summaryrefslogtreecommitdiff
path: root/auth2.c
blob: 7769046fbcac75d508253a283fb63fe2ef8ae77c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
/*
 * Copyright (c) 2000 Markus Friedl.  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 Markus Friedl.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 "includes.h"
RCSID("$OpenBSD: auth2.c,v 1.13 2000/08/20 18:42:40 millert Exp $");

#include <openssl/dsa.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>

#include "xmalloc.h"
#include "rsa.h"
#include "ssh.h"
#include "pty.h"
#include "packet.h"
#include "buffer.h"
#include "cipher.h"
#include "servconf.h"
#include "compat.h"
#include "channels.h"
#include "bufaux.h"
#include "ssh2.h"
#include "auth.h"
#include "session.h"
#include "dispatch.h"
#include "auth.h"
#include "key.h"
#include "kex.h"

#include "dsa.h"
#include "uidswap.h"
#include "auth-options.h"

#ifdef HAVE_OSF_SIA
# include <sia.h>
# include <siad.h>
#endif

/* import */
extern ServerOptions options;
extern unsigned char *session_id2;
extern int session_id2_len;

/* protocol */

void	input_service_request(int type, int plen);
void	input_userauth_request(int type, int plen);
void	protocol_error(int type, int plen);

/* auth */
int	ssh2_auth_none(struct passwd *pw);
int	ssh2_auth_password(struct passwd *pw);
int  	ssh2_auth_pubkey(struct passwd *pw, char *service);

/* helper */
struct passwd*	 auth_set_user(char *u, char *s);
int	user_dsa_key_allowed(struct passwd *pw, Key *key);

typedef struct Authctxt Authctxt;
struct Authctxt {
	char *user;
	char *service;
	struct passwd pw;
	int valid;
};
static Authctxt	*authctxt = NULL;
static int userauth_success = 0;

/*
 * loop until userauth_success == TRUE
 */

void
do_authentication2()
{
	/* turn off skey/kerberos, not supported by SSH2 */
#ifdef SKEY
	options.skey_authentication = 0;
#endif
#ifdef KRB4
	options.kerberos_authentication = 0;
#endif

	dispatch_init(&protocol_error);
	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
	dispatch_run(DISPATCH_BLOCK, &userauth_success);
	do_authenticated2();
}

void
protocol_error(int type, int plen)
{
	log("auth: protocol error: type %d plen %d", type, plen);
	packet_start(SSH2_MSG_UNIMPLEMENTED);
	packet_put_int(0);
	packet_send();
	packet_write_wait();
}

void
input_service_request(int type, int plen)
{
	unsigned int len;
	int accept = 0;
	char *service = packet_get_string(&len);
	packet_done();

	if (strcmp(service, "ssh-userauth") == 0) {
		if (!userauth_success) {
			accept = 1;
			/* now we can handle user-auth requests */
			dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
		}
	}
	/* XXX all other service requests are denied */

	if (accept) {
		packet_start(SSH2_MSG_SERVICE_ACCEPT);
		packet_put_cstring(service);
		packet_send();
		packet_write_wait();
	} else {
		debug("bad service request %s", service);
		packet_disconnect("bad service request %s", service);
	}
	xfree(service);
}

void
input_userauth_request(int type, int plen)
{
	static void (*authlog) (const char *fmt,...) = verbose;
	static int attempt = 0;
	unsigned int len;
	int authenticated = 0;
	char *user, *service, *method, *authmsg = NULL;
	struct passwd *pw;
#ifdef WITH_AIXAUTHENTICATE
	extern char *aixloginmsg;
#endif /* WITH_AIXAUTHENTICATE */

	user = packet_get_string(&len);
	service = packet_get_string(&len);
	method = packet_get_string(&len);
	if (++attempt == AUTH_FAIL_MAX) {
#ifdef WITH_AIXAUTHENTICATE 
		loginfailed(user,get_canonical_hostname(),"ssh");
#endif /* WITH_AIXAUTHENTICATE */
		packet_disconnect("too many failed userauth_requests");
	}
	debug("userauth-request for user %s service %s method %s", user, service, method);

