1 /*
2 Unix SMB/CIFS implementation.
3
4 Kerberos utility functions for GENSEC
5
6 Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
7
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
12
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
17
18
19 You should have received a copy of the GNU General Public License
20 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 */
22
23 #include "includes.h"
24 #include "system/kerberos.h"
25 #include "auth/kerberos/kerberos.h"
26 #include "auth/credentials/credentials.h"
27 #include "auth/credentials/credentials_proto.h"
28 #include "auth/credentials/credentials_krb5.h"
29 #include "auth/kerberos/kerberos_credentials.h"
30 #include "auth/kerberos/kerberos_util.h"
31
32 struct principal_container {
33 struct smb_krb5_context *smb_krb5_context;
34 krb5_principal principal;
35 const char *string_form; /* Optional */
36 };
37
free_principal(struct principal_container * pc)38 static krb5_error_code free_principal(struct principal_container *pc)
39 {
40 /* current heimdal - 0.6.3, which we need anyway, fixes segfaults here */
41 krb5_free_principal(pc->smb_krb5_context->krb5_context, pc->principal);
42
43 return 0;
44 }
45
46
parse_principal(TALLOC_CTX * parent_ctx,const char * princ_string,struct smb_krb5_context * smb_krb5_context,krb5_principal * princ,const char ** error_string)47 static krb5_error_code parse_principal(TALLOC_CTX *parent_ctx,
48 const char *princ_string,
49 struct smb_krb5_context *smb_krb5_context,
50 krb5_principal *princ,
51 const char **error_string)
52 {
53 int ret;
54 struct principal_container *mem_ctx;
55 if (princ_string == NULL) {
56 *princ = NULL;
57 return 0;
58 }
59
60 ret = krb5_parse_name(smb_krb5_context->krb5_context,
61 princ_string, princ);
62
63 if (ret) {
64 (*error_string) = smb_get_krb5_error_message(
65 smb_krb5_context->krb5_context,
66 ret, parent_ctx);
67 return ret;
68 }
69
70 mem_ctx = talloc(parent_ctx, struct principal_container);
71 if (!mem_ctx) {
72 (*error_string) = error_message(ENOMEM);
73 return ENOMEM;
74 }
75
76 /* This song-and-dance effectivly puts the principal
77 * into talloc, so we can't loose it. */
78 mem_ctx->smb_krb5_context = talloc_reference(mem_ctx,
79 smb_krb5_context);
80 mem_ctx->principal = *princ;
81 talloc_set_destructor(mem_ctx, free_principal);
82 return 0;
83 }
84
85 /* Obtain the principal set on this context. Requires a
86 * smb_krb5_context because we are doing krb5 principal parsing with
87 * the library routines. The returned princ is placed in the talloc
88 * system by means of a destructor (do *not* free). */
89
principal_from_credentials(TALLOC_CTX * parent_ctx,struct cli_credentials * credentials,struct smb_krb5_context * smb_krb5_context,krb5_principal * princ,enum credentials_obtained * obtained,const char ** error_string)90 krb5_error_code principal_from_credentials(TALLOC_CTX *parent_ctx,
91 struct cli_credentials *credentials,
92 struct smb_krb5_context *smb_krb5_context,
93 krb5_principal *princ,
94 enum credentials_obtained *obtained,
95 const char **error_string)
96 {
97 krb5_error_code ret;
98 const char *princ_string;
99 TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
100 *obtained = CRED_UNINITIALISED;
