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libip.packet.dns.cpp

/*
 * Copyright (c) 2007
 *      Shrew Soft Inc.  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.
 * 3. Redistributions in any form must be accompanied by information on
 *    how to obtain complete source code for the software and any
 *    accompanying software that uses the software.  The source code
 *    must either be included in the distribution or be available for no
 *    more than the cost of distribution plus a nominal fee, and must be
 *    freely redistributable under reasonable conditions.  For an
 *    executable file, complete source code means the source code for all
 *    modules it contains.  It does not include source code for modules or
 *    files that typically accompany the major components of the operating
 *    system on which the executable file runs.
 *
 * THIS SOFTWARE IS PROVIDED BY SHREW SOFT INC ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
 * NON-INFRINGEMENT, ARE DISCLAIMED.  IN NO EVENT SHALL SHREW SOFT INC
 * 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.
 *
 * AUTHOR : Matthew Grooms
 *          mgrooms@shrew.net
 *
 */

#include "libip.h"

#include <stdio.h>

#define MAX_DNS_NAME    255

PACKET_DNS::_PACKET_DNS()
{
      ident = 0;
      flags = 0;
      ques  = 0;
      answ  = 0;
      ath_rr      = 0;
      add_rr      = 0;
}

PACKET_DNS::~_PACKET_DNS()
{
      DNS_QUERY * query;
      DNS_RECORD * record;

      long index = 0;
      long count = list_ques.get_count();

      for( ; index < count; index++ )
      {
            query = ( DNS_QUERY * ) list_ques.get_item( index );
            delete query;
      }

      index = 0;
      count = list_answ.get_count();

      for( ; index < count; index++ )
      {
            record = ( DNS_RECORD * ) list_answ.get_item( index );
            delete record;
      }

      index = 0;
      count = list_ath_rr.get_count();

      for( ; index < count; index++ )
      {
            record = ( DNS_RECORD * ) list_ath_rr.get_item( index );
            delete record;
      }

      index = 0;
      count = list_add_rr.get_count();

      for( ; index < count; index++ )
      {
            record = ( DNS_RECORD * ) list_add_rr.get_item( index );
            delete record;
      }
}

bool PACKET_DNS::read_name( char * name, long & size )
{
      uint8_t     tag1;
      uint8_t     tag2;
      long  oset = 0;

      //
      // reserve room for our null char
      //

      size--;

      //
      // step through all sequence tags
      //

      while( get_byte( tag1 ) )
      {
            //
            // is this a reserved value
            //

            if( ( ( tag1 & 0xc0 ) == 0x80 ) ||
                  ( ( tag1 & 0xc0 ) == 0x40 ) )
                  break;

            //
            // is this an end tag
            //

            if( tag1 == 0 )
            {
                  //
                  // end of our segment, null
                  // terminate and return
                  //

                  name[ oset ] = 0;
                  return true;
            }

            //
            // append a period if neccessary
            //

            if( oset )
            {
                  if( size < 1 )
                  break;

                  name[ oset ] = '.';
                  oset++;
                  size--;
            }

            //
            // is this a name segment or
            // name segment pointer
            //
            if( ( tag1 & 0xc0 ) == 0xc0 )
            {
                  size_t tmp_oset = 0;
                  size_t new_oset = 0;

                  //
                  // its a pointer, recurse
                  //

                  if( !get_byte( tag2 ) )
                        break;

                  new_oset |= ( tag1 & 0x3f );
                  new_oset <<= 8;
                  new_oset |= tag2;

                  if( new_oset >= data_size )
                        break;

                  tmp_oset = data_oset;
                  data_oset = new_oset;

                  bool rslt = read_name( name + oset, size );

                  data_oset = tmp_oset;

                  if( rslt )
                        return true;
            }
            else
            {
                  //
                  // its a segment, append
                  //

                  long temp = tag1;
                  if( temp >= size )
                        break;

                  if( !get( &name[ oset ], temp ) )
                        break;

                  oset += temp;
                  size -= temp;
            }
      }

      return false;
}

bool PACKET_DNS::read_query( DNS_QUERY ** query )
{
      //
      // read the name
      //

      char name_data[ MAX_DNS_NAME ];
      long name_size = MAX_DNS_NAME;

      if( !read_name( name_data, name_size ) )
            return false;

      uint16_t type;
      if( !get_word( type ) )
            return false;

      uint16_t clss;
      if( !get_word( clss ) )
            return false;

