Harden public intake bounds against untrusted growth (#1451)

* Bound public rate-limit buckets against attacker-keyed growth. Keep the NIP-13 PoW sender bypass, skip content-bucket minting on sender reject, and evict idle/oldest entries at a hard cap. Co-authored-by: Cursor <cursoragent@cursor.com> * Stop Cashu-looking text from skipping long-message guards. Oversized public content always collapses and takes the plain formatting path so remote tokens cannot force layout/regex DoS. Co-authored-by: Cursor <cursoragent@cursor.com> * Cap teleported geohash participant markers. Bound the set with FIFO eviction, clear it on channel switch, and prune markers that leave the visible participant list. Co-authored-by: Cursor <cursoragent@cursor.com> * Bound untrusted Nostr relay frames and event tags. Reject oversized inbound messages before JSON parse, cap tag arrays/values at decode, and stop logging raw tag contents. Co-authored-by: Cursor <cursoragent@cursor.com> * Fail soft when Noise handshake state is unexpectedly missing. Replace the initiator startHandshake force unwrap with a guard that throws invalidState instead of crashing. Co-authored-by: Cursor <cursoragent@cursor.com> * Cap geohash nickname cache from remote Nostr events. FIFO-evict at capacity, clear on channel switch, and prune nicknames that leave the visible participant list. Co-authored-by: Cursor <cursoragent@cursor.com> * Avoid overlapping exclusive access in the rate limiter. Make bucket helpers static so inout dictionary updates do not conflict with a mutating call on self. Co-authored-by: Cursor <cursoragent@cursor.com> * Fix rate-limiter tests for mutating allow under #expect. Call allow outside the macro so Swift Testing does not capture an immutable copy of the struct. Co-authored-by: Cursor <cursoragent@cursor.com> * Drop unused WebSocket data helper; reset rate limiter on panic wipe. dataWithinInboundLimit replaced the unbounded path, and panic clear should not leave public intake buckets behind. Co-authored-by: Cursor <cursoragent@cursor.com> --------- Co-authored-by: Cursor <cursoragent@cursor.com>
2026-07-25 13:45:20 +00:00 · 2026-07-25 12:25:46 +02:00
parent 733098bb63
commit 593fd7d737
18 changed files with 504 additions and 35 deletions
@@ -7,45 +7,146 @@ final class LocationPresenceStore: ObservableObject {
    @Published private(set) var geoNicknames: [String: String] = [:]
    @Published private(set) var teleportedGeo: Set<String> = []

+    private let teleportedGeoCapacity: Int
+    private var teleportedGeoOrder: [String] = []
+    private let geoNicknameCapacity: Int
+    private var geoNicknameOrder: [String] = []
+
+    init(
+        teleportedGeoCapacity: Int = TransportConfig.geoTeleportedParticipantsCap,
+        geoNicknameCapacity: Int = TransportConfig.geoNicknameParticipantsCap
+    ) {
+        self.teleportedGeoCapacity = max(0, teleportedGeoCapacity)
+        self.geoNicknameCapacity = max(0, geoNicknameCapacity)
+    }
+
    func setCurrentGeohash(_ geohash: String?) {
-        currentGeohash = geohash?.lowercased()
+        let normalized = geohash?.lowercased()
+        if currentGeohash != normalized {
+            // Presence markers are scoped to the active geohash channel.
+            clearTeleportedGeo()
+            clearGeoNicknames()
+        }
+        currentGeohash = normalized
    }

    func setNickname(_ nickname: String, for pubkeyHex: String) {
-        geoNicknames[pubkeyHex.lowercased()] = nickname
+        guard geoNicknameCapacity > 0 else {
+            clearGeoNicknames()
+            return
+        }
+
+        let key = pubkeyHex.lowercased()
+        if geoNicknames[key] != nil {
+            geoNicknames[key] = nickname
+            return
+        }
+
+        while geoNicknameOrder.count >= geoNicknameCapacity, let oldest = geoNicknameOrder.first {
+            geoNicknameOrder.removeFirst()
+            geoNicknames.removeValue(forKey: oldest)
+        }
+
+        geoNicknames[key] = nickname
+        geoNicknameOrder.append(key)
    }

