MXCrypto: Move decryptions out of the main thread

CHANGES.rst

@@ -7,12 +7,20 @@ Changes to be released in next version
 🙌 Improvements
  * MXSession: Cache initial sync response until it is fully handled (vector-im/element-ios/issues/4317).
  * MXStore: New commit method accepting a completion block.
+ * MXCrypto: Decrypt events asynchronously and no more on the main thread )(vector-im/element-ios/issues/4306).
+ * MXSession: Add the decryptEvents method to decypt a bunch of events asynchronously.
+ * MXSession: Make the eventWithEventId method decrypt the event if needed.
+ * MXEventTimeline: Add NSCopying implementation so that another pagination can be done on the same set of data.
+ * MXCrypto: eventDeviceInfo: Do not synchronise anymore the operation with the decryption queue.
 
 🐛 Bugfix
- * 
+ * MXRoomSummary: Fix decryption of the last message when it is edited (vector-im/element-ios/issues/4322).
 
 ⚠️ API Changes
- * 
+ * MXRoom: MXRoom.outgoingMessages does not decrypt messages anymore. Use MXSession.decryptEvents to get decrypted events.
+ * MXSession: [MXSession decryptEvent:inTimeline:] is deprecated, use [MXSession decryptEvents:inTimeline:onComplete:] instead.
+ * MXCrypto: [MXCrypto decryptEvent:inTimeline:] is deprecated, use [MXCrypto decryptEvents:inTimeline:onComplete:] instead.
+ * MXCrypto: [MXCrypto hasKeysToDecryptEvent:] is now asynchronous.
 
 🗣 Translations
  * 

MatrixSDK/Aggregations/MXAggregatedEditsUpdater.m

@@ -70,17 +70,6 @@ - (MXHTTPOperation*)replaceTextMessageEvent:(MXEvent*)event
         failure(nil);
         return nil;
     }
-
-    // If it is not already done, decrypt the event to build the new content
-    if (event.isEncrypted && !event.clearEvent)
-    {
-        if (![self.mxSession decryptEvent:event inTimeline:nil])
-        {
-            NSLog(@"[MXAggregations] replaceTextMessageEvent: Fail to decrypt original event: %@", event.eventId);
-            failure(nil);
-            return nil;
-        }
-    }
 
     NSString *messageType = event.content[@"msgtype"];
 
@@ -243,13 +232,6 @@ - (void)handleReplace:(MXEvent *)replaceEvent
             if (editedEvent)
             {
                 [self.matrixStore replaceEvent:editedEvent inRoom:roomId];
-
-                if (editedEvent.isEncrypted && !editedEvent.clearEvent)
-                {
-                    [self.mxSession decryptEvent:editedEvent inTimeline:nil];
-                }
-
-
                 [self notifyEventEditsListenersOfRoom:roomId replaceEvent:replaceEvent];
             }
         }

MatrixSDK/Aggregations/MXAggregatedReferencesUpdater.m

@@ -58,11 +58,6 @@ - (void)handleReference:(MXEvent *)referenceEvent
         {
             [self.matrixStore replaceEvent:newEvent inRoom:roomId];
 
-            if (newEvent.isEncrypted && !newEvent.clearEvent)
-            {
-                [self.mxSession decryptEvent:newEvent inTimeline:nil];
-            }
-
             // TODO or not?
             //[self notifyEventEditsListenersOfRoom:roomId replaceEvent:replaceEvent];
         }

MatrixSDK/Aggregations/MXAggregations.m

@@ -158,15 +158,25 @@ - (MXHTTPOperation*)referenceEventsForEvent:(NSString*)eventId
             }
         }
 
+        NSMutableArray *eventsToDecrypt = [NSMutableArray array];
         for (MXEvent *event in allEvents)
         {
             if (event.isEncrypted && !event.clearEvent)
             {
-                [self.mxSession decryptEvent:event inTimeline:nil];
+                [eventsToDecrypt addObject:event];
             }
         }
 
-        success(paginatedResponse);
+        if (eventsToDecrypt.count)
+        {
+            [self.mxSession decryptEvents:eventsToDecrypt inTimeline:nil onComplete:^(NSArray<MXEvent *> *failedEvents) {
+                success(paginatedResponse);
+            }];
+        }
+        else
+        {
+            success(paginatedResponse);
+        }
     };
 
     MXEvent *event = [self.mxSession.store eventWithEventId:eventId inRoom:roomId];

MatrixSDK/Crypto/Algorithms/MXDecrypting.h

@@ -47,17 +47,13 @@
 /**
  Decrypt a message.
 
- In case of success, the event is updated with clear data.
- In case of failure, event.decryptionError contains the error.
-
  @param event the raw event.
  @param timeline the id of the timeline where the event is decrypted. It is used
-                 to prevent replay attack.
- @param error the result error if there is a problem decrypting the event.
+                 to prevent replay attack. Can be nil.
 
- @return The decryption result. Nil if it failed.
+ @return The decryption result.
  */
-- (MXEventDecryptionResult *)decryptEvent:(MXEvent*)event inTimeline:(NSString*)timeline error:(NSError** )error;
+- (MXEventDecryptionResult *)decryptEvent:(MXEvent*)event inTimeline:(NSString*)timeline;
 
 /**
  * Handle a key event.

