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 /* Options. Leave them on. */ 85 #ifndef DEBUG 86 #define DEBUG 87 #endif 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 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 if (n > 0 && (statp->options & RES_NSID) != 0U) { 134 rdata = &buf[n]; 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 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 if (errno == ECONNREFUSED) { 247 RES_SET_H_ERRNO(statp, TRY_AGAIN); 248 return (-1); 249 } 250 switch (statp->res_h_errno) { 251 case NO_DATA: 252 case HOST_NOT_FOUND: 253 break; 254 case TRY_AGAIN: 255 if (hp->rcode == SERVFAIL) 256 break; 257 /* FALLTHROUGH */ 258 default: 259 return (-1); 260 } 261 saved_herrno = statp->res_h_errno; 262 tried_as_is++; 263 } 264 265 /* 266 * We do at least one level of search if 267 * - there is no dot and RES_DEFNAME is set, or 268 * - there is at least one dot, there is no trailing dot, 269 * and RES_DNSRCH is set. 270 */ 271 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 272 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 273 int done = 0; 274 275 for (domain = (const char * const *)statp->dnsrch; 276 *domain && !done; 277 domain++) { 278 searched = 1; 279 280 if (domain[0][0] == '\0' || 281 (domain[0][0] == '.' && domain[0][1] == '\0')) 282 root_on_list++; 283 284 if (root_on_list && tried_as_is) 285 continue; 286 287 ret = res_nquerydomain(statp, name, *domain, 288 class, type, 289 answer, anslen); 290 if (ret > 0) 291 return (ret); 292 293 /* 294 * If no server present, give up. 295 * If name isn't found in this domain, 296 * keep trying higher domains in the search list 297 * (if that's enabled). 298 * On a NO_DATA error, keep trying, otherwise 299 * a wildcard entry of another type could keep us 300 * from finding this entry higher in the domain. 301 * If we get some other error (negative answer or 302 * server failure), then stop searching up, 303 * but try the input name below in case it's 304 * fully-qualified. 305 */ 306 if (errno == ECONNREFUSED) { 307 RES_SET_H_ERRNO(statp, TRY_AGAIN); 308 return (-1); 309 } 310 311 switch (statp->res_h_errno) { 312 case NO_DATA: 313 got_nodata++; 314 /* FALLTHROUGH */ 315 case HOST_NOT_FOUND: 316 /* keep trying */ 317 break; 318 case TRY_AGAIN: 319 /* 320 * This can occur due to a server failure 321 * (that is, all listed servers have failed), 322 * or all listed servers have timed out. 323 * ((HEADER *)answer)->rcode may not be set 324 * to SERVFAIL in the case of a timeout. 325 * 326 * Either way we must return TRY_AGAIN in 327 * order to avoid non-deterministic 328 * return codes. 329 * For example, loaded name servers or races 330 * against network startup/validation (dhcp, 331 * ppp, etc) can cause the search to timeout 332 * on one search element, e.g. 'fu.bar.com', 333 * and return a definitive failure on the 334 * next search element, e.g. 'fu.'. 335 */ 336 got_servfail++; 337 if (hp->rcode == SERVFAIL) { 338 /* try next search element, if any */ 339 break; 340 } 341 /* FALLTHROUGH */ 342 default: 343 /* anything else implies that we're done */ 344 done++; 345 } 346 347 /* if we got here for some reason other than DNSRCH, 348 * we only wanted one iteration of the loop, so stop. 349 */ 350 if ((statp->options & RES_DNSRCH) == 0U) 351 done++; 352 } 353 } 354 355 switch (statp->res_h_errno) { 356 case NO_DATA: 357 case HOST_NOT_FOUND: 358 break; 359 case TRY_AGAIN: 360 if (hp->rcode == SERVFAIL) 361 break; 362 /* FALLTHROUGH */ 363 default: 364 goto giveup; 365 } 366 367 /* 368 * If the query has not already been tried as is then try it 369 * unless RES_NOTLDQUERY is set and there were no dots. 370 */ 371 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 372 !(tried_as_is || root_on_list)) { 373 ret = res_nquerydomain(statp, name, NULL, class, type, 374 answer, anslen); 375 if (ret > 0) 376 return (ret); 377 } 378 379 /* if we got here, we didn't satisfy the search. 380 * if we did an initial full query, return that query's H_ERRNO 381 * (note that we wouldn't be here if that query had succeeded). 382 * else if we ever got a nodata, send that back as the reason. 383 * else send back meaningless H_ERRNO, that being the one from 384 * the last DNSRCH we did. 385 */ 386 giveup: 387 if (saved_herrno != -1) 388 RES_SET_H_ERRNO(statp, saved_herrno); 389 else if (got_nodata) 390 RES_SET_H_ERRNO(statp, NO_DATA); 391 else if (got_servfail) 392 RES_SET_H_ERRNO(statp, TRY_AGAIN); 393 return (-1); 394 } 395 396 /*% 397 * Perform a call on res_query on the concatenation of name and domain, 398 * removing a trailing dot from name if domain is NULL. 399 */ 400 int 401 res_nquerydomain(res_state statp, 402 const char *name, 403 const char *domain, 404 int class, int type, /*%< class and type of query */ 405 u_char *answer, /*%< buffer to put answer */ 406 int anslen) /*%< size of answer */ 407 { 408 char nbuf[MAXDNAME]; 409 const char *longname = nbuf; 410 int n, d; 411 412 #ifdef DEBUG 413 if (statp->options & RES_DEBUG) 414 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 415 name, domain?domain:"<Nil>", class, type); 416 #endif 417 if (domain == NULL) { 418 /* 419 * Check for trailing '.'; 420 * copy without '.' if present. 421 */ 422 n = strlen(name); 423 if (n >= MAXDNAME) { 424 RES_SET_H_ERRNO(statp, NO_RECOVERY); 425 return (-1); 426 } 427 n--; 428 if (n >= 0 && name[n] == '.') { 429 strncpy(nbuf, name, n); 430 nbuf[n] = '\0'; 431 } else 432 longname = name; 433 } else { 434 n = strlen(name); 435 d = strlen(domain); 436 if (n + d + 1 >= MAXDNAME) { 437 RES_SET_H_ERRNO(statp, NO_RECOVERY); 438 return (-1); 439 } 440 sprintf(nbuf, "%s.%s", name, domain); 441 } 442 return (res_nquery(statp, longname, class, type, answer, anslen)); 443 } 444 445 const char * 446 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 447 char *file, *cp1, *cp2; 448 char buf[BUFSIZ]; 449 FILE *fp; 450 451 if (statp->options & RES_NOALIASES) 452 return (NULL); 453 file = secure_getenv("HOSTALIASES"); 454 if (file == NULL || (fp = fopen(file, "re")) == NULL) 455 return (NULL); 456 setbuf(fp, NULL); 457 buf[sizeof(buf) - 1] = '\0'; 458 while (fgets(buf, sizeof(buf), fp)) { 459 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 460 ; 461 if (!*cp1) 462 break; 463 *cp1 = '\0'; 464 if (ns_samename(buf, name) == 1) { 465 while (isspace((unsigned char)*++cp1)) 466 ; 467 if (!*cp1) 468 break; 469 for (cp2 = cp1 + 1; *cp2 && 470 !isspace((unsigned char)*cp2); ++cp2) 471 ; 472 *cp2 = '\0'; 473 strncpy(dst, cp1, siz - 1); 474 dst[siz - 1] = '\0'; 475 fclose(fp); 476 return (dst); 477 } 478 } 479 fclose(fp); 480 return (NULL); 481 } 482 483 /*! \file */ 484