We can fix email server encryption!
Sydney is a Staff Technologist at the Electronic Frontier Foundation. She primarily works on EFF's initiative to secure all TCP packets, like finally securing email delivery via STARTTLS Everywhere. In the past she has also developed on the Let's Encrypt Certbot client, which secures communications with web users via HTTPS. Otherwise, she cares a lot about decentralizing state and corporate power, censorship resistance, puzzles, 2D illustration, and noodles.
For years the SMTP protocol that email servers use to deliver your mail over the Internet has had an encryption option, called STARTTLS. This server-to-server encryption feature has only recently become common, and the way it's typically used is still very fragile. An attacker can trick servers into turning off the encryption (downgrade) or using the wrong encryption key (man-in-the-middle). This talk will be centered on a demo of the problems and work we and others have been doing to fix them.
First, I'll break the encrypted connection between two demo mailservers, showing that we can intercept or modify emails even when server admins think they've turned on encrypted email delivery. Then, I'll talk about why this is possible and the different solutions the ecosystem is working towards to solve the problem, including DANE, MTA-STS, and how our STARTTLS Everywhere project fits in. Finally, I'm going to fortify the TLS support on some Postfix mailservers, with brand-new tooling released in the past year.