xref: /freebsd/lib/libc/resolv/res_query.c (revision 87c1627502a5dde91e5284118eec8682b60f27a2)
1 /*
2  * Copyright (c) 1988, 1993
3  *    The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 4. Neither the name of the University nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 /*
31  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
32  *
33  * Permission to use, copy, modify, and distribute this software for any
34  * purpose with or without fee is hereby granted, provided that the above
35  * copyright notice and this permission notice appear in all copies, and that
36  * the name of Digital Equipment Corporation not be used in advertising or
37  * publicity pertaining to distribution of the document or software without
38  * specific, written prior permission.
39  *
40  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
41  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
42  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
43  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
44  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
45  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
46  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
47  * SOFTWARE.
48  */
49 
50 /*
51  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
52  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
53  *
54  * Permission to use, copy, modify, and distribute this software for any
55  * purpose with or without fee is hereby granted, provided that the above
56  * copyright notice and this permission notice appear in all copies.
57  *
58  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
59  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
60  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
61  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
62  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
63  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
64  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
65  */
66 
67 #if defined(LIBC_SCCS) && !defined(lint)
68 static const char sccsid[] = "@(#)res_query.c	8.1 (Berkeley) 6/4/93";
69 static const char rcsid[] = "$Id: res_query.c,v 1.7.18.2 2008/04/03 23:15:15 marka Exp $";
70 #endif /* LIBC_SCCS and not lint */
71 #include <sys/cdefs.h>
72 __FBSDID("$FreeBSD$");
73 
74 #include "port_before.h"
75 #include <sys/types.h>
76 #include <sys/param.h>
77 #include <netinet/in.h>
78 #include <arpa/inet.h>
79 #include <arpa/nameser.h>
80 #include <ctype.h>
81 #include <errno.h>
82 #include <netdb.h>
83 #include <resolv.h>
84 #include <stdio.h>
85 #include <stdlib.h>
86 #include <string.h>
87 #include <unistd.h>
88 #include "port_after.h"
89 
90 /* Options.  Leave them on. */
91 #define DEBUG
92 
93 #if PACKETSZ > 1024
94 #define MAXPACKET	PACKETSZ
95 #else
96 #define MAXPACKET	1024
97 #endif
98 
99 /*%
100  * Formulate a normal query, send, and await answer.
101  * Returned answer is placed in supplied buffer "answer".
102  * Perform preliminary check of answer, returning success only
103  * if no error is indicated and the answer count is nonzero.
104  * Return the size of the response on success, -1 on error.
105  * Error number is left in H_ERRNO.
106  *
107  * Caller must parse answer and determine whether it answers the question.
108  */
109 int
110 res_nquery(res_state statp,
111 	   const char *name,	/*%< domain name */
112 	   int class, int type,	/*%< class and type of query */
113 	   u_char *answer,	/*%< buffer to put answer */
114 	   int anslen)		/*%< size of answer buffer */
115 {
116 	u_char buf[MAXPACKET];
117 	HEADER *hp = (HEADER *) answer;
118 	u_int oflags;
119 	u_char *rdata;
120 	int n;
121 
122 	oflags = statp->_flags;
123 
124 again:
125 	hp->rcode = NOERROR;	/*%< default */
126 #ifdef DEBUG
