Connection to some obfs4 bridges fails on fresh installation

Summary

Some obfs4 bridges don't work on fresh installations of TorBrowsers

Steps to reproduce:

If I have a fresh installation of Tor Browser and I try to set an obfs4 bridge

What is the current bug behavior?

I might (non-deterministically, but with high probability) have problems

  • the connection progress bar gets stuck at ~75%
  • waiting does not help
  • pressing cancel and retrying solves the problem.

I couldn't reproduce it on a TorBrowser which already connected to Tor in the past.

This is the same problem we found at Tails. In our issue there are more details about it.

Not every obfs4 bridge have this problem, but many do. I can share specific addresses if that's useful, but I think you'll have no problem finding bridges that have this behavior.

What is the expected behavior?

It should just connect

Environment

Edited by boyska