1 /* $NetBSD: transited.c,v 1.3 2023/06/19 21:41:45 christos Exp $ */
2
3 /*
4 * Copyright (c) 1997 - 2001, 2003 Kungliga Tekniska Högskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include "krb5_locl.h"
37
38 /* this is an attempt at one of the most horrible `compression'
39 schemes that has ever been invented; it's so amazingly brain-dead
40 that words can not describe it, and all this just to save a few
41 silly bytes */
42
43 struct tr_realm {
44 char *realm;
45 unsigned leading_space:1;
46 unsigned leading_slash:1;
47 unsigned trailing_dot:1;
48 struct tr_realm *next;
49 };
50
51 static void
free_realms(struct tr_realm * r)52 free_realms(struct tr_realm *r)
53 {
54 struct tr_realm *p;
55 while(r){
56 p = r;
57 r = r->next;
58 free(p->realm);
59 free(p);
60 }
61 }
62
63 static int
make_path(krb5_context context,struct tr_realm * r,const char * from,const char * to)64 make_path(krb5_context context, struct tr_realm *r,
65 const char *from, const char *to)
66 {
67 struct tr_realm *tmp;
68 const char *p;
69
70 if(strlen(from) < strlen(to)){
71 const char *str;
72 str = from;
73 from = to;
74 to = str;
75 }
76
77 if(strcmp(from + strlen(from) - strlen(to), to) == 0){
78 p = from;
79 while(1){
80 p = strchr(p, '.');
81 if(p == NULL) {
82 krb5_clear_error_message (context);
83 return KRB5KDC_ERR_POLICY;
84 }
85 p++;
86 if(strcmp(p, to) == 0)
87 break;
88 tmp = calloc(1, sizeof(*tmp));
89 if(tmp == NULL)
90 return krb5_enomem(context);
91 tmp->next = r->next;
92 r->next = tmp;
93 tmp->realm = strdup(p);
94 if(tmp->realm == NULL){
95 r->next = tmp->next;
96 free(tmp);
97 return krb5_enomem(context);
98 }
99 }
100 }else if(strncmp(from, to, strlen(to)) == 0){
101 p = from + strlen(from);
102 while(1){
103 while(p >= from && *p != '/') p--;
104 if(p == from)
105 return KRB5KDC_ERR_POLICY;
106
107 if(strncmp(to, from, p - from) == 0)
108 break;
109 tmp = calloc(1, sizeof(*tmp));
110 if(tmp == NULL)
111 return krb5_enomem(context);
112 tmp->next = r->next;
113 r->next = tmp;
114 tmp->realm = malloc(p - from + 1);
115 if(tmp->realm == NULL){
116 r->next = tmp->next;
117 free(tmp);
118 return krb5_enomem(context);
119 }
120 memcpy(tmp->realm, from, p - from);
121 tmp->realm[p - from] = '\0';
122 p--;
123 }
124 } else {
125 krb5_clear_error_message (context);
126 return KRB5KDC_ERR_POLICY;
127 }
128
129 return 0;
130 }
131
132 static int
make_paths(krb5_context context,struct tr_realm * realms,const char * client_realm,const char * server_realm)133 make_paths(krb5_context context,
134 struct tr_realm *realms, const char *client_realm,
135 const char *server_realm)
136 {
137 struct tr_realm *r;
138 int ret;
139 const char *prev_realm = client_realm;
140 const char *next_realm = NULL;
141 for(r = realms; r; r = r->next){
142 /* it *might* be that you can have more than one empty
143 component in a row, at least that's how I interpret the
144 "," exception in 1510 */
145 if(r->realm[0] == '\0'){
146 while(r->next && r->next->realm[0] == '\0')
147 r = r->next;
148 if(r->next)
149 next_realm = r->next->realm;
150 else
151 next_realm = server_realm;
152 ret = make_path(context, r, prev_realm, next_realm);
153 if(ret){
154 free_realms(realms);
155 return ret;
156 }
157 }
158 prev_realm = r->realm;
159 }
160 return 0;
161 }
162
163 static int
expand_realms(krb5_context context,struct tr_realm * realms,const char * client_realm)164 expand_realms(krb5_context context,
