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