resolv/res_init.c

   1 /* Resolver state initialization and resolv.conf parsing.
   2    Copyright (C) 1995-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 /*
  20  * Copyright (c) 1985, 1989, 1993
  21  *    The Regents of the University of California.  All rights reserved.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the above copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 4. Neither the name of the University nor the names of its contributors
  32  *    may be used to endorse or promote products derived from this software
  33  *    without specific prior written permission.
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  36  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  38  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  39  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  40  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  41  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  42  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  43  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  44  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  45  * SUCH DAMAGE.
  46  */
  47
  48 /*
  49  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  50  *
  51  * Permission to use, copy, modify, and distribute this software for any
  52  * purpose with or without fee is hereby granted, provided that the above
  53  * copyright notice and this permission notice appear in all copies, and that
  54  * the name of Digital Equipment Corporation not be used in advertising or
  55  * publicity pertaining to distribution of the document or software without
  56  * specific, written prior permission.
  57  *
  58  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  59  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  60  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  61  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  62  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  63  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  64  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  65  * SOFTWARE.
  66  */
  67
  68 /*
  69  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
  70  *
  71  * Permission to use, copy, modify, and distribute this software for any
  72  * purpose with or without fee is hereby granted, provided that the above
  73  * copyright notice and this permission notice appear in all copies.
  74  *
  75  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  76  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  77  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  78  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  79  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  80  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  81  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  82  * SOFTWARE.
  83  */
  84
  85 #include <ctype.h>
  86 #include <netdb.h>
  87 #include <resolv/resolv-internal.h>
  88 #include <res_hconf.h>
  89 #include <stdio.h>
  90 #include <stdio_ext.h>
  91 #include <stdlib.h>
  92 #include <string.h>
  93 #include <unistd.h>
  94 #include <stdint.h>
  95 #include <arpa/inet.h>
  96 #include <arpa/nameser.h>
  97 #include <net/if.h>
  98 #include <netinet/in.h>
  99 #include <sys/param.h>
 100 #include <sys/socket.h>
 101 #include <sys/time.h>
 102 #include <sys/types.h>
 103 #include <inet/net-internal.h>
 104 #include <errno.h>
 105
 106 static void res_setoptions (res_state, const char *);
 107 static uint32_t net_mask (struct in_addr);
 108
 109 unsigned long long int __res_initstamp;
 110
 111 int
 112 res_ninit (res_state statp)
 113 {
 114   return __res_vinit (statp, 0);
 115 }
 116 libc_hidden_def (__res_ninit)
 117
 118 /* Return true if CH separates the netmask in the "sortlist"
 119    directive.  */
 120 static inline bool
 121 is_sort_mask (char ch)
 122 {
 123   return ch == '/' || ch == '&';
 124 }
 125
 126 /* Internal helper function for __res_vinit, to aid with resource
 127    deallocation and error handling.  Return true on success, false on
 128    failure.  */
 129 static bool
 130 res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
 131 {
 132   char *cp, **pp;
 133   size_t buffer_size = 0;
 134   int nserv = 0;    /* Number of nameservers read from file.  */
 135   bool have_serv6 = false;
 136   bool haveenv = false;
 137   bool havesearch = false;
 138   int nsort = 0;
 139   char *net;
 140   statp->_u._ext.initstamp = __res_initstamp;
 141
 142   if (!preinit)
 143     {
 144       statp->retrans = RES_TIMEOUT;
 145       statp->retry = RES_DFLRETRY;
 146       statp->options = RES_DEFAULT;
 147       statp->id = res_randomid ();
 148     }
 149
 150   statp->nscount = 0;
 151   statp->defdname[0] = '\0';
 152   statp->ndots = 1;
 153   statp->pfcode = 0;
 154   statp->_vcsock = -1;
 155   statp->_flags = 0;
 156   statp->__glibc_unused_qhook = NULL;
 157   statp->__glibc_unused_rhook = NULL;
 158   statp->_u._ext.nscount = 0;
 159   for (int n = 0; n < MAXNS; n++)
 160     statp->_u._ext.nsaddrs[n] = NULL;
 161
 162   /* Allow user to override the local domain definition.  */
 163   if ((cp = getenv ("LOCALDOMAIN")) != NULL)
 164     {
 165       strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
