mit.edu
> https://mailman.mit.edu/mailman/listinfo/kerberos


-- 
Simo Sorce * Red Hat, Inc * New York