Telnet Encryption (using Kerberos V4) SECURITY HOLE

[Theodore Ts'o <[e-mail]>]

-----BEGIN PGP SIGNED MESSAGE-----

We have discovered a serious security problem found in the Berkeley
telnet client.  This bug only affects telnet clients which provide
support for the experimental telnet encryption option using the
Kerberos V4 authentication.  All known, released versions of the BSD
telnet that support Kerberos V4 authentication and encryption are
affected by this bug.

It is recommended that all sites who use encrypted telnet in
conjuction with Kerberos V4 apply this patch immediately.

This patch, along with the domestic version of the most recently
released telnet sources from Berkeley, are available via anonymous ftp
from net-dist.mit.edu in the directory /pub/telnet.  

The patch (which is also included in this message) can be found in the
file /pub/telnet/telnet.patch.  The file /pub/telnet/telnet.patch.sig
contains a detached PGP signature of this file.

Users of NCSA Telnet should upgrade to the NCSA telnet 2.6.1d4, which
is available via from ftp.ncsa.uiuc.edu in the directory
/Mac/Telnet/Telnet2.6/prerelease/d4.

Customers of ftp Software with an encrypting telnet (provided in the
PC/TCP or OnNet packages) should call the ftp technical support line
at 1-800-282-4387 and ask for the "tn encrypt patch".

If you have an encrypting telnet from some other vendor, please
contact that vendor for information regarding how to get a fixed
version.