	/* XXX we only allow the ssh-connection service */
	pw = auth_set_user(user, service);
	if (pw && strcmp(service, "ssh-connection")==0) {
		if (strcmp(method, "none") == 0) {
			authenticated =	ssh2_auth_none(pw);
		} else if (strcmp(method, "password") == 0) {
			authenticated =	ssh2_auth_password(pw);
		} else if (strcmp(method, "publickey") == 0) {
			authenticated =	ssh2_auth_pubkey(pw, service);
		}
	}
	if (authenticated && pw && pw->pw_uid == 0 && !options.permit_root_login) {
		authenticated = 0;
		log("ROOT LOGIN REFUSED FROM %.200s",
		    get_canonical_hostname());
	}

#ifdef USE_PAM
		if (authenticated && !do_pam_account(pw->pw_name, NULL))
			authenticated = 0;
#endif /* USE_PAM */

	/* Raise logging level */
	if (authenticated == 1 ||
	    attempt == AUTH_FAIL_LOG ||
	    strcmp(method, "password") == 0)
		authlog = log;

	/* Log before sending the reply */
	if (authenticated == 1) {
		authmsg = "Accepted";
	} else if (authenticated == 0) {
		authmsg = "Failed";
	} else {
		authmsg = "Postponed";
	}
	authlog("%s %s for %.200s from %.200s port %d ssh2",
		authmsg,
		method,
		pw && pw->pw_uid == 0 ? "ROOT" : user,
		get_remote_ipaddr(),
		get_remote_port());

	/* XXX todo: check if multiple auth methods are needed */
	if (authenticated == 1) {
#ifdef WITH_AIXAUTHENTICATE
		/* We don't have a pty yet, so just label the line as "ssh" */
		if (loginsuccess(user,get_canonical_hostname(),"ssh",
				&aixloginmsg) < 0)
			aixloginmsg = NULL;
#endif /* WITH_AIXAUTHENTICATE */
		/* turn off userauth */
		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
		packet_send();
		packet_write_wait();
		/* now we can break out */
		userauth_success = 1;
	} else if (authenticated == 0) {
		packet_start(SSH2_MSG_USERAUTH_FAILURE);
		packet_put_cstring("publickey,password");	/* XXX dynamic */
		packet_put_char(0);				/* XXX partial success, unused */
		packet_send();
		packet_write_wait();
	}

	xfree(service);
	xfree(user);
	xfree(method);
}

int
ssh2_auth_none(struct passwd *pw)
{
#ifdef HAVE_OSF_SIA
	extern int saved_argc;
	extern char **saved_argv;
#endif

	packet_done();

#ifdef USE_PAM
	return auth_pam_password(pw, "");
#elif defined(HAVE_OSF_SIA)
	return(sia_validate_user(NULL, saved_argc, saved_argv, 
		get_canonical_hostname(), pw->pw_name, NULL, 0, NULL, 
		"") == SIASUCCESS);
#else /* !HAVE_OSF_SIA && !USE_PAM */
	return auth_password(pw, "");
#endif /* USE_PAM */
}
int
ssh2_auth_password(struct passwd *pw)
{
	char *password;
	int authenticated = 0;
	int change;
	unsigned int len;
#ifdef HAVE_OSF_SIA
	extern int saved_argc;
	extern char **saved_argv;
#endif
	change = packet_get_char();
	if (change)
		log("password change not supported");
	password = packet_get_string(&len);
	packet_done();
	if (options.password_authentication &&
#ifdef USE_PAM
	    auth_pam_password(pw, password) == 1)
#elif defined(HAVE_OSF_SIA)
	    sia_validate_user(NULL, saved_argc, saved_argv, 
		 	get_canonical_hostname(), pw->pw_name, NULL, 0, 
			NULL, password) == SIASUCCESS)
#else /* !USE_PAM && !HAVE_OSF_SIA */
	    auth_password(pw, password) == 1)
#endif /* USE_PAM */
		authenticated = 1;
	memset(password, 0, len);
	xfree(password);
	return authenticated;
}
int
ssh2_auth_pubkey(struct passwd *pw, char *service)
{
	Buffer b;
	Key *key;
	char *pkalg, *pkblob, *sig;
	unsigned int alen, blen, slen;
	int have_sig;
	int authenticated = 0;

