From 6f2f70dcdc5b753c1101b8f0e24550babc6db775 Mon Sep 17 00:00:00 2001
From: manuroe <manu@matrix.org>
Date: Thu, 8 Oct 2020 09:24:40 +0200
Subject: [PATCH] MXCrypto: Reset OTKs in case some IDs are already used.

This is a mitigation for https://github.com/vector-im/element-ios/issues/3721. But it does not fix the root issue.
---
 CHANGES.rst                 |  2 +-
 MatrixSDK/Crypto/MXCrypto.m | 23 +++++++++++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 93f99d0fb4..6b1035e145 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -8,7 +8,7 @@ Changes to be released in next version
  * MXCrypto: Add hasKeysToDecryptEvent method.
 
 🐛 Bugfix
- * 
+ * MXCrypto: Reset OTKs in case some IDs are already used (https://github.com/vector-im/element-ios/issues/3721).
 
 ⚠️ API Changes
  * 
diff --git a/MatrixSDK/Crypto/MXCrypto.m b/MatrixSDK/Crypto/MXCrypto.m
index d2a9ffc865..91ec3e3c55 100644
--- a/MatrixSDK/Crypto/MXCrypto.m
+++ b/MatrixSDK/Crypto/MXCrypto.m
@@ -2641,7 +2641,7 @@ - (void)maybeUploadOneTimeKeys:(void (^)(void))success failure:(void (^)(NSError
         NSLog(@"[MXCrypto] maybeUploadOneTimeKeys: there are %tu one-time keys on the homeserver", oneTimeKeyCount);
         
         MXWeakify(self);
-        uploadOneTimeKeysOperation = [self generateAndUploadOneTimeKeys:oneTimeKeyCount success:^{
+        uploadOneTimeKeysOperation = [self generateAndUploadOneTimeKeys:oneTimeKeyCount retry:YES success:^{
             MXStrongifyAndReturnIfNil(self);
             
             self->uploadOneTimeKeysOperation = nil;
@@ -2695,7 +2695,7 @@ - (void)maybeUploadOneTimeKeys:(void (^)(void))success failure:(void (^)(NSError
             NSLog(@"[MXCrypto] maybeUploadOneTimeKeys: %@ one-time keys on the homeserver", @(keyCount));
 
             MXWeakify(self);
-            MXHTTPOperation *operation2 = [self generateAndUploadOneTimeKeys:keyCount success:^{
+            MXHTTPOperation *operation2 = [self generateAndUploadOneTimeKeys:keyCount retry:YES success:^{
                 MXStrongifyAndReturnIfNil(self);
                 
                 self->uploadOneTimeKeysOperation = nil;
@@ -2743,7 +2743,7 @@ - (void)maybeUploadOneTimeKeys:(void (^)(void))success failure:(void (^)(NSError
     }
 }
 
-- (MXHTTPOperation *)generateAndUploadOneTimeKeys:(NSUInteger)keyCount success:(void (^)(void))success failure:(void (^)(NSError *))failure
+- (MXHTTPOperation *)generateAndUploadOneTimeKeys:(NSUInteger)keyCount retry:(BOOL)retry success:(void (^)(void))success failure:(void (^)(NSError *))failure
 {
     MXHTTPOperation *operation;
     
@@ -2753,7 +2753,22 @@ - (MXHTTPOperation *)generateAndUploadOneTimeKeys:(NSUInteger)keyCount success:(
             success();
         } failure:^(NSError *error) {
             NSLog(@"[MXCrypto] generateAndUploadOneTimeKeys: Failed to publish one-time keys. Error: %@", error);
-            failure(error);
+            
+            if ([MXError isMXError:error] && retry)
+            {
+                // The homeserver explicitly rejected the request.
+                // Reset local OTKs we tried to push and retry
+                // There is no matrix specific error but we really want to detect the error described at
+                // https://github.com/vector-im/element-ios/issues/3721
+                NSLog(@"[MXCrypto] uploadOneTimeKeys: Reset local OTKs because the server does not like them");
+                [self.olmDevice markOneTimeKeysAsPublished];
+                
+                [self generateAndUploadOneTimeKeys:keyCount retry:NO success:success failure:failure];
+            }
+            else
+            {
+                failure(error);
+            }
         }];
     }