165 struct tr_realm *realms, const char *client_realm)
166 {
167 struct tr_realm *r;
168 const char *prev_realm = NULL;
169 for(r = realms; r; r = r->next){
170 if(r->trailing_dot){
171 char *tmp;
172 size_t len;
173
174 if(prev_realm == NULL)
175 prev_realm = client_realm;
176
177 len = strlen(r->realm) + strlen(prev_realm) + 1;
178
179 tmp = realloc(r->realm, len);
180 if(tmp == NULL){
181 free_realms(realms);
182 return krb5_enomem(context);
183 }
184 r->realm = tmp;
185 strlcat(r->realm, prev_realm, len);
186 }else if(r->leading_slash && !r->leading_space && prev_realm){
187 /* yet another exception: if you use x500-names, the
188 leading realm doesn't have to be "quoted" with a space */
189 char *tmp;
190 size_t len = strlen(r->realm) + strlen(prev_realm) + 1;
191
192 tmp = malloc(len);
193 if(tmp == NULL){
194 free_realms(realms);
195 return krb5_enomem(context);
196 }
197 strlcpy(tmp, prev_realm, len);
198 strlcat(tmp, r->realm, len);
199 free(r->realm);
200 r->realm = tmp;
201 }
202 prev_realm = r->realm;
203 }
204 return 0;
205 }
206
207 static struct tr_realm *
make_realm(char * realm)208 make_realm(char *realm)
209 {
210 struct tr_realm *r;
211 char *p, *q;
212 int quote = 0;
213 r = calloc(1, sizeof(*r));
214 if(r == NULL){
215 free(realm);
216 return NULL;
217 }
218 r->realm = realm;
219 for(p = q = r->realm; *p; p++){
220 if(p == r->realm && *p == ' '){
221 r->leading_space = 1;
222 continue;
223 }
224 if(q == r->realm && *p == '/')
225 r->leading_slash = 1;
226 if(quote){
227 *q++ = *p;
228 quote = 0;
229 continue;
230 }
231 if(*p == '\\'){
232 quote = 1;
233 continue;
234 }
235 if(p[0] == '.' && p[1] == '\0')
236 r->trailing_dot = 1;
237 *q++ = *p;
238 }
239 *q = '\0';
240 return r;
241 }
242
243 static struct tr_realm*
append_realm(struct tr_realm * head,struct tr_realm * r)244 append_realm(struct tr_realm *head, struct tr_realm *r)
245 {
246 struct tr_realm *p;
247 if(head == NULL){
248 r->next = NULL;
249 return r;
250 }
251 p = head;
252 while(p->next) p = p->next;
253 p->next = r;
254 return head;
255 }
256
257 static int
decode_realms(krb5_context context,const char * tr,int length,struct tr_realm ** realms)258 decode_realms(krb5_context context,
259 const char *tr, int length, struct tr_realm **realms)
260 {
261 struct tr_realm *r = NULL;
262
263 char *tmp;
264 int quote = 0;
265 const char *start = tr;
266 int i;
267
268 for(i = 0; i < length; i++){
269 if(quote){
270 quote = 0;
271 continue;
272 }
273 if(tr[i] == '\\'){
274 quote = 1;
275 continue;
276 }
277 if(tr[i] == ','){
278 tmp = malloc(tr + i - start + 1);
279 if(tmp == NULL)
280 return krb5_enomem(context);
281 memcpy(tmp, start, tr + i - start);
282 tmp[tr + i - start] = '\0';
283 r = make_realm(tmp);
284 if(r == NULL){
285 free_realms(*realms);
286 *realms = NULL;
287 return krb5_enomem(context);
288 }
289 *realms = append_realm(*realms, r);
290 start = tr + i + 1;
291 }
292 }
293 tmp = malloc(tr + i - start + 1);
294 if(tmp == NULL){
295 free_realms(*realms);
296 *realms = NULL;
297 return krb5_enomem(context);
298 }
299 memcpy(tmp, start, tr + i - start);
300 tmp[tr + i - start] = '\0';
301 r = make_realm(tmp);
302 if(r == NULL){
303 free_realms(*realms);
304 *realms = NULL;
305 return krb5_enomem(context);
306 }
307 *realms = append_realm(*realms, r);
308
309 return 0;
310 }
311
312
