[tor-dev] UX improvement proposal: Onion auto-redirects using Alt-Svc HTTP header

[George Kadianakis]

teor <teor2345 at gmail.com> writes:

>> 
>> On 16 Nov 2017, at 00:38, Alec Muffett <alec.muffett at gmail.com> wrote:
>> 
>>> I think it's important to point out that a Tor client is never
>>> guaranteed to hold a *definitive* consensus.
>>> 
>> That's why I say "(mostly) definitive" in my text - my feeling is that a locally-held copy of the consensus to be queried is going to be on average of far higher quality, completeness, and non-stagnancy than something that one tries to scrape out of Onionoo every 15 minutes.
>
> Please don't use a consensus or a tor client to check for exits for
> this purpose. It produces significant numbers of false negatives,
> because some exits use other IP addresses for their exit traffic.
>

I'm actually not a fan of Alec's idea, and I agree with you that there
will be a significant number of false negatives, but it might be worth
pointing out that IIUC false negatives are probably not so damaging in
this use case, because it would result in users getting thrown to the
normal website instead of the onion site, because the website didn't
realize they are Tor users. So not much damage done there.

False positives are a bit more damaging for reachability because it
means that the website would throw normal users to the onion website
which would fail, but that's not so likely (except if exit node
operators surf from their exit node, or if an exit node IP is shared to
other people).