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.
# 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 lib/active_support/secure_random.rb, line 151 151: def self.base64(n=nil) 152: [random_bytes(n)].pack("m*").delete("\n") 153: 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 lib/active_support/secure_random.rb, line 137 137: def self.hex(n=nil) 138: random_bytes(n).unpack("H*")[0] 139: 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 lib/active_support/secure_random.rb, line 59 59: def self.random_bytes(n=nil) 60: n ||= 16 61: 62: unless defined? OpenSSL 63: begin 64: require 'openssl' 65: rescue LoadError 66: end 67: end 68: 69: if defined? OpenSSL::Random 70: return OpenSSL::Random.random_bytes(n) 71: end 72: 73: if !defined?(@has_urandom) || @has_urandom 74: flags = File::RDONLY 75: flags |= File::NONBLOCK if defined? File::NONBLOCK 76: flags |= File::NOCTTY if defined? File::NOCTTY 77: flags |= File::NOFOLLOW if defined? File::NOFOLLOW 78: begin 79: File.open("/dev/urandom", flags) {|f| 80: unless f.stat.chardev? 81: raise Errno::ENOENT 82: end 83: @has_urandom = true 84: ret = f.readpartial(n) 85: if ret.length != n 86: raise NotImplementedError, "Unexpected partial read from random device" 87: end 88: return ret 89: } 90: rescue Errno::ENOENT 91: @has_urandom = false 92: end 93: end 94: 95: if !defined?(@has_win32) 96: begin 97: require 'Win32API' 98: 99: crypt_acquire_context = Win32API.new("advapi32", "CryptAcquireContext", 'PPPII', 'L') 100: @crypt_gen_random = Win32API.new("advapi32", "CryptGenRandom", 'LIP', 'L') 101: 102: hProvStr = " " * 4 103: prov_rsa_full = 1 104: crypt_verifycontext = 0xF0000000 105: 106: if crypt_acquire_context.call(hProvStr, nil, nil, prov_rsa_full, crypt_verifycontext) == 0 107: raise SystemCallError, "CryptAcquireContext failed: #{lastWin32ErrorMessage}" 108: end 109: @hProv, = hProvStr.unpack('L') 110: 111: @has_win32 = true 112: rescue LoadError 113: @has_win32 = false 114: end 115: end 116: if @has_win32 117: bytes = " " * n 118: if @crypt_gen_random.call(@hProv, bytes.size, bytes) == 0 119: raise SystemCallError, "CryptGenRandom failed: #{lastWin32ErrorMessage}" 120: end 121: return bytes 122: end 123: 124: raise NotImplementedError, "No random device" 125: 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 lib/active_support/secure_random.rb, line 164 164: def self.random_number(n=0) 165: if 0 < n 166: hex = n.to_s(16) 167: hex = '0' + hex if (hex.length & 1) == 1 168: bin = [hex].pack("H*") 169: mask = bin[0] 170: mask |= mask >> 1 171: mask |= mask >> 2 172: mask |= mask >> 4 173: begin 174: rnd = SecureRandom.random_bytes(bin.length) 175: rnd[0] = rnd[0] & mask 176: end until rnd < bin 177: rnd.unpack("H*")[0].hex 178: else 179: # assumption: Float::MANT_DIG <= 64 180: i64 = SecureRandom.random_bytes(8).unpack("Q")[0] 181: Math.ldexp(i64 >> (64-Float::MANT_DIG), -Float::MANT_DIG) 182: end 183: end
Disabled; run with --debug to generate this.
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