1 /*-
2 * SPDX-License-Identifier: (ISC AND BSD-3-Clause)
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 #include "port_before.h"
70 #include <sys/param.h>
71 #include <netinet/in.h>
72 #include <arpa/inet.h>
73 #include <arpa/nameser.h>
74 #include <ctype.h>
75 #include <errno.h>
76 #include <netdb.h>
77 #include <resolv.h>
78 #include <stdio.h>
79 #include <stdlib.h>
80 #include <string.h>
81 #include <unistd.h>
82 #include "port_after.h"
83
84 #if PACKETSZ > 1024
85 #define MAXPACKET PACKETSZ
86 #else
87 #define MAXPACKET 1024
88 #endif
89
90 /*%
91 * Formulate a normal query, send, and await answer.
92 * Returned answer is placed in supplied buffer "answer".
93 * Perform preliminary check of answer, returning success only
94 * if no error is indicated and the answer count is nonzero.
95 * Return the size of the response on success, -1 on error.
96 * Error number is left in H_ERRNO.
97 *
98 * Caller must parse answer and determine whether it answers the question.
99 */
100 int
res_nquery(res_state statp,const char * name,int class,int type,u_char * answer,int anslen)101 res_nquery(res_state statp,
102 const char *name, /*%< domain name */
103 int class, int type, /*%< class and type of query */
104 u_char *answer, /*%< buffer to put answer */
105 int anslen) /*%< size of answer buffer */
106 {
107 u_char buf[MAXPACKET];
108 HEADER *hp = (HEADER *) answer;
109 u_int oflags;
110 u_char *rdata;
111 int n;
112
113 oflags = statp->_flags;
114
115 again:
116 hp->rcode = NOERROR; /*%< default */
117 #ifdef DEBUG
118 if (statp->options & RES_DEBUG)
119 printf(";; res_query(%s, %d, %d)\n", name, class, type);
120 #endif
121
122 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
123 buf, sizeof(buf));
124 #ifdef RES_USE_EDNS0
125 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
126 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
127 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
128 if (n > 0 && (statp->options & RES_NSID) != 0U) {
129 rdata = &buf[n];
130 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
131 NS_OPT_NSID, 0, NULL);
132 }
133 }
134 #endif
135 if (n <= 0) {
136 #ifdef DEBUG
137 if (statp->options & RES_DEBUG)
138 printf(";; res_query: mkquery failed\n");
139 #endif
140 RES_SET_H_ERRNO(statp, NO_RECOVERY);
141 return (n);
142 }
143
144 n = res_nsend(statp, buf, n, answer, anslen);
145 if (n < 0) {
146 #ifdef RES_USE_EDNS0
147 /* if the query choked with EDNS0, retry without EDNS0 */
148 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
149 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
150 statp->_flags |= RES_F_EDNS0ERR;
151 if (statp->options & RES_DEBUG)
152 printf(";; res_nquery: retry without EDNS0\n");
153 goto again;
154 }
155 #endif
156 #ifdef DEBUG
157 if (statp->options & RES_DEBUG)
158 printf(";; res_query: send error\n");
159 #endif
160 RES_SET_H_ERRNO(statp, TRY_AGAIN);
161 return (n);
162 }
163
164 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
165 #ifdef DEBUG
166 if (statp->options & RES_DEBUG)
167 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
168 p_rcode(hp->rcode),
169 ntohs(hp->ancount),
170 ntohs(hp->nscount),
171 ntohs(hp->arcount));
172 #endif
173 switch (hp->rcode) {
174 case NXDOMAIN:
175 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
176 break;
177 case SERVFAIL:
178 RES_SET_H_ERRNO(statp, TRY_AGAIN);
179 break;
180 case NOERROR:
181 RES_SET_H_ERRNO(statp, NO_DATA);
182 break;
183 case FORMERR:
184 case NOTIMP:
185 case REFUSED:
186 default:
187 RES_SET_H_ERRNO(statp, NO_RECOVERY);
188 break;
189 }
190 return (-1);
191 }
192 return (n);
193 }
194
195 /*%
196 * Formulate a normal query, send, and retrieve answer in supplied buffer.
197 * Return the size of the response on success, -1 on error.
198 * If enabled, implement search rules until answer or unrecoverable failure
199 * is detected. Error code, if any, is left in H_ERRNO.
