1/*-
2 * Copyright (c) 1991, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <sys/cdefs.h>
35
36__FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/kerberos.c,v 1.8 2003/01/29 18:14:28 nectar Exp $");
37
38#ifndef lint
39static const char sccsid[] = "@(#)kerberos.c	8.3 (Berkeley) 5/30/95";
40#endif /* not lint */
41
42/*
43 * Copyright (C) 1990 by the Massachusetts Institute of Technology
44 *
45 * Export of this software from the United States of America is assumed
46 * to require a specific license from the United States Government.
47 * It is the responsibility of any person or organization contemplating
48 * export to obtain such a license before exporting.
49 *
50 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
51 * distribute this software and its documentation for any purpose and
52 * without fee is hereby granted, provided that the above copyright
53 * notice appear in all copies and that both that copyright notice and
54 * this permission notice appear in supporting documentation, and that
55 * the name of M.I.T. not be used in advertising or publicity pertaining
56 * to distribution of the software without specific, written prior
57 * permission.  M.I.T. makes no representations about the suitability of
58 * this software for any purpose.  It is provided "as is" without express
59 * or implied warranty.
60 */
61
62#ifdef	KRB4
63#include <sys/types.h>
64#include <arpa/telnet.h>
65#include <openssl/des.h>	/* BSD wont include this in krb.h, so we do it here */
66#include <krb.h>
67#include <stdio.h>
68#include <stdlib.h>
69#include <string.h>
70
71#include "encrypt.h"
72#include "auth.h"
73#include "misc.h"
74
75int kerberos4_cksum(unsigned char *, int);
76int kuserok(AUTH_DAT *, char *);
77
78extern int auth_debug_mode;
79
80static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
81			  		AUTHTYPE_KERBEROS_V4, };
82
83#define	KRB_AUTH	0		/* Authentication data follows */
84#define	KRB_REJECT	1		/* Rejected (reason might follow) */
85#define	KRB_ACCEPT	2		/* Accepted */
86#define	KRB_CHALLENGE	3		/* Challenge for mutual auth. */
87#define	KRB_RESPONSE	4		/* Response for mutual auth. */
88
89static	KTEXT_ST auth;
90static	char name[ANAME_SZ];
91static	AUTH_DAT adat = { 0, "", "", "", 0, {}, 0, 0, 0, { 0, "", 0 } };
92#ifdef	ENCRYPTION
93static Block	session_key	= { 0 };
94static des_key_schedule sched;
95static Block	challenge	= { 0 };
96#endif	/* ENCRYPTION */
97
98static char krb_service_name[] = "rcmd";
99static char empty[] = "";
100
101static int
102Data(Authenticator *ap, int type, const unsigned char *d, int c)
103{
104	unsigned char *p = str_data + 4;
105	const unsigned char *cd = d;
106
107	if (c == -1)
108		c = strlen(cd);
109
110	if (auth_debug_mode) {
111		printf("%s:%d: [%d] (%d)",
112			str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
113			str_data[3],
114			type, c);
115		printd(d, c);
116		printf("\r\n");
117	}
118	*p++ = ap->type;
119	*p++ = ap->way;
120	*p++ = type;
121	while (c-- > 0) {
122		if ((*p++ = *cd++) == IAC)
123			*p++ = IAC;
124	}
125	*p++ = IAC;
126	*p++ = SE;
127	if (str_data[3] == TELQUAL_IS)
128		printsub('>', &str_data[2], p - (&str_data[2]));
129	return(net_write(str_data, p - str_data));
130}
131
132int
133kerberos4_init(Authenticator *ap __unused, int server)
134{
135	FILE *fp;
136
137	if (server) {
138		str_data[3] = TELQUAL_REPLY;
139		if ((fp = fopen(KEYFILE, "r")) == NULL)
140			return(0);
141		fclose(fp);
142	} else {