	if (options.dsa_authentication == 0) {
		debug("pubkey auth disabled");
		return 0;
	}
	have_sig = packet_get_char();
	pkalg = packet_get_string(&alen);
	if (strcmp(pkalg, KEX_DSS) != 0) {
		xfree(pkalg);
		log("bad pkalg %s", pkalg);	/*XXX*/
		return 0;
	}
	pkblob = packet_get_string(&blen);
	key = dsa_key_from_blob(pkblob, blen);
	if (key != NULL) {
		if (have_sig) {
			sig = packet_get_string(&slen);
			packet_done();
			buffer_init(&b);
			if (datafellows & SSH_COMPAT_SESSIONID_ENCODING) {
				buffer_put_string(&b, session_id2, session_id2_len);
			} else {
				buffer_append(&b, session_id2, session_id2_len);
			}
			/* reconstruct packet */
			buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
			buffer_put_cstring(&b, pw->pw_name);
			buffer_put_cstring(&b,
			    datafellows & SSH_BUG_PUBKEYAUTH ?
			    "ssh-userauth" :
			    service);
			buffer_put_cstring(&b, "publickey");
			buffer_put_char(&b, have_sig);
			buffer_put_cstring(&b, KEX_DSS);
			buffer_put_string(&b, pkblob, blen);
#ifdef DEBUG_DSS
			buffer_dump(&b);
#endif
			/* test for correct signature */
			if (user_dsa_key_allowed(pw, key) &&
			    dsa_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
				authenticated = 1;
			buffer_clear(&b);
			xfree(sig);
		} else {
			packet_done();
			debug("test key...");
			/* test whether pkalg/pkblob are acceptable */
			/* XXX fake reply and always send PK_OK ? */
			/*
			 * XXX this allows testing whether a user is allowed
			 * to login: if you happen to have a valid pubkey this
			 * message is sent. the message is NEVER sent at all
			 * if a user is not allowed to login. is this an
			 * issue? -markus
			 */
			if (user_dsa_key_allowed(pw, key)) {
				packet_start(SSH2_MSG_USERAUTH_PK_OK);
				packet_put_string(pkalg, alen);
				packet_put_string(pkblob, blen);
				packet_send();
				packet_write_wait();
				authenticated = -1;
			}
		}
		key_free(key);
	}
	xfree(pkalg);
	xfree(pkblob);
	return authenticated;
}

/* set and get current user */

struct passwd*
auth_get_user(void)
{
	return (authctxt != NULL && authctxt->valid) ? &authctxt->pw : NULL;
}

struct passwd*
auth_set_user(char *u, char *s)
{
	struct passwd *pw, *copy;

	if (authctxt == NULL) {
		authctxt = xmalloc(sizeof(*authctxt));
		authctxt->valid = 0;
		authctxt->user = xstrdup(u);
		authctxt->service = xstrdup(s);
		setproctitle("%s", u);
		pw = getpwnam(u);
		if (!pw || !allowed_user(pw)) {
			log("auth_set_user: illegal user %s", u);
			return NULL;
		}
#ifdef USE_PAM
		start_pam(pw);
#endif
		copy = &authctxt->pw;
		memset(copy, 0, sizeof(*copy));
		copy->pw_name = xstrdup(pw->pw_name);
		copy->pw_passwd = xstrdup(pw->pw_passwd);
		copy->pw_uid = pw->pw_uid;
		copy->pw_gid = pw->pw_gid;
#ifdef HAVE_PW_CLASS_IN_PASSWD
		copy->pw_class = xstrdup(pw->pw_class);
#endif
		copy->pw_dir = xstrdup(pw->pw_dir);
		copy->pw_shell = xstrdup(pw->pw_shell);
		authctxt->valid = 1;
	} else {
		if (strcmp(u, authctxt->user) != 0 ||
		    strcmp(s, authctxt->service) != 0) {
			log("auth_set_user: missmatch: (%s,%s)!=(%s,%s)",
			    u, s, authctxt->user, authctxt->service);
			return NULL;
		}
	}
	return auth_get_user();
}

