1 /*
2  * Portions Copyright (C) 2004, 2005, 2008  Internet Systems Consortium, Inc. ("ISC")
3  * Portions Copyright (C) 1996-2001, 2003  Internet Software Consortium.
4  *
5  * Permission to use, copy, modify, and/or distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15  * PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 /*
19  * Copyright (c) 1988, 1993
20  *    The Regents of the University of California.  All rights reserved.
21  *
22  * Redistribution and use in source and binary forms, with or without
23  * modification, are permitted provided that the following conditions
24  * are met:
25  * 1. Redistributions of source code must retain the above copyright
26  *    notice, this list of conditions and the following disclaimer.
27  * 2. Redistributions in binary form must reproduce the above copyright
28  *    notice, this list of conditions and the following disclaimer in the
29  *    documentation and/or other materials provided with the distribution.
30  * 3. All advertising materials mentioning features or use of this software
31  *    must display the following acknowledgement:
32  * 	This product includes software developed by the University of
33  * 	California, Berkeley and its contributors.
34  * 4. Neither the name of the University nor the names of its contributors
35  *    may be used to endorse or promote products derived from this software
36  *    without specific prior written permission.
37  *
38  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
39  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
41  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
42  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
43  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
44  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
45  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
46  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
47  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48  * SUCH DAMAGE.
49  */
50 
51 /*
52  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
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, and that
57  * the name of Digital Equipment Corporation not be used in advertising or
58  * publicity pertaining to distribution of the document or software without
59  * specific, written prior permission.
60  *
61  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
62  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
63  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
64  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
65  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
66  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
67  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
68  * SOFTWARE.
69  */
70 
71 #include "port_before.h"
72 #include <sys/types.h>
73 #include <sys/param.h>
74 #include <netinet/in.h>
75 #include <arpa/inet.h>
76 #include <arpa/nameser.h>
77 #include <ctype.h>
78 #include <errno.h>
79 #include <netdb.h>
80 #include <resolv.h>
81 #include <stdio.h>
82 #include <stdlib.h>
83 #include <string.h>
84 #include "port_after.h"
85 
86 /* Options.  Leave them on. */
87 #define DEBUG
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 		rdata = &buf[n];
134 		if (n > 0 && (statp->options & RES_NSID) != 0U) {
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 		saved_herrno = statp->res_h_errno;
247 		tried_as_is++;
248 	}
249 
250 	/*
251 	 * We do at least one level of search if
252 	 *	- there is no dot and RES_DEFNAME is set, or
253 	 *	- there is at least one dot, there is no trailing dot,
254 	 *	  and RES_DNSRCH is set.
255 	 */
256 	if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
257 	    (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
258 		int done = 0;
259 
260 		for (domain = (const char * const *)statp->dnsrch;
261 		     *domain && !done;
262 		     domain++) {
263 			searched = 1;
264 
265 			if (domain[0][0] == '\0' ||
266 			    (domain[0][0] == '.' && domain[0][1] == '\0'))
267 				root_on_list++;
268 
269 			ret = res_nquerydomain(statp, name, *domain,
270 					       class, type,
271 					       answer, anslen);
272 			if (ret > 0)
273 				return (ret);
274 
275 			/*
276 			 * If no server present, give up.
277 			 * If name isn't found in this domain,
278 			 * keep trying higher domains in the search list
279 			 * (if that's enabled).
280 			 * On a NO_DATA error, keep trying, otherwise
281 			 * a wildcard entry of another type could keep us
282 			 * from finding this entry higher in the domain.
283 			 * If we get some other error (negative answer or
284 			 * server failure), then stop searching up,
285 			 * but try the input name below in case it's
286 			 * fully-qualified.
287 			 */
288 			if (errno == ECONNREFUSED) {
289 				RES_SET_H_ERRNO(statp, TRY_AGAIN);
290 				return (-1);
291 			}
292 
293 			switch (statp->res_h_errno) {
294 			case NO_DATA:
295 				got_nodata++;
296 				/* FALLTHROUGH */
297 			case HOST_NOT_FOUND:
298 				/* keep trying */
299 				break;
300 			case TRY_AGAIN:
301 				if (hp->rcode == SERVFAIL) {
302 					/* try next search element, if any */
303 					got_servfail++;
304 					break;
305 				}
306 				/* FALLTHROUGH */
307 			default:
308 				/* anything else implies that we're done */
309 				done++;
310 			}
311 
312 			/* if we got here for some reason other than DNSRCH,
313 			 * we only wanted one iteration of the loop, so stop.