143		str_data[3] = TELQUAL_IS;
144	}
145	return(1);
146}
147
148char dst_realm_buf[REALM_SZ], *dest_realm = NULL;
149int dst_realm_sz = REALM_SZ;
150
151int
152kerberos4_send(Authenticator *ap)
153{
154	KTEXT_ST lauth;
155	char instance[INST_SZ];
156	char *realm;
157	CREDENTIALS cred;
158	int r;
159
160	printf("[ Trying KERBEROS4 ... ]\n");
161	if (!UserNameRequested) {
162		if (auth_debug_mode) {
163			printf("Kerberos V4: no user name supplied\r\n");
164		}
165		return(0);
166	}
167
168	memset(instance, 0, sizeof(instance));
169
170	if ((realm = krb_get_phost(RemoteHostName)))
171		strncpy(instance, realm, sizeof(instance));
172
173	instance[sizeof(instance)-1] = '\0';
174
175	realm = dest_realm ? dest_realm : krb_realmofhost(RemoteHostName);
176
177	if (!realm) {
178		printf("Kerberos V4: no realm for %s\r\n", RemoteHostName);
179		return(0);
180	}
181	if ((r = krb_mk_req(&lauth, krb_service_name, instance, realm, 0L))) {
182		printf("mk_req failed: %s\r\n", krb_err_txt[r]);
183		return(0);
184	}
185	if ((r = krb_get_cred(krb_service_name, instance, realm, &cred))) {
186		printf("get_cred failed: %s\r\n", krb_err_txt[r]);
187		return(0);
188	}
189	if (!auth_sendname(UserNameRequested, strlen(UserNameRequested))) {
190		if (auth_debug_mode)
191			printf("Not enough room for user name\r\n");
192		return(0);
193	}
194	if (auth_debug_mode)
195		printf("Sent %d bytes of authentication data\r\n", lauth.length);
196	if (!Data(ap, KRB_AUTH, (void *)lauth.dat, lauth.length)) {
197		if (auth_debug_mode)
198			printf("Not enough room for authentication data\r\n");
199		return(0);
200	}
201#ifdef	ENCRYPTION
202	/*
203	 * If we are doing mutual authentication, get set up to send
204	 * the challenge, and verify it when the response comes back.
205	 */
206	if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
207		register int i;
208
209		des_key_sched(&cred.session, sched);
210		des_random_key(&session_key);
211		des_ecb_encrypt(&session_key, &session_key, sched, 0);
212		des_ecb_encrypt(&session_key, &challenge, sched, 0);
213		/*
214		 * Increment the challenge by 1, and encrypt it for
215		 * later comparison.
216		 */
217		for (i = 7; i >= 0; --i) {
218			register int x;
219			x = (unsigned int)challenge[i] + 1;
220			challenge[i] = x;	/* ignore overflow */
221			if (x < 256)		/* if no overflow, all done */
222				break;
223		}
224		des_ecb_encrypt(&challenge, &challenge, sched, 1);
225	}
226#endif	/* ENCRYPTION */
227
228	if (auth_debug_mode) {
229		printf("CK: %d:", kerberos4_cksum(lauth.dat, lauth.length));
230		printd(lauth.dat, lauth.length);
231		printf("\r\n");
232		printf("Sent Kerberos V4 credentials to server\r\n");
233	}
234	return(1);
235}
236
237void
238kerberos4_is(Authenticator *ap, unsigned char *data, int cnt)
239{
240#ifdef	ENCRYPTION
241	Session_Key skey;
242	Block datablock;
243#endif	/* ENCRYPTION */
244	char realm[REALM_SZ];
245	char instance[INST_SZ];
246	int r;
247
248	if (cnt-- < 1)
249		return;
250	switch (*data++) {
251	case KRB_AUTH:
252		if (krb_get_lrealm(realm, 1) != KSUCCESS) {
253			Data(ap, KRB_REJECT, "No local V4 Realm.", -1);
254			auth_finished(ap, AUTH_REJECT);
255			if (auth_debug_mode)
256				printf("No local realm\r\n");
257			return;
258		}
259		memmove((void *)auth.dat, (void *)data, auth.length = cnt);
260		if (auth_debug_mode) {
261			printf("Got %d bytes of authentication data\r\n", cnt);
262			printf("CK: %d:", kerberos4_cksum(auth.dat, auth.length));
