💾 Archived View for egsam.mk16.de › 4.2.gmi captured on 2023-05-24 at 17:42:52. Gemini links have been rewritten to link to archived content
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This server cannot at this moment test TOFU certificate-pinning.
Clients can validate TLS connections however they like (including not at all) but the strongly RECOMMENDED approach is to implement a lightweight "TOFU" certificate-pinning system which treats self-signed certificates as first- class citizens. This greatly reduces TLS overhead on the network (only one cert needs to be sent, not a whole chain) and lowers the barrier to entry for setting up a Gemini site (no need to pay a CA or setup a Let's Encrypt cron job, just make a cert and go).
TOFU stands for "Trust On First Use" and is public-key security model similar to that used by OpenSSH. The first time a Gemini client connects to a server, it accepts whatever certificate it is presented. That certificate's fingerprint and expiry date are saved in a persistent database (like the .known_hosts file for SSH), associated with the server's hostname. On all subsequent connections to that hostname, the received certificate's fingerprint is computed and compared to the one in the database. If the certificate is not the one previously received, but the previous certificate's expiry date has not passed, the user is shown a warning, analogous to the one web browser users are shown when receiving a certificate without a signature chain leading to a trusted CA.
This model is by no means perfect, but it is not awful and is vastly superior to just accepting self-signed certificates unconditionally.