101
102 if (!mem_ctx) {
103 (*error_string) = error_message(ENOMEM);
104 return ENOMEM;
105 }
106 princ_string = cli_credentials_get_principal_and_obtained(credentials,
107 mem_ctx,
108 obtained);
109 if (!princ_string) {
110 *princ = NULL;
111 return 0;
112 }
113
114 ret = parse_principal(parent_ctx, princ_string,
115 smb_krb5_context, princ, error_string);
116 talloc_free(mem_ctx);
117 return ret;
118 }
119
120 /* Obtain the principal set on this context. Requires a
121 * smb_krb5_context because we are doing krb5 principal parsing with
122 * the library routines. The returned princ is placed in the talloc
123 * system by means of a destructor (do *not* free). */
124
impersonate_principal_from_credentials(TALLOC_CTX * parent_ctx,struct cli_credentials * credentials,struct smb_krb5_context * smb_krb5_context,krb5_principal * princ,const char ** error_string)125 static krb5_error_code impersonate_principal_from_credentials(
126 TALLOC_CTX *parent_ctx,
127 struct cli_credentials *credentials,
128 struct smb_krb5_context *smb_krb5_context,
129 krb5_principal *princ,
130 const char **error_string)
131 {
132 return parse_principal(parent_ctx,
133 cli_credentials_get_impersonate_principal(credentials),
134 smb_krb5_context, princ, error_string);
135 }
136
smb_krb5_create_principals_array(TALLOC_CTX * mem_ctx,krb5_context context,const char * account_name,const char * realm,uint32_t num_spns,const char * spns[],uint32_t * pnum_principals,krb5_principal ** pprincipals,const char ** error_string)137 krb5_error_code smb_krb5_create_principals_array(TALLOC_CTX *mem_ctx,
138 krb5_context context,
139 const char *account_name,
140 const char *realm,
141 uint32_t num_spns,
142 const char *spns[],
143 uint32_t *pnum_principals,
144 krb5_principal **pprincipals,
145 const char **error_string)
146 {
147 krb5_error_code code;
148 TALLOC_CTX *tmp_ctx;
149 uint32_t num_principals = 0;
150 krb5_principal *principals;
151 uint32_t i;
152
153 tmp_ctx = talloc_new(mem_ctx);
154 if (tmp_ctx == NULL) {
155 *error_string = "Cannot allocate tmp_ctx";
156 return ENOMEM;
157 }
158
159 if (realm == NULL) {
160 *error_string = "Cannot create principal without a realm";
161 code = EINVAL;
162 goto done;
163 }
164
165 if (account_name == NULL && (num_spns == 0 || spns == NULL)) {
166 *error_string = "Cannot create principal without an account or SPN";
167 code = EINVAL;
168 goto done;
169 }
170
171 if (account_name != NULL && account_name[0] != '\0') {
172 num_principals++;
173 }
174 num_principals += num_spns;
175
176 principals = talloc_zero_array(tmp_ctx,
177 krb5_principal,
178 num_principals);
179 if (principals == NULL) {
180 *error_string = "Cannot allocate principals";
181 code = ENOMEM;
182 goto done;
183 }
184
185 for (i = 0; i < num_spns; i++) {
186 code = krb5_parse_name(context, spns[i], &(principals[i]));
187 if (code != 0) {
188 *error_string = smb_get_krb5_error_message(context,
189 code,
190 mem_ctx);
191 goto done;
192 }
193 }
194
195 if (account_name != NULL && account_name[0] != '\0') {
196 code = smb_krb5_make_principal(context,
197 &(principals[i]),
198 realm,
199 account_name,
200 NULL);
201 if (code != 0) {
202 *error_string = smb_get_krb5_error_message(context,
203 code,
