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 H��gskolan
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
43struct 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
51static void
52free_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
63static int
64make_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
132static int
133make_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
163static int
164expand_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
207static struct tr_realm *
208make_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
243static struct tr_realm*
244append_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
257static int
258decode_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
313KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
314krb5_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
374KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
375krb5_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
406KRB5_LIB_FUNCTION void KRB5_LIB_CALL
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
416struct 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 */
430static const char *
431hier_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
453static void
454hier_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 */
512KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
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
608KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
609krb5_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
649KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
650krb5_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
683int
684main(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