1 /* $NetBSD: res_query.c,v 1.9 2007/03/30 20:23:05 ghen Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 /* 37 * Portions Copyright (c) 1993 by Digital Equipment Corporation. 38 * 39 * Permission to use, copy, modify, and distribute this software for any 40 * purpose with or without fee is hereby granted, provided that the above 41 * copyright notice and this permission notice appear in all copies, and that 42 * the name of Digital Equipment Corporation not be used in advertising or 43 * publicity pertaining to distribution of the document or software without 44 * specific, written prior permission. 45 * 46 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL 47 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES 48 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT 49 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 50 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 51 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 52 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 53 * SOFTWARE. 54 */ 55 56 /* 57 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 58 * Portions Copyright (c) 1996-1999 by Internet Software Consortium. 59 * 60 * Permission to use, copy, modify, and distribute this software for any 61 * purpose with or without fee is hereby granted, provided that the above 62 * copyright notice and this permission notice appear in all copies. 63 * 64 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 65 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 66 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 67 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 68 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 69 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 70 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 71 */ 72 73 #include <sys/cdefs.h> 74 #if defined(LIBC_SCCS) && !defined(lint) 75 #ifdef notdef 76 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; 77 static const char rcsid[] = "Id: res_query.c,v 1.7.18.1 2005/04/27 05:01:11 sra Exp"; 78 #else 79 __RCSID("$NetBSD: res_query.c,v 1.9 2007/03/30 20:23:05 ghen Exp $"); 80 #endif 81 #endif /* LIBC_SCCS and not lint */ 82 83 #include "port_before.h" 84 85 #include "namespace.h" 86 #include <sys/types.h> 87 #include <sys/param.h> 88 #include <netinet/in.h> 89 #include <arpa/inet.h> 90 #include <arpa/nameser.h> 91 #include <ctype.h> 92 #include <errno.h> 93 #include <netdb.h> 94 #include <resolv.h> 95 #include <stdio.h> 96 #include <stdlib.h> 97 #include <unistd.h> 98 #include <string.h> 99 #include "port_after.h" 100 101 #if 0 102 #ifdef __weak_alias 103 __weak_alias(res_nquery,_res_nquery) 104 __weak_alias(res_nsearch,_res_nsearch) 105 __weak_alias(res_nquerydomain,__res_nquerydomain) 106 __weak_alias(res_hostalias,__res_hostalias) 107 #endif 108 #endif 109 110 /* Options. Leave them on. */ 111 #ifndef DEBUG 112 #define DEBUG 113 #endif 114 115 #if PACKETSZ > 1024 116 #define MAXPACKET PACKETSZ 117 #else 118 #define MAXPACKET 1024 119 #endif 120 121 /*% 122 * Formulate a normal query, send, and await answer. 123 * Returned answer is placed in supplied buffer "answer". 124 * Perform preliminary check of answer, returning success only 125 * if no error is indicated and the answer count is nonzero. 126 * Return the size of the response on success, -1 on error. 127 * Error number is left in H_ERRNO. 128 * 129 * Caller must parse answer and determine whether it answers the question. 