TLS 1.3 record layer (RFC 8446) #59

Phase 6: TLS 1.3 Record Layer#

Implement the TLS 1.3 record layer protocol in the net crate for framing and encrypting/decrypting TLS records.

Requirements#

• Record types (RFC 8446 §5.1):
  • ContentType: ChangeCipherSpec (20), Alert (21), Handshake (22), ApplicationData (23)
  • Record header: content type (1 byte), legacy version (2 bytes), length (2 bytes)
• Plaintext records: read/write TLS records over TCP
  • TlsRecord { content_type, data }
  • read_record(stream) -> Result<TlsRecord>
  • write_record(stream, record) -> Result<()>
• Encrypted records (RFC 8446 §5.2):
  • AEAD encryption using AES-128-GCM, AES-256-GCM, or ChaCha20-Poly1305
  • Per-record nonce construction: XOR base IV with sequence number
  • Inner content type (appended to plaintext before encryption)
  • Padding support (optional)
• Record size limits: max 2^14 bytes plaintext, max 2^14+256 bytes ciphertext
• Alert protocol: parse and generate alert messages (close_notify, fatal errors)

Dependencies#

• TCP socket wrapper (from prior issue)
• we-crypto crate: AES-GCM, ChaCha20-Poly1305

Acceptance Criteria#

• Read and write plaintext TLS records
• Encrypt records with AES-128-GCM and ChaCha20-Poly1305
• Decrypt records with proper nonce sequencing
• Content type hiding (inner content type in encrypted records)
• Record size enforcement
• Alert message handling (at least close_notify)
• Tests for record framing, encryption round-trips, nonce generation (20+ tests)
• cargo clippy and cargo fmt clean