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 activesupport/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