optimized email sync from cloud to do RSA validation and decryption only once

src/js/crypto/aes-cbc.js

@@ -16,6 +16,11 @@
 		 * @return [String] The base64 encoded ciphertext
 		 */
 		this.encrypt = function(plaintext, key, iv) {
+			// validate args
+			if (!plaintext || !key || !iv) {
+				throw new Error("Missing args for encryption!");
+			}
+
 			// decode args to utf8 and encrypt
 			var cipher = forge.aes.createEncryptionCipher(utl.decode64(key));
 			cipher.start(utl.decode64(iv));
@@ -34,6 +39,11 @@
 		 * @return [String] The decrypted plaintext in UTF-16
 		 */
 		this.decrypt = function(ciphertext, key, iv) {
+			// validate args
+			if (!ciphertext || !key || !iv) {
+				throw new Error("Missing args for decryption!");
+			}
+
 			// decode args input to utf8 decrypt
 			var cipher = forge.aes.createDecryptionCipher(utl.decode64(key));
 			cipher.start(utl.decode64(iv));

src/js/crypto/crypto-batch-worker.js

@@ -28,6 +28,14 @@
 					// start decryption
 					output = batch.decryptListForUser(i.list, i.senderPubkeys, i.receiverPrivkey);
 
+				} else if (i.type === 'reencrypt' && i.senderPubkeys && i.receiverPrivkey && i.list && i.symKey) {
+					// start validation and re-encryption
+					output = batch.reencryptListKeysForUser(i.list, i.senderPubkeys, i.receiverPrivkey, i.symKey);
+
+				} else if (i.type === 'decryptItems' && i.symKey && i.list) {
+					// start decryption
+					output = batch.decryptKeysAndList(i.list, i.symKey);
+
 				} else {
 					throw 'Not all arguments for web worker crypto are defined!';
 				}

src/js/crypto/crypto-batch.js

@@ -97,7 +97,7 @@
 		 * Decrypt and verify a list of item keys using RSA
 		 * @param list [Array] The list of items to decrypt
 		 * @param senderPubkeys [Array] A list of public keys used to verify
-		 * @param receiverPrivkey [Array] The receiver's private key used to decrypt
+		 * @param receiverPrivkey [String] The receiver's private key used to decrypt
 		 */
 		this.decryptListKeysForUser = function(list, senderPubkeys, receiverPrivkey) {
 			var senderPk,
@@ -120,6 +120,27 @@
 			return list;
 		};
 
+		/**
+		 * Decrypt a list of item keys using RSA and the encrypt them again using AES
+		 * @param list [Array] The list of items to decrypt
+		 * @param senderPubkeys [Array] A list of public keys used to verify
+		 * @param receiverPrivkey [String] The receiver's private key used to decrypt
+		 * @param symKey [String] The symmetric key used to re-encrypt the item key
+		 */
+		this.reencryptListKeysForUser = function(list, senderPubkeys, receiverPrivkey, symKey) {
+			// verify and decrypt item keys using RSA
+			this.decryptListKeysForUser(list, senderPubkeys, receiverPrivkey);
+
+			list.forEach(function(i) {
+				// re-encrypt item key using aes
+				i.encryptedKey = aes.encrypt(i.key, symKey, i.iv);
+
+				delete i.key;
+			});
+
+			return list;
+		};
+
 		/**
 		 * Decrypt an item using AES
 		 * @param i [Object] The item to decrypt
@@ -149,6 +170,32 @@
 			return list;
 		};
 
+		/**
+		 * Decrypt keys and items using AES
+		 * @param list [Array] The list of items to decrypt
+		 * @param symKey [String] The symmetric key used to re-encrypt the item key
+		 */
+		this.decryptKeysAndList = function(list, symKey) {
+			var self = this,
+				j;
+
+			list.forEach(function(i) {
+				// decrypt item key
+				i.key = aes.decrypt(i.encryptedKey, symKey, i.iv);
+				// decrypt item for user
+				self.decryptItem(i);
+
+				delete i.encryptedKey;
+			});
+
+			// set plaintext as list item
+			for (j = 0; j < list.length; j++) {
+				list[j] = list[j].plaintext;
+			}
+
+			return list;
+		};
+
 		/**
 		 * Decrypt and verify an item using AES and RSA
 		 * @param i [Object] The item to decrypt

src/js/crypto/crypto.js

@@ -9,6 +9,8 @@ define(['cryptoLib/util', 'cryptoLib/aes-cbc', 'cryptoLib/rsa', 'cryptoLib/crypt
 
 	var self = {};
 
