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telnetd/libtelnet/kerberos.c

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/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#ifndef lint
static const char sccsid[] = "@(#)kerberos.c 8.3 (Berkeley) 5/30/95";
#endif /* not lint */
/*
* Copyright (C) 1990 by the Massachusetts Institute of Technology
*
* Export of this software from the United States of America is assumed
* to require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#ifdef KRB4
#include <sys/types.h>
#include "arpa/telnet.h"
#include <openssl/des.h> /* BSD wont include this in krb.h, so we do it here */
#include <krb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "encrypt.h"
#include "auth.h"
#include "misc.h"
int kerberos4_cksum(unsigned char *, int);
int kuserok(AUTH_DAT *, char *);
extern int auth_debug_mode;
static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
AUTHTYPE_KERBEROS_V4, };
#define KRB_AUTH 0 /* Authentication data follows */
#define KRB_REJECT 1 /* Rejected (reason might follow) */
#define KRB_ACCEPT 2 /* Accepted */
#define KRB_CHALLENGE 3 /* Challenge for mutual auth. */
#define KRB_RESPONSE 4 /* Response for mutual auth. */
static KTEXT_ST auth;
static char name[ANAME_SZ];
static AUTH_DAT adat = { 0, "", "", "", 0, {}, 0, 0, 0, { 0, "", 0 } };
#ifdef ENCRYPTION
static Block session_key = { 0 };
static des_key_schedule sched;
static Block challenge = { 0 };
#endif /* ENCRYPTION */
static char krb_service_name[] = "rcmd";
static char empty[] = "";
static int
Data(Authenticator *ap, int type, const unsigned char *d, int c)
{
unsigned char *p = str_data + 4;
const unsigned char *cd = d;
if (c == -1)
c = strlen(cd);
if (auth_debug_mode) {
printf("%s:%d: [%d] (%d)",
str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
str_data[3],
type, c);
printd(d, c);
printf("\r\n");
}
*p++ = ap->type;
*p++ = ap->way;
*p++ = type;
while (c-- > 0) {
if ((*p++ = *cd++) == IAC)
*p++ = IAC;
}
*p++ = IAC;
*p++ = SE;
if (str_data[3] == TELQUAL_IS)
printsub('>', &str_data[2], p - (&str_data[2]));
return(net_write(str_data, p - str_data));
}
int
kerberos4_init(Authenticator *ap __unused, int server)
{
FILE *fp;
if (server) {
str_data[3] = TELQUAL_REPLY;
if ((fp = fopen(KEYFILE, "r")) == NULL)
return(0);
fclose(fp);
} else {
str_data[3] = TELQUAL_IS;
}
return(1);
}
char dst_realm_buf[REALM_SZ], *dest_realm = NULL;
int dst_realm_sz = REALM_SZ;
int
kerberos4_send(Authenticator *ap)
{
KTEXT_ST lauth;
char instance[INST_SZ];
char *realm;
CREDENTIALS cred;
int r;
printf("[ Trying KERBEROS4 ... ]\n");
if (!UserNameRequested) {
if (auth_debug_mode) {
printf("Kerberos V4: no user name supplied\r\n");
}
return(0);
}
memset(instance, 0, sizeof(instance));
if ((realm = krb_get_phost(RemoteHostName)))
strncpy(instance, realm, sizeof(instance));
instance[sizeof(instance)-1] = '\0';
realm = dest_realm ? dest_realm : krb_realmofhost(RemoteHostName);
if (!realm) {
printf("Kerberos V4: no realm for %s\r\n", RemoteHostName);
return(0);
}
if ((r = krb_mk_req(&lauth, krb_service_name, instance, realm, 0L))) {
printf("mk_req failed: %s\r\n", krb_err_txt[r]);
return(0);
}
if ((r = krb_get_cred(krb_service_name, instance, realm, &cred))) {
printf("get_cred failed: %s\r\n", krb_err_txt[r]);
return(0);
}
if (!auth_sendname(UserNameRequested, strlen(UserNameRequested))) {
if (auth_debug_mode)
printf("Not enough room for user name\r\n");
return(0);
}
if (auth_debug_mode)
printf("Sent %d bytes of authentication data\r\n", lauth.length);
if (!Data(ap, KRB_AUTH, (void *)lauth.dat, lauth.length)) {
if (auth_debug_mode)
printf("Not enough room for authentication data\r\n");
return(0);
}
#ifdef ENCRYPTION
/*
* If we are doing mutual authentication, get set up to send
* the challenge, and verify it when the response comes back.
