Implement group chat message signing

Signal/Signal-Info.plist

@@ -127,7 +127,7 @@
 	<key>NSContactsUsageDescription</key>
 	<string>Signal uses your contacts to find users you know. We do not store your contacts on the server.</string>
 	<key>NSFaceIDUsageDescription</key>
-	<string>Loki Messenger&apos;s Screen Lock feature uses Face ID.</string>
+	<string>Loki Messenger's Screen Lock feature uses Face ID.</string>
 	<key>NSMicrophoneUsageDescription</key>
 	<string>Signal needs access to your microphone to make and receive phone calls and record voice messages.</string>
 	<key>NSPhotoLibraryAddUsageDescription</key>

SignalServiceKit/src/Loki/API/Group Chat/LokiGroupChatAPI.swift

@@ -75,7 +75,8 @@ public final class LokiGroupChatAPI : LokiDotNetAPI {
                 let isDeleted = (message["is_deleted"] as? Int == 1)
                 guard !isDeleted else { return nil }
                 guard let annotations = message["annotations"] as? [JSON], let annotation = annotations.first, let value = annotation["value"] as? JSON,
-                    let serverID = message["id"] as? UInt64, let body = message["text"] as? String, let hexEncodedPublicKey = value["source"] as? String, let displayName = value["from"] as? String,
+                    let serverID = message["id"] as? UInt64, let hexEncodedSignatureData = value["sig"] as? String, let signatureVersion = value["sigver"] as? Int,
+                    let body = message["text"] as? String, let hexEncodedPublicKey = value["source"] as? String, let displayName = value["from"] as? String,
                     let timestamp = value["timestamp"] as? UInt64 else {
                         print("[Loki] Couldn't parse message for group chat with ID: \(group) on server: \(server) from: \(message).")
                         return nil
@@ -84,20 +85,28 @@ public final class LokiGroupChatAPI : LokiDotNetAPI {
                 if serverID > (lastMessageServerID ?? 0) { setLastMessageServerID(for: group, on: server, to: serverID) }
                 let quote: LokiGroupMessage.Quote?
                 if let quoteAsJSON = value["quote"] as? JSON, let quotedMessageTimestamp = quoteAsJSON["id"] as? UInt64, let quoteeHexEncodedPublicKey = quoteAsJSON["author"] as? String, let quotedMessageBody = quoteAsJSON["text"] as? String {
-                    quote = LokiGroupMessage.Quote(quotedMessageTimestamp: quotedMessageTimestamp, quoteeHexEncodedPublicKey: quoteeHexEncodedPublicKey, quotedMessageBody: quotedMessageBody)
+                    let quotedMessageServerID = message["reply_to"] as? UInt64
+                    quote = LokiGroupMessage.Quote(quotedMessageTimestamp: quotedMessageTimestamp, quoteeHexEncodedPublicKey: quoteeHexEncodedPublicKey, quotedMessageBody: quotedMessageBody, quotedMessageServerID: quotedMessageServerID)
                 } else {
                     quote = nil
                 }
-                return LokiGroupMessage(serverID: serverID, hexEncodedPublicKey: hexEncodedPublicKey, displayName: displayName, body: body, type: publicChatMessageType, timestamp: timestamp, quote: quote)
+                let signature = LokiGroupMessage.Signature(hexEncodedData: hexEncodedSignatureData, version: UInt64(signatureVersion))
+                let result = LokiGroupMessage(serverID: serverID, hexEncodedPublicKey: hexEncodedPublicKey, displayName: displayName, body: body, type: publicChatMessageType, timestamp: timestamp, quote: quote, signature: signature)
+                guard result.hasValidSignature() else {
+                    print("[Loki] Ignoring group chat message with invalid signature.")
+                    return nil
+                }
+                return result
             }.sorted { $0.timestamp < $1.timestamp }
         }
     }
     
     public static func sendMessage(_ message: LokiGroupMessage, to group: UInt64, on server: String) -> Promise<LokiGroupMessage> {
+        guard let signedMessage = message.sign(with: userKeyPair.privateKey) else { return Promise(error: Error.signingFailed) }
         return getAuthToken(for: server).then { token -> Promise<LokiGroupMessage> in
             print("[Loki] Sending message to group chat with ID: \(group) on server: \(server).")
             let url = URL(string: "\(server)/channels/\(group)/messages")!
-            let parameters = message.toJSON()
+            let parameters = signedMessage.toJSON()
             let request = TSRequest(url: url, method: "POST", parameters: parameters)
             request.allHTTPHeaderFields = [ "Content-Type" : "application/json", "Authorization" : "Bearer \(token)" ]
             let displayName = userDisplayName
@@ -111,7 +120,7 @@ public final class LokiGroupChatAPI : LokiDotNetAPI {
                     throw Error.parsingFailed
                 }
                 let timestamp = UInt64(date.timeIntervalSince1970) * 1000
-                return LokiGroupMessage(serverID: serverID, hexEncodedPublicKey: userHexEncodedPublicKey, displayName: displayName, body: body, type: publicChatMessageType, timestamp: timestamp, quote: message.quote)
+                return LokiGroupMessage(serverID: serverID, hexEncodedPublicKey: userHexEncodedPublicKey, displayName: displayName, body: body, type: publicChatMessageType, timestamp: timestamp, quote: signedMessage.quote, signature: signedMessage.signature)
             }
         }.recover { error -> Promise<LokiGroupMessage> in
             if let error = error as? NetworkManagerError, error.statusCode == 401 {

SignalServiceKit/src/Loki/API/Group Chat/LokiGroupMessage.swift

@@ -10,17 +10,29 @@ public final class LokiGroupMessage : NSObject {
     public let timestamp: UInt64
     public let type: String
     public let quote: Quote?
+    public let signature: Signature?
     