+	var passBasedKey;
+
 	/**
 	 * Initializes the crypto modules by fetching the user's
 	 * encrypted secret key from storage and storing it in memory.
@@ -34,6 +36,9 @@ define(['cryptoLib/util', 'cryptoLib/aes-cbc', 'cryptoLib/rsa', 'cryptoLib/crypt
 				return;
 			}
 
+			// remember pbkdf2 for later use
+			passBasedKey = derivedKey;
+
 			// check if key exists
 			if (!args.storedKeypair) {
 				// generate keys, encrypt and persist if none exists
@@ -239,6 +244,42 @@ define(['cryptoLib/util', 'cryptoLib/aes-cbc', 'cryptoLib/rsa', 'cryptoLib/crypt
 		});
 	};
 
+	//
+	// Re-encrypt keys item and items seperately
+	//
+
+	self.reencryptListKeysForUser = function(list, senderPubkeys, callback) {
+		var keypair = rsa.exportKeys();
+		var receiverPrivkey = {
+			_id: keypair._id,
+			privateKey: keypair.privkeyPem
+		};
+
+		startWorker('/crypto/crypto-batch-worker.js', {
+			type: 'reencrypt',
+			list: list,
+			receiverPrivkey: receiverPrivkey,
+			senderPubkeys: senderPubkeys,
+			symKey: passBasedKey
+		}, callback, function() {
+			return cryptoBatch.reencryptListKeysForUser(list, senderPubkeys, receiverPrivkey, passBasedKey);
+		});
+	};
+
+	self.decryptKeysAndList = function(list, callback) {
+		startWorker('/crypto/crypto-batch-worker.js', {
+			type: 'decryptItems',
+			list: list,
+			symKey: passBasedKey
+		}, callback, function() {
+			return cryptoBatch.decryptKeysAndList(list, passBasedKey);
+		});
+	};
+
+	//
+	// helper functions
+	//
+
 	function startWorker(script, args, callback, noWorker) {
 		// check for WebWorker support
 		if (window.Worker) {

src/js/dao/email-dao.js

@@ -80,7 +80,7 @@ define(['underscore', 'cryptoLib/util', 'js/crypto/crypto', 'js/dao/lawnchair-da
 		 * @param num [Number] The number of items to fetch (null means fetch all)
 		 */
 		self.listItems = function(folderName, offset, num, callback) {
-			var collection, folder, already, pubkeyIds = [];
+			var collection, folder;
 
 			// check if items are in memory already (account.folders model)
 			folder = self.account.get('folders').where({
@@ -99,6 +99,56 @@ define(['underscore', 'cryptoLib/util', 'js/crypto/crypto', 'js/dao/lawnchair-da
 						return;
 					}
 
+					// decrypt list
+					crypto.decryptKeysAndList(encryptedList, function(err, decryptedList) {
+						if (err) {
+							callback(err);
+							return;
+						}
+
+						// cache collection in folder memory
+						if (decryptedList.length > 0) {
+							folder = new app.model.Folder({
+								name: folderName
+							});
+							folder.set('items', decryptedList);
+							self.account.get('folders').add(folder);
+						}
+
+						callback(null, decryptedList);
+					});
+				});
+
+			} else {
+				// read items from memory
+				collection = folder.get('items');
+				callback(null, collection);
+			}
+		};
+
+		/**
+		 * Synchronize a folder's items from the cloud to the device-storage
+		 * @param folderName [String] The name of the folder e.g. 'inbox'
+		 */
+		self.syncFromCloud = function(folderName, callback) {
+			var folder, already, pubkeyIds = [];
+
+			cloudstorage.listEncryptedItems('email', self.account.get('emailAddress'), folderName, function(err, encryptedList) {
+				// return if an error occured
+				if (err) {
+					callback({
+						errMsg: 'Syncing encrypted items from cloud failed!',
+						err: err
+					}); // error
+					return;
+				}
+				if (encryptedList.length === 0) {
+					callback();
+					return;
+				}
+
+				// TODO: remove old folder items from devicestorage
+
 				// gather public key ids required to verify signatures
 				encryptedList.forEach(function(i) {
 					already = null;
@@ -119,56 +169,15 @@ define(['underscore', 'cryptoLib/util', 'js/crypto/crypto', 'js/dao/lawnchair-da
 						return;
 					}
 