313 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_domain_x500_decode(krb5_context context,krb5_data tr,char *** realms,unsigned int * num_realms,const char * client_realm,const char * server_realm)314 krb5_domain_x500_decode(krb5_context context,
315 krb5_data tr, char ***realms, unsigned int *num_realms,
316 const char *client_realm, const char *server_realm)
317 {
318 struct tr_realm *r = NULL;
319 struct tr_realm *p, **q;
320 int ret;
321
322 if(tr.length == 0) {
323 *realms = NULL;
324 *num_realms = 0;
325 return 0;
326 }
327
328 /* split string in components */
329 ret = decode_realms(context, tr.data, tr.length, &r);
330 if(ret)
331 return ret;
332
333 /* apply prefix rule */
334 ret = expand_realms(context, r, client_realm);
335 if(ret)
336 return ret;
337
338 ret = make_paths(context, r, client_realm, server_realm);
339 if(ret)
340 return ret;
341
342 /* remove empty components and count realms */
343 *num_realms = 0;
344 for(q = &r; *q; ){
345 if((*q)->realm[0] == '\0'){
346 p = *q;
347 *q = (*q)->next;
348 free(p->realm);
349 free(p);
350 }else{
351 q = &(*q)->next;
352 (*num_realms)++;
353 }
354 }
355 if (*num_realms + 1 > UINT_MAX/sizeof(**realms))
356 return ERANGE;
357
358 {
359 char **R;
360 R = malloc((*num_realms + 1) * sizeof(*R));
361 if (R == NULL)
362 return krb5_enomem(context);
363 *realms = R;
364 while(r){
365 *R++ = r->realm;
366 p = r->next;
367 free(r);
368 r = p;
369 }
370 }
371 return 0;
372 }
373
374 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_domain_x500_encode(char ** realms,unsigned int num_realms,krb5_data * encoding)375 krb5_domain_x500_encode(char **realms, unsigned int num_realms,
376 krb5_data *encoding)
377 {
378 char *s = NULL;
379 int len = 0;
380 unsigned int i;
381 krb5_data_zero(encoding);
382 if (num_realms == 0)
383 return 0;
384 for(i = 0; i < num_realms; i++){
385 len += strlen(realms[i]);
386 if(realms[i][0] == '/')
387 len++;
388 }
389 len += num_realms - 1;
390 s = malloc(len + 1);
391 if (s == NULL)
392 return ENOMEM;
393 *s = '\0';
394 for(i = 0; i < num_realms; i++){
395 if(i)
396 strlcat(s, ",", len + 1);
397 if(realms[i][0] == '/')
398 strlcat(s, " ", len + 1);
399 strlcat(s, realms[i], len + 1);
400 }
401 encoding->data = s;
402 encoding->length = strlen(s);
403 return 0;
404 }
405
406 KRB5_LIB_FUNCTION void KRB5_LIB_CALL
_krb5_free_capath(krb5_context context,char ** capath)407 _krb5_free_capath(krb5_context context, char **capath)
408 {
409 char **s;
410
411 for (s = capath; s && *s; ++s)
412 free(*s);
413 free(capath);
414 }
415
416 struct hier_iter {
417 const char *local_realm;
418 const char *server_realm;
419 const char *lr; /* Pointer into tail of local realm */
420 const char *sr; /* Pointer into tail of server realm */
421 size_t llen; /* Length of local_realm */
422 size_t slen; /* Length of server_realm */
423 size_t len; /* Length of common suffix */
424 size_t num; /* Path element count */
425 };
426
427 /*
428 * Step up from local_realm to common suffix, or else down to server_realm.
429 */
430 static const char *
hier_next(struct hier_iter * state)431 hier_next(struct hier_iter *state)
432 {
433 const char *lr = state->lr;
434 const char *sr = state->sr;
435 const char *lsuffix = state->local_realm + state->llen - state->len;
436 const char *server_realm = state->server_realm;
437
438 if (lr != NULL) {
439 while (lr < lsuffix)
440 if (*lr++ == '.')
441 return state->lr = lr;
442 state->lr = NULL;
443 }
444 if (sr != NULL) {
445 while (--sr >= server_realm)
446 if (sr == server_realm || sr[-1] == '.')
