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 #if defined(LIBC_SCCS) && !defined(lint) 70 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; 71 static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $"; 72 #endif /* LIBC_SCCS and not lint */ 73 #include <sys/cdefs.h> 74 __FBSDID("$FreeBSD$"); 75 76 #include "port_before.h" 77 #include <sys/param.h> 78 #include <netinet/in.h> 79 #include <arpa/inet.h> 80 #include <arpa/nameser.h> 81 #include <ctype.h> 82 #include <errno.h> 83 #include <netdb.h> 84 #include <resolv.h> 85 #include <stdio.h> 86 #include <stdlib.h> 87 #include <string.h> 88 #include <unistd.h> 89 #include "port_after.h" 90 91 /* Options. Leave them on. */ 92 #ifndef DEBUG 93 #define DEBUG 94 #endif 95 96 #if PACKETSZ > 1024 97 #define MAXPACKET PACKETSZ 98 #else 99 #define MAXPACKET 1024 100 #endif 101 102 /*% 103 * Formulate a normal query, send, and await answer. 104 * Returned answer is placed in supplied buffer "answer". 105 * Perform preliminary check of answer, returning success only 106 * if no error is indicated and the answer count is nonzero. 107 * Return the size of the response on success, -1 on error. 108 * Error number is left in H_ERRNO. 109 * 110 * Caller must parse answer and determine whether it answers the question. 111 */ 112 int 113 res_nquery(res_state statp, 114 const char *name, /*%< domain name */ 115 int class, int type, /*%< class and type of query */ 116 u_char *answer, /*%< buffer to put answer */ 117 int anslen) /*%< size of answer buffer */ 118 { 119 u_char buf[MAXPACKET]; 120 HEADER *hp = (HEADER *) answer; 121 u_int oflags; 122 u_char *rdata; 123 int n; 124 125 oflags = statp->_flags; 126 127 again: 128 hp->rcode = NOERROR; /*%< default */ 129 #ifdef DEBUG 130 if (statp->options & RES_DEBUG) 131 printf(";; res_query(%s, %d, %d)\n", name, class, type); 132 #endif 133 134 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 135 buf, sizeof(buf)); 136 #ifdef RES_USE_EDNS0 137 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 138 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) { 139 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 140 if (n > 0 && (statp->options & RES_NSID) != 0U) { 141 rdata = &buf[n]; 142 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata, 143 NS_OPT_NSID, 0, NULL); 144 } 145 } 146 #endif 147 if (n <= 0) { 148 #ifdef DEBUG 149 if (statp->options & RES_DEBUG) 150 printf(";; res_query: mkquery failed\n"); 151 #endif 152 RES_SET_H_ERRNO(statp, NO_RECOVERY); 153 return (n); 154 } 155 156 n = res_nsend(statp, buf, n, answer, anslen); 157 if (n < 0) { 158 #ifdef RES_USE_EDNS0 159 /* if the query choked with EDNS0, retry without EDNS0 */ 160 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 161 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 162 statp->_flags |= RES_F_EDNS0ERR; 163 if (statp->options & RES_DEBUG) 164 printf(";; res_nquery: retry without EDNS0\n"); 165 goto again; 166 } 167 #endif 168 #ifdef DEBUG 169 if (statp->options & RES_DEBUG) 170 printf(";; res_query: send error\n"); 171 #endif 172 RES_SET_H_ERRNO(statp, TRY_AGAIN); 173 return (n); 174 } 175 176 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 177 #ifdef DEBUG 178 if (statp->options & RES_DEBUG) 179 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 180 p_rcode(hp->rcode), 181 ntohs(hp->ancount), 182 ntohs(hp->nscount), 183 ntohs(hp->arcount)); 184 #endif 185 switch (hp->rcode) { 186 case NXDOMAIN: 187 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 188 break; 189 case SERVFAIL: 190 RES_SET_H_ERRNO(statp, TRY_AGAIN); 191 break; 192 case NOERROR: 193 RES_SET_H_ERRNO(statp, NO_DATA); 194 break; 195 case FORMERR: 196 case NOTIMP: 197 case REFUSED: 198 default: 199 RES_SET_H_ERRNO(statp, NO_RECOVERY); 200 break; 201 } 202 return (-1); 203 } 204 return (n); 205 } 206 207 /*% 208 * Formulate a normal query, send, and retrieve answer in supplied buffer. 