Receiver now rejects gossip envelopes whose prev_event_hash doesn't
extend the sender's last-seen event_hash — fork detection lives at the
wire layer, not just in docs/mesh.md.
Schema: new mesh_peer_chains table (peer_member_id PK, last_event_hash,
last_seq, last_seen_at) with idempotent _migrate_mesh_peer_chains
matching the _migrate_audit_mode pattern.
Envelope: WireEnvelope gains prev_event_hash + event_hash, both
optional for back-compat. canonical_bytes() excludes event_hash to
avoid the circular dependency (the hash is computed FROM the canonical
bytes). New WireEnvelope.with_chain(prev_event_hash=...) builds a
linked envelope with event_hash = sha256(prev || canonical_bytes).
Sender (MeshWireClient._signed_envelope, MeshWireServer.handle_request
DELIVER_BODY): reads our latest_event_hash, builds the linked
envelope, then appends a 'mesh_sent' audit event whose body is the
envelope's canonical (event-hash-excluded) dict. By construction the
audit event_hash equals the envelope event_hash — wire chain-of-claims
and local audit chain stay in lockstep, so back-to-back sends advance
the chain naturally.
Receiver (handle_announce): when an envelope carries chain fields,
recompute event_hash and 400 on mismatch; look up
mesh_peer_chains[sender] and 409 on prev mismatch; on accept update
the row + write the existing mesh_received event.
Backward compat: legacy envelopes (event_hash=None) bypass chain
enforcement — kept the existing test_mesh_wire.py fixtures verbatim
since they construct WireEnvelope directly without with_chain(). All
production traffic goes through MeshWireClient and is always tracked.
v1 deferred (documented in module docstring): no multi-event catchup;
operator retries on 409. No cross-peer reconciliation.
Tests: 12 new in tests/test_mesh_chain.py covering the 7 required
cases plus canonical-bytes exclusion, migration idempotence, and
legacy-envelope fallback. 246 passed, 1 skipped overall.
Adds an opt-in confidentiality layer to gossip. Senders pass
encrypt=True on announce_root / announce_falsification; bodies travel
AEAD-encrypted (ChaCha20-Poly1305) under the per-epoch symmetric secret
recovered via the existing X25519 wrap. Cleartext stays the default —
all existing wire tests pass without modification.
WireEnvelope grows an optional encrypted_body field. canonical_bytes
omits the field when None (byte-identical to v1 cleartext format) and
includes it when set, so the Ed25519 signature binds the ciphertext —
a MITM cannot swap payloads. AAD is type|sender|epoch|ts so a captured
(nonce, ct) cannot be replayed under different envelope metadata.
state.recover_epoch_secret resolves the rotator from the audit chain
and re-unwraps this peer's slot. Sender + receiver share one path; no
new sender-side cache is required.
Implements the protocol contract pinned in docs/mesh.md. Each peer
runs a stdlib ThreadingHTTPServer; clients send Ed25519-signed
envelopes carrying one of:
ANNOUNCE_ROOT document_root + source_uri + versions
ANNOUNCE_DERIVATION core_root <- surface_roots (proof-blob hash)
ANNOUNCE_PROVIDENCE cache_key + audit_mode + answer_hash
ANNOUNCE_FALSIFICATION cache_key + reason
REQUEST_BODY/DELIVER_BODY pull-on-miss + Merkle-root verify
WireEnvelope canonicalizes via sorted-key separator-tight JSON; the
canonical bytes are what get signed. Receivers verify the signature
against sender_id's sign_pub looked up in mesh_roster at the
envelope's epoch_id — non-members of that epoch produce no valid
signature, so they're silently rejected (401, no audit event).
Each accepted ANNOUNCE_* writes one 'mesh_received' event into the
local audit chain whose body is the full signed envelope (the
remote's signature stays attached for non-repudiation). The
receiver's chain stays internally consistent because we append in
receive-order.
REQUEST_BODY/DELIVER_BODY: the responder ships the document text
plus per-chunk leaf hashes; the client re-derives the Merkle root
from those leaves and refuses to return any body whose leaves
don't reconstruct the requested root.
Tests: 17 unit (envelope canonicalization, sig verify against
roster, type validation, tampered-body rejection, audit-event
write) + 5 end-to-end (two real HTTP peers on ephemeral ports
exchanging announces and bodies). 22/22 green.
Deferred to later commits, per docs/mesh.md:
- CLI verbs (mesh serve, mesh sync) — pending downstream merge
- per-peer chain-of-claims tracking (catchup, replay, fork detection)
- optional AEAD encryption of message bodies (contract says optional)
