lib/libc/resolv/res_query.c

   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 1.8.672.2 2008/04/03 10:49:22 marka Exp $";
  74 #endif /* LIBC_SCCS and not lint */
  75
  76 #include "port_before.h"
  77 #include <sys/types.h>
  78 #include <sys/param.h>
  79 #include <netinet/in.h>
  80 #include <arpa/inet.h>
  81 #include <arpa/nameser.h>
  82 #include <ctype.h>
  83 #include <errno.h>
  84 #include <netdb.h>
  85 #include <resolv.h>
  86 #include <stdio.h>
  87 #include <stdlib.h>
  88 #include <string.h>
  89 #include "port_after.h"
  90
  91 /* Options.  Leave them on. */
  92 #define DEBUG
  93
  94 #if PACKETSZ > 1024
  95 #define MAXPACKET       PACKETSZ
  96 #else
  97 #define MAXPACKET       1024
  98 #endif
  99
 100 /*%
 101  * Formulate a normal query, send, and await answer.
 102  * Returned answer is placed in supplied buffer "answer".
 103  * Perform preliminary check of answer, returning success only
 104  * if no error is indicated and the answer count is nonzero.
 105  * Return the size of the response on success, -1 on error.
 106  * Error number is left in H_ERRNO.
 107  *
 108  * Caller must parse answer and determine whether it answers the question.
 109  */
 110 int
 111 res_nquery(res_state statp,
 112            const char *name,    /*%< domain name */
 113            int class, int type, /*%< class and type of query */
 114            u_char *answer,      /*%< buffer to put answer */
 115            int anslen)          /*%< size of answer buffer */
 116 {
 117         u_char buf[MAXPACKET];
 118         HEADER *hp = (HEADER *) answer;
 119         u_int oflags;
 120         u_char *rdata;
 121         int n;
 122
 123         oflags = statp->_flags;
 124
 125 again:
 126         hp->rcode = NOERROR;    /*%< default */
 127 #ifdef DEBUG
 128         if (statp->options & RES_DEBUG)
 129                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 130 #endif
 131
 132         n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
 133                          buf, sizeof(buf));
 134 #ifdef RES_USE_EDNS0
 135         if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
 136             (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
 137                 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
 138                 rdata = &buf[n];
 139                 if (n > 0 && (statp->options & RES_NSID) != 0U) {
 140                         n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
 141                                            NS_OPT_NSID, 0, NULL);
 142                 }
 143         }
 144 #endif
 145         if (n <= 0) {
 146 #ifdef DEBUG
 147                 if (statp->options & RES_DEBUG)
 148                         printf(";; res_query: mkquery failed\n");
 149 #endif
 150                 RES_SET_H_ERRNO(statp, NO_RECOVERY);
 151                 return (n);
 152         }
 153
 154         n = res_nsend(statp, buf, n, answer, anslen);
 155         if (n < 0) {
 156 #ifdef RES_USE_EDNS0
 157                 /* if the query choked with EDNS0, retry without EDNS0 */
 158                 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
 159                     ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
 160                         statp->_flags |= RES_F_EDNS0ERR;
 161                         if (statp->options & RES_DEBUG)
 162                                 printf(";; res_nquery: retry without EDNS0\n");
 163                         goto again;
 164                 }
 165 #endif
 166 #ifdef DEBUG
 167                 if (statp->options & RES_DEBUG)
 168                         printf(";; res_query: send error\n");
 169 #endif
 170                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 171                 return (n);
 172         }
 173
 174         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 175 #ifdef DEBUG
 176                 if (statp->options & RES_DEBUG)
 177                         printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
 178                                p_rcode(hp->rcode),
 179                                ntohs(hp->ancount),
 180                                ntohs(hp->nscount),
 181                                ntohs(hp->arcount));
 182 #endif
 183                 switch (hp->rcode) {
 184                 case NXDOMAIN:
 185                         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
 186                         break;
 187                 case SERVFAIL:
 188                         RES_SET_H_ERRNO(statp, TRY_AGAIN);
 189                         break;
 190                 case NOERROR:
 191                         RES_SET_H_ERRNO(statp, NO_DATA);
 192                         break;
 193                 case FORMERR:
 194                 case NOTIMP:
 195                 case REFUSED:
 196                 default:
 197                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 198                         break;
 199                 }
 200                 return (-1);
 201         }
 202         return (n);
 203 }
 204
 205 /*%
 206  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 207  * Return the size of the response on success, -1 on error.
