summaryrefslogtreecommitdiff
path: root/source3/libads/kerberos_verify.c
blob: ca36e6e4254b1f7f5d83502321f470f83874178b (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
546
547
548
/* 
   Unix SMB/CIFS implementation.
   kerberos utility library
   Copyright (C) Andrew Tridgell 2001
   Copyright (C) Remus Koos 2001
   Copyright (C) Luke Howard 2003   
   Copyright (C) Guenther Deschner 2003, 2005
   Copyright (C) Jim McDonough (jmcd@us.ibm.com) 2003
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
   Copyright (C) Jeremy Allison 2007
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

#ifdef HAVE_KRB5

#if !defined(HAVE_KRB5_PRINC_COMPONENT)
const krb5_data *krb5_princ_component(krb5_context, krb5_principal, int );
#endif

/**********************************************************************************
 Try to verify a ticket using the system keytab... the system keytab has kvno -1 entries, so
 it's more like what microsoft does... see comment in utils/net_ads.c in the
 ads_keytab_add_entry function for details.
***********************************************************************************/

static BOOL ads_keytab_verify_ticket(krb5_context context,
					krb5_auth_context auth_context,
					const DATA_BLOB *ticket,
					krb5_ticket **pp_tkt,
					krb5_keyblock **keyblock,
					krb5_error_code *perr)
{
	krb5_error_code ret = 0;
	BOOL auth_ok = False;
	krb5_keytab keytab = NULL;
	krb5_kt_cursor kt_cursor;
	krb5_keytab_entry kt_entry;
	char *valid_princ_formats[7] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL };
	char *entry_princ_s = NULL;
	fstring my_name, my_fqdn;
	int i;
	int number_matched_principals = 0;
	krb5_data packet;

	*pp_tkt = NULL;
	*keyblock = NULL;
	*perr = 0;

	/* Generate the list of principal names which we expect
	 * clients might want to use for authenticating to the file
	 * service.  We allow name$,{host,cifs}/{name,fqdn,name.REALM}. */

	fstrcpy(my_name, global_myname());

	my_fqdn[0] = '\0';
	name_to_fqdn(my_fqdn, global_myname());

	asprintf(&valid_princ_formats[0], "%s$@%s", my_name, lp_realm());
	asprintf(&valid_princ_formats[1], "host/%s@%s", my_name, lp_realm());
	asprintf(&valid_princ_formats[2], "host/%s@%s", my_fqdn, lp_realm());
	asprintf(&valid_princ_formats[3], "host/%s.%s@%s", my_name, lp_realm(), lp_realm());
	asprintf(&valid_princ_formats[4], "cifs/%s@%s", my_name, lp_realm());
	asprintf(&valid_princ_formats[5], "cifs/%s@%s", my_fqdn, lp_realm());
	asprintf(&valid_princ_formats[6], "cifs/%s.%s@%s", my_name, lp_realm(), lp_realm());

	ZERO_STRUCT(kt_entry);
	ZERO_STRUCT(kt_cursor);

	ret = krb5_kt_default(context, &keytab);
	if (ret) {
		DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_default failed (%s)\n", error_message(ret)));
		goto out;
	}

	/* Iterate through the keytab.  For each key, if the principal
	 * name case-insensitively matches one of the allowed formats,
	 * try verifying the ticket using that principal. */

	ret = krb5_kt_start_seq_get(context, keytab, &kt_cursor);
	if (ret) {
		DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_start_seq_get failed (%s)\n", error_message(ret)));
		goto out;
	}
  
	while (!auth_ok && (krb5_kt_next_entry(context, keytab, &kt_entry, &kt_cursor) == 0)) {
		ret = smb_krb5_unparse_name(context, kt_entry.principal, &entry_princ_s);
		if (ret) {
			DEBUG(1, ("ads_keytab_verify_ticket: smb_krb5_unparse_name failed (%s)\n",
				error_message(ret)));
			goto out;
		}

		for (i = 0; i < ARRAY_SIZE(valid_princ_formats); i++) {

			if (!strequal(entry_princ_s, valid_princ_formats[i])) {
				continue;
			}

			number_matched_principals++;
			packet.length = ticket->length;
			packet.data = (char *)ticket->data;
			*pp_tkt = NULL;

			ret = krb5_rd_req_return_keyblock_from_keytab(context, &auth_context, &packet,
							  	      kt_entry.principal, keytab,
								      NULL, pp_tkt, keyblock);

			if (ret) {
				DEBUG(10,("ads_keytab_verify_ticket: "
					"krb5_rd_req_return_keyblock_from_keytab(%s) failed: %s\n",
					entry_princ_s, error_message(ret)));