*/
if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
register int i;
des_key_sched(&cred.session, sched);
des_random_key(&session_key);
des_ecb_encrypt(&session_key, &session_key, sched, 0);
des_ecb_encrypt(&session_key, &challenge, sched, 0);
/*
* Increment the challenge by 1, and encrypt it for
* later comparison.
*/
for (i = 7; i >= 0; --i) {
register int x;
x = (unsigned int)challenge[i] + 1;
challenge[i] = x; /* ignore overflow */
if (x < 256) /* if no overflow, all done */
break;
}
des_ecb_encrypt(&challenge, &challenge, sched, 1);
}
#endif /* ENCRYPTION */
if (auth_debug_mode) {
printf("CK: %d:", kerberos4_cksum(lauth.dat, lauth.length));
printd(lauth.dat, lauth.length);
printf("\r\n");
printf("Sent Kerberos V4 credentials to server\r\n");
}
return(1);
}
void
kerberos4_is(Authenticator *ap, unsigned char *data, int cnt)
{
#ifdef ENCRYPTION
Session_Key skey;
Block datablock;
#endif /* ENCRYPTION */
char realm[REALM_SZ];
char instance[INST_SZ];
int r;
if (cnt-- < 1)
return;
switch (*data++) {
case KRB_AUTH:
if (krb_get_lrealm(realm, 1) != KSUCCESS) {
Data(ap, KRB_REJECT, "No local V4 Realm.", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("No local realm\r\n");
return;
}
memmove((void *)auth.dat, (void *)data, auth.length = cnt);
if (auth_debug_mode) {
printf("Got %d bytes of authentication data\r\n", cnt);
printf("CK: %d:", kerberos4_cksum(auth.dat, auth.length));
printd(auth.dat, auth.length);
printf("\r\n");
}
instance[0] = '*'; instance[1] = 0;
if ((r = krb_rd_req(&auth, krb_service_name,
instance, 0, &adat, empty))) {
if (auth_debug_mode)
printf("Kerberos failed him as %s\r\n", name);
Data(ap, KRB_REJECT, krb_err_txt[r], -1);
auth_finished(ap, AUTH_REJECT);
return;
}
#ifdef ENCRYPTION
memmove((void *)session_key, (void *)adat.session, sizeof(Block));
#endif /* ENCRYPTION */
krb_kntoln(&adat, name);
if (UserNameRequested && !kuserok(&adat, UserNameRequested))
Data(ap, KRB_ACCEPT, NULL, 0);
else
Data(ap, KRB_REJECT, "user is not authorized", -1);
auth_finished(ap, AUTH_USER);
break;
case KRB_CHALLENGE:
#ifndef ENCRYPTION
Data(ap, KRB_RESPONSE, NULL, 0);
#else /* ENCRYPTION */
if (!VALIDKEY(session_key)) {
/*
* We don't have a valid session key, so just
* send back a response with an empty session
* key.
*/
Data(ap, KRB_RESPONSE, NULL, 0);
break;
}
des_key_sched(&session_key, sched);
memmove((void *)datablock, (void *)data, sizeof(Block));
/*
* Take the received encrypted challenge, and encrypt
* it again to get a unique session_key for the
* ENCRYPT option.
*/
des_ecb_encrypt(&datablock, &session_key, sched, 1);
skey.type = SK_DES;
skey.length = 8;
skey.data = session_key;
encrypt_session_key(&skey, 1);
/*
* Now decrypt the received encrypted challenge,
* increment by one, re-encrypt it and send it back.
*/
des_ecb_encrypt(&datablock, &challenge, sched, 0);
for (r = 7; r >= 0; r--) {
register int t;
t = (unsigned int)challenge[r] + 1;
challenge[r] = t; /* ignore overflow */
if (t < 256) /* if no overflow, all done */
break;
}
des_ecb_encrypt(&challenge, &challenge, sched, 1);
Data(ap, KRB_RESPONSE, challenge, sizeof(challenge));
#endif /* ENCRYPTION */
break;
default:
if (auth_debug_mode)
printf("Unknown Kerberos option %d\r\n", data[-1]);
Data(ap, KRB_REJECT, NULL, 0);
break;
}
}
void
kerberos4_reply(Authenticator *ap, unsigned char *data, int cnt)
{
#ifdef ENCRYPTION
Session_Key skey;
#endif /* ENCRYPTION */
if (cnt-- < 1)
return;
switch (*data++) {
case KRB_REJECT:
if (cnt > 0) {
printf("[ Kerberos V4 refuses authentication because %.*s ]\r\n",
cnt, data);
} else
printf("[ Kerberos V4 refuses authentication ]\r\n");
auth_send_retry();
return;
case KRB_ACCEPT:
printf("[ Kerberos V4 accepts you ]\n");
if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
/*
* Send over the encrypted challenge.