 208  * If enabled, implement search rules until answer or unrecoverable failure
 209  * is detected.  Error code, if any, is left in H_ERRNO.
 210  */
 211 int
 212 res_nsearch(res_state statp,
 213             const char *name,   /*%< domain name */
 214             int class, int type,        /*%< class and type of query */
 215             u_char *answer,     /*%< buffer to put answer */
 216             int anslen)         /*%< size of answer */
 217 {
 218         const char *cp, * const *domain;
 219         HEADER *hp = (HEADER *) answer;
 220         char tmp[NS_MAXDNAME];
 221         u_int dots;
 222         int trailing_dot, ret, saved_herrno;
 223         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 224         int tried_as_is = 0;
 225         int searched = 0;
 226
 227         errno = 0;
 228         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /*%< True if we never query. */
 229         dots = 0;
 230         for (cp = name; *cp != '\0'; cp++)
 231                 dots += (*cp == '.');
 232         trailing_dot = 0;
 233         if (cp > name && *--cp == '.')
 234                 trailing_dot++;
 235
 236         /* If there aren't any dots, it could be a user-level alias. */
 237         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 238                 return (res_nquery(statp, cp, class, type, answer, anslen));
 239
 240         /*
 241          * If there are enough dots in the name, let's just give it a
 242          * try 'as is'. The threshold can be set with the "ndots" option.
 243          * Also, query 'as is', if there is a trailing dot in the name.
 244          */
 245         saved_herrno = -1;
 246         if (dots >= statp->ndots || trailing_dot) {
 247                 ret = res_nquerydomain(statp, name, NULL, class, type,
 248                                          answer, anslen);
 249                 if (ret > 0 || trailing_dot)
 250                         return (ret);
 251                 saved_herrno = statp->res_h_errno;
 252                 tried_as_is++;
 253         }
 254
 255         /*
 256          * We do at least one level of search if
 257          *      - there is no dot and RES_DEFNAME is set, or
 258          *      - there is at least one dot, there is no trailing dot,
 259          *        and RES_DNSRCH is set.
 260          */
 261         if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
 262             (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
 263                 int done = 0;
 264
 265                 for (domain = (const char * const *)statp->dnsrch;
 266                      *domain && !done;
 267                      domain++) {
 268                         searched = 1;
 269
 270                         if (domain[0][0] == '\0' ||
 271                             (domain[0][0] == '.' && domain[0][1] == '\0'))
 272                                 root_on_list++;
 273
 274                         ret = res_nquerydomain(statp, name, *domain,
 275                                                class, type,
 276                                                answer, anslen);
 277                         if (ret > 0)
 278                                 return (ret);
 279
 280                         /*
 281                          * If no server present, give up.
 282                          * If name isn't found in this domain,
 283                          * keep trying higher domains in the search list
 284                          * (if that's enabled).
 285                          * On a NO_DATA error, keep trying, otherwise
 286                          * a wildcard entry of another type could keep us
 287                          * from finding this entry higher in the domain.
 288                          * If we get some other error (negative answer or
 289                          * server failure), then stop searching up,
 290                          * but try the input name below in case it's
 291                          * fully-qualified.
 292                          */
 293                         if (errno == ECONNREFUSED) {
 294                                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 295                                 return (-1);
 296                         }
 297
 298                         switch (statp->res_h_errno) {
 299                         case NO_DATA:
 300                                 got_nodata++;
 301                                 /* FALLTHROUGH */
 302                         case HOST_NOT_FOUND:
 303                                 /* keep trying */
 304                                 break;
 305                         case TRY_AGAIN:
 306                                 if (hp->rcode == SERVFAIL) {
 307                                         /* try next search element, if any */
 308                                         got_servfail++;
 309                                         break;
 310                                 }
 311                                 /* FALLTHROUGH */
 312                         default:
 313                                 /* anything else implies that we're done */
 314                                 done++;
 315                         }
 316
 317                         /* if we got here for some reason other than DNSRCH,
 318                          * we only wanted one iteration of the loop, so stop.
