Verify Nostr inbound signatures once, off the main actor

Every inbound relay event was Schnorr-verified TWICE, both times on the
main actor: once in NostrRelayManager.handleParsedMessage and again in
each NostrInboundPipeline / GeoPresenceTracker handler. Each
verification re-serializes the event JSON, hashes it, and runs a
secp256k1 Schnorr verify, so busy geohashes paid double crypto on the
UI thread. Geohash gift-wrap NIP-17 decryption (two ECDH+ChaCha layers)
also ran on the main actor.

Changes:
- NostrRelayManager now owns a serial off-main inbound pipeline
  (AsyncStream + single consumer task): frames are parsed and verified
  in arrival order off the main actor, preserving per-subscription
  delivery order. This is the single verification point for the whole
  inbound path; downstream handlers only ever see verified events.
- Dedup stays two-phase and unpoisonable: a cheap main-actor duplicate
  LOOKUP runs before verification (duplicate fan-in from several relays
  never pays for crypto — previously every duplicate was verified), and
  events are RECORDED as seen only after the signature verifies, so a
  forged-signature copy can never suppress the genuine event.
- NostrInboundPipeline and GeoPresenceTracker drop their redundant
  re-verification; geohash gift-wrap decryption moves off the main
  actor following the existing account-mailbox Task.detached pattern
  (atomic main-actor check-and-record, then decrypt off-main, then hop
  back for state updates).
- Tests: relay-level coverage for tampered gift wraps and for in-order
  delivery of back-to-back frames; pipeline-level tampered-signature
  tests move to the relay boundary where the invariant now lives; the
  mock relay connection queues frames emitted before receive re-arms.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bitchatTests/ChatNostrCoordinatorContextTests.swift

@@ -382,10 +382,12 @@ struct ChatNostrCoordinatorContextTests {
 
         coordinator.inbound.handleGiftWrap(giftWrap, id: recipient)
 
+        // The NIP-17 unwrap runs off the main actor; wait for the hop back.
         let convKey = PeerID(nostr_: sender.publicKeyHex)
+        let routed = await TestHelpers.waitUntil({ context.handledPrivateMessages.count == 1 })
+        #expect(routed)
         #expect(context.recordedNostrEventIDs == [giftWrap.id])
         #expect(context.nostrKeyMapping[convKey] == sender.publicKeyHex)
-        #expect(context.handledPrivateMessages.count == 1)
         #expect(context.handledPrivateMessages.first?.senderPubkey == sender.publicKeyHex)
         #expect(context.handledPrivateMessages.first?.convKey == convKey)
 
@@ -398,30 +400,37 @@ struct ChatNostrCoordinatorContextTests {
 
         // The same gift wrap is dropped on replay.
         coordinator.inbound.handleGiftWrap(giftWrap, id: recipient)
+        await drainMainQueue()
         #expect(context.recordedNostrEventIDs == [giftWrap.id])
         #expect(context.handledPrivateMessages.count == 1)
     }
 
+    // NOTE: Inbound Schnorr signature verification (and the forged-copy
+    // dedup-poisoning invariant) is enforced once, off the main actor, at the
+    // relay boundary — see NostrRelayManagerTests
+    // `test_receiveEvent_invalidSignatureDoesNotPoisonDuplicateCache` and
+    // `test_receiveGiftWrap_tamperedSignatureIsDroppedAndDoesNotPoisonDedup`.
+    // The inbound pipeline only ever sees verified events.
+
     @Test @MainActor
-    func processNostrMessage_invalidSignatureDoesNotPoisonDedup() async throws {
+    func processNostrMessage_duplicateDeliveryProcessesOnce() async throws {
         let context = MockChatNostrContext()
         let coordinator = ChatNostrCoordinator(context: context)
 
         let recipient = try NostrIdentity.generate()
         let sender = try NostrIdentity.generate()
+        context.nostrIdentity = recipient
         let giftWrap = try NostrProtocol.createPrivateMessage(
             content: "verify:noop",
             recipientPubkey: recipient.publicKeyHex,
             senderIdentity: sender
         )
-        var invalidGiftWrap = giftWrap
-        invalidGiftWrap.sig = String(repeating: "0", count: 128)
 
