A Ruby port of Charlie Miller's infamous 5 line Python dumb fuzzer

miller-fuzz.rb

#!/usr/bin/env ruby
#
# A Ruby port of Charlie Miller's infamous 5 line Python dumb fuzzer
# ~ bcoles

=begin
# Original Python code:
numwrites = random.randrange(math.ceil((float(len(buf)) / FuzzFactor))) + 1
for j in range(numwrites):
  rbyte = random.randrange(256)
  rn = random.randrange(len(buf))
  buf[rn] = "%c"%(rbyte)
=end

require 'securerandom'

infile = '/path/to/in_file'
outfile = '/path/to/out_file'

data = IO.binread infile
fuzz_factor = 250
num_writes = SecureRandom.random_number((data.size / fuzz_factor.to_f).ceil) + 1

new_data = data.dup
num_writes.times do
  position = SecureRandom.random_number data.size
  new_byte = SecureRandom.random_number 256
  new_data.tap { |stream| stream.setbyte position, new_byte }
end

File.open(outfile, 'w') do |file|
  file.write new_data
end