Module: SecureRandom

Defined in:
lib/securerandom.rb

Class Method Summary (collapse)

Class Method Details

+ (Object) base64(n = nil)

SecureRandom.base64 generates a random base64 string.

The argument n specifies the length of the random length. The length of the result string is about 4/3 of n.

If n is not specified, 16 is assumed. It may be larger in future.

The result may contain A-Z, a-z, 0-9, “+”, “/” and “=”. 

  p SecureRandom.base64 #=> "/2BuBuLf3+WfSKyQbRcc/A=="
  p SecureRandom.base64 #=> "6BbW0pxO0YENxn38HMUbcQ=="

If secure random number generator is not available, NotImplementedError is raised.

See RFC 3548 for base64. 



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

def self.base64(n=nil)
  [random_bytes(n)].pack("m*").delete("\n")
end

+ (Object) hex(n = nil)

SecureRandom.hex generates a random hex string.

The argument n specifies the length of the random length. The length of the result string is twice of n.

If n is not specified, 16 is assumed. It may be larger in future.

The result may contain 0-9 and a-f. 

  p SecureRandom.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
  p SecureRandom.hex #=> "91dc3bfb4de5b11d029d376634589b61"

If secure random number generator is not available, NotImplementedError is raised. 



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# File 'lib/securerandom.rb', line 131

def self.hex(n=nil)
  random_bytes(n).unpack("H*")[0]
end

+ (Object) lastWin32ErrorMessage

Following code is based on David Garamond’s GUID library for Ruby. 



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# File 'lib/securerandom.rb', line 246

def self.lastWin32ErrorMessage # :nodoc:
  get_last_error = Win32API.new("kernel32", "GetLastError", '', 'L')
  format_message = Win32API.new("kernel32", "FormatMessageA", 'LPLLPLPPPPPPPP', 'L')
  format_message_ignore_inserts = 0x00000200
  format_message_from_system    = 0x00001000

  code = get_last_error.call
  msg = "\0" * 1024
  len = format_message.call(format_message_ignore_inserts + format_message_from_system, 0, code, 0, msg, 1024, nil, nil, nil, nil, nil, nil, nil, nil)
  msg[0, len].tr("\r", '').chomp
end

+ (Object) random_bytes(n = nil)

SecureRandom.random_bytes generates a random binary string.

The argument n specifies the length of the result string.

If n is not specified, 16 is assumed. It may be larger in future.

The result may contain any byte: “\x00” - “\xff”. 

  p SecureRandom.random_bytes #=> "\xD8\\\xE0\xF4\r\xB2\xFC*WM\xFF\x83\x18\xF45\xB6"
  p SecureRandom.random_bytes #=> "m\xDC\xFC/\a\x00Uf\xB2\xB2P\xBD\xFF6S\x97"

If secure random number generator is not available, NotImplementedError is raised.

Raises:

  • (NotImplementedError) 


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# File 'lib/securerandom.rb', line 56

def self.random_bytes(n=nil)
  n ||= 16

  if defined? OpenSSL::Random
    return OpenSSL::Random.random_bytes(n)
  end

  if !defined?(@has_urandom) || @has_urandom
    flags = File::RDONLY
    flags |= File::NONBLOCK if defined? File::NONBLOCK
    flags |= File::NOCTTY if defined? File::NOCTTY
    begin
      File.open("/dev/urandom", flags) {|f|
        unless f.stat.chardev?
          raise Errno::ENOENT
        end
        @has_urandom = true
        ret = f.readpartial(n)
        if ret.length != n
          raise NotImplementedError, "Unexpected partial read from random device"
        end
        return ret
      }
    rescue Errno::ENOENT
      @has_urandom = false
    end
  end

  if !defined?(@has_win32)
    begin
      require 'Win32API'

      crypt_acquire_context = Win32API.new("advapi32", "CryptAcquireContext", 'PPPII', 'L')
      @crypt_gen_random = Win32API.new("advapi32", "CryptGenRandom", 'LIP', 'L')

      hProvStr = " " * 4
      prov_rsa_full = 1
      crypt_verifycontext = 0xF0000000

      if crypt_acquire_context.call(hProvStr, nil, nil, prov_rsa_full, crypt_verifycontext) == 0
        raise SystemCallError, "CryptAcquireContext failed: #{lastWin32ErrorMessage}"
      end
      @hProv, = hProvStr.unpack('L')

