Harden native protocol: version discipline, rekey, migration, rate limit, O(1) client index

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Track A protocol hardening for native-v1.

1. Protocol VERSION discipline (protocol.rs, native.rs, dosh-server.rs,
   dosh-client.rs): bump protocol::VERSION to 2 and NATIVE_PROTOCOL_VERSION to 2.
   Foreign wire-version datagrams now get a clear named "protocol version
   mismatch - upgrade dosh" reject from the server instead of a silent timeout
   (peek_foreign_wire_version + VERSION_MISMATCH_REASON). The native handshake's
   plaintext protocol_version is also checked server-side before any crypto via
   check_native_protocol_version, returning a typed ProtocolVersionMismatch.

2. Transport rekey (spec section 11/9): server rotates a client's traffic key
   after rekey_after_packets OR rekey_after_secs (config knobs). Rotated keys are
   derived independently of the handshake keys from the current key plus fresh
   server CSPRNG material shipped confidentially in an AEAD Rekey packet
   (derive_rekey_session_key). The previous epoch's key is retained briefly so
   in-flight pre-rekey packets still decrypt (matched by session_key_id), and
   stale-epoch packets are ignored, not fatal. Client handles Rekey/RekeyAck.

3. Connection migration (spec section 11): every authenticated, replay-accepted
   packet now migrates client.endpoint to the new source address (input, resize,
   ping, ack, resume, stream*, rekey-ack), not just resume. Ping now verifies its
   AEAD tag before acting so migration cannot be spoofed.

4. Native auth rate limiting: per-source-IP token bucket
   (native_auth_rate_limit_per_minute) enforced in handle_native_client_hello
   BEFORE any X25519/Ed25519 work; over-limit hellos get a non-crypto reject.

5. Speed: replaced O(sessions x clients) per-packet linear scans with an O(1)
   HashMap<conn_id, session_name> index in ServerState, kept in sync on every
   client insert/remove (attach handlers, detach, remove_client, cleanup reap,
   session-exit drain).

New config keys (ServerConfig, with defaults): rekey_after_packets = 100000,
rekey_after_secs = 3600.

Tests: version-mismatch reject (no hang), rate-limit flood reject, rekey
round-trip end-to-end + key-derivation unit tests, source-address migration,
client-index sync + cleanup purge. fmt and full test suite green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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DuProcess

2026-06-14 10:45:44 -04:00

parent 2a6f28d529

commit f9c1973c13

7 changed files with 1283 additions and 169 deletions

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