Use number of chunk for HMAC as well

Prevents switching single blocks within the encrypted file.

3 files changed, 29 insertions, 19 deletions

diff --git a/apps/encryption/lib/crypto/crypt.php b/apps/encryption/lib/crypto/crypt.php
index 6c3aee47a56..b4c10f42790 100644
--- a/apps/encryption/lib/crypto/crypt.php
+++ b/apps/encryption/lib/crypto/crypt.php
@@ -170,10 +170,11 @@ class Crypt {
 	 * @param string $plainContent
 	 * @param string $passPhrase
 	 * @param int $version
+	 * @param int $position
 	 * @return false|string
 	 * @throws EncryptionFailedException
 	 */
-	public function symmetricEncryptFileContent($plainContent, $passPhrase, $version) {
+	public function symmetricEncryptFileContent($plainContent, $passPhrase, $version, $position) {
 
 		if (!$plainContent) {
 			$this->logger->error('Encryption Library, symmetrical encryption failed no content given',
@@ -189,7 +190,7 @@ class Crypt {
 			$this->getCipher());
 
 		// Create a signature based on the key as well as the current version
-		$sig = $this->createSignature($encryptedContent, $passPhrase.$version);
+		$sig = $this->createSignature($encryptedContent, $passPhrase.$version.$position);
 
 		// combine content to encrypt the IV identifier and actual IV
 		$catFile = $this->concatIV($encryptedContent, $iv);
@@ -368,6 +369,7 @@ class Crypt {
 		$encryptedKey = $this->symmetricEncryptFileContent(
 			$privateKey,
 			$hash,
+			0,
 			0
 		);
 
@@ -444,14 +446,15 @@ class Crypt {
 	 * @param string $passPhrase
 	 * @param string $cipher
 	 * @param int $version
+	 * @param int $position
 	 * @return string
 	 * @throws DecryptionFailedException
 	 */
-	public function symmetricDecryptFileContent($keyFileContents, $passPhrase, $cipher = self::DEFAULT_CIPHER, $version = 0) {
+	public function symmetricDecryptFileContent($keyFileContents, $passPhrase, $cipher = self::DEFAULT_CIPHER, $version = 0, $position = 0) {
 		$catFile = $this->splitMetaData($keyFileContents, $cipher);
 
 		if ($catFile['signature'] !== false) {
-			$this->checkSignature($catFile['encrypted'], $passPhrase.$version, $catFile['signature']);
+			$this->checkSignature($catFile['encrypted'], $passPhrase.$version.$position, $catFile['signature']);
 		}
 
 		return $this->decrypt($catFile['encrypted'],
diff --git a/apps/encryption/lib/crypto/encryption.php b/apps/encryption/lib/crypto/encryption.php
index 90c60b8e0d5..d4e8087c4b0 100644
--- a/apps/encryption/lib/crypto/encryption.php
+++ b/apps/encryption/lib/crypto/encryption.php
@@ -215,13 +215,14 @@ class Encryption implements IEncryptionModule {
 	 * buffer.
 	 *
 	 * @param string $path to the file
+	 * @param int $position
 	 * @return string remained data which should be written to the file in case
 	 *                of a write operation
 	 * @throws PublicKeyMissingException
 	 * @throws \Exception
 	 * @throws \OCA\Encryption\Exceptions\MultiKeyEncryptException
 	 */
-	public function end($path) {
+	public function end($path, $position = 0) {
 		$result = '';
 		if ($this->isWriteOperation) {
 			// Partial files do not increase the version
@@ -230,7 +231,7 @@ class Encryption implements IEncryptionModule {
 			}
 			$this->keyManager->setVersion($this->path, $this->version+1);
 			if (!empty($this->writeCache)) {
-				$result = $this->crypt->symmetricEncryptFileContent($this->writeCache, $this->fileKey, $this->version+1);
+				$result = $this->crypt->symmetricEncryptFileContent($this->writeCache, $this->fileKey, $this->version+1, $position);
 				$this->writeCache = '';
 			}
 			$publicKeys = array();
@@ -264,9 +265,10 @@ class Encryption implements IEncryptionModule {
 	 * encrypt data
 	 *
 	 * @param string $data you want to encrypt
+	 * @param int $position
 	 * @return string encrypted data
 	 */
-	public function encrypt($data) {
+	public function encrypt($data, $position = 0) {
 		// If extra data is left over from the last round, make sure it
 		// is integrated into the next block
 		if ($this->writeCache) {
@@ -314,7 +316,7 @@ class Encryption implements IEncryptionModule {
 				if(\OC\Files\Cache\Scanner::isPartialFile($this->path)) {
 					$this->version = $this->version - 1;
 				}
-				$encrypted .= $this->crypt->symmetricEncryptFileContent($chunk, $this->fileKey, $this->version+1);
+				$encrypted .= $this->crypt->symmetricEncryptFileContent($chunk, $this->fileKey, $this->version+1, $position);
 
