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 /* Options. Leave them on. */
85 #ifndef DEBUG
86 #define DEBUG
87 #endif
88
89 #if PACKETSZ > 1024
90 #define MAXPACKET PACKETSZ
91 #else
92 #define MAXPACKET 1024
93 #endif
94
95 /*%
96 * Formulate a normal query, send, and await answer.
97 * Returned answer is placed in supplied buffer "answer".
98 * Perform preliminary check of answer, returning success only
99 * if no error is indicated and the answer count is nonzero.
100 * Return the size of the response on success, -1 on error.
101 * Error number is left in H_ERRNO.
102 *
103 * Caller must parse answer and determine whether it answers the question.
104 */
105 int
res_nquery(res_state statp,const char * name,int class,int type,u_char * answer,int anslen)106 res_nquery(res_state statp,
107 const char *name, /*%< domain name */
108 int class, int type, /*%< class and type of query */
109 u_char *answer, /*%< buffer to put answer */
110 int anslen) /*%< size of answer buffer */
111 {
112 u_char buf[MAXPACKET];
113 HEADER *hp = (HEADER *) answer;
114 u_int oflags;
115 u_char *rdata;
116 int n;
117
118 oflags = statp->_flags;
119
120 again:
121 hp->rcode = NOERROR; /*%< default */
122 #ifdef DEBUG
123 if (statp->options & RES_DEBUG)
124 printf(";; res_query(%s, %d, %d)\n", name, class, type);
125 #endif
126
127 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
128 buf, sizeof(buf));
129 #ifdef RES_USE_EDNS0
130 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
131 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
132 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
133 if (n > 0 && (statp->options & RES_NSID) != 0U) {
134 rdata = &buf[n];
135 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
136 NS_OPT_NSID, 0, NULL);
137 }
138 }
139 #endif
140 if (n <= 0) {
141 #ifdef DEBUG
142 if (statp->options & RES_DEBUG)
143 printf(";; res_query: mkquery failed\n");
144 #endif
145 RES_SET_H_ERRNO(statp, NO_RECOVERY);
146 return (n);
147 }
148
149 n = res_nsend(statp, buf, n, answer, anslen);
150 if (n < 0) {
151 #ifdef RES_USE_EDNS0
152 /* if the query choked with EDNS0, retry without EDNS0 */
153 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
154 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
155 statp->_flags |= RES_F_EDNS0ERR;
156 if (statp->options & RES_DEBUG)
157 printf(";; res_nquery: retry without EDNS0\n");
158 goto again;
159 }
160 #endif
161 #ifdef DEBUG
162 if (statp->options & RES_DEBUG)
163 printf(";; res_query: send error\n");
164 #endif
165 RES_SET_H_ERRNO(statp, TRY_AGAIN);
166 return (n);
167 }
168
169 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
170 #ifdef DEBUG
171 if (statp->options & RES_DEBUG)
172 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
173 p_rcode(hp->rcode),
174 ntohs(hp->ancount),
175 ntohs(hp->nscount),
176 ntohs(hp->arcount));
177 #endif
178 switch (hp->rcode) {
179 case NXDOMAIN:
180 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
181 break;
182 case SERVFAIL:
183 RES_SET_H_ERRNO(statp, TRY_AGAIN);
184 break;
185 case NOERROR:
186 RES_SET_H_ERRNO(statp, NO_DATA);
187 break;
188 case FORMERR:
189 case NOTIMP:
190 case REFUSED:
191 default:
192 RES_SET_H_ERRNO(statp, NO_RECOVERY);
193 break;
194 }
195 return (-1);
196 }
197 return (n);
198 }
199
200 /*%
201 * Formulate a normal query, send, and retrieve answer in supplied buffer.
202 * Return the size of the response on success, -1 on error.
203 * If enabled, implement search rules until answer or unrecoverable failure
204 * is detected. Error code, if any, is left in H_ERRNO.
