1/* $NetBSD: res_query.c,v 1.17 2023/08/01 08:47:25 mrg Exp $ */ 2 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/* 70 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 71 * Portions Copyright (c) 1996-1999 by Internet Software Consortium. 72 * 73 * Permission to use, copy, modify, and distribute this software for any 74 * purpose with or without fee is hereby granted, provided that the above 75 * copyright notice and this permission notice appear in all copies. 76 * 77 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 78 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 79 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 80 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 81 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 82 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 83 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 84 */ 85 86#include <sys/cdefs.h> 87#if defined(LIBC_SCCS) && !defined(lint) 88#ifdef notdef 89static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; 90static const char rcsid[] = "Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp"; 91#else 92__RCSID("$NetBSD: res_query.c,v 1.17 2023/08/01 08:47:25 mrg Exp $"); 93#endif 94#endif /* LIBC_SCCS and not lint */ 95 96#include "port_before.h" 97 98#include "namespace.h" 99#include <sys/types.h> 100#include <sys/param.h> 101#include <netinet/in.h> 102#include <arpa/inet.h> 103#include <arpa/nameser.h> 104#include <ctype.h> 105#include <errno.h> 106#include <netdb.h> 107#include <resolv.h> 108#include <stdio.h> 109#include <stdlib.h> 110#include <unistd.h> 111#include <string.h> 112#include "port_after.h" 113 114#if 0 115#ifdef __weak_alias 116__weak_alias(res_nquery,_res_nquery) 117__weak_alias(res_nsearch,_res_nsearch) 118__weak_alias(res_nquerydomain,__res_nquerydomain) 119__weak_alias(res_hostalias,__res_hostalias) 120#endif 121#endif 122 123/* Options. Leave them on. */ 124#ifndef DEBUG 125#define DEBUG 126#endif 127 128#if PACKETSZ > 1024 129#define MAXPACKET PACKETSZ 130#else 131#define MAXPACKET 1024 132#endif 133 134/*% 135 * Formulate a normal query, send, and await answer. 136 * Returned answer is placed in supplied buffer "answer". 137 * Perform preliminary check of answer, returning success only 138 * if no error is indicated and the answer count is nonzero. 139 * Return the size of the response on success, -1 on error. 140 * Error number is left in H_ERRNO. 141 * 142 * Caller must parse answer and determine whether it answers the question. 143 */ 144int 145res_nquery(res_state statp, 146 const char *name, /*%< domain name */ 147 int class, int type, /*%< class and type of query */ 148 u_char *answer, /*%< buffer to put answer */ 149 int anslen) /*%< size of answer buffer */ 150{ 151 u_char buf[MAXPACKET]; 152 HEADER *hp = (HEADER *)(void *)answer; 153 u_int oflags; 154 u_char *rdata; 155 int n; 156 157 oflags = statp->_flags; 158 159again: 160 hp->rcode = NOERROR; /*%< default */ 161#ifdef DEBUG 162 if (statp->options & RES_DEBUG) 163 printf(";; res_query(%s, %d, %d)\n", name, class, type); 164#endif 165 166 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 167 buf, (int)sizeof(buf)); 168#ifdef RES_USE_EDNS0 169 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 170 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID)) != 0U) { 171 n = res_nopt(statp, n, buf, (int)sizeof(buf), anslen); 172 rdata = &buf[n]; 173 if (n > 0 && (statp->options & RES_NSID) != 0U) { 174 n = res_nopt_rdata(statp, n, buf, (int)sizeof(buf), 175 rdata, NS_OPT_NSID, 0, NULL); 176 } 177 } 178#endif 179 if (n <= 0) { 180#ifdef DEBUG 181 if (statp->options & RES_DEBUG) 182 printf(";; res_query: mkquery failed\n"); 183#endif 184 RES_SET_H_ERRNO(statp, NO_RECOVERY); 185 return (n); 186 } 187 188 n = res_nsend(statp, buf, n, answer, anslen); 189 if (n < 0) { 190#ifdef RES_USE_EDNS0 191 /* if the query choked with EDNS0, retry without EDNS0 */ 192 