				/* workaround for MIT: 
				* as krb5_ktfile_get_entry will explicitly
				* close the krb5_keytab as soon as krb5_rd_req
				* has sucessfully decrypted the ticket but the
				* ticket is not valid yet (due to clockskew)
				* there is no point in querying more keytab
				* entries - Guenther */
					
				if (ret == KRB5KRB_AP_ERR_TKT_NYV || 
				    ret == KRB5KRB_AP_ERR_TKT_EXPIRED ||
				    ret == KRB5KRB_AP_ERR_SKEW) {
					break;
				}
			} else {
				DEBUG(3,("ads_keytab_verify_ticket: "
					"krb5_rd_req_return_keyblock_from_keytab succeeded for principal %s\n",
					entry_princ_s));
				auth_ok = True;
				break;
			}
		}

		/* Free the name we parsed. */
		SAFE_FREE(entry_princ_s);

		/* Free the entry we just read. */
		smb_krb5_kt_free_entry(context, &kt_entry);
		ZERO_STRUCT(kt_entry);
	}
	krb5_kt_end_seq_get(context, keytab, &kt_cursor);

	ZERO_STRUCT(kt_cursor);

  out:
	
	for (i = 0; i < ARRAY_SIZE(valid_princ_formats); i++) {
		SAFE_FREE(valid_princ_formats[i]);
	}
	
	if (!auth_ok) {
		if (!number_matched_principals) {
			DEBUG(3, ("ads_keytab_verify_ticket: no keytab principals matched expected file service name.\n"));
		} else {
			DEBUG(3, ("ads_keytab_verify_ticket: krb5_rd_req failed for all %d matched keytab principals\n",
				number_matched_principals));
		}
	}

	SAFE_FREE(entry_princ_s);

	{
		krb5_keytab_entry zero_kt_entry;
		ZERO_STRUCT(zero_kt_entry);
		if (memcmp(&zero_kt_entry, &kt_entry, sizeof(krb5_keytab_entry))) {
			smb_krb5_kt_free_entry(context, &kt_entry);
		}
	}

	{
		krb5_kt_cursor zero_csr;
		ZERO_STRUCT(zero_csr);
		if ((memcmp(&kt_cursor, &zero_csr, sizeof(krb5_kt_cursor)) != 0) && keytab) {
			krb5_kt_end_seq_get(context, keytab, &kt_cursor);
		}
	}

	if (keytab) {
		krb5_kt_close(context, keytab);
	}
	*perr = ret;
	return auth_ok;
}

/**********************************************************************************
 Try to verify a ticket using the secrets.tdb.
***********************************************************************************/

static krb5_error_code ads_secrets_verify_ticket(krb5_context context,
						krb5_auth_context auth_context,
						krb5_principal host_princ,
						const DATA_BLOB *ticket,
						krb5_ticket **pp_tkt,
						krb5_keyblock **keyblock,
						krb5_error_code *perr)
{
	krb5_error_code ret = 0;
	BOOL auth_ok = False;
	char *password_s = NULL;
	krb5_data password;
	krb5_enctype enctypes[4] = { ENCTYPE_DES_CBC_CRC, ENCTYPE_DES_CBC_MD5, 0, 0 };
	krb5_data packet;
	int i;

	*pp_tkt = NULL;
	*keyblock = NULL;
	*perr = 0;

#if defined(ENCTYPE_ARCFOUR_HMAC)
	enctypes[2] = ENCTYPE_ARCFOUR_HMAC;
#endif

	if (!secrets_init()) {
		DEBUG(1,("ads_secrets_verify_ticket: secrets_init failed\n"));
		*perr = KRB5_CONFIG_CANTOPEN;
		return False;
	}

	password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
	if (!password_s) {
		DEBUG(1,("ads_secrets_verify_ticket: failed to fetch machine password\n"));
		*perr = KRB5_LIBOS_CANTREADPWD;
		return False;
	}

	password.data = password_s;
	password.length = strlen(password_s);