-        // A forged-signature copy is rejected WITHOUT entering the dedup set...
-        await coordinator.inbound.processNostrMessage(invalidGiftWrap)
-        #expect(context.recordedNostrEventIDs.isEmpty)
+        // Fan-in of the same (already verified) gift wrap from several relays
+        // records and processes exactly once.
+        await coordinator.inbound.processNostrMessage(giftWrap)
+        #expect(context.recordedNostrEventIDs == [giftWrap.id])
 
-        // ...so the genuine event with the same ID still processes and records.
         await coordinator.inbound.processNostrMessage(giftWrap)
         #expect(context.recordedNostrEventIDs == [giftWrap.id])
     }

bitchatTests/ChatViewModelExtensionsTests.swift

@@ -352,31 +352,11 @@ struct ChatViewModelNostrExtensionTests {
         #expect(!viewModel.messages.contains { $0.content == "Blocked" })
     }
 
-    @Test @MainActor
-    func handleNostrEvent_rejectsInvalidSignature() async throws {
-        let (viewModel, _) = makeTestableViewModel()
-        let geohash = "u4pruydq"
-        let identity = try NostrIdentity.generate()
-
-        viewModel.switchLocationChannel(to: .location(GeohashChannel(level: .city, geohash: geohash)))
-
-        let event = NostrEvent(
-            pubkey: identity.publicKeyHex,
-            createdAt: Date(),
-            kind: .ephemeralEvent,
-            tags: [["g", geohash]],
-            content: "Valid"
-        )
-        var signed = try event.sign(with: identity.schnorrSigningKey())
-        signed.id = "deadbeef"
-
-        viewModel.handleNostrEvent(signed)
-
-        try? await Task.sleep(nanoseconds: 100_000_000)
-        viewModel.publicMessagePipeline.flushIfNeeded()
-
-        #expect(!viewModel.messages.contains { $0.content == "Tampered" })
-    }
+    // NOTE: Tampered-signature rejection is enforced once, off the main
+    // actor, at the relay boundary (events only reach the inbound pipeline
+    // after verification) — see NostrRelayManagerTests
+    // `test_receiveEvent_invalidSignatureDoesNotPoisonDuplicateCache` and
+    // `test_receiveGiftWrap_tamperedSignatureIsDroppedAndDoesNotPoisonDedup`.
 
     @Test @MainActor
     func subscribeGiftWrap_rejectsOversizedEmbeddedPacket() async throws {
@@ -565,9 +545,14 @@ struct ChatViewModelNostrExtensionTests {
 
         viewModel.handleGiftWrap(giftWrap, id: recipient)
 
-        try? await Task.sleep(nanoseconds: 50_000_000)
+        // Gift-wrap decryption runs off the main actor; wait for the ack
+        // (sent even for blocked senders) to know processing finished.
+        let didAck = await TestHelpers.waitUntil(
+            { viewModel.sentGeoDeliveryAcks.contains(messageID) },
+            timeout: 5.0
+        )
+        #expect(didAck)
         #expect(viewModel.privateChats[convKey] == nil)
-        #expect(viewModel.sentGeoDeliveryAcks.contains(messageID))
     }
 
     @Test @MainActor

bitchatTests/GeohashPresenceTests.swift

@@ -326,26 +326,11 @@ struct ChatViewModelPresenceHandlingTests {
         #expect(viewModel.geohashParticipantCount(for: activeGeohash) >= 1)
     }
 
