- Share only the first chunk of inbound sessions instead of the whole key history

- Download keys if the user is unknown (first invite)

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/crypto/CryptoService.kt

@@ -40,6 +40,7 @@ import org.matrix.android.sdk.api.session.crypto.verification.VerificationServic
 import org.matrix.android.sdk.api.session.events.model.Content
 import org.matrix.android.sdk.api.session.events.model.Event
 import org.matrix.android.sdk.api.session.events.model.content.RoomKeyWithHeldContent
+import org.matrix.android.sdk.internal.database.helper.SessionInfoPair
 
 interface CryptoService {
 
@@ -178,7 +179,12 @@ interface CryptoService {
     fun prepareToEncrypt(roomId: String, callback: MatrixCallback<Unit>)
 
     /**
-     * Share existing inbound sessions with the provided userId devices
+     * Share all existing inbound sessions to the provided userId devices
      */
     fun sendSharedHistoryKeys(roomId: String, userId: String)
+
+    /**
+     * Share all inbound sessions of the last chunk messages to the provided userId devices
+     */
+    fun sendSharedHistoryKeysToLastChunk(roomId: String, userId: String, sessionInfoSet: Set<SessionInfoPair>?)
 }

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/DefaultCryptoService.kt

@@ -92,6 +92,7 @@ import org.matrix.android.sdk.internal.crypto.tasks.SetDeviceNameTask
 import org.matrix.android.sdk.internal.crypto.tasks.UploadKeysTask
 import org.matrix.android.sdk.internal.crypto.verification.DefaultVerificationService
 import org.matrix.android.sdk.internal.crypto.verification.VerificationMessageProcessor
+import org.matrix.android.sdk.internal.database.helper.SessionInfoPair
 import org.matrix.android.sdk.internal.di.DeviceId
 import org.matrix.android.sdk.internal.di.MoshiProvider
 import org.matrix.android.sdk.internal.di.UserId
@@ -1337,6 +1338,34 @@ internal class DefaultCryptoService @Inject constructor(
         }
     }
 
+    override fun sendSharedHistoryKeysToLastChunk(roomId: String, userId: String, sessionInfoSet: Set<SessionInfoPair>?) {
+        cryptoCoroutineScope.launch(coroutineDispatchers.crypto) {
+            runCatching {
+                deviceListManager.downloadKeys(listOf(userId), false)
+            }.mapCatching {
+                val userDevices = cryptoStore.getUserDevices(userId)
+                userDevices?.forEach {
+                    // Lets share the provided inbound sessions for every user device
+                    val deviceId = it.key
+                    sessionInfoSet?.mapNotNull { sessionInfoPair ->
+                        // Get inbound session from sessionId and sessionKey
+                        cryptoStore.getInboundGroupSession(sessionInfoPair.first, sessionInfoPair.second)
+                    }?.filter { inboundGroupSession ->
+                        // Filter only sessions with sharedHistory enabled
+                        inboundGroupSession.sharedHistory
+                    }?.forEach { inboundGroupSession ->
+                        // Share the session to userId with deviceId
+                        val exportedKeys = inboundGroupSession.exportKeys()
+                        val algorithm = exportedKeys?.algorithm
+                        val decryptor = roomDecryptorProvider.getRoomDecryptor(roomId, algorithm)
+                        decryptor?.shareKeysWithDevice(exportedKeys, deviceId, userId)
+                        Timber.i("## CRYPTO | Sharing inbound session")
+                    }
+                }
+            }
+        }
+    }
+
     override fun sendSharedHistoryKeys(roomId: String, userId: String) {
         cryptoCoroutineScope.launch(coroutineDispatchers.crypto) {
             val userDevices = cryptoStore.getUserDevices(userId)
@@ -1347,7 +1376,7 @@ internal class DefaultCryptoService @Inject constructor(
                 inboundSessions.filter { inboundGroupSession ->
                     inboundGroupSession.sharedHistory
                 }.forEach { inboundGroupSession ->
-                    // Share the session with the to userId with deviceId
+                    // Share the session to userId with deviceId
                     val exportedKeys = inboundGroupSession.exportKeys()
                     val algorithm = exportedKeys?.algorithm
                     val decryptor = roomDecryptorProvider.getRoomDecryptor(roomId, algorithm)