127 	if (statp->options & RES_DEBUG)
128 		printf(";; res_query(%s, %d, %d)\n", name, class, type);
129 #endif
130 
131 	n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
132 			 buf, sizeof(buf));
133 #ifdef RES_USE_EDNS0
134 	if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
135 	    (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
136 		n = res_nopt(statp, n, buf, sizeof(buf), anslen);
137 		rdata = &buf[n];
138 		if (n > 0 && (statp->options & RES_NSID) != 0U) {
139 			n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
140 					   NS_OPT_NSID, 0, NULL);
141 		}
142 	}
143 #endif
144 	if (n <= 0) {
145 #ifdef DEBUG
146 		if (statp->options & RES_DEBUG)
147 			printf(";; res_query: mkquery failed\n");
148 #endif
149 		RES_SET_H_ERRNO(statp, NO_RECOVERY);
150 		return (n);
151 	}
152 
153 	n = res_nsend(statp, buf, n, answer, anslen);
154 	if (n < 0) {
155 #ifdef RES_USE_EDNS0
156 		/* if the query choked with EDNS0, retry without EDNS0 */
157 		if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
158 		    ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
159 			statp->_flags |= RES_F_EDNS0ERR;
160 			if (statp->options & RES_DEBUG)
161 				printf(";; res_nquery: retry without EDNS0\n");
162 			goto again;
163 		}
164 #endif
165 #ifdef DEBUG
166 		if (statp->options & RES_DEBUG)
167 			printf(";; res_query: send error\n");
168 #endif
169 		RES_SET_H_ERRNO(statp, TRY_AGAIN);
170 		return (n);
171 	}
172 
173 	if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
174 #ifdef DEBUG
175 		if (statp->options & RES_DEBUG)
176 			printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
177 			       p_rcode(hp->rcode),
178 			       ntohs(hp->ancount),
179 			       ntohs(hp->nscount),
180 			       ntohs(hp->arcount));
181 #endif
182 		switch (hp->rcode) {
183 		case NXDOMAIN:
184 			RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
185 			break;
186 		case SERVFAIL:
187 			RES_SET_H_ERRNO(statp, TRY_AGAIN);
188 			break;
189 		case NOERROR:
190 			RES_SET_H_ERRNO(statp, NO_DATA);
191 			break;
192 		case FORMERR:
193 		case NOTIMP:
194 		case REFUSED:
195 		default:
196 			RES_SET_H_ERRNO(statp, NO_RECOVERY);
197 			break;
198 		}
199 		return (-1);
200 	}
201 	return (n);
202 }
203 
204 /*%
205  * Formulate a normal query, send, and retrieve answer in supplied buffer.
206  * Return the size of the response on success, -1 on error.
207  * If enabled, implement search rules until answer or unrecoverable failure
208  * is detected.  Error code, if any, is left in H_ERRNO.
209  */
210 int
211 res_nsearch(res_state statp,
212 	    const char *name,	/*%< domain name */
213 	    int class, int type,	/*%< class and type of query */
214 	    u_char *answer,	/*%< buffer to put answer */
215 	    int anslen)		/*%< size of answer */
216 {
217 	const char *cp, * const *domain;
218 	HEADER *hp = (HEADER *) answer;
219 	char tmp[NS_MAXDNAME];
220 	u_int dots;
221 	int trailing_dot, ret, saved_herrno;
222 	int got_nodata = 0, got_servfail = 0, root_on_list = 0;
223 	int tried_as_is = 0;
224 	int searched = 0;
225 
226 	errno = 0;
227 	RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /*%< True if we never query. */
228 	dots = 0;
229 	for (cp = name; *cp != '\0'; cp++)
230 		dots += (*cp == '.');
231 	trailing_dot = 0;
232 	if (cp > name && *--cp == '.')
233 		trailing_dot++;
234 
235 	/* If there aren't any dots, it could be a user-level alias. */
236 	if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
237 		return (res_nquery(statp, cp, class, type, answer, anslen));
238 
239 	/*
240 	 * If there are enough dots in the name, let's just give it a
241 	 * try 'as is'. The threshold can be set with the "ndots" option.
242 	 * Also, query 'as is', if there is a trailing dot in the name.
