Merge e07e3c91186877f3d59414afd8cf1baac6413e4a into 094657efa0aabbb6f71c9050149d1d01aee96400

app/src/main/java/com/bitchat/android/nostr/GeohashMessageHandler.kt

@@ -3,8 +3,11 @@ package com.bitchat.android.nostr
 import android.app.Application
 import android.util.Log
 import com.bitchat.android.model.BitchatMessage
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 import java.util.Date
 
 /**
@@ -18,7 +21,8 @@ class GeohashMessageHandler(
     private val repo: GeohashRepository,
     private val scope: CoroutineScope,
     private val dataManager: com.bitchat.android.ui.DataManager,
-    private val addChannelMessage: (String, BitchatMessage) -> Unit
+    private val addChannelMessage: (String, BitchatMessage) -> Unit,
+    private val signatureVerificationDispatcher: CoroutineDispatcher = Dispatchers.Default
 ) {
     companion object { private const val TAG = "GeohashMessageHandler" }
 
@@ -44,6 +48,13 @@ class GeohashMessageHandler(
                 if (event.kind != NostrKind.EPHEMERAL_EVENT && event.kind != NostrKind.GEOHASH_PRESENCE) return@launch
                 val tagGeo = event.tags.firstOrNull { it.size >= 2 && it[0] == "g" }?.getOrNull(1)
                 if (tagGeo == null || !tagGeo.equals(subscribedGeohash, true)) return@launch
+                val hasValidSignature = withContext(signatureVerificationDispatcher) {
+                    event.isValidSignature()
+                }
+                if (!hasValidSignature) {
+                    Log.w(TAG, "Rejecting geohash event ${event.id.take(8)}... with invalid signature")
+                    return@launch
+                }
                 if (dedupe(event.id)) return@launch
 
                 // PoW validation (if enabled) - apply to chat messages primarily

app/src/main/java/com/bitchat/android/nostr/LocationNotesManager.kt

@@ -416,6 +416,11 @@ class LocationNotesManager private constructor() {
             Log.v(TAG, "Ignoring non-text-note event: kind=${event.kind}")
             return
         }
+
+        if (!event.isValidSignature()) {
+            Log.w(TAG, "Rejecting note ${event.id.take(8)}... with invalid signature")
+            return
+        }
         
         // Check for geohash tag
         val geohashTag = event.tags.firstOrNull { it.size >= 2 && it[0] == "g" }

app/src/main/java/com/bitchat/android/nostr/NostrClient.kt

@@ -282,6 +282,11 @@ class NostrClient private constructor(private val context: Context) {
         handler: (content: String, senderPubkey: String, nickname: String?, timestamp: Int) -> Unit
     ) {
         try {
+            if (!event.isValidSignature()) {
+                Log.w(TAG, "🚫 Rejecting geohash event ${event.id.take(8)}... with invalid signature")
+                return
+            }
+
             // Check Proof of Work validation for incoming geohash events
             val powSettings = PoWPreferenceManager.getCurrentSettings()
             if (powSettings.enabled && powSettings.difficulty > 0) {

app/src/test/kotlin/com/bitchat/android/nostr/GeohashMessageHandlerSignatureTest.kt

