Secure random number generator interface.
This library is an interface for secure random number generator which is suitable for generating session key in HTTP cookies, etc.
It supports following secure random number generators.
-
openssl
-
/dev/urandom
-
Win32
Note: This module is based on the SecureRandom library from Ruby 1.9, revision 18786, August 23 2008. It’s 100% interface-compatible with Ruby 1.9’s SecureRandom library.
Example
# random hexadecimal string. p SecureRandom.hex(10) # => "52750b30ffbc7de3b362" p SecureRandom.hex(10) # => "92b15d6c8dc4beb5f559" p SecureRandom.hex(11) # => "6aca1b5c58e4863e6b81b8" p SecureRandom.hex(12) # => "94b2fff3e7fd9b9c391a2306" p SecureRandom.hex(13) # => "39b290146bea6ce975c37cfc23" ... # random base64 string. p SecureRandom.base64(10) # => "EcmTPZwWRAozdA==" p SecureRandom.base64(10) # => "9b0nsevdwNuM/w==" p SecureRandom.base64(10) # => "KO1nIU+p9DKxGg==" p SecureRandom.base64(11) # => "l7XEiFja+8EKEtY=" p SecureRandom.base64(12) # => "7kJSM/MzBJI+75j8" p SecureRandom.base64(13) # => "vKLJ0tXBHqQOuIcSIg==" ... # random binary string. p SecureRandom.random_bytes(10) # => "\016\t{\370g\310pbr\301" p SecureRandom.random_bytes(10) # => "\323U\030TO\234\357\020\a\337" ...
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.
If secure random number generator is not available, NotImplementedError is raised.
[ show source ]
# File activesupport/lib/active_support/secure_random.rb, line 151 def self.base64(n=nil) [random_bytes(n)].pack("m*").delete("\n") end
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.
If secure random number generator is not available, NotImplementedError is raised.
[ show source ]
# File activesupport/lib/active_support/secure_random.rb, line 137 def self.hex(n=nil) random_bytes(n).unpack("H*")[0] end
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.
If secure random number generator is not available, NotImplementedError is raised.
[ show source ]
# File activesupport/lib/active_support/secure_random.rb, line 59 def self.random_bytes(n=nil) n ||= 16 unless defined? OpenSSL begin require 'openssl' rescue LoadError end end 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 flags |= File::NOFOLLOW if defined? File::NOFOLLOW 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 = " " * 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
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.
If 0 is given or an argument is not given, SecureRandom.random_number returns an float: 0.0 <= SecureRandom.random_number() < 1.0.
[ show source ]
# File activesupport/lib/active_support/secure_random.rb, line 164 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] mask |= mask >> 1 mask |= mask >> 2 mask |= mask >> 4 begin rnd = SecureRandom.random_bytes(bin.length) rnd[0] = rnd[0] & mask 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