From e8db4017b8640762880212197dc489b5ff4389bc Mon Sep 17 00:00:00 2001
From: Stefan Weiberg <sweiberg@suse.com>
Date: Thu, 11 Oct 2018 20:24:36 +0200
Subject: [PATCH] backport of #10778

Adding a check to see if keyFileContents is empty:

* this fixes a download error and an exception if the data content
  for encryption is empty
* #3958: for recovering encrypted files with a damaged signature
  this is necessary in addition to turning the signature check off

Signed-off-by: Stefan Weiberg <sweiberg@suse.com>
---
 apps/encryption/lib/Crypto/Crypt.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/apps/encryption/lib/Crypto/Crypt.php b/apps/encryption/lib/Crypto/Crypt.php
index 49b1bcb41aa..70c99f808ba 100644
--- a/apps/encryption/lib/Crypto/Crypt.php
+++ b/apps/encryption/lib/Crypto/Crypt.php
@@ -457,6 +457,10 @@ class Crypt {
 	 * @throws DecryptionFailedException
 	 */
 	public function symmetricDecryptFileContent($keyFileContents, $passPhrase, $cipher = self::DEFAULT_CIPHER, $version = 0, $position = 0) {
+		if ($keyFileContents == '') {
+			return '';
+		}
+
 		$catFile = $this->splitMetaData($keyFileContents, $cipher);
 
 		if ($catFile['signature'] !== false) {