Class: PacketFu::TCPHeader

Inherits:
Struct
  • Object
show all
Includes:
StructFu
Defined in:
lib/packetfu/protos/tcp/header.rb

Overview

TCPHeader is a complete TCP struct, used in TCPPacket. Most IP traffic is TCP-based, by volume.

For more on TCP packets, see www.networksorcery.com/enp/protocol/tcp.htm

Header Definition

Int16        :tcp_src       Default: random 
Int16        :tcp_dst
Int32        :tcp_seq       Default: random
Int32        :tcp_ack
TcpHlen      :tcp_hlen      Default: 5           # Must recalc as options are set. 
TcpReserved  :tcp_reserved  Default: 0
TcpEcn       :tcp_ecn
TcpFlags     :tcp_flags
Int16        :tcp_win,      Default: 0           # WinXP's default syn packet
Int16        :tcp_sum,      Default: calculated  # Must set this upon generation.
Int16        :tcp_urg
TcpOptions   :tcp_opts
String       :body

See also TcpHlen, TcpReserved, TcpEcn, TcpFlags, TcpOpts

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from StructFu

#clone, #set_endianness, #sz, #typecast

Methods inherited from Struct

#force_binary

Constructor Details

#initialize(args = {}) ⇒ TCPHeader

Returns a new instance of TCPHeader.



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# File 'lib/packetfu/protos/tcp/header.rb', line 41

def initialize(args={})
  @random_seq = rand(0xffffffff)
  @random_src = rand_port
  super(
    Int16.new(args[:tcp_src] || tcp_calc_src),
    Int16.new(args[:tcp_dst]),
    Int32.new(args[:tcp_seq] || tcp_calc_seq),
    Int32.new(args[:tcp_ack]),
    TcpHlen.new(:hlen => (args[:tcp_hlen] || 5)),
    TcpReserved.new(args[:tcp_reserved] || 0),
    TcpEcn.new(args[:tcp_ecn]),
    TcpFlags.new(args[:tcp_flags]),
    Int16.new(args[:tcp_win] || 0x4000),
    Int16.new(args[:tcp_sum] || 0),
    Int16.new(args[:tcp_urg]),
    TcpOptions.new.read(args[:tcp_opts]),
    StructFu::String.new.read(args[:body])
  )
end

Instance Attribute Details

#body ⇒ Object

Returns the value of attribute body

Returns:

  • (Object) —

    the current value of body



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def body
  @body
end

#flavor ⇒ Object

Returns the value of attribute flavor.



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# File 'lib/packetfu/protos/tcp/header.rb', line 61

def flavor
  @flavor
end

#tcp_ack ⇒ Object

Getter for the TCP ackowlegement number.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_ack
  @tcp_ack
end

#tcp_dst ⇒ Object

Getter for the TCP destination port.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_dst
  @tcp_dst
end

#tcp_ecn ⇒ Object

Getter for the ECN bits.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_ecn
  @tcp_ecn
end

#tcp_flags ⇒ Object

Returns the value of attribute tcp_flags

Returns:

  • (Object) —

    the current value of tcp_flags



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_flags
  @tcp_flags
end

#tcp_hlen ⇒ Object

Getter for the TCP Header Length value.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_hlen
  @tcp_hlen
end

#tcp_opts ⇒ Object

Getter for TCP Options.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_opts
  @tcp_opts
end

#tcp_reserved ⇒ Object

Getter for the TCP Reserved field.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_reserved
  @tcp_reserved
end

#tcp_seq ⇒ Object

Getter for the TCP sequence number.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_seq
  @tcp_seq
end

#tcp_src ⇒ Object

Getter for the TCP source port.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_src
  @tcp_src
end

#tcp_sum ⇒ Object

Getter for the TCP checksum.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_sum
  @tcp_sum
end

#tcp_urg ⇒ Object

Getter for the TCP urgent field.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_urg
  @tcp_urg
end

#tcp_win ⇒ Object

Getter for the TCP window size number.



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# File 'lib/packetfu/protos/tcp/header.rb', line 33

def tcp_win
  @tcp_win
end

Instance Method Details

#bits_to_s ⇒ Object

Helper function to create the string for Hlen, Reserved, ECN, and Flags.



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# File 'lib/packetfu/protos/tcp/header.rb', line 64

def bits_to_s
  bytes = []
  bytes[0] = (self[:tcp_hlen].to_i << 4) +
    (self[:tcp_reserved].to_i << 1) +
    self[:tcp_ecn].n.to_i
  bytes[1] = (self[:tcp_ecn].c.to_i << 7) +
    (self[:tcp_ecn].e.to_i << 6) +
    self[:tcp_flags].to_i
  bytes.pack("CC")
end

#rand_port ⇒ Object

Generates a random high port. This is affected by packet flavor.



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# File 'lib/packetfu/protos/tcp/header.rb', line 223

def rand_port
  rand(0xffff - 1025) + 1025
end

#read(str) ⇒ Object

Reads a string to populate the object.