/* return 1 if user allows given key */
int
user_dsa_key_allowed(struct passwd *pw, Key *key)
{
	char line[8192], file[1024];
	int found_key = 0;
	unsigned int bits = -1;
	FILE *f;
	unsigned long linenum = 0;
	struct stat st;
	Key *found;

	/* Temporarily use the user's uid. */
	temporarily_use_uid(pw->pw_uid);

	/* The authorized keys. */
	snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
	    SSH_USER_PERMITTED_KEYS2);

	/* Fail quietly if file does not exist */
	if (stat(file, &st) < 0) {
		/* Restore the privileged uid. */
		restore_uid();
		return 0;
	}
	/* Open the file containing the authorized keys. */
	f = fopen(file, "r");
	if (!f) {
		/* Restore the privileged uid. */
		restore_uid();
		return 0;
	}
	if (options.strict_modes) {
		int fail = 0;
		char buf[1024];
		/* Check open file in order to avoid open/stat races */
		if (fstat(fileno(f), &st) < 0 ||
		    (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
		    (st.st_mode & 022) != 0) {
			snprintf(buf, sizeof buf, "DSA authentication refused for %.100s: "
			    "bad ownership or modes for '%s'.", pw->pw_name, file);
			fail = 1;
		} else {
			/* Check path to SSH_USER_PERMITTED_KEYS */
			int i;
			static const char *check[] = {
				"", SSH_USER_DIR, NULL
			};
			for (i = 0; check[i]; i++) {
				snprintf(line, sizeof line, "%.500s/%.100s",
				    pw->pw_dir, check[i]);
				if (stat(line, &st) < 0 ||
				    (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
				    (st.st_mode & 022) != 0) {
					snprintf(buf, sizeof buf,
					    "DSA authentication refused for %.100s: "
					    "bad ownership or modes for '%s'.",
					    pw->pw_name, line);
					fail = 1;
					break;
				}
			}
		}
		if (fail) {
			fclose(f);
			log("%s",buf);
			restore_uid();
			return 0;
		}
	}
	found_key = 0;
	found = key_new(KEY_DSA);

	while (fgets(line, sizeof(line), f)) {
		char *cp, *options = NULL;
		linenum++;
		/* Skip leading whitespace, empty and comment lines. */
		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
			;
		if (!*cp || *cp == '\n' || *cp == '#')
			continue;

		bits = key_read(found, &cp);
		if (bits == 0) {
			/* no key?  check if there are options for this key */
			int quoted = 0;
			options = cp;
			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
				if (*cp == '\\' && cp[1] == '"')
					cp++;	/* Skip both */
				else if (*cp == '"')
					quoted = !quoted;
			}
			/* Skip remaining whitespace. */
			for (; *cp == ' ' || *cp == '\t'; cp++)
				;
			bits = key_read(found, &cp);
			if (bits == 0) {
				/* still no key?  advance to next line*/
				continue;
			}
		}
		if (key_equal(found, key) &&
		    auth_parse_options(pw, options, linenum) == 1) {
			found_key = 1;
			debug("matching key found: file %s, line %ld",
			    file, linenum);
			break;
		}
	}
	restore_uid();
	fclose(f);
	key_free(found);
	return found_key;
}