use window.crypto.getRandomValues

addon/webextension/makeUuid.js

@@ -1,12 +1,47 @@
 window.makeUuid = (function () {
 
-  // From http://stackoverflow.com/questions/105034/create-guid-uuid-in-javascript
+  // From http://pastebin.com/JSgC7eej
   return function makeUuid() { // eslint-disable-line no-unused-vars
-    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
-      var r = Math.random()*16 | 0,
-        v = c === 'x' ? r : (r & 0x3 | 0x8);
-      return v.toString(16);
-    });
+    // get sixteen unsigned 8 bit random values
+    var u = window
+      .crypto
+      .getRandomValues(new Uint8Array(16));
+
+    // set the version bit to v4
+    u[6] = (u[6] & 0x0f) | 0x40
+
+    // set the variant bit to "don't care" (yes, the RFC
+    // calls it that)
+    u[8] = (u[8] & 0xbf) | 0x80
+
+    // hex encode them and add the dashes
+    var uid = "";
+    uid += u[0].toString(16);
+    uid += u[1].toString(16);
+    uid += u[2].toString(16);
+    uid += u[3].toString(16);
+    uid += "-";
+
+    uid += u[4].toString(16);
+    uid += u[5].toString(16);
+    uid += "-";
+
+    uid += u[6].toString(16);
+    uid += u[7].toString(16);
+    uid += "-";
+
+    uid += u[8].toString(16);
+    uid += u[9].toString(16);
+    uid += "-";
+
+    uid += u[10].toString(16);
+    uid += u[11].toString(16);
+    uid += u[12].toString(16);
+    uid += u[13].toString(16);
+    uid += u[14].toString(16);
+    uid += u[15].toString(16);
+
+    return uid;
   };
 })();
 null;

shared/shot.js

@@ -145,20 +145,48 @@ function deepEqual(a, b) {
   return true;
 }
 
+// From http://pastebin.com/JSgC7eej
 function makeUuid() {
-  // FIXME: not a proper uuid
-  let id = "";
-  while (id.length < 12) {
-    // 46656 == Math.pow(36, 3)
-    let num;
-    if (! id) {
-      num = Date.now() % 46656;
-    } else {
-      num = Math.floor(Math.random() * 46656);
-    }
-    id += num.toString(36);
-  }
-  return id;
+  // get sixteen unsigned 8 bit random values
+  var u = window
+    .crypto
+    .getRandomValues(new Uint8Array(16));
+
+  // set the version bit to v4
+  u[6] = (u[6] & 0x0f) | 0x40
+
+  // set the variant bit to "don't care" (yes, the RFC
+  // calls it that)
+  u[8] = (u[8] & 0xbf) | 0x80
+
+  // hex encode them and add the dashes
+  var uid = "";
+  uid += u[0].toString(16);
+  uid += u[1].toString(16);
+  uid += u[2].toString(16);
+  uid += u[3].toString(16);
+  uid += "-";
+
+  uid += u[4].toString(16);
+  uid += u[5].toString(16);
+  uid += "-";
+
+  uid += u[6].toString(16);
+  uid += u[7].toString(16);
+  uid += "-";
+
+  uid += u[8].toString(16);
+  uid += u[9].toString(16);
+  uid += "-";
+
+  uid += u[10].toString(16);
+  uid += u[11].toString(16);
+  uid += u[12].toString(16);
+  uid += u[13].toString(16);
+  uid += u[14].toString(16);
+  uid += u[15].toString(16);
+
+  return uid;
 }
 
 class AbstractShot {