MatrixSDK/Crypto/Algorithms/MXEventDecryptionResult.h

@@ -1,5 +1,6 @@
 /*
  Copyright 2017 Vector Creations Ltd
+ Copyright 2021 The Matrix.org Foundation C.I.C
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -44,4 +45,9 @@
  */
 @property NSArray<NSString *> *forwardingCurve25519KeyChain;
 
+/**
+ If any, the error that occured during decryption.
+ */
+@property (nonatomic) NSError *error;
+
 @end

MatrixSDK/Crypto/Algorithms/Megolm/MXMegolmDecryption.m

@@ -68,8 +68,8 @@ - (BOOL)hasKeysToDecryptEvent:(MXEvent *)event
 
     NSString *senderKey, *sessionId;
 
-    MXJSONModelSetString(senderKey, event.content[@"sender_key"]);
-    MXJSONModelSetString(sessionId, event.content[@"session_id"]);
+    MXJSONModelSetString(senderKey, event.wireContent[@"sender_key"]);
+    MXJSONModelSetString(sessionId, event.wireContent[@"session_id"]);
     if (senderKey && sessionId)
     {
         hasKeys = ([crypto.store inboundGroupSessionWithId:sessionId andSenderKey:senderKey] != nil);
@@ -78,35 +78,32 @@ - (BOOL)hasKeysToDecryptEvent:(MXEvent *)event
     return hasKeys;
 }
 
-- (MXEventDecryptionResult *)decryptEvent:(MXEvent*)event inTimeline:(NSString*)timeline error:(NSError** )error;
+- (MXEventDecryptionResult *)decryptEvent:(MXEvent*)event inTimeline:(NSString*)timeline
 {
     MXEventDecryptionResult *result;
     NSString *senderKey, *ciphertext, *sessionId;
 
-    MXJSONModelSetString(senderKey, event.content[@"sender_key"]);
-    MXJSONModelSetString(ciphertext, event.content[@"ciphertext"]);
-    MXJSONModelSetString(sessionId, event.content[@"session_id"]);
+    MXJSONModelSetString(senderKey, event.wireContent[@"sender_key"]);
+    MXJSONModelSetString(ciphertext, event.wireContent[@"ciphertext"]);
+    MXJSONModelSetString(sessionId, event.wireContent[@"session_id"]);
 
     if (!senderKey || !sessionId || !ciphertext)
     {
-        if (error)
-        {
-            *error = [NSError errorWithDomain:MXDecryptingErrorDomain
+        result = [MXEventDecryptionResult new];
+        result.error = [NSError errorWithDomain:MXDecryptingErrorDomain
                                          code:MXDecryptingErrorMissingFieldsCode
                                      userInfo:@{
                                                 NSLocalizedDescriptionKey: MXDecryptingErrorMissingFieldsReason
                                                 }];
-        }
-        return nil;
+        return result;
     }
 
     NSError *olmError;
     MXDecryptionResult *olmResult = [olmDevice decryptGroupMessage:ciphertext roomId:event.roomId inTimeline:timeline sessionId:sessionId senderKey:senderKey error:&olmError];
 
+    result = [MXEventDecryptionResult new];
     if (olmResult)
     {
-        result = [[MXEventDecryptionResult alloc] init];
-
         result.clearEvent = olmResult.payload;
         result.senderCurve25519Key = olmResult.senderKey;
         result.claimedEd25519Key = olmResult.keysClaimed[@"ed25519"];
@@ -141,10 +138,7 @@ - (MXEventDecryptionResult *)decryptEvent:(MXEvent*)event inTimeline:(NSString*)
             });
         }
 
-        if (error)
-        {
-            *error = olmError;
-        }
+        result.error = olmError;
     }
 
     return result;
@@ -400,29 +394,25 @@ - (void)retryDecryption:(NSString*)senderKey sessionId:(NSString*)sessionId comp
                 else
                 {
                     // Decrypt on the current thread (Must be MXCrypto.cryptoQueue)
-                    NSError *error;
-                    MXEventDecryptionResult *result = [self decryptEvent:event inTimeline:(timelineId.length ? timelineId : nil) error:&error];
+                    MXEventDecryptionResult *result = [self decryptEvent:event inTimeline:(timelineId.length ? timelineId : nil)];
 
                     // And set the result on the main thread to be compatible with other modules
                     dispatch_group_enter(group);
                     dispatch_async(dispatch_get_main_queue(), ^{
-                        if (result)
+                        if (result.error)
                         {
-                            if (event.clearEvent)
-                            {
-                                // This can happen when the event is in several timelines
-                                NSLog(@"[MXMegolmDecryption] retryDecryption: %@ already decrypted on main thread", event.eventId);
-                            }
-                            else
-                            {
-                                [event setClearData:result];
-                            }
+                            NSLog(@"[MXMegolmDecryption] retryDecryption: Still can't decrypt %@. Error: %@", event.eventId, result.error);
+                            allDecrypted = NO;
                         }
-                        else if (error)
+
+                        if (event.clearEvent)
                         {
-                            NSLog(@"[MXMegolmDecryption] retryDecryption: Still can't decrypt %@. Error: %@", event.eventId, event.decryptionError);
-                            event.decryptionError = error;
-                            allDecrypted = NO;
+                            // This can happen when the event is in several timelines
+                            NSLog(@"[MXMegolmDecryption] retryDecryption: %@ already decrypted on main thread", event.eventId);
+                        }
+                        else
+                        {
+                            [event setClearData:result];
                         }
 
                         dispatch_group_leave(group);