200 */
201 int
res_nsearch(res_state statp,const char * name,int class,int type,u_char * answer,int anslen)202 res_nsearch(res_state statp,
203 const char *name, /*%< domain name */
204 int class, int type, /*%< class and type of query */
205 u_char *answer, /*%< buffer to put answer */
206 int anslen) /*%< size of answer */
207 {
208 const char *cp, * const *domain;
209 HEADER *hp = (HEADER *) answer;
210 char tmp[NS_MAXDNAME];
211 u_int dots;
212 int trailing_dot, ret, saved_herrno;
213 int got_nodata = 0, got_servfail = 0, root_on_list = 0;
214 int tried_as_is = 0;
215 int searched = 0;
216
217 errno = 0;
218 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */
219 dots = 0;
220 for (cp = name; *cp != '\0'; cp++)
221 dots += (*cp == '.');
222 trailing_dot = 0;
223 if (cp > name && *--cp == '.')
224 trailing_dot++;
225
226 /* If there aren't any dots, it could be a user-level alias. */
227 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
228 return (res_nquery(statp, cp, class, type, answer, anslen));
229
230 /*
231 * If there are enough dots in the name, let's just give it a
232 * try 'as is'. The threshold can be set with the "ndots" option.
233 * Also, query 'as is', if there is a trailing dot in the name.
234 */
235 saved_herrno = -1;
236 if (dots >= statp->ndots || trailing_dot) {
237 ret = res_nquerydomain(statp, name, NULL, class, type,
238 answer, anslen);
239 if (ret > 0 || trailing_dot)
240 return (ret);
241 if (errno == ECONNREFUSED) {
242 RES_SET_H_ERRNO(statp, TRY_AGAIN);
243 return (-1);
244 }
245 switch (statp->res_h_errno) {
246 case NO_DATA:
247 case HOST_NOT_FOUND:
248 break;
249 case TRY_AGAIN:
250 if (hp->rcode == SERVFAIL)
251 break;
252 /* FALLTHROUGH */
253 default:
254 return (-1);
255 }
256 saved_herrno = statp->res_h_errno;
257 tried_as_is++;
258 }
259
260 /*
261 * We do at least one level of search if
262 * - there is no dot and RES_DEFNAME is set, or
263 * - there is at least one dot, there is no trailing dot,
264 * and RES_DNSRCH is set.
265 */
266 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
267 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
268 int done = 0;
269
270 for (domain = (const char * const *)statp->dnsrch;
271 *domain && !done;
272 domain++) {
273 searched = 1;
274
275 if (domain[0][0] == '\0' ||
276 (domain[0][0] == '.' && domain[0][1] == '\0'))
277 root_on_list++;
278
279 if (root_on_list && tried_as_is)
280 continue;
281
282 ret = res_nquerydomain(statp, name, *domain,
283 class, type,
284 answer, anslen);
285 if (ret > 0)
286 return (ret);
287
288 /*
289 * If no server present, give up.
290 * If name isn't found in this domain,
291 * keep trying higher domains in the search list
292 * (if that's enabled).
293 * On a NO_DATA error, keep trying, otherwise
294 * a wildcard entry of another type could keep us
295 * from finding this entry higher in the domain.
296 * If we get some other error (negative answer or
297 * server failure), then stop searching up,
298 * but try the input name below in case it's
299 * fully-qualified.
300 */
301 if (errno == ECONNREFUSED) {
302 RES_SET_H_ERRNO(statp, TRY_AGAIN);
303 return (-1);
304 }
305
306 switch (statp->res_h_errno) {
307 case NO_DATA:
308 got_nodata++;
309 /* FALLTHROUGH */
310 case HOST_NOT_FOUND:
311 /* keep trying */
312 break;
313 case TRY_AGAIN:
314 /*
315 * This can occur due to a server failure
316 * (that is, all listed servers have failed),
317 * or all listed servers have timed out.
318 * ((HEADER *)answer)->rcode may not be set
319 * to SERVFAIL in the case of a timeout.
320 *
321 * Either way we must return TRY_AGAIN in
322 * order to avoid non-deterministic
323 * return codes.
