/* Resolver state initialization and resolv.conf parsing.

   Copyright (C) 1995-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

/*

 * Copyright (c) 1985, 1989, 1993

 *    The Regents of the University of California.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 4. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

/*

 * Portions Copyright (c) 1993 by Digital Equipment Corporation.

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies, and that

 * the name of Digital Equipment Corporation not be used in advertising or

 * publicity pertaining to distribution of the document or software without

 * specific, written prior permission.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL

 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT

 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL

 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR

 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS

 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS

 * SOFTWARE.

 */

/*

 * Portions Copyright (c) 1996-1999 by Internet Software Consortium.

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS

 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE

 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL

 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR

 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS

 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS

 * SOFTWARE.

 */

#include <ctype.h>

#include <netdb.h>

#include <resolv/resolv-internal.h>

#include <res_hconf.h>

#include <stdio.h>

#include <stdio_ext.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <stdint.h>

#include <arpa/inet.h>

#include <arpa/nameser.h>

#include <net/if.h>

#include <netinet/in.h>

#include <sys/param.h>

#include <sys/socket.h>

#include <sys/time.h>

#include <sys/types.h>

#include <inet/net-internal.h>

#include <errno.h>

#include <resolv_conf.h>

#include <file_change_detection.h>

static uint32_t net_mask (struct in_addr);

int

res_ninit (res_state statp)

{

  return __res_vinit (statp, 0);

}

libc_hidden_def (__res_ninit)

/* Return true if CH separates the netmask in the "sortlist"

   directive.  */

static inline bool

is_sort_mask (char ch)

{

  return ch == '/' || ch == '&';

}

/* Array of name server addresses.  */

#define DYNARRAY_STRUCT nameserver_list

#define DYNARRAY_ELEMENT const struct sockaddr *

#define DYNARRAY_ELEMENT_FREE(e) free ((struct sockaddr *) *(e))

#define DYNARRAY_INITIAL_SIZE 3

#define DYNARRAY_PREFIX nameserver_list_

#include <malloc/dynarray-skeleton.c>

/* Array of strings for the search array.  The backing store is

   managed separately.  */

#define DYNARRAY_STRUCT search_list

#define DYNARRAY_ELEMENT const char *

#define DYNARRAY_INITIAL_SIZE 6

#define DYNARRAY_PREFIX search_list_

#include <malloc/dynarray-skeleton.c>

/* Array of name server addresses.  */

#define DYNARRAY_STRUCT sort_list

#define DYNARRAY_ELEMENT struct resolv_sortlist_entry

#define DYNARRAY_INITIAL_SIZE 0

#define DYNARRAY_PREFIX sort_list_

#include <malloc/dynarray-skeleton.c>

/* resolv.conf parser state and results.  */

struct resolv_conf_parser

{

  char *buffer;            /* Temporary buffer for reading lines.  */

  struct nameserver_list nameserver_list; /* Nameserver addresses.  */

  char *search_list_store; /* Backing storage for search list entries.  */

  struct search_list search_list; /* Points into search_list_store.  */

  struct sort_list sort_list;   /* Address preference sorting list.  */

  /* Configuration template.  The non-array elements are filled in

     directly.  The array elements are updated prior to the call to

     __resolv_conf_attach.  */

  struct resolv_conf template;

};

/* Return true if *PREINIT contains actual preinitialization.  */

static bool

has_preinit_values (const struct __res_state *preinit)

{

  return (preinit->retrans != 0 && preinit->retrans != RES_TIMEOUT)

    || (preinit->retry != 0 && preinit->retry != RES_DFLRETRY)

    || (preinit->options != 0

        && (preinit->options & ~RES_INIT) != RES_DEFAULT);

}

static void

resolv_conf_parser_init (struct resolv_conf_parser *parser,

                         const struct __res_state *preinit)

{

  parser->buffer = NULL;

  parser->search_list_store = NULL;

  nameserver_list_init (&parser->nameserver_list);

  search_list_init (&parser->search_list);

  sort_list_init (&parser->sort_list);

  if (preinit != NULL)

