Secrets: On startup, request again private keys we are missing locally

This will mitigate unexpected state of cross-signing and backup.

CHANGES.rst

@@ -4,6 +4,7 @@ Changes in 0.11.3 (2020-05-xx)
 Improvements:
  * Cross-signing: Display "Verify your other sessions" modal at every startup if needed (#3180).
  * Cross-signing: The "Complete Security" button now triggers a verification request to all user devices.
+ * Secrets: On startup, request again private keys we are missing locally.
 
 Bug fix:
  * KeyVerificationSelfVerifyStartViewController has no navigation (#3195).

Riot/AppDelegate.m

@@ -2769,6 +2769,8 @@ NSString *const AppDelegateUniversalLinkDidChangeNotification = @"AppDelegateUni
             
             // Register to new key verification request
             [self registerNewRequestNotificationForSession:mxSession];
+            
+            [self checkLocalPrivateKeysInSession:mxSession];
         }
         else if (mxSession.state == MXSessionStateClosed)
         {
@@ -3523,6 +3525,32 @@ NSString *const AppDelegateUniversalLinkDidChangeNotification = @"AppDelegateUni
     [eventsToNotify removeObjectForKey:@(mxSession.hash)];
 }
 
+- (void)checkLocalPrivateKeysInSession:(MXSession*)mxSession
+{
+    id<MXCryptoStore> cryptoStore = mxSession.crypto.store;
+    NSUInteger keysCount = 0;
+    if ([cryptoStore secretWithSecretId:MXSecretId.keyBackup])
+    {
+        keysCount++;
+    }
+    if ([cryptoStore secretWithSecretId:MXSecretId.crossSigningUserSigning])
+    {
+        keysCount++;
+    }
+    if ([cryptoStore secretWithSecretId:MXSecretId.crossSigningSelfSigning])
+    {
+        keysCount++;
+    }
+    
+    if (keysCount > 0 && keysCount < 3)
+    {
+        // We should have 3 of them. If not, request them again as mitigation
+        NSLog(@"[AppDelegate] checkLocalPrivateKeysInSession: request keys because keysCount = %@", @(keysCount));
+        [mxSession.crypto requestAllPrivateKeys];
+    }
+}
+
+
 #pragma mark -
 
 /**