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 <stdio.h>
  89 #include <stdio_ext.h>
  90 #include <stdlib.h>
  91 #include <string.h>
  92 #include <unistd.h>
  93 #include <stdint.h>
  94 #include <arpa/inet.h>
  95 #include <arpa/nameser.h>
  96 #include <net/if.h>
  97 #include <netinet/in.h>
  98 #include <sys/param.h>
  99 #include <sys/socket.h>
 100 #include <sys/time.h>
 101 #include <sys/types.h>
 102 #include <inet/net-internal.h>
 103 #include <errno.h>
 104
 105 static void res_setoptions (res_state, const char *, const char *);
 106 static uint32_t net_mask (struct in_addr);
 107
 108 unsigned long long int __res_initstamp;
 109
 110 int
 111 res_ninit (res_state statp)
 112 {
 113   return __res_vinit (statp, 0);
 114 }
 115 libc_hidden_def (__res_ninit)
 116
 117 /* Return true if CH separates the netmask in the "sortlist"
 118    directive.  */
 119 static inline bool
 120 is_sort_mask (char ch)
 121 {
 122   return ch == '/' || ch == '&';
 123 }
 124
 125 /* Internal helper function for __res_vinit, to aid with resource
 126    deallocation and error handling.  Return true on success, false on
 127    failure.  */
 128 static bool
 129 res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
 130 {
 131   char *cp, **pp;
 132   size_t buffer_size = 0;
 133   int nserv = 0;    /* Number of nameservers read from file.  */
 134   bool have_serv6 = false;
 135   bool haveenv = false;
 136   bool havesearch = false;
 137   int nsort = 0;
 138   char *net;
 139   statp->_u._ext.initstamp = __res_initstamp;
 140
 141   if (!preinit)
 142     {
 143       statp->retrans = RES_TIMEOUT;
 144       statp->retry = RES_DFLRETRY;
 145       statp->options = RES_DEFAULT;
 146       statp->id = res_randomid ();
 147     }
 148
 149   statp->nscount = 0;
 150   statp->defdname[0] = '\0';
 151   statp->ndots = 1;
 152   statp->pfcode = 0;
 153   statp->_vcsock = -1;
 154   statp->_flags = 0;
 155   statp->__glibc_unused_qhook = NULL;
 156   statp->__glibc_unused_rhook = NULL;
 157   statp->_u._ext.nscount = 0;
 158   for (int n = 0; n < MAXNS; n++)
 159     statp->_u._ext.nsaddrs[n] = NULL;
 160
 161   /* Allow user to override the local domain definition.  */
 162   if ((cp = getenv ("LOCALDOMAIN")) != NULL)
 163     {
 164       strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
 165       statp->defdname[sizeof (statp->defdname) - 1] = '\0';
 166       haveenv = true;
 167
 168       /* Set search list to be blank-separated strings from rest of
 169          env value.  Permits users of LOCALDOMAIN to still have a
 170          search list, and anyone to set the one that they want to use
 171          as an individual (even more important now that the rfc1535
 172          stuff restricts searches).  */
 173       cp = statp->defdname;
 174       pp = statp->dnsrch;
 175       *pp++ = cp;
 176       for (int n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++)
 177         {
 178           if (*cp == '\n')
 179             break;
 180           else if (*cp == ' ' || *cp == '\t')
 181             {
 182               *cp = 0;
 183               n = 1;
 184             }
 185           else if (n > 0)
 186             {
 187               *pp++ = cp;
 188               n = 0;
 189               havesearch = true;
 190             }
 191         }
 192       /* Null terminate last domain if there are excess.  */
 193       while (*cp != '\0' && *cp != ' ' && *cp != '\t' && *cp != '\n')
 194         cp++;
 195       *cp = '\0';
 196       *pp++ = 0;
 197     }
 198
 199 #define MATCH(line, name)                       \
 200   (!strncmp ((line), name, sizeof (name) - 1)     \
 201    && ((line)[sizeof (name) - 1] == ' '           \
 202        || (line)[sizeof (name) - 1] == '\t'))
 203
 204   if (fp != NULL)
 205     {
 206       /* No threads use this stream.  */
 207       __fsetlocking (fp, FSETLOCKING_BYCALLER);
 208       /* Read the config file.  */
 209       while (true)
 210         {
 211           {
 212             ssize_t ret = __getline (buffer, &buffer_size, fp);
 213             if (ret <= 0)
 214               {
 215                 if (_IO_ferror_unlocked (fp))
 216                   return false;
 217                 else
 218                   break;
 219               }
 220           }
 221