205 */
206 int
res_nsearch(res_state statp,const char * name,int class,int type,u_char * answer,int anslen)207 res_nsearch(res_state statp,
208 const char *name, /*%< domain name */
209 int class, int type, /*%< class and type of query */
210 u_char *answer, /*%< buffer to put answer */
211 int anslen) /*%< size of answer */
212 {
213 const char *cp, * const *domain;
214 HEADER *hp = (HEADER *) answer;
215 char tmp[NS_MAXDNAME];
216 u_int dots;
217 int trailing_dot, ret, saved_herrno;
218 int got_nodata = 0, got_servfail = 0, root_on_list = 0;
219 int tried_as_is = 0;
220 int searched = 0;
221
222 errno = 0;
223 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */
224 dots = 0;
225 for (cp = name; *cp != '\0'; cp++)
226 dots += (*cp == '.');
227 trailing_dot = 0;
228 if (cp > name && *--cp == '.')
229 trailing_dot++;
230
231 /* If there aren't any dots, it could be a user-level alias. */
232 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
233 return (res_nquery(statp, cp, class, type, answer, anslen));
234
235 /*
236 * If there are enough dots in the name, let's just give it a
237 * try 'as is'. The threshold can be set with the "ndots" option.
238 * Also, query 'as is', if there is a trailing dot in the name.
239 */
240 saved_herrno = -1;
241 if (dots >= statp->ndots || trailing_dot) {
242 ret = res_nquerydomain(statp, name, NULL, class, type,
243 answer, anslen);
244 if (ret > 0 || trailing_dot)
245 return (ret);
246 if (errno == ECONNREFUSED) {
247 RES_SET_H_ERRNO(statp, TRY_AGAIN);
248 return (-1);
249 }
250 switch (statp->res_h_errno) {
251 case NO_DATA:
252 case HOST_NOT_FOUND:
253 break;
254 case TRY_AGAIN:
255 if (hp->rcode == SERVFAIL)
256 break;
257 /* FALLTHROUGH */
258 default:
259 return (-1);
260 }
261 saved_herrno = statp->res_h_errno;
262 tried_as_is++;
263 }
264
265 /*
266 * We do at least one level of search if
267 * - there is no dot and RES_DEFNAME is set, or
268 * - there is at least one dot, there is no trailing dot,
269 * and RES_DNSRCH is set.
270 */
271 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
272 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
273 int done = 0;
274
275 for (domain = (const char * const *)statp->dnsrch;
276 *domain && !done;
277 domain++) {
278 searched = 1;
279
280 if (domain[0][0] == '\0' ||
281 (domain[0][0] == '.' && domain[0][1] == '\0'))
282 root_on_list++;
283
284 if (root_on_list && tried_as_is)
285 continue;
286
287 ret = res_nquerydomain(statp, name, *domain,
288 class, type,
289 answer, anslen);
290 if (ret > 0)
291 return (ret);
292
293 /*
294 * If no server present, give up.
295 * If name isn't found in this domain,
296 * keep trying higher domains in the search list
297 * (if that's enabled).
298 * On a NO_DATA error, keep trying, otherwise
299 * a wildcard entry of another type could keep us
300 * from finding this entry higher in the domain.
301 * If we get some other error (negative answer or
302 * server failure), then stop searching up,
303 * but try the input name below in case it's
304 * fully-qualified.
305 */
306 if (errno == ECONNREFUSED) {
307 RES_SET_H_ERRNO(statp, TRY_AGAIN);
308 return (-1);
309 }
310
311 switch (statp->res_h_errno) {
312 case NO_DATA:
313 got_nodata++;
314 /* FALLTHROUGH */
315 case HOST_NOT_FOUND:
316 /* keep trying */
317 break;
318 case TRY_AGAIN:
319 /*
320 * This can occur due to a server failure
321 * (that is, all listed servers have failed),
322 * or all listed servers have timed out.
323 * ((HEADER *)answer)->rcode may not be set
324 * to SERVFAIL in the case of a timeout.
325 *
326 * Either way we must return TRY_AGAIN in
327 * order to avoid non-deterministic
328 * return codes.
329 * For example, loaded name servers or races
330 * against network startup/validation (dhcp,
331 * ppp, etc) can cause the search to timeout
332 * on one search element, e.g. 'fu.bar.com',
333 * and return a definitive failure on the
334 * next search element, e.g. 'fu.'.
335 */
336 got_servfail++;
337 if (hp->rcode == SERVFAIL) {
338 /* try next search element, if any */
339 break;
340 }
341 /* FALLTHROUGH */
342 default:
343 /* anything else implies that we're done */
344 done++;
345 }
346
347 /* if we got here for some reason other than DNSRCH,
348 * we only wanted one iteration of the loop, so stop.
