Use pool counter for generating large diffs to prevent DoS.

Bug: T130947
Change-Id: If560844664051c04e01b954377b4bdfdb744d13f

Signed-off-by: Chad Horohoe <chadh@wikimedia.org>

diff --git a/includes/diff/DifferenceEngine.php b/includes/diff/DifferenceEngine.php
index caef7f1..8985d51 100644 (file)
--- a/includes/diff/DifferenceEngine.php
+++ b/includes/diff/DifferenceEngine.php
@@ -842,19 +842,36 @@ class DifferenceEngine extends ContextSource {
         * @return bool|string
         */
        public function generateTextDiffBody( $otext, $ntext ) {
-               $time = microtime( true );
+               $diff = function() use ( $otext, $ntext ) {
+                       $time = microtime( true );
 
-               $result = $this->textDiff( $otext, $ntext );
+                       $result = $this->textDiff( $otext, $ntext );
 
-               $time = intval( ( microtime( true ) - $time ) * 1000 );
-               $this->getStats()->timing( 'diff_time', $time );
-               // Log requests slower than 99th percentile
-               if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
-                       wfDebugLog( 'diff',
-                               "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
+                       $time = intval( ( microtime( true ) - $time ) * 1000 );
+                       $this->getStats()->timing( 'diff_time', $time );
+                       // Log requests slower than 99th percentile
+                       if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
+                               wfDebugLog( 'diff',
+                                       "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
+                       }
+
+                       return $result;
+               };
+
+               $error = function( $status ) {
+                       throw new FatalError( $status->getWikiText() );
+               };
+
+               // Use PoolCounter if the diff looks like it can be expensive
+               if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
+                       $work = new PoolCounterWorkViaCallback( 'diff',
+                               md5( $otext ) . md5( $ntext ),
+                               [ 'doWork' => $diff, 'error' => $error ]
+                       );
+                       return $work->execute();
                }
 
-               return $result;
+               return $diff();
        }
 
        /**