 222           /* Skip comments.  */
 223           if (**buffer == ';' || **buffer == '#')
 224             continue;
 225           /* Read default domain name.  */
 226           if (MATCH (*buffer, "domain"))
 227             {
 228               if (haveenv)
 229                 /* LOCALDOMAIN overrides the configuration file.  */
 230                 continue;
 231               cp = *buffer + sizeof ("domain") - 1;
 232               while (*cp == ' ' || *cp == '\t')
 233                 cp++;
 234               if ((*cp == '\0') || (*cp == '\n'))
 235                 continue;
 236               strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
 237               statp->defdname[sizeof (statp->defdname) - 1] = '\0';
 238               if ((cp = strpbrk (statp->defdname, " \t\n")) != NULL)
 239                 *cp = '\0';
 240               havesearch = false;
 241               continue;
 242             }
 243           /* Set search list.  */
 244           if (MATCH (*buffer, "search"))
 245             {
 246               if (haveenv)
 247                 /* LOCALDOMAIN overrides the configuration file.  */
 248                 continue;
 249               cp = *buffer + sizeof ("search") - 1;
 250               while (*cp == ' ' || *cp == '\t')
 251                 cp++;
 252               if ((*cp == '\0') || (*cp == '\n'))
 253                 continue;
 254               strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
 255               statp->defdname[sizeof (statp->defdname) - 1] = '\0';
 256               if ((cp = strchr (statp->defdname, '\n')) != NULL)
 257                 *cp = '\0';
 258               /* Set search list to be blank-separated strings on rest
 259                  of line.  */
 260               cp = statp->defdname;
 261               pp = statp->dnsrch;
 262               *pp++ = cp;
 263               for (int n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++)
 264                 {
 265                   if (*cp == ' ' || *cp == '\t')
 266                     {
 267                       *cp = 0;
 268                       n = 1;
 269                     }
 270                   else if (n)
 271                     {
 272                       *pp++ = cp;
 273                       n = 0;
 274                     }
 275                 }
 276               /* Null terminate last domain if there are excess.  */
 277               while (*cp != '\0' && *cp != ' ' && *cp != '\t')
 278                 cp++;
 279               *cp = '\0';
 280               *pp++ = 0;
 281               havesearch = true;
 282               continue;
 283             }
 284           /* Read nameservers to query.  */
 285           if (MATCH (*buffer, "nameserver") && nserv < MAXNS)
 286             {
 287               struct in_addr a;
 288
 289               cp = *buffer + sizeof ("nameserver") - 1;
 290               while (*cp == ' ' || *cp == '\t')
 291                 cp++;
 292               if ((*cp != '\0') && (*cp != '\n') && __inet_aton (cp, &a))
 293                 {
 294                   statp->nsaddr_list[nserv].sin_addr = a;
 295                   statp->nsaddr_list[nserv].sin_family = AF_INET;
 296                   statp->nsaddr_list[nserv].sin_port = htons (NAMESERVER_PORT);
 297                   nserv++;
 298                 }
 299               else
 300                 {
 301                   struct in6_addr a6;
 302                   char *el;
 303
 304                   if ((el = strpbrk (cp, " \t\n")) != NULL)
 305                     *el = '\0';
 306                   if ((el = strchr (cp, SCOPE_DELIMITER)) != NULL)
 307                     *el = '\0';
 308                   if ((*cp != '\0') && (__inet_pton (AF_INET6, cp, &a6) > 0))
 309                     {
 310                       struct sockaddr_in6 *sa6;
 311
 312                       sa6 = malloc (sizeof (*sa6));
 313                       if (sa6 == NULL)
 314                         return false;
 315
 316                       sa6->sin6_family = AF_INET6;
 317                       sa6->sin6_port = htons (NAMESERVER_PORT);
 318                       sa6->sin6_flowinfo = 0;
 319                       sa6->sin6_addr = a6;
 320
 321                       sa6->sin6_scope_id = 0;
 322                       if (__glibc_likely (el != NULL))