243 	 */
244 	saved_herrno = -1;
245 	if (dots >= statp->ndots || trailing_dot) {
246 		ret = res_nquerydomain(statp, name, NULL, class, type,
247 					 answer, anslen);
248 		if (ret > 0 || trailing_dot)
249 			return (ret);
250 		if (errno == ECONNREFUSED) {
251 			RES_SET_H_ERRNO(statp, TRY_AGAIN);
252 			return (-1);
253 		}
254 		switch (statp->res_h_errno) {
255 		case NO_DATA:
256 		case HOST_NOT_FOUND:
257 			break;
258 		case TRY_AGAIN:
259 			if (hp->rcode == SERVFAIL)
260 				break;
261 			/* FALLTHROUGH */
262 		default:
263 			return (-1);
264 		}
265 		saved_herrno = statp->res_h_errno;
266 		tried_as_is++;
267 	}
268 
269 	/*
270 	 * We do at least one level of search if
271 	 *	- there is no dot and RES_DEFNAME is set, or
272 	 *	- there is at least one dot, there is no trailing dot,
273 	 *	  and RES_DNSRCH is set.
274 	 */
275 	if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
276 	    (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
277 		int done = 0;
278 
279 		for (domain = (const char * const *)statp->dnsrch;
280 		     *domain && !done;
281 		     domain++) {
282 			searched = 1;
283 
284 			if (domain[0][0] == '\0' ||
285 			    (domain[0][0] == '.' && domain[0][1] == '\0'))
286 				root_on_list++;
287 
288 			if (root_on_list && tried_as_is)
289 				continue;
290 
291 			ret = res_nquerydomain(statp, name, *domain,
292 					       class, type,
293 					       answer, anslen);
294 			if (ret > 0)
295 				return (ret);
296 
297 			/*
298 			 * If no server present, give up.
299 			 * If name isn't found in this domain,
300 			 * keep trying higher domains in the search list
301 			 * (if that's enabled).
302 			 * On a NO_DATA error, keep trying, otherwise
303 			 * a wildcard entry of another type could keep us
304 			 * from finding this entry higher in the domain.
305 			 * If we get some other error (negative answer or
306 			 * server failure), then stop searching up,
307 			 * but try the input name below in case it's
308 			 * fully-qualified.
309 			 */
310 			if (errno == ECONNREFUSED) {
311 				RES_SET_H_ERRNO(statp, TRY_AGAIN);
312 				return (-1);
313 			}
314 
315 			switch (statp->res_h_errno) {
316 			case NO_DATA:
317 				got_nodata++;
318 				/* FALLTHROUGH */
319 			case HOST_NOT_FOUND:
320 				/* keep trying */
321 				break;
322 			case TRY_AGAIN:
323 				/*
324 				 * This can occur due to a server failure
325 				 * (that is, all listed servers have failed),
326 				 * or all listed servers have timed out.
327 				 * ((HEADER *)answer)->rcode may not be set
328 				 * to SERVFAIL in the case of a timeout.
329 				 *
330 				 * Either way we must return TRY_AGAIN in
331 				 * order to avoid non-deterministic
332 				 * return codes.
333 				 * For example, loaded name servers or races
334 				 * against network startup/validation (dhcp,
335 				 * ppp, etc) can cause the search to timeout
336 				 * on one search element, e.g. 'fu.bar.com',
337 				 * and return a definitive failure on the
338 				 * next search element, e.g. 'fu.'.
339 				 */
340 				got_servfail++;
341 				if (hp->rcode == SERVFAIL) {
342 					/* try next search element, if any */
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 	switch (statp->res_h_errno) {
360 	case NO_DATA:
361 	case HOST_NOT_FOUND:
362 		break;
363 	case TRY_AGAIN:
364 		if (hp->rcode == SERVFAIL)
365 			break;
366 		/* FALLTHROUGH */
367 	default:
368 		goto giveup;
369 	}
370 
371 	/*
372 	 * If the query has not already been tried as is then try it
373 	 * unless RES_NOTLDQUERY is set and there were no dots.