130 */ 131 int 132 res_nquery(res_state statp, 133 const char *name, /*%< domain name */ 134 int class, int type, /*%< class and type of query */ 135 u_char *answer, /*%< buffer to put answer */ 136 int anslen) /*%< size of answer buffer */ 137 { 138 u_char buf[MAXPACKET]; 139 HEADER *hp = (HEADER *)(void *)answer; 140 int n; 141 u_int oflags; 142 143 oflags = statp->_flags; 144 145 again: 146 hp->rcode = NOERROR; /*%< default */ 147 #ifdef DEBUG 148 if (statp->options & RES_DEBUG) 149 printf(";; res_query(%s, %d, %d)\n", name, class, type); 150 #endif 151 152 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 153 buf, sizeof(buf)); 154 #ifdef RES_USE_EDNS0 155 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 156 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U) 157 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 158 #endif 159 if (n <= 0) { 160 #ifdef DEBUG 161 if (statp->options & RES_DEBUG) 162 printf(";; res_query: mkquery failed\n"); 163 #endif 164 RES_SET_H_ERRNO(statp, NO_RECOVERY); 165 return (n); 166 } 167 n = res_nsend(statp, buf, n, answer, anslen); 168 if (n < 0) { 169 #ifdef RES_USE_EDNS0 170 /* if the query choked with EDNS0, retry without EDNS0 */ 171 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 172 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 173 statp->_flags |= RES_F_EDNS0ERR; 174 if (statp->options & RES_DEBUG) 175 printf(";; res_nquery: retry without EDNS0\n"); 176 goto again; 177 } 178 #endif 179 #ifdef DEBUG 180 if (statp->options & RES_DEBUG) 181 printf(";; res_query: send error\n"); 182 #endif 183 RES_SET_H_ERRNO(statp, TRY_AGAIN); 184 return (n); 185 } 186 187 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 188 #ifdef DEBUG 189 if (statp->options & RES_DEBUG) 190 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 191 p_rcode(hp->rcode), 192 ntohs(hp->ancount), 193 ntohs(hp->nscount), 194 ntohs(hp->arcount)); 195 #endif 196 switch (hp->rcode) { 197 case NXDOMAIN: 198 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 199 break; 200 case SERVFAIL: 201 RES_SET_H_ERRNO(statp, TRY_AGAIN); 202 break; 203 case NOERROR: 204 RES_SET_H_ERRNO(statp, NO_DATA); 205 break; 206 case FORMERR: 207 case NOTIMP: 208 case REFUSED: 209 default: 210 RES_SET_H_ERRNO(statp, NO_RECOVERY); 211 break; 212 } 213 return (-1); 214 } 215 return (n); 216 } 217 218 /*% 219 * Formulate a normal query, send, and retrieve answer in supplied buffer. 220 * Return the size of the response on success, -1 on error. 221 * If enabled, implement search rules until answer or unrecoverable failure 222 * is detected. Error code, if any, is left in H_ERRNO. 223 */ 224 int 225 res_nsearch(res_state statp, 226 const char *name, /*%< domain name */ 227 int class, int type, /*%< class and type of query */ 228 u_char *answer, /*%< buffer to put answer */ 229 int anslen) /*%< size of answer */ 230 { 231 const char *cp, * const *domain; 232 HEADER *hp = (HEADER *)(void *)answer; 233 char tmp[NS_MAXDNAME]; 234 u_int dots; 235 int trailing_dot, ret, saved_herrno; 236 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 237 int tried_as_is = 0; 238 int searched = 0; 239 240 errno = 0; 241 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 242 dots = 0; 243 for (cp = name; *cp != '\0'; cp++) 244 dots += (*cp == '.'); 245 trailing_dot = 0; 246 if (cp > name && *--cp == '.') 247 trailing_dot++; 248 249 /* If there aren't any dots, it could be a user-level alias. */ 250 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 251 return (res_nquery(statp, cp, class, type, answer, anslen)); 252 253 /* 254 * If there are enough dots in the name, let's just give it a 255 * try 'as is'. The threshold can be set with the "ndots" option. 256 * Also, query 'as is', if there is a trailing dot in the name. 257 */ 258 saved_herrno = -1; 259 if (dots >= statp->ndots || trailing_dot) { 260 ret = res_nquerydomain(statp, name, NULL, class, type, 261 answer, anslen); 262 if (ret > 0 || trailing_dot) 263 return (ret); 264 saved_herrno = statp->res_h_errno; 265 tried_as_is++; 266 } 267 268 /* 269 * We do at least one level of search if 270 * - there is no dot and RES_DEFNAME is set, or 271 * - there is at least one dot, there is no trailing dot, 272 * and RES_DNSRCH is set. 273 */ 274 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 275 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 276 int done = 