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271
MatrixSDK/Crypto/Algorithms/RoomEvent/MXRoomEventDecryption.swift
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| // | ||
| // Copyright 2022 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. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
| // | ||
|
|
||
| import Foundation | ||
|
|
||
| #if DEBUG | ||
| import MatrixSDKCrypto | ||
|
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| /// Object responsible for decrypting room events and dealing with undecryptable events | ||
| protocol MXRoomEventDecrypting: Actor { | ||
|
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| /// Decrypt a list of events | ||
| func decrypt(events: [MXEvent]) -> [MXEventDecryptionResult] | ||
|
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| /// Process an event that may contain room key and retry decryption if it does | ||
| /// | ||
| /// Note: room key could be contained in `m.room_key` or `m.forwarded_room_key` | ||
| func handlePossibleRoomKeyEvent(_ event: MXEvent) | ||
|
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| /// Retry decrypting events with specific session ids | ||
| /// | ||
| /// Note: this may be useful if we have just imported keys from backup / file | ||
| func retryUndecryptedEvents(sessionIds: [String]) | ||
|
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| /// Reset the store of undecrypted events | ||
| func resetUndecryptedEvents() | ||
| } | ||
|
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| /// Implementation of `MXRoomEventDecrypting` as an Actor | ||
| actor MXRoomEventDecryption: MXRoomEventDecrypting { | ||
| typealias SessionId = String | ||
| typealias EventId = String | ||
|
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| // `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" | ||
|
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| private let handler: MXCryptoRoomEventDecrypting | ||
| private var undecryptedEvents: [SessionId: [EventId: MXEvent]] | ||
| private let log = MXNamedLog(name: "MXRoomEventDecryption") | ||
|
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| init(handler: MXCryptoRoomEventDecrypting) { | ||
| self.handler = handler | ||
| self.undecryptedEvents = [:] | ||
| } | ||
|
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| func decrypt(events: [MXEvent]) -> [MXEventDecryptionResult] { | ||
| let results = events.map(decrypt(event:)) | ||
|
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| let undecrypted = results.filter { | ||
| $0.clearEvent == nil || $0.error != nil | ||
| } | ||
|
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| if !undecrypted.isEmpty { | ||
| log.error("Unable to decrypt some event(s)", context: [ | ||
| "total": events.count, | ||
| "undecrypted": undecrypted.count | ||
| ]) | ||
| } else { | ||
| log.debug("Decrypted all \(events.count) event(s)") | ||
| } | ||
|
|
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| return results | ||
| } | ||
|
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| func handlePossibleRoomKeyEvent(_ event: MXEvent) { | ||
| guard let sessionId = roomKeySessionId(for: event) else { | ||
| return | ||
| } | ||
|
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| log.debug("Recieved a new room key as `\(event.type ?? "")` for session \(sessionId)") | ||
| let events = undecryptedEvents[sessionId]?.map(\.value) ?? [] | ||
| retryDecryption(events: events) | ||
| } | ||
|
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| func retryUndecryptedEvents(sessionIds: [String]) { | ||
| let events = sessionIds | ||
| .flatMap { | ||
| undecryptedEvents[$0]?.map { | ||
| $0.value | ||
| } ?? [] | ||
| } | ||
| retryDecryption(events: events) | ||
| } | ||
|
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| func resetUndecryptedEvents() { | ||
| undecryptedEvents = [:] | ||
| } | ||
|
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| // MARK: - Private | ||
|
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| private func decrypt(event: MXEvent) -> MXEventDecryptionResult { | ||
| guard | ||
| event.isEncrypted && event.clear == nil, | ||
| event.content?["algorithm"] as? String == kMXCryptoMegolmAlgorithm, | ||
| let sessionId = sessionId(for: event) | ||
| else { | ||
| log.debug("Ignoring unencrypted or non-room event") | ||
|
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| let result = MXEventDecryptionResult() | ||
| result.clearEvent = event.clear?.jsonDictionary() | ||
| return result | ||
| } | ||
|
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| do { | ||
