1 files changed, 87 insertions, 0 deletions
diff --git a/src/js/surrogates.js b/src/js/surrogates.js
new file mode 100644
index 0000000..5389afd
--- /dev/null
+++ b/src/js/surrogates.js
@@ -0,0 +1,87 @@
+/*
+ *
+ * This file is part of Privacy Badger <https://www.eff.org/privacybadger>
+ * Copyright (C) 2016 Electronic Frontier Foundation
+ *
+ * Privacy Badger is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Privacy Badger is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Privacy Badger.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+require.scopes.surrogates = (function() {
+
+const db = require('surrogatedb');
+
+/**
+ * Blocking tracking scripts (trackers) can cause parts of webpages to break.
+ * Surrogate scripts are dummy pieces of JavaScript meant to supply just enough
+ * of the original tracker's functionality to allow pages to continue working.
+ *
+ * This method gets called within request-blocking listeners:
+ * It needs to be fast!
+ *
+ * @param {String} script_url The full URL of the script resource being requested.
+ *
+ * @param {String} script_hostname The hostname component of the script_url
+ * parameter. This is an optimization: the calling context should already have
+ * this information.
+ *
+ * @return {(String|Boolean)} The surrogate script as a data URI when there is a
+ * match, or boolean false when there is no match.
+ */
+function getSurrogateURI(script_url, script_hostname) {
+  // do we have an entry for the script hostname?
+  if (db.hostnames.hasOwnProperty(script_hostname)) {
+    const tokens = db.hostnames[script_hostname];
+
+    // it's a wildcard token
+    if (_.isString(tokens)) {
+      if (db.surrogates.hasOwnProperty(tokens)) {
+        // return the surrogate code
+        return 'data:application/javascript;base64,' + btoa(db.surrogates[tokens]);
+      }
+    }
+
+    // must be an array of suffix tokens
+    const qs_start = script_url.indexOf('?');
+
+    for (let i = 0; i < tokens.length; i++) {
+      // do any of the suffix tokens match the script URL?
+      const token = tokens[i];
+
+      let match = false;
+
+      if (qs_start == -1) {
+        if (script_url.endsWith(token)) {
+          match = true;
+        }
+      } else {
+        if (script_url.endsWith(token, qs_start)) {
+          match = true;
+        }
+      }
+
+      if (match) {
+        // there is a match, return the surrogate code
+        return 'data:application/javascript;base64,' + btoa(db.surrogates[token]);
+      }
+    }
+  }
+
+  return false;
+}
+
+const exports = {
+  getSurrogateURI: getSurrogateURI,
+};
+
+return exports;
+})();