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 1.7.18.1 2005/04/27 05:01:11 sra 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 int n; 119 u_int oflags; 120 121 oflags = statp->_flags; 122 123 again: 124 hp->rcode = NOERROR; /*%< default */ 125 #ifdef DEBUG 126 if (statp->options & RES_DEBUG) 127 printf(";; res_query(%s, %d, %d)\n", name, class, type); 128 #endif 129 130 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 131 buf, sizeof(buf)); 132 #ifdef RES_USE_EDNS0 133 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 134 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U) 135 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 136 #endif 137 if (n <= 0) { 138 #ifdef DEBUG 139 if (statp->options & RES_DEBUG) 140 printf(";; res_query: mkquery failed\n"); 141 #endif 142 RES_SET_H_ERRNO(statp, NO_RECOVERY); 143 return (n); 144 } 145 n = res_nsend(statp, buf, n, answer, anslen); 146 if (n < 0) { 147 #ifdef RES_USE_EDNS0 148 /* if the query choked with EDNS0, retry without EDNS0 */ 149 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 150 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 151 statp->_flags |= RES_F_EDNS0ERR; 152 if (statp->options & RES_DEBUG) 153 printf(";; res_nquery: retry without EDNS0\n"); 154 goto again; 155 } 156 #endif 157 #ifdef DEBUG 158 if (statp->options & RES_DEBUG) 159 printf(";; res_query: send error\n"); 160 #endif 161 RES_SET_H_ERRNO(statp, TRY_AGAIN); 162 return (n); 163 } 164 165 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 166 #ifdef DEBUG 167 if (statp->options & RES_DEBUG) 168 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 169 p_rcode(hp->rcode), 170 ntohs(hp->ancount), 171 ntohs(hp->nscount), 172 ntohs(hp->arcount)); 173 #endif 174 switch (hp->rcode) { 175 case NXDOMAIN: 176 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 177 break; 178 case SERVFAIL: 179 RES_SET_H_ERRNO(statp, TRY_AGAIN); 180 break; 181 case NOERROR: 182 RES_SET_H_ERRNO(statp, NO_DATA); 183 break; 184 case FORMERR: 185 case NOTIMP: 186 case REFUSED: 187 default: 188 RES_SET_H_ERRNO(statp, NO_RECOVERY); 189 break; 190 } 191 return (-1); 192 } 193 return (n); 194 } 195 196 /*% 197 * Formulate a normal query, send, and retrieve answer in supplied buffer. 198 * Return the size of the response on success, -1 on error. 199 * If enabled, implement search rules until answer or unrecoverable failure 200 * is detected. Error code, if any, is left in H_ERRNO. 201 */ 202 int 203 res_nsearch(res_state statp, 204 const char *name, /*%< domain name */ 205 int class, int type, /*%< class and type of query */ 206 u_char *answer, /*%< buffer to put answer */ 207 int anslen) /*%< size of answer */ 208 { 209 const char *cp, * const *domain; 210 HEADER *hp = (HEADER *) answer; 211 char tmp[NS_MAXDNAME]; 212 u_int dots; 213 int trailing_dot, ret, saved_herrno; 214 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 215 int tried_as_is = 0; 216 int searched = 0; 217 218 errno = 0; 219 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 220 dots = 0; 221 for (cp = name; *cp != '\0'; cp++) 222 dots += (*cp == '.'); 223 trailing_dot = 0; 224 if (cp > name && *--cp == '.') 225 trailing_dot++; 226 227 /* If there aren't any dots, it could be a user-level alias. */ 228 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 229 return (res_nquery(statp, cp, class, type, answer, anslen)); 230 231 /* 232 * If there are enough dots in the name, let's just give it a 233 * try 'as is'. The threshold can be set with the "ndots" option. 234 * Also, query 'as is', if there is a trailing dot in the name. 235 */ 236 saved_herrno = -1; 237 if (dots >= statp->ndots || trailing_dot) { 238 ret = res_nquerydomain(statp, name, NULL, class, type, 239 answer, anslen); 240 if (ret > 0 || trailing_dot) 241 return (ret); 242 if (errno == ECONNREFUSED) { 243 RES_SET_H_ERRNO(statp, TRY_AGAIN); 244 return (-1); 245 } 246 switch (statp->res_h_errno) { 247 case NO_DATA: 248 case HOST_NOT_FOUND: 249 break; 250 case TRY_AGAIN: 251 if (hp->rcode == SERVFAIL) 252 break; 253 /* FALLTHROUGH */ 254 default: 255 return (-1); 256 } 257 saved_herrno = statp->res_h_errno; 258 tried_as_is++; 259 } 260 261 /* 262 * We do at least one level of search if 263 * - there is no dot and RES_DEFNAME is set, or 264 * - there is at least one dot, there is no trailing dot, 265 * and RES_DNSRCH is set. 266 */ 267 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 268 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 269 int done = 0; 270 271 for (domain = (const char * const *)statp->dnsrch; 272 *domain && !done; 273 domain++) { 274 searched = 1; 275 276 if (domain[0][0] == '\0' || 277 (domain[0][0] == '.' && domain[0][1] == '\0')) 278 root_on_list++; 279 280 if (root_on_list && tried_as_is) 281 continue; 282 283 ret = res_nquerydomain(statp, name, *domain, 284 class, type, 285 answer, anslen); 286 if (ret > 0) 287 return (ret); 288 289 /* 290 * If no server present, give up. 291 * If name isn't found in this domain, 292 * keep trying higher domains in the search list 293 * (if that's enabled). 