Class: Syspy::TdsPackageStream

Inherits:
Object
  • Object
show all
Defined in:
lib/tds_package_stream.rb

Instance Method Summary collapse

Constructor Details

#initialize(interface, dst, dst_port) ⇒ TdsPackageStream 



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# File 'lib/tds_package_stream.rb', line 10

def initialize(interface,dst,dst_port)
  @interface = interface
  @dst = dst
  @dst_port = dst_port
  @in,@out = IO.pipe()
end

Instance Method Details

#each_package ⇒ Object 



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# File 'lib/tds_package_stream.rb', line 17

def each_package()
  Thread.abort_on_exception = true       
  @tcpdump_thread = Thread.new(){       
    IO.popen("tcpdump -q -y EN10MB -U -B #{1024 * 1024} -w - -i #{@interface} tcp and dst #{@dst} and dst port #{@dst_port} 2>/dev/null"){|io|         
      content = ""
      loop(){
        tcp_length = read_ip_header(io)
        Log.debug "Got IP package: #{tcp_length}"
        content_length = read_tcp_header(io,tcp_length)
        Log.debug "Got TCP package: #{content_length}"
        
        if(content_length > 0)        
          content = io.read(content_length)       
          @out.write(content)
          @out.flush      
        end

        Log.debug "Network package done"      
      } 
    }
  }  

  content = ""
  @in.each_byte(){|byte|
    if(byte == 0x0F)                 
      last_packet_indicator = Bytes.uint(@in)          
      length = Bytes.uint16be(@in)
       
      # skip next 4 bytes of the header
      if(Bytes.uint32be(@in) == 0x00)
        content << @in.read(length - 8)
        
        if(last_packet_indicator == 0x1)              
          begin
            io = StringIO.new(content)
            package = handle_package(io)
            yield package if package               
          ensure
            content = ""
          end             
        end
      end
    end           
  }     
end

#handle_package(io) ⇒ Object 



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# File 'lib/tds_package_stream.rb', line 63

def handle_package(io)    
  token = io.readchar()
  token_class = TdsTokens.token_class(token)
  if(token_class)
    length = TdsTokens.fixed_length(token)
    unless(length)
      length_field_size = TdsTokens.length_field_size(token)
      if(length_field_size)
        length = Bytes.uintle(io,length_field_size)
      end       
    end
    Log.debug("Got #{TdsTokens.token_name(token)} of #{length} bytes")
    package = token_class.new(io,length)
    return package        
  end
  nil   
end

#read_ip_header(io) ⇒ Object 



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# File 'lib/tds_package_stream.rb', line 81

def read_ip_header(io)
  count = 0
  loop(){
    network_type = Bytes.uint16be(io)
    break if network_type == 0x800 and count >= 14
    count += 1 
  }    

  # read IP version and header length
  ver_len = io.readchar()
  version = ver_len >> 4
   
  raise "Invalid IP version: #{version}" unless version == 4 || version == 6

  header_length = (ver_len & 0x0F) * 4
   
  # skip TOS
  io.readchar()
   
  # get package length
  content_length = Bytes.uint16be(io)

  # consume remaining IP header
  io.read(header_length - 4)
  content_length - header_length
end

#read_tcp_header(io, ip_package_size) ⇒ Object 



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# File 'lib/tds_package_stream.rb', line 108

def read_tcp_header(io, ip_package_size)
  # skip first 12
  io.read(12)

  # get header length
  tcp_offset = (io.readchar() >> 4) * 4
   
  # consume remaining tcp header
  io.read(tcp_offset - 13)
  
  ip_package_size - tcp_offset
end