1/*
2 * Copyright (c) 1995 - 2006 Kungliga Tekniska H�gskolan
3 * (Royal Institute of Technology, Stockholm, Sweden).
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * 3. Neither the name of the Institute nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#ifdef HAVE_CONFIG_H
35#include <config.h>
36#endif
37#include "roken.h"
38#ifdef HAVE_ARPA_NAMESER_H
39#include <arpa/nameser.h>
40#endif
41#ifdef HAVE_RESOLV_H
42#include <resolv.h>
43#endif
44#include "resolve.h"
45
46#include <assert.h>
47
48RCSID("$Id: resolve.c 19869 2007-01-12 16:03:14Z lha $");
49
50#ifdef _AIX /* AIX have broken res_nsearch() in 5.1 (5.0 also ?) */
51#undef HAVE_RES_NSEARCH
52#endif
53
54#define DECL(X) {#X, rk_ns_t_##X}
55
56static struct stot{
57    const char *name;
58    int type;
59}stot[] = {
60    DECL(a),
61    DECL(aaaa),
62    DECL(ns),
63    DECL(cname),
64    DECL(soa),
65    DECL(ptr),
66    DECL(mx),
67    DECL(txt),
68    DECL(afsdb),
69    DECL(sig),
70    DECL(key),
71    DECL(srv),
72    DECL(naptr),
73    DECL(sshfp),
74    DECL(ds),
75    {NULL, 	0}
76};
77
78int _resolve_debug = 0;
79
80int ROKEN_LIB_FUNCTION
81dns_string_to_type(const char *name)
82{
83    struct stot *p = stot;
84    for(p = stot; p->name; p++)
85	if(strcasecmp(name, p->name) == 0)
86	    return p->type;
87    return -1;
88}
89
90const char * ROKEN_LIB_FUNCTION
91dns_type_to_string(int type)
92{
93    struct stot *p = stot;
94    for(p = stot; p->name; p++)
95	if(type == p->type)
96	    return p->name;
97    return NULL;
98}
99
100#if (defined(HAVE_RES_SEARCH) || defined(HAVE_RES_NSEARCH)) && defined(HAVE_DN_EXPAND)
101
102static void
103dns_free_rr(struct resource_record *rr)
104{
105    if(rr->domain)
106	free(rr->domain);
107    if(rr->u.data)
108	free(rr->u.data);
109    free(rr);
110}
111
112void ROKEN_LIB_FUNCTION
113dns_free_data(struct dns_reply *r)
114{
115    struct resource_record *rr;
116    if(r->q.domain)
117	free(r->q.domain);
118    for(rr = r->head; rr;){
119	struct resource_record *tmp = rr;
120	rr = rr->next;
121	dns_free_rr(tmp);
122    }
123    free (r);
124}
125
126static int
127parse_record(const unsigned char *data, const unsigned char *end_data,
128	     const unsigned char **pp, struct resource_record **ret_rr)
129{
130    struct resource_record *rr;
131    int type, class, ttl, size;
132    int status;
133    char host[MAXDNAME];
134    const unsigned char *p = *pp;
135
136    *ret_rr = NULL;
137
138    status = dn_expand(data, end_data, p, host, sizeof(host));
139    if(status < 0)
140	return -1;
141    if (p + status + 10 > end_data)
142	return -1;
143
144    p += status;
145    type = (p[0] << 8) | p[1];
146    p += 2;
147    class = (p[0] << 8) | p[1];
148    p += 2;
149    ttl = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
150    p += 4;
151    size = (p[0] << 8) | p[1];
152    p += 2;
153
154    if (p + size > end_data)
155	return -1;
156
157    rr = calloc(1, sizeof(*rr));
158    if(rr == NULL)
159	return -1;
160    rr->domain = strdup(host);
161    if(rr->domain == NULL) {
162	dns_free_rr(rr);
163	return -1;
164    }
165    rr->type = type;
