1/*-
2 * Copyright (c) 1991, 1993
3 *      Dave Safford.  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. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 */
30
31#include <sys/cdefs.h>
32
33__FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/sra.c,v 1.16 2002/05/06 09:48:02 markm Exp $");
34
35#ifdef	SRA
36#ifdef	ENCRYPTION
37#include <sys/types.h>
38#include <arpa/telnet.h>
39#include <pwd.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <syslog.h>
44#include <ttyent.h>
45
46#ifndef NOPAM
47#include <security/pam_appl.h>
48#else
49#include <unistd.h>
50#endif
51
52#include "auth.h"
53#include "misc.h"
54#include "encrypt.h"
55#include "pk.h"
56
57char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
58char *user, *pass, *xuser, *xpass;
59DesData ck;
60IdeaData ik;
61
62extern int auth_debug_mode;
63extern char line[];
64
65static int sra_valid = 0;
66static int passwd_sent = 0;
67
68static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
69			  		AUTHTYPE_SRA, };
70
71#define SRA_KEY	0
72#define SRA_USER 1
73#define SRA_CONTINUE 2
74#define SRA_PASS 3
75#define SRA_ACCEPT 4
76#define SRA_REJECT 5
77
78static int check_user(char *, char *);
79
80/* support routine to send out authentication message */
81static int
82Data(Authenticator *ap, int type, void *d, int c)
83{
84        unsigned char *p = str_data + 4;
85	unsigned char *cd = (unsigned char *)d;
86
87	if (c == -1)
88		c = strlen((char *)cd);
89
90        if (auth_debug_mode) {
91                printf("%s:%d: [%d] (%d)",
92                        str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
93                        str_data[3],
94                        type, c);
95                printd(d, c);
96                printf("\r\n");
97        }
98	*p++ = ap->type;
99	*p++ = ap->way;
100	*p++ = type;
101        while (c-- > 0) {
102                if ((*p++ = *cd++) == IAC)
103                        *p++ = IAC;
104        }
105        *p++ = IAC;
106        *p++ = SE;
107	if (str_data[3] == TELQUAL_IS)
108		printsub('>', &str_data[2], p - (&str_data[2]));
109        return(net_write(str_data, p - str_data));
110}
111
112int
113sra_init(Authenticator *ap __unused, int server)
114{
115	if (server)
116		str_data[3] = TELQUAL_REPLY;
117	else
118		str_data[3] = TELQUAL_IS;
119
120	user = (char *)malloc(256);
121	xuser = (char *)malloc(513);
122	pass = (char *)malloc(256);
123	xpass = (char *)malloc(513);
124
125	if (user == NULL || xuser == NULL || pass == NULL || xpass ==
126	NULL)
127		return 0; /* malloc failed */
128
129	passwd_sent = 0;
130
131	genkeys(pka,ska);
132	return(1);
133}
134
135/* client received a go-ahead for sra */
136int
137sra_send(Authenticator *ap)
138{
139	/* send PKA */
140
141	if (auth_debug_mode)
142		printf("Sent PKA to server.\r\n" );
143	printf("Trying SRA secure login:\r\n");
144	if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
145		if (auth_debug_mode)
146			printf("Not enough room for authentication data\r\n");
147		return(0);
148	}
149
150	return(1);
151}
152
153/* server received an IS -- could be SRA KEY, USER, or PASS */
154void
155sra_is(Authenticator *ap, unsigned char *data, int cnt)
156{
157	int valid;
158	Session_Key skey;
159
160	if (cnt-- < 1)
161		goto bad;
162	switch (*data++) {
163
164	case SRA_KEY:
165		if (cnt < HEXKEYBYTES) {
166			Data(ap, SRA_REJECT, (void *)0, 0);
167			auth_finished(ap, AUTH_USER);
168			if (auth_debug_mode) {
169				printf("SRA user rejected for bad PKB\r\n");
170			}
171			return;
172		}
173		if (auth_debug_mode)
