glibc/nss/nss_files/files-hosts.c

/* Hosts file parser in nss_files module.
   Copyright (C) 1996-2017 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/>.  */

#include <assert.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <netdb.h>
#include <resolv/resolv-internal.h>


/* Get implementation for some internal functions.  */
#include "../resolv/mapv4v6addr.h"
#include "../resolv/res_hconf.h"


#define ENTNAME		hostent
#define DATABASE	"hosts"
#define NEED_H_ERRNO

#define EXTRA_ARGS	 , af, flags
#define EXTRA_ARGS_DECL	 , int af, int flags

#define ENTDATA hostent_data
struct hostent_data
  {
    unsigned char host_addr[16]; /* IPv4 or IPv6 address.  */
    char *h_addr_ptrs[2];	/* Points to that and null terminator.  */
  };

#define TRAILING_LIST_MEMBER		h_aliases
#define TRAILING_LIST_SEPARATOR_P	isspace
#include "files-parse.c"
LINE_PARSER
("#",
 {
   char *addr;

   STRING_FIELD (addr, isspace, 1);

   /* Parse address.  */
   if (inet_pton (af == AF_UNSPEC ? AF_INET : af, addr, entdata->host_addr)
       > 0)
     af = af == AF_UNSPEC ? AF_INET : af;
   else
     {
       if (af == AF_INET6 && (flags & AI_V4MAPPED) != 0
	   && inet_pton (AF_INET, addr, entdata->host_addr) > 0)
	 map_v4v6_address ((char *) entdata->host_addr,
			   (char *) entdata->host_addr);
       else if (af == AF_INET
		&& inet_pton (AF_INET6, addr, entdata->host_addr) > 0)
	 {
	   if (IN6_IS_ADDR_V4MAPPED (entdata->host_addr))
	     memcpy (entdata->host_addr, entdata->host_addr + 12, INADDRSZ);
	   else if (IN6_IS_ADDR_LOOPBACK (entdata->host_addr))
	     {
	       in_addr_t localhost = htonl (INADDR_LOOPBACK);
	       memcpy (entdata->host_addr, &localhost, sizeof (localhost));
	     }
	   else
	     /* Illegal address: ignore line.  */
	     return 0;
	 }
       else if (af == AF_UNSPEC
		&& inet_pton (AF_INET6, addr, entdata->host_addr) > 0)
	 af = AF_INET6;
       else
	 /* Illegal address: ignore line.  */
	 return 0;
     }

   /* We always return entries of the requested form.  */
   result->h_addrtype = af;
   result->h_length = af == AF_INET ? INADDRSZ : IN6ADDRSZ;

   /* Store a pointer to the address in the expected form.  */
   entdata->h_addr_ptrs[0] = (char *) entdata->host_addr;
   entdata->h_addr_ptrs[1] = NULL;
   result->h_addr_list = entdata->h_addr_ptrs;

   STRING_FIELD (result->h_name, isspace, 1);
 })

#define EXTRA_ARGS_VALUE \
  , (res_use_inet6 () ? AF_INET6 : AF_INET),		      \
  (res_use_inet6 () ? AI_V4MAPPED : 0)
#include "files-XXX.c"
#undef EXTRA_ARGS_VALUE

/* We only need to consider IPv4 mapped addresses if the input to the
   gethostbyaddr() function is an IPv6 address.  */
#define EXTRA_ARGS_VALUE \
  , af, (len == IN6ADDRSZ ? AI_V4MAPPED : 0)
DB_LOOKUP (hostbyaddr, ,,,
	   {
	     if (result->h_length == (int) len
		 && ! memcmp (addr, result->h_addr_list[0], len))
	       break;
	   }, const void *addr, socklen_t len, int af)
#undef EXTRA_ARGS_VALUE

enum nss_status
_nss_files_gethostbyname3_r (const char *name, int af, struct hostent *result,
			     char *buffer, size_t buflen, int *errnop,
			     int *herrnop, int32_t *ttlp, char **canonp)
{
  FILE *stream = NULL;
  uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct hostent_data);
  buffer += pad;
  buflen = buflen > pad ? buflen - pad : 0;

