aes_gcm.rb in jwe-0.3.1

- old
+ new

@@ -1,7 +1,10 @@
+require 'jwe/enc/cipher'
+
 module JWE
   module Enc
+    # Abstract AES in Galois Counter mode for different key sizes.
     module AesGcm
       attr_accessor :cek
       attr_accessor :iv
       attr_accessor :tag
 
@@ -9,58 +12,56 @@
         self.iv = iv
         self.cek = cek
       end
 
       def encrypt(cleartext, authenticated_data)
-        raise JWE::BadCEK.new("The supplied key is too short. Required length: #{key_length}") if cek.length < key_length
+        raise JWE::BadCEK, "The supplied key is too short. Required length: #{key_length}" if cek.length < key_length
 
-        cipher.encrypt
-        cipher.key = cek
-        cipher.iv = iv
-        cipher.auth_data = authenticated_data
-
+        setup_cipher(:encrypt, authenticated_data)
         ciphertext = cipher.update(cleartext) + cipher.final
         self.tag = cipher.auth_tag
 
         ciphertext
       end
 
       def decrypt(ciphertext, authenticated_data)
-        raise JWE::BadCEK.new("The supplied key is too short. Required length: #{key_length}") if cek.length < key_length
+        raise JWE::BadCEK, "The supplied key is too short. Required length: #{key_length}" if cek.length < key_length
 
-        cipher.decrypt
-        cipher.key = cek
-        cipher.iv = iv
-        cipher.auth_tag = tag
-        cipher.auth_data = authenticated_data
-
+        setup_cipher(:decrypt, authenticated_data)
         cipher.update(ciphertext) + cipher.final
       rescue OpenSSL::Cipher::CipherError
-        raise JWE::InvalidData.new('Invalid ciphertext or authentication tag')
+        raise JWE::InvalidData, 'Invalid ciphertext or authentication tag'
       end
 
+      def setup_cipher(direction, auth_data)
+        cipher.send(direction)
+        cipher.key = cek
+        cipher.iv = iv
+        cipher.auth_tag = tag if direction == :decrypt
+        cipher.auth_data = auth_data
+      end
+
       def iv
         @iv ||= SecureRandom.random_bytes(12)
       end
 
       def cek
         @cek ||= SecureRandom.random_bytes(key_length)
       end
 
       def cipher
-        @cipher ||= OpenSSL::Cipher.new(cipher_name)
-      rescue RuntimeError
-        raise JWE::NotImplementedError.new("The version of OpenSSL linked to your Ruby does not support the cipher #{cipher_name}.")
+        @cipher ||= Cipher.for(cipher_name)
       end
 
       def tag
         @tag || ''
       end
 
       def self.included(base)
         base.extend(ClassMethods)
       end
 
+      # Provides availability checks for Key Encryption algorithms
       module ClassMethods
         def available?
           new.cipher
           true
         rescue JWE::NotImplementedError