Merge pull request #876 from qutad/feat/announce-capability-bits

feat: Add announce capability bit assignments

app/src/main/java/com/bitchat/android/model/PeerCapabilities.kt

@@ -29,9 +29,23 @@ data class PeerCapabilities(val rawValue: Long) : Parcelable {
     companion object {
         val NONE = PeerCapabilities(0)
 
+        val PREKEYS = PeerCapabilities(1L shl 0)
+        val WIFI_BULK = PeerCapabilities(1L shl 1)
+        val GATEWAY = PeerCapabilities(1L shl 2)
+        val GROUPS = PeerCapabilities(1L shl 3)
+        val BOARD = PeerCapabilities(1L shl 4)
+        val VOUCH = PeerCapabilities(1L shl 5)
+        val MESH_DIAGNOSTICS = PeerCapabilities(1L shl 6)
+        val BRIDGE = PeerCapabilities(1L shl 7)
+
         /** Noise-encrypted private BitchatFilePacket using payload type 0x20. */
         val PRIVATE_MEDIA = PeerCapabilities(1L shl 8)
 
+        val PRIVATE_MEDIA_RECEIPTS = PeerCapabilities(1L shl 9)
+
+        /** Reserved by iOS; decode it but do not advertise or act on it. */
+        val NON_DESTRUCTIVE_NOISE_REPLACEMENT = PeerCapabilities(1L shl 10)
+
         /** Capabilities implemented by this Android build. */
         val LOCAL_SUPPORTED = PRIVATE_MEDIA
 

app/src/test/kotlin/com/bitchat/android/model/IdentityAnnouncementTest.kt

@@ -12,9 +12,38 @@ class IdentityAnnouncementTest {
     private val signingKey = ByteArray(32) { 0x22 }
 
     @Test
-    fun `private media capability uses iOS little-endian bytes`() {
+    fun `capability assignments and encoding match iOS`() {
+        assertEquals(1L shl 0, PeerCapabilities.PREKEYS.rawValue)
+        assertEquals(1L shl 1, PeerCapabilities.WIFI_BULK.rawValue)
+        assertEquals(1L shl 2, PeerCapabilities.GATEWAY.rawValue)
+        assertEquals(1L shl 3, PeerCapabilities.GROUPS.rawValue)
+        assertEquals(1L shl 4, PeerCapabilities.BOARD.rawValue)
+        assertEquals(1L shl 5, PeerCapabilities.VOUCH.rawValue)
+        assertEquals(1L shl 6, PeerCapabilities.MESH_DIAGNOSTICS.rawValue)
+        assertEquals(1L shl 7, PeerCapabilities.BRIDGE.rawValue)
+        assertEquals(1L shl 8, PeerCapabilities.PRIVATE_MEDIA.rawValue)
+        assertEquals(1L shl 9, PeerCapabilities.PRIVATE_MEDIA_RECEIPTS.rawValue)
+        assertEquals(1L shl 10, PeerCapabilities.NON_DESTRUCTIVE_NOISE_REPLACEMENT.rawValue)
+
+        val assigned = PeerCapabilities((1L shl 11) - 1)
+        assertArrayEquals(byteArrayOf(0xFF.toByte(), 0x07), assigned.encoded())
+        assertEquals(assigned, PeerCapabilities.decode(assigned.encoded()))
+    }
+
+    @Test
+    fun `capability encoding is minimal and preserves low 64 unknown bits`() {
+        assertArrayEquals(byteArrayOf(0x00), PeerCapabilities.NONE.encoded())
+        assertArrayEquals(byteArrayOf(0x01), PeerCapabilities.PREKEYS.encoded())
         assertArrayEquals(byteArrayOf(0x00, 0x01), PeerCapabilities.PRIVATE_MEDIA.encoded())
-        assertTrue(PeerCapabilities.decode(byteArrayOf(0x00, 0x01)).contains(PeerCapabilities.PRIVATE_MEDIA))
+
+        val future = PeerCapabilities.decode(
+            byteArrayOf(0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80.toByte(), 0x55)
+        )
+        assertEquals(Long.MIN_VALUE or 1L, future.rawValue)
+        assertArrayEquals(
+            byteArrayOf(0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80.toByte()),
+            future.encoded()
+        )
     }
 
     @Test
@@ -71,5 +100,6 @@ class IdentityAnnouncementTest {
                 .capabilities!!
                 .contains(PeerCapabilities.PRIVATE_MEDIA)
         )
+        assertEquals(PeerCapabilities.PRIVATE_MEDIA, PeerCapabilities.LOCAL_SUPPORTED)
     }
 }

docs/ANNOUNCEMENT_GOSSIP.md

@@ -29,9 +29,16 @@ Existing TLVs (unchanged):
 
 Other optional extension:
 
-- `0x05` CAPABILITIES: Minimal little-endian feature bitfield. Bit 8 advertises
-  authenticated Noise private media (`PRIVATE_MEDIA_V1`); its exact value is
-  `00 01`. An empty value is valid and means no advertised capabilities.
+- `0x05` CAPABILITIES: Minimal little-endian feature bitfield. Assigned bits
+  match iOS: 0 prekeys, 1 Wi-Fi bulk, 2 gateway, 3 private groups, 4 board,
+  5 vouch, 6 mesh diagnostics, 7 bridge, 8 authenticated Noise private media,
+  9 private-media receipts, and 10 reserved non-destructive Noise replacement.
+  Bit 8's exact value is `00 01`. An empty value is valid and means no
+  advertised capabilities. For this announcement TLV, unknown bits and bytes
+  beyond the low 64 bits must be tolerated for forward compatibility. This
+  tolerance does not apply to the Noise-authenticated peer-state payload
+  `0x21`, whose capability field must be canonical and 1...8 bytes; see
+  `PRIVATE_MEDIA_V1.md`.
 
 New TLV (optional):
 
@@ -69,6 +76,12 @@ This matches the on‑wire 8‑byte `senderID`/`recipientID` encoding used in th
   security-sensitive bit is trusted only after the signed announcement key is
   bound to the matching remote static key from a live Noise handshake; see
   `PRIVATE_MEDIA_V1.md`.
+- Capability bits are independent discovery hints. Implementations advertise
+  only wire features they implement and must not infer support from platform,
+  app version, or unrelated transports with similar names.
+- Private-media receipts and retry (bit 9) require the current Noise
+  generation's authenticated `0x21` peer state to prove both bits 8 and 9. An
+  announcement alone never authorizes that behavior.
 - If a `0x04` TLV is present:
   - Interpret the value as `N = length / 8` peer IDs (ignore trailing non‑aligned bytes).
   - Each 8‑byte chunk is decoded back to a 16‑hex‑char peer ID string (lowercase).