263			printd(auth.dat, auth.length);
264			printf("\r\n");
265		}
266		instance[0] = '*'; instance[1] = 0;
267		if ((r = krb_rd_req(&auth, krb_service_name,
268				   instance, 0, &adat, empty))) {
269			if (auth_debug_mode)
270				printf("Kerberos failed him as %s\r\n", name);
271			Data(ap, KRB_REJECT, krb_err_txt[r], -1);
272			auth_finished(ap, AUTH_REJECT);
273			return;
274		}
275#ifdef	ENCRYPTION
276		memmove((void *)session_key, (void *)adat.session, sizeof(Block));
277#endif	/* ENCRYPTION */
278		krb_kntoln(&adat, name);
279
280		if (UserNameRequested && !kuserok(&adat, UserNameRequested))
281			Data(ap, KRB_ACCEPT, NULL, 0);
282		else
283			Data(ap, KRB_REJECT, "user is not authorized", -1);
284		auth_finished(ap, AUTH_USER);
285		break;
286
287	case KRB_CHALLENGE:
288#ifndef	ENCRYPTION
289		Data(ap, KRB_RESPONSE, NULL, 0);
290#else	/* ENCRYPTION */
291		if (!VALIDKEY(session_key)) {
292			/*
293			 * We don't have a valid session key, so just
294			 * send back a response with an empty session
295			 * key.
296			 */
297			Data(ap, KRB_RESPONSE, NULL, 0);
298			break;
299		}
300
301		des_key_sched(&session_key, sched);
302		memmove((void *)datablock, (void *)data, sizeof(Block));
303		/*
304		 * Take the received encrypted challenge, and encrypt
305		 * it again to get a unique session_key for the
306		 * ENCRYPT option.
307		 */
308		des_ecb_encrypt(&datablock, &session_key, sched, 1);
309		skey.type = SK_DES;
310		skey.length = 8;
311		skey.data = session_key;
312		encrypt_session_key(&skey, 1);
313		/*
314		 * Now decrypt the received encrypted challenge,
315		 * increment by one, re-encrypt it and send it back.
316		 */
317		des_ecb_encrypt(&datablock, &challenge, sched, 0);
318		for (r = 7; r >= 0; r--) {
319			register int t;
320			t = (unsigned int)challenge[r] + 1;
321			challenge[r] = t;	/* ignore overflow */
322			if (t < 256)		/* if no overflow, all done */
323				break;
324		}
325		des_ecb_encrypt(&challenge, &challenge, sched, 1);
326		Data(ap, KRB_RESPONSE, challenge, sizeof(challenge));
327#endif	/* ENCRYPTION */
328		break;
329
330	default:
331		if (auth_debug_mode)
332			printf("Unknown Kerberos option %d\r\n", data[-1]);
333		Data(ap, KRB_REJECT, NULL, 0);
334		break;
335	}
336}
337
338void
339kerberos4_reply(Authenticator *ap, unsigned char *data, int cnt)
340{
341#ifdef	ENCRYPTION
342	Session_Key skey;
343#endif	/* ENCRYPTION */
344
345	if (cnt-- < 1)
346		return;
347	switch (*data++) {
348	case KRB_REJECT:
349		if (cnt > 0) {
350			printf("[ Kerberos V4 refuses authentication because %.*s ]\r\n",
351				cnt, data);
352		} else
353			printf("[ Kerberos V4 refuses authentication ]\r\n");
354		auth_send_retry();
355		return;
356	case KRB_ACCEPT:
357		printf("[ Kerberos V4 accepts you ]\n");
358		if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
359			/*
360			 * Send over the encrypted challenge.
361		 	 */
362#ifndef	ENCRYPTION
363			Data(ap, KRB_CHALLENGE, NULL, 0);
364#else	/* ENCRYPTION */
365			Data(ap, KRB_CHALLENGE, session_key,
366						sizeof(session_key));
367			des_ecb_encrypt(&session_key, &session_key, sched, 1);
368			skey.type = SK_DES;
369			skey.length = 8;
370			skey.data = session_key;
371			encrypt_session_key(&skey, 0);
372#endif	/* ENCRYPTION */
373			return;
374		}
375		auth_finished(ap, AUTH_USER);
376		return;
377	case KRB_RESPONSE:
378#ifdef	ENCRYPTION
379		/*
380		 * Verify that the response to the challenge is correct.
