1 files changed, 53 insertions, 24 deletions

diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb
index 4f7cd12d48..ada2e79ccb 100644
--- a/activesupport/lib/active_support/message_encryptor.rb
+++ b/activesupport/lib/active_support/message_encryptor.rb
@@ -1,5 +1,5 @@
 require 'openssl'
-require 'active_support/base64'
+require 'base64'
 
 module ActiveSupport
   # MessageEncryptor is a simple way to encrypt values which get stored somewhere
@@ -9,16 +9,56 @@ module ActiveSupport
   #
   # This can be used in situations similar to the <tt>MessageVerifier</tt>, but where you don't
   # want users to be able to determine the value of the payload.
+  #
+  #   key = OpenSSL::Digest::SHA256.new('password').digest        # => "\x89\xE0\x156\xAC..." 
+  #   crypt = ActiveSupport::MessageEncryptor.new(key)            # => #<ActiveSupport::MessageEncryptor ...> 
+  #   encrypted_data = crypt.encrypt_and_sign('my secret data')   # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..." 
+  #   crypt.decrypt_and_verify(encrypted_data)                    # => "my secret data" 
   class MessageEncryptor
+    module NullSerializer #:nodoc:
+      def self.load(value)
+        value
+      end
+
+      def self.dump(value)
+        value
+      end
+    end
+
     class InvalidMessage < StandardError; end
     OpenSSLCipherError = OpenSSL::Cipher.const_defined?(:CipherError) ? OpenSSL::Cipher::CipherError : OpenSSL::CipherError
 
-    def initialize(secret, cipher = 'aes-256-cbc')
+    # Initialize a new MessageEncryptor.
+    # +secret+ must be at least as long as the cipher key size. For the default 'aes-256-cbc' cipher,
+    # this is 256 bits. If you are using a user-entered secret, you can generate a suitable key with
+    # <tt>OpenSSL::Digest::SHA256.new(user_secret).digest</tt> or similar.
+    #
+    # Options:
+    # * <tt>:cipher</tt>      - Cipher to use. Can be any cipher returned by <tt>OpenSSL::Cipher.ciphers</tt>. Default is 'aes-256-cbc'
+    # * <tt>:serializer</tt>  - Object serializer to use. Default is +Marshal+.
+    # 
+    def initialize(secret, options = {})
       @secret = secret
-      @cipher = cipher
+      @cipher = options[:cipher] || 'aes-256-cbc'
+      @verifier = MessageVerifier.new(@secret, :serializer => NullSerializer)
+      @serializer = options[:serializer] || Marshal
+    end
+
+    # Encrypt and sign a message. We need to sign the message in order to avoid padding attacks.
+    # Reference: http://www.limited-entropy.com/padding-oracle-attacks
+    def encrypt_and_sign(value)
+      verifier.generate(_encrypt(value))
+    end
+
+    # Decrypt and verify a message. We need to verify the message in order to avoid padding attacks.
+    # Reference: http://www.limited-entropy.com/padding-oracle-attacks
+    def decrypt_and_verify(value)
+      _decrypt(verifier.verify(value))
     end
 
-    def encrypt(value)
+    private
+
+    def _encrypt(value)
       cipher = new_cipher
       # Rely on OpenSSL for the initialization vector
       iv = cipher.random_iv
@@ -27,15 +67,15 @@ module ActiveSupport
       cipher.key = @secret
       cipher.iv  = iv
 
-      encrypted_data = cipher.update(Marshal.dump(value))
+      encrypted_data = cipher.update(@serializer.dump(value))
       encrypted_data << cipher.final
 
-      [encrypted_data, iv].map {|v| ActiveSupport::Base64.encode64s(v)}.join("--")
+      [encrypted_data, iv].map {|v| ::Base64.strict_encode64(v)}.join("--")
     end
 
-    def decrypt(encrypted_message)
+    def _decrypt(encrypted_message)
       cipher = new_cipher
-      encrypted_data, iv = encrypted_message.split("--").map {|v| ActiveSupport::Base64.decode64(v)}
+      encrypted_data, iv = encrypted_message.split("--").map {|v| ::Base64.decode64(v)}
 
       cipher.decrypt
       cipher.key = @secret
@@ -44,28 +84,17 @@ module ActiveSupport
       decrypted_data = cipher.update(encrypted_data)
       decrypted_data << cipher.final
 
-      Marshal.load(decrypted_data)
+      @serializer.load(decrypted_data)
     rescue OpenSSLCipherError, TypeError
       raise InvalidMessage
     end
 
-    def encrypt_and_sign(value)
-      verifier.generate(encrypt(value))
+    def new_cipher
+      OpenSSL::Cipher::Cipher.new(@cipher)
     end
 
-    def decrypt_and_verify(value)
-      decrypt(verifier.verify(value))
+    def verifier
+      @verifier
     end
-
-
-
-    private
-      def new_cipher
-        OpenSSL::Cipher::Cipher.new(@cipher)
-      end
-
-      def verifier
-        MessageVerifier.new(@secret)
-      end
   end
 end