3 ms·

Firefox reduced the timer precision, this demo does not work. https://developer.mozilla.org/en-US/docs/Web/API/Performance/now#reduced_time_precision https://de

• ddworken 6y ago
  It is worth noting that this POC was specifically targeted at Chromium based browsers. To quote the blog post, they also developed "a PoC which leaks data at 60B/s using timers with a precision of 1ms or worse". So Firefox's protection's are likely not sufficient to mitigate all Spectre attacks.
• NAR8789 6y ago
  I'm not able to get it to work in firefox either, but it feels like "reduced timer precision" shouldn't be sufficient to stop this particular attack. The authors of the demo here claim to be able to "amplify timing differences" by repeatedly hitting or missing cache and measuring the combined total time. My searching indicates firefox's performance.now precision is 20us, but the demo claims to be able to get timing differences of 2ms pretty easily. EDIT: 20us precision might be outdated... running this repeatedly on osx and linux, I'm distinctly getting my results "bucketed" into whatever the unit on the x-axis is. Based on that, I'm guessing timer precision on firefox is actually 1ms. Increasing the cache timer repetitions gets me to a smooth graph, but still no separation of the peaks. The fact that I can get the graph to go from discrete buckets to smooth normal curves makes me think this can indeed overcome reduced timer precision The fact that I can't get the peaks to separate makes me wonder if some other mitigation is protecting me.