    {

      parser->template.retrans = preinit->retrans;

      parser->template.retry = preinit->retry;

      parser->template.options = preinit->options | RES_INIT;

    }

  else

    {

      parser->template.retrans = RES_TIMEOUT;

      parser->template.retry = RES_DFLRETRY;

      parser->template.options = RES_DEFAULT | RES_INIT;

    }

  parser->template.ndots = 1;

}

static void

resolv_conf_parser_free (struct resolv_conf_parser *parser)

{

  free (parser->buffer);

  free (parser->search_list_store);

  nameserver_list_free (&parser->nameserver_list);

  search_list_free (&parser->search_list);

  sort_list_free (&parser->sort_list);

}

/* Allocate a struct sockaddr_in object on the heap, with the

   specified address and port.  */

static struct sockaddr *

allocate_address_v4 (struct in_addr a, uint16_t port)

{

  struct sockaddr_in *sa4 = malloc (sizeof (*sa4));

  if (sa4 == NULL)

    return NULL;

  sa4->sin_family = AF_INET;

  sa4->sin_addr = a;

  sa4->sin_port = htons (port);

  return (struct sockaddr *) sa4;

}

/* Try to obtain the domain name from the host name and store it in

   *RESULT.  Return false on memory allocation failure.  If the domain

   name cannot be determined for any other reason, write NULL to

   *RESULT and return true.  */

static bool

domain_from_hostname (char **result)

{

  char buf[256];

  /* gethostbyname may not terminate the buffer.  */

  buf[sizeof (buf) - 1] = '\0';

  if (__gethostname (buf, sizeof (buf) - 1) == 0)

    {

      char *dot = strchr (buf, '.');

      if (dot != NULL)

        {

          *result = __strdup (dot + 1);

          if (*result == NULL)

            return false;

          return true;

        }

    }

  *result = NULL;

  return true;

}

static void res_setoptions (struct resolv_conf_parser *, const char *options);

/* Internal helper function for __res_vinit, to aid with resource

   deallocation and error handling.  Return true on success, false on

   failure.  */

static bool

res_vinit_1 (FILE *fp, struct resolv_conf_parser *parser)

{

  char *cp;

  size_t buffer_size = 0;

  bool haveenv = false;

  /* Allow user to override the local domain definition.  */

  if ((cp = getenv ("LOCALDOMAIN")) != NULL)

    {

      /* The code below splits the string in place.  */

      cp = __strdup (cp);

      if (cp == NULL)

        return false;

      free (parser->search_list_store);

      parser->search_list_store = cp;

      haveenv = true;

      /* The string will be truncated as needed below.  */

      search_list_add (&parser->search_list, cp);

      /* Set search list to be blank-separated strings from rest of

         env value.  Permits users of LOCALDOMAIN to still have a

         search list, and anyone to set the one that they want to use

         as an individual (even more important now that the rfc1535

         stuff restricts searches).  */

      for (bool in_name = true; *cp != '\0'; cp++)

        {

          if (*cp == '\n')

            {

              *cp = '\0';

              break;

            }

          else if (*cp == ' ' || *cp == '\t')

            {

              *cp = '\0';

              in_name = false;

            }

          else if (!in_name)

            {

              search_list_add (&parser->search_list, cp);

              in_name = true;

            }

        }

    }

#define MATCH(line, name)                       \

  (!strncmp ((line), name, sizeof (name) - 1)     \

   && ((line)[sizeof (name) - 1] == ' '           \

       || (line)[sizeof (name) - 1] == '\t'))

  if (fp != NULL)

    {

      /* No threads use this stream.  */

      __fsetlocking (fp, FSETLOCKING_BYCALLER);

      /* Read the config file.  */

      while (true)

        {

          {

            ssize_t ret = __getline (&parser->buffer, &buffer_size, fp);

            if (ret <= 0)

              {

                if (_IO_ferror_unlocked (fp))

                  return false;

                else

                  break;

              }

          }

          /* Skip comments.  */

          if (*parser->buffer == ';' || *parser->buffer == '#')

            continue;

          /* Read default domain name.  */

          if (MATCH (parser->buffer, "domain"))

