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# -*- coding: binary -*-
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require 'socket'
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require 'ipaddr'
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class RawSocket # :nodoc:
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  @@id_arr = []
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  def initialize(src_addr,dest_addr)
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    # Define socket
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    begin
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      @socket = Socket.new PF_INET, SOCK_RAW, IPPROTO_RAW
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    rescue SystemCallError => e
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      raise SystemCallError, "You must be root to use raw sockets! #{e}"
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    end
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    @socket.setsockopt IPPROTO_IP, IP_HDRINCL, 1
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    # Checks addresses
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    @src_addr  = check_addr src_addr
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    @dest_addr = check_addr dest_addr
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    # Source and destination port are zero
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    @src_port  = 0
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    @dest_port = 0
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    # Set correct protocol version in the header
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    @version = @dest_addr.ipv4? ? "0100" : "0110"
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    # Total length: must be overridden by subclasses
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    @tot_lenght = 20
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    # Protocol: must be overridden by subclasses
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    @protocol = 1 # ICMP by default
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    # Generate a new id
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    # @id = genID
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    @id = 1234
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    # Generate peer sockaddr
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    @to = Socket.pack_sockaddr_in @dest_port, @dest_addr.to_s    
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  end
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  def send(payload = '')
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    packet = make_ip_header([[ @version+'0101', 'B8' ],            # version, hlen
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                              [ 0, 'C' ],                          # tos
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                              [ @tot_lenght + payload.size, 'n' ], # total len
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                              [ @id, 'n' ],                        # id
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                              [ 0, 'n' ],                          # flags, offset
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                              [ 64, 'C' ],                         # ttl
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                              [ @protocol, 'C' ],                  # protocol
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                              [ 0, 'n' ],                          # checksum
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                              [ @src_addr.to_i, 'N' ],             # source
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                              [ @dest_addr.to_i, 'N' ],            # destination
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                            ])
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    packet << make_transport_header(payload.size)
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    packet << [payload].pack("a*")
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    @socket.send(packet,0,@to)
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  end 
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  private
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  def check_addr addr
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    case addr
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    when String
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      IPAddr.new addr
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    when IPAddr
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      addr
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    else
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      raise ArgumentError, "Wrong address format: #{addr}"
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    end
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  end
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  def check_port port
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    if (1..65535).include? port and port.kind_of? Integer
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      port
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    else
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      raise ArgumentError, "Port #{port} not valid"
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    end
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  end
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  def genID
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    while (@@id_arr.include?(q = rand(65535)))
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    end
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    @@id_arr.push(q)
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    q
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  end
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  def ipchecksum(data)
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    checksum = data.unpack("n*").inject(0) { |s, x| s + x }
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    ((checksum >> 16) + (checksum & 0xffff)) ^ 0xffff
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  end
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  def make_ip_header(parts)
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    template = ''
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    data = []
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    parts.each do |part|
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      data += part[0..-2]
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      template << part[-1]
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    end
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    data_str = data.pack(template)
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    checksum = ipchecksum(data_str)
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    data[-3] = checksum
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    data.pack(template)
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  end
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  def make_transport_header
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    ""
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  end
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end
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class UdpRawSocket < RawSocket # :nodoc:
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  def initialize(src_addr,src_port,dest_addr,dest_port)
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    super(src_addr,dest_addr)
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    # Check ports
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    @src_port  = check_port src_port
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    @dest_port = check_port dest_port
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    # Total length: must be overridden by subclasses
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    @tot_lenght = 20 + 8 # 8 bytes => UDP Header
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    # Protocol: must be overridden by subclasses
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    @protocol = 17 # UDP protocol
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    @to = Socket.pack_sockaddr_in @dest_port, @dest_addr.to_s    
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  end
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  private
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  def make_udp_header(parts)
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    template = ''
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    data = []
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    parts.each do |part|
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      data += part[0..-2]
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      template << part[-1]
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    end
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    data.pack(template)
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  end 
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  def make_transport_header(pay_size)
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    make_udp_header([
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                      [ @src_port, 'n'],         # source port
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                      [ @dest_port, 'n' ],       # destination port
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                      [ 8 + pay_size, 'n' ],     # len
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                      [ 0, 'n' ]                 # checksum (mandatory)
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                    ]) 
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  end
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end
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