381		 */
382		if ((cnt != sizeof(Block)) ||
383		    (0 != memcmp((void *)data, (void *)challenge,
384						sizeof(challenge))))
385		{
386#endif	/* ENCRYPTION */
387			printf("[ Kerberos V4 challenge failed!!! ]\r\n");
388			auth_send_retry();
389			return;
390#ifdef	ENCRYPTION
391		}
392		printf("[ Kerberos V4 challenge successful ]\r\n");
393		auth_finished(ap, AUTH_USER);
394#endif	/* ENCRYPTION */
395		break;
396	default:
397		if (auth_debug_mode)
398			printf("Unknown Kerberos option %d\r\n", data[-1]);
399		return;
400	}
401}
402
403int
404kerberos4_status(Authenticator *ap __unused, char *nam, int level)
405{
406	if (level < AUTH_USER)
407		return(level);
408
409	if (UserNameRequested && !kuserok(&adat, UserNameRequested)) {
410		strcpy(nam, UserNameRequested);
411		return(AUTH_VALID);
412	} else
413		return(AUTH_USER);
414}
415
416#define	BUMP(buf, len)		while (*(buf)) {++(buf), --(len);}
417#define	ADDC(buf, len, c)	if ((len) > 0) {*(buf)++ = (c); --(len);}
418
419void
420kerberos4_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
421{
422	char lbuf[32];
423	register int i;
424
425	buf[buflen-1] = '\0';		/* make sure its NULL terminated */
426	buflen -= 1;
427
428	switch(data[3]) {
429	case KRB_REJECT:		/* Rejected (reason might follow) */
430		strncpy((char *)buf, " REJECT ", buflen);
431		goto common;
432
433	case KRB_ACCEPT:		/* Accepted (name might follow) */
434		strncpy((char *)buf, " ACCEPT ", buflen);
435	common:
436		BUMP(buf, buflen);
437		if (cnt <= 4)
438			break;
439		ADDC(buf, buflen, '"');
440		for (i = 4; i < cnt; i++)
441			ADDC(buf, buflen, data[i]);
442		ADDC(buf, buflen, '"');
443		ADDC(buf, buflen, '\0');
444		break;
445
446	case KRB_AUTH:			/* Authentication data follows */
447		strncpy((char *)buf, " AUTH", buflen);
448		goto common2;
449
450	case KRB_CHALLENGE:
451		strncpy((char *)buf, " CHALLENGE", buflen);
452		goto common2;
453
454	case KRB_RESPONSE:
455		strncpy((char *)buf, " RESPONSE", buflen);
456		goto common2;
457
458	default:
459		sprintf(lbuf, " %d (unknown)", data[3]);
460		strncpy((char *)buf, lbuf, buflen);
461	common2:
462		BUMP(buf, buflen);
463		for (i = 4; i < cnt; i++) {
464			sprintf(lbuf, " %d", data[i]);
465			strncpy((char *)buf, lbuf, buflen);
466			BUMP(buf, buflen);
467		}
468		break;
469	}
470}
471
472int
473kerberos4_cksum(unsigned char *d, int n)
474{
475	int ck = 0;
476
477	/*
478	 * A comment is probably needed here for those not
479	 * well versed in the "C" language.  Yes, this is
480	 * supposed to be a "switch" with the body of the
481	 * "switch" being a "while" statement.  The whole
482	 * purpose of the switch is to allow us to jump into
483	 * the middle of the while() loop, and then not have
484	 * to do any more switch()s.
485	 *
486	 * Some compilers will spit out a warning message
487	 * about the loop not being entered at the top.
488	 */
489	switch (n&03)
490	while (n > 0) {
491	case 0:
492		ck ^= (int)*d++ << 24;
493		--n;
494	case 3:
495		ck ^= (int)*d++ << 16;
496		--n;
497	case 2:
498		ck ^= (int)*d++ << 8;
499		--n;
500	case 1:
501		ck ^= (int)*d++;
502		--n;
503	}
504	return(ck);
505}
506#endif
507