166    rr->class = class;
167    rr->ttl = ttl;
168    rr->size = size;
169    switch(type){
170    case rk_ns_t_ns:
171    case rk_ns_t_cname:
172    case rk_ns_t_ptr:
173	status = dn_expand(data, end_data, p, host, sizeof(host));
174	if(status < 0) {
175	    dns_free_rr(rr);
176	    return -1;
177	}
178	rr->u.txt = strdup(host);
179	if(rr->u.txt == NULL) {
180	    dns_free_rr(rr);
181	    return -1;
182	}
183	break;
184    case rk_ns_t_mx:
185    case rk_ns_t_afsdb:{
186	size_t hostlen;
187
188	status = dn_expand(data, end_data, p + 2, host, sizeof(host));
189	if(status < 0){
190	    dns_free_rr(rr);
191	    return -1;
192	}
193	if (status + 2 > size) {
194	    dns_free_rr(rr);
195	    return -1;
196	}
197
198	hostlen = strlen(host);
199	rr->u.mx = (struct mx_record*)malloc(sizeof(struct mx_record) +
200						hostlen);
201	if(rr->u.mx == NULL) {
202	    dns_free_rr(rr);
203	    return -1;
204	}
205	rr->u.mx->preference = (p[0] << 8) | p[1];
206	strlcpy(rr->u.mx->domain, host, hostlen + 1);
207	break;
208    }
209    case rk_ns_t_srv:{
210	size_t hostlen;
211	status = dn_expand(data, end_data, p + 6, host, sizeof(host));
212	if(status < 0){
213	    dns_free_rr(rr);
214	    return -1;
215	}
216	if (status + 6 > size) {
217	    dns_free_rr(rr);
218	    return -1;
219	}
220
221	hostlen = strlen(host);
222	rr->u.srv =
223	    (struct srv_record*)malloc(sizeof(struct srv_record) +
224				       hostlen);
225	if(rr->u.srv == NULL) {
226	    dns_free_rr(rr);
227	    return -1;
228	}
229	rr->u.srv->priority = (p[0] << 8) | p[1];
230	rr->u.srv->weight = (p[2] << 8) | p[3];
231	rr->u.srv->port = (p[4] << 8) | p[5];
232	strlcpy(rr->u.srv->target, host, hostlen + 1);
233	break;
234    }
235    case rk_ns_t_txt:{
236	if(size == 0 || size < *p + 1) {
237	    dns_free_rr(rr);
238	    return -1;
239	}
240	rr->u.txt = (char*)malloc(*p + 1);
241	if(rr->u.txt == NULL) {
242	    dns_free_rr(rr);
243	    return -1;
244	}
245	strncpy(rr->u.txt, (const char*)(p + 1), *p);
246	rr->u.txt[*p] = '\0';
247	break;
248    }
249    case rk_ns_t_key : {
250	size_t key_len;
251
252	if (size < 4) {
253	    dns_free_rr(rr);
254	    return -1;
255	}
256
257	key_len = size - 4;
258	rr->u.key = malloc (sizeof(*rr->u.key) + key_len - 1);
259	if (rr->u.key == NULL) {
260	    dns_free_rr(rr);
261	    return -1;
262	}
263
264	rr->u.key->flags     = (p[0] << 8) | p[1];
265	rr->u.key->protocol  = p[2];
266	rr->u.key->algorithm = p[3];
267	rr->u.key->key_len   = key_len;
268	memcpy (rr->u.key->key_data, p + 4, key_len);
269	break;
270    }
271    case rk_ns_t_sig : {
272	size_t sig_len, hostlen;
273
274	if(size <= 18) {
275	    dns_free_rr(rr);
276	    return -1;
277	}
278	status = dn_expand (data, end_data, p + 18, host, sizeof(host));
279	if (status < 0) {
280	    dns_free_rr(rr);
281	    return -1;
282	}
283	if (status + 18 > size) {
284	    dns_free_rr(rr);
285	    return -1;
286	}
287
288	/* the signer name is placed after the sig_data, to make it
289           easy to free this structure; the size calculation below
290           includes the zero-termination if the structure itself.
291	   don't you just love C?
