Pin announce signing keys to stop mesh identity spoofing (#1349)

TOFU-pins the Ed25519 signing key per noise key so a self-consistent announce that reuses a victim's peerID+noise key with the attacker's signing key/nickname is rejected instead of overwriting the registry and persisted identity. Complements #1432: that PR's signed-LEAVE verification reads the stored signing key this PR protects from announce-path poisoning.

Rebased onto main as a single commit; swift build --build-tests green, 40/40 targeted tests incl. the spoofing e2e cases, and #1432's suites 50/50 unaffected.

bitchatTests/Services/BLEPeerRegistryTests.swift

@@ -6,12 +6,12 @@ import Testing
 @Suite("BLE peer registry tests")
 struct BLEPeerRegistryTests {
     @Test("upserted announces track new, reconnect, and rename transitions")
-    func upsertVerifiedAnnounceTracksTransitions() {
+    func upsertVerifiedAnnounceTracksTransitions() throws {
         var registry = BLEPeerRegistry()
         let peerID = PeerID(str: "1122334455667788")
         let firstSeen = Date(timeIntervalSince1970: 100)
 
-        let first = registry.upsertVerifiedAnnounce(
+        let firstResult = registry.upsertVerifiedAnnounce(
             peerID: peerID,
             nickname: "alice",
             noisePublicKey: Data([1, 2, 3]),
@@ -19,6 +19,7 @@ struct BLEPeerRegistryTests {
             isConnected: true,
             now: firstSeen
         )
+        let first = try #require(firstResult)
 
         #expect(first.isNewPeer)
         #expect(!first.wasDisconnected)
@@ -27,7 +28,7 @@ struct BLEPeerRegistryTests {
         #expect(registry.nickname(for: peerID, connectedOnly: true) == "alice")
 
         registry.markDisconnected(peerID)
-        let reconnect = registry.upsertVerifiedAnnounce(
+        let reconnectResult = registry.upsertVerifiedAnnounce(
             peerID: peerID,
             nickname: "alice-renamed",
             noisePublicKey: Data([1, 2, 3]),
@@ -35,6 +36,7 @@ struct BLEPeerRegistryTests {
             isConnected: true,
             now: firstSeen.addingTimeInterval(1)
         )
+        let reconnect = try #require(reconnectResult)
 
         #expect(!reconnect.isNewPeer)
         #expect(reconnect.wasDisconnected)
@@ -42,6 +44,85 @@ struct BLEPeerRegistryTests {
         #expect(registry.info(for: peerID)?.nickname == "alice-renamed")
     }
 
+    @Test("pinned signing key cannot be silently replaced by a later announce")
+    func upsertVerifiedAnnounceRefusesToReplacePinnedSigningKey() throws {
+        var registry = BLEPeerRegistry()
+        let peerID = PeerID(str: "1122334455667788")
+        let noiseKey = Data(repeating: 0x11, count: 32)
+        let victimSigningKey = Data(repeating: 0x42, count: 32)
+        let attackerSigningKey = Data(repeating: 0x66, count: 32)
+        let firstSeen = Date(timeIntervalSince1970: 100)
+
+        let pinResult = registry.upsertVerifiedAnnounce(
+            peerID: peerID,
+            nickname: "victim",
+            noisePublicKey: noiseKey,
+            signingPublicKey: victimSigningKey,
+            isConnected: true,
+            now: firstSeen
+        )
+        #expect(pinResult != nil)
+
+        // Attacker replays the victim's noiseKey/peerID with their own
+        // signing key and nickname; the upsert must be refused wholesale.
+        let attack = registry.upsertVerifiedAnnounce(
+            peerID: peerID,
+            nickname: "attacker",
+            noisePublicKey: noiseKey,
+            signingPublicKey: attackerSigningKey,
+            isConnected: true,
+            now: firstSeen.addingTimeInterval(1)
+        )
+
+        #expect(attack == nil)
+        let info = try #require(registry.info(for: peerID))
+        #expect(info.nickname == "victim")
+        #expect(info.signingPublicKey == victimSigningKey)
+
+        // A legitimate re-announce with the pinned key is still accepted.
+        let legit = registry.upsertVerifiedAnnounce(
+            peerID: peerID,
+            nickname: "victim-renamed",
+            noisePublicKey: noiseKey,
+            signingPublicKey: victimSigningKey,
+            isConnected: true,
+            now: firstSeen.addingTimeInterval(2)
+        )
+        #expect(legit != nil)
+        #expect(registry.info(for: peerID)?.nickname == "victim-renamed")
+    }
+
+    @Test("announce without a signing key keeps the pinned key")
+    func upsertVerifiedAnnounceKeepsPinnedSigningKeyWhenAnnounceOmitsIt() throws {
+        var registry = BLEPeerRegistry()
+        let peerID = PeerID(str: "1122334455667788")
+        let noiseKey = Data(repeating: 0x11, count: 32)
+        let signingKey = Data(repeating: 0x42, count: 32)
+        let firstSeen = Date(timeIntervalSince1970: 100)
+
+        let initialResult = registry.upsertVerifiedAnnounce(
+            peerID: peerID,
+            nickname: "alice",
+            noisePublicKey: noiseKey,
+            signingPublicKey: signingKey,
+            isConnected: true,
+            now: firstSeen
+        )
+        #expect(initialResult != nil)
+
+        let update = registry.upsertVerifiedAnnounce(
+            peerID: peerID,
+            nickname: "alice",
+            noisePublicKey: noiseKey,
+            signingPublicKey: nil,
+            isConnected: true,
+            now: firstSeen.addingTimeInterval(1)
+        )
+
+        #expect(update != nil)
+        #expect(registry.info(for: peerID)?.signingPublicKey == signingKey)
+    }
+
     @Test("reachability keeps recent verified offline peers only when mesh is attached")
     func reachabilityRequiresMeshAttachmentForOfflinePeers() {
         let offlinePeer = PeerID(str: "1122334455667788")