349 */
350 if ((statp->options & RES_DNSRCH) == 0U)
351 done++;
352 }
353 }
354
355 switch (statp->res_h_errno) {
356 case NO_DATA:
357 case HOST_NOT_FOUND:
358 break;
359 case TRY_AGAIN:
360 if (hp->rcode == SERVFAIL)
361 break;
362 /* FALLTHROUGH */
363 default:
364 goto giveup;
365 }
366
367 /*
368 * If the query has not already been tried as is then try it
369 * unless RES_NOTLDQUERY is set and there were no dots.
370 */
371 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
372 !(tried_as_is || root_on_list)) {
373 ret = res_nquerydomain(statp, name, NULL, class, type,
374 answer, anslen);
375 if (ret > 0)
376 return (ret);
377 }
378
379 /* if we got here, we didn't satisfy the search.
380 * if we did an initial full query, return that query's H_ERRNO
381 * (note that we wouldn't be here if that query had succeeded).
382 * else if we ever got a nodata, send that back as the reason.
383 * else send back meaningless H_ERRNO, that being the one from
384 * the last DNSRCH we did.
385 */
386 giveup:
387 if (saved_herrno != -1)
388 RES_SET_H_ERRNO(statp, saved_herrno);
389 else if (got_nodata)
390 RES_SET_H_ERRNO(statp, NO_DATA);
391 else if (got_servfail)
392 RES_SET_H_ERRNO(statp, TRY_AGAIN);
393 return (-1);
394 }
395
396 /*%
397 * Perform a call on res_query on the concatenation of name and domain,
398 * removing a trailing dot from name if domain is NULL.
399 */
400 int
res_nquerydomain(res_state statp,const char * name,const char * domain,int class,int type,u_char * answer,int anslen)401 res_nquerydomain(res_state statp,
402 const char *name,
403 const char *domain,
404 int class, int type, /*%< class and type of query */
405 u_char *answer, /*%< buffer to put answer */
406 int anslen) /*%< size of answer */
407 {
408 char nbuf[MAXDNAME];
409 const char *longname = nbuf;
410 int n, d;
411
412 #ifdef DEBUG
413 if (statp->options & RES_DEBUG)
414 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
415 name, domain?domain:"<Nil>", class, type);
416 #endif
417 if (domain == NULL) {
418 /*
419 * Check for trailing '.';
420 * copy without '.' if present.
421 */
422 n = strlen(name);
423 if (n >= MAXDNAME) {
424 RES_SET_H_ERRNO(statp, NO_RECOVERY);
425 return (-1);
426 }
427 n--;
428 if (n >= 0 && name[n] == '.') {
429 strncpy(nbuf, name, n);
430 nbuf[n] = '\0';
431 } else
432 longname = name;
433 } else {
434 n = strlen(name);
435 d = strlen(domain);
436 if (n + d + 1 >= MAXDNAME) {
437 RES_SET_H_ERRNO(statp, NO_RECOVERY);
438 return (-1);
439 }
440 sprintf(nbuf, "%s.%s", name, domain);
441 }
442 return (res_nquery(statp, longname, class, type, answer, anslen));
443 }
444
445 const char *
res_hostalias(const res_state statp,const char * name,char * dst,size_t siz)446 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
447 char *file, *cp1, *cp2;
448 char buf[BUFSIZ];
449 FILE *fp;
450
451 if (statp->options & RES_NOALIASES)
452 return (NULL);
453 file = secure_getenv("HOSTALIASES");
454 if (file == NULL || (fp = fopen(file, "re")) == NULL)
455 return (NULL);
456 setbuf(fp, NULL);
457 buf[sizeof(buf) - 1] = '\0';
458 while (fgets(buf, sizeof(buf), fp)) {
459 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
460 ;
461 if (!*cp1)
462 break;
463 *cp1 = '\0';
464 if (ns_samename(buf, name) == 1) {
465 while (isspace((unsigned char)*++cp1))
466 ;
467 if (!*cp1)
468 break;
469 for (cp2 = cp1 + 1; *cp2 &&
470 !isspace((unsigned char)*cp2); ++cp2)
471 ;
472 *cp2 = '\0';
473 strncpy(dst, cp1, siz - 1);
474 dst[siz - 1] = '\0';
475 fclose(fp);
476 return (dst);
477 }
478 }
479 fclose(fp);
480 return (NULL);
481 }
482
483 /*! \file */
484