447 return state->sr = sr;
448 state->sr = NULL;
449 }
450 return NULL;
451 }
452
453 static void
hier_init(struct hier_iter * state,const char * local_realm,const char * server_realm)454 hier_init(struct hier_iter *state, const char *local_realm, const char *server_realm)
455 {
456 size_t llen;
457 size_t slen;
458 size_t len = 0;
459 const char *lr;
460 const char *sr;
461
462 state->local_realm = local_realm;
463 state->server_realm = server_realm;
464 state->llen = llen = strlen(local_realm);
465 state->slen = slen = strlen(server_realm);
466 state->len = 0;
467 state->num = 0;
468
469 if (slen == 0 || llen == 0)
470 return;
471
472 /* Find first difference from the back */
473 for (lr = local_realm + llen, sr = server_realm + slen;
474 lr != local_realm && sr != server_realm;
475 --lr, --sr) {
476 if (lr[-1] != sr[-1])
477 break;
478 if (lr[-1] == '.')
479 len = llen - (lr - local_realm);
480 }
481
482 /* Nothing in common? */
483 if (*lr == '\0')
484 return;
485
486 /* Everything in common? */
487 if (llen == slen && lr == local_realm)
488 return;
489
490 /* Is one realm is a suffix of the other? */
491 if ((llen < slen && lr == local_realm && sr[-1] == '.') ||
492 (llen > slen && sr == server_realm && lr[-1] == '.'))
493 len = llen - (lr - local_realm);
494
495 state->len = len;
496 /* `lr` starts at local realm and walks up the tree to common suffix */
497 state->lr = local_realm;
498 /* `sr` starts at common suffix in server realm and walks down the tree */
499 state->sr = server_realm + slen - len;
500
501 /* Count elements and reset */
502 while (hier_next(state) != NULL)
503 ++state->num;
504 state->lr = local_realm;
505 state->sr = server_realm + slen - len;
506 }
507
508 /*
509 * Find a referral path from client_realm to server_realm via local_realm.
510 * Either via [capaths] or hierarchicaly.
511 */
512 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
_krb5_find_capath(krb5_context context,const char * client_realm,const char * local_realm,const char * server_realm,krb5_boolean use_hierarchical,char *** rpath,size_t * npath)513 _krb5_find_capath(krb5_context context,
514 const char *client_realm,
515 const char *local_realm,
516 const char *server_realm,
517 krb5_boolean use_hierarchical,
518 char ***rpath,
519 size_t *npath)
520 {
521 char **confpath;
522 char **capath;
523 struct hier_iter hier_state;
524 char **rp;
525 const char *r;
526
527 *rpath = NULL;
528 *npath = 0;
529
530 confpath = krb5_config_get_strings(context, NULL, "capaths",
531 client_realm, server_realm, NULL);
532 if (confpath == NULL)
533 confpath = krb5_config_get_strings(context, NULL, "capaths",
534 local_realm, server_realm, NULL);
535 /*
536 * With a [capaths] setting from the client to the server we look for our
537 * own realm in the list. If our own realm is not present, we return the
538 * full list. Otherwise, we return our realm's successors, or possibly
539 * NULL. Ignoring a [capaths] settings risks loops plus would violate
540 * explicit policy and the principle of least surpise.
541 */
542 if (confpath != NULL) {
543 char **start = confpath;
544 size_t i;
545 size_t n;
546
547 for (rp = start; *rp; rp++)
548 if (strcmp(*rp, local_realm) == 0)
549 start = rp+1;
550 n = rp - start;
551
552 if (n == 0) {
553 krb5_config_free_strings(confpath);
554 return 0;
555 }
556
557 capath = calloc(n + 1, sizeof(*capath));
558 if (capath == NULL) {
559 krb5_config_free_strings(confpath);
560 return krb5_enomem(context);
561 }
562
563 for (i = 0, rp = start; *rp; rp++) {
564 if ((capath[i++] = strdup(*rp)) == NULL) {
565 _krb5_free_capath(context, capath);
566 krb5_config_free_strings(confpath);
567 return krb5_enomem(context);
568 }
569 }
570 krb5_config_free_strings(confpath);
571 capath[i] = NULL;
572 *rpath = capath;
573 *npath = n;
574 return 0;
575 }
576
577 /* The use_hierarchical flag makes hierarchical path lookup unconditional */
578 if (! use_hierarchical &&
579 ! krb5_config_get_bool_default(context, NULL, TRUE, "libdefaults",
580 "allow_hierarchical_capaths", NULL))
581 return 0;
582
583 /*
584 * When validating transit paths, local_realm == client_realm. Otherwise,
585 * with hierarchical referrals, they may differ, and we may be building a
586 * path forward from our own realm!
