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.

The result may contain A-Z, a-z, 0-9, "+", "/" and "=".

p SecureRandom.base64 #=> "/2BuBuLf3+WfSKyQbRcc/A=="
p SecureRandom.base64 #=> "6BbW0pxO0YENxn38HMUbcQ=="

If secure random number generator is not available, NotImplementedError is raised.

See RFC 3548 for the definition of base64.

 
 # File securerandom.rb, line 160
def self.base64(n=nil)
 [random_bytes(n)].pack("m*").delete("\n")
end
 

::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.

The result may contain 0-9 and a-f.

p SecureRandom.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
p SecureRandom.hex #=> "91dc3bfb4de5b11d029d376634589b61"

If secure random number generator is not available, NotImplementedError is raised.

 
 # File securerandom.rb, line 139
def self.hex(n=nil)
 random_bytes(n).unpack("H*")[0]
end
 

::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.

The result may contain any byte: "x00" - "xff".

p SecureRandom.random_bytes #=> "\xD8\\\xE0\xF4\r\xB2\xFC*WM\xFF\x83\x18\xF45\xB6"
p SecureRandom.random_bytes #=> "m\xDC\xFC/\a\x00Uf\xB2\xB2P\xBD\xFF6S\x97"

If secure random number generator is not available, NotImplementedError is raised.

 
 # File securerandom.rb, line 56
def self.random_bytes(n=nil)
 n = n ? n.to_int : 16
 if defined? OpenSSL::Random
 @pid = 0 if !defined?(@pid)
 pid = $$
 if @pid != pid
 now = Time.now
 ary = [now.to_i, now.nsec, @pid, pid]
 OpenSSL::Random.seed(ary.to_s)
 @pid = pid
 end
 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
 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: only #{ret.length} for #{n} bytes"
 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 = " ".force_encoding("ASCII-8BIT") * 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
 

::random_number generates a random number.

If a positive integer is given as n, ::random_number returns an integer: 0 <= ::random_number < n.

p SecureRandom.random_number(100) #=> 15
p SecureRandom.random_number(100) #=> 88

If 0 is given or an argument is not given, ::random_number returns a float: 0.0 <= ::random_number < 1.0.

p SecureRandom.random_number #=> 0.596506046187744
p SecureRandom.random_number #=> 0.350621695741409

 
 # File securerandom.rb, line 214
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].ord
 mask |= mask >> 1
 mask |= mask >> 2
 mask |= mask >> 4
 begin
 rnd = SecureRandom.random_bytes(bin.length)
 rnd[0] = (rnd[0].ord & mask).chr
 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
 

::urlsafe_base64 generates a random URL-safe 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.

The boolean argument padding specifies the padding. If it is false or nil, padding is not generated. Otherwise padding is generated. By default, padding is not generated because "=" may be used as a URL delimiter.

The result may contain A-Z, a-z, 0-9, "-" and "_". "=" is also used if padding is true.

p SecureRandom.urlsafe_base64 #=> "b4GOKm4pOYU_-BOXcrUGDg"
p SecureRandom.urlsafe_base64 #=> "UZLdOkzop70Ddx-IJR0ABg"
p SecureRandom.urlsafe_base64(nil, true) #=> "i0XQ-7gglIsHGV2_BNPrdQ=="
p SecureRandom.urlsafe_base64(nil, true) #=> "-M8rLhr7JEpJlqFGUMmOxg=="

If secure random number generator is not available, NotImplementedError is raised.

See RFC 3548 for the definition of URL-safe base64.

 
 # File securerandom.rb, line 190
def self.urlsafe_base64(n=nil, padding=false)
 s = [random_bytes(n)].pack("m*")
 s.delete!("\n")
 s.tr!("+/", "-_")
 s.delete!("=") if !padding
 s
end
 

::uuid generates a v4 random UUID (Universally Unique IDentifier).

p SecureRandom.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
p SecureRandom.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
p SecureRandom.uuid #=> "62936e70-1815-439b-bf89-8492855a7e6b"

The version 4 UUID is purely random (except the version). It doesn't contain meaningful information such as MAC address, time, etc.

See RFC 4122 for details of UUID.

 
 # File securerandom.rb, line 246
def self.uuid
 ary = self.random_bytes(16).unpack("NnnnnN")
 ary[2] = (ary[2] & 0x0fff) | 0x4000
 ary[3] = (ary[3] & 0x3fff) | 0x8000
 "%08x-%04x-%04x-%04x-%04x%08x" % ary
end