            {

              if (haveenv)

                /* LOCALDOMAIN overrides the configuration file.  */

                continue;

              cp = parser->buffer + sizeof ("domain") - 1;

              while (*cp == ' ' || *cp == '\t')

                cp++;

              if ((*cp == '\0') || (*cp == '\n'))

                continue;

              cp = __strdup (cp);

              if (cp == NULL)

                return false;

              free (parser->search_list_store);

              parser->search_list_store = cp;

              search_list_clear (&parser->search_list);

              search_list_add (&parser->search_list, cp);

              /* Replace trailing whitespace.  */

              if ((cp = strpbrk (cp, " \t\n")) != NULL)

                *cp = '\0';

              continue;

            }

          /* Set search list.  */

          if (MATCH (parser->buffer, "search"))

            {

              if (haveenv)

                /* LOCALDOMAIN overrides the configuration file.  */

                continue;

              cp = parser->buffer + sizeof ("search") - 1;

              while (*cp == ' ' || *cp == '\t')

                cp++;

              if ((*cp == '\0') || (*cp == '\n'))

                continue;

              {

                char *p = strchr (cp, '\n');

                if (p != NULL)

                  *p = '\0';

              }

              cp = __strdup (cp);

              if (cp == NULL)

                return false;

              free (parser->search_list_store);

              parser->search_list_store = cp;

              /* The string is truncated below.  */

              search_list_clear (&parser->search_list);

              search_list_add (&parser->search_list, cp);

              /* Set search list to be blank-separated strings on rest

                 of line.  */

              for (bool in_name = true; *cp != '\0'; cp++)

                {

                  if (*cp == ' ' || *cp == '\t')

                    {

                      *cp = '\0';

                      in_name = false;

                    }

                  else if (!in_name)

                    {

                      search_list_add (&parser->search_list, cp);

                      in_name = true;

                    }

                }

              continue;

            }

          /* Read nameservers to query.  */

          if (MATCH (parser->buffer, "nameserver"))

            {

              struct in_addr a;

              cp = parser->buffer + sizeof ("nameserver") - 1;

              while (*cp == ' ' || *cp == '\t')

                cp++;

              /* Ignore trailing contents on the name server line.  */

              {

                char *el;

                if ((el = strpbrk (cp, " \t\n")) != NULL)

                  *el = '\0';

              }

              struct sockaddr *sa;

              if ((*cp != '\0') && (*cp != '\n') && __inet_aton_exact (cp, &a))

                {

                  sa = allocate_address_v4 (a, NAMESERVER_PORT);

                  if (sa == NULL)

                    return false;

                }

              else

                {

                  struct in6_addr a6;

                  char *el;

                  if ((el = strchr (cp, SCOPE_DELIMITER)) != NULL)

                    *el = '\0';

                  if ((*cp != '\0') && (__inet_pton (AF_INET6, cp, &a6) > 0))

                    {

                      struct sockaddr_in6 *sa6;

                      sa6 = malloc (sizeof (*sa6));

                      if (sa6 == NULL)

                        return false;

                      sa6->sin6_family = AF_INET6;

                      sa6->sin6_port = htons (NAMESERVER_PORT);

                      sa6->sin6_flowinfo = 0;

                      sa6->sin6_addr = a6;

                      sa6->sin6_scope_id = 0;

                      if (__glibc_likely (el != NULL))

                        /* Ignore errors, for backwards

                           compatibility.  */

                        __inet6_scopeid_pton

                          (&a6, el + 1, &sa6->sin6_scope_id);

                      sa = (struct sockaddr *) sa6;

                    }

                  else

                    /* IPv6 address parse failure.  */

                    sa = NULL;

                }

              if (sa != NULL)

                {

                  const struct sockaddr **p = nameserver_list_emplace

                    (&parser->nameserver_list);

                  if (p != NULL)

                    *p = sa;

                  else

                    {

                      free (sa);

                      return false;

                    }

                }

              continue;

            }

          if (MATCH (parser->buffer, "sortlist"))

            {

              struct in_addr a;

              cp = parser->buffer + sizeof ("sortlist") - 1;

              while (true)