0; 277 278 for (domain = (const char * const *)statp->dnsrch; 279 *domain && !done; 280 domain++) { 281 searched = 1; 282 283 if (domain[0][0] == '\0' || 284 (domain[0][0] == '.' && domain[0][1] == '\0')) 285 root_on_list++; 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 if (hp->rcode == SERVFAIL) { 320 /* try next search element, if any */ 321 got_servfail++; 322 break; 323 } 324 /* FALLTHROUGH */ 325 default: 326 /* anything else implies that we're done */ 327 done++; 328 } 329 330 /* if we got here for some reason other than DNSRCH, 331 * we only wanted one iteration of the loop, so stop. 332 */ 333 if ((statp->options & RES_DNSRCH) == 0U) 334 done++; 335 } 336 } 337 338 /* 339 * If the query has not already been tried as is then try it 340 * unless RES_NOTLDQUERY is set and there were no dots. 341 */ 342 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 343 !(tried_as_is || root_on_list)) { 344 ret = res_nquerydomain(statp, name, NULL, class, type, 345 answer, anslen); 346 if (ret > 0) 347 return (ret); 348 } 349 350 /* if we got here, we didn't satisfy the search. 351 * if we did an initial full query, return that query's H_ERRNO 352 * (note that we wouldn't be here if that query had succeeded). 353 * else if we ever got a nodata, send that back as the reason. 354 * else send back meaningless H_ERRNO, that being the one from 355 * the last DNSRCH we did. 356 */ 357 if (saved_herrno != -1) 358 RES_SET_H_ERRNO(statp, saved_herrno); 359 else if (got_nodata) 360 RES_SET_H_ERRNO(statp, NO_DATA); 361 else if (got_servfail) 362 RES_SET_H_ERRNO(statp, TRY_AGAIN); 363 return (-1); 364 } 365 366 /*% 367 * Perform a call on res_query on the concatenation of name and domain, 368 * removing a trailing dot from name if domain is NULL. 369 */ 370 int 371 res_nquerydomain(res_state statp, 372 const char *name, 373 const char *domain, 374 int class, int type, /*%< class and type of query */ 375 u_char *answer, /*%< buffer to put answer */ 376 int anslen) /*%< size of answer */ 377 { 378 char nbuf[MAXDNAME]; 379 const char *longname = nbuf; 380 int n, d; 381 382 #ifdef DEBUG 383 if (statp->options & RES_DEBUG) 384 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 385 name, domain?domain:"<Nil>", class, type); 386 #endif 387 if (domain == NULL) { 388 /* 389 * Check for trailing '.'; 390 * copy without '.' if present. 391 */ 392 n = strlen(name); 393 if (n >= MAXDNAME) { 394 RES_SET_H_ERRNO(statp, NO_RECOVERY); 395 return (-1); 396 } 397 n--; 398 if (n >= 0 && name[n] == '.') { 399 strncpy(nbuf, name, (size_t)n); 400 nbuf[n] = '\0'; 401 } else 402 longname = name; 403 } else { 404 n = strlen(name); 405 d = strlen(domain); 406 if (n + d + 1 >= MAXDNAME) { 407 RES_SET_H_ERRNO(statp, NO_RECOVERY); 408 return (-1); 409 } 410 sprintf(nbuf, "%s.%s", name, domain); 411 } 412 return (res_nquery(statp, longname, class, type, answer, anslen)); 413 } 414 415 const char * 416 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 417 char *file, *cp1, *cp2; 418 char buf[BUFSIZ]; 419 FILE *fp; 420 421 if (statp->options & RES_NOALIASES) 422 return (NULL); 423 /* 424 * forbid hostaliases for setuid binary, due to possible security 425 * breach. 426 */ 427 if (issetugid()) 428 return (NULL); 429 file = getenv("HOSTALIASES"); 430 if (file == NULL || (fp = fopen(file, "r")) == NULL) 431 return (NULL); 432 setbuf(fp, NULL); 433 buf[sizeof(buf) - 1] = '\0'; 434 while (fgets(buf, sizeof(buf), fp)) { 435 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 436 ; 437 if (!*cp1) 438 break; 439 *cp1 = '\0'; 440 if (ns_samename(buf, name) == 1) { 441 while (isspace((unsigned char)*++cp1)) 442 ; 443 if (!*cp1) 444 break; 445 for (cp2 = cp1 + 1; *cp2 && 446 !isspace((unsigned char)*cp2); ++cp2) 447 ; 448 *cp2 = '\0'; 449 strncpy(dst, cp1, siz - 1); 450 dst[siz - 1] = '\0'; 451 fclose(fp); 452 return (dst); 453 } 454 } 455 fclose(fp); 456 return (NULL); 457 } 458 459 /*! \file */ 460