292	*/
293	sig_len = size - 18 - status;
294	hostlen = strlen(host);
295	rr->u.sig = malloc(sizeof(*rr->u.sig)
296			      + hostlen + sig_len);
297	if (rr->u.sig == NULL) {
298	    dns_free_rr(rr);
299	    return -1;
300	}
301	rr->u.sig->type           = (p[0] << 8) | p[1];
302	rr->u.sig->algorithm      = p[2];
303	rr->u.sig->labels         = p[3];
304	rr->u.sig->orig_ttl       = (p[4] << 24) | (p[5] << 16)
305	    | (p[6] << 8) | p[7];
306	rr->u.sig->sig_expiration = (p[8] << 24) | (p[9] << 16)
307	    | (p[10] << 8) | p[11];
308	rr->u.sig->sig_inception  = (p[12] << 24) | (p[13] << 16)
309	    | (p[14] << 8) | p[15];
310	rr->u.sig->key_tag        = (p[16] << 8) | p[17];
311	rr->u.sig->sig_len        = sig_len;
312	memcpy (rr->u.sig->sig_data, p + 18 + status, sig_len);
313	rr->u.sig->signer         = &rr->u.sig->sig_data[sig_len];
314	strlcpy(rr->u.sig->signer, host, hostlen + 1);
315	break;
316    }
317
318    case rk_ns_t_cert : {
319	size_t cert_len;
320
321	if (size < 5) {
322	    dns_free_rr(rr);
323	    return -1;
324	}
325
326	cert_len = size - 5;
327	rr->u.cert = malloc (sizeof(*rr->u.cert) + cert_len - 1);
328	if (rr->u.cert == NULL) {
329	    dns_free_rr(rr);
330	    return -1;
331	}
332
333	rr->u.cert->type      = (p[0] << 8) | p[1];
334	rr->u.cert->tag       = (p[2] << 8) | p[3];
335	rr->u.cert->algorithm = p[4];
336	rr->u.cert->cert_len  = cert_len;
337	memcpy (rr->u.cert->cert_data, p + 5, cert_len);
338	break;
339    }
340    case rk_ns_t_sshfp : {
341	size_t sshfp_len;
342
343	if (size < 2) {
344	    dns_free_rr(rr);
345	    return -1;
346	}
347
348	sshfp_len = size - 2;
349
350	rr->u.sshfp = malloc (sizeof(*rr->u.sshfp) + sshfp_len - 1);
351	if (rr->u.sshfp == NULL) {
352	    dns_free_rr(rr);
353	    return -1;
354	}
355
356	rr->u.sshfp->algorithm = p[0];
357	rr->u.sshfp->type      = p[1];
358	rr->u.sshfp->sshfp_len  = sshfp_len;
359	memcpy (rr->u.sshfp->sshfp_data, p + 2, sshfp_len);
360	break;
361    }
362    case rk_ns_t_ds: {
363	size_t digest_len;
364
365	if (size < 4) {
366	    dns_free_rr(rr);
367	    return -1;
368	}
369
370	digest_len = size - 4;
371
372	rr->u.ds = malloc (sizeof(*rr->u.ds) + digest_len - 1);
373	if (rr->u.ds == NULL) {
374	    dns_free_rr(rr);
375	    return -1;
376	}
377
378	rr->u.ds->key_tag     = (p[0] << 8) | p[1];
379	rr->u.ds->algorithm   = p[2];
380	rr->u.ds->digest_type = p[3];
381	rr->u.ds->digest_len  = digest_len;
382	memcpy (rr->u.ds->digest_data, p + 4, digest_len);
383	break;
384    }
385    default:
386	rr->u.data = (unsigned char*)malloc(size);
387	if(size != 0 && rr->u.data == NULL) {
388	    dns_free_rr(rr);
389	    return -1;
390	}
391	if (size)
392	    memcpy(rr->u.data, p, size);
393    }
394    *pp = p + size;
395    *ret_rr = rr;
396
397    return 0;
398}
399
400#ifndef TEST_RESOLVE
401static
402#endif
403struct dns_reply*
404parse_reply(const unsigned char *data, size_t len)
405{
406    const unsigned char *p;
407    int status;
408    int i;
409    char host[MAXDNAME];
410    const unsigned char *end_data = data + len;
411    struct dns_reply *r;
412    struct resource_record **rr;
413
414    r = calloc(1, sizeof(*r));
415    if (r == NULL)
416	return NULL;
417
418    p = data;
419
420    r->h.id = (p[0] << 8) | p[1];
421    r->h.flags = 0;
422    if (p[2] & 0x01)
423	r->h.flags |= rk_DNS_HEADER_RESPONSE_FLAG;
424    r->h.opcode = (p[2] >> 1) & 0xf;
425    if (p[2] & 0x20)
426	r->h.flags |= rk_DNS_HEADER_AUTHORITIVE_ANSWER;
427    if (p[2] & 0x40)
428	r->h.flags |= rk_DNS_HEADER_TRUNCATED_MESSAGE;
429    if (p[2] & 0x80)
430	r->h.flags |= rk_DNS_HEADER_RECURSION_DESIRED;
431    if (p[3] & 0x01)