174			printf("Sent pka\r\n");
175		if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
176			if (auth_debug_mode)
177				printf("Not enough room\r\n");
178			return;
179		}
180		memcpy(pkb,data,HEXKEYBYTES);
181		pkb[HEXKEYBYTES] = '\0';
182		common_key(ska,pkb,&ik,&ck);
183		return;
184
185	case SRA_USER:
186		/* decode KAB(u) */
187		if (cnt > 512) /* Attempted buffer overflow */
188			break;
189		memcpy(xuser,data,cnt);
190		xuser[cnt] = '\0';
191		pk_decode(xuser,user,&ck);
192		auth_encrypt_user(user);
193		Data(ap, SRA_CONTINUE, (void *)0, 0);
194
195		return;
196
197	case SRA_PASS:
198		if (cnt > 512) /* Attempted buffer overflow */
199			break;
200		/* decode KAB(P) */
201		memcpy(xpass,data,cnt);
202		xpass[cnt] = '\0';
203		pk_decode(xpass,pass,&ck);
204
205		/* check user's password */
206		valid = check_user(user,pass);
207
208		if(valid) {
209			Data(ap, SRA_ACCEPT, (void *)0, 0);
210			skey.data = ck;
211			skey.type = SK_DES;
212			skey.length = 8;
213			encrypt_session_key(&skey, 1);
214
215			sra_valid = 1;
216			auth_finished(ap, AUTH_VALID);
217			if (auth_debug_mode) {
218				printf("SRA user accepted\r\n");
219			}
220		}
221		else {
222			Data(ap, SRA_CONTINUE, (void *)0, 0);
223/*
224			Data(ap, SRA_REJECT, (void *)0, 0);
225			sra_valid = 0;
226			auth_finished(ap, AUTH_REJECT);
227*/
228			if (auth_debug_mode) {
229				printf("SRA user failed\r\n");
230			}
231		}
232		return;
233
234	default:
235		if (auth_debug_mode)
236			printf("Unknown SRA option %d\r\n", data[-1]);
237	}
238bad:
239	Data(ap, SRA_REJECT, 0, 0);
240	sra_valid = 0;
241	auth_finished(ap, AUTH_REJECT);
242}
243
244/* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
245void
246sra_reply(Authenticator *ap, unsigned char *data, int cnt)
247{
248	char uprompt[256],tuser[256];
249	Session_Key skey;
250	size_t i;
251
252	if (cnt-- < 1)
253		return;
254	switch (*data++) {
255
256	case SRA_KEY:
257		/* calculate common key */
258		if (cnt < HEXKEYBYTES) {
259			if (auth_debug_mode) {
260				printf("SRA user rejected for bad PKB\r\n");
261			}
262			return;
263		}
264		memcpy(pkb,data,HEXKEYBYTES);
265		pkb[HEXKEYBYTES] = '\0';
266
267		common_key(ska,pkb,&ik,&ck);
268
269	enc_user:
270
271		/* encode user */
272		memset(tuser,0,sizeof(tuser));
273		sprintf(uprompt,"User (%s): ",UserNameRequested);
274		telnet_gets(uprompt,tuser,255,1);
275		if (tuser[0] == '\n' || tuser[0] == '\r' )
276			strcpy(user,UserNameRequested);
277		else {
278			/* telnet_gets leaves the newline on */
279			for(i=0;i<sizeof(tuser);i++) {
280				if (tuser[i] == '\n') {
281					tuser[i] = '\0';
282					break;
283				}
284			}
285			strcpy(user,tuser);
286		}
287		pk_encode(user,xuser,&ck);
288
289		/* send it off */
290		if (auth_debug_mode)
291			printf("Sent KAB(U)\r\n");
292		if (!Data(ap, SRA_USER, (void *)xuser, strlen(xuser))) {
293			if (auth_debug_mode)
294				printf("Not enough room\r\n");
295			return;
296		}
297		break;
298
299	case SRA_CONTINUE:
300		if (passwd_sent) {
301			passwd_sent = 0;
302			printf("[ SRA login failed ]\r\n");
303			goto enc_user;
304		}
305		/* encode password */
306		memset(pass,0,sizeof(pass));
307		telnet_gets("Password: ",pass,255,0);
308		pk_encode(pass,xpass,&ck);
309		/* send it off */
310		if (auth_debug_mode)
311			printf("Sent KAB(P)\r\n");
312		if (!Data(ap, SRA_PASS, (void *)xpass, strlen(xpass))) {
313			if (auth_debug_mode)
314				printf("Not enough room\r\n");
315			return;
316		}
317		passwd_sent = 1;
318		break;
319
320	case SRA_REJECT:
321		printf("[ SRA refuses authentication ]\r\n");
