1 /* $NetBSD: res_query.c,v 1.16 2015/02/24 17:56:20 christos Exp $ */
2
3 /*
4 * Portions Copyright (C) 2004, 2005, 2008 Internet Systems Consortium, Inc. ("ISC")
5 * Portions Copyright (C) 1996-2001, 2003 Internet Software Consortium.
6 *
7 * Permission to use, copy, modify, and/or distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
12 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
13 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
14 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
15 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
16 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
17 * PERFORMANCE OF THIS SOFTWARE.
18 */
19
20 /*
21 * Copyright (c) 1988, 1993
22 * The Regents of the University of California. All rights reserved.
23 *
24 * Redistribution and use in source and binary forms, with or without
25 * modification, are permitted provided that the following conditions
26 * are met:
27 * 1. Redistributions of source code must retain the above copyright
28 * notice, this list of conditions and the following disclaimer.
29 * 2. Redistributions in binary form must reproduce the above copyright
30 * notice, this list of conditions and the following disclaimer in the
31 * documentation and/or other materials provided with the distribution.
32 * 3. Neither the name of the University nor the names of its contributors
33 * may be used to endorse or promote products derived from this software
34 * without specific prior written permission.
35 *
36 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
37 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
39 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
40 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
41 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
42 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
43 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
44 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
45 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
46 * SUCH DAMAGE.
47 */
48
49 /*
50 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
51 *
52 * Permission to use, copy, modify, and distribute this software for any
53 * purpose with or without fee is hereby granted, provided that the above
54 * copyright notice and this permission notice appear in all copies, and that
55 * the name of Digital Equipment Corporation not be used in advertising or
56 * publicity pertaining to distribution of the document or software without
57 * specific, written prior permission.
58 *
59 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
60 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
61 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
62 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
63 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
64 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
65 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
66 * SOFTWARE.
67 */
68
69 /*
70 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
71 * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
72 *
73 * Permission to use, copy, modify, and distribute this software for any
74 * purpose with or without fee is hereby granted, provided that the above
75 * copyright notice and this permission notice appear in all copies.
76 *
77 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
78 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
79 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
80 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
81 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
82 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
83 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
84 */
85
86 #include <sys/cdefs.h>
87 #if defined(LIBC_SCCS) && !defined(lint)
88 #ifdef notdef
89 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
90 static const char rcsid[] = "Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp";
91 #else
92 __RCSID("$NetBSD: res_query.c,v 1.16 2015/02/24 17:56:20 christos Exp $");
93 #endif
94 #endif /* LIBC_SCCS and not lint */
95
96 #include "port_before.h"
97
98 #include "namespace.h"
99 #include <sys/types.h>
100 #include <sys/param.h>
101 #include <netinet/in.h>
102 #include <arpa/inet.h>
103 #include <arpa/nameser.h>
104 #include <ctype.h>
105 #include <errno.h>
106 #include <netdb.h>
107 #include <resolv.h>
108 #include <stdio.h>
109 #include <stdlib.h>
110 #include <unistd.h>
111 #include <string.h>
112 #include "port_after.h"
113
114 #if 0
115 #ifdef __weak_alias
116 __weak_alias(res_nquery,_res_nquery)
117 __weak_alias(res_nsearch,_res_nsearch)
118 __weak_alias(res_nquerydomain,__res_nquerydomain)
119 __weak_alias(res_hostalias,__res_hostalias)
120 #endif
121 #endif
122
123 /* Options. Leave them on. */
124 #ifndef DEBUG
125 #define DEBUG
126 #endif
127
128 #if PACKETSZ > 1024
129 #define MAXPACKET PACKETSZ
130 #else
131 #define MAXPACKET 1024
132 #endif
133
134 /*%
135 * Formulate a normal query, send, and await answer.
136 * Returned answer is placed in supplied buffer "answer".
137 * Perform preliminary check of answer, returning success only
138 * if no error is indicated and the answer count is nonzero.
139 * Return the size of the response on success, -1 on error.
140 * Error number is left in H_ERRNO.
141 *
142 * Caller must parse answer and determine whether it answers the question.