204 mem_ctx);
205 goto done;
206 }
207 }
208
209 if (pnum_principals != NULL) {
210 *pnum_principals = num_principals;
211
212 if (pprincipals != NULL) {
213 *pprincipals = talloc_steal(mem_ctx, principals);
214 }
215 }
216
217 code = 0;
218 done:
219 talloc_free(tmp_ctx);
220 return code;
221 }
222
223 /**
224 * Return a freshly allocated ccache (destroyed by destructor on child
225 * of parent_ctx), for a given set of client credentials
226 */
227
kinit_to_ccache(TALLOC_CTX * parent_ctx,struct cli_credentials * credentials,struct smb_krb5_context * smb_krb5_context,struct tevent_context * event_ctx,krb5_ccache ccache,enum credentials_obtained * obtained,const char ** error_string)228 krb5_error_code kinit_to_ccache(TALLOC_CTX *parent_ctx,
229 struct cli_credentials *credentials,
230 struct smb_krb5_context *smb_krb5_context,
231 struct tevent_context *event_ctx,
232 krb5_ccache ccache,
233 enum credentials_obtained *obtained,
234 const char **error_string)
235 {
236 krb5_error_code ret;
237 const char *password;
238 #ifdef SAMBA4_USES_HEIMDAL
239 const char *self_service;
240 #endif
241 const char *target_service;
242 time_t kdc_time = 0;
243 krb5_principal princ;
244 krb5_principal impersonate_principal;
245 int tries;
246 TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
247 krb5_get_init_creds_opt *krb_options;
248
249 if (!mem_ctx) {
250 (*error_string) = strerror(ENOMEM);
251 return ENOMEM;
252 }
253
254 ret = principal_from_credentials(mem_ctx, credentials, smb_krb5_context, &princ, obtained, error_string);
255 if (ret) {
256 talloc_free(mem_ctx);
257 return ret;
258 }
259
260 if (princ == NULL) {
261 (*error_string) = talloc_asprintf(credentials, "principal, username or realm was not specified in the credentials");
262 talloc_free(mem_ctx);
263 return KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN;
264 }
265
266 ret = impersonate_principal_from_credentials(mem_ctx, credentials, smb_krb5_context, &impersonate_principal, error_string);
267 if (ret) {
268 talloc_free(mem_ctx);
269 return ret;
270 }
271
272 #ifdef SAMBA4_USES_HEIMDAL
273 self_service = cli_credentials_get_self_service(credentials);
274 #endif
275 target_service = cli_credentials_get_target_service(credentials);
276
277 password = cli_credentials_get_password(credentials);
278
279 /* setup the krb5 options we want */
280 if ((ret = krb5_get_init_creds_opt_alloc(smb_krb5_context->krb5_context, &krb_options))) {
281 (*error_string) = talloc_asprintf(credentials, "krb5_get_init_creds_opt_alloc failed (%s)\n",
282 smb_get_krb5_error_message(smb_krb5_context->krb5_context,
283 ret, mem_ctx));
284 talloc_free(mem_ctx);
285 return ret;
286 }
287
288 #ifdef SAMBA4_USES_HEIMDAL /* Disable for now MIT reads defaults when needed */
289 /* get the defaults */
290 krb5_get_init_creds_opt_set_default_flags(smb_krb5_context->krb5_context, NULL, NULL, krb_options);
291 #endif
292 /* set if we want a forwardable ticket */
293 switch (cli_credentials_get_krb_forwardable(credentials)) {
294 case CRED_AUTO_KRB_FORWARDABLE:
295 break;
296 case CRED_NO_KRB_FORWARDABLE:
297 krb5_get_init_creds_opt_set_forwardable(krb_options, FALSE);
298 break;
299 case CRED_FORCE_KRB_FORWARDABLE:
