module SecureRandom

Secure random number generator interface.¶ ↑

This library is an interface to secure random number generators which are suitable for generating session keys in HTTP cookies, etc.

You can use this library in your application by requiring it:

require 'securerandom'

It supports the following secure random number generators:

openssl
/dev/urandom
Win32

SecureRandom is extended by the Random::Formatter module which defines the following methods:

alphanumeric
base64
choose
gen_random
hex
rand
random_bytes
random_number
urlsafe_base64
uuid

These methods are usable as class methods of SecureRandom such as ‘SecureRandom.hex`.

Examples¶ ↑

Generate random hexadecimal strings:

require 'securerandom'

SecureRandom.hex(10) #=> "52750b30ffbc7de3b362"
SecureRandom.hex(10) #=> "92b15d6c8dc4beb5f559"
SecureRandom.hex(13) #=> "39b290146bea6ce975c37cfc23"

Generate random base64 strings:

SecureRandom.base64(10) #=> "EcmTPZwWRAozdA=="
SecureRandom.base64(10) #=> "KO1nIU+p9DKxGg=="
SecureRandom.base64(12) #=> "7kJSM/MzBJI+75j8"

Generate random binary strings:

SecureRandom.random_bytes(10) #=> "\016\t{\370g\310pbr\301"
SecureRandom.random_bytes(10) #=> "\323U\030TO\234\357\020\a\337"

Generate alphanumeric strings:

SecureRandom.alphanumeric(10) #=> "S8baxMJnPl"
SecureRandom.alphanumeric(10) #=> "aOxAg8BAJe"

Generate UUIDs:

SecureRandom.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
SecureRandom.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"

Public Class Methods

bytes(n) click to toggle source

# File securerandom.rb, line 71
def bytes(n)
  return gen_random(n)
end

gen_random(n) click to toggle source

# File securerandom.rb, line 75
def gen_random(n)
  ret = Random.urandom(1)
  if ret.nil?
    begin
      require 'openssl'
    rescue NoMethodError
      raise NotImplementedError, "No random device"
    else
      @rng_chooser.synchronize do
        class << self
          remove_method :gen_random
          alias gen_random gen_random_openssl
          public :gen_random
        end
      end
      return gen_random(n)
    end
  else
    @rng_chooser.synchronize do
      class << self
        remove_method :gen_random
        alias gen_random gen_random_urandom
        public :gen_random
      end
    end
    return gen_random(n)
  end
end

Private Class Methods

gen_random_openssl(n) click to toggle source

# File securerandom.rb, line 106
def gen_random_openssl(n)
  @pid = 0 unless defined?(@pid)
  pid = $$
  unless @pid == pid
    now = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)
    OpenSSL::Random.random_add([now, @pid, pid].join(""), 0.0)
    seed = Random.urandom(16)
    if (seed)
      OpenSSL::Random.random_add(seed, 16)
    end
    @pid = pid
  end
  return OpenSSL::Random.random_bytes(n)
end

Also aliased as: gen_random

gen_random_urandom(n) click to toggle source

# File securerandom.rb, line 121
def gen_random_urandom(n)
  ret = Random.urandom(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

Also aliased as: gen_random