Module | ActiveSupport::SecureRandom |
In: |
vendor/rails/activesupport/lib/active_support/secure_random.rb
|
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.
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.
# 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.
# File vendor/rails/activesupport/lib/active_support/secure_random.rb, line 149 149: def self.base64(n=nil) 150: [random_bytes(n)].pack("m*").delete("\n") 151: 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.
# File vendor/rails/activesupport/lib/active_support/secure_random.rb, line 135 135: def self.hex(n=nil) 136: random_bytes(n).unpack("H*")[0] 137: 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.
# File vendor/rails/activesupport/lib/active_support/secure_random.rb, line 64 64: def self.random_bytes(n=nil) 65: n ||= 16 66: 67: if defined? OpenSSL::Random 68: return OpenSSL::Random.random_bytes(n) 69: end 70: 71: if !defined?(@has_urandom) || @has_urandom 72: flags = File::RDONLY 73: flags |= File::NONBLOCK if defined? File::NONBLOCK 74: flags |= File::NOCTTY if defined? File::NOCTTY 75: flags |= File::NOFOLLOW if defined? File::NOFOLLOW 76: begin 77: File.open("/dev/urandom", flags) {|f| 78: unless f.stat.chardev? 79: raise Errno::ENOENT 80: end 81: @has_urandom = true 82: ret = f.readpartial(n) 83: if ret.length != n 84: raise NotImplementedError, "Unexpected partial read from random device" 85: end 86: return ret 87: } 88: rescue Errno::ENOENT 89: @has_urandom = false 90: end 91: end 92: 93: if !defined?(@has_win32) 94: begin 95: require 'Win32API' 96: 97: crypt_acquire_context = Win32API.new("advapi32", "CryptAcquireContext", 'PPPII', 'L') 98: @crypt_gen_random = Win32API.new("advapi32", "CryptGenRandom", 'LIP', 'L') 99: 100: hProvStr = " " * 4 101: prov_rsa_full = 1 102: crypt_verifycontext = 0xF0000000 103: 104: if crypt_acquire_context.call(hProvStr, nil, nil, prov_rsa_full, crypt_verifycontext) == 0 105: raise SystemCallError, "CryptAcquireContext failed: #{lastWin32ErrorMessage}" 106: end 107: @hProv, = hProvStr.unpack('L') 108: 109: @has_win32 = true 110: rescue LoadError 111: @has_win32 = false 112: end 113: end 114: if @has_win32 115: bytes = " " * n 116: if @crypt_gen_random.call(@hProv, bytes.size, bytes) == 0 117: raise SystemCallError, "CryptGenRandom failed: #{lastWin32ErrorMessage}" 118: end 119: return bytes 120: end 121: 122: raise NotImplementedError, "No random device" 123: 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.
# File vendor/rails/activesupport/lib/active_support/secure_random.rb, line 162 162: def self.random_number(n=0) 163: if 0 < n 164: hex = n.to_s(16) 165: hex = '0' + hex if (hex.length & 1) == 1 166: bin = [hex].pack("H*") 167: mask = bin[0] 168: mask |= mask >> 1 169: mask |= mask >> 2 170: mask |= mask >> 4 171: begin 172: rnd = SecureRandom.random_bytes(bin.length) 173: rnd[0] = rnd[0] & mask 174: end until rnd < bin 175: rnd.unpack("H*")[0].hex 176: else 177: # assumption: Float::MANT_DIG <= 64 178: i64 = SecureRandom.random_bytes(8).unpack("Q")[0] 179: Math.ldexp(i64 >> (64-Float::MANT_DIG), -Float::MANT_DIG) 180: end 181: end