					Theodore Ts'o
					[e-mail]
					February 15, 1995


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#! /bin/sh
# This is a shell archive.  Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file".  To overwrite existing
# files, type "sh file -c".  You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g..  If this archive is complete, you
# will see the following message at the end:
#		"End of shell archive."
# Contents:  telnet.patch telnet.patch.sig
# Wrapped by tytso@dcl on Wed Feb 15 17:01:03 1995
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'telnet.patch' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'telnet.patch'\"
else
echo shar: Extracting \"'telnet.patch'\" \(4877 characters\)
sed "s/^X//" >'telnet.patch' <<'END_OF_FILE'
XIndex: auth.c
X===================================================================
XRCS file: /mit/krb5/.cvsroot/src/appl/telnet/libtelnet/auth.c,v
Xretrieving revision 5.5
Xretrieving revision 5.7
Xdiff -u -r5.5 -r5.7
X--- auth.c	1994/08/18 21:06:45	5.5
X+++ auth.c	1994/11/08 04:39:02	5.7
X@@ -244,7 +244,7 @@
X {
X 	register int x;
X 
X-	if (strcasecmp(type, AUTHTYPE_NAME(0))) {
X+	if (!strcasecmp(type, AUTHTYPE_NAME(0))) {
X 		*maskp = -1;
X 		return(1);
X 	}
X@@ -260,14 +260,14 @@
X 
X 	int
X auth_enable(type)
X-	int type;
X+	char * type;
X {
X 	return(auth_onoff(type, 1));
X }
X 
X 	int
X auth_disable(type)
X-	int type;
X+	char * type;
X {
X 	return(auth_onoff(type, 0));
X }
X@@ -277,15 +277,20 @@
X 	char *type;
X 	int on;
X {
X-	int mask = -1;
X+	int i, mask = -1;
X 	Authenticator *ap;
X 
X 	if (!strcasecmp(type, "?") || !strcasecmp(type, "help")) {
X                 printf("auth %s 'type'\n", on ? "enable" : "disable");
X 		printf("Where 'type' is one of:\n");
X 		printf("\t%s\n", AUTHTYPE_NAME(0));
X-		for (ap = authenticators; ap->type; ap++)
X+		mask = 0;
X+		for (ap = authenticators; ap->type; ap++) {
X+			if ((mask & (i = typemask(ap->type))) != 0)
X+				continue;
X+			mask |= i;
X 			printf("\t%s\n", AUTHTYPE_NAME(ap->type));
X+		}
X 		return(0);
X 	}
X 
X@@ -293,7 +298,6 @@
X 		printf("%s: invalid authentication type\n", type);
X 		return(0);
X 	}
X-	mask = getauthmask(type, &mask);
X 	if (on)
X 		i_wont_support &= ~mask;
X 	else
X@@ -317,16 +321,22 @@
X auth_status()
X {
X 	Authenticator *ap;
X+	int i, mask;
X 
X 	if (i_wont_support == -1)
X 		printf("Authentication disabled\n");
X 	else
X 		printf("Authentication enabled\n");
X 
X-	for (ap = authenticators; ap->type; ap++)
X+	mask = 0;
X+	for (ap = authenticators; ap->type; ap++) {
X+		if ((mask & (i = typemask(ap->type))) != 0)
X+			continue;
X+		mask |= i;
X 		printf("%s: %s\n", AUTHTYPE_NAME(ap->type),
X 			(i_wont_support & typemask(ap->type)) ?
X 					"disabled" : "enabled");
X+	}
X 	return(1);
X }
X 
XIndex: kerberos.c
X===================================================================
XRCS file: /mit/krb5/.cvsroot/src/appl/telnet/libtelnet/kerberos.c,v
Xretrieving revision 5.5
Xretrieving revision 5.8
Xdiff -u -r5.5 -r5.8
X--- kerberos.c	1994/08/18 21:07:02	5.5
X+++ kerberos.c	1994/11/14 21:33:58	5.8
X@@ -225,9 +225,10 @@
X 		register int i;
X 
X 		des_key_sched(cred.session, sched);
X-		des_set_random_generator_seed(cred.session);
X-		des_new_random_key(challenge);
X-		des_ecb_encrypt(challenge, session_key, sched, 1);
X+		des_init_random_number_generator(cred.session);
X+		des_new_random_key(session_key);
X+		des_ecb_encrypt(session_key, session_key, sched, 0);
X+		des_ecb_encrypt(session_key, challenge, sched, 0);
X 		/*
X 		 * Increment the challenge by 1, and encrypt it for
X 		 * later comparison.
X@@ -320,6 +321,11 @@
X 			break;
X 		}
X 
X+		/*
X+		 * Initialize the random number generator since it's
X+		 * used later on by the encryption routine.
X+		 */
X+		des_init_random_number_generator(session_key);
X 		des_key_sched(session_key, sched);
X 		memcpy((void *)datablock, (void *)data, sizeof(Block));
X 		/*
X@@ -337,7 +343,7 @@
X 		 * increment by one, re-encrypt it and send it back.
X 		 */
X 		des_ecb_encrypt(datablock, challenge, sched, 0);
X-		for (r = 7; r >= 0; r++) {
X+		for (r = 7; r >= 0; r--) {
X 			register int t;
X 			t = (unsigned int)challenge[r] + 1;
X 			challenge[r] = t;	/* ignore overflow */
X
XIndex: commands.c
X===================================================================
XRCS file: /mit/krb5/.cvsroot/src/appl/telnet/telnet/commands.c,v
Xretrieving revision 5.14
Xretrieving revision 5.16
Xdiff -u -r5.14 -r5.16
X--- commands.c	1994/08/18 21:07:37	5.14
X+++ commands.c	1994/11/08 06:42:49	5.16
X@@ -1919,8 +1919,8 @@
X };
X 
X extern int
X-	auth_enable P((int)),
X-	auth_disable P((int)),
X+	auth_enable P((char *)),
X+	auth_disable P((char *)),
X 	auth_status P((void));
X static int
X 	auth_help P((void));
X@@ -1959,6 +1959,12 @@
X {
X     struct authlist *c;
X 
X+    if (argc < 2) {
X+      fprintf(stderr,
X+          "Need an argument to 'auth' command.  'auth ?' for help.\n");
X+      return 0;
X+    }
X+
X     c = (struct authlist *)
X 		genget(argv[1], (char **) AuthList, sizeof(struct authlist));
X     if (c == 0) {
X@@ -2015,7 +2021,7 @@
X 						EncryptEnable, 1, 1, 2 },
X     { "disable", "Disable encryption. ('encrypt enable ?' for more)",
X 						EncryptDisable, 0, 1, 2 },
X-    { "type", "Set encryptiong type. ('encrypt type ?' for more)",
X+    { "type", "Set encryption type. ('encrypt type ?' for more)",
X 						EncryptType, 0, 1, 1 },
X     { "start", "Start encryption. ('encrypt start ?' for more)",
X 						EncryptStart, 1, 0, 1 },
X@@ -2058,6 +2064,12 @@
X     char *argv[];
X {
X     struct encryptlist *c;
X+
X+    if (argc < 2) {
X+	fprintf(stderr,
X+	    "Need an argument to 'encrypt' command.  'encrypt ?' for help.\n");
X+	return 0;
X+    }
X 
X     c = (struct encryptlist *)
X 		genget(argv[1], (char **) EncryptList, sizeof(struct encryptlist));
END_OF_FILE
if test 4877 -ne `wc -c <'telnet.patch'`; then
    echo shar: \"'telnet.patch'\" unpacked with wrong size!
fi
# end of 'telnet.patch'
fi
if test -f 'telnet.patch.sig' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'telnet.patch.sig'\"
else
echo shar: Extracting \"'telnet.patch.sig'\" \(284 characters\)
sed "s/^X//" >'telnet.patch.sig' <<'END_OF_FILE'
X-----BEGIN PGP MESSAGE-----
XVersion: 2.6.1
X
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X-----END PGP MESSAGE-----
END_OF_FILE
if test 284 -ne `wc -c <'telnet.patch.sig'`; then
    echo shar: \"'telnet.patch.sig'\" unpacked with wrong size!
fi
# end of 'telnet.patch.sig'
fi
echo shar: End of shell archive.
exit 0