432	r->h.flags |= rk_DNS_HEADER_RECURSION_AVAILABLE;
433    if (p[3] & 0x04)
434	r->h.flags |= rk_DNS_HEADER_AUTHORITIVE_ANSWER;
435    if (p[3] & 0x08)
436	r->h.flags |= rk_DNS_HEADER_CHECKING_DISABLED;
437    r->h.response_code = (p[3] >> 4) & 0xf;
438    r->h.qdcount = (p[4] << 8) | p[5];
439    r->h.ancount = (p[6] << 8) | p[7];
440    r->h.nscount = (p[8] << 8) | p[9];
441    r->h.arcount = (p[10] << 8) | p[11];
442
443    p += 12;
444
445    if(r->h.qdcount != 1) {
446	free(r);
447	return NULL;
448    }
449    status = dn_expand(data, end_data, p, host, sizeof(host));
450    if(status < 0){
451	dns_free_data(r);
452	return NULL;
453    }
454    r->q.domain = strdup(host);
455    if(r->q.domain == NULL) {
456	dns_free_data(r);
457	return NULL;
458    }
459    if (p + status + 4 > end_data) {
460	dns_free_data(r);
461	return NULL;
462    }
463    p += status;
464    r->q.type = (p[0] << 8 | p[1]);
465    p += 2;
466    r->q.class = (p[0] << 8 | p[1]);
467    p += 2;
468
469    rr = &r->head;
470    for(i = 0; i < r->h.ancount; i++) {
471	if(parse_record(data, end_data, &p, rr) != 0) {
472	    dns_free_data(r);
473	    return NULL;
474	}
475	rr = &(*rr)->next;
476    }
477    for(i = 0; i < r->h.nscount; i++) {
478	if(parse_record(data, end_data, &p, rr) != 0) {
479	    dns_free_data(r);
480	    return NULL;
481	}
482	rr = &(*rr)->next;
483    }
484    for(i = 0; i < r->h.arcount; i++) {
485	if(parse_record(data, end_data, &p, rr) != 0) {
486	    dns_free_data(r);
487	    return NULL;
488	}
489	rr = &(*rr)->next;
490    }
491    *rr = NULL;
492    return r;
493}
494
495#ifdef HAVE_RES_NSEARCH
496#ifdef HAVE_RES_NDESTROY
497#define rk_res_free(x) res_ndestroy(x)
498#else
499#define rk_res_free(x) res_nclose(x)
500#endif
501#endif
502
503static struct dns_reply *
504dns_lookup_int(const char *domain, int rr_class, int rr_type)
505{
506    struct dns_reply *r;
507    unsigned char *reply = NULL;
508    int size;
509    int len;
510#ifdef HAVE_RES_NSEARCH
511    struct __res_state state;
512    memset(&state, 0, sizeof(state));
513    if(res_ninit(&state))
514	return NULL; /* is this the best we can do? */
515#elif defined(HAVE__RES)
516    u_long old_options = 0;
517#endif
518
519    size = 0;
520    len = 1000;
521    do {
522	if (reply) {
523	    free(reply);
524	    reply = NULL;
525	}
526	if (size <= len)
527	    size = len;
528	if (_resolve_debug) {
529#ifdef HAVE_RES_NSEARCH
530	    state.options |= RES_DEBUG;
531#elif defined(HAVE__RES)
532	    old_options = _res.options;
533	    _res.options |= RES_DEBUG;
534#endif
535	    fprintf(stderr, "dns_lookup(%s, %d, %s), buffer size %d\n", domain,
536		    rr_class, dns_type_to_string(rr_type), size);
537	}
538	reply = malloc(size);
539	if (reply == NULL) {
540#ifdef HAVE_RES_NSEARCH
541	    rk_res_free(&state);
542#endif
543	    return NULL;
544	}
545#ifdef HAVE_RES_NSEARCH
546	len = res_nsearch(&state, domain, rr_class, rr_type, reply, size);
547#else
548	len = res_search(domain, rr_class, rr_type, reply, size);
549#endif
550	if (_resolve_debug) {
551#if defined(HAVE__RES) && !defined(HAVE_RES_NSEARCH)
552	    _res.options = old_options;
553#endif
554	    fprintf(stderr, "dns_lookup(%s, %d, %s) --> %d\n",
555		    domain, rr_class, dns_type_to_string(rr_type), len);
556	}
557	if (len < 0) {
558#ifdef HAVE_RES_NSEARCH
559	    rk_res_free(&state);
560#endif
561	    free(reply);
562	    return NULL;
563	}
564    } while (size < len && len < rk_DNS_MAX_PACKET_SIZE);
565#ifdef HAVE_RES_NSEARCH
566    rk_res_free(&state);
567#endif
568
569    len = min(len, size);
570    r = parse_reply(reply, len);
571    free(reply);
572    return r;