*/
#ifndef ENCRYPTION
Data(ap, KRB_CHALLENGE, NULL, 0);
#else /* ENCRYPTION */
Data(ap, KRB_CHALLENGE, session_key,
sizeof(session_key));
des_ecb_encrypt(&session_key, &session_key, sched, 1);
skey.type = SK_DES;
skey.length = 8;
skey.data = session_key;
encrypt_session_key(&skey, 0);
#endif /* ENCRYPTION */
return;
}
auth_finished(ap, AUTH_USER);
return;
case KRB_RESPONSE:
#ifdef ENCRYPTION
/*
* Verify that the response to the challenge is correct.
*/
if ((cnt != sizeof(Block)) ||
(0 != memcmp((void *)data, (void *)challenge,
sizeof(challenge))))
{
#endif /* ENCRYPTION */
printf("[ Kerberos V4 challenge failed!!! ]\r\n");
auth_send_retry();
return;
#ifdef ENCRYPTION
}
printf("[ Kerberos V4 challenge successful ]\r\n");
auth_finished(ap, AUTH_USER);
#endif /* ENCRYPTION */
break;
default:
if (auth_debug_mode)
printf("Unknown Kerberos option %d\r\n", data[-1]);
return;
}
}
int
kerberos4_status(Authenticator *ap __unused, char *nam, int level)
{
if (level < AUTH_USER)
return(level);
if (UserNameRequested && !kuserok(&adat, UserNameRequested)) {
strcpy(nam, UserNameRequested);
return(AUTH_VALID);
} else
return(AUTH_USER);
}
#define BUMP(buf, len) while (*(buf)) {++(buf), --(len);}
#define ADDC(buf, len, c) if ((len) > 0) {*(buf)++ = (c); --(len);}
void
kerberos4_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
char lbuf[32];
register int i;
buf[buflen-1] = '\0'; /* make sure its NULL terminated */
buflen -= 1;
switch(data[3]) {
case KRB_REJECT: /* Rejected (reason might follow) */
strncpy((char *)buf, " REJECT ", buflen);
goto common;
case KRB_ACCEPT: /* Accepted (name might follow) */
strncpy((char *)buf, " ACCEPT ", buflen);
common:
BUMP(buf, buflen);
if (cnt <= 4)
break;
ADDC(buf, buflen, '"');
for (i = 4; i < cnt; i++)
ADDC(buf, buflen, data[i]);
ADDC(buf, buflen, '"');
ADDC(buf, buflen, '\0');
break;
case KRB_AUTH: /* Authentication data follows */
strncpy((char *)buf, " AUTH", buflen);
goto common2;
case KRB_CHALLENGE:
strncpy((char *)buf, " CHALLENGE", buflen);
goto common2;
case KRB_RESPONSE:
strncpy((char *)buf, " RESPONSE", buflen);
goto common2;
default:
sprintf(lbuf, " %d (unknown)", data[3]);
strncpy((char *)buf, lbuf, buflen);
common2:
BUMP(buf, buflen);
for (i = 4; i < cnt; i++) {
sprintf(lbuf, " %d", data[i]);
strncpy((char *)buf, lbuf, buflen);
BUMP(buf, buflen);
}
break;
}
}
int
kerberos4_cksum(unsigned char *d, int n)
{
int ck = 0;
/*
* A comment is probably needed here for those not
* well versed in the "C" language. Yes, this is
* supposed to be a "switch" with the body of the
* "switch" being a "while" statement. The whole
* purpose of the switch is to allow us to jump into
* the middle of the while() loop, and then not have
* to do any more switch()s.
*
* Some compilers will spit out a warning message
* about the loop not being entered at the top.
*/
switch (n&03)
while (n > 0) {
case 0:
ck ^= (int)*d++ << 24;
--n;
case 3:
ck ^= (int)*d++ << 16;
--n;
case 2:
ck ^= (int)*d++ << 8;
--n;
case 1:
ck ^= (int)*d++;
--n;
}
return(ck);
}
#endif
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