374 	 */
375 	if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
376 	    !(tried_as_is || root_on_list)) {
377 		ret = res_nquerydomain(statp, name, NULL, class, type,
378 				       answer, anslen);
379 		if (ret > 0)
380 			return (ret);
381 	}
382 
383 	/* if we got here, we didn't satisfy the search.
384 	 * if we did an initial full query, return that query's H_ERRNO
385 	 * (note that we wouldn't be here if that query had succeeded).
386 	 * else if we ever got a nodata, send that back as the reason.
387 	 * else send back meaningless H_ERRNO, that being the one from
388 	 * the last DNSRCH we did.
389 	 */
390 giveup:
391 	if (saved_herrno != -1)
392 		RES_SET_H_ERRNO(statp, saved_herrno);
393 	else if (got_nodata)
394 		RES_SET_H_ERRNO(statp, NO_DATA);
395 	else if (got_servfail)
396 		RES_SET_H_ERRNO(statp, TRY_AGAIN);
397 	return (-1);
398 }
399 
400 /*%
401  * Perform a call on res_query on the concatenation of name and domain,
402  * removing a trailing dot from name if domain is NULL.
403  */
404 int
405 res_nquerydomain(res_state statp,
406 	    const char *name,
407 	    const char *domain,
408 	    int class, int type,	/*%< class and type of query */
409 	    u_char *answer,		/*%< buffer to put answer */
410 	    int anslen)		/*%< size of answer */
411 {
412 	char nbuf[MAXDNAME];
413 	const char *longname = nbuf;
414 	int n, d;
415 
416 #ifdef DEBUG
417 	if (statp->options & RES_DEBUG)
418 		printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
419 		       name, domain?domain:"<Nil>", class, type);
420 #endif
421 	if (domain == NULL) {
422 		/*
423 		 * Check for trailing '.';
424 		 * copy without '.' if present.
425 		 */
426 		n = strlen(name);
427 		if (n >= MAXDNAME) {
428 			RES_SET_H_ERRNO(statp, NO_RECOVERY);
429 			return (-1);
430 		}
431 		n--;
432 		if (n >= 0 && name[n] == '.') {
433 			strncpy(nbuf, name, n);
434 			nbuf[n] = '\0';
435 		} else
436 			longname = name;
437 	} else {
438 		n = strlen(name);
439 		d = strlen(domain);
440 		if (n + d + 1 >= MAXDNAME) {
441 			RES_SET_H_ERRNO(statp, NO_RECOVERY);
442 			return (-1);
443 		}
444 		sprintf(nbuf, "%s.%s", name, domain);
445 	}
446 	return (res_nquery(statp, longname, class, type, answer, anslen));
447 }
448 
449 const char *
450 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
451 	char *file, *cp1, *cp2;
452 	char buf[BUFSIZ];
453 	FILE *fp;
454 
455 	if (statp->options & RES_NOALIASES)
456 		return (NULL);
457 	if (issetugid())
458 		return (NULL);
459 	file = getenv("HOSTALIASES");
460 	if (file == NULL || (fp = fopen(file, "r")) == NULL)
461 		return (NULL);
462 	setbuf(fp, NULL);
463 	buf[sizeof(buf) - 1] = '\0';
464 	while (fgets(buf, sizeof(buf), fp)) {
465 		for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
466 			;
467 		if (!*cp1)
468 			break;
469 		*cp1 = '\0';
470 		if (ns_samename(buf, name) == 1) {
471 			while (isspace((unsigned char)*++cp1))
472 				;
473 			if (!*cp1)
474 				break;
475 			for (cp2 = cp1 + 1; *cp2 &&
476 			     !isspace((unsigned char)*cp2); ++cp2)
477 				;
478 			*cp2 = '\0';
479 			strncpy(dst, cp1, siz - 1);
480 			dst[siz - 1] = '\0';
481 			fclose(fp);
482 			return (dst);
483 		}
484 	}
485 	fclose(fp);
486 	return (NULL);
487 }
488 
489 /*! \file */
490