gemini-certificate-validation-demo-1/README.md

gemini-certificate-validation-demo-1

This is a minimal Gemini client capable of (self-signed) certificate validation using the additional network perspective of a Tor exit node. When the client encounters a new certificate for a host, it makes a TLS connection to the same host via Tor, in order to obtain its certificate from a second vantage point. The user is notified on certificate mismatch or connection failure.

This method should detect any local man-in-the-middle attack (originating from the same LAN, for instance) and should also provide protection over a more or less broad area of the Internet, depending on the exit node's position in the network graph and its DNS resolution setup. Any attack will trigger an alert unless it affects both the user and the exit node (whether it's a BGP hijack, a DNS compromise or whatever else).

This validation method works best when the exit node is far from the user's position. Users may configure Tor to select specific exit nodes by setting the ExitNodes and StrictNodes options in their torrc file. The ExitNodes option accepts countries, IP address ranges and node fingerprints. For example, this is how to only select exits located in France:

ExitNodes {fr}
StrictNodes 1

False alarms can be triggered by MITM attacks on the exit node's end. And, obviously, validation does not work for servers which block Tor.

Validated certificates are kept in memory for the duration of the browsing session. Tor is assumed to be listening on localhost, port 9050.

This is a fork of Solderpunk's minimal Gemini client written in Python.