@@ -0,0 +1,136 @@
+package com.bitchat.android.nostr
+
+import android.app.Application
+import androidx.test.core.app.ApplicationProvider
+import com.bitchat.android.ui.ChatState
+import com.bitchat.android.ui.DataManager
+import com.bitchat.android.ui.MessageManager
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+
+/**
+ * Regression coverage for GH-733: geohash events (kind 20000/20001) were accepted from the
+ * relay without Schnorr signature verification, allowing full pubkey impersonation.
+ */
+@RunWith(RobolectricTestRunner::class)
+class GeohashMessageHandlerSignatureTest {
+
+    private val application: Application = ApplicationProvider.getApplicationContext()
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    private val testDispatcher = UnconfinedTestDispatcher()
+    private val testScope = TestScope(testDispatcher)
+
+    private lateinit var chatState: ChatState
+    private lateinit var dataManager: DataManager
+    private lateinit var messageManager: MessageManager
+    private lateinit var repo: GeohashRepository
+    private lateinit var handler: GeohashMessageHandler
+
+    private val geohash = "u4pruy"
+
+    @Before
+    fun setup() {
+        chatState = ChatState(scope = testScope)
+        dataManager = DataManager(context = application)
+        messageManager = MessageManager(state = chatState)
+        repo = GeohashRepository(application, chatState, dataManager)
+        handler = GeohashMessageHandler(
+            application = application,
+            repo = repo,
+            scope = testScope,
+            dataManager = dataManager,
+            addChannelMessage = messageManager::addChannelMessage,
+            signatureVerificationDispatcher = testDispatcher
+        )
+    }
+
+    private fun buildSignedEvent(identity: NostrIdentity, content: String): NostrEvent {
+        val unsigned = NostrEvent(
+            pubkey = identity.publicKeyHex,
+            createdAt = (System.currentTimeMillis() / 1000).toInt(),
+            kind = NostrKind.EPHEMERAL_EVENT,
+            tags = listOf(listOf("g", geohash)),
+            content = content
+        )
+        return unsigned.sign(identity.privateKeyHex)
+    }
+
+    @Test
+    fun onEvent_acceptsGenuinelySignedEvent() {
+        val victim = NostrIdentity.generate()
+        val genuine = buildSignedEvent(victim, "hello from the real victim")
+
+        handler.onEvent(genuine, geohash)
+
+        val stored = chatState.getChannelMessagesValue()["geo:$geohash"]
+        assertEquals(1, stored?.size)
+        assertEquals("hello from the real victim", stored?.first()?.content)
+    }
+
+    @Test
+    fun onEvent_rejectsEventWithForgedSignature() {
+        val victim = NostrIdentity.generate()
+        val attacker = NostrIdentity.generate()
+
+        // Attacker claims the victim's pubkey but signs with their own key - a forged event.
+        val forged = buildSignedEvent(victim, "impersonated message").copy(
+            sig = NostrEvent(
+                pubkey = attacker.publicKeyHex,
+                createdAt = (System.currentTimeMillis() / 1000).toInt(),
+                kind = NostrKind.EPHEMERAL_EVENT,
+                tags = listOf(listOf("g", geohash)),
+                content = "impersonated message"
+            ).sign(attacker.privateKeyHex).sig
+        )
+
+        // Sanity check: this event is indeed invalid before we even touch the handler.
+        assertEquals(false, forged.isValidSignature())
+
+        handler.onEvent(forged, geohash)
+
+        val stored = chatState.getChannelMessagesValue()["geo:$geohash"]
+        assertNull("Forged event must not be rendered as a legitimate message", stored)
+    }
+
+    @Test
+    fun onEvent_stillAcceptsGenuineEventAfterForgedCopyWithSameIdWasRejected() {
+        val victim = NostrIdentity.generate()
+        val attacker = NostrIdentity.generate()
+        val genuine = buildSignedEvent(victim, "hello from the real victim")
+
+        // A forged event carrying the SAME id as the genuine one (ids are a content hash,
+        // independent of the signature), but signed by an attacker - relays can deliver this
+        // before the genuine copy arrives from another relay.
+        val forgedWithSameId = genuine.copy(
+            sig = NostrEvent(
+                pubkey = attacker.publicKeyHex,
+                createdAt = genuine.createdAt,
+                kind = NostrKind.EPHEMERAL_EVENT,
+                tags = listOf(listOf("g", geohash)),
+                content = "hello from the real victim"
+            ).sign(attacker.privateKeyHex).sig
+        )
+        assertEquals(genuine.id, forgedWithSameId.id)
+        assertEquals(false, forgedWithSameId.isValidSignature())
+
+        // Forged copy arrives first and must be rejected without poisoning the dedup cache.
+        handler.onEvent(forgedWithSameId, geohash)
+        assertNull(chatState.getChannelMessagesValue()["geo:$geohash"])
+
+        // The genuine copy (same id, valid signature) arrives afterwards from another relay -
+        // it must still be rendered, not silently dropped as a "duplicate".
+        handler.onEvent(genuine, geohash)
+
+        val stored = chatState.getChannelMessagesValue()["geo:$geohash"]
+        assertEquals(1, stored?.size)
+        assertEquals("hello from the real victim", stored?.first()?.content)
+    }
+}

app/src/test/kotlin/com/bitchat/android/nostr/NostrBackgroundEventProcessorTest.kt

@@ -36,17 +36,21 @@ class NostrBackgroundEventProcessorTest {
     fun `cold start processes more events than the removed handoff queue capacity`() = runBlocking {
         val application = ApplicationProvider.getApplicationContext<Application>()
         val processor = NostrBackgroundEventProcessor(application, scope)
+        val identity = NostrIdentity.generate()
+        val expectedIds = mutableSetOf<String>()
 
         repeat(300) { index ->
+            val event = NostrEvent(
+                pubkey = identity.publicKeyHex,
+                createdAt = index + 1,
+                kind = NostrKind.EPHEMERAL_EVENT,
+                tags = listOf(listOf("g", "u4pruy")),
+                content = "message-$index"
+            ).sign(identity.privateKeyHex)
+            expectedIds += event.id
+
             processor.onGeohashMessage(
-                event = NostrEvent(
-                    id = "cold-start-$index",
-                    pubkey = index.toString(16).padStart(64, '0'),
-                    createdAt = 1,
-                    kind = NostrKind.EPHEMERAL_EVENT,
-                    tags = listOf(listOf("g", "u4pruy")),
-                    content = "message-$index"
-                ),
+                event = event,
                 geohash = "u4pruy"
             )
         }
@@ -58,7 +62,7 @@ class NostrBackgroundEventProcessorTest {
         }
 
         assertEquals(
-            (0 until 300).map { "cold-start-$it" }.toSet(),
+            expectedIds,
             AppStateStore.channelMessages.value["geo:u4pruy"].orEmpty().map { it.id }.toSet()
         )
     }