	/* CIFS doesn't use addresses in tickets. This would break NAT. JRA */

	packet.length = ticket->length;
	packet.data = (char *)ticket->data;

	/* We need to setup a auth context with each possible encoding type in turn. */
	for (i=0;enctypes[i];i++) {
		krb5_keyblock *key = NULL;

		if (!(key = SMB_MALLOC_P(krb5_keyblock))) {
			ret = ENOMEM;
			goto out;
		}
	
		if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
			SAFE_FREE(key);
			continue;
		}

		krb5_auth_con_setuseruserkey(context, auth_context, key);

		if (!(ret = krb5_rd_req(context, &auth_context, &packet, 
					NULL,
					NULL, NULL, pp_tkt))) {
			DEBUG(10,("ads_secrets_verify_ticket: enc type [%u] decrypted message !\n",
				(unsigned int)enctypes[i] ));
			auth_ok = True;
			krb5_copy_keyblock(context, key, keyblock);
			krb5_free_keyblock(context, key);
			break;
		}

		DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
				("ads_secrets_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
				(unsigned int)enctypes[i], error_message(ret)));

		/* successfully decrypted but ticket is just not valid at the moment */
		if (ret == KRB5KRB_AP_ERR_TKT_NYV || 
		    ret == KRB5KRB_AP_ERR_TKT_EXPIRED ||
		    ret == KRB5KRB_AP_ERR_SKEW) {
			break;
		}

		krb5_free_keyblock(context, key);

	}

 out:
	SAFE_FREE(password_s);
	*perr = ret;
	return auth_ok;
}

/**********************************************************************************
 Verify an incoming ticket and parse out the principal name and 
 authorization_data if available.
***********************************************************************************/

NTSTATUS ads_verify_ticket(TALLOC_CTX *mem_ctx,
			   const char *realm,
			   time_t time_offset,
			   const DATA_BLOB *ticket,
			   char **principal,
			   PAC_DATA **pac_data,
			   DATA_BLOB *ap_rep,
			   DATA_BLOB *session_key)
{
	NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
	NTSTATUS pac_ret;
	DATA_BLOB auth_data;
	krb5_context context = NULL;
	krb5_auth_context auth_context = NULL;
	krb5_data packet;
	krb5_ticket *tkt = NULL;
	krb5_rcache rcache = NULL;
	krb5_keyblock *keyblock = NULL;
	time_t authtime;
	krb5_error_code ret = 0;
	
	krb5_principal host_princ = NULL;
	krb5_const_principal client_principal = NULL;
	char *host_princ_s = NULL;
	BOOL auth_ok = False;
	BOOL got_replay_mutex = False;
	BOOL got_auth_data = False;

	ZERO_STRUCT(packet);
	ZERO_STRUCT(auth_data);

	*principal = NULL;
	*pac_data = NULL;
	*ap_rep = data_blob_null;
	*session_key = data_blob_null;

	initialize_krb5_error_table();
	ret = krb5_init_context(&context);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
		return NT_STATUS_LOGON_FAILURE;
	}

	if (time_offset != 0) {
		krb5_set_real_time(context, time(NULL) + time_offset, 0);
	}

	ret = krb5_set_default_realm(context, realm);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
		goto out;
	}

	/* This whole process is far more complex than I would
           like. We have to go through all this to allow us to store
           the secret internally, instead of using /etc/krb5.keytab */

	ret = krb5_auth_con_init(context, &auth_context);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
		goto out;
	}

	asprintf(&host_princ_s, "%s$", global_myname());
	if (!host_princ_s) {
		goto out;
	}

	strlower_m(host_princ_s);
	ret = smb_krb5_parse_name(context, host_princ_s, &host_princ);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: smb_krb5_parse_name(%s) failed (%s)\n",
					host_princ_s, error_message(ret)));
		goto out;
	}


	/* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
	 * code surrounding the replay cache... */

	if (!grab_server_mutex("replay cache mutex")) {
		DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
		ret = KRB5_CC_IO;
		goto out;
	}

	got_replay_mutex = True;

	/*
	 * JRA. We must set the rcache here. This will prevent replay attacks.
	 */

	ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
		goto out;
	}

	ret = krb5_auth_con_setrcache(context, auth_context, rcache);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
		goto out;
	}

	if (lp_use_kerberos_keytab()) {
		auth_ok = ads_keytab_verify_ticket(context, auth_context, ticket, &tkt, &keyblock, &ret);
	}
	if (!auth_ok) {
		auth_ok = ads_secrets_verify_ticket(context, auth_context, host_princ,
						    ticket, &tkt, &keyblock, &ret);
	}

	release_server_mutex();
	got_replay_mutex = False;