                {

                  while (*cp == ' ' || *cp == '\t')

                    cp++;

                  if (*cp == '\0' || *cp == '\n' || *cp == ';')

                    break;

                  char *net = cp;

                  while (*cp && !is_sort_mask (*cp) && *cp != ';'

                         && isascii (*cp) && !isspace (*cp))

                    cp++;

                  char separator = *cp;

                  *cp = 0;

                  struct resolv_sortlist_entry e;

                  if (__inet_aton_exact (net, &a))

                    {

                      e.addr = a;

                      if (is_sort_mask (separator))

                        {

                          *cp++ = separator;

                          net = cp;

                          while (*cp && *cp != ';'

                                 && isascii (*cp) && !isspace (*cp))

                            cp++;

                          separator = *cp;

                          *cp = 0;

                          if (__inet_aton_exact (net, &a))

                            e.mask = a.s_addr;

                          else

                            e.mask = net_mask (e.addr);

                        }

                      else

                        e.mask = net_mask (e.addr);

                      sort_list_add (&parser->sort_list, e);

                    }

                  *cp = separator;

                }

              continue;

            }

          if (MATCH (parser->buffer, "options"))

            {

              res_setoptions (parser, parser->buffer + sizeof ("options") - 1);

              continue;

            }

        }

    }

  if (__glibc_unlikely (nameserver_list_size (&parser->nameserver_list) == 0))

    {

      const struct sockaddr **p

        = nameserver_list_emplace (&parser->nameserver_list);

      if (p == NULL)

        return false;

      *p = allocate_address_v4 (__inet_makeaddr (IN_LOOPBACKNET, 1),

                                NAMESERVER_PORT);

      if (*p == NULL)

        return false;

    }

  if (search_list_size (&parser->search_list) == 0)

    {

      char *domain;

      if (!domain_from_hostname (&domain))

        return false;

      if (domain != NULL)

        {

          free (parser->search_list_store);

          parser->search_list_store = domain;

          search_list_add (&parser->search_list, domain);

        }

    }

  if ((cp = getenv ("RES_OPTIONS")) != NULL)

    res_setoptions (parser, cp);

  if (nameserver_list_has_failed (&parser->nameserver_list)

      || search_list_has_failed (&parser->search_list)

      || sort_list_has_failed (&parser->sort_list))

    {

      __set_errno (ENOMEM);

      return false;

    }

  return true;

}

struct resolv_conf *

__resolv_conf_load (struct __res_state *preinit,

                    struct file_change_detection *change)

{

  /* Ensure that /etc/hosts.conf has been loaded (once).  */

  _res_hconf_init ();

  FILE *fp = fopen (_PATH_RESCONF, "rce");

  if (fp == NULL)

    switch (errno)

      {

      case EACCES:

      case EISDIR:

      case ELOOP:

      case ENOENT:

      case ENOTDIR:

      case EPERM:

        /* Ignore these errors.  They are persistent errors caused

           by file system contents.  */

        break;

      default:

        /* Other errors refer to resource allocation problems and

           need to be handled by the application.  */

        return NULL;

      }

  struct resolv_conf_parser parser;

  resolv_conf_parser_init (&parser, preinit);

  struct resolv_conf *conf = NULL;

  bool ok = res_vinit_1 (fp, &parser);

  if (ok && change != NULL)

    /* Update the file change information if the configuration was

       loaded successfully.  */

    ok = __file_change_detection_for_fp (change, fp);

  if (ok)

    {

      parser.template.nameserver_list

        = nameserver_list_begin (&parser.nameserver_list);

      parser.template.nameserver_list_size

        = nameserver_list_size (&parser.nameserver_list);

      parser.template.search_list = search_list_begin (&parser.search_list);

      parser.template.search_list_size

        = search_list_size (&parser.search_list);

      parser.template.sort_list = sort_list_begin (&parser.sort_list);

      parser.template.sort_list_size = sort_list_size (&parser.sort_list);

      conf = __resolv_conf_allocate (&parser.template);

    }

  resolv_conf_parser_free (&parser);

  if (fp != NULL)

    {

      int saved_errno = errno;

      fclose (fp);

      __set_errno (saved_errno);

    }

  return conf;

}

/* Set up default settings.  If the /etc/resolv.conf configuration

   file exist, the values there will have precedence.  Otherwise, the

   server address is set to INADDR_LOOPBACK and the default domain

   name comes from gethostname.  The RES_OPTIONS and LOCALDOMAIN

   environment variables can be used to override some settings.