 323                         /* Ignore errors, for backwards
 324                            compatibility.  */
 325                         __inet6_scopeid_pton
 326                           (&a6, el + 1, &sa6->sin6_scope_id);
 327
 328                       statp->nsaddr_list[nserv].sin_family = 0;
 329                       statp->_u._ext.nsaddrs[nserv] = sa6;
 330                       statp->_u._ext.nssocks[nserv] = -1;
 331                       have_serv6 = true;
 332                       nserv++;
 333                     }
 334                 }
 335               continue;
 336             }
 337           if (MATCH (*buffer, "sortlist"))
 338             {
 339               struct in_addr a;
 340
 341               cp = *buffer + sizeof ("sortlist") - 1;
 342               while (nsort < MAXRESOLVSORT)
 343                 {
 344                   while (*cp == ' ' || *cp == '\t')
 345                     cp++;
 346                   if (*cp == '\0' || *cp == '\n' || *cp == ';')
 347                     break;
 348                   net = cp;
 349                   while (*cp && !is_sort_mask (*cp) && *cp != ';'
 350                          && isascii (*cp) && !isspace (*cp))
 351                     cp++;
 352                   char separator = *cp;
 353                   *cp = 0;
 354                   if (__inet_aton (net, &a))
 355                     {
 356                       statp->sort_list[nsort].addr = a;
 357                       if (is_sort_mask (separator))
 358                         {
 359                           *cp++ = separator;
 360                           net = cp;
 361                           while (*cp && *cp != ';'
 362                                  && isascii (*cp) && !isspace (*cp))
 363                             cp++;
 364                           separator = *cp;
 365                           *cp = 0;
 366                           if (__inet_aton (net, &a))
 367                             statp->sort_list[nsort].mask = a.s_addr;
 368                           else
 369                             statp->sort_list[nsort].mask
 370                               = net_mask (statp->sort_list[nsort].addr);
 371                         }
 372                       else
 373                         statp->sort_list[nsort].mask
 374                           = net_mask (statp->sort_list[nsort].addr);
 375                       nsort++;
 376                     }
 377                   *cp = separator;
 378                 }
 379               continue;
 380             }
 381           if (MATCH (*buffer, "options"))
 382             {
 383               res_setoptions (statp, *buffer + sizeof ("options") - 1, "conf");
 384               continue;
 385             }
 386         }
 387       statp->nscount = nserv;
 388       if (have_serv6)
 389         /* We try IPv6 servers again.  */
 390         statp->ipv6_unavail = false;
 391       statp->nsort = nsort;
 392       fclose (fp);
 393     }
 394   if (__glibc_unlikely (statp->nscount == 0))
 395     {
 396       statp->nsaddr.sin_addr = __inet_makeaddr (IN_LOOPBACKNET, 1);
 397       statp->nsaddr.sin_family = AF_INET;
 398       statp->nsaddr.sin_port = htons (NAMESERVER_PORT);
 399       statp->nscount = 1;
 400     }
 401   if (statp->defdname[0] == 0)
 402     {
 403       char buf[sizeof (statp->defdname)];
 404       if (__gethostname (buf, sizeof (statp->defdname) - 1) == 0
 405           && (cp = strchr (buf, '.')) != NULL)
 406         strcpy (statp->defdname, cp + 1);
 407     }
 408
 409   /* Find components of local domain that might be searched.  */
 410   if (!havesearch)
 411     {
 412       pp = statp->dnsrch;
 413       *pp++ = statp->defdname;
 414       *pp = NULL;
 415
 416     }
 417
 418   if ((cp = getenv ("RES_OPTIONS")) != NULL)
 419     res_setoptions (statp, cp, "env");
 420   statp->options |= RES_INIT;
 421   return true;
 422 }
 423
 424 /* Set up default settings.  If the /etc/resolv.conf configuration
 425    file exist, the values there will have precedence.  Otherwise, the
 426    server address is set to INADDR_LOOPBACK and the default domain
 427    name comes from gethostname.  The RES_OPTIONS and LOCALDOMAIN
 428    environment variables can be used to override some settings.
