/* Copyright 1998 by the Massachusetts Institute of Technology.

 *

 * Permission to use, copy, modify, and distribute this

 * software and its documentation for any purpose and without

 * fee is hereby granted, provided that the above copyright

 * notice appear in all copies and that both that copyright

 * notice and this permission notice appear in supporting

 * documentation, and that the name of M.I.T. not be used in

 * advertising or publicity pertaining to distribution of the

 * software without specific, written prior permission.

 * M.I.T. makes no representations about the suitability of

 * this software for any purpose.  It is provided "as is"

 * without express or implied warranty.

 *

 * SPDX-License-Identifier: MIT

 */

/*

 * ares_parse_ns_reply created by Vlad Dinulescu <vlad.dinulescu@avira.com>

 *      on behalf of AVIRA Gmbh - http://www.avira.com

 */

#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H

#  include <netinet/in.h>

#endif

#ifdef HAVE_NETDB_H

#  include <netdb.h>

#endif

#ifdef HAVE_ARPA_INET_H

#  include <arpa/inet.h>

#endif

#include "ares_nameser.h"

#include "ares.h"

#include "ares_dns.h"

#include "ares_private.h"

int ares_parse_ns_reply( const unsigned char* abuf, int alen,

                         struct hostent** host )

{

  unsigned int qdcount, ancount;

  int status, i, rr_type, rr_class, rr_len;

  int nameservers_num;

  long len;

  const unsigned char *aptr;

  char* hostname, *rr_name, *rr_data, **nameservers;

  struct hostent *hostent;

  /* Set *host to NULL for all failure cases. */

  *host = NULL;

  /* Give up if abuf doesn't have room for a header. */

  if ( alen < HFIXEDSZ )

    return ARES_EBADRESP;

  /* Fetch the question and answer count from the header. */

  qdcount = DNS_HEADER_QDCOUNT( abuf );

  ancount = DNS_HEADER_ANCOUNT( abuf );

  if ( qdcount != 1 )

    return ARES_EBADRESP;

  /* Expand the name from the question, and skip past the question. */

  aptr = abuf + HFIXEDSZ;

  status = ares__expand_name_for_response( aptr, abuf, alen, &hostname, &len, 0);

  if ( status != ARES_SUCCESS )

    return status;

  if ( aptr + len + QFIXEDSZ > abuf + alen )

  {

    ares_free( hostname );

    return ARES_EBADRESP;

  }

  aptr += len + QFIXEDSZ;

  /* Allocate nameservers array; ancount gives an upper bound */

  nameservers = ares_malloc( ( ancount + 1 ) * sizeof( char * ) );

  if ( !nameservers )

  {

    ares_free( hostname );

    return ARES_ENOMEM;

  }

  nameservers_num = 0;

  /* Examine each answer resource record (RR) in turn. */

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

  {

    /* Decode the RR up to the data field. */

    status = ares__expand_name_for_response( aptr, abuf, alen, &rr_name, &len, 0);

    if ( status != ARES_SUCCESS )

      break;

    aptr += len;

    if ( aptr + RRFIXEDSZ > abuf + alen )

    {

      status = ARES_EBADRESP;

      ares_free(rr_name);

      break;

    }

    rr_type = DNS_RR_TYPE( aptr );

    rr_class = DNS_RR_CLASS( aptr );

    rr_len = DNS_RR_LEN( aptr );

    aptr += RRFIXEDSZ;

    if (aptr + rr_len > abuf + alen)

      {

        ares_free(rr_name);

        status = ARES_EBADRESP;

        break;

      }

    if ( rr_class == C_IN && rr_type == T_NS )

    {

      /* Decode the RR data and add it to the nameservers list */

      status = ares__expand_name_for_response( aptr, abuf, alen, &rr_data,

                                               &len, 1);

      if ( status != ARES_SUCCESS )

      {

        ares_free(rr_name);

        break;

      }

      nameservers[nameservers_num] = ares_malloc(strlen(rr_data)+1);

      if (nameservers[nameservers_num]==NULL)

      {

        ares_free(rr_name);

        ares_free(rr_data);

        status=ARES_ENOMEM;

        break;

      }

      strcpy(nameservers[nameservers_num],rr_data);

      ares_free(rr_data);

      nameservers_num++;

    }

    ares_free( rr_name );

    aptr += rr_len;

    if ( aptr > abuf + alen )

    {  /* LCOV_EXCL_START: already checked above */

      status = ARES_EBADRESP;

      break;

    }  /* LCOV_EXCL_STOP */

  }

  if ( status == ARES_SUCCESS && nameservers_num == 0 )

  {

    status = ARES_ENODATA;

  }

  if ( status == ARES_SUCCESS )

  {

    /* We got our answer.  Allocate memory to build the host entry. */

    nameservers[nameservers_num] = NULL;

    hostent = ares_malloc( sizeof( struct hostent ) );

    if ( hostent )

    {

      hostent->h_addr_list = ares_malloc( 1 * sizeof( char * ) );

      if ( hostent->h_addr_list )

      {

        /* Fill in the hostent and return successfully. */

        hostent->h_name = hostname;

        hostent->h_aliases = nameservers;

        hostent->h_addrtype = AF_INET;

        hostent->h_length = sizeof( struct in_addr );

        hostent->h_addr_list[0] = NULL;

        *host = hostent;

        return ARES_SUCCESS;

      }

      ares_free( hostent );

    }

    status = ARES_ENOMEM;

  }

  for ( i = 0; i < nameservers_num; i++ )

    ares_free( nameservers[i] );

  ares_free( nameservers );

  ares_free( hostname );

  return status;

}