    func replaceGeoNicknames(_ nicknames: [String: String]) {
-        geoNicknames = Dictionary(
-            uniqueKeysWithValues: nicknames.map { key, value in
-                (key.lowercased(), value)
-            }
-        )
+        guard geoNicknameCapacity > 0 else {
+            clearGeoNicknames()
+            return
+        }
+
+        var seen: Set<String> = []
+        var ordered: [String] = []
+        var normalized: [String: String] = [:]
+        for (key, value) in nicknames {
+            let lower = key.lowercased()
+            guard seen.insert(lower).inserted else { continue }
+            ordered.append(lower)
+            normalized[lower] = value
+        }
+        if ordered.count > geoNicknameCapacity {
+            let kept = Array(ordered.suffix(geoNicknameCapacity))
+            ordered = kept
+            normalized = Dictionary(uniqueKeysWithValues: kept.compactMap { key in
+                normalized[key].map { (key, $0) }
+            })
+        }
+        geoNicknameOrder = ordered
+        geoNicknames = normalized
    }

    func clearGeoNicknames() {
        geoNicknames.removeAll()
+        geoNicknameOrder.removeAll()
+    }
+
+    func retainGeoNicknames(keeping pubkeys: Set<String>) {
+        let allowed = Set(pubkeys.map { $0.lowercased() })
+        geoNicknameOrder = geoNicknameOrder.filter { allowed.contains($0) }
+        geoNicknames = geoNicknames.filter { allowed.contains($0.key) }
    }

    func markTeleported(_ pubkeyHex: String) {
-        teleportedGeo.insert(pubkeyHex.lowercased())
+        guard teleportedGeoCapacity > 0 else {
+            clearTeleportedGeo()
+            return
+        }
+
+        let key = pubkeyHex.lowercased()
+        guard !teleportedGeo.contains(key) else { return }
+
+        while teleportedGeoOrder.count >= teleportedGeoCapacity, let oldest = teleportedGeoOrder.first {
+            teleportedGeoOrder.removeFirst()
+            teleportedGeo.remove(oldest)
+        }
+
+        teleportedGeo.insert(key)
+        teleportedGeoOrder.append(key)
    }

    func clearTeleported(_ pubkeyHex: String) {
-        teleportedGeo.remove(pubkeyHex.lowercased())
+        let key = pubkeyHex.lowercased()
+        teleportedGeo.remove(key)
+        teleportedGeoOrder.removeAll { $0 == key }
    }

    func replaceTeleportedGeo(_ pubkeys: Set<String>) {
-        teleportedGeo = Set(pubkeys.map { $0.lowercased() })
+        guard teleportedGeoCapacity > 0 else {
+            clearTeleportedGeo()
+            return
+        }
+
+        var seen: Set<String> = []
+        var ordered: [String] = []
+        for key in pubkeys.map({ $0.lowercased() }) where !seen.contains(key) {
+            seen.insert(key)
+            ordered.append(key)
+        }
+        if ordered.count > teleportedGeoCapacity {
+            ordered = Array(ordered.suffix(teleportedGeoCapacity))
+        }
+        teleportedGeoOrder = ordered
+        teleportedGeo = Set(ordered)
+    }
+
+    func retainTeleportedGeo(keeping pubkeys: Set<String>) {
+        let allowed = Set(pubkeys.map { $0.lowercased() })
+        teleportedGeoOrder = teleportedGeoOrder.filter { allowed.contains($0) }
+        teleportedGeo = teleportedGeo.intersection(allowed)
    }

    func clearTeleportedGeo() {
        teleportedGeo.removeAll()
+        teleportedGeoOrder.removeAll()
    }

    func reset() {
        currentGeohash = nil
        geoNicknames.removeAll()
+        geoNicknameOrder.removeAll()
        teleportedGeo.removeAll()
+        teleportedGeoOrder.removeAll()
    }
 }
@@ -66,7 +66,10 @@ class NoiseSession {
            
