check checksum of document version

CHANGELOG

@@ -6,6 +6,8 @@
 - fix potential clickjacking attack with manipulated email address of a user
 - loading more items on ViewFolder page obeys sort order
 - fix possible csrf attacks due to missing form token
+- show an error msg on the documents detail page if the checksum of version
+  mismatch
 
 --------------------------------------------------------------------------------
                      Changes in version 5.1.21

views/bootstrap/class.ViewDocument.php

@@ -588,6 +588,11 @@ class SeedDMS_View_ViewDocument extends SeedDMS_Bootstrap_Style {
 			exit;
 		}
 
+		$checksum = SeedDMS_Core_File::checksum($dms->contentDir, $latestContent->getPath());
+		if($checksum != $latestContent->getChecksum()) {
+			$this->errorMsg(getMLText('wrong_checksum'));
+		}
+
 		$txt = $this->callHook('preLatestVersionTab', $latestContent);
 		if(is_string($txt))
 			echo $txt;