1 files changed, 102 insertions, 0 deletions
diff --git a/lib/securerandom.rb b/lib/securerandom.rb
new file mode 100644
index 0000000000..6079fdb5c4
--- /dev/null
+++ b/lib/securerandom.rb
@@ -0,0 +1,102 @@
+# -*- coding: us-ascii -*-
+# frozen_string_literal: true
+
+require 'random/formatter'
+
+# == Secure random number generator interface.
+#
+# This library is an interface to secure random number generators which are
+# suitable for generating session keys in HTTP cookies, etc.
+#
+# You can use this library in your application by requiring it:
+#
+#   require 'securerandom'
+#
+# It supports the following secure random number generators:
+#
+# * openssl
+# * /dev/urandom
+# * Win32
+#
+# SecureRandom is extended by the Random::Formatter module which
+# defines the following methods:
+#
+# * alphanumeric
+# * base64
+# * choose
+# * gen_random
+# * hex
+# * rand
+# * random_bytes
+# * random_number
+# * urlsafe_base64
+# * uuid
+#
+# These methods are usable as class methods of SecureRandom such as
+# +SecureRandom.hex+.
+#
+# If a secure random number generator is not available,
+# +NotImplementedError+ is raised.
+
+module SecureRandom
+
+  # The version
+  VERSION = "0.4.1"
+
+  class << self
+    # Returns a random binary string containing +size+ bytes.
+    #
+    # See Random.bytes
+    def bytes(n)
+      return gen_random(n)
+    end
+
+    # Compatibility methods for Ruby 3.2, we can remove this after dropping to support Ruby 3.2
+    def alphanumeric(n = nil, chars: ALPHANUMERIC)
+      n = 16 if n.nil?
+      choose(chars, n)
+    end if RUBY_VERSION < '3.3'
+
+    private
+
+    # :stopdoc:
+
+    # Implementation using OpenSSL
+    def gen_random_openssl(n)
+      return OpenSSL::Random.random_bytes(n)
+    end
+
+    # Implementation using system random device
+    def gen_random_urandom(n)
+      ret = Random.urandom(n)
+      unless ret
+        raise NotImplementedError, "No random device"
+      end
+      unless ret.length == n
+        raise NotImplementedError, "Unexpected partial read from random device: only #{ret.length} for #{n} bytes"
+      end
+      ret
+    end
+
+    begin
+      # Check if Random.urandom is available
+      Random.urandom(1)
+      alias gen_random gen_random_urandom
+    rescue RuntimeError
+      begin
+        require 'openssl'
+      rescue NoMethodError
+        raise NotImplementedError, "No random device"
+      else
+        alias gen_random gen_random_openssl
+      end
+    end
+
+    # :startdoc:
+
+    # Generate random data bytes for Random::Formatter
+    public :gen_random
+  end
+end
+
+SecureRandom.extend(Random::Formatter)