Adds the §5 pre-build gate for multi-tenant replay protection.
buzz-auth gains a Nip98ReplayGuard trait plus the
nip98_replay_key(ctx, event_id) helper. The trait's try_mark contract
requires atomic set-if-absent semantics; an in-process cache (moka,
DashMap) does not carry the freshness proof across pods under the
"any pod, any connection" architecture (§4B), so the production
implementation MUST be shared state. The Redis-backed impl lives in
buzz-pubsub as RedisNip98ReplayGuard and uses a single SET key 1 NX
EX <ttl> per claim.
Key shape: buzz:{community}:nip98:{event_id_hex}. Event ids are
content-addressed so natural cross-community collision is zero, but
the gate is fail-closed isolation — a same-id replay across
communities must consult two distinct seen-set rows, not one shared
row. Tests pin both the prefix and the cross-community isolation
guarantee.
TTL floor is DEFAULT_REPLAY_TTL_SECS = 120, matching the §5 gate
requirement and the doubled NIP-98 ±60s timestamp tolerance.
Implementations MAY clamp sub-floor TTLs up to the floor; they MUST
NOT honor smaller values. The Redis impl clamps.
Caller contract documented in the trait: verify first, then mark.
Burning a seen-set slot on a forgery would let an attacker who learns
a future event id DoS the legitimate event. On Err (Redis
unreachable) callers MUST fail closed.
Not wired into a call site in this commit — there is no NIP-98 HTTP
handler in Lane 0 yet. Eva's relay-wiring lane will consume the trait
when the HTTP path lands; the contract is documented for that
integration.
Validation:
- cargo test -p buzz-auth --lib ✅ 40 passed (4 new in nip98_replay).
- cargo test -p buzz-pubsub --lib ✅ 3 passed, 9 Redis-required
ignored (3 new in nip98_replay).
- cargo test -p buzz-pubsub --lib nip98_replay -- --ignored against
local Redis ✅ 3 passed: first-claim/replay, cross-community
isolation, sub-floor TTL lifted to floor.
- Workspace check not run locally (sqlx 0.9.0 / rustc 1.94 vs local
1.89); CI catches it.
Co-authored-by: Tyler Longwell <tlongwell@block.xyz>
Signed-off-by: Tyler Longwell <tlongwell@block.xyz>