#if 0
	/* Heimdal leaks here, if we fix the leak, MIT crashes */
	if (rcache) {
		krb5_rc_close(context, rcache);
	}
#endif

	if (!auth_ok) {
		DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n", 
			 error_message(ret)));
		/* Try map the error return in case it's something like
		 * a clock skew error.
		 */
		sret = krb5_to_nt_status(ret);
		if (NT_STATUS_IS_OK(sret) || NT_STATUS_EQUAL(sret,NT_STATUS_UNSUCCESSFUL)) {
			sret = NT_STATUS_LOGON_FAILURE;
		}
		DEBUG(10,("ads_verify_ticket: returning error %s\n",
			nt_errstr(sret) ));
		goto out;
	} 
	
	authtime = get_authtime_from_tkt(tkt);
	client_principal = get_principal_from_tkt(tkt);

	ret = krb5_mk_rep(context, auth_context, &packet);
	if (ret) {
		DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
			error_message(ret)));
		goto out;
	}

	*ap_rep = data_blob(packet.data, packet.length);
	if (packet.data) {
		kerberos_free_data_contents(context, &packet);
		ZERO_STRUCT(packet);
	}

	get_krb5_smb_session_key(context, auth_context, session_key, True);
	dump_data_pw("SMB session key (from ticket)\n", session_key->data, session_key->length);

#if 0
	file_save("/tmp/ticket.dat", ticket->data, ticket->length);
#endif

	/* continue when no PAC is retrieved or we couldn't decode the PAC 
	   (like accounts that have the UF_NO_AUTH_DATA_REQUIRED flag set, or
	   Kerberos tickets encrypted using a DES key) - Guenther */

	got_auth_data = get_auth_data_from_tkt(mem_ctx, &auth_data, tkt);
	if (!got_auth_data) {
		DEBUG(3,("ads_verify_ticket: did not retrieve auth data. continuing without PAC\n"));
	}

	if (got_auth_data && pac_data != NULL) {

		pac_ret = decode_pac_data(mem_ctx, &auth_data, context, keyblock, client_principal, authtime, pac_data);
		if (!NT_STATUS_IS_OK(pac_ret)) {
			DEBUG(3,("ads_verify_ticket: failed to decode PAC_DATA: %s\n", nt_errstr(pac_ret)));
			*pac_data = NULL;
		}
		data_blob_free(&auth_data);
	}

#if 0
#if defined(HAVE_KRB5_TKT_ENC_PART2)
	/* MIT */
	if (tkt->enc_part2) {
		file_save("/tmp/authdata.dat",
			  tkt->enc_part2->authorization_data[0]->contents,
			  tkt->enc_part2->authorization_data[0]->length);
	}
#else
	/* Heimdal */
	if (tkt->ticket.authorization_data) {
		file_save("/tmp/authdata.dat",
			  tkt->ticket.authorization_data->val->ad_data.data,
			  tkt->ticket.authorization_data->val->ad_data.length);
	}
#endif
#endif

	if ((ret = smb_krb5_unparse_name(context, client_principal, principal))) {
		DEBUG(3,("ads_verify_ticket: smb_krb5_unparse_name failed (%s)\n", 
			 error_message(ret)));
		sret = NT_STATUS_LOGON_FAILURE;
		goto out;
	}

	sret = NT_STATUS_OK;

 out:

	if (got_replay_mutex) {
		release_server_mutex();
	}

	if (!NT_STATUS_IS_OK(sret)) {
		data_blob_free(&auth_data);
	}

	if (!NT_STATUS_IS_OK(sret)) {
		data_blob_free(ap_rep);
	}

	if (host_princ) {
		krb5_free_principal(context, host_princ);
	}

	if (keyblock) {
		krb5_free_keyblock(context, keyblock);
	}

	if (tkt != NULL) {
		krb5_free_ticket(context, tkt);
	}

	SAFE_FREE(host_princ_s);

	if (auth_context) {
		krb5_auth_con_free(context, auth_context);
	}

	if (context) {
		krb5_free_context(context);
	}

	return sret;
}

#endif /* HAVE_KRB5 */