| let decryptedEvent = try handler.decryptRoomEvent(event) | ||
| let result = try MXEventDecryptionResult(event: decryptedEvent) | ||
| log.debug("Successfully decrypted event `\(result.clearEvent["type"] ?? "unknown")`") | ||
| return result | ||
|
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| } catch let error as DecryptionError { | ||
| return handleDecryptionError(for: event, sessionId: sessionId, error: error) | ||
| } catch { | ||
| return handleGenericError(for: event, sessionId: sessionId, error: error) | ||
| } | ||
| } | ||
|
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| private func addUndecryptedEvent(_ event: MXEvent) { | ||
| guard let sessionId = sessionId(for: event) else { | ||
| return | ||
| } | ||
|
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| var events = undecryptedEvents[sessionId] ?? [:] | ||
| events[event.eventId] = event | ||
| undecryptedEvents[sessionId] = events | ||
| } | ||
|
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| private func removeUndecryptedEvent(_ event: MXEvent) { | ||
| guard let sessionId = sessionId(for: event) else { | ||
| return | ||
| } | ||
| undecryptedEvents[sessionId]?[event.eventId] = nil | ||
| } | ||
|
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| private func retryDecryption(events: [MXEvent]) { | ||
| guard !events.isEmpty else { | ||
| return | ||
| } | ||
|
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| log.debug("Re-decrypting \(events.count) event(s)") | ||
|
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| var results = [(MXEvent, MXEventDecryptionResult)]() | ||
| for event in events { | ||
| guard event.clear == nil else { | ||
| removeUndecryptedEvent(event) | ||
| continue | ||
| } | ||
|
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| let result = decrypt(event: event) | ||
| guard result.clearEvent != nil else { | ||
| log.error("Event still not decryptable", context: [ | ||
| "event_id": event.eventId ?? "unknown", | ||
| "session_id": sessionId(for: event), | ||
| "error": result.error.localizedDescription | ||
| ]) | ||
| continue | ||
| } | ||
|
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| removeUndecryptedEvent(event) | ||
| results.append((event, result)) | ||
| } | ||
|
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| Task { [results] in | ||
| await MainActor.run { | ||
| for (event, result) in results { | ||
| event.setClearData(result) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| private func roomKeySessionId(for event: MXEvent) -> String? { | ||
| if event.eventType == .roomKey, let content = MXRoomKeyEventContent(fromJSON: event.content) { | ||
| return content.sessionId | ||
| } else if event.eventType == .roomForwardedKey, let content = MXForwardedRoomKeyEventContent(fromJSON: event.content) { | ||
| return content.sessionId | ||
| } else { | ||
| return nil | ||
| } | ||
| } | ||
|
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| private func sessionId(for event: MXEvent) -> String? { | ||
| let sessionId = event.content["session_id"] ?? event.wireContent["session_id"] | ||
| guard let sessionId = sessionId as? String else { | ||
| log.failure("Event is missing session id") | ||
| return nil | ||
| } | ||
| return sessionId | ||
| } | ||
|
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| // MARK: - Error handling | ||
|
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| 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) | ||
|
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| 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) | ||
|
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| 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", | ||
| ]) | ||
| } | ||
|
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| 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 megolm error", context: [ | ||
| "session_id": sessionId, | ||
| "message": message, | ||
| "error": error | ||
| ]) | ||
| return trackedDecryptionResult(for: event, error: error) | ||
| } | ||
| } | ||
| } | ||
|
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| 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) | ||
| } | ||
|
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| private func trackedDecryptionResult(for event: MXEvent, error: Error) -> MXEventDecryptionResult { | ||
| addUndecryptedEvent(event) | ||
|
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| let result = MXEventDecryptionResult() | ||
| result.error = error | ||
| return result | ||
| } | ||
| } | ||
|
|
||
| #endif |
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