322		printf("Trying plaintext login:\r\n");
323		auth_finished(0,AUTH_REJECT);
324		return;
325
326	case SRA_ACCEPT:
327		printf("[ SRA accepts you ]\r\n");
328		skey.data = ck;
329		skey.type = SK_DES;
330		skey.length = 8;
331		encrypt_session_key(&skey, 0);
332
333		auth_finished(ap, AUTH_VALID);
334		return;
335	default:
336		if (auth_debug_mode)
337			printf("Unknown SRA option %d\r\n", data[-1]);
338		return;
339	}
340}
341
342int
343sra_status(Authenticator *ap __unused, char *name, int level)
344{
345	if (level < AUTH_USER)
346		return(level);
347	if (UserNameRequested && sra_valid) {
348		strcpy(name, UserNameRequested);
349		return(AUTH_VALID);
350	} else
351		return(AUTH_USER);
352}
353
354#define	BUMP(buf, len)		while (*(buf)) {++(buf), --(len);}
355#define	ADDC(buf, len, c)	if ((len) > 0) {*(buf)++ = (c); --(len);}
356
357void
358sra_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
359{
360	char lbuf[32];
361	int i;
362
363	buf[buflen-1] = '\0';		/* make sure its NULL terminated */
364	buflen -= 1;
365
366	switch(data[3]) {
367
368	case SRA_CONTINUE:
369		strncpy((char *)buf, " CONTINUE ", buflen);
370		goto common;
371
372	case SRA_REJECT:		/* Rejected (reason might follow) */
373		strncpy((char *)buf, " REJECT ", buflen);
374		goto common;
375
376	case SRA_ACCEPT:		/* Accepted (name might follow) */
377		strncpy((char *)buf, " ACCEPT ", buflen);
378
379	common:
380		BUMP(buf, buflen);
381		if (cnt <= 4)
382			break;
383		ADDC(buf, buflen, '"');
384		for (i = 4; i < cnt; i++)
385			ADDC(buf, buflen, data[i]);
386		ADDC(buf, buflen, '"');
387		ADDC(buf, buflen, '\0');
388		break;
389
390	case SRA_KEY:			/* Authentication data follows */
391		strncpy((char *)buf, " KEY ", buflen);
392		goto common2;
393
394	case SRA_USER:
395		strncpy((char *)buf, " USER ", buflen);
396		goto common2;
397
398	case SRA_PASS:
399		strncpy((char *)buf, " PASS ", buflen);
400		goto common2;
401
402	default:
403		sprintf(lbuf, " %d (unknown)", data[3]);
404		strncpy((char *)buf, lbuf, buflen);
405	common2:
406		BUMP(buf, buflen);
407		for (i = 4; i < cnt; i++) {
408			sprintf(lbuf, " %d", data[i]);
409			strncpy((char *)buf, lbuf, buflen);
410			BUMP(buf, buflen);
411		}
412		break;
413	}
414}
415
416static int
417isroot(const char *usr)
418{
419	struct passwd *pwd;
420
421	if ((pwd=getpwnam(usr))==NULL)
422		return 0;
423	return (!pwd->pw_uid);
424}
425
426static int
427rootterm(char *ttyn)
428{
429	struct ttyent *t;
430
431	return ((t = getttynam(ttyn)) && t->ty_status & TTY_SECURE);
432}
433
434#ifdef NOPAM
435static int
436check_user(char *name, char *cred)
437{
438	char *cp;
439	char *xpasswd, *salt;
440
441	if (isroot(name) && !rootterm(line))
442	{
443		crypt("AA","*"); /* Waste some time to simulate success */
444		return(0);
445	}
446
447	if (pw = sgetpwnam(name)) {
448		if (pw->pw_shell == NULL) {
449			pw = (struct passwd *) NULL;
450			return(0);
451		}
452
453		salt = pw->pw_passwd;
454		xpasswd = crypt(cred, salt);
455		/* The strcmp does not catch null passwords! */
456		if (pw == NULL || *pw->pw_passwd == '\0' ||
457			strcmp(xpasswd, pw->pw_passwd)) {
458			pw = (struct passwd *) NULL;
459			return(0);
460		}
461		return(1);
462	}
463	return(0);
464}
465#else
466
467/*
468 * The following is stolen from ftpd, which stole it from the imap-uw
469 * PAM module and login.c. It is needed because we can't really
470 * "converse" with the user, having already gone to the trouble of
471 * getting their username and password through an encrypted channel.
