[tor-dev] Summary of meek's costs, October 2015

[David Fifield]

On Fri, Nov 20, 2015 at 05:50:51PM -0600, Tom Ritter wrote:
> On 18 November 2015 at 16:32, David Fifield <david at bamsoftware.com> wrote:
> > There was an unfortunate outage of meek-amazon (not the result of
> > censorship, just operations failure). Between 30 September and 9 October
> > the bridge had an expired HTTPS certificate.
> >         [tor-talk] Outage of meek-amazon
> >         https://lists.torproject.org/pipermail/tor-talk/2015-October/039231.html
> >         https://lists.torproject.org/pipermail/tor-talk/2015-October/039234.html
> > And then, as a side effect of installing a new certificate, the bridge's
> > fingerprint changed, which caused Tor Browser to refuse to connect. It
> > used to be that we didn't include fingerprints for the meek bridges, but
> > now we do, so we didn't anticipate this error and didn't notice it
> > quickly.
> >         Update the meek-amazon fingerprint to B9E7141C594AF25699E0079C1F0146F409495296
> >         https://trac.torproject.org/projects/tor/ticket/17473
> >         [tor-talk] Changed fingerprint for meek-amazon bridge (attn support)
> >         https://lists.torproject.org/pipermail/tor-talk/2015-November/039397.html
> > Interestingly, the meek-amazon bridge still had about 400 simultaneous
> > users (not as much as normal) during the time when the fingerprint
> > didn't match. I would have expected it to go almost to zero. Maybe it's
> > people using an old version of Tor Browser (from before March 2015) or
> > some non–Tor Browser installation.
> 
> It seems like it would be better to use the SPKI rather than the cert
> fingerprint, this would allow you to reissue the same key and keep
> things working for older clients.

The fingerprint I'm talking about is the relay fingerprint, not the
HTTPS/X.509 one. The HTTPS certificate and the relay identity
fingerprint are completely independent. It just happened that in this
case, the relay was so configured, that when it rebooted to start using
the new HTTPS cert, it also generated a new identity key.

We're not pinning the HTTPS cert and in fact we can't; it's just used
for confidentiality on the CDN↔meek-server link.