From 30aa8574633b3be4381e342a60cdd5bc68895730 Mon Sep 17 00:00:00 2001
From: Andy Uhnak <andyuhnak@gmail.com>
Date: Fri, 11 Nov 2022 10:28:04 +0000
Subject: [PATCH] Log decryption errors separately

---
 .../RoomEvent/MXRoomEventDecryption.swift     | 100 +++++++++++++-----
 .../Utils/Logs/MXAnalyticsDestination.swift   |   2 +-
 changelog.d/pr-1632.change                    |   1 +
 3 files changed, 75 insertions(+), 28 deletions(-)
 create mode 100644 changelog.d/pr-1632.change

diff --git a/MatrixSDK/Crypto/Algorithms/RoomEvent/MXRoomEventDecryption.swift b/MatrixSDK/Crypto/Algorithms/RoomEvent/MXRoomEventDecryption.swift
index d8bddbbebc..62adc9ec2e 100644
--- a/MatrixSDK/Crypto/Algorithms/RoomEvent/MXRoomEventDecryption.swift
+++ b/MatrixSDK/Crypto/Algorithms/RoomEvent/MXRoomEventDecryption.swift
@@ -43,6 +43,10 @@ protocol MXRoomEventDecrypting: Actor {
 actor MXRoomEventDecryption: MXRoomEventDecrypting {
     typealias SessionId = String
     typealias EventId = String
+    
+    // `Megolm` error does not currently expose the type of "missing keys" error, so have to match against
+    // hardcoded non-localized error message. Will be changed in future PR
+    private static let MissingKeysMessage = "decryption failed because the room key is missing"
         
     private let handler: MXCryptoRoomEventDecrypting
     private var undecryptedEvents: [SessionId: [EventId: MXEvent]]
@@ -117,34 +121,10 @@ actor MXRoomEventDecryption: MXRoomEventDecrypting {
             log.debug("Successfully decrypted event `\(result.clearEvent["type"] ?? "unknown")`")
             return result
             
-        // `Megolm` error does not currently expose the type of "missing keys" error, so have to match against
-        // hardcoded non-localized error message. Will be changed in future PR
-        } catch DecryptionError.Megolm(message: "decryption failed because the room key is missing") {
-            if undecryptedEvents[sessionId] == nil {
-                log.error("Failed to decrypt one or more events due to missing room keys", context: [
-                    "session_id": sessionId,
-                    "details": "further errors for the same key will be supressed"
-                ])
-            }
-            
-            addUndecryptedEvent(event)
-            
-            let result = MXEventDecryptionResult()
-            result.error = NSError(
-                domain: MXDecryptingErrorDomain,
-                code: Int(MXDecryptingErrorUnknownInboundSessionIdCode.rawValue),
-                userInfo: [
-                    NSLocalizedDescriptionKey: MXDecryptingErrorUnknownInboundSessionIdReason
-                ]
-            )
-            return result
+        } catch let error as DecryptionError {
+            return handleDecryptionError(for: event, sessionId: sessionId, error: error)
         } catch {
-            log.error("Failed to decrypt event", context: error)
-            addUndecryptedEvent(event)
-            
-            let result = MXEventDecryptionResult()
-            result.error = error
-            return result
+            return handleGenericError(for: event, sessionId: sessionId, error: error)
         }
     }
     
@@ -220,6 +200,72 @@ actor MXRoomEventDecryption: MXRoomEventDecrypting {
         }
         return sessionId
     }
+
+    // MARK: - Error handling
+
+    private func handleDecryptionError(for event: MXEvent, sessionId: String, error: DecryptionError) -> MXEventDecryptionResult {
+        switch error {
+        case .Identifier(let message):
+            log.error("Failed to decrypt event due to identifier", context: [
+                "session_id": sessionId,
+                "message": message,
+                "error": error
+            ])
+            return trackedDecryptionResult(for: event, error: error)
+            
+        case .Serialization(let message):
+            log.error("Failed to decrypt event due to serialization", context: [
+                "session_id": sessionId,
+                "message": message,
+                "error": error
+            ])
+            return trackedDecryptionResult(for: event, error: error)
+            
+        case .Megolm(let message):
+            if message == Self.MissingKeysMessage {
+                if undecryptedEvents[sessionId] == nil {
+                    log.error("Failed to decrypt event(s) due to missing room keys", context: [
+                        "session_id": sessionId,
+                        "message": message,
+                        "error": error,
+                        "details": "further errors for the same key will be supressed",
+                    ])
+                }
+                
+                let keysError = NSError(
+                    domain: MXDecryptingErrorDomain,
+                    code: Int(MXDecryptingErrorUnknownInboundSessionIdCode.rawValue),
+                    userInfo: [
+                        NSLocalizedDescriptionKey: MXDecryptingErrorUnknownInboundSessionIdReason
+                    ]
+                )
+                return trackedDecryptionResult(for: event, error: keysError)
+            } else {
+                log.error("Failed to decrypt event due to serialization", context: [
+                    "session_id": sessionId,
+                    "message": message,
+                    "error": error
+                ])
+                return trackedDecryptionResult(for: event, error: error)
+            }
+        }
+    }
+    
+    private func handleGenericError(for event: MXEvent, sessionId: String, error: Error) -> MXEventDecryptionResult {
+        log.error("Failed to decrypt event", context: [
+            "session_id": sessionId,
+            "error": error
+        ])
+        return trackedDecryptionResult(for: event, error: error)
+    }
+    
+    private func trackedDecryptionResult(for event: MXEvent, error: Error) -> MXEventDecryptionResult {
+        addUndecryptedEvent(event)
+        
+        let result = MXEventDecryptionResult()
+        result.error = error
+        return result
+    }
 }
 
 #endif
diff --git a/MatrixSDK/Utils/Logs/MXAnalyticsDestination.swift b/MatrixSDK/Utils/Logs/MXAnalyticsDestination.swift
index b3a82cb2bb..c7b8ef31c8 100644
--- a/MatrixSDK/Utils/Logs/MXAnalyticsDestination.swift
+++ b/MatrixSDK/Utils/Logs/MXAnalyticsDestination.swift
@@ -45,7 +45,7 @@ class MXAnalyticsDestination: BaseDestination {
             return dictionary
         } else if let error = context as? Error {
             return [
-                "error": error.localizedDescription
+                "error": error
             ]
         } else {
             return [
diff --git a/changelog.d/pr-1632.change b/changelog.d/pr-1632.change
new file mode 100644
index 0000000000..cc6c64abd2
--- /dev/null
+++ b/changelog.d/pr-1632.change
@@ -0,0 +1 @@
+CryptoV2: Log decryption errors separately