TemplateParser: Improve cache integrity check failure scenario

Previously, if the cache integrity check failed then it would emit a
warning but then continue to use the code. The integrity check could
genuinely fail if the secret key was changed, if the cache was
truncated, or other edge case scenarios.

Now TemplateParser will recompile if the cache fails the integrity
check, and then update the cache with the newly compiled version.

Bug: T163154
Change-Id: I9a6c8d528f84cfbabf402cfaf6468c162fab1f15

diff --git a/includes/TemplateParser.php b/includes/TemplateParser.php
index 924c347..2759ff9 100644 (file)
--- a/includes/TemplateParser.php
+++ b/includes/TemplateParser.php
@@ -102,20 +102,22 @@ class TemplateParser {
                        $key = $cache->makeKey( 'template', $templateName, $fastHash );
                        $code = $this->forceRecompile ? null : $cache->get( $key );
 
-                       if ( !$code ) {
-                               $code = $this->compileForEval( $fileContents, $filename );
-
-                               // Prefix the cached code with a keyed hash (64 hex chars) as an integrity check
-                               $cache->set( $key, hash_hmac( 'sha256', $code, $secretKey ) . $code );
-                       } else {
+                       if ( $code ) {
                                // Verify the integrity of the cached PHP code
                                $keyedHash = substr( $code, 0, 64 );
                                $code = substr( $code, 64 );
                                if ( $keyedHash !== hash_hmac( 'sha256', $code, $secretKey ) ) {
-                                       // Generate a notice if integrity check fails
-                                       trigger_error( "Template failed integrity check: {$filename}" );
+                                       // If the integrity check fails, don't use the cached code
+                                       // We'll update the invalid cache below
+                                       $code = null;
                                }
                        }
+                       if ( !$code ) {
+                               $code = $this->compileForEval( $fileContents, $filename );
+
+                               // Prefix the cached code with a keyed hash (64 hex chars) as an integrity check
+                               $cache->set( $key, hash_hmac( 'sha256', $code, $secretKey ) . $code );
+                       }
                // If there is no secret key available, don't use cache
                } else {
                        $code = $this->compileForEval( $fileContents, $filename );