-						// decrypt list
-						crypto.decryptListForUser(encryptedList, senderPubkeys, function(err, decryptedList) {
+					// verfiy signatures and re-encrypt item keys
+					crypto.reencryptListKeysForUser(encryptedList, senderPubkeys, function(err, encryptedKeyList) {
 						if (err) {
 							callback(err);
 							return;
 						}
 
-							// cache collection in folder memory
-							if (decryptedList.length > 0) {
-								folder = new app.model.Folder({
-									name: folderName
-								});
-								folder.set('items', decryptedList);
-								self.account.get('folders').add(folder);
-							}
-
-							callback(null, decryptedList);
-						});
-
-					});
-				});
-
-			} else {
-				// read items from memory
-				collection = folder.get('items');
-				callback(null, collection);
-			}
-		};
-
-		/**
-		 * Synchronize a folder's items from the cloud to the device-storage
-		 * @param folderName [String] The name of the folder e.g. 'inbox'
-		 */
-		self.syncFromCloud = function(folderName, callback) {
-			var folder;
-
-			cloudstorage.listEncryptedItems('email', self.account.get('emailAddress'), folderName, function(err, data) {
-				// return if an error occured
-				if (err) {
-					callback({
-						errMsg: 'Syncing encrypted items from cloud failed!',
-						err: err
-					}); // error
-					return;
-				}
-
-				// TODO: remove old folder items from devicestorage
-
 						// persist encrypted list in device storage
-				devicestorage.storeEcryptedList(data, 'email_' + folderName, function() {
+						devicestorage.storeEcryptedList(encryptedKeyList, 'email_' + folderName, function() {
 							// remove cached folder in account model
 							folder = self.account.get('folders').where({
 								name: folderName
@@ -179,6 +188,9 @@ define(['underscore', 'cryptoLib/util', 'js/crypto/crypto', 'js/dao/lawnchair-da
 							callback();
 						});
 					});
+
+				});
+			});
 		};
 
 		/**

test/unit/email-dao-test.js

@@ -17,7 +17,7 @@ define(['js/dao/email-dao', 'js/dao/keychain-dao', 'js/dao/lawnchair-dao',
 		// init dependencies
 		jsonDao.init(emaildaoTest.user);
 		// cloud storage stub
-		var cloudstorageStub = {
+		emaildaoTest.cloudstorageStub = {
 			putPublicKey: function(pk, callback) {
 				callback();
 			},
@@ -28,8 +28,8 @@ define(['js/dao/email-dao', 'js/dao/keychain-dao', 'js/dao/lawnchair-dao',
 				callback();
 			}
 		};
-		emaildaoTest.keychain = new KeychainDAO(cloudstorageStub);
-		emaildaoTest.emailDao = new EmailDAO(cloudstorageStub, emaildaoTest.keychain);
+		emaildaoTest.keychain = new KeychainDAO(emaildaoTest.cloudstorageStub);
+		emaildaoTest.emailDao = new EmailDAO(emaildaoTest.cloudstorageStub, emaildaoTest.keychain);
 
 		// generate test data
 		emaildaoTest.list = testData.getEmailCollection(100);
@@ -54,7 +54,7 @@ define(['js/dao/email-dao', 'js/dao/keychain-dao', 'js/dao/lawnchair-dao',
 		});
 	});
 
-	asyncTest("Persist test emails", 4, function() {
+	asyncTest("Persist test emails (stubbed sync from cloud)", 4, function() {
 		emaildaoTest.keychain.getUserKeyPair(emaildaoTest.user, function(err, keypair) {
 			ok(!err && keypair, 'Fetch keypair from keychain');
 
@@ -69,8 +69,13 @@ define(['js/dao/email-dao', 'js/dao/keychain-dao', 'js/dao/lawnchair-dao',
 					encryptedList[i].sentDate = emaildaoTest.list.at(i).get('sentDate');
 				}
 
-				storage.storeEcryptedList(encryptedList, 'email_inbox', function() {
-					ok(true, 'Store encrypted list');
+				// set encrypted test list as return value for cloud storage stub
+				emaildaoTest.cloudstorageStub.listEncryptedItems = function(type, emailAddress, folderName, callback) {
+					callback(null, encryptedList);
+				};
+
+				emaildaoTest.emailDao.syncFromCloud('inbox', function() {
+					ok(true, 'Stored encrypted list');
 
 					start();
 				});