            // Only initiator writes the first message
            if role == .initiator {
-                let message = try handshakeState!.writeMessage()
+                guard let handshake = handshakeState else {
+                    throw NoiseSessionError.invalidState
+                }
+                let message = try handshake.writeMessage()
                sentHandshakeMessages.append(message)
                return message
            } else {
@@ -700,6 +700,10 @@ struct NostrEvent: Codable {
              let content = dict["content"] as? String else {
            throw NostrError.invalidEvent
        }
+
+        guard Self.isWithinInboundTagLimits(tags) else {
+            throw NostrError.invalidEvent
+        }
        
        self.id = dict["id"] as? String ?? ""
        self.pubkey = pubkey
@@ -709,6 +713,21 @@ struct NostrEvent: Codable {
        self.content = content
        self.sig = dict["sig"] as? String
    }
+
+    /// Bounds untrusted relay tag arrays so attackers cannot force large
+    /// allocations or expensive joins on the inbound hot path.
+    static func isWithinInboundTagLimits(_ tags: [[String]]) -> Bool {
+        guard tags.count <= TransportConfig.nostrMaxEventTags else { return false }
+
+        for tag in tags {
+            guard tag.count <= TransportConfig.nostrMaxEventTagValues else { return false }
+            guard tag.allSatisfy({ $0.utf8.count <= TransportConfig.nostrMaxEventTagValueBytes }) else {
+                return false
+            }
+        }
+
+        return true
+    }
    
    func sign(with key: P256K.Schnorr.PrivateKey) throws -> NostrEvent {
        let (eventId, eventIdHash) = try calculateEventId()
@@ -1480,7 +1480,7 @@ private enum ParsedInbound {
    case notice(String)
    
    init?(_ message: URLSessionWebSocketTask.Message) {
-        guard let data = message.data,
+        guard let data = message.dataWithinInboundLimit,
              let array = try? JSONSerialization.jsonObject(with: data) as? [Any],
              array.count >= 2,
              let type = array[0] as? String else {
@@ -1525,11 +1525,19 @@ private enum ParsedInbound {
 }

 private extension URLSessionWebSocketTask.Message {
-    var data: Data? {
+    /// Prefer rejecting oversized frames before UTF-8/Data materialization
+    /// where we can (string length), and always before JSON parse.
+    var dataWithinInboundLimit: Data? {
+        let maxBytes = TransportConfig.nostrMaxInboundMessageBytes
        switch self {
-        case .string(let text): text.data(using: .utf8)
-        case .data(let data):   data
-        @unknown default:       nil
+        case .string(let text):
+            guard text.utf8.count <= maxBytes else { return nil }
+            return text.data(using: .utf8)
+        case .data(let data):
+            guard data.count <= maxBytes else { return nil }
+            return data
+        @unknown default:
+            return nil
        }
    }
 }
@@ -251,9 +251,9 @@ final class MessageFormattingEngine {
        isSelf: Bool,
        isMentioned: Bool
    ) -> AttributedString {
-        // For very long content without special tokens, use plain formatting
-        let containsCashu = containsCashuToken(content)
-        if (content.count > 4000 || content.hasVeryLongToken(threshold: 1024)) && !containsCashu {
+        // For very long content, use plain formatting to avoid expensive
+        // regex/detector work. Cashu presence must not disable this guard.
+        if content.isOversizedForRichFormatting() {
            return formatPlainContent(content, baseColor: baseColor, isSelf: isSelf)
        }

@@ -46,6 +46,7 @@ enum TransportConfig {
    static let privateChatCap: Int = 1337
    static let meshTimelineCap: Int = 1337
    static let geoTimelineCap: Int = 1337
+    static let geoNicknameParticipantsCap: Int = 1337
    static let contentLRUCap: Int = 2000
    static let geoSamplingEventLRUCap: Int = 2000

@@ -81,6 +82,11 @@ enum TransportConfig {
    static let nostrDuplicateEventLogInterval: Int = 50
    // Sample interval for per-event debug logs on the inbound hot path.
    static let nostrInboundEventLogInterval: Int = 100
+    // Reject oversized/untrusted relay frames before JSON parse / store.
+    static let nostrMaxInboundMessageBytes: Int = 256 * 1024
+    static let nostrMaxEventTags: Int = 64
+    static let nostrMaxEventTagValues: Int = 16
+    static let nostrMaxEventTagValueBytes: Int = 1024