 429    Return 0 if completes successfully, -1 on error.  */
 430 int
 431 __res_vinit (res_state statp, int preinit)
 432 {
 433   FILE *fp = fopen (_PATH_RESCONF, "rce");
 434   if (fp == NULL)
 435     switch (errno)
 436       {
 437       case EACCES:
 438       case EISDIR:
 439       case ELOOP:
 440       case ENOENT:
 441       case ENOTDIR:
 442       case EPERM:
 443         /* Ignore these errors.  They are persistent errors caused
 444            by file system contents.  */
 445         break;
 446       default:
 447         /* Other errors refer to resource allocation problems and
 448            need to be handled by the application.  */
 449         return -1;
 450       }
 451
 452   char *buffer = NULL;
 453   bool ok = res_vinit_1 (statp, preinit, fp, &buffer);
 454   free (buffer);
 455
 456   if (!ok)
 457     {
 458       /* Deallocate the name server addresses which have been
 459          allocated.  */
 460       for (int n = 0; n < MAXNS; n++)
 461         free (statp->_u._ext.nsaddrs[n]);
 462       return -1;
 463     }
 464   return 0;
 465 }
 466
 467 static void
 468 res_setoptions (res_state statp, const char *options, const char *source)
 469 {
 470   const char *cp = options;
 471
 472   while (*cp)
 473     {
 474       /* Skip leading and inner runs of spaces.  */
 475       while (*cp == ' ' || *cp == '\t')
 476         cp++;
 477       /* Search for and process individual options.  */
 478       if (!strncmp (cp, "ndots:", sizeof ("ndots:") - 1))
 479         {
 480           int i = atoi (cp + sizeof ("ndots:") - 1);
 481           if (i <= RES_MAXNDOTS)
 482             statp->ndots = i;
 483           else
 484             statp->ndots = RES_MAXNDOTS;
 485         }
 486       else if (!strncmp (cp, "timeout:", sizeof ("timeout:") - 1))
 487         {
 488           int i = atoi (cp + sizeof ("timeout:") - 1);
 489           if (i <= RES_MAXRETRANS)
 490             statp->retrans = i;
 491           else
 492             statp->retrans = RES_MAXRETRANS;
 493         }
 494       else if (!strncmp (cp, "attempts:", sizeof ("attempts:") - 1))
 495         {
 496           int i = atoi (cp + sizeof ("attempts:") - 1);
 497           if (i <= RES_MAXRETRY)
 498             statp->retry = i;
 499           else
 500             statp->retry = RES_MAXRETRY;
 501         }
 502       else
 503         {
 504           static const struct
 505           {
 506             char str[22];
 507             uint8_t len;
 508             uint8_t clear;
 509             unsigned long int flag;
 510           } options[] = {
 511 #define STRnLEN(str) str, sizeof (str) - 1
 512             { STRnLEN ("inet6"), 0, DEPRECATED_RES_USE_INET6 },
 513             { STRnLEN ("rotate"), 0, RES_ROTATE },
 514             { STRnLEN ("edns0"), 0, RES_USE_EDNS0 },
 515             { STRnLEN ("single-request-reopen"), 0, RES_SNGLKUPREOP },
 516             { STRnLEN ("single-request"), 0, RES_SNGLKUP },
 517             { STRnLEN ("no_tld_query"), 0, RES_NOTLDQUERY },
 518             { STRnLEN ("no-tld-query"), 0, RES_NOTLDQUERY },
 519             { STRnLEN ("use-vc"), 0, RES_USEVC }
 520           };
 521 #define noptions (sizeof (options) / sizeof (options[0]))
 522           for (int i = 0; i < noptions; ++i)
 523             if (strncmp (cp, options[i].str, options[i].len) == 0)
 524               {
 525                 if (options[i].clear)
 526                   statp->options &= options[i].flag;
 527                 else
 528                   statp->options |= options[i].flag;
 529                 break;
 530               }
 531         }
 532       /* Skip to next run of spaces.  */
 533       while (*cp && *cp != ' ' && *cp != '\t')
 534         cp++;
 535     }
 536 }
 537
 538 static uint32_t
 539 net_mask (struct in_addr in)
 540 {
 541   uint32_t i = ntohl (in.s_addr);
 542
 543   if (IN_CLASSA (i))
 544     return htonl (IN_CLASSA_NET);
 545   else if (IN_CLASSB (i))
 546     return htonl (IN_CLASSB_NET);
 547   return htonl (IN_CLASSC_NET);
 548 }