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 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.
# File 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.
# File 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.
# File 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
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