    // Conversation store diagnostics (field observability)
    // Sample interval for the periodic store-audit "OK" heartbeat line
@@ -98,6 +104,12 @@ enum TransportConfig {
    static let uiSenderRateBucketRefillPerSec: Double = 1.0
    static let uiContentRateBucketCapacity: Double = 3
    static let uiContentRateBucketRefillPerSec: Double = 0.5
+    // Bound attacker-keyed bucket maps (sender IDs / content digests).
+    static let uiSenderRateBucketMaxEntries: Int = 2000
+    static let uiContentRateBucketMaxEntries: Int = 2000
+    static let uiRateBucketIdleTTL: TimeInterval = 10 * 60
+    // Cap teleported-participant markers so remote events cannot grow the set.
+    static let geoTeleportedParticipantsCap: Int = 1337

    // UI sleeps/delays
    static let uiStartupInitialDelaySeconds: TimeInterval = 1.0
@@ -71,12 +71,8 @@ final class ChatMessageFormatter {
            let content = message.content
            let nsContent = content as NSString
            let nsLen = nsContent.length
-            let containsCashuEarly: Bool = {
-                let regex = Patterns.quickCashuPresence
-                return regex.numberOfMatches(in: content, options: [], range: NSRange(location: 0, length: nsLen)) > 0
-            }()

-            if (content.count > 4000 || content.hasVeryLongToken(threshold: 1024)) && !containsCashuEarly {
+            if content.isOversizedForRichFormatting() {
                var plainStyle = AttributeContainer()
                plainStyle.foregroundColor = baseColor
                plainStyle.font = isSelf
@@ -1183,6 +1183,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, TransportEventDele
        identityManager.clearAllIdentityData()
        peerIdentityStore.clearAll()
        locationPresenceStore.reset()
+        publicRateLimiter.reset()

        // Clear persistent favorites from keychain
        FavoritesPersistenceService.shared.clearAllFavorites()
@@ -156,6 +156,17 @@ private extension ChatViewModelBootstrapper {
                viewModel?.objectWillChange.send()
            }
            .store(in: &viewModel.cancellables)
+
+        viewModel.participantTracker.$visiblePeople
+            .receive(on: DispatchQueue.main)
+            .sink { [weak viewModel] people in
+                Task { @MainActor [weak viewModel] in
+                    let visible = Set(people.map { $0.id })
+                    viewModel?.locationPresenceStore.retainTeleportedGeo(keeping: visible)
+                    viewModel?.locationPresenceStore.retainGeoNicknames(keeping: visible)
+                }
+            }
+            .store(in: &viewModel.cancellables)
    }

    func loadPersistedViewState() {
@@ -26,6 +26,10 @@ struct MessageRateLimiter {
            }
            return false
        }
+
+        func isIdle(since now: Date, idleTTL: TimeInterval) -> Bool {
+            now.timeIntervalSince(lastRefill) >= idleTTL
+        }
    }

    private var senderBuckets: [String: TokenBucket] = [:]
@@ -35,17 +39,26 @@ struct MessageRateLimiter {
    private let senderRefill: Double
    private let contentCapacity: Double
    private let contentRefill: Double
+    private let maxSenderBuckets: Int
+    private let maxContentBuckets: Int
+    private let bucketIdleTTL: TimeInterval

    init(
        senderCapacity: Double,
        senderRefillPerSec: Double,
        contentCapacity: Double,
-        contentRefillPerSec: Double
+        contentRefillPerSec: Double,
+        maxSenderBuckets: Int = TransportConfig.uiSenderRateBucketMaxEntries,
+        maxContentBuckets: Int = TransportConfig.uiContentRateBucketMaxEntries,
+        bucketIdleTTL: TimeInterval = TransportConfig.uiRateBucketIdleTTL
    ) {
        self.senderCapacity = senderCapacity
        self.senderRefill = senderRefillPerSec
        self.contentCapacity = contentCapacity
        self.contentRefill = contentRefillPerSec
+        self.maxSenderBuckets = max(1, maxSenderBuckets)
+        self.maxContentBuckets = max(1, maxContentBuckets)
+        self.bucketIdleTTL = bucketIdleTTL
    }