  /* Open file.  */
  enum nss_status status = internal_setent (&stream);

  if (status == NSS_STATUS_SUCCESS)
    {
      /* XXX Is using _res to determine whether we want to convert IPv4
         addresses to IPv6 addresses really the right thing to do?  */
      int flags = (res_use_inet6 () ? AI_V4MAPPED : 0);

      while ((status = internal_getent (stream, result, buffer, buflen, errnop,
					herrnop, af, flags))
	     == NSS_STATUS_SUCCESS)
	{
	  LOOKUP_NAME_CASE (h_name, h_aliases)
	}

      if (status == NSS_STATUS_SUCCESS
	  && _res_hconf.flags & HCONF_FLAG_MULTI)
	{
	  /* We have to get all host entries from the file.  */
	  size_t tmp_buflen = MIN (buflen, 4096);
	  char tmp_buffer_stack[tmp_buflen]
	    __attribute__ ((__aligned__ (__alignof__ (struct hostent_data))));
	  char *tmp_buffer = tmp_buffer_stack;
	  struct hostent tmp_result_buf;
	  int naddrs = 1;
	  int naliases = 0;
	  char *bufferend;
	  bool tmp_buffer_malloced = false;

	  while (result->h_aliases[naliases] != NULL)
	    ++naliases;

	  bufferend = (char *) &result->h_aliases[naliases + 1];

	again:
	  while ((status = internal_getent (stream, &tmp_result_buf, tmp_buffer,
					    tmp_buflen, errnop, herrnop, af,
					    flags))
		 == NSS_STATUS_SUCCESS)
	    {
	      int matches = 1;
	      struct hostent *old_result = result;
	      result = &tmp_result_buf;
	      /* The following piece is a bit clumsy but we want to use the
		 `LOOKUP_NAME_CASE' value.  The optimizer should do its
		 job.  */
	      do
		{
		  LOOKUP_NAME_CASE (h_name, h_aliases)
		  result = old_result;
		}
	      while ((matches = 0));

	      if (matches)
		{
		  /* We could be very clever and try to recycle a few bytes
		     in the buffer instead of generating new arrays.  But
		     we are not doing this here since it's more work than
		     it's worth.  Simply let the user provide a bit bigger
		     buffer.  */
		  char **new_h_addr_list;
		  char **new_h_aliases;
		  int newaliases = 0;
		  size_t newstrlen = 0;
		  int cnt;

		  /* Count the new aliases and the length of the strings.  */
		  while (tmp_result_buf.h_aliases[newaliases] != NULL)
		    {
		      char *cp = tmp_result_buf.h_aliases[newaliases];
		      ++newaliases;
		      newstrlen += strlen (cp) + 1;
		    }
		  /* If the real name is different add it also to the
		     aliases.  This means that there is a duplication
		     in the alias list but this is really the user's
		     problem.  */
		  if (strcmp (old_result->h_name,
			      tmp_result_buf.h_name) != 0)
		    {
		      ++newaliases;
		      newstrlen += strlen (tmp_result_buf.h_name) + 1;
		    }

		  /* Make sure bufferend is aligned.  */
		  assert ((bufferend - (char *) 0) % sizeof (char *) == 0);

		  /* Now we can check whether the buffer is large enough.
		     16 is the maximal size of the IP address.  */
		  if (bufferend + 16 + (naddrs + 2) * sizeof (char *)
		      + roundup (newstrlen, sizeof (char *))
		      + (naliases + newaliases + 1) * sizeof (char *)
		      >= buffer + buflen)
		    {
		      *errnop = ERANGE;
		      *herrnop = NETDB_INTERNAL;
		      status = NSS_STATUS_TRYAGAIN;
		      goto out;
		    }

		  new_h_addr_list =
		    (char **) (bufferend
			       + roundup (newstrlen, sizeof (char *))
			       + 16);
		  new_h_aliases =
		    (char **) ((char *) new_h_addr_list
			       + (naddrs + 2) * sizeof (char *));

