New CryptoMachine on each background operation

MatrixSDK/Background/Crypto/MXBackgroundCryptoV2.swift

@@ -27,29 +27,13 @@ class MXBackgroundCryptoV2: MXBackgroundCrypto {
  case missingCredentials
  }
 
- private let machine: MXCryptoMachine
+ private let credentials: MXCredentials
+ private let restClient: MXRestClient
  private let log = MXNamedLog(name: "MXBackgroundCryptoV2")
 
- init(credentials: MXCredentials, restClient: MXRestClient) throws {
- guard
- let userId = credentials.userId,
- let deviceId = credentials.deviceId
- else {
- throw Error.missingCredentials
- }
-
- // `MXCryptoMachine` will load the same store as the main application meaning that background and foreground
- // sync services have access to the same data / keys. Possible race conditions are handled internally.
- machine = try MXCryptoMachine(
- userId: userId,
- deviceId: deviceId,
- restClient: restClient,
- getRoomAction: { [log] _ in
- log.error("The background crypto should not be accessing rooms")
- return nil
- }
- )
-
+ init(credentials: MXCredentials, restClient: MXRestClient) {
+ self.credentials = credentials
+ self.restClient = restClient
  log.debug("Initialized background crypto module")
  }
 
@@ -66,6 +50,7 @@ class MXBackgroundCryptoV2: MXBackgroundCrypto {
  log.debug(details)
 
  do {
+ let machine = try createMachine()
  _ = try await machine.handleSyncResponse(
  toDevice: syncResponse.toDevice,
  deviceLists: syncResponse.deviceLists,
@@ -100,6 +85,7 @@ class MXBackgroundCryptoV2: MXBackgroundCrypto {
  do {
  // Rust-sdk does not expose api to see if we have a given session key yet (will be added in the future)
  // so for the time being to find out if we can decrypt we simply perform the (more expensive) decryption
+ let machine = try createMachine()
  _ = try machine.decryptRoomEvent(event)
  log.debug("Event `\(eventId)` can be decrypted with session `\(sessionId)`")
  return true
@@ -117,6 +103,7 @@ class MXBackgroundCryptoV2: MXBackgroundCrypto {
  log.debug("Decrypting event `\(eventId)`")
 
  do {
+ let machine = try createMachine()
  let decrypted = try machine.decryptRoomEvent(event)
  let result = try MXEventDecryptionResult(event: decrypted)
  event.setClearData(result)
@@ -127,6 +114,30 @@ class MXBackgroundCryptoV2: MXBackgroundCrypto {
  throw error
  }
  }
+
+ // `MXCryptoMachine` will load the same store as the main application meaning that background and foreground
+ // sync services have access to the same data / keys. The machine is not fully multi-thread and multi-process
+ // safe, and until this is resolved we open a new instance of `MXCryptoMachine` on each background operation
+ // to ensure we are always up-to-date with whatever has been written by the foreground process in the meanwhile.
+ // See https:/matrix-org/matrix-rust-sdk/issues/1415 for more details.
+ private func createMachine() throws -> MXCryptoMachine {
+ guard
+ let userId = credentials.userId,
+ let deviceId = credentials.deviceId
+ else {
+ throw Error.missingCredentials
+ }
+
+ return try MXCryptoMachine(
+ userId: userId,
+ deviceId: deviceId,
+ restClient: restClient,
+ getRoomAction: { [log] _ in
+ log.error("The background crypto should not be accessing rooms")
+ return nil
+ }
+ )
+ }
 }
 
 #endif

MatrixSDK/Background/MXBackgroundSyncService.swift

@@ -40,7 +40,7 @@ public enum MXBackgroundSyncServiceError: Error {
  private let processingQueue: DispatchQueue
  public let credentials: MXCredentials
  private let syncResponseStoreManager: MXSyncResponseStoreManager
- private let crypto: MXBackgroundCrypto?
+ private let crypto: MXBackgroundCrypto
  private var store: MXStore
  private let restClient: MXRestClient
  private var pushRulesManager: MXBackgroundPushRulesManager
@@ -91,12 +91,7 @@ public enum MXBackgroundSyncServiceError: Error {
  crypto = {
  #if DEBUG
  if MXSDKOptions.sharedInstance().isCryptoSDKAvailable && MXSDKOptions.sharedInstance().enableCryptoSDK {
- do {
- return try MXBackgroundCryptoV2(credentials: credentials, restClient: restClient)
- } catch {
- MXLog.failure("Cannot create background crypto", context: error)
- return nil
- }
+ return MXBackgroundCryptoV2(credentials: credentials, restClient: restClient)
  }
  #endif
  return MXLegacyBackgroundCrypto(credentials: credentials, resetBackgroundCryptoStore: resetBackgroundCryptoStore)
@@ -299,7 +294,7 @@ public enum MXBackgroundSyncServiceError: Error {
  }
 
  // should decrypt it first
- if let crypto = crypto, crypto.canDecryptEvent(event) {
+ if crypto.canDecryptEvent(event) {
  // we have keys to decrypt the event
  MXLog.debug("[MXBackgroundSyncService] fetchEvent: Event needs to be decrpyted, and we have the keys to decrypt it.")
 
@@ -406,8 +401,7 @@ public enum MXBackgroundSyncServiceError: Error {
  await self.handleSyncResponse(syncResponse, syncToken: eventStreamToken)
 
  if let event = self.syncResponseStoreManager.event(withEventId: eventId, inRoom: roomId),
- let crypto = self.crypto,
- !crypto.canDecryptEvent(event),
+ !self.crypto.canDecryptEvent(event),
  (syncResponse.toDevice?.events ?? []).count > 0 {
  // we got the event but not the keys to decrypt it. continue to sync
  self.launchBackgroundSync(forEventId: eventId, roomId: roomId, completion: completion)
@@ -446,7 +440,7 @@ public enum MXBackgroundSyncServiceError: Error {
  }
  syncResponseStoreManager.updateStore(with: syncResponse, syncToken: syncToken)
 
- await crypto?.handleSyncResponse(syncResponse)
+ await crypto.handleSyncResponse(syncResponse)
 
  if MXSDKOptions.sharedInstance().autoAcceptRoomInvites,
  let invitedRooms = syncResponse.rooms?.invite {