    /// - Parameter powBits: validated NIP-13 difficulty of the event
@@ -58,25 +71,83 @@ struct MessageRateLimiter {
        if powBits >= NostrPoW.rateLimitBypassBits {
            senderAllowed = true
        } else {
-            var senderBucket = senderBuckets[senderKey] ?? TokenBucket(
+            var senderBucket = Self.bucket(
+                for: senderKey,
+                in: &senderBuckets,
                capacity: senderCapacity,
-                tokens: senderCapacity,
                refillPerSec: senderRefill,
-                lastRefill: now
+                maxBuckets: maxSenderBuckets,
+                idleTTL: bucketIdleTTL,
+                now: now
            )
            senderAllowed = senderBucket.allow(now: now)
            senderBuckets[senderKey] = senderBucket
        }

-        var contentBucket = contentBuckets[contentKey] ?? TokenBucket(
+        // Rejected senders must not mint attacker-keyed content entries.
+        guard senderAllowed else { return false }
+
+        var contentBucket = Self.bucket(
+            for: contentKey,
+            in: &contentBuckets,
            capacity: contentCapacity,
-            tokens: contentCapacity,
            refillPerSec: contentRefill,
-            lastRefill: now
+            maxBuckets: maxContentBuckets,
+            idleTTL: bucketIdleTTL,
+            now: now
        )
        let contentAllowed = contentBucket.allow(now: now)
        contentBuckets[contentKey] = contentBucket

-        return senderAllowed && contentAllowed
+        return contentAllowed
+    }
+
+    mutating func reset() {
+        senderBuckets.removeAll()
+        contentBuckets.removeAll()
+    }
+
+    var bucketCountsForTesting: (sender: Int, content: Int) {
+        (senderBuckets.count, contentBuckets.count)
+    }
+
+    // Static so we can take `inout` on a stored dictionary without overlapping
+    // exclusive access through a mutating method on `self`.
+    private static func bucket(
+        for key: String,
+        in buckets: inout [String: TokenBucket],
+        capacity: Double,
+        refillPerSec: Double,
+        maxBuckets: Int,
+        idleTTL: TimeInterval,
+        now: Date
+    ) -> TokenBucket {
+        if let existing = buckets[key] {
+            return existing
+        }
+
+        evictIfNeeded(from: &buckets, maxBuckets: maxBuckets, idleTTL: idleTTL, now: now)
+        return TokenBucket(
+            capacity: capacity,
+            tokens: capacity,
+            refillPerSec: refillPerSec,
+            lastRefill: now
+        )
+    }
+
+    private static func evictIfNeeded(
+        from buckets: inout [String: TokenBucket],
+        maxBuckets: Int,
+        idleTTL: TimeInterval,
+        now: Date
+    ) {
+        guard buckets.count >= maxBuckets else { return }
+
+        buckets = buckets.filter { !$0.value.isIdle(since: now, idleTTL: idleTTL) }
+        guard buckets.count >= maxBuckets else { return }
+
+        if let oldestKey = buckets.min(by: { $0.value.lastRefill < $1.value.lastRefill })?.key {
+            buckets.removeValue(forKey: oldestKey)
+        }
    }
 }
@@ -196,7 +196,10 @@ final class NostrInboundPipeline {
        // Sampled: fires for every geo event and floods dev logs in busy geohashes.
        geoEventLogCount += 1
        if geoEventLogCount == 1 || geoEventLogCount.isMultiple(of: TransportConfig.nostrInboundEventLogInterval) {
-            SecureLogger.debug("GeoTeleport: recv #\(geoEventLogCount) pub=\(event.pubkey.prefix(8))… pow=\(powBits) tags=\(event.tags.map { "[" + $0.joined(separator: ",") + "]" }.joined(separator: ","))", category: .session)
+            SecureLogger.debug(
+                "GeoTeleport: recv #\(geoEventLogCount) pub=\(event.pubkey.prefix(8))… pow=\(powBits) tagCount=\(event.tags.count)",
+                category: .session
+            )
        }

        if context.isNostrBlocked(pubkeyHexLowercased: event.pubkey) {
@@ -41,7 +41,7 @@ struct TextMessageView: View {
            // first text line; a fixed top padding left the lock's solid body
            // hanging below the line's visual center.
            HStack(alignment: .firstTextBaseline, spacing: 0) {
-                let isLong = (message.content.count > TransportConfig.uiLongMessageLengthThreshold || message.content.hasVeryLongToken(threshold: TransportConfig.uiVeryLongTokenThreshold)) && cashuLinks.isEmpty
+                let isLong = message.content.isLongForDisplay()
                let isExpanded = expandedMessageIDs.contains(message.id)
                if message.isPrivate {
                    Image(systemName: "lock.fill")
@@ -103,7 +103,7 @@ struct TextMessageView: View {
            }
            