		  /* Copy the old data in the new arrays.  */
		  for (cnt = 0; cnt < naddrs; ++cnt)
		    new_h_addr_list[cnt] = old_result->h_addr_list[cnt];

		  for (cnt = 0; cnt < naliases; ++cnt)
		    new_h_aliases[cnt] = old_result->h_aliases[cnt];

		  /* Store the new strings.  */
		  cnt = 0;
		  while (tmp_result_buf.h_aliases[cnt] != NULL)
		    {
		      new_h_aliases[naliases++] = bufferend;
		      bufferend = (__stpcpy (bufferend,
					     tmp_result_buf.h_aliases[cnt])
				   + 1);
		      ++cnt;
		    }

		  if (cnt < newaliases)
		    {
		      new_h_aliases[naliases++] = bufferend;
		      bufferend = __stpcpy (bufferend,
					    tmp_result_buf.h_name) + 1;
		    }

		  /* Final NULL pointer.  */
		  new_h_aliases[naliases] = NULL;

		  /* Round up the buffer end address.  */
		  bufferend += (sizeof (char *)
				- ((bufferend - (char *) 0)
				   % sizeof (char *))) % sizeof (char *);

		  /* Now the new address.  */
		  new_h_addr_list[naddrs++] =
		    memcpy (bufferend, tmp_result_buf.h_addr,
			    tmp_result_buf.h_length);

		  /* Also here a final NULL pointer.  */
		  new_h_addr_list[naddrs] = NULL;

		  /* Store the new array pointers.  */
		  old_result->h_aliases = new_h_aliases;
		  old_result->h_addr_list = new_h_addr_list;

		  /* Compute the new buffer end.  */
		  bufferend = (char *) &new_h_aliases[naliases + 1];
		  assert (bufferend <= buffer + buflen);

		  result = old_result;
		}
	    }

	  if (status == NSS_STATUS_TRYAGAIN)
	    {
	      size_t newsize = 2 * tmp_buflen;
	      if (tmp_buffer_malloced)
		{
		  char *newp = realloc (tmp_buffer, newsize);
		  if (newp != NULL)
		    {
		      assert ((((uintptr_t) newp)
			       & (__alignof__ (struct hostent_data) - 1))
			      == 0);
		      tmp_buffer = newp;
		      tmp_buflen = newsize;
		      goto again;
		    }
		}
	      else if (!__libc_use_alloca (buflen + newsize))
		{
		  tmp_buffer = malloc (newsize);
		  if (tmp_buffer != NULL)
		    {
		      assert ((((uintptr_t) tmp_buffer)
			       & (__alignof__ (struct hostent_data) - 1))
			      == 0);
		      tmp_buffer_malloced = true;
		      tmp_buflen = newsize;
		      goto again;
		    }
		}
	      else
		{
		  tmp_buffer
		    = extend_alloca (tmp_buffer, tmp_buflen,
				     newsize
				     + __alignof__ (struct hostent_data));
		  tmp_buffer = (char *) (((uintptr_t) tmp_buffer
					  + __alignof__ (struct hostent_data)
					  - 1)
					 & ~(__alignof__ (struct hostent_data)
					     - 1));
		  goto again;
		}
	    }
	  else
	    status = NSS_STATUS_SUCCESS;
	out:
	  if (tmp_buffer_malloced)
	    free (tmp_buffer);
	}

      internal_endent (&stream);
    }

  if (canonp && status == NSS_STATUS_SUCCESS)
    *canonp = result->h_name;

  return status;
}

enum nss_status
_nss_files_gethostbyname_r (const char *name, struct hostent *result,
			    char *buffer, size_t buflen, int *errnop,
			    int *herrnop)
{
  int af = (res_use_inet6 () ? AF_INET6 : AF_INET);

  return _nss_files_gethostbyname3_r (name, af, result, buffer, buflen,
				      errnop, herrnop, NULL, NULL);
}

enum nss_status
_nss_files_gethostbyname2_r (const char *name, int af, struct hostent *result,
			     char *buffer, size_t buflen, int *errnop,
			     int *herrnop)
{
  return _nss_files_gethostbyname3_r (name, af, result, buffer, buflen,
				      errnop, herrnop, NULL, NULL);
}

enum nss_status
_nss_files_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
			     char *buffer, size_t buflen, int *errnop,
			     int *herrnop, int32_t *ttlp)
{
  FILE *stream = NULL;