 166       statp->defdname[sizeof (statp->defdname) - 1] = '\0';
 167       haveenv = true;
 168
 169       /* Set search list to be blank-separated strings from rest of
 170          env value.  Permits users of LOCALDOMAIN to still have a
 171          search list, and anyone to set the one that they want to use
 172          as an individual (even more important now that the rfc1535
 173          stuff restricts searches).  */
 174       cp = statp->defdname;
 175       pp = statp->dnsrch;
 176       *pp++ = cp;
 177       for (int n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++)
 178         {
 179           if (*cp == '\n')
 180             break;
 181           else if (*cp == ' ' || *cp == '\t')
 182             {
 183               *cp = 0;
 184               n = 1;
 185             }
 186           else if (n > 0)
 187             {
 188               *pp++ = cp;
 189               n = 0;
 190               havesearch = true;
 191             }
 192         }
 193       /* Null terminate last domain if there are excess.  */
 194       while (*cp != '\0' && *cp != ' ' && *cp != '\t' && *cp != '\n')
 195         cp++;
 196       *cp = '\0';
 197       *pp++ = 0;
 198     }
 199
 200 #define MATCH(line, name)                       \
 201   (!strncmp ((line), name, sizeof (name) - 1)     \
 202    && ((line)[sizeof (name) - 1] == ' '           \
 203        || (line)[sizeof (name) - 1] == '\t'))
 204
 205   if (fp != NULL)
 206     {
 207       /* No threads use this stream.  */
 208       __fsetlocking (fp, FSETLOCKING_BYCALLER);
 209       /* Read the config file.  */
 210       while (true)
 211         {
 212           {
 213             ssize_t ret = __getline (buffer, &buffer_size, fp);
 214             if (ret <= 0)
 215               {
 216                 if (_IO_ferror_unlocked (fp))
 217                   return false;
 218                 else
 219                   break;
 220               }
 221           }
 222
 223           /* Skip comments.  */
 224           if (**buffer == ';' || **buffer == '#')
 225             continue;
 226           /* Read default domain name.  */
 227           if (MATCH (*buffer, "domain"))
 228             {
 229               if (haveenv)
 230                 /* LOCALDOMAIN overrides the configuration file.  */
 231                 continue;
 232               cp = *buffer + sizeof ("domain") - 1;
 233               while (*cp == ' ' || *cp == '\t')
 234                 cp++;
 235               if ((*cp == '\0') || (*cp == '\n'))
 236                 continue;
 237               strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
 238               statp->defdname[sizeof (statp->defdname) - 1] = '\0';
 239               if ((cp = strpbrk (statp->defdname, " \t\n")) != NULL)
 240                 *cp = '\0';
 241               havesearch = false;
 242               continue;
 243             }
 244           /* Set search list.  */
 245           if (MATCH (*buffer, "search"))
 246             {
 247               if (haveenv)
 248                 /* LOCALDOMAIN overrides the configuration file.  */
 249                 continue;
 250               cp = *buffer + sizeof ("search") - 1;
 251               while (*cp == ' ' || *cp == '\t')
 252                 cp++;
 253               if ((*cp == '\0') || (*cp == '\n'))
 254                 continue;
 255               strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
 256               statp->defdname[sizeof (statp->defdname) - 1] = '\0';
 257               if ((cp = strchr (statp->defdname, '\n')) != NULL)
 258                 *cp = '\0';
 259               /* Set search list to be blank-separated strings on rest
 260                  of line.  */
 261               cp = statp->defdname;
 262               pp = statp->dnsrch;
 263               *pp++ = cp;
 264               for (int n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++)
 265                 {
 266                   if (*cp == ' ' || *cp == '\t')
 267                     {
 268                       *cp = 0;
 269                       n = 1;
 270                     }
 271                   else if (n)
 272                     {
 273                       *pp++ = cp;
 274                       n = 0;
 275                     }
 276                 }
 277               /* Null terminate last domain if there are excess.  */
 278               while (*cp != '\0' && *cp != ' ' && *cp != '\t')
 279                 cp++;
 280               *cp = '\0';
 281               *pp++ = 0;
 282               havesearch = true;
 283               continue;
 284             }
 285           /* Read nameservers to query.  */
 286           if (MATCH (*buffer, "nameserver") && nserv < MAXNS)
 287             {
 288               struct in_addr a;
 289
 290               cp = *buffer + sizeof ("nameserver") - 1;
 291               while (*cp == ' ' || *cp == '\t')
 292                 cp++;
 293               if ((*cp != '\0') && (*cp != '\n') && __inet_aton (cp, &a))
 294                 {
 295                   statp->nsaddr_list[nserv].sin_addr = a;
 296                   statp->nsaddr_list[nserv].sin_family = AF_INET;
 297                   statp->nsaddr_list[nserv].sin_port = htons (NAMESERVER_PORT);
 298                   nserv++;
