1 /* 2 * Copyright (c) 1988, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Portions Copyright (c) 1993 by Digital Equipment Corporation. 36 * 37 * Permission to use, copy, modify, and distribute this software for any 38 * purpose with or without fee is hereby granted, provided that the above 39 * copyright notice and this permission notice appear in all copies, and that 40 * the name of Digital Equipment Corporation not be used in advertising or 41 * publicity pertaining to distribution of the document or software without 42 * specific, written prior permission. 43 * 44 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL 45 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES 46 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT 47 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 48 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 49 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 50 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 51 * SOFTWARE. 52 */ 53 54 /* 55 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 56 * Portions Copyright (c) 1996-1999 by Internet Software Consortium. 57 * 58 * Permission to use, copy, modify, and distribute this software for any 59 * purpose with or without fee is hereby granted, provided that the above 60 * copyright notice and this permission notice appear in all copies. 61 * 62 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 63 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 64 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 65 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 66 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 67 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 68 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 69 */ 70 71 #if defined(LIBC_SCCS) && !defined(lint) 72 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; 73 static const char rcsid[] = "$Id: res_query.c,v 1.2.2.3.4.2 2004/03/16 12:34:19 marka Exp $"; 74 #endif /* LIBC_SCCS and not lint */ 75 #include <sys/cdefs.h> 76 __FBSDID("$FreeBSD$"); 77 78 #include "port_before.h" 79 #include <sys/types.h> 80 #include <sys/param.h> 81 #include <netinet/in.h> 82 #include <arpa/inet.h> 83 #include <arpa/nameser.h> 84 #include <ctype.h> 85 #include <errno.h> 86 #include <netdb.h> 87 #include <resolv.h> 88 #include <stdio.h> 89 #include <stdlib.h> 90 #include <string.h> 91 #include <unistd.h> 92 #include "port_after.h" 93 94 /* Options. Leave them on. */ 95 #define DEBUG 96 97 #if PACKETSZ > 1024 98 #define MAXPACKET PACKETSZ 99 #else 100 #define MAXPACKET 1024 101 #endif 102 103 /* 104 * Formulate a normal query, send, and await answer. 105 * Returned answer is placed in supplied buffer "answer". 106 * Perform preliminary check of answer, returning success only 107 * if no error is indicated and the answer count is nonzero. 108 * Return the size of the response on success, -1 on error. 109 * Error number is left in H_ERRNO. 110 * 111 * Caller must parse answer and determine whether it answers the question. 112 */ 113 int 114 res_nquery(res_state statp, 115 const char *name, /* domain name */ 116 int class, int type, /* class and type of query */ 117 u_char *answer, /* buffer to put answer */ 118 int anslen) /* size of answer buffer */ 119 { 120 u_char buf[MAXPACKET]; 121 HEADER *hp = (HEADER *) answer; 122 int n; 123 u_int oflags; 124 125 oflags = statp->_flags; 126 127 again: 128 hp->rcode = NOERROR; /* default */ 129 130 #ifdef DEBUG 131 if (statp->options & RES_DEBUG) 132 printf(";; res_query(%s, %d, %d)\n", name, class, type); 133 #endif 134 135 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 136 buf, sizeof(buf)); 137 #ifdef RES_USE_EDNS0 138 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 139 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U) 140 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 141 #endif 142 if (n <= 0) { 143 #ifdef DEBUG 144 if (statp->options & RES_DEBUG) 145 printf(";; res_query: mkquery failed\n"); 146 #endif 147 RES_SET_H_ERRNO(statp, NO_RECOVERY); 148 return (n); 149 } 150 n = res_nsend(statp, buf, n, answer, anslen); 151 if (n < 0) { 152 #ifdef RES_USE_EDNS0 153 /* if the query choked with EDNS0, retry without EDNS0 */ 154 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 155 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 156 statp->_flags |= RES_F_EDNS0ERR; 157 if (statp->options & RES_DEBUG) 158 