| 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 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 vendor/rails/activesupport/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 vendor/rails/activesupport/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 vendor/rails/activesupport/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