Add a version hash for asset loading to prevent browser's cache issue

The hash is generated using the same salt as the one used for credentials (1 salt per instance)  in order to avoid exposing the instance version.

Fixes #965

2 files changed, 20 insertions, 0 deletions

diff --git a/application/ApplicationUtils.php b/application/ApplicationUtils.php
index 85dcbeeb..20fec376 100644
--- a/application/ApplicationUtils.php
+++ b/application/ApplicationUtils.php
@@ -220,4 +220,19 @@ class ApplicationUtils
 
         return $errors;
     }
+
+    /**
+     * Returns a salted hash representing the current Shaarli version.
+     *
+     * Useful for assets browser cache.
+     *
+     * @param string $currentVersion of Shaarli
+     * @param string $salt           User personal salt, also used for the authentication
+     *
+     * @return string version hash
+     */
+    public static function getVersionHash($currentVersion, $salt)
+    {
+        return hash_hmac('sha256', $currentVersion, $salt);
+    }
 }
diff --git a/application/PageBuilder.php b/application/PageBuilder.php
index 7a42400d..c91b662c 100644
--- a/application/PageBuilder.php
+++ b/application/PageBuilder.php
@@ -76,6 +76,10 @@ class PageBuilder
         $this->tpl->assign('searchcrits', $searchcrits);
         $this->tpl->assign('source', index_url($_SERVER));
         $this->tpl->assign('version', shaarli_version);
+        $this->tpl->assign(
+            'version_hash',
+            ApplicationUtils::getVersionHash(SHAARLI_VERSION, $this->conf->get('credentials.salt'))
+        );
         $this->tpl->assign('scripturl', index_url($_SERVER));
         $this->tpl->assign('privateonly', !empty($_SESSION['privateonly'])); // Show only private links?
         $this->tpl->assign('untaggedonly', !empty($_SESSION['untaggedonly']));
@@ -89,6 +93,7 @@ class PageBuilder
         $this->tpl->assign('feed_type', $this->conf->get('feed.show_atom', true) !== false ? 'atom' : 'rss');
         $this->tpl->assign('hide_timestamps', $this->conf->get('privacy.hide_timestamps', false));
         $this->tpl->assign('token', getToken($this->conf));
+
         if ($this->linkDB !== null) {
             $this->tpl->assign('tags', $this->linkDB->linksCountPerTag());
         }