 299                 }
 300               else
 301                 {
 302                   struct in6_addr a6;
 303                   char *el;
 304
 305                   if ((el = strpbrk (cp, " \t\n")) != NULL)
 306                     *el = '\0';
 307                   if ((el = strchr (cp, SCOPE_DELIMITER)) != NULL)
 308                     *el = '\0';
 309                   if ((*cp != '\0') && (__inet_pton (AF_INET6, cp, &a6) > 0))
 310                     {
 311                       struct sockaddr_in6 *sa6;
 312
 313                       sa6 = malloc (sizeof (*sa6));
 314                       if (sa6 == NULL)
 315                         return false;
 316
 317                       sa6->sin6_family = AF_INET6;
 318                       sa6->sin6_port = htons (NAMESERVER_PORT);
 319                       sa6->sin6_flowinfo = 0;
 320                       sa6->sin6_addr = a6;
 321
 322                       sa6->sin6_scope_id = 0;
 323                       if (__glibc_likely (el != NULL))
 324                         /* Ignore errors, for backwards
 325                            compatibility.  */
 326                         __inet6_scopeid_pton
 327                           (&a6, el + 1, &sa6->sin6_scope_id);
 328
 329                       statp->nsaddr_list[nserv].sin_family = 0;
 330                       statp->_u._ext.nsaddrs[nserv] = sa6;
 331                       statp->_u._ext.nssocks[nserv] = -1;
 332                       have_serv6 = true;
 333                       nserv++;
 334                     }
 335                 }
 336               continue;
 337             }
 338           if (MATCH (*buffer, "sortlist"))
 339             {
 340               struct in_addr a;
 341
 342               cp = *buffer + sizeof ("sortlist") - 1;
 343               while (nsort < MAXRESOLVSORT)
 344                 {
 345                   while (*cp == ' ' || *cp == '\t')
 346                     cp++;
 347                   if (*cp == '\0' || *cp == '\n' || *cp == ';')
 348                     break;
 349                   net = cp;
 350                   while (*cp && !is_sort_mask (*cp) && *cp != ';'
 351                          && isascii (*cp) && !isspace (*cp))
 352                     cp++;
 353                   char separator = *cp;
 354                   *cp = 0;
 355                   if (__inet_aton (net, &a))
 356                     {
 357                       statp->sort_list[nsort].addr = a;
 358                       if (is_sort_mask (separator))
 359                         {
 360                           *cp++ = separator;
 361                           net = cp;
 362                           while (*cp && *cp != ';'
 363                                  && isascii (*cp) && !isspace (*cp))
 364                             cp++;
 365                           separator = *cp;
 366                           *cp = 0;
 367                           if (__inet_aton (net, &a))
 368                             statp->sort_list[nsort].mask = a.s_addr;
 369                           else
 370                             statp->sort_list[nsort].mask
 371                               = net_mask (statp->sort_list[nsort].addr);
 372                         }
 373                       else
 374                         statp->sort_list[nsort].mask
 375                           = net_mask (statp->sort_list[nsort].addr);
 376                       nsort++;
 377                     }
 378                   *cp = separator;
 379                 }
 380               continue;
 381             }
 382           if (MATCH (*buffer, "options"))
 383             {
 384               res_setoptions (statp, *buffer + sizeof ("options") - 1);
 385               continue;
 386             }
 387         }
 388       statp->nscount = nserv;
 389       if (have_serv6)
 390         /* We try IPv6 servers again.  */
 391         statp->ipv6_unavail = false;
 392       statp->nsort = nsort;
 393       fclose (fp);
 394     }
 395   if (__glibc_unlikely (statp->nscount == 0))
 396     {
 397       statp->nsaddr.sin_addr = __inet_makeaddr (IN_LOOPBACKNET, 1);
 398       statp->nsaddr.sin_family = AF_INET;
 399       statp->nsaddr.sin_port = htons (NAMESERVER_PORT);
 400       statp->nscount = 1;
 401     }
 402   if (statp->defdname[0] == 0)
 403     {
 404       char buf[sizeof (statp->defdname)];
 405       if (__gethostname (buf, sizeof (statp->defdname) - 1) == 0
 406           && (cp = strchr (buf, '.')) != NULL)
 407         strcpy (statp->defdname, cp + 1);
 408     }
 409
 410   /* Find components of local domain that might be searched.  */
 411   if (!havesearch)
 412     {
 413       pp = statp->dnsrch;
 414       *pp++ = statp->defdname;
 415       *pp = NULL;
 416
 417     }
 418
 419   if ((cp = getenv ("RES_OPTIONS")) != NULL)
 420     res_setoptions (statp, cp);
 421   statp->options |= RES_INIT;
 422   return true;
 423 }
 424
 425 /* Set up default settings.  If the /etc/resolv.conf configuration
 426    file exist, the values there will have precedence.  Otherwise, the
 427    server address is set to INADDR_LOOPBACK and the default domain
 428    name comes from gethostname.  The RES_OPTIONS and LOCALDOMAIN
 429    environment variables can be used to override some settings.