294 * On a NO_DATA error, keep trying, otherwise 295 * a wildcard entry of another type could keep us 296 * from finding this entry higher in the domain. 297 * If we get some other error (negative answer or 298 * server failure), then stop searching up, 299 * but try the input name below in case it's 300 * fully-qualified. 301 */ 302 if (errno == ECONNREFUSED) { 303 RES_SET_H_ERRNO(statp, TRY_AGAIN); 304 return (-1); 305 } 306 307 switch (statp->res_h_errno) { 308 case NO_DATA: 309 got_nodata++; 310 /* FALLTHROUGH */ 311 case HOST_NOT_FOUND: 312 /* keep trying */ 313 break; 314 case TRY_AGAIN: 315 /* 316 * This can occur due to a server failure 317 * (that is, all listed servers have failed), 318 * or all listed servers have timed out. 319 * ((HEADER *)answer)->rcode may not be set 320 * to SERVFAIL in the case of a timeout. 321 * 322 * Either way we must return TRY_AGAIN in 323 * order to avoid non-deterministic 324 * return codes. 325 * For example, loaded name servers or races 326 * against network startup/validation (dhcp, 327 * ppp, etc) can cause the search to timeout 328 * on one search element, e.g. 'fu.bar.com', 329 * and return a definitive failure on the 330 * next search element, e.g. 'fu.'. 331 */ 332 got_servfail++; 333 if (hp->rcode == SERVFAIL) { 334 /* try next search element, if any */ 335 break; 336 } 337 /* FALLTHROUGH */ 338 default: 339 /* anything else implies that we're done */ 340 done++; 341 } 342 343 /* if we got here for some reason other than DNSRCH, 344 * we only wanted one iteration of the loop, so stop. 345 */ 346 if ((statp->options & RES_DNSRCH) == 0U) 347 done++; 348 } 349 } 350 351 switch (statp->res_h_errno) { 352 case NO_DATA: 353 case HOST_NOT_FOUND: 354 break; 355 case TRY_AGAIN: 356 if (hp->rcode == SERVFAIL) 357 break; 358 /* FALLTHROUGH */ 359 default: 360 goto giveup; 361 } 362 363 /* 364 * If the query has not already been tried as is then try it 365 * unless RES_NOTLDQUERY is set and there were no dots. 366 */ 367 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 368 !(tried_as_is || root_on_list)) { 369 ret = res_nquerydomain(statp, name, NULL, class, type, 370 answer, anslen); 371 if (ret > 0) 372 return (ret); 373 } 374 375 /* if we got here, we didn't satisfy the search. 376 * if we did an initial full query, return that query's H_ERRNO 377 * (note that we wouldn't be here if that query had succeeded). 378 * else if we ever got a nodata, send that back as the reason. 379 * else send back meaningless H_ERRNO, that being the one from 380 * the last DNSRCH we did. 381 */ 382 giveup: 383 if (saved_herrno != -1) 384 RES_SET_H_ERRNO(statp, saved_herrno); 385 else if (got_nodata) 386 RES_SET_H_ERRNO(statp, NO_DATA); 387 else if (got_servfail) 388 RES_SET_H_ERRNO(statp, TRY_AGAIN); 389 return (-1); 390 } 391 392 /*% 393 * Perform a call on res_query on the concatenation of name and domain, 394 * removing a trailing dot from name if domain is NULL. 395 */ 396 int 397 res_nquerydomain(res_state statp, 398 const char *name, 399 const char *domain, 400 int class, int type, /*%< class and type of query */ 401 u_char *answer, /*%< buffer to put answer */ 402 int anslen) /*%< size of answer */ 403 { 404 char nbuf[MAXDNAME]; 405 const char *longname = nbuf; 406 int n, d; 407 408 #ifdef DEBUG 409 if (statp->options & RES_DEBUG) 410 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 411 name, domain?domain:"<Nil>", class, type); 412 #endif 413 if (domain == NULL) { 414 /* 415 * Check for trailing '.'; 416 * copy without '.' if present. 417 */ 418 n = strlen(name); 419 if (n >= MAXDNAME) { 420 RES_SET_H_ERRNO(statp, NO_RECOVERY); 421 return (-1); 422 } 423 n--; 424 if (n >= 0 && name[n] == '.') { 425 strncpy(nbuf, name, n); 426 nbuf[n] = '\0'; 427 } else 428 longname = name; 429 } else { 430 n = strlen(name); 431 d = strlen(domain); 432 if (n + d + 1 >= MAXDNAME) { 433 RES_SET_H_ERRNO(statp, NO_RECOVERY); 434 return (-1); 435 } 436 sprintf(nbuf, "%s.%s", name, domain); 437 } 438 return (res_nquery(statp, longname, class, type, answer, anslen)); 439 } 440 441 const char * 442 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 443 char *file, *cp1, *cp2; 444 char buf[BUFSIZ]; 445 FILE *fp; 446 447 if (statp->options & RES_NOALIASES) 448 return (NULL); 449 if (issetugid()) 450 return (NULL); 451 file = getenv("HOSTALIASES"); 452 if (file == NULL || (fp = fopen(file, "r")) == NULL) 453 return (NULL); 454 setbuf(fp, NULL); 455 buf[sizeof(buf) - 1] = '\0'; 456 while (fgets(buf, sizeof(buf), fp)) { 457 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 458 ; 459 if (!*cp1) 460 break; 461 *cp1 = '\0'; 462 if (ns_samename(buf, name) == 1) { 463 while (isspace((unsigned char)*++cp1)) 464 ; 465 if (!*cp1) 466 break; 467 for (cp2 = cp1 + 1; *cp2 && 468 !isspace((unsigned char)*cp2); ++cp2) 469 ; 470 *cp2 = '\0'; 471 strncpy(dst, cp1, siz - 1); 472 dst[siz - 1] = '\0'; 473 fclose(fp); 474 return (dst); 475 } 476 } 477 fclose(fp); 478 return (NULL); 479 } 480 481 /*! \file */ 482