      //
      // create our query struct
      //

      DNS_QUERY * tmp_query = new DNS_QUERY;
      if( tmp_query == NULL )
            return false;

      tmp_query->name = new char[ name_size + 1 ];
      memcpy( tmp_query->name, name_data, name_size );
      tmp_query->name[ name_size ] = 0;
      tmp_query->type = type;
      tmp_query->clss = clss;

      *query = tmp_query;

      return true;
}

bool PACKET_DNS::read_record( DNS_RECORD ** record )
{
      //
      // read the name
      //

      char name_data[ MAX_DNS_NAME ];
      long name_size = MAX_DNS_NAME;

      if( !read_name( name_data, name_size ) )
            return false;

      uint16_t type;
      if( !get_word( type ) )
            return false;

      uint16_t clss;
      if( !get_word( clss ) )
            return false;

      uint32_t rttl;
      if( !get_quad( rttl ) )
            return false;

      uint16_t rlen;
      if( !get_word( rlen ) )
            return false;

      get_null( rlen );

      //
      // create our record struct
      //

      DNS_RECORD * tmp_record = new DNS_RECORD;
      if( tmp_record == NULL )
            return false;

      tmp_record->name = new char[ name_size + 1 ];
      memcpy( tmp_record->name, name_data, name_size );
      tmp_record->name[ name_size ] = 0;
      tmp_record->type = type;
      tmp_record->clss = clss;
      tmp_record->rttl = rttl;
      tmp_record->rlen = rlen;

      *record = tmp_record;

      return true;
}

bool PACKET_DNS::read()
{
      //
      // read the header
      //

      DNS_HEADER dns_head;
      if( !get( &dns_head, sizeof( dns_head ) ) )
            return false;

      ident = ntohs( dns_head.ident );
      flags = ntohs( dns_head.flags );
      ques  = ntohs( dns_head.ques );
      answ  = ntohs( dns_head.answ );
      ath_rr      = ntohs( dns_head.ath_rr );
      add_rr      = ntohs( dns_head.add_rr );

      //
      // read question section
      //

      long index;

      for( index = 0; index < ques; index++ )
      {
            DNS_QUERY * query;
            if( !read_query( &query ) )
                  return false;

            list_ques.add_item( query );
      }

      //
      // read answer section
      //

      for( index = 0; index < answ; index++ )
      {
            DNS_RECORD * record;
            if( !read_record( &record ) )
                  return false;

            list_answ.add_item( record );
      }

      //
      // authoritative section
      //

      for( index = 0; index < ath_rr; index++ )
      {
            DNS_RECORD * record;
            if( !read_record( &record ) )
                  return false;

            list_ath_rr.add_item( record );
      }

      //
      // additional section
      //

      for( index = 0; index < add_rr; index++ )
      {
            DNS_RECORD * record;
            if( !read_record( &record ) )
                  return false;

            list_add_rr.add_item( record );
      }

      return true;
}

bool PACKET_DNS::write()
{
      return true;
}

bool PACKET_DNS::get_question( DNS_QUERY ** query, long index )
{
      *query = ( DNS_QUERY * ) list_ques.get_item( index );
      return ( *query != NULL );
}

bool PACKET_DNS::get_answer( DNS_RECORD ** record, long index )
{
      *record = ( DNS_RECORD * ) list_answ.get_item( index );
      return ( *record != NULL );
}

bool PACKET_DNS::get_authority( DNS_RECORD ** record, long index )
{
      *record = ( DNS_RECORD * ) list_ath_rr.get_item( index );
      return ( *record != NULL );
}

bool PACKET_DNS::get_additional( DNS_RECORD ** record, long index )
{
      *record = ( DNS_RECORD * ) list_add_rr.get_item( index );
      return ( *record != NULL );
}


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