143 */
144 int
res_nquery(res_state statp,const char * name,int class,int type,u_char * answer,int anslen)145 res_nquery(res_state statp,
146 const char *name, /*%< domain name */
147 int class, int type, /*%< class and type of query */
148 u_char *answer, /*%< buffer to put answer */
149 int anslen) /*%< size of answer buffer */
150 {
151 u_char buf[MAXPACKET];
152 HEADER *hp = (HEADER *)(void *)answer;
153 u_int oflags;
154 u_char *rdata;
155 int n;
156
157 oflags = statp->_flags;
158
159 again:
160 hp->rcode = NOERROR; /*%< default */
161 #ifdef DEBUG
162 if (statp->options & RES_DEBUG)
163 printf(";; res_query(%s, %d, %d)\n", name, class, type);
164 #endif
165
166 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
167 buf, (int)sizeof(buf));
168 #ifdef RES_USE_EDNS0
169 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
170 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID)) != 0U) {
171 n = res_nopt(statp, n, buf, (int)sizeof(buf), anslen);
172 rdata = &buf[n];
173 if (n > 0 && (statp->options & RES_NSID) != 0U) {
174 n = res_nopt_rdata(statp, n, buf, (int)sizeof(buf),
175 rdata, NS_OPT_NSID, 0, NULL);
176 }
177 }
178 #endif
179 if (n <= 0) {
180 #ifdef DEBUG
181 if (statp->options & RES_DEBUG)
182 printf(";; res_query: mkquery failed\n");
183 #endif
184 RES_SET_H_ERRNO(statp, NO_RECOVERY);
185 return (n);
186 }
187
188 n = res_nsend(statp, buf, n, answer, anslen);
189 if (n < 0) {
190 #ifdef RES_USE_EDNS0
191 /* if the query choked with EDNS0, retry without EDNS0 */
192 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
193 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
194 statp->_flags |= RES_F_EDNS0ERR;
195 if (statp->options & RES_DEBUG)
196 printf(";; res_nquery: retry without EDNS0\n");
197 goto again;
198 }
199 #endif
200 #ifdef DEBUG
201 if (statp->options & RES_DEBUG)
202 printf(";; res_query: send error\n");
203 #endif
204 RES_SET_H_ERRNO(statp, TRY_AGAIN);
205 return (n);
206 }
207
208 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
209 #ifdef DEBUG
210 if (statp->options & RES_DEBUG)
211 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
212 p_rcode(hp->rcode),
213 ntohs(hp->ancount),
214 ntohs(hp->nscount),
215 ntohs(hp->arcount));
216 #endif
217 switch (hp->rcode) {
218 case NXDOMAIN:
219 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
220 break;
221 case SERVFAIL:
222 RES_SET_H_ERRNO(statp, TRY_AGAIN);
223 break;
224 case NOERROR:
225 RES_SET_H_ERRNO(statp, NO_DATA);
226 break;
227 case FORMERR:
228 case NOTIMP:
229 case REFUSED:
230 default:
231 RES_SET_H_ERRNO(statp, NO_RECOVERY);
232 break;
233 }
234 return (-1);
235 }
236 return (n);
237 }
238
239 /*%
240 * Formulate a normal query, send, and retrieve answer in supplied buffer.
241 * Return the size of the response on success, -1 on error.
242 * If enabled, implement search rules until answer or unrecoverable failure
243 * is detected. Error code, if any, is left in H_ERRNO.
244 */
245 int
res_nsearch(res_state statp,const char * name,int class,int type,u_char * answer,int anslen)246 res_nsearch(res_state statp,
247 const char *name, /*%< domain name */
248 int class, int type, /*%< class and type of query */
249 u_char *answer, /*%< buffer to put answer */
250 int anslen) /*%< size of answer */
251 {
252 const char *cp, * const *domain;
253 HEADER *hp = (HEADER *)(void *)answer;
254 char tmp[NS_MAXDNAME];
255 u_int dots;
256 int trailing_dot, ret, saved_herrno;
257 int got_nodata = 0, got_servfail = 0, root_on_list = 0;
258 int tried_as_is = 0;
259 int searched = 0;
260
261 errno = 0;
262 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */
263 dots = 0;
264 for (cp = name; *cp != '\0'; cp++)
265 dots += (*cp == '.');
266 trailing_dot = 0;
267 if (cp > name && *--cp == '.')
268 trailing_dot++;
269
270 /* If there aren't any dots, it could be a user-level alias. */
271 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
272 return (res_nquery(statp, cp, class, type, answer, anslen));
273
274 /*
275 * If there are enough dots in the name, let's just give it a
276 * try 'as is'. The threshold can be set with the "ndots" option.
277 * Also, query 'as is', if there is a trailing dot in the name.
278 */
279 saved_herrno = -1;
280 if (dots >= statp->ndots || trailing_dot) {
281 ret = res_nquerydomain(statp, name, NULL, class, type,
282 answer, anslen);
283 if (ret > 0 || trailing_dot)
284 return (ret);
285 saved_herrno = statp->res_h_errno;
286 tried_as_is++;
287 }
288
289 /*
290 * We do at least one level of search if
291 * - there is no dot and RES_DEFNAME is set, or
292 * - there is at least one dot, there is no trailing dot,
293 * and RES_DNSRCH is set.
294 */
295 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
296 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
297 int done = 0;
298
299 for (domain = (const char * const *)statp->dnsrch;
300 *domain && !done;
301 domain++) {
302 searched = 1;
303
304 if (domain[0][0] == '\0' ||
305 (domain[0][0] == '.' && domain[0][1] == '\0'))
306 root_on_list++;
307
308 ret = res_nquerydomain(statp, name, *domain,
309 class, type,
310 answer, anslen);
311 if (ret > 0)
312 return (ret);
313
314 /*
315 * If no server present, give up.
316 * If name isn't found in this domain,
317 * keep trying higher domains in the search list
318 * (if that's enabled).
319 * On a NO_DATA error, keep trying, otherwise
320 * a wildcard entry of another type could keep us
321 * from finding this entry higher in the domain.
