fix logic for 304 workaround

FreshRSS · Sep 20, 2024 · 2a60217 · 2a60217
1 parent ecee8d4
commit 2a60217
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Showing 2 changed files with 24 additions and 6 deletions.
diff --git a/src/HTTP/Utils.php b/src/HTTP/Utils.php
@@ -11,6 +11,24 @@
  */
 final class Utils
 {
+
+    /**
+     * Extracts `max-age` from the `Cache-Control` HTTP headers
+     *
+     * @param array<string,mixed> $http_headers HTTP headers of the response
+     * @return int|null The `max-age` value or `null` if not found
+     *
+     * FreshRSS
+     */
+    public static function get_http_max_age(array $http_headers): ?int
+    {
+        $cache_control = $http_headers['cache-control'] ?? '';
+        if (is_string($cache_control) && $cache_control !== '' && preg_match('/\bmax-age=(\d+)\b/', $cache_control, $matches)) {
+            return (int) $matches[1];
+        }
+        return null;
+    }
+
     /**
      * Negotiate the cache expiration time based on the HTTP response headers.
      * Return the cache duration time in number of seconds since the Unix Epoch, accounting for:

diff --git a/src/SimplePie.php b/src/SimplePie.php
@@ -2019,20 +2019,20 @@ protected function fetch_data(&$cache)
                             $this->raw_data = false;
                             if (isset($file)) { // FreshRSS
                                 $old_cache_control = $this->data['headers']['cache-control'] ?? '';
+                                $old_max_age = \SimplePie\HTTP\Utils::get_http_max_age($this->data['headers']);
 
                                 // Update cache metadata
                                 $this->data['headers'] = array_map(function (array $values): string {
                                     return implode(',', $values);
                                 }, $file->get_headers());
 
                                 // Workaround for buggy servers returning wrong cache-control headers for 304 responses
-                                if (is_numeric($old_cache_control)) {
-                                    $new_cache_control = $this->data['headers']['cache-control'] ?? '';
-                                    if (!is_numeric($new_cache_control)) {
-                                        $new_cache_control = $this->cache_duration;
+                                if ($old_max_age !== null) {
+                                    $new_max_age = \SimplePie\HTTP\Utils::get_http_max_age($this->data['headers']);
+                                    if ($new_max_age === null || $new_max_age > $old_max_age) {
+                                        // Allow servers to return a shorter cache duration for 304 responses, but not longer
+                                        $this->data['headers']['cache-control'] = $old_cache_control;
                                     }
-                                    // Allow servers to return a shorter cache duration for 304 responses, but not longer
-                                    $this->data['headers']['cache-control'] = min((int)$old_cache_control, (int)$new_cache_control);
                                 }
 
                                 $this->data['cache_expiration_time'] = \SimplePie\HTTP\Utils::negociate_cache_expiration_time($this->data['headers'] ?? [], $this->cache_duration, $this->cache_duration_min, $this->cache_duration_max);