314 			 */
315 			if ((statp->options & RES_DNSRCH) == 0U)
316 				done++;
317 		}
318 	}
319 
320 	/*
321 	 * If the query has not already been tried as is then try it
322 	 * unless RES_NOTLDQUERY is set and there were no dots.
323 	 */
324 	if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
325 	    !(tried_as_is || root_on_list)) {
326 		ret = res_nquerydomain(statp, name, NULL, class, type,
327 				       answer, anslen);
328 		if (ret > 0)
329 			return (ret);
330 	}
331 
332 	/* if we got here, we didn't satisfy the search.
333 	 * if we did an initial full query, return that query's H_ERRNO
334 	 * (note that we wouldn't be here if that query had succeeded).
335 	 * else if we ever got a nodata, send that back as the reason.
336 	 * else send back meaningless H_ERRNO, that being the one from
337 	 * the last DNSRCH we did.
338 	 */
339 	if (saved_herrno != -1)
340 		RES_SET_H_ERRNO(statp, saved_herrno);
341 	else if (got_nodata)
342 		RES_SET_H_ERRNO(statp, NO_DATA);
343 	else if (got_servfail)
344 		RES_SET_H_ERRNO(statp, TRY_AGAIN);
345 	return (-1);
346 }
347 
348 /*%
349  * Perform a call on res_query on the concatenation of name and domain,
350  * removing a trailing dot from name if domain is NULL.
351  */
352 int
res_nquerydomain(res_state statp,const char * name,const char * domain,int class,int type,u_char * answer,int anslen)353 res_nquerydomain(res_state statp,
354 	    const char *name,
355 	    const char *domain,
356 	    int class, int type,	/*%< class and type of query */
357 	    u_char *answer,		/*%< buffer to put answer */
358 	    int anslen)		/*%< size of answer */
359 {
360 	char nbuf[MAXDNAME];
361 	const char *longname = nbuf;
362 	int n, d;
363 
364 #ifdef DEBUG
365 	if (statp->options & RES_DEBUG)
366 		printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
367 		       name, domain?domain:"<Nil>", class, type);
368 #endif
369 	if (domain == NULL) {
370 		/*
371 		 * Check for trailing '.';
372 		 * copy without '.' if present.
373 		 */
374 		n = strlen(name);
375 		if (n >= MAXDNAME) {
376 			RES_SET_H_ERRNO(statp, NO_RECOVERY);
377 			return (-1);
378 		}
379 		n--;
380 		if (n >= 0 && name[n] == '.') {
381 			strncpy(nbuf, name, n);
382 			nbuf[n] = '\0';
383 		} else
384 			longname = name;
385 	} else {
386 		n = strlen(name);
387 		d = strlen(domain);
388 		if (n + d + 1 >= MAXDNAME) {
389 			RES_SET_H_ERRNO(statp, NO_RECOVERY);
390 			return (-1);
391 		}
392 		sprintf(nbuf, "%s.%s", name, domain);
393 	}
394 	return (res_nquery(statp, longname, class, type, answer, anslen));
395 }
396 
397 const char *
res_hostalias(const res_state statp,const char * name,char * dst,size_t siz)398 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
399 	char *file, *cp1, *cp2;
400 	char buf[BUFSIZ];
401 	FILE *fp;
402 
403 	if (statp->options & RES_NOALIASES)
404 		return (NULL);
405 	file = getenv("HOSTALIASES");
406 	if (file == NULL || (fp = fopen(file, "r")) == NULL)
407 		return (NULL);
408 	setbuf(fp, NULL);
409 	buf[sizeof(buf) - 1] = '\0';
410 	while (fgets(buf, sizeof(buf), fp)) {
411 		for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
412 			;
413 		if (!*cp1)
414 			break;
415 		*cp1 = '\0';
416 		if (ns_samename(buf, name) == 1) {
417 			while (isspace((unsigned char)*++cp1))
418 				;
419 			if (!*cp1)
420 				break;
421 			for (cp2 = cp1 + 1; *cp2 &&
422 			     !isspace((unsigned char)*cp2); ++cp2)
423 				;
424 			*cp2 = '\0';
425 			strncpy(dst, cp1, siz - 1);
426 			dst[siz - 1] = '\0';
427 			fclose(fp);
428 			return (dst);
429 		}
430 	}
431 	fclose(fp);
432 	return (NULL);
433 }
434 
435 /*! \file */
436