324 * For example, loaded name servers or races
325 * against network startup/validation (dhcp,
326 * ppp, etc) can cause the search to timeout
327 * on one search element, e.g. 'fu.bar.com',
328 * and return a definitive failure on the
329 * next search element, e.g. 'fu.'.
330 */
331 got_servfail++;
332 if (hp->rcode == SERVFAIL) {
333 /* try next search element, if any */
334 break;
335 }
336 /* FALLTHROUGH */
337 default:
338 /* anything else implies that we're done */
339 done++;
340 }
341
342 /* if we got here for some reason other than DNSRCH,
343 * we only wanted one iteration of the loop, so stop.
344 */
345 if ((statp->options & RES_DNSRCH) == 0U)
346 done++;
347 }
348 }
349
350 switch (statp->res_h_errno) {
351 case NO_DATA:
352 case HOST_NOT_FOUND:
353 break;
354 case TRY_AGAIN:
355 if (hp->rcode == SERVFAIL)
356 break;
357 /* FALLTHROUGH */
358 default:
359 goto giveup;
360 }
361
362 /*
363 * If the query has not already been tried as is then try it
364 * unless RES_NOTLDQUERY is set and there were no dots.
365 */
366 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
367 !(tried_as_is || root_on_list)) {
368 ret = res_nquerydomain(statp, name, NULL, class, type,
369 answer, anslen);
370 if (ret > 0)
371 return (ret);
372 }
373
374 /* if we got here, we didn't satisfy the search.
375 * if we did an initial full query, return that query's H_ERRNO
376 * (note that we wouldn't be here if that query had succeeded).
377 * else if we ever got a nodata, send that back as the reason.
378 * else send back meaningless H_ERRNO, that being the one from
379 * the last DNSRCH we did.
380 */
381 giveup:
382 if (saved_herrno != -1)
383 RES_SET_H_ERRNO(statp, saved_herrno);
384 else if (got_nodata)
385 RES_SET_H_ERRNO(statp, NO_DATA);
386 else if (got_servfail)
387 RES_SET_H_ERRNO(statp, TRY_AGAIN);
388 return (-1);
389 }
390
391 /*%
392 * Perform a call on res_query on the concatenation of name and domain,
393 * removing a trailing dot from name if domain is NULL.
394 */
395 int
res_nquerydomain(res_state statp,const char * name,const char * domain,int class,int type,u_char * answer,int anslen)396 res_nquerydomain(res_state statp,
397 const char *name,
398 const char *domain,
399 int class, int type, /*%< class and type of query */
400 u_char *answer, /*%< buffer to put answer */
401 int anslen) /*%< size of answer */
402 {
403 char nbuf[MAXDNAME];
404 const char *longname = nbuf;
405 int n, d;
406
407 #ifdef DEBUG
408 if (statp->options & RES_DEBUG)
409 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
410 name, domain?domain:"<Nil>", class, type);
411 #endif
412 if (domain == NULL) {
413 /*
414 * Check for trailing '.';
415 * copy without '.' if present.
416 */
417 n = strlen(name);
418 if (n >= MAXDNAME) {
419 RES_SET_H_ERRNO(statp, NO_RECOVERY);
420 return (-1);
421 }
422 n--;
423 if (n >= 0 && name[n] == '.') {
424 strncpy(nbuf, name, n);
425 nbuf[n] = '\0';
426 } else
427 longname = name;
428 } else {
429 n = strlen(name);
430 d = strlen(domain);
431 if (n + d + 1 >= MAXDNAME) {
432 RES_SET_H_ERRNO(statp, NO_RECOVERY);
433 return (-1);
434 }
435 sprintf(nbuf, "%s.%s", name, domain);
436 }
437 return (res_nquery(statp, longname, class, type, answer, anslen));
438 }
439
440 const char *
res_hostalias(const res_state statp,const char * name,char * dst,size_t siz)441 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
442 char *file, *cp1, *cp2;
443 char buf[BUFSIZ];
444 FILE *fp;
445
446 if (statp->options & RES_NOALIASES)
447 return (NULL);
448 file = secure_getenv("HOSTALIASES");
449 if (file == NULL || (fp = fopen(file, "re")) == NULL)
450 return (NULL);
451 setbuf(fp, NULL);
452 buf[sizeof(buf) - 1] = '\0';
453 while (fgets(buf, 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