OP-01-011 Error suppression in UTF-8 decoding function (Medium). Add check for parameter type to decode_utf8.

src/util.js

@@ -142,6 +142,9 @@ module.exports = {
    * @return {String} A native javascript string
    */
   decode_utf8: function (utf8) {
+    if (typeof utf8 !== 'string') {
+      throw new Error('Parameter "utf8" is not of type string');
+    }
     try {
       return decodeURIComponent(escape(utf8));
     } catch (e) {

test/general/basic.js

@@ -328,4 +328,13 @@ describe('Basic', function() {
     });
   });
 
+  describe("Misc.", function() {
+
+    it('util.decode_utf8 throws error if invalid parameter type', function () {
+      var test = openpgp.util.decode_utf8.bind(null, {chameleon: true});
+      expect(test).to.throw(Error, /Parameter "utf8" is not of type string/);
+    });
+
+  });
+
 });