            // Expand/Collapse for very long messages
-            if (message.content.count > TransportConfig.uiLongMessageLengthThreshold || message.content.hasVeryLongToken(threshold: TransportConfig.uiVeryLongTokenThreshold)) && cashuLinks.isEmpty {
+            if message.content.isLongForDisplay() {
                let isExpanded = expandedMessageIDs.contains(message.id)
                let labelKey = isExpanded ? LocalizedStringKey("content.message.show_less") : LocalizedStringKey("content.message.show_more")
                Button(labelKey) {
@@ -21,6 +21,26 @@ extension String {
        return current >= threshold
    }

+    /// True when the message should collapse behind Show more in the UI.
+    /// Length alone decides this — embedding a Cashu-looking token must not
+    /// disable the guard (remote DoS via unbounded layout).
+    func isLongForDisplay(
+        lengthThreshold: Int = TransportConfig.uiLongMessageLengthThreshold,
+        tokenThreshold: Int = TransportConfig.uiVeryLongTokenThreshold
+    ) -> Bool {
+        count > lengthThreshold || hasVeryLongToken(threshold: tokenThreshold)
+    }
+
+    /// True when rich formatting (regex / link detectors) should be skipped.
+    /// Cashu presence used to exempt oversized content from the plain path;
+    /// that let untrusted input force expensive formatting work.
+    func isOversizedForRichFormatting(
+        lengthThreshold: Int = 4000,
+        tokenThreshold: Int = 1024
+    ) -> Bool {
+        count > lengthThreshold || hasVeryLongToken(threshold: tokenThreshold)
+    }
+
    // Extract up to `max` distinct Cashu tokens (cashuA/cashuB), as the bare
    // bearer strings. Allow dot '.' and shorter lengths. The `cashu:` URI
    // form matches too — the token embedded after the scheme is the match.
@@ -147,6 +147,44 @@ struct AppArchitectureTests {
        #expect(store.teleportedGeo.isEmpty)
    }

+    @Test("LocationPresenceStore bounds and prunes teleported geohash participants")
+    @MainActor
+    func locationPresenceStoreBoundsTeleportedParticipants() {
+        let store = LocationPresenceStore(teleportedGeoCapacity: 2)
+
+        store.setCurrentGeohash("u4pruy")
+        store.markTeleported("AAAAAA")
+        store.markTeleported("BBBBBB")
+        store.markTeleported("CCCCCC")
+
+        #expect(store.teleportedGeo == Set(["bbbbbb", "cccccc"]))
+
+        store.retainTeleportedGeo(keeping: Set(["CCCCCC"]))
+        #expect(store.teleportedGeo == Set(["cccccc"]))
+
+        store.setCurrentGeohash("u4pruz")
+        #expect(store.teleportedGeo.isEmpty)
+    }
+
+    @Test("LocationPresenceStore bounds geohash nicknames and clears on channel switch")
+    @MainActor
+    func locationPresenceStoreBoundsGeoNicknames() {
+        let store = LocationPresenceStore(geoNicknameCapacity: 2)
+
+        store.setCurrentGeohash("u4pruy")
+        store.setNickname("alice", for: "AAAAAA")
+        store.setNickname("bob", for: "BBBBBB")
+        store.setNickname("carol", for: "CCCCCC")
+
+        #expect(store.geoNicknames == ["bbbbbb": "bob", "cccccc": "carol"])
+
+        store.retainGeoNicknames(keeping: Set(["CCCCCC"]))
+        #expect(store.geoNicknames == ["cccccc": "carol"])
+
+        store.setCurrentGeohash("u4pruz")
+        #expect(store.geoNicknames.isEmpty)
+    }
+
    @Test("PeerHandle equality and hashing use the canonical identity only")
    func peerHandleEqualityUsesCanonicalIdentity() {
        let first = PeerHandle(id: "noise:abc123", routingPeerID: PeerID(str: "peer-a"))
@@ -646,6 +646,25 @@ struct ChatViewModelFormattingTests {
        #expect(String(formatted.characters) == "<@Alice#a1b2> hello #mesh [\(message.formattedTimestamp)]")
    }