printf(";; res_nquery: retry without EDNS0\n"); 159 goto again; 160 } 161 #endif 162 #ifdef DEBUG 163 if (statp->options & RES_DEBUG) 164 printf(";; res_query: send error\n"); 165 #endif 166 RES_SET_H_ERRNO(statp, TRY_AGAIN); 167 return (n); 168 } 169 170 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 171 #ifdef DEBUG 172 if (statp->options & RES_DEBUG) 173 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 174 p_rcode(hp->rcode), 175 ntohs(hp->ancount), 176 ntohs(hp->nscount), 177 ntohs(hp->arcount)); 178 #endif 179 switch (hp->rcode) { 180 case NXDOMAIN: 181 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 182 break; 183 case SERVFAIL: 184 RES_SET_H_ERRNO(statp, TRY_AGAIN); 185 break; 186 case NOERROR: 187 RES_SET_H_ERRNO(statp, NO_DATA); 188 break; 189 case FORMERR: 190 case NOTIMP: 191 case REFUSED: 192 default: 193 RES_SET_H_ERRNO(statp, NO_RECOVERY); 194 break; 195 } 196 return (-1); 197 } 198 return (n); 199 } 200 201 /* 202 * Formulate a normal query, send, and retrieve answer in supplied buffer. 203 * Return the size of the response on success, -1 on error. 204 * If enabled, implement search rules until answer or unrecoverable failure 205 * is detected. Error code, if any, is left in H_ERRNO. 206 */ 207 int 208 res_nsearch(res_state statp, 209 const char *name, /* domain name */ 210 int class, int type, /* class and type of query */ 211 u_char *answer, /* buffer to put answer */ 212 int anslen) /* size of answer */ 213 { 214 const char *cp, * const *domain; 215 HEADER *hp = (HEADER *) answer; 216 char tmp[NS_MAXDNAME]; 217 u_int dots; 218 int trailing_dot, ret, saved_herrno; 219 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 220 int tried_as_is = 0; 221 int searched = 0; 222 223 errno = 0; 224 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /* True if we never query. */ 225 226 dots = 0; 227 for (cp = name; *cp != '\0'; cp++) 228 dots += (*cp == '.'); 229 trailing_dot = 0; 230 if (cp > name && *--cp == '.') 231 trailing_dot++; 232 233 /* If there aren't any dots, it could be a user-level alias. */ 234 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 235 return (res_nquery(statp, cp, class, type, answer, anslen)); 236 237 /* 238 * If there are enough dots in the name, let's just give it a 239 * try 'as is'. The threshold can be set with the "ndots" option. 240 * Also, query 'as is', if there is a trailing dot in the name. 241 */ 242 saved_herrno = -1; 243 if (dots >= statp->ndots || trailing_dot) { 244 ret = res_nquerydomain(statp, name, NULL, class, type, 245 answer, anslen); 246 if (ret > 0 || trailing_dot) 247 return (ret); 248 if (errno == ECONNREFUSED) { 249 RES_SET_H_ERRNO(statp, TRY_AGAIN); 250 return (-1); 251 } 252 switch (statp->res_h_errno) { 253 case NO_DATA: 254 case HOST_NOT_FOUND: 255 break; 256 case TRY_AGAIN: 257 if (hp->rcode == SERVFAIL) 258 break; 259 /* FALLTHROUGH */ 260 default: 261 return (-1); 262 } 263 saved_herrno = statp->res_h_errno; 264 tried_as_is++; 265 } 266 267 /* 268 * We do at least one level of search if 269 * - there is no dot and RES_DEFNAME is set, or 270 * - there is at least one dot, there is no trailing dot, 271 * and RES_DNSRCH is set. 272 */ 273 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 274 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 275 int done = 0; 276 277 for (domain = (const char * const *)statp->dnsrch; 278 *domain && !done; 279 domain++) { 280 searched = 1; 281 282 if (domain[0][0] == '\0' || 283 (domain[0][0] == '.' && domain[0][1] == '\0')) 284 root_on_list++; 285 286 if (root_on_list && tried_as_is) 287 continue; 288 289 ret = res_nquerydomain(statp, name, *domain, 290 class, type, 291 answer, anslen); 292 if (ret > 0) 293 return (ret); 294 295 /* 296 * If no server present, give up. 297 * If name isn't found in this domain, 298 * keep trying higher domains in the search list 299 * (if that's enabled). 300 * On a NO_DATA error, keep trying, otherwise 301 * a wildcard entry of another type could keep us 302 * from finding this entry higher in the domain. 303 * If we get some other error (negative answer or 304 * server failure), then stop searching up, 305 * but try the input name below in case it's 306 * fully-qualified. 