 319                          */
 320                         if ((statp->options & RES_DNSRCH) == 0U)
 321                                 done++;
 322                 }
 323         }
 324
 325         /*
 326          * If the query has not already been tried as is then try it
 327          * unless RES_NOTLDQUERY is set and there were no dots.
 328          */
 329         if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
 330             !(tried_as_is || root_on_list)) {
 331                 ret = res_nquerydomain(statp, name, NULL, class, type,
 332                                        answer, anslen);
 333                 if (ret > 0)
 334                         return (ret);
 335         }
 336
 337         /* if we got here, we didn't satisfy the search.
 338          * if we did an initial full query, return that query's H_ERRNO
 339          * (note that we wouldn't be here if that query had succeeded).
 340          * else if we ever got a nodata, send that back as the reason.
 341          * else send back meaningless H_ERRNO, that being the one from
 342          * the last DNSRCH we did.
 343          */
 344         if (saved_herrno != -1)
 345                 RES_SET_H_ERRNO(statp, saved_herrno);
 346         else if (got_nodata)
 347                 RES_SET_H_ERRNO(statp, NO_DATA);
 348         else if (got_servfail)
 349                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 350         return (-1);
 351 }
 352
 353 /*%
 354  * Perform a call on res_query on the concatenation of name and domain,
 355  * removing a trailing dot from name if domain is NULL.
 356  */
 357 int
 358 res_nquerydomain(res_state statp,
 359             const char *name,
 360             const char *domain,
 361             int class, int type,        /*%< class and type of query */
 362             u_char *answer,             /*%< buffer to put answer */
 363             int anslen)         /*%< size of answer */
 364 {
 365         char nbuf[MAXDNAME];
 366         const char *longname = nbuf;
 367         int n, d;
 368
 369 #ifdef DEBUG
 370         if (statp->options & RES_DEBUG)
 371                 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
 372                        name, domain?domain:"<Nil>", class, type);
 373 #endif
 374         if (domain == NULL) {
 375                 /*
 376                  * Check for trailing '.';
 377                  * copy without '.' if present.
 378                  */
 379                 n = strlen(name);
 380                 if (n >= MAXDNAME) {
 381                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 382                         return (-1);
 383                 }
 384                 n--;
 385                 if (n >= 0 && name[n] == '.') {
 386                         strncpy(nbuf, name, n);
 387                         nbuf[n] = '\0';
 388                 } else
 389                         longname = name;
 390         } else {
 391                 n = strlen(name);
 392                 d = strlen(domain);
 393                 if (n + d + 1 >= MAXDNAME) {
 394                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 395                         return (-1);
 396                 }
 397                 sprintf(nbuf, "%s.%s", name, domain);
 398         }
 399         return (res_nquery(statp, longname, class, type, answer, anslen));
 400 }
 401
 402 const char *
 403 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
 404         char *file, *cp1, *cp2;
 405         char buf[BUFSIZ];
 406         FILE *fp;
 407
 408         if (statp->options & RES_NOALIASES)
 409                 return (NULL);
 410         file = getenv("HOSTALIASES");
 411         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 412                 return (NULL);
 413         setbuf(fp, NULL);
 414         buf[sizeof(buf) - 1] = '\0';
 415         while (fgets(buf, sizeof(buf), fp)) {
 416                 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
 417                         ;
 418                 if (!*cp1)
 419                         break;
 420                 *cp1 = '\0';
 421                 if (ns_samename(buf, name) == 1) {
 422                         while (isspace((unsigned char)*++cp1))
 423                                 ;
 424                         if (!*cp1)
 425                                 break;
 426                         for (cp2 = cp1 + 1; *cp2 &&
 427                              !isspace((unsigned char)*cp2); ++cp2)
 428                                 ;
 429                         *cp2 = '\0';
 430                         strncpy(dst, cp1, siz - 1);
 431                         dst[siz - 1] = '\0';
 432                         fclose(fp);
 433                         return (dst);
 434                 }
 435         }
 436         fclose(fp);
 437         return (NULL);
 438 }
 439
 440 /*! \file */