Autodiscovery of Hidden Services Given a Domain or a Website

Question

IPFS has DNSLink and Dat has .well-known/dat for the autodiscovery of the content on their networks given a domain name (or a website in Dat's case).

So for instance, when a user visits http://facebook.com/ using Tor Browser Bundle, the browser can automatically discover if the website offers a hidden service (e.g. http://facebookcorewwwi.onion/) and can redirect (or ask to redirect) the user.

P.S. I remember reading something about Tor's solution to this (which used DNS), but cannot find it again as search results for "tor" and "dns" return irrelevant results mostly about DNS leaks.

Answer 1

This is now possible in Tor Browser 9.5: https://www.torproject.org/releases/tor-browser-95/

You can set the Onion-Location HTTP header or add a <meta> tag to the HTML.

See https://community.torproject.org/onion-services/advanced/onion-location/ and https://kushaldas.in/posts/onion-location-and-onion-names-in-tor-browser-9-5.html for details.

To enable this, in Apache, you need a configuration line like below for your website’s configuration.

Header set Onion-Location "http://your-onion-address.onion%{REQUEST_URI}s"

Remember to enable rewrite module.

For nginx, add the following in your server configuration.

add_header Onion-Location http://<your-onion-address>.onion$request_uri;