+    @Test @MainActor
+    func formatMessageAsText_longCashuFallsBackToPlain() async {
+        let (viewModel, _) = makeTestableViewModel()
+        let cashu = "cashuA" + String(repeating: "a", count: 40)
+        let longContent = "hi @bob " + cashu + " " + String(repeating: "x", count: 4_100)
+        let message = BitchatMessage(
+            id: "fmt-long-cashu",
+            sender: "Alice#a1b2",
+            content: longContent,
+            timestamp: Date(timeIntervalSince1970: 1_700_010_123),
+            isRelay: false,
+            senderPeerID: PeerID(str: "00000000000000b3")
+        )
+
+        let formatted = viewModel.formatMessageAsText(message, colorScheme: .light)
+
+        #expect(String(formatted.characters) == "<@Alice#a1b2> \(longContent) [\(message.formattedTimestamp)]")
+    }
+
    @Test @MainActor
    func formatMessageHeader_formatsSenderHeader() async {
        let (viewModel, _) = makeTestableViewModel()
@@ -323,6 +323,32 @@ struct MessageFormattingEngineTests {
        // Exactly at threshold DOES trigger (uses >= comparison)
        #expect(content.hasVeryLongToken(threshold: 50))
    }
+
+    @Test func isLongForDisplay_doesNotIgnoreCashuLinks() {
+        let cashu = "cashuA" + String(repeating: "a", count: 40)
+        let content = String(repeating: "a", count: TransportConfig.uiLongMessageLengthThreshold + 1) + " " + cashu
+
+        #expect(content.extractCashuLinks().count == 1)
+        #expect(content.isLongForDisplay())
+    }
+
+    @MainActor
+    @Test func formatMessage_longCashuMessageFallsBackToPlainContentPath() {
+        let context = MockMessageFormattingContext(nickname: "carol")
+        let cashu = "cashuA" + String(repeating: "a", count: 40)
+        let longContent = "hi @bob " + cashu + " " + String(repeating: "x", count: 4_100)
+        let message = BitchatMessage(
+            id: "long-cashu",
+            sender: "alice",
+            content: longContent,
+            timestamp: Date(timeIntervalSince1970: 1_700_000_999),
+            isRelay: false
+        )
+
+        let formatted = MessageFormattingEngine.formatMessage(message, context: context, colorScheme: .light)
+
+        #expect(String(formatted.characters) == "<@alice> \(longContent) [\(message.formattedTimestamp)]")
+    }
 }