-    @Test func subscribeNostrEvent_samplingInvalidSignatureDoesNotPoisonDedup() async throws {
-        let (viewModel, _) = makeTestableViewModel()
-        let sampleGeohash = "u4pru"
-        let identity = try NostrIdentity.generate()
-        let event = NostrEvent(
-            pubkey: identity.publicKeyHex,
-            createdAt: Date(),
-            kind: .geohashPresence,
-            tags: [["g", sampleGeohash]],
-            content: ""
-        )
-        let signed = try event.sign(with: identity.schnorrSigningKey())
-        var invalid = signed
-        invalid.sig = String(repeating: "0", count: 128)
-
-        viewModel.subscribeNostrEvent(invalid, gh: sampleGeohash)
-        viewModel.subscribeNostrEvent(signed, gh: sampleGeohash)
-
-        #expect(viewModel.geohashParticipantCount(for: sampleGeohash) == 1)
-    }
+    // NOTE: Tampered-signature rejection (and the forged-copy dedup-poisoning
+    // invariant) is enforced once, off the main actor, at the relay boundary —
+    // the sampling path only ever sees verified events. See
+    // NostrRelayManagerTests
+    // `test_receiveEvent_invalidSignatureDoesNotPoisonDuplicateCache`.
 
     // MARK: - Test Helper
 

bitchatTests/Performance/PerformanceBaselineTests.swift

@@ -77,8 +77,10 @@ final class PerformanceBaselineTests: XCTestCase {
     // MARK: - 1a. Nostr inbound event handling (fresh events)
 
     /// `NostrInboundPipeline.handleNostrEvent` for never-seen geo events
-    /// (kind 20000): signature verification, dedup record, presence/nickname
-    /// bookkeeping, and public-message ingest scheduling.
+    /// (kind 20000): dedup record, presence/nickname bookkeeping, and
+    /// public-message ingest scheduling. Schnorr signature verification is
+    /// NOT part of this path anymore — it runs exactly once, off the main
+    /// actor, in `NostrRelayManager` before delivery.
     func testNostrInboundEventHandling_freshEvents() throws {
         let events = try Self.makeSignedGeohashEvents(count: 500)
         // A fresh context per measure pass so every event takes the
@@ -106,8 +108,9 @@ final class PerformanceBaselineTests: XCTestCase {
 
     /// The dedup-hit path: identical events replayed. Duplicates dominate
     /// real relay traffic (the same event arrives from several relays), so
-    /// this path runs hundreds of times a minute in busy geohashes. Note it
-    /// still pays full Schnorr signature verification before the dedup check.
+    /// this path runs hundreds of times a minute in busy geohashes. It is a
+    /// pure dedup lookup: no crypto (verification happens upstream in
+    /// `NostrRelayManager`, and only for the first-seen copy).
     func testNostrInboundEventHandling_duplicateEvents() throws {
         let events = try Self.makeSignedGeohashEvents(count: 500)
         let context = PerfNostrContext()

bitchatTests/Services/NostrRelayManagerTests.swift

@@ -724,6 +724,77 @@ final class NostrRelayManagerTests: XCTestCase {
         XCTAssertEqual(context.manager.debugDuplicateInboundEventDropCount(forSubscriptionID: "events"), 0)
     }
 