   Return 0 if completes successfully, -1 on error.  */

int

__res_vinit (res_state statp, int preinit)

{

  struct resolv_conf *conf;

  if (preinit && has_preinit_values (statp))

    /* For the preinit case, we cannot use the cached configuration

       because some settings could be different.  */

    conf = __resolv_conf_load (statp, NULL);

  else

    conf = __resolv_conf_get_current ();

  if (conf == NULL)

    return -1;

  bool ok = __resolv_conf_attach (statp, conf);

  __resolv_conf_put (conf);

  if (ok)

    {

      if (preinit)

        statp->id = res_randomid ();

      return 0;

    }

  else

    return -1;

}

static void

res_setoptions (struct resolv_conf_parser *parser, const char *options)

{

  const char *cp = options;

  while (*cp)

    {

      /* Skip leading and inner runs of spaces.  */

      while (*cp == ' ' || *cp == '\t')

        cp++;

      /* Search for and process individual options.  */

      if (!strncmp (cp, "ndots:", sizeof ("ndots:") - 1))

        {

          int i = atoi (cp + sizeof ("ndots:") - 1);

          if (i <= RES_MAXNDOTS)

            parser->template.ndots = i;

          else

            parser->template.ndots = RES_MAXNDOTS;

        }

      else if (!strncmp (cp, "timeout:", sizeof ("timeout:") - 1))

        {

          int i = atoi (cp + sizeof ("timeout:") - 1);

          if (i <= RES_MAXRETRANS)

            parser->template.retrans = i;

          else

            parser->template.retrans = RES_MAXRETRANS;

        }

      else if (!strncmp (cp, "attempts:", sizeof ("attempts:") - 1))

        {

          int i = atoi (cp + sizeof ("attempts:") - 1);

          if (i <= RES_MAXRETRY)

            parser->template.retry = i;

          else

            parser->template.retry = RES_MAXRETRY;

        }

      else

        {

          static const struct

          {

            char str[22];

            uint8_t len;

            uint8_t clear;

            unsigned long int flag;

          } options[] = {

#define STRnLEN(str) str, sizeof (str) - 1

            { STRnLEN ("inet6"), 0, DEPRECATED_RES_USE_INET6 },

            { STRnLEN ("rotate"), 0, RES_ROTATE },

            { STRnLEN ("edns0"), 0, RES_USE_EDNS0 },

            { STRnLEN ("single-request-reopen"), 0, RES_SNGLKUPREOP },

            { STRnLEN ("single-request"), 0, RES_SNGLKUP },

            { STRnLEN ("no_tld_query"), 0, RES_NOTLDQUERY },

            { STRnLEN ("no-tld-query"), 0, RES_NOTLDQUERY },

            { STRnLEN ("no-reload"), 0, RES_NORELOAD },

            { STRnLEN ("use-vc"), 0, RES_USEVC }

          };

#define noptions (sizeof (options) / sizeof (options[0]))

          for (int i = 0; i < noptions; ++i)

            if (strncmp (cp, options[i].str, options[i].len) == 0)

              {

                if (options[i].clear)

                  parser->template.options &= options[i].flag;

                else

                  parser->template.options |= options[i].flag;

                break;

              }

        }

      /* Skip to next run of spaces.  */

      while (*cp && *cp != ' ' && *cp != '\t')

        cp++;

    }

}

static uint32_t

net_mask (struct in_addr in)

{

  uint32_t i = ntohl (in.s_addr);

  if (IN_CLASSA (i))

    return htonl (IN_CLASSA_NET);

  else if (IN_CLASSB (i))

    return htonl (IN_CLASSB_NET);

  return htonl (IN_CLASSC_NET);

}