[2380] in Kerberos
Re: telnet encryption option vs. Clarkson TCP
daemon@ATHENA.MIT.EDU (Patrick Herlihy)
Wed Nov 18 18:07:31 1992
Date: 18 Nov 92 21:38:56 GMT
From: P.Herlihy@ccsd.uts.edu.au (Patrick Herlihy)
To: kerberos@shelby.Stanford.EDU
alan@CURTA.CC.COLUMBIA.EDU (Alan Crosswell) writes:
>I wonder if you have heard of any interoperability problems between
>the Kerberized (version 4) telnetd that came with the first beta of
>MIT Kerberos 5 and Clarkson TCP for the PC (CUTE-2.2TN-D).
>The problem I have is the telnet session "freezes" right around the
>TELOPT_ENCRYPTION (option 38) negotiation. Clarkson TCP is not
>capable of doing the auth or encrypt options (boy do I wish!) so it is
>just something messing up in the part where the unknown option is
>supposed to be rejected. If I recompile telnetd with -UENCRYPT then
>Clarkson TCP is able to get in. Other telnet clients like Unix and
>Kermit can get in just fine.
I figured that Clarkson TCP just doesn't handle the encryption option
properly: telnetd says "WILL ENCRYPT", expecting a response from CUTCP
if it won't encrypt; CUTCP just ignores the option altogether.
Telnetd then assumes that the option has been accepted, and waits in a loop
expecting to get encryption key info.
If you make the initial telnetd option "DO ENCRYPT" instead of "WILL ENCRYPT",
and put a "WILL ENCRYPT" later on, CUTCP will respond properly in the
negative.
My diffs to telnetd/telnetd.c in the telnet.91.03.25 release follow:
*** telnetd.c.orig Wed Nov 18 08:34:47 1992
--- telnetd.c Wed Nov 18 08:34:51 1992
***************
*** 417,423 ****
#endif
#if defined(ENCRYPT)
! send_will(TELOPT_ENCRYPT, 1);
#endif
send_do(TELOPT_TTYPE, 1);
send_do(TELOPT_TSPEED, 1);
--- 417,424 ----
#endif
#if defined(ENCRYPT)
! /* send_will(TELOPT_ENCRYPT, 1); */
! send_do(TELOPT_ENCRYPT, 1);
#endif
send_do(TELOPT_TTYPE, 1);
send_do(TELOPT_TSPEED, 1);
***************
*** 425,431 ****
send_do(TELOPT_ENVIRON, 1);
while (
#if defined(ENCRYPT)
! his_do_dont_is_changing(TELOPT_ENCRYPT) ||
#endif
his_will_wont_is_changing(TELOPT_TTYPE) ||
his_will_wont_is_changing(TELOPT_TSPEED) ||
--- 426,433 ----
send_do(TELOPT_ENVIRON, 1);
while (
#if defined(ENCRYPT)
! /* his_do_dont_is_changing(TELOPT_ENCRYPT) || */
! his_will_wont_is_changing(TELOPT_ENCRYPT) ||
#endif
his_will_wont_is_changing(TELOPT_TTYPE) ||
his_will_wont_is_changing(TELOPT_TSPEED) ||
***************
*** 439,444 ****
--- 441,447 ----
* send with. If autoencrypt is not set, this will just return.
*/
if (his_state_is_will(TELOPT_ENCRYPT)) {
+ send_will(TELOPT_ENCRYPT, 1);
encrypt_wait();
}
#endif
--
Patrick John Herlihy, P.Herlihy@ccsd.uts.EDU.AU
Communications Services Branch, Ph: +61 2 330 5162
University of Technology, Sydney, Fax: +61 2 330 5562
PO Box 123, Broadway, NSW, 2007, Australia.