+    /// The relay boundary is the single signature-verification point for the
+    /// whole inbound path (downstream pipelines no longer re-verify), so a
+    /// tampered gift wrap (kind 1059, the DM/mailbox path) must be dropped
+    /// here — and must not poison the dedup cache against the genuine copy.
+    func test_receiveGiftWrap_tamperedSignatureIsDroppedAndDoesNotPoisonDedup() async throws {
+        let firstRelayURL = "wss://giftwrap-one.example"
+        let secondRelayURL = "wss://giftwrap-two.example"
+        let context = makeContext(permission: .denied)
+        let sender = try NostrIdentity.generate()
+        let recipient = try NostrIdentity.generate()
+        let giftWrap = try NostrProtocol.createPrivateMessage(
+            content: "psst",
+            recipientPubkey: recipient.publicKeyHex,
+            senderIdentity: sender
+        )
+        let tampered = invalidSignatureCopy(of: giftWrap)
+        var receivedIDs: [String] = []
+
+        context.manager.subscribe(
+            filter: makeFilter(),
+            id: "gift-wraps",
+            relayUrls: [firstRelayURL, secondRelayURL]
+        ) { event in
+            receivedIDs.append(event.id)
+        }
+        let subscriptionsSent = await waitUntil {
+            context.sessionFactory.latestConnection(for: firstRelayURL)?.sentStrings.count == 1 &&
+            context.sessionFactory.latestConnection(for: secondRelayURL)?.sentStrings.count == 1
+        }
+        XCTAssertTrue(subscriptionsSent)
+
+        try context.sessionFactory.latestConnection(for: firstRelayURL)?.emitEventMessage(subscriptionID: "gift-wraps", event: tampered)
+        try context.sessionFactory.latestConnection(for: secondRelayURL)?.emitEventMessage(subscriptionID: "gift-wraps", event: giftWrap)
+
+        let countedOnBothRelays = await waitUntil {
+            context.manager.relays.first(where: { $0.url == firstRelayURL })?.messagesReceived == 1 &&
+            context.manager.relays.first(where: { $0.url == secondRelayURL })?.messagesReceived == 1
+        }
+        XCTAssertTrue(countedOnBothRelays)
+        XCTAssertEqual(receivedIDs, [giftWrap.id])
+        XCTAssertEqual(context.manager.debugDuplicateInboundEventDropCount, 0)
+    }
+
+    /// Signature verification moved off-main into a single serial consumer;
+    /// several frames buffered on one socket must still be delivered to the
+    /// handler in arrival order.
+    func test_receiveEvent_deliversBackToBackEventsInArrivalOrder() async throws {
+        let relayURL = "wss://ordered.example"
+        let context = makeContext(permission: .denied)
+        let events = try (0..<12).map { try makeSignedEvent(content: "ordered-\($0)") }
+        var receivedIDs: [String] = []
+
+        context.manager.subscribe(filter: makeFilter(), id: "ordered", relayUrls: [relayURL]) { event in
+            receivedIDs.append(event.id)
+        }
+        let subscriptionSent = await waitUntil {
+            context.sessionFactory.latestConnection(for: relayURL)?.sentStrings.count == 1
+        }
+        XCTAssertTrue(subscriptionSent)
+
+        for event in events {
+            try context.sessionFactory.latestConnection(for: relayURL)?.emitEventMessage(subscriptionID: "ordered", event: event)
+        }
+
+        let allDelivered = await waitUntil(timeout: 5.0) {
+            receivedIDs.count == events.count
+        }
+        XCTAssertTrue(allDelivered)
+        XCTAssertEqual(receivedIDs, events.map(\.id))
+    }
+
     func test_receiveEvent_withoutHandlerStillTracksReceivedCount() async throws {
         let relayURL = "wss://missing-handler.example"
         let context = makeContext(permission: .denied)
@@ -1695,7 +1766,11 @@ private final class MockRelayConnection: NostrRelayConnectionProtocol {
     }
 
     func receive(completionHandler: @escaping (Result<URLSessionWebSocketTask.Message, Error>) -> Void) {
-        receiveHandler = completionHandler
+        if !pendingResults.isEmpty {
+            completionHandler(pendingResults.removeFirst())
+        } else {
+            receiveHandler = completionHandler
+        }
     }
 
     func sendPing(pongReceiveHandler: @escaping (Error?) -> Void) {
@@ -1728,15 +1803,24 @@ private final class MockRelayConnection: NostrRelayConnectionProtocol {
     }
 
     func emitRawString(_ string: String) throws {
-        let handler = receiveHandler
-        receiveHandler = nil
-        handler?(.success(.string(string)))
+        deliver(.success(.string(string)))
     }
 
     private func emit(jsonObject: Any) throws {
         let data = try JSONSerialization.data(withJSONObject: jsonObject)
-        let handler = receiveHandler
-        receiveHandler = nil
-        handler?(.success(.data(data)))
+        deliver(.success(.data(data)))
+    }
+
+    // Frames emitted before the manager re-arms `receive` are queued so
+    // back-to-back emissions model a socket with several buffered frames.
+    private var pendingResults: [Result<URLSessionWebSocketTask.Message, Error>] = []
+
+    private func deliver(_ result: Result<URLSessionWebSocketTask.Message, Error>) {
+        if let handler = receiveHandler {
+            receiveHandler = nil
+            handler(result)
+        } else {
+            pendingResults.append(result)
+        }
     }
 }