587 */
588 hier_init(&hier_state, local_realm, server_realm);
589 if (hier_state.num == 0)
590 return 0;
591
592 rp = capath = calloc(hier_state.num + 1, sizeof(*capath));
593 if (capath == NULL)
594 return krb5_enomem(context);
595 while ((r = hier_next(&hier_state)) != NULL) {
596 if ((*rp++ = strdup(r)) == NULL) {
597 _krb5_free_capath(context, capath);
598 return krb5_enomem(context);
599 }
600 }
601
602 *rp = NULL;
603 *rpath = capath;
604 *npath = hier_state.num;
605 return 0;
606 }
607
608 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_check_transited(krb5_context context,krb5_const_realm client_realm,krb5_const_realm server_realm,krb5_realm * realms,unsigned int num_realms,int * bad_realm)609 krb5_check_transited(krb5_context context,
610 krb5_const_realm client_realm,
611 krb5_const_realm server_realm,
612 krb5_realm *realms,
613 unsigned int num_realms,
614 int *bad_realm)
615 {
616 krb5_error_code ret = 0;
617 char **capath = NULL;
618 size_t num_capath = 0;
619 size_t i = 0;
620 size_t j = 0;
621
622 /* In transit checks hierarchical capaths are optional */
623 ret = _krb5_find_capath(context, client_realm, client_realm, server_realm,
624 FALSE, &capath, &num_capath);
625 if (ret)
626 return ret;
627
628 for (i = 0; i < num_realms; i++) {
629 for (j = 0; j < num_capath; ++j) {
630 if (strcmp(realms[i], capath[j]) == 0)
631 break;
632 }
633 if (j == num_capath) {
634 _krb5_free_capath(context, capath);
635 krb5_set_error_message (context, KRB5KRB_AP_ERR_ILL_CR_TKT,
636 N_("no transit allowed "
637 "through realm %s from %s to %s", ""),
638 realms[i], client_realm, server_realm);
639 if (bad_realm)
640 *bad_realm = i;
641 return KRB5KRB_AP_ERR_ILL_CR_TKT;
642 }
643 }
644
645 _krb5_free_capath(context, capath);
646 return 0;
647 }
648
649 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_check_transited_realms(krb5_context context,const char * const * realms,unsigned int num_realms,int * bad_realm)650 krb5_check_transited_realms(krb5_context context,
651 const char *const *realms,
652 unsigned int num_realms,
653 int *bad_realm)
654 {
655 size_t i;
656 int ret = 0;
657 char **bad_realms = krb5_config_get_strings(context, NULL,
658 "libdefaults",
659 "transited_realms_reject",
660 NULL);
661 if(bad_realms == NULL)
662 return 0;
663
664 for(i = 0; i < num_realms; i++) {
665 char **p;
666 for(p = bad_realms; *p; p++)
667 if(strcmp(*p, realms[i]) == 0) {
668 ret = KRB5KRB_AP_ERR_ILL_CR_TKT;
669 krb5_set_error_message (context, ret,
670 N_("no transit allowed "
671 "through realm %s", ""),
672 *p);
673 if(bad_realm)
674 *bad_realm = i;
675 break;
676 }
677 }
678 krb5_config_free_strings(bad_realms);
679 return ret;
680 }
681
682 #if 0
683 int
684 main(int argc, char **argv)
685 {
686 krb5_data x;
687 char **r;
688 int num, i;
689 x.data = argv[1];
690 x.length = strlen(x.data);
691 if(domain_expand(x, &r, &num, argv[2], argv[3]))
692 exit(1);
693 for(i = 0; i < num; i++)
694 printf("%s\n", r[i]);
695 return 0;
696 }
697 #endif
698