209 * Return the size of the response on success, -1 on error. 210 * If enabled, implement search rules until answer or unrecoverable failure 211 * is detected. Error code, if any, is left in H_ERRNO. 212 */ 213 int 214 res_nsearch(res_state statp, 215 const char *name, /*%< domain name */ 216 int class, int type, /*%< class and type of query */ 217 u_char *answer, /*%< buffer to put answer */ 218 int anslen) /*%< size of answer */ 219 { 220 const char *cp, * const *domain; 221 HEADER *hp = (HEADER *) answer; 222 char tmp[NS_MAXDNAME]; 223 u_int dots; 224 int trailing_dot, ret, saved_herrno; 225 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 226 int tried_as_is = 0; 227 int searched = 0; 228 229 errno = 0; 230 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 231 dots = 0; 232 for (cp = name; *cp != '\0'; cp++) 233 dots += (*cp == '.'); 234 trailing_dot = 0; 235 if (cp > name && *--cp == '.') 236 trailing_dot++; 237 238 /* If there aren't any dots, it could be a user-level alias. */ 239 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 240 return (res_nquery(statp, cp, class, type, answer, anslen)); 241 242 /* 243 * If there are enough dots in the name, let's just give it a 244 * try 'as is'. The threshold can be set with the "ndots" option. 245 * Also, query 'as is', if there is a trailing dot in the name. 246 */ 247 saved_herrno = -1; 248 if (dots >= statp->ndots || trailing_dot) { 249 ret = res_nquerydomain(statp, name, NULL, class, type, 250 answer, anslen); 251 if (ret > 0 || trailing_dot) 252 return (ret); 253 if (errno == ECONNREFUSED) { 254 RES_SET_H_ERRNO(statp, TRY_AGAIN); 255 return (-1); 256 } 257 switch (statp->res_h_errno) { 258 case NO_DATA: 259 case HOST_NOT_FOUND: 260 break; 261 case TRY_AGAIN: 262 if (hp->rcode == SERVFAIL) 263 break; 264 /* FALLTHROUGH */ 265 default: 266 return (-1); 267 } 268 saved_herrno = statp->res_h_errno; 269 tried_as_is++; 270 } 271 272 /* 273 * We do at least one level of search if 274 * - there is no dot and RES_DEFNAME is set, or 275 * - there is at least one dot, there is no trailing dot, 276 * and RES_DNSRCH is set. 277 */ 278 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 279 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 280 int done = 0; 281 282 for (domain = (const char * const *)statp->dnsrch; 283 *domain && !done; 284 domain++) { 285 searched = 1; 286 287 if (domain[0][0] == '\0' || 288 (domain[0][0] == '.' && domain[0][1] == '\0')) 289 root_on_list++; 290 291 if (root_on_list && tried_as_is) 292 continue; 293 294 ret = res_nquerydomain(statp, name, *domain, 295 class, type, 296 answer, anslen); 297 if (ret > 0) 298 return (ret); 299 300 /* 301 * If no server present, give up. 302 * If name isn't found in this domain, 303 * keep trying higher domains in the search list 304 * (if that's enabled). 305 * On a NO_DATA error, keep trying, otherwise 306 * a wildcard entry of another type could keep us 307 * from finding this entry higher in the domain. 308 * If we get some other error (negative answer or 309 * server failure), then stop searching up, 310 * but try the input name below in case it's 311 * fully-qualified. 312 */ 313 if (errno == ECONNREFUSED) { 314 RES_SET_H_ERRNO(statp, TRY_AGAIN); 315 return (-1); 316 } 317 318 switch (statp->res_h_errno) { 319 case NO_DATA: 320 got_nodata++; 321 /* FALLTHROUGH */ 322 case HOST_NOT_FOUND: 323 /* keep trying */ 324 break; 325 case TRY_AGAIN: 326 /* 327 * This can occur due to a server failure 328 * (that is, all listed servers have failed), 329 * or all listed servers have timed out. 330 * ((HEADER *)answer)->rcode may not be set 331 * to SERVFAIL in the case of a timeout. 332 * 333 * Either way we must return TRY_AGAIN in 334 * order to avoid non-deterministic 335 * return codes. 336 * For example, loaded name servers or races 337 * against network startup/validation (dhcp, 338 * ppp, etc) can cause the search to timeout 339 * on one search element, e.g. 