  /* Open file.  */
  enum nss_status status = internal_setent (&stream);

  if (status == NSS_STATUS_SUCCESS)
    {
      bool any = false;
      bool got_canon = false;
      while (1)
	{
	  /* Align the buffer for the next record.  */
	  uintptr_t pad = (-(uintptr_t) buffer
			   % __alignof__ (struct hostent_data));
	  buffer += pad;
	  buflen = buflen > pad ? buflen - pad : 0;

	  struct hostent result;
	  status = internal_getent (stream, &result, buffer, buflen, errnop,
				    herrnop, AF_UNSPEC, 0);
	  if (status != NSS_STATUS_SUCCESS)
	    break;

	  int naliases = 0;
	  if (__strcasecmp (name, result.h_name) != 0)
	    {
	      for (; result.h_aliases[naliases] != NULL; ++naliases)
		if (! __strcasecmp (name, result.h_aliases[naliases]))
		  break;
	      if (result.h_aliases[naliases] == NULL)
		continue;

	      /* We know this alias exist.  Count it.  */
	      ++naliases;
	    }

	  /* Determine how much memory has been used so far.  */
	  // XXX It is not necessary to preserve the aliases array
	  while (result.h_aliases[naliases] != NULL)
	    ++naliases;
	  char *bufferend = (char *) &result.h_aliases[naliases + 1];
	  assert (buflen >= bufferend - buffer);
	  buflen -= bufferend - buffer;
	  buffer = bufferend;

	  /* We found something.  */
	  any = true;

	  /* Create the record the caller expects.  There is only one
	     address.  */
	  assert (result.h_addr_list[1] == NULL);
	  if (*pat == NULL)
	    {
	      uintptr_t pad = (-(uintptr_t) buffer
			       % __alignof__ (struct gaih_addrtuple));
	      buffer += pad;
	      buflen = buflen > pad ? buflen - pad : 0;

	      if (__builtin_expect (buflen < sizeof (struct gaih_addrtuple),
				    0))
		{
		  *errnop = ERANGE;
		  *herrnop = NETDB_INTERNAL;
		  status = NSS_STATUS_TRYAGAIN;
		  break;
		}

	      *pat = (struct gaih_addrtuple *) buffer;
	      buffer += sizeof (struct gaih_addrtuple);
	      buflen -= sizeof (struct gaih_addrtuple);
	    }

	  (*pat)->next = NULL;
	  (*pat)->name = got_canon ? NULL : result.h_name;
	  got_canon = true;
	  (*pat)->family = result.h_addrtype;
	  memcpy ((*pat)->addr, result.h_addr_list[0], result.h_length);
	  (*pat)->scopeid = 0;

	  pat = &((*pat)->next);

	  /* If we only look for the first matching entry we are done.  */
	  if ((_res_hconf.flags & HCONF_FLAG_MULTI) == 0)
	    break;
	}

      /* If we have to look for multiple records and found one, this
	 is a success.  */
      if (status == NSS_STATUS_NOTFOUND && any)
	{
	  assert ((_res_hconf.flags & HCONF_FLAG_MULTI) != 0);
	  status = NSS_STATUS_SUCCESS;
	}

      internal_endent (&stream);
    }
  else if (status == NSS_STATUS_TRYAGAIN)
    {
      *errnop = errno;
      *herrnop = TRY_AGAIN;
    }
  else
    {
      *errnop = errno;
      *herrnop = NO_DATA;
    }

  return status;
}