322 * If we get some other error (negative answer or
323 * server failure), then stop searching up,
324 * but try the input name below in case it's
325 * fully-qualified.
326 */
327 if (errno == ECONNREFUSED) {
328 RES_SET_H_ERRNO(statp, TRY_AGAIN);
329 return (-1);
330 }
331
332 switch (statp->res_h_errno) {
333 case NO_DATA:
334 got_nodata++;
335 /* FALLTHROUGH */
336 case HOST_NOT_FOUND:
337 /* keep trying */
338 break;
339 case TRY_AGAIN:
340 if (hp->rcode == SERVFAIL) {
341 /* try next search element, if any */
342 got_servfail++;
343 break;
344 }
345 /* FALLTHROUGH */
346 default:
347 /* anything else implies that we're done */
348 done++;
349 }
350
351 /* if we got here for some reason other than DNSRCH,
352 * we only wanted one iteration of the loop, so stop.
353 */
354 if ((statp->options & RES_DNSRCH) == 0U)
355 done++;
356 }
357 }
358
359 /*
360 * If the query has not already been tried as is then try it
361 * unless RES_NOTLDQUERY is set and there were no dots.
362 */
363 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
364 !(tried_as_is || root_on_list)) {
365 ret = res_nquerydomain(statp, name, NULL, class, type,
366 answer, anslen);
367 if (ret > 0)
368 return (ret);
369 }
370
371 /* if we got here, we didn't satisfy the search.
372 * if we did an initial full query, return that query's H_ERRNO
373 * (note that we wouldn't be here if that query had succeeded).
374 * else if we ever got a nodata, send that back as the reason.
375 * else send back meaningless H_ERRNO, that being the one from
376 * the last DNSRCH we did.
377 */
378 if (saved_herrno != -1)
379 RES_SET_H_ERRNO(statp, saved_herrno);
380 else if (got_nodata)
381 RES_SET_H_ERRNO(statp, NO_DATA);
382 else if (got_servfail)
383 RES_SET_H_ERRNO(statp, TRY_AGAIN);
384 return (-1);
385 }
386
387 /*%
388 * Perform a call on res_query on the concatenation of name and domain,
389 * removing a trailing dot from name if domain is NULL.
390 */
391 int
res_nquerydomain(res_state statp,const char * name,const char * domain,int class,int type,u_char * answer,int anslen)392 res_nquerydomain(res_state statp,
393 const char *name,
394 const char *domain,
395 int class, int type, /*%< class and type of query */
396 u_char *answer, /*%< buffer to put answer */
397 int anslen) /*%< size of answer */
398 {
399 char nbuf[MAXDNAME];
400 const char *longname = nbuf;
401 size_t n, d;
402
403 #ifdef DEBUG
404 if (statp->options & RES_DEBUG)
405 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
406 name, domain?domain:"<Nil>", class, type);
407 #endif
408 if (domain == NULL) {
409 /*
410 * Check for trailing '.';
411 * copy without '.' if present.
412 */
413 n = strlen(name);
414 if (n >= MAXDNAME) {
415 RES_SET_H_ERRNO(statp, NO_RECOVERY);
416 return (-1);
417 }
418 if (n && name[--n] == '.') {
419 strncpy(nbuf, name, n);
420 nbuf[n] = '\0';
421 } else
422 longname = name;
423 } else {
424 n = strlen(name);
425 d = strlen(domain);
426 if (n + d + 1 >= MAXDNAME) {
427 RES_SET_H_ERRNO(statp, NO_RECOVERY);
428 return (-1);
429 }
430 sprintf(nbuf, "%s.%s", name, domain);
431 }
432 return (res_nquery(statp, longname, class, type, answer, anslen));
433 }
434
435 const char *
res_hostalias(const res_state statp,const char * name,char * dst,size_t siz)436 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
437 char *file, *cp1, *cp2;
438 char buf[BUFSIZ];
439 FILE *fp;
440
441 if (statp->options & RES_NOALIASES)
442 return (NULL);
443 /*
444 * forbid hostaliases for setuid binary, due to possible security
445 * breach.
446 */
447 if (issetugid())
448 return (NULL);
449 file = getenv("HOSTALIASES");
450 if (file == NULL || (fp = fopen(file, "re")) == NULL)
451 return (NULL);
452 buf[sizeof(buf) - 1] = '\0';
453 while (fgets(buf, (int)sizeof(buf), fp)) {
454 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
455 ;
456 if (!*cp1)
457 break;
458 *cp1 = '\0';
459 if (ns_samename(buf, name) == 1) {
460 while (isspace((unsigned char)*++cp1))
461 ;
462 if (!*cp1)
463 break;
464 for (cp2 = cp1 + 1; *cp2 &&
465 !isspace((unsigned char)*cp2); ++cp2)
466 ;
467 *cp2 = '\0';
468 strncpy(dst, cp1, siz - 1);
469 dst[siz - 1] = '\0';
470 fclose(fp);
471 return (dst);
472 }
473 }
474 fclose(fp);
475 return (NULL);
476 }
477
478 /*! \file */
479