@MainActor
@@ -116,4 +116,87 @@ struct MessageRateLimiterTests {
        #expect(plain)
        #expect(!plainExhausted)
    }
+
+    @Test("Content buckets do not grow when sender is rate limited")
+    func contentBucketsDoNotGrowAfterSenderLimit() {
+        var limiter = MessageRateLimiter(
+            senderCapacity: 1,
+            senderRefillPerSec: 0,
+            contentCapacity: 1,
+            contentRefillPerSec: 0,
+            maxSenderBuckets: 10,
+            maxContentBuckets: 10,
+            bucketIdleTTL: 60
+        )
+        let now = Date()
+
+        let first = limiter.allow(senderKey: "sender", contentKey: "content-0", now: now)
+        var rejected = true
+        for index in 1...100 {
+            if limiter.allow(senderKey: "sender", contentKey: "content-\(index)", now: now) {
+                rejected = false
+            }
+        }
+
+        #expect(first)
+        #expect(rejected)
+        #expect(limiter.bucketCountsForTesting.sender == 1)
+        #expect(limiter.bucketCountsForTesting.content == 1)
+    }
+
+    @Test("Bucket maps evict entries at configured caps")
+    func bucketMapsEvictAtConfiguredCaps() {
+        let maxEntries = 3
+        var limiter = MessageRateLimiter(
+            senderCapacity: 1,
+            senderRefillPerSec: 0,
+            contentCapacity: 1,
+            contentRefillPerSec: 0,
+            maxSenderBuckets: maxEntries,
+            maxContentBuckets: maxEntries,
+            bucketIdleTTL: 60
+        )
+        let now = Date()
+
+        for index in 0..<25 {
+            _ = limiter.allow(
+                senderKey: "sender-\(index)",
+                contentKey: "content-\(index)",
+                now: now.addingTimeInterval(TimeInterval(index))
+            )
+        }
+
+        #expect(limiter.bucketCountsForTesting.sender == maxEntries)
+        #expect(limiter.bucketCountsForTesting.content == maxEntries)
+    }
+
+    @Test("PoW bypass still creates content buckets under the cap")
+    func powBypassCreatesBoundedContentBuckets() {
+        let maxEntries = 3
+        var limiter = MessageRateLimiter(
+            senderCapacity: 1,
+            senderRefillPerSec: 0,
+            contentCapacity: 100,
+            contentRefillPerSec: 0,
+            maxSenderBuckets: maxEntries,
+            maxContentBuckets: maxEntries,
+            bucketIdleTTL: 60
+        )
+        let now = Date()
+
+        var allAllowed = true
+        for index in 0..<10 {
+            let allowed = limiter.allow(
+                senderKey: "sender",
+                contentKey: "content-\(index)",
+                powBits: NostrPoW.rateLimitBypassBits,
+                now: now.addingTimeInterval(TimeInterval(index))
+            )
+            if !allowed { allAllowed = false }
+        }
+
+        #expect(allAllowed)
+        #expect(limiter.bucketCountsForTesting.sender == 0)
+        #expect(limiter.bucketCountsForTesting.content == maxEntries)
+    }
 }
@@ -290,7 +290,65 @@ struct NostrProtocolTests {
        #expect(object["limit"] as? Int == 42)
    }

+
+    @Test func inboundNostrEventRejectsTooManyTags() throws {
+        var eventDict = Self.validInboundEventDict()
+        eventDict["tags"] = Array(
+            repeating: ["g", "u4pruyd"],
+            count: TransportConfig.nostrMaxEventTags + 1
+        )
+
+        #expect(throws: NostrError.invalidEvent) {
+            _ = try NostrEvent(from: eventDict)
+        }
+    }
+
+    @Test func inboundNostrEventRejectsTooManyTagValues() throws {
+        var eventDict = Self.validInboundEventDict()
+        eventDict["tags"] = [Array(
+            repeating: "value",
+            count: TransportConfig.nostrMaxEventTagValues + 1
+        )]
+
+        #expect(throws: NostrError.invalidEvent) {
+            _ = try NostrEvent(from: eventDict)
+        }
+    }
+
+    @Test func inboundNostrEventRejectsOversizedTagValues() throws {
+        var eventDict = Self.validInboundEventDict()
+        eventDict["tags"] = [[
+            "g",
+            String(repeating: "a", count: TransportConfig.nostrMaxEventTagValueBytes + 1)
+        ]]
+
+        #expect(throws: NostrError.invalidEvent) {
+            _ = try NostrEvent(from: eventDict)
+        }
+    }
+
+    @Test func inboundNostrEventAcceptsTagsWithinLimits() throws {
+        var eventDict = Self.validInboundEventDict()
+        eventDict["tags"] = [["g", "u4pruyd"], ["t", "teleport"]]
+
+        let event = try NostrEvent(from: eventDict)
+
+        #expect(event.tags.count == 2)
+    }
+
    // MARK: - Helpers
+    private static func validInboundEventDict() -> [String: Any] {
+        [
+            "id": String(repeating: "0", count: 64),
+            "pubkey": String(repeating: "1", count: 64),
+            "created_at": 1_234_567,
+            "kind": NostrProtocol.EventKind.ephemeralEvent.rawValue,
+            "tags": [["g", "u4pruyd"]],
+            "content": "hello",
+            "sig": String(repeating: "2", count: 128)
+        ]
+    }
+
    private static func base64URLDecode(_ s: String) -> Data? {
        var str = s.replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/")
        let rem = str.count % 4