300 krb5_get_init_creds_opt_set_forwardable(krb_options, TRUE);
301 break;
302 }
303
304 #ifdef SAMBA4_USES_HEIMDAL /* FIXME: MIT does not have this yet */
305 /*
306 * In order to work against windows KDCs even if we use
307 * the netbios domain name as realm, we need to add the following
308 * flags:
309 * KRB5_INIT_CREDS_NO_C_CANON_CHECK;
310 * KRB5_INIT_CREDS_NO_C_NO_EKU_CHECK;
311 *
312 * On MIT: Set pkinit_eku_checking to none
313 */
314 krb5_get_init_creds_opt_set_win2k(smb_krb5_context->krb5_context,
315 krb_options, true);
316 krb5_get_init_creds_opt_set_canonicalize(smb_krb5_context->krb5_context,
317 krb_options, true);
318 #else /* MIT */
319 krb5_get_init_creds_opt_set_canonicalize(krb_options, true);
320 #endif
321
322 tries = 2;
323 while (tries--) {
324 #ifdef SAMBA4_USES_HEIMDAL
325 struct tevent_context *previous_ev;
326 /* Do this every time, in case we have weird recursive issues here */
327 ret = smb_krb5_context_set_event_ctx(smb_krb5_context, event_ctx, &previous_ev);
328 if (ret) {
329 talloc_free(mem_ctx);
330 return ret;
331 }
332 #endif
333 if (password) {
334 if (impersonate_principal) {
335 #ifdef SAMBA4_USES_HEIMDAL
336 ret = smb_krb5_kinit_s4u2_ccache(smb_krb5_context->krb5_context,
337 ccache,
338 princ,
339 password,
340 impersonate_principal,
341 self_service,
342 target_service,
343 krb_options,
344 NULL,
345 &kdc_time);
346 #else
347 talloc_free(mem_ctx);
348 (*error_string) = "INTERNAL error: s4u2 ops "
349 "are not supported with MIT build yet";
350 return EINVAL;
351 #endif
352 } else {
353 ret = smb_krb5_kinit_password_ccache(smb_krb5_context->krb5_context,
354 ccache,
355 princ,
356 password,
357 target_service,
358 krb_options,
359 NULL,
360 &kdc_time);
361 }
362 } else if (impersonate_principal) {
363 talloc_free(mem_ctx);
364 (*error_string) = "INTERNAL error: Cannot impersonate principal with just a keyblock. A password must be specified in the credentials";
365 return EINVAL;
366 } else {
367 /* No password available, try to use a keyblock instead */
368
369 krb5_keyblock keyblock;
370 const struct samr_Password *mach_pwd;
371 mach_pwd = cli_credentials_get_nt_hash(credentials, mem_ctx);
372 if (!mach_pwd) {
373 talloc_free(mem_ctx);
374 (*error_string) = "kinit_to_ccache: No password available for kinit\n";
375 krb5_get_init_creds_opt_free(smb_krb5_context->krb5_context, krb_options);
376 #ifdef SAMBA4_USES_HEIMDAL
377 smb_krb5_context_remove_event_ctx(smb_krb5_context, previous_ev, event_ctx);
378 #endif
379 return EINVAL;
380 }
381 ret = smb_krb5_keyblock_init_contents(smb_krb5_context->krb5_context,
382 ENCTYPE_ARCFOUR_HMAC,
383 mach_pwd->hash, sizeof(mach_pwd->hash),
384 &keyblock);
385
386 if (ret == 0) {
387 ret = smb_krb5_kinit_keyblock_ccache(smb_krb5_context->krb5_context,
388 ccache,
389 princ,
390 &keyblock,
391 target_service,
392 krb_options,
393 NULL,
394 &kdc_time);
395 krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &keyblock);
396 }
397 }
398
399 #ifdef SAMBA4_USES_HEIMDAL
400 smb_krb5_context_remove_event_ctx(smb_krb5_context, previous_ev, event_ctx);
401 #endif
402
403 if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
404 /* Perhaps we have been given an invalid skew, so try again without it */