 				// Remove the chunk we just processed from
 				// $data, leaving only unprocessed data in $data
@@ -332,10 +334,11 @@ class Encryption implements IEncryptionModule {
 	 * decrypt data
 	 *
 	 * @param string $data you want to decrypt
+	 * @param int $position
 	 * @return string decrypted data
 	 * @throws DecryptionFailedException
 	 */
-	public function decrypt($data) {
+	public function decrypt($data, $position = 0) {
 		if (empty($this->fileKey)) {
 			$msg = 'Can not decrypt this file, probably this is a shared file. Please ask the file owner to reshare the file with you.';
 			$hint = $this->l->t('Can not decrypt this file, probably this is a shared file. Please ask the file owner to reshare the file with you.');
@@ -344,11 +347,7 @@ class Encryption implements IEncryptionModule {
 			throw new DecryptionFailedException($msg, $hint);
 		}
 
-		$result = '';
-		if (!empty($data)) {
-			$result = $this->crypt->symmetricDecryptFileContent($data, $this->fileKey, $this->cipher, $this->version);
-		}
-		return $result;
+		return $this->crypt->symmetricDecryptFileContent($data, $this->fileKey, $this->cipher, $this->version, $position);
 	}
 
 	/**
diff --git a/lib/private/files/stream/encryption.php b/lib/private/files/stream/encryption.php
index bc771a91ebd..63949035b5a 100644
--- a/lib/private/files/stream/encryption.php
+++ b/lib/private/files/stream/encryption.php
@@ -399,8 +399,9 @@ class Encryption extends Wrapper {
 	}
 
 	public function stream_close() {
-		$this->flush();
-		$remainingData = $this->encryptionModule->end($this->fullPath);
+		$this->flush('end');
+		$position = (int)floor($this->position/$this->unencryptedBlockSize);
+		$remainingData = $this->encryptionModule->end($this->fullPath, $position . 'end');
 		if ($this->readOnly === false) {
 			if(!empty($remainingData)) {
 				parent::stream_write($remainingData);
@@ -412,15 +413,17 @@ class Encryption extends Wrapper {
 
 	/**
 	 * write block to file
+	 * @param string $positionPrefix
 	 */
-	protected function flush() {
+	protected function flush($positionPrefix = '') {
 		// write to disk only when writeFlag was set to 1
 		if ($this->writeFlag) {
 			// Disable the file proxies so that encryption is not
 			// automatically attempted when the file is written to disk -
 			// we are handling that separately here and we don't want to
 			// get into an infinite loop
-			$encrypted = $this->encryptionModule->encrypt($this->cache);
+			$position = (int)floor($this->position/$this->unencryptedBlockSize);
+			$encrypted = $this->encryptionModule->encrypt($this->cache, $position . $positionPrefix);
 			$bytesWritten = parent::stream_write($encrypted);
 			$this->writeFlag = false;
 			// Check whether the write concerns the last block
@@ -447,7 +450,12 @@ class Encryption extends Wrapper {
 		if ($this->cache === '' && !($this->position === $this->unencryptedSize && ($this->position % $this->unencryptedBlockSize) === 0)) {
 			// Get the data from the file handle
 			$data = parent::stream_read($this->util->getBlockSize());
-			$this->cache = $this->encryptionModule->decrypt($data);
+			$position = (int)floor($this->position/$this->unencryptedBlockSize);
+			$numberOfChunks = (int)($this->unencryptedSize / $this->unencryptedBlockSize);
+			if($numberOfChunks === $position) {
+				$position .= 'end';
+			}
+			$this->cache = $this->encryptionModule->decrypt($data, $position);
 		}
 	}