307 */ 308 if (errno == ECONNREFUSED) { 309 RES_SET_H_ERRNO(statp, TRY_AGAIN); 310 return (-1); 311 } 312 313 switch (statp->res_h_errno) { 314 case NO_DATA: 315 got_nodata++; 316 /* FALLTHROUGH */ 317 case HOST_NOT_FOUND: 318 /* keep trying */ 319 break; 320 case TRY_AGAIN: 321 /* 322 * This can occur due to a server failure 323 * (that is, all listed servers have failed), 324 * or all listed servers have timed out. 325 * ((HEADER *)answer)->rcode may not be set 326 * to SERVFAIL in the case of a timeout. 327 * 328 * Either way we must return TRY_AGAIN in 329 * order to avoid non-deterministic 330 * return codes. 331 * For example, loaded name servers or races 332 * against network startup/validation (dhcp, 333 * ppp, etc) can cause the search to timeout 334 * on one search element, e.g. 'fu.bar.com', 335 * and return a definitive failure on the 336 * next search element, e.g. 'fu.'. 337 */ 338 got_servfail++; 339 if (hp->rcode == SERVFAIL) { 340 /* try next search element, if any */ 341 break; 342 } 343 /* FALLTHROUGH */ 344 default: 345 /* anything else implies that we're done */ 346 done++; 347 } 348 349 /* if we got here for some reason other than DNSRCH, 350 * we only wanted one iteration of the loop, so stop. 351 */ 352 if ((statp->options & RES_DNSRCH) == 0U) 353 done++; 354 } 355 } 356 357 switch (statp->res_h_errno) { 358 case NO_DATA: 359 case HOST_NOT_FOUND: 360 break; 361 case TRY_AGAIN: 362 if (hp->rcode == SERVFAIL) 363 break; 364 /* FALLTHROUGH */ 365 default: 366 goto giveup; 367 } 368 369 /* 370 * If the query has not already been tried as is then try it 371 * unless RES_NOTLDQUERY is set and there were no dots. 372 */ 373 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 374 !(tried_as_is || root_on_list)) { 375 ret = res_nquerydomain(statp, name, NULL, class, type, 376 answer, anslen); 377 if (ret > 0) 378 return (ret); 379 } 380 381 /* if we got here, we didn't satisfy the search. 382 * if we did an initial full query, return that query's H_ERRNO 383 * (note that we wouldn't be here if that query had succeeded). 384 * else if we ever got a nodata, send that back as the reason. 385 * else send back meaningless H_ERRNO, that being the one from 386 * the last DNSRCH we did. 387 */ 388 giveup: 389 if (saved_herrno != -1) 390 RES_SET_H_ERRNO(statp, saved_herrno); 391 else if (got_nodata) 392 RES_SET_H_ERRNO(statp, NO_DATA); 393 else if (got_servfail) 394 RES_SET_H_ERRNO(statp, TRY_AGAIN); 395 return (-1); 396 } 397 398 /* 399 * Perform a call on res_query on the concatenation of name and domain, 400 * removing a trailing dot from name if domain is NULL. 401 */ 402 int 403 res_nquerydomain(res_state statp, 404 const char *name, 405 const char *domain, 406 int class, int type, /* class and type of query */ 407 u_char *answer, /* buffer to put answer */ 408 int anslen) /* size of answer */ 409 { 410 char nbuf[MAXDNAME]; 411 const char *longname = nbuf; 412 int n, d; 413 414 #ifdef DEBUG 415 if (statp->options & RES_DEBUG) 416 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 417 name, domain?domain:"<Nil>", class, type); 418 #endif 419 if (domain == NULL) { 420 /* 421 * Check for trailing '.'; 422 * copy without '.' if present. 423 */ 424 n = strlen(name); 425 if (n >= MAXDNAME) { 426 RES_SET_H_ERRNO(statp, NO_RECOVERY); 427 return (-1); 428 } 429 n--; 430 if (n >= 0 && name[n] == '.') { 431 strncpy(nbuf, name, n); 432 nbuf[n] = '\0'; 433 } else 434 longname = name; 435 } else { 436 n = strlen(name); 437 d = strlen(domain); 438 if (n + d + 1 >= MAXDNAME) { 439 RES_SET_H_ERRNO(statp, NO_RECOVERY); 440 return (-1); 441 } 442 sprintf(nbuf, "%s.%s", name, domain); 443 } 444 return (res_nquery(statp, longname, class, type, answer, anslen)); 445 } 446 447 const char * 448 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 449 char *file, *cp1, *cp2; 450 char buf[BUFSIZ]; 451 FILE *fp; 452 453 if (statp->options & RES_NOALIASES) 454 return (NULL); 455 if (issetugid()) 456 return (NULL); 457 file = getenv("HOSTALIASES"); 458 if (file == NULL || (fp = fopen(file, "r")) == NULL) 459 return (NULL); 460 setbuf(fp, NULL); 461 buf[sizeof(buf) - 1] = '\0'; 462 while (fgets(buf, sizeof(buf), fp)) { 463 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 464 ; 465 if (!*cp1) 466 break; 467 *cp1 = '\0'; 468 if (ns_samename(buf, name) == 1) { 469 while (isspace((unsigned char)*++cp1)) 470 ; 471 if (!*cp1) 472 break; 473 for (cp2 = cp1 + 1; *cp2 && 474 !isspace((unsigned char)*cp2); ++cp2) 475 ; 476 *cp2 = '\0'; 477 strncpy(dst, cp1, siz - 1); 478 dst[siz - 1] = '\0'; 479 fclose(fp); 480 return (dst); 481 } 482 } 483 fclose(fp); 484 return (NULL); 485 } 486