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 193 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 194 statp->_flags |= RES_F_EDNS0ERR; 195 if (statp->options & RES_DEBUG) 196 printf(";; res_nquery: retry without EDNS0\n"); 197 goto again; 198 } 199#endif 200#ifdef DEBUG 201 if (statp->options & RES_DEBUG) 202 printf(";; res_query: send error\n"); 203#endif 204 RES_SET_H_ERRNO(statp, TRY_AGAIN); 205 return (n); 206 } 207 208 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 209#ifdef DEBUG 210 if (statp->options & RES_DEBUG) 211 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 212 p_rcode(hp->rcode), 213 ntohs(hp->ancount), 214 ntohs(hp->nscount), 215 ntohs(hp->arcount)); 216#endif 217 switch (hp->rcode) { 218 case NXDOMAIN: 219 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 220 break; 221 case SERVFAIL: 222 RES_SET_H_ERRNO(statp, TRY_AGAIN); 223 break; 224 case NOERROR: 225 RES_SET_H_ERRNO(statp, NO_DATA); 226 break; 227 case FORMERR: 228 case NOTIMP: 229 case REFUSED: 230 default: 231 RES_SET_H_ERRNO(statp, NO_RECOVERY); 232 break; 233 } 234 return (-1); 235 } 236 return (n); 237} 238 239/*% 240 * Formulate a normal query, send, and retrieve answer in supplied buffer. 241 * Return the size of the response on success, -1 on error. 242 * If enabled, implement search rules until answer or unrecoverable failure 243 * is detected. Error code, if any, is left in H_ERRNO. 244 */ 245int 246res_nsearch(res_state statp, 247 const char *name, /*%< domain name */ 248 int class, int type, /*%< class and type of query */ 249 u_char *answer, /*%< buffer to put answer */ 250 int anslen) /*%< size of answer */ 251{ 252 const char *cp, * const *domain; 253 HEADER *hp = (HEADER *)(void *)answer; 254 char tmp[NS_MAXDNAME]; 255 u_int dots; 256 int trailing_dot, ret, saved_herrno; 257 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 258 int tried_as_is = 0; 259 int searched = 0; 260 261 errno = 0; 262 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 263 dots = 0; 264 for (cp = name; *cp != '\0'; cp++) 265 dots += (*cp == '.'); 266 trailing_dot = 0; 267 if (cp > name && *--cp == '.') 268 trailing_dot++; 269 270 /* If there aren't any dots, it could be a user-level alias. */ 271 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 272 return (res_nquery(statp, cp, class, type, answer, anslen)); 273 274 /* 275 * If there are enough dots in the name, let's just give it a 276 * try 'as is'. The threshold can be set with the "ndots" option. 277 * Also, query 'as is', if there is a trailing dot in the name. 278 */ 279 saved_herrno = -1; 280 if (dots >= statp->ndots || trailing_dot) { 281 ret = res_nquerydomain(statp, name, NULL, class, type, 282 answer, anslen); 283 if (ret > 0 || trailing_dot) 284 return (ret); 285 saved_herrno = statp->res_h_errno; 286 tried_as_is++; 287 } 288 289 /* 290 * We do at least one level of search if 291 * - there is no dot and RES_DEFNAME is set, or 292 * - there is at least one dot, there is no trailing dot, 293 * and RES_DNSRCH is set. 294 */ 295 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 296 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 297 int done = 0; 298 299 for (domain = (const char * const *)statp->dnsrch; 300 *domain && !done; 301 domain++) { 302 searched = 1; 303 304 if (domain[0][0] == '\0' || 305 (domain[0][0] == '.' && domain[0][1] == '\0')) 306 root_on_list++; 307 308 ret = res_nquerydomain(statp, name, *domain, 309 class, type, 310 answer, anslen); 311 if (ret > 0) 312 return (ret); 313 314 /* 315 * If no server present, give up. 316 * If name isn't found in this domain, 317 * keep trying higher domains in the search list 318 * (if that's enabled). 319 * On a NO_DATA error, keep trying, otherwise 320 * a wildcard entry of another type could keep us 321 * from finding this entry higher in the domain. 322 * If we get some other error (negative answer or 323 * server failure), then stop searching up, 324 * but try the input name below in case it's 325 * fully-qualified. 