TLSv1.3 from scratch
summary
LibreSSL implements TLS 1.3 by writing a new stack from scratch: roughly 7,000 lines of C produced by three people over several six‑week sprints, with the client implemented first. A DAG‑based handshake state machine prevents out‑of‑order attacks, the key schedule uses HKDF (a subtle misread required hashing a zero length input), and the record layer enforces one‑record per call with careful memory zeroing. Interop testing uses tlsfuzzer and oss‑fuzz, and workarounds handle odd peers like Fizz sending duplicate CCS and legacy libssl API behaviors such as auto_retry and partial writes.
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chapters (15)
- 0:00Intro
- 6:15TLSv13 vs TLS12
- 9:53Can we have it yet
- 17:20TLS stack
- 18:44Handstake state machine
- 20:02Handshakesvg
- 22:31Key derivation
- 24:44Record layer
- 26:31Security
- 27:13Handshaking
- 27:34Legacy Stack
- 28:33SSL
- 32:29Interoperability
- 37:56Summary
- 39:32Questions
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