Ruby Bug: SecureRandom should try /dev/urandom first(bugs.ruby-lang.org)

  require "securerandom"

  module SecureRandom
    F = File.open("/dev/urandom")

    def self.random_bytes(n = nil)
      F.read(n || 16)
    end
  end

    def SecureRandom.gen_random(n)
      ret = Random.raw_seed(n)
      unless ret
        raise NotImplementedError, "No random device"
      end
      unless ret.length == n
        raise NotImplementedError, "Unexpected partial read from random device: only #{ret.length} for #{n} bytes"
      end
      ret
    end