 430    Return 0 if completes successfully, -1 on error.  */
 431 int
 432 __res_vinit (res_state statp, int preinit)
 433 {
 434   /* Ensure that /etc/hosts.conf has been loaded (once).  */
 435   _res_hconf_init ();
 436
 437   FILE *fp = fopen (_PATH_RESCONF, "rce");
 438   if (fp == NULL)
 439     switch (errno)
 440       {
 441       case EACCES:
 442       case EISDIR:
 443       case ELOOP:
 444       case ENOENT:
 445       case ENOTDIR:
 446       case EPERM:
 447         /* Ignore these errors.  They are persistent errors caused
 448            by file system contents.  */
 449         break;
 450       default:
 451         /* Other errors refer to resource allocation problems and
 452            need to be handled by the application.  */
 453         return -1;
 454       }
 455
 456   char *buffer = NULL;
 457   bool ok = res_vinit_1 (statp, preinit, fp, &buffer);
 458   free (buffer);
 459
 460   if (!ok)
 461     {
 462       /* Deallocate the name server addresses which have been
 463          allocated.  */
 464       for (int n = 0; n < MAXNS; n++)
 465         free (statp->_u._ext.nsaddrs[n]);
 466       return -1;
 467     }
 468   return 0;
 469 }
 470
 471 static void
 472 res_setoptions (res_state statp, const char *options)
 473 {
 474   const char *cp = options;
 475
 476   while (*cp)
 477     {
 478       /* Skip leading and inner runs of spaces.  */
 479       while (*cp == ' ' || *cp == '\t')
 480         cp++;
 481       /* Search for and process individual options.  */
 482       if (!strncmp (cp, "ndots:", sizeof ("ndots:") - 1))
 483         {
 484           int i = atoi (cp + sizeof ("ndots:") - 1);
 485           if (i <= RES_MAXNDOTS)
 486             statp->ndots = i;
 487           else
 488             statp->ndots = RES_MAXNDOTS;
 489         }
 490       else if (!strncmp (cp, "timeout:", sizeof ("timeout:") - 1))
 491         {
 492           int i = atoi (cp + sizeof ("timeout:") - 1);
 493           if (i <= RES_MAXRETRANS)
 494             statp->retrans = i;
 495           else
 496             statp->retrans = RES_MAXRETRANS;
 497         }
 498       else if (!strncmp (cp, "attempts:", sizeof ("attempts:") - 1))
 499         {
 500           int i = atoi (cp + sizeof ("attempts:") - 1);
 501           if (i <= RES_MAXRETRY)
 502             statp->retry = i;
 503           else
 504             statp->retry = RES_MAXRETRY;
 505         }
 506       else
 507         {
 508           static const struct
 509           {
 510             char str[22];
 511             uint8_t len;
 512             uint8_t clear;
 513             unsigned long int flag;
 514           } options[] = {
 515 #define STRnLEN(str) str, sizeof (str) - 1
 516             { STRnLEN ("inet6"), 0, DEPRECATED_RES_USE_INET6 },
 517             { STRnLEN ("rotate"), 0, RES_ROTATE },
 518             { STRnLEN ("edns0"), 0, RES_USE_EDNS0 },
 519             { STRnLEN ("single-request-reopen"), 0, RES_SNGLKUPREOP },
 520             { STRnLEN ("single-request"), 0, RES_SNGLKUP },
 521             { STRnLEN ("no_tld_query"), 0, RES_NOTLDQUERY },
 522             { STRnLEN ("no-tld-query"), 0, RES_NOTLDQUERY },
 523             { STRnLEN ("use-vc"), 0, RES_USEVC }
 524           };
 525 #define noptions (sizeof (options) / sizeof (options[0]))
 526           for (int i = 0; i < noptions; ++i)
 527             if (strncmp (cp, options[i].str, options[i].len) == 0)
 528               {
 529                 if (options[i].clear)
 530                   statp->options &= options[i].flag;
 531                 else
 532                   statp->options |= options[i].flag;
 533                 break;
 534               }
 535         }
 536       /* Skip to next run of spaces.  */
 537       while (*cp && *cp != ' ' && *cp != '\t')
 538         cp++;
 539     }
 540 }
 541
 542 static uint32_t
 543 net_mask (struct in_addr in)
 544 {
 545   uint32_t i = ntohl (in.s_addr);
 546
 547   if (IN_CLASSA (i))
 548     return htonl (IN_CLASSA_NET);
 549   else if (IN_CLASSB (i))
 550     return htonl (IN_CLASSB_NET);
 551   return htonl (IN_CLASSC_NET);
 552 }