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# File 'lib/packetfu/protos/tcp/header.rb', line 94

def read(str)
  force_binary(str)
  return self if str.nil?
  self[:tcp_src].read(str[0,2])
  self[:tcp_dst].read(str[2,2])
  self[:tcp_seq].read(str[4,4])
  self[:tcp_ack].read(str[8,4])
  self[:tcp_hlen].read(str[12,1])
  self[:tcp_reserved].read(str[12,1])
  self[:tcp_ecn].read(str[12,2])
  self[:tcp_flags].read(str[13,1])
  self[:tcp_win].read(str[14,2])
  self[:tcp_sum].read(str[16,2])
  self[:tcp_urg].read(str[18,2])
  self[:tcp_opts].read(str[20,((self[:tcp_hlen].to_i * 4) - 20)])
  self[:body].read(str[(self[:tcp_hlen].to_i * 4),str.size])
  self
end

#tcp_ack_readable ⇒ Object 



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# File 'lib/packetfu/protos/tcp/header.rb', line 290

def tcp_ack_readable
  "0x%08x" % tcp_ack
end

#tcp_calc_hlen ⇒ Object

Sets and returns the true length of the TCP Header. TODO: Think about making all the option stuff safer.



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# File 'lib/packetfu/protos/tcp/header.rb', line 218

def tcp_calc_hlen
  self[:tcp_hlen] = TcpHlen.new(:hlen => ((20 + tcp_opts_len) / 4))
end

#tcp_calc_seq ⇒ Object

Resets the sequence number to a new random number.



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# File 'lib/packetfu/protos/tcp/header.rb', line 207

def tcp_calc_seq; @random_seq; end

#tcp_calc_src ⇒ Object

Resets the source port to a new random number.



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# File 'lib/packetfu/protos/tcp/header.rb', line 209

def tcp_calc_src; @random_src; end

#tcp_dport ⇒ Object

Equivalent to tcp_dst.



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# File 'lib/packetfu/protos/tcp/header.rb', line 257

def tcp_dport
  self.tcp_dst.to_i
end

#tcp_dport=(arg) ⇒ Object

Equivalent to tcp_dst=.



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# File 'lib/packetfu/protos/tcp/header.rb', line 262

def tcp_dport=(arg)
  self.tcp_dst=(arg)
end

#tcp_flags_dotmap ⇒ Object Also known as: tcp_flags_readable

Gets a more readable flags list



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# File 'lib/packetfu/protos/tcp/header.rb', line 233

def tcp_flags_dotmap
  dotmap = tcp_flags.members.map do |flag|
    status = self.tcp_flags.send flag
    status == 0 ? "." : flag.to_s.upcase[0].chr
  end
  dotmap.join
end

#tcp_options ⇒ Object

Gets a more readable option list.



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# File 'lib/packetfu/protos/tcp/header.rb', line 228

def tcp_options
 self[:tcp_opts].decode
end

#tcp_options=(arg) ⇒ Object

Sets a more readable option list.



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# File 'lib/packetfu/protos/tcp/header.rb', line 242

def tcp_options=(arg)
  self[:tcp_opts].encode arg
end

#tcp_opts_len ⇒ Object

Returns the actual length of the TCP options.



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# File 'lib/packetfu/protos/tcp/header.rb', line 212

def tcp_opts_len
  self[:tcp_opts].to_s.size
end

#tcp_opts_readable ⇒ Object 



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# File 'lib/packetfu/protos/tcp/header.rb', line 302

def tcp_opts_readable
  tcp_options
end

#tcp_recalc(arg = :all) ⇒ Object

Recalculates calculated fields for TCP (except checksum which is at the Packet level).



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# File 'lib/packetfu/protos/tcp/header.rb', line 267

def tcp_recalc(arg=:all)
  case arg
  when :tcp_hlen
    tcp_calc_hlen
  when :tcp_src
    @random_tcp_src = rand_port
  when :tcp_sport
    @random_tcp_src = rand_port
  when :tcp_seq
    @random_tcp_seq = rand(0xffffffff) 
  when :all
    tcp_calc_hlen
    @random_tcp_src = rand_port
    @random_tcp_seq = rand(0xffffffff) 
  else
    raise ArgumentError, "No such field `#{arg}'"
  end
end

#tcp_seq_readable ⇒ Object 



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# File 'lib/packetfu/protos/tcp/header.rb', line 294

def tcp_seq_readable
  "0x%08x" % tcp_seq
end

#tcp_sport ⇒ Object

Equivalent to tcp_src.



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# File 'lib/packetfu/protos/tcp/header.rb', line 247

def tcp_sport
  self.tcp_src.to_i
end

#tcp_sport=(arg) ⇒ Object

Equivalent to tcp_src=.



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# File 'lib/packetfu/protos/tcp/header.rb', line 252

def tcp_sport=(arg)
  self.tcp_src=(arg)
end

#tcp_sum_readable ⇒ Object 



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# File 'lib/packetfu/protos/tcp/header.rb', line 298

def tcp_sum_readable
  "0x%04x" % tcp_sum
end

#to_s ⇒ Object

Returns the object in string form.



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# File 'lib/packetfu/protos/tcp/header.rb', line 76

def to_s
  hdr = self.to_a.map do |x|
    if x.kind_of? TcpHlen
      bits_to_s
    elsif x.kind_of? TcpReserved
      next
    elsif x.kind_of? TcpEcn
      next
    elsif x.kind_of? TcpFlags
      next
    else
      x.to_s
    end
  end
  hdr.flatten.join
end