405 time_t t = time(NULL);
406 krb5_set_real_time(smb_krb5_context->krb5_context, t, 0);
407 } else {
408 /* not a skew problem */
409 break;
410 }
411 }
412
413 krb5_get_init_creds_opt_free(smb_krb5_context->krb5_context, krb_options);
414
415 if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
416 (*error_string) = talloc_asprintf(credentials, "kinit for %s failed (%s)\n",
417 cli_credentials_get_principal(credentials, mem_ctx),
418 smb_get_krb5_error_message(smb_krb5_context->krb5_context,
419 ret, mem_ctx));
420 talloc_free(mem_ctx);
421 return ret;
422 }
423
424 /* cope with ticket being in the future due to clock skew */
425 if ((unsigned)kdc_time > time(NULL)) {
426 time_t t = time(NULL);
427 int time_offset =(unsigned)kdc_time-t;
428 DEBUG(4,("Advancing clock by %d seconds to cope with clock skew\n", time_offset));
429 krb5_set_real_time(smb_krb5_context->krb5_context, t + time_offset + 1, 0);
430 }
431
432 if (ret == KRB5KDC_ERR_PREAUTH_FAILED && cli_credentials_wrong_password(credentials)) {
433 ret = kinit_to_ccache(parent_ctx,
434 credentials,
435 smb_krb5_context,
436 event_ctx,
437 ccache, obtained,
438 error_string);
439 }
440
441 if (ret) {
442 (*error_string) = talloc_asprintf(credentials, "kinit for %s failed (%s)\n",
443 cli_credentials_get_principal(credentials, mem_ctx),
444 smb_get_krb5_error_message(smb_krb5_context->krb5_context,
445 ret, mem_ctx));
446 talloc_free(mem_ctx);
447 return ret;
448 }
449
450 DEBUG(10,("kinit for %s succeeded\n",
451 cli_credentials_get_principal(credentials, mem_ctx)));
452
453
454 talloc_free(mem_ctx);
455 return 0;
456 }
457
free_keytab_container(struct keytab_container * ktc)458 static krb5_error_code free_keytab_container(struct keytab_container *ktc)
459 {
460 return krb5_kt_close(ktc->smb_krb5_context->krb5_context, ktc->keytab);
461 }
462
smb_krb5_get_keytab_container(TALLOC_CTX * mem_ctx,struct smb_krb5_context * smb_krb5_context,krb5_keytab opt_keytab,const char * keytab_name,struct keytab_container ** ktc)463 krb5_error_code smb_krb5_get_keytab_container(TALLOC_CTX *mem_ctx,
464 struct smb_krb5_context *smb_krb5_context,
465 krb5_keytab opt_keytab,
466 const char *keytab_name,
467 struct keytab_container **ktc)
468 {
469 krb5_keytab keytab;
470 krb5_error_code ret;
471
472 if (opt_keytab) {
473 keytab = opt_keytab;
474 } else {
475 ret = krb5_kt_resolve(smb_krb5_context->krb5_context,
476 keytab_name, &keytab);
477 if (ret) {
478 DEBUG(1,("failed to open krb5 keytab: %s\n",
479 smb_get_krb5_error_message(
480 smb_krb5_context->krb5_context,
481 ret, mem_ctx)));
482 return ret;
483 }
484 }
485
486 *ktc = talloc(mem_ctx, struct keytab_container);
487 if (!*ktc) {
488 return ENOMEM;
489 }
490
491 (*ktc)->smb_krb5_context = talloc_reference(*ktc, smb_krb5_context);
492 (*ktc)->keytab = keytab;
493 (*ktc)->password_based = false;
494 talloc_set_destructor(*ktc, free_keytab_container);
495
496 return 0;
497 }
498
499 /*
500 * Walk the keytab, looking for entries of this principal name,
501 * with KVNO other than current kvno -1.
502 *
503 * These entries are now stale,
504 * we only keep the current and previous entries around.
505 *
506 * Inspired by the code in Samba3 for 'use kerberos keytab'.