326 */ 327 if (errno == ECONNREFUSED) { 328 RES_SET_H_ERRNO(statp, TRY_AGAIN); 329 return (-1); 330 } 331 332 switch (statp->res_h_errno) { 333 case NO_DATA: 334 got_nodata++; 335 /* FALLTHROUGH */ 336 case HOST_NOT_FOUND: 337 /* keep trying */ 338 break; 339 case TRY_AGAIN: 340 if (hp->rcode == SERVFAIL) { 341 /* try next search element, if any */ 342 got_servfail++; 343 break; 344 } 345 /* FALLTHROUGH */ 346 default: 347 /* anything else implies that we're done */ 348 done++; 349 } 350 351 /* if we got here for some reason other than DNSRCH, 352 * we only wanted one iteration of the loop, so stop. 353 */ 354 if ((statp->options & RES_DNSRCH) == 0U) 355 done++; 356 } 357 } 358 359 /* 360 * If the query has not already been tried as is then try it 361 * unless RES_NOTLDQUERY is set and there were no dots. 362 */ 363 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 364 !(tried_as_is || root_on_list)) { 365 ret = res_nquerydomain(statp, name, NULL, class, type, 366 answer, anslen); 367 if (ret > 0) 368 return (ret); 369 } 370 371 /* if we got here, we didn't satisfy the search. 372 * if we did an initial full query, return that query's H_ERRNO 373 * (note that we wouldn't be here if that query had succeeded). 374 * else if we ever got a nodata, send that back as the reason. 375 * else send back meaningless H_ERRNO, that being the one from 376 * the last DNSRCH we did. 377 */ 378 if (saved_herrno != -1) 379 RES_SET_H_ERRNO(statp, saved_herrno); 380 else if (got_nodata) 381 RES_SET_H_ERRNO(statp, NO_DATA); 382 else if (got_servfail) 383 RES_SET_H_ERRNO(statp, TRY_AGAIN); 384 return (-1); 385} 386 387/*% 388 * Perform a call on res_query on the concatenation of name and domain, 389 * removing a trailing dot from name if domain is NULL. 390 */ 391int 392res_nquerydomain(res_state statp, 393 const char *name, 394 const char *domain, 395 int class, int type, /*%< class and type of query */ 396 u_char *answer, /*%< buffer to put answer */ 397 int anslen) /*%< size of answer */ 398{ 399 char nbuf[MAXDNAME]; 400 const char *longname = nbuf; 401 size_t n; 402 403#ifdef DEBUG 404 if (statp->options & RES_DEBUG) 405 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 406 name, domain?domain:"<Nil>", class, type); 407#endif 408 if (domain == NULL) { 409 /* 410 * Check for trailing '.'; 411 * copy without '.' if present. 412 */ 413 n = strlen(name); 414 if (n >= MAXDNAME) { 415 RES_SET_H_ERRNO(statp, NO_RECOVERY); 416 return (-1); 417 } 418 if (n && name[--n] == '.') { 419 snprintf(nbuf, sizeof(nbuf), "%*s", (int)n, name); 420 } else 421 longname = name; 422 } else { 423 if ((size_t)snprintf(nbuf, sizeof(nbuf), "%s.%s", 424 name, domain) >= sizeof(nbuf)) { 425 RES_SET_H_ERRNO(statp, NO_RECOVERY); 426 return (-1); 427 } 428 } 429 return (res_nquery(statp, longname, class, type, answer, anslen)); 430} 431 432const char * 433res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 434 char *file, *cp1, *cp2; 435 char buf[BUFSIZ]; 436 FILE *fp; 437 438 if (statp->options & RES_NOALIASES) 439 return (NULL); 440 /* 441 * forbid hostaliases for setuid binary, due to possible security 442 * breach. 443 */ 444 if (issetugid()) 445 return (NULL); 446 file = getenv("HOSTALIASES"); 447 if (file == NULL || (fp = fopen(file, "re")) == NULL) 448 return (NULL); 449 buf[sizeof(buf) - 1] = '\0'; 450 while (fgets(buf, (int)sizeof(buf), fp)) { 451 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 452 ; 453 if (!*cp1) 454 break; 455 *cp1 = '\0'; 456 if (ns_samename(buf, name) == 1) { 457 while (isspace((unsigned char)*++cp1)) 458 ; 459 if (!*cp1) 460 break; 461 for (cp2 = cp1 + 1; *cp2 && 462 !isspace((unsigned char)*cp2); ++cp2) 463 ; 464 *cp2 = '\0'; 465 strncpy(dst, cp1, siz - 1); 466 dst[siz - 1] = '\0'; 467 fclose(fp); 468 return (dst); 469 } 470 } 471 fclose(fp); 472 return (NULL); 473} 474 475/*! \file */ 476