      @has_win32 = true
    rescue LoadError
      @has_win32 = false
    end
  end
  if @has_win32
    bytes = " ".force_encoding("ASCII-8BIT") * n
    if @crypt_gen_random.call(@hProv, bytes.size, bytes) == 0
      raise SystemCallError, "CryptGenRandom failed: #{lastWin32ErrorMessage}"
    end
    return bytes
  end

  raise NotImplementedError, "No random device"
end

+ (Object) random_number(n = 0)

SecureRandom.random_number generates a random number.

If an positive integer is given as n, SecureRandom.random_number returns an integer: 0 <= SecureRandom.random_number(n) < n. 

  p SecureRandom.random_number(100) #=> 15
  p SecureRandom.random_number(100) #=> 88

If 0 is given or an argument is not given, SecureRandom.random_number returns an float: 0.0 <= SecureRandom.random_number() < 1.0. 

  p SecureRandom.random_number #=> 0.596506046187744
  p SecureRandom.random_number #=> 0.350621695741409



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# File 'lib/securerandom.rb', line 206

def self.random_number(n=0)
  if 0 < n
    hex = n.to_s(16)
    hex = '0' + hex if (hex.length & 1) == 1
    bin = [hex].pack("H*")
    mask = bin[0].ord
    mask |= mask >> 1
    mask |= mask >> 2
    mask |= mask >> 4
    begin
      rnd = SecureRandom.random_bytes(bin.length)
      rnd[0] = (rnd[0].ord & mask).chr
    end until rnd < bin
    rnd.unpack("H*")[0].hex
  else
    # assumption: Float::MANT_DIG <= 64
    i64 = SecureRandom.random_bytes(8).unpack("Q")[0]
    Math.ldexp(i64 >> (64-Float::MANT_DIG), -Float::MANT_DIG)
  end
end

+ (Object) urlsafe_base64(n = nil, padding = false)

SecureRandom.urlsafe_base64 generates a random URL-safe base64 string.

The argument n specifies the length of the random length. The length of the result string is about 4/3 of n.

If n is not specified, 16 is assumed. It may be larger in future.

The boolean argument padding specifies the padding. If it is false or nil, padding is not generated. Otherwise padding is generated. By default, padding is not generated because “=” may be used as a URL delimiter.

The result may contain A-Z, a-z, 0-9, “-” and “_”. “=” is also used if padding is true. 

  p SecureRandom.urlsafe_base64 #=> "b4GOKm4pOYU_-BOXcrUGDg"
  p SecureRandom.urlsafe_base64 #=> "UZLdOkzop70Ddx-IJR0ABg"

  p SecureRandom.urlsafe_base64(nil, true) #=> "i0XQ-7gglIsHGV2_BNPrdQ=="
  p SecureRandom.urlsafe_base64(nil, true) #=> "-M8rLhr7JEpJlqFGUMmOxg=="

If secure random number generator is not available, NotImplementedError is raised.

See RFC 3548 for URL-safe base64. 



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# File 'lib/securerandom.rb', line 182

def self.urlsafe_base64(n=nil, padding=false)
  s = [random_bytes(n)].pack("m*")
  s.delete!("\n")
  s.tr!("+/", "-_")
  s.delete!("=") if !padding
  s
end

+ (Object) uuid

SecureRandom.uuid generates a v4 random UUID (Universally Unique IDentifier). 

  p SecureRandom.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
  p SecureRandom.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
  p SecureRandom.uuid #=> "62936e70-1815-439b-bf89-8492855a7e6b"

The version 4 UUID is purely random (except the version). It doesn’t contain meaningful information such as MAC address, time, etc.

See RFC 4122 for details of UUID. 



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# File 'lib/securerandom.rb', line 238

def self.uuid
  ary = self.random_bytes(16).unpack("NnnnnN")
  ary[2] = (ary[2] & 0x0fff) | 0x4000
  ary[3] = (ary[3] & 0x3fff) | 0x8000
  "%08x-%04x-%04x-%04x-%04x%08x" % ary
end