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/database/helper/ChunkEntityHelper.kt

@@ -18,7 +18,10 @@ package org.matrix.android.sdk.internal.database.helper
 
 import io.realm.Realm
 import io.realm.kotlin.createObject
+import org.matrix.android.sdk.api.session.events.model.content.EncryptedEventContent
+import org.matrix.android.sdk.api.session.events.model.toModel
 import org.matrix.android.sdk.api.session.room.model.RoomMemberContent
+import org.matrix.android.sdk.internal.database.mapper.asDomain
 import org.matrix.android.sdk.internal.database.model.ChunkEntity
 import org.matrix.android.sdk.internal.database.model.CurrentStateEventEntityFields
 import org.matrix.android.sdk.internal.database.model.EventAnnotationsSummaryEntity
@@ -31,6 +34,7 @@ import org.matrix.android.sdk.internal.database.model.RoomMemberSummaryEntityFie
 import org.matrix.android.sdk.internal.database.model.TimelineEventEntity
 import org.matrix.android.sdk.internal.database.model.TimelineEventEntityFields
 import org.matrix.android.sdk.internal.database.query.find
+import org.matrix.android.sdk.internal.database.query.findLastForwardChunkOfRoom
 import org.matrix.android.sdk.internal.database.query.getOrCreate
 import org.matrix.android.sdk.internal.database.query.where
 import org.matrix.android.sdk.internal.session.room.timeline.PaginationDirection
@@ -180,3 +184,14 @@ internal fun ChunkEntity.isMoreRecentThan(chunkToCheck: ChunkEntity): Boolean {
     // We don't know, so we assume it's false
     return false
 }
+
+internal fun ChunkEntity.Companion.findLatestSessionInfo(realm: Realm, roomId: String): Set<SessionInfoPair>? =
+        ChunkEntity.findLastForwardChunkOfRoom(realm, roomId)?.timelineEvents?.mapNotNull { timelineEvent ->
+            timelineEvent?.root?.asDomain()?.content?.toModel<EncryptedEventContent>()?.let { content ->
+                content.sessionId ?:  return@mapNotNull null
+                content.senderKey ?:  return@mapNotNull null
+                Pair(content.sessionId, content.senderKey)
+            }
+        }?.toSet()
+
+internal typealias SessionInfoPair = Pair<String, String>

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/membership/DefaultMembershipService.kt

@@ -29,7 +29,9 @@ import org.matrix.android.sdk.api.session.room.members.MembershipService
 import org.matrix.android.sdk.api.session.room.members.RoomMemberQueryParams
 import org.matrix.android.sdk.api.session.room.model.Membership
 import org.matrix.android.sdk.api.session.room.model.RoomMemberSummary
+import org.matrix.android.sdk.internal.database.helper.findLatestSessionInfo
 import org.matrix.android.sdk.internal.database.mapper.asDomain
+import org.matrix.android.sdk.internal.database.model.ChunkEntity
 import org.matrix.android.sdk.internal.database.model.RoomMemberSummaryEntity
 import org.matrix.android.sdk.internal.database.model.RoomMemberSummaryEntityFields
 import org.matrix.android.sdk.internal.database.model.RoomMembersLoadStatusType
@@ -141,7 +143,10 @@ internal class DefaultMembershipService @AssistedInject constructor(
     }
 
     override suspend fun invite(userId: String, reason: String?) {
-        cryptoService.sendSharedHistoryKeys(roomId, userId)
+        val sessionInfoSet = Realm.getInstance(monarchy.realmConfiguration).use {
+            ChunkEntity.findLatestSessionInfo(it, roomId)
+        }
+        cryptoService.sendSharedHistoryKeysToLastChunk(roomId, userId, sessionInfoSet)
         val params = InviteTask.Params(roomId, userId, reason)
         inviteTask.execute(params)
     }