507 */
smb_krb5_remove_obsolete_keytab_entries(TALLOC_CTX * mem_ctx,krb5_context context,krb5_keytab keytab,uint32_t num_principals,krb5_principal * principals,krb5_kvno kvno,bool * found_previous,const char ** error_string)508 krb5_error_code smb_krb5_remove_obsolete_keytab_entries(TALLOC_CTX *mem_ctx,
509 krb5_context context,
510 krb5_keytab keytab,
511 uint32_t num_principals,
512 krb5_principal *principals,
513 krb5_kvno kvno,
514 bool *found_previous,
515 const char **error_string)
516 {
517 TALLOC_CTX *tmp_ctx;
518 krb5_error_code code;
519 krb5_kt_cursor cursor;
520
521 tmp_ctx = talloc_new(mem_ctx);
522 if (tmp_ctx == NULL) {
523 *error_string = "Cannot allocate tmp_ctx";
524 return ENOMEM;
525 }
526
527 *found_previous = true;
528
529 code = krb5_kt_start_seq_get(context, keytab, &cursor);
530 switch (code) {
531 case 0:
532 break;
533 #ifdef HEIM_ERR_OPNOTSUPP
534 case HEIM_ERR_OPNOTSUPP:
535 #endif
536 case ENOENT:
537 case KRB5_KT_END:
538 /* no point enumerating if there isn't anything here */
539 code = 0;
540 goto done;
541 default:
542 *error_string = talloc_asprintf(mem_ctx,
543 "failed to open keytab for read of old entries: %s\n",
544 smb_get_krb5_error_message(context, code, mem_ctx));
545 goto done;
546 }
547
548 do {
549 krb5_kvno old_kvno = kvno - 1;
550 krb5_keytab_entry entry;
551 bool matched = false;
552 uint32_t i;
553
554 code = krb5_kt_next_entry(context, keytab, &entry, &cursor);
555 if (code) {
556 break;
557 }
558
559 for (i = 0; i < num_principals; i++) {
560 krb5_boolean ok;
561
562 ok = smb_krb5_kt_compare(context,
563 &entry,
564 principals[i],
565 0,
566 0);
567 if (ok) {
568 matched = true;
569 break;
570 }
571 }
572
573 if (!matched) {
574 /*
575 * Free the entry, it wasn't the one we were looking
576 * for anyway
577 */
578 krb5_kt_free_entry(context, &entry);
579 /* Make sure we do not double free */
580 ZERO_STRUCT(entry);
581 continue;
582 }
583
584 /*
585 * Delete it, if it is not kvno - 1.
586 *
587 * Some keytab files store the kvno only in 8bits. Limit the
588 * compare to 8bits, so that we don't miss old keys and delete
589 * them.
590 */
591 if ((entry.vno & 0xff) != (old_kvno & 0xff)) {
592 krb5_error_code rc;
593
594 /* Release the enumeration. We are going to
595 * have to start this from the top again,
596 * because deletes during enumeration may not
597 * always be consistent.
598 *
599 * Also, the enumeration locks a FILE: keytab
600 */
601 krb5_kt_end_seq_get(context, keytab, &cursor);
602
603 code = krb5_kt_remove_entry(context, keytab, &entry);
604 krb5_kt_free_entry(context, &entry);
605
606 /* Make sure we do not double free */
607 ZERO_STRUCT(entry);
608
609 /* Deleted: Restart from the top */
610 rc = krb5_kt_start_seq_get(context, keytab, &cursor);
611 if (rc != 0) {
612 krb5_kt_free_entry(context, &entry);
613
614 /* Make sure we do not double free */
615 ZERO_STRUCT(entry);
616
617 DEBUG(1, ("failed to restart enumeration of keytab: %s\n",
618 smb_get_krb5_error_message(context,
619 code,
620 tmp_ctx)));
621
622 talloc_free(tmp_ctx);
623 return rc;
624 }
625
626 if (code != 0) {
627 break;
628 }
629
630 } else {
631 *found_previous = true;
632 }
633
634 /* Free the entry, we don't need it any more */
635 krb5_kt_free_entry(context, &entry);
636 /* Make sure we do not double free */
637 ZERO_STRUCT(entry);
638 } while (code == 0);
639
640 krb5_kt_end_seq_get(context, keytab, &cursor);
641
642 switch (code) {
643 case 0:
644 break;
645 case ENOENT:
646 case KRB5_KT_END:
647 break;
648 default:
649 *error_string = talloc_asprintf(mem_ctx,
650 "failed in deleting old entries for principal: %s\n",
651 smb_get_krb5_error_message(context,
652 code,
653 mem_ctx));
654 }
655
656 code = 0;
657 done:
658 talloc_free(tmp_ctx);
659 return code;
660 }
661