File encryption/decryption implemented

lib/aes/aes.rb

@@ -4,10 +4,22 @@ class << self
     def encrypt(plain_text, key, opts={})
       ::AES::AES.new(key, opts).encrypt(plain_text)
     end
+
+    # Encrypts an file
+    def encrypt_file(filepath, enc_filepath, key, opts={})
+      ::AES::AES.new(key, opts).encrypt_file(filepath, enc_filepath)
+    end
+
     # Decrypts the cipher_text with the provided key
     def decrypt(cipher_text, key, opts={})
       ::AES::AES.new(key, opts).decrypt(cipher_text)
     end
+
+    # Decrypts an file
+    def decrypt_file(filepath, enc_filepath, key, opts={})
+      ::AES::AES.new(key, opts).decrypt_file(filepath, enc_filepath)
+    end
+
     # Generates a random key of the specified length in bits
     # Default format is :plain
     def key(length=256,format=:plain)
@@ -19,7 +31,7 @@ def key(length=256,format=:plain)
         key
       end
     end
-    # Generates a random iv 
+    # Generates a random iv
     # Default format is :plain
     def iv(format=:plain)
       iv = ::AES::AES.new("").random_iv
@@ -28,26 +40,29 @@ def iv(format=:plain)
         Base64.encode64(iv).chomp
       else
         iv
-      end      
+      end
     end
   end
-  
+
   class AES
     attr :options
     attr :key
     attr :iv
     attr :cipher
     attr :cipher_text
     attr :plain_text
-
+
+    ENCRYPT_CHUNK_SIZE = 2048
+    DECRYPT_CHUNK_SIZE = 2822 #it uses base64 on the encrypted chunk. this is the size after the base64 encoding.
+
     def initialize(key, opts={})
       merge_options opts
       @cipher = nil
       @key    = key
       @iv   ||= random_iv
       self
     end
-  
+
     # Encrypts
     def encrypt(plain_text)
       @plain_text = plain_text
@@ -62,7 +77,18 @@ def encrypt(plain_text)
       @cipher_text
     end
 
-    # Decrypts  
+    def encrypt_file(filepath, encrypted_filepath)
+      enc_file = File.open(encrypted_filepath, 'wb')
+      File.open(filepath, 'rb') do |f|
+        until f.eof
+          chunk = f.read(ENCRYPT_CHUNK_SIZE)
+          enc_file.write(encrypt(chunk))
+        end
+      end
+      enc_file.close
+    end
+
+    # Decrypts
     def decrypt(cipher_text)
       @cipher_text = cipher_text
       _setup(:decrypt)
@@ -73,32 +99,43 @@ def decrypt(cipher_text)
         ctext = @cipher_text
       end
       @cipher.iv  = ctext[0]
-      @plain_text = @cipher.update(ctext[1]) + @cipher.final 
+      @plain_text = @cipher.update(ctext[1]) + @cipher.final
+    end
+
+    def decrypt_file(encrypted_filepath, filepath)
+      file = File.open(filepath, 'wb')
+      File.open(encrypted_filepath, 'rb') do |f|
+        until f.eof
+          chunk = f.read(DECRYPT_CHUNK_SIZE)
+          file.write(decrypt(chunk))
+        end
+      end
+      file.close
     end
 
     # Generate a random initialization vector
     def random_iv
       _setup(:encrypt)
       @cipher.random_iv
     end
-  
+
     # Generate a random key
     def random_key(length=256)
       _random_seed.unpack('H*')[0][0..((length/8)-1)]
     end
-  
+
     private
-    
+
       # Generates a random seed value
       def _random_seed(size=32)
         if defined? OpenSSL::Random
           return OpenSSL::Random.random_bytes(size)
         else
           chars = ("a".."z").to_a + ("A".."Z").to_a + ("0".."9").to_a
-          (1..size).collect{|a| chars[rand(chars.size)] }.join        
+          (1..size).collect{|a| chars[rand(chars.size)] }.join
         end
       end
-    
+
       # Un-Base64's the IV and CipherText
       # Returns an array containing the IV, and CipherText
       def b64_d(data)
@@ -108,12 +145,12 @@ def b64_d(data)
         end
         iv_and_ctext
       end
-  
+
       # Base64 Encodes a string
       def b64_e(data)
         Base64.encode64(data).chomp
       end
-  
+
       # Encrypts @plain_text
       def _encrypt
         @cipher.update(@plain_text) + @cipher.final
@@ -128,7 +165,7 @@ def merge_options(opts)
         }.merge! opts
         _handle_iv
       end
-      
+
       def _handle_iv
         @iv = @options[:iv]
         return if @iv.nil?
@@ -138,13 +175,13 @@ def _handle_iv
           @iv  = Base64.decode64(@options[:iv])
         end
       end
-      
+
       # Create a new cipher using the cipher type specified
       def _setup(action)
-        @cipher ||= OpenSSL::Cipher::Cipher.new(@options[:cipher]) 
+        @cipher ||= OpenSSL::Cipher::Cipher.new(@options[:cipher])
         # Toggles encryption mode
         @cipher.send(action)
         @cipher.key = @key.unpack('a2'*32).map{|x| x.hex}.pack('c'*32)
       end
   end
-end
+end

test/test_aes.rb

@@ -1,7 +1,7 @@
 require 'helper'
 
 class TestAES < Test::Unit::TestCase
-    
+
   should "encrypt and decrypt a string" do
     key = "01234567890123456789012345678901"
     msg = "This is a message that nobody should ever see"
@@ -10,7 +10,7 @@ class TestAES < Test::Unit::TestCase
     enc = AES.encrypt(msg, key, {:format => :plain})
     assert_equal msg, AES.decrypt(enc, key, {:format => :plain})
   end
-  
+
   should "produce the same encrypted string when provided an identical key and iv" do
     key  = "01234567890123456789012345678901"
     msg  = "This is a message that nobody should ever see"
@@ -19,10 +19,32 @@ class TestAES < Test::Unit::TestCase
     enc2 = AES.encrypt(msg, key, {:iv => iv})
     assert_equal enc1, enc2
   end
-  
+
   should "generate a new key when AES#key" do
     assert_equal 32, AES.key.length
     assert_equal 44, AES.key(256, :base_64).length
   end
-
+
+  should "encrypt and decrypt a file" do
+    key = "01234567890123456789012345678901"
+    msg = "This is a message that nobody should ever see"
+    File.open('message.txt', 'w') { |f| f.write(msg) }
+
+    AES.encrypt_file('message.txt', 'encrypted.txt', key)
+    assert_not_equal(File.read('message.txt'), File.read('encrypted.txt'))
+
+    AES.decrypt_file('encrypted.txt', 'decrypted.txt', key)
+    assert_equal(File.read('message.txt'), File.read('decrypted.txt'))
+
+  end
+
+  def teardown
+    files = ['message.txt', 'encrypted.txt', 'decrypted.txt']
+    files.each do |file|
+      if File.exists?(file)
+        File.delete(file)
+      end
+    end
+  end
+
 end