'fu.bar.com', 340 * and return a definitive failure on the 341 * next search element, e.g. 'fu.'. 342 */ 343 got_servfail++; 344 if (hp->rcode == SERVFAIL) { 345 /* try next search element, if any */ 346 break; 347 } 348 /* FALLTHROUGH */ 349 default: 350 /* anything else implies that we're done */ 351 done++; 352 } 353 354 /* if we got here for some reason other than DNSRCH, 355 * we only wanted one iteration of the loop, so stop. 356 */ 357 if ((statp->options & RES_DNSRCH) == 0U) 358 done++; 359 } 360 } 361 362 switch (statp->res_h_errno) { 363 case NO_DATA: 364 case HOST_NOT_FOUND: 365 break; 366 case TRY_AGAIN: 367 if (hp->rcode == SERVFAIL) 368 break; 369 /* FALLTHROUGH */ 370 default: 371 goto giveup; 372 } 373 374 /* 375 * If the query has not already been tried as is then try it 376 * unless RES_NOTLDQUERY is set and there were no dots. 377 */ 378 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 379 !(tried_as_is || root_on_list)) { 380 ret = res_nquerydomain(statp, name, NULL, class, type, 381 answer, anslen); 382 if (ret > 0) 383 return (ret); 384 } 385 386 /* if we got here, we didn't satisfy the search. 387 * if we did an initial full query, return that query's H_ERRNO 388 * (note that we wouldn't be here if that query had succeeded). 389 * else if we ever got a nodata, send that back as the reason. 390 * else send back meaningless H_ERRNO, that being the one from 391 * the last DNSRCH we did. 392 */ 393 giveup: 394 if (saved_herrno != -1) 395 RES_SET_H_ERRNO(statp, saved_herrno); 396 else if (got_nodata) 397 RES_SET_H_ERRNO(statp, NO_DATA); 398 else if (got_servfail) 399 RES_SET_H_ERRNO(statp, TRY_AGAIN); 400 return (-1); 401 } 402 403 /*% 404 * Perform a call on res_query on the concatenation of name and domain, 405 * removing a trailing dot from name if domain is NULL. 406 */ 407 int 408 res_nquerydomain(res_state statp, 409 const char *name, 410 const char *domain, 411 int class, int type, /*%< class and type of query */ 412 u_char *answer, /*%< buffer to put answer */ 413 int anslen) /*%< size of answer */ 414 { 415 char nbuf[MAXDNAME]; 416 const char *longname = nbuf; 417 int n, d; 418 419 #ifdef DEBUG 420 if (statp->options & RES_DEBUG) 421 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 422 name, domain?domain:"<Nil>", class, type); 423 #endif 424 if (domain == NULL) { 425 /* 426 * Check for trailing '.'; 427 * copy without '.' if present. 428 */ 429 n = strlen(name); 430 if (n >= MAXDNAME) { 431 RES_SET_H_ERRNO(statp, NO_RECOVERY); 432 return (-1); 433 } 434 n--; 435 if (n >= 0 && name[n] == '.') { 436 strncpy(nbuf, name, n); 437 nbuf[n] = '\0'; 438 } else 439 longname = name; 440 } else { 441 n = strlen(name); 442 d = strlen(domain); 443 if (n + d + 1 >= MAXDNAME) { 444 RES_SET_H_ERRNO(statp, NO_RECOVERY); 445 return (-1); 446 } 447 sprintf(nbuf, "%s.%s", name, domain); 448 } 449 return (res_nquery(statp, longname, class, type, answer, anslen)); 450 } 451 452 const char * 453 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 454 char *file, *cp1, *cp2; 455 char buf[BUFSIZ]; 456 FILE *fp; 457 458 if (statp->options & RES_NOALIASES) 459 return (NULL); 460 if (issetugid()) 461 return (NULL); 462 file = getenv("HOSTALIASES"); 463 if (file == NULL || (fp = fopen(file, "re")) == NULL) 464 return (NULL); 465 setbuf(fp, NULL); 466 buf[sizeof(buf) - 1] = '\0'; 467 while (fgets(buf, sizeof(buf), fp)) { 468 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 469 ; 470 if (!*cp1) 471 break; 472 *cp1 = '\0'; 473 if (ns_samename(buf, name) == 1) { 474 while (isspace((unsigned char)*++cp1)) 475 ; 476 if (!*cp1) 477 break; 478 for (cp2 = cp1 + 1; *cp2 && 479 !isspace((unsigned char)*cp2); ++cp2) 480 ; 481 *cp2 = '\0'; 482 strncpy(dst, cp1, siz - 1); 483 dst[siz - 1] = '\0'; 484 fclose(fp); 485 return (dst); 486 } 487 } 488 fclose(fp); 489 return (NULL); 490 } 491 492 /*! \file */ 493