Rotate our session when there is a room history visibility change since the last outboundSession

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/algorithms/megolm/MXMegolmEncryption.kt

@@ -172,6 +172,8 @@ internal class MXMegolmEncryption(
         if (session == null ||
                 // Need to make a brand new session?
                 session.needsRotation(sessionRotationPeriodMsgs, sessionRotationPeriodMs) ||
+                // Is there a room history visibility change since the last outboundSession
+                cryptoStore.needsRotationDueToVisibilityChange(roomId) ||
                 // Determine if we have shared with anyone we shouldn't have
                 session.sharedWithTooManyDevices(devicesInRoom)) {
             Timber.tag(loggerTag.value).d("roomId:$roomId Starting new megolm session because we need to rotate.")

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

@@ -341,7 +341,14 @@ internal interface IMXCryptoStore {
     fun storeCurrentOutboundGroupSessionForRoom(roomId: String, outboundGroupSession: OlmOutboundGroupSession?)
 
     /**
-     * Remove an inbound group session.
+     * Returns true if there is a room history visibility change since the latest outbound
+     * session. Specifically when the room's history visibility setting changes to
+     * world_readable or shared from invited or joined, or changes to invited or joined from world_readable or shared
+     */
+    fun needsRotationDueToVisibilityChange(roomId: String): Boolean
+
+    /**
+     * Remove an inbound group session
      *
      * @param sessionId the session identifier.
      * @param senderKey the base64-encoded curve25519 key of the sender.

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/store/db/RealmCryptoStore.kt

@@ -826,6 +826,8 @@ internal class RealmCryptoStore @Inject constructor(
                 if (outboundGroupSession != null) {
                     val info = realm.createObject(OutboundGroupSessionInfoEntity::class.java).apply {
                         creationTime = clock.epochMillis()
+                        // Store the room history visibility on the outbound session creation
+                        shouldShareHistory = entity.shouldShareHistory
                         putOutboundGroupSession(outboundGroupSession)
                     }
                     entity.outboundSessionInfo = info
@@ -834,6 +836,14 @@ internal class RealmCryptoStore @Inject constructor(
         }
     }
 
+    override fun needsRotationDueToVisibilityChange(roomId: String): Boolean {
+        return doWithRealm(realmConfiguration) { realm ->
+            CryptoRoomEntity.getById(realm, roomId)?.let { entity ->
+                entity.shouldShareHistory != entity.outboundSessionInfo?.shouldShareHistory
+            }
+        } ?: false
+    }
+
     /**
      * Note: the result will be only use to export all the keys and not to use the OlmInboundGroupSessionWrapper2,
      * so there is no need to use or update `inboundGroupSessionToRelease` for native memory management.

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/store/db/model/OutboundGroupSessionInfoEntity.kt

@@ -24,7 +24,8 @@ import timber.log.Timber
 
 internal open class OutboundGroupSessionInfoEntity(
         var serializedOutboundSessionData: String? = null,
-        var creationTime: Long? = null
+        var creationTime: Long? = null,
+        var shouldShareHistory: Boolean = false
 ) : RealmObject() {
 
     fun getOutboundGroupSession(): OlmOutboundGroupSession? {