573}
574
575struct dns_reply * ROKEN_LIB_FUNCTION
576dns_lookup(const char *domain, const char *type_name)
577{
578    int type;
579
580    type = dns_string_to_type(type_name);
581    if(type == -1) {
582	if(_resolve_debug)
583	    fprintf(stderr, "dns_lookup: unknown resource type: `%s'\n",
584		    type_name);
585	return NULL;
586    }
587    return dns_lookup_int(domain, C_IN, type);
588}
589
590static int
591compare_srv(const void *a, const void *b)
592{
593    const struct resource_record *const* aa = a, *const* bb = b;
594
595    if((*aa)->u.srv->priority == (*bb)->u.srv->priority)
596	return ((*aa)->u.srv->weight - (*bb)->u.srv->weight);
597    return ((*aa)->u.srv->priority - (*bb)->u.srv->priority);
598}
599
600#ifndef HAVE_RANDOM
601#define random() rand()
602#endif
603
604/* try to rearrange the srv-records by the algorithm in RFC2782 */
605void ROKEN_LIB_FUNCTION
606dns_srv_order(struct dns_reply *r)
607{
608    struct resource_record **srvs, **ss, **headp;
609    struct resource_record *rr;
610    int num_srv = 0;
611
612#if defined(HAVE_INITSTATE) && defined(HAVE_SETSTATE)
613    int state[256 / sizeof(int)];
614    char *oldstate;
615#endif
616
617    for(rr = r->head; rr; rr = rr->next)
618	if(rr->type == rk_ns_t_srv)
619	    num_srv++;
620
621    if(num_srv == 0)
622	return;
623
624    srvs = malloc(num_srv * sizeof(*srvs));
625    if(srvs == NULL)
626	return; /* XXX not much to do here */
627
628    /* unlink all srv-records from the linked list and put them in
629       a vector */
630    for(ss = srvs, headp = &r->head; *headp; )
631	if((*headp)->type == rk_ns_t_srv) {
632	    *ss = *headp;
633	    *headp = (*headp)->next;
634	    (*ss)->next = NULL;
635	    ss++;
636	} else
637	    headp = &(*headp)->next;
638
639    /* sort them by priority and weight */
640    qsort(srvs, num_srv, sizeof(*srvs), compare_srv);
641
642#if defined(HAVE_INITSTATE) && defined(HAVE_SETSTATE)
643    oldstate = initstate(time(NULL), (char*)state, sizeof(state));
644#endif
645
646    headp = &r->head;
647
648    for(ss = srvs; ss < srvs + num_srv; ) {
649	int sum, rnd, count;
650	struct resource_record **ee, **tt;
651	/* find the last record with the same priority and count the
652           sum of all weights */
653	for(sum = 0, tt = ss; tt < srvs + num_srv; tt++) {
654	    assert(*tt != NULL);
655	    if((*tt)->u.srv->priority != (*ss)->u.srv->priority)
656		break;
657	    sum += (*tt)->u.srv->weight;
658	}
659	ee = tt;
660	/* ss is now the first record of this priority and ee is the
661           first of the next */
662	while(ss < ee) {
663	    rnd = random() % (sum + 1);
664	    for(count = 0, tt = ss; ; tt++) {
665		if(*tt == NULL)
666		    continue;
667		count += (*tt)->u.srv->weight;
668		if(count >= rnd)
669		    break;
670	    }
671
672	    assert(tt < ee);
673
674	    /* insert the selected record at the tail (of the head) of
675               the list */
676	    (*tt)->next = *headp;
677	    *headp = *tt;
678	    headp = &(*tt)->next;
679	    sum -= (*tt)->u.srv->weight;
680	    *tt = NULL;
681	    while(ss < ee && *ss == NULL)
682		ss++;
683	}
684    }
685
686#if defined(HAVE_INITSTATE) && defined(HAVE_SETSTATE)
687    setstate(oldstate);
688#endif
689    free(srvs);
690    return;
691}
692
693#else /* NOT defined(HAVE_RES_SEARCH) && defined(HAVE_DN_EXPAND) */
694
695struct dns_reply * ROKEN_LIB_FUNCTION
696dns_lookup(const char *domain, const char *type_name)
697{
698    return NULL;
699}
700
701void ROKEN_LIB_FUNCTION
702dns_free_data(struct dns_reply *r)
703{
704}
705
706void ROKEN_LIB_FUNCTION
707dns_srv_order(struct dns_reply *r)
708{
709}
710
711#endif
712