472 */
473
474#define COPY_STRING(s) (s ? strdup(s):NULL)
475
476struct cred_t {
477	const char *uname;
478	const char *pass;
479};
480typedef struct cred_t cred_t;
481
482static int
483auth_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata)
484{
485	int i;
486	cred_t *cred = (cred_t *) appdata;
487	struct pam_response *reply =
488		malloc(sizeof(struct pam_response) * num_msg);
489
490	if (reply == NULL)
491		return PAM_BUF_ERR;
492
493	for (i = 0; i < num_msg; i++) {
494		switch (msg[i]->msg_style) {
495		case PAM_PROMPT_ECHO_ON:        /* assume want user name */
496			reply[i].resp_retcode = PAM_SUCCESS;
497			reply[i].resp = COPY_STRING(cred->uname);
498			/* PAM frees resp. */
499			break;
500		case PAM_PROMPT_ECHO_OFF:       /* assume want password */
501			reply[i].resp_retcode = PAM_SUCCESS;
502			reply[i].resp = COPY_STRING(cred->pass);
503			/* PAM frees resp. */
504			break;
505		case PAM_TEXT_INFO:
506		case PAM_ERROR_MSG:
507			reply[i].resp_retcode = PAM_SUCCESS;
508			reply[i].resp = NULL;
509			break;
510		default:                        /* unknown message style */
511			free(reply);
512			return PAM_CONV_ERR;
513		}
514	}
515
516	*resp = reply;
517	return PAM_SUCCESS;
518}
519
520/*
521 * The PAM version as a side effect may put a new username in *name.
522 */
523static int
524check_user(char *name, char *cred)
525{
526	pam_handle_t *pamh = NULL;
527	const void *item;
528	int rval;
529	int e;
530	cred_t auth_cred = { name, cred };
531	struct pam_conv conv = { &auth_conv, &auth_cred };
532
533	e = pam_start("telnetd", name, &conv, &pamh);
534	if (e != PAM_SUCCESS) {
535		syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
536		return 0;
537	}
538
539#if 0 /* Where can we find this value? */
540	e = pam_set_item(pamh, PAM_RHOST, remotehost);
541	if (e != PAM_SUCCESS) {
542		syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
543			pam_strerror(pamh, e));
544		return 0;
545	}
546#endif
547
548	e = pam_authenticate(pamh, 0);
549	switch (e) {
550	case PAM_SUCCESS:
551		/*
552		 * With PAM we support the concept of a "template"
553		 * user.  The user enters a login name which is
554		 * authenticated by PAM, usually via a remote service
555		 * such as RADIUS or TACACS+.  If authentication
556		 * succeeds, a different but related "template" name
557		 * is used for setting the credentials, shell, and
558		 * home directory.  The name the user enters need only
559		 * exist on the remote authentication server, but the
560		 * template name must be present in the local password
561		 * database.
562		 *
563		 * This is supported by two various mechanisms in the
564		 * individual modules.  However, from the application's
565		 * point of view, the template user is always passed
566		 * back as a changed value of the PAM_USER item.
567		 */
568		if ((e = pam_get_item(pamh, PAM_USER, &item)) ==
569		    PAM_SUCCESS) {
570			strcpy(name, item);
571		} else
572			syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
573			pam_strerror(pamh, e));
574		if (isroot(name) && !rootterm(line))
575			rval = 0;
576		else
577			rval = 1;
578		break;
579
580	case PAM_AUTH_ERR:
581	case PAM_USER_UNKNOWN:
582	case PAM_MAXTRIES:
583		rval = 0;
584	break;
585
586	default:
587		syslog(LOG_ERR, "auth_pam: %s", pam_strerror(pamh, e));
588		rval = 0;
589		break;
590	}
591
592	if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
593		syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
594		rval = 0;
595	}
596	return rval;
597}
598
599#endif
600
601#endif /* ENCRYPTION */
602#endif /* SRA */
603