     @objc(serverID)
     public var objc_serverID: UInt64 { return serverID ?? 0 }
     
+    // MARK: Settings
+    private let signatureVersion: UInt64 = 1
+    
+    // MARK: Types
     public struct Quote {
         public let quotedMessageTimestamp: UInt64
         public let quoteeHexEncodedPublicKey: String
         public let quotedMessageBody: String
+        public let quotedMessageServerID: UInt64?
+    }
+    
+    public struct Signature {
+        public let hexEncodedData: String
+        public let version: UInt64
     }
     
-    public init(serverID: UInt64?, hexEncodedPublicKey: String, displayName: String, body: String, type: String, timestamp: UInt64, quote: Quote?) {
+    // MARK: Initialization
+    public init(serverID: UInt64?, hexEncodedPublicKey: String, displayName: String, body: String, type: String, timestamp: UInt64, quote: Quote?, signature: Signature?) {
         self.serverID = serverID
         self.hexEncodedPublicKey = hexEncodedPublicKey
         self.displayName = displayName
@@ -28,24 +40,74 @@ public final class LokiGroupMessage : NSObject {
         self.type = type
         self.timestamp = timestamp
         self.quote = quote
+        self.signature = signature
         super.init()
     }
     
-    @objc public convenience init(hexEncodedPublicKey: String, displayName: String, body: String, type: String, timestamp: UInt64, quotedMessageTimestamp: UInt64, quoteeHexEncodedPublicKey: String?, quotedMessageBody: String?) {
+    @objc public convenience init(hexEncodedPublicKey: String, displayName: String, body: String, type: String, timestamp: UInt64, quotedMessageTimestamp: UInt64, quoteeHexEncodedPublicKey: String?, quotedMessageBody: String?, quotedMessageServerID: UInt64, hexEncodedSignatureData: String?, signatureVersion: UInt64) {
         let quote: Quote?
         if quotedMessageTimestamp != 0, let quoteeHexEncodedPublicKey = quoteeHexEncodedPublicKey, let quotedMessageBody = quotedMessageBody {
-            quote = Quote(quotedMessageTimestamp: quotedMessageTimestamp, quoteeHexEncodedPublicKey: quoteeHexEncodedPublicKey, quotedMessageBody: quotedMessageBody)
+            let quotedMessageServerID = (quotedMessageServerID != 0) ? quotedMessageServerID : nil
+            quote = Quote(quotedMessageTimestamp: quotedMessageTimestamp, quoteeHexEncodedPublicKey: quoteeHexEncodedPublicKey, quotedMessageBody: quotedMessageBody, quotedMessageServerID: quotedMessageServerID)
         } else {
             quote = nil
         }
-        self.init(serverID: nil, hexEncodedPublicKey: hexEncodedPublicKey, displayName: displayName, body: body, type: type, timestamp: timestamp, quote: quote)
+        let signature: Signature?
+        if let hexEncodedData = hexEncodedSignatureData, signatureVersion != 0 {
+            signature = Signature(hexEncodedData: hexEncodedData, version: signatureVersion)
+        } else {
+            signature = nil
+        }
+        self.init(serverID: nil, hexEncodedPublicKey: hexEncodedPublicKey, displayName: displayName, body: body, type: type, timestamp: timestamp, quote: quote, signature: signature)
+    }
+    
+    // MARK: Crypto
+    internal func sign(with privateKey: Data) -> LokiGroupMessage? {
+        guard let data = getValidationData() else {
+            print("[Loki] Failed to sign group chat message.")
+            return nil
+        }
+        let userKeyPair = OWSIdentityManager.shared().identityKeyPair()!
+        guard let signatureData = try? Ed25519.sign(data, with: userKeyPair) else {
+            print("[Loki] Failed to sign group chat message.")
+            return nil
+        }
+        let hexEncodedSignatureData = signatureData.toHexString()
+        let signature = Signature(hexEncodedData: hexEncodedSignatureData, version: signatureVersion)
+        return LokiGroupMessage(serverID: serverID, hexEncodedPublicKey: hexEncodedPublicKey, displayName: displayName, body: body, type: type, timestamp: timestamp, quote: quote, signature: signature)
     }
     
+    internal func hasValidSignature() -> Bool {
+        guard let signature = signature else { return false }
+        guard let data = getValidationData() else { return false }
+        return (try? Ed25519.verifySignature(Data(hex: signature.hexEncodedData), publicKey: Data(hex: hexEncodedPublicKey), data: data)) ?? false
+    }
+    
+    // MARK: JSON
     internal func toJSON() -> JSON {
-        var value: JSON = [ "timestamp" : timestamp, "from" : displayName, "source" : hexEncodedPublicKey ]
+        var value: JSON = [ "timestamp" : timestamp ]
         if let quote = quote {
             value["quote"] = [ "id" : quote.quotedMessageTimestamp, "author" : quote.quoteeHexEncodedPublicKey, "text" : quote.quotedMessageBody ]
         }
-        return [ "text" : body, "annotations": [ [ "type" : type, "value" : value ] ] ]
+        if let signature = signature {
+            value["sig"] = signature.hexEncodedData
+            value["sigver"] = signature.version
+        }
+        let annotation: JSON = [ "type" : type, "value" : value ]
+        var result: JSON = [ "text" : body, "annotations": [ annotation ] ]
+        if let quotedMessageServerID = quote?.quotedMessageServerID {
+            result["reply_to"] = quotedMessageServerID
+        }
+        return result
+    }
+    
+    // MARK: Convenience
+    private func getValidationData() -> Data? {
+        var string = "\(body.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines))\(timestamp)"
+        if let quote = quote {
+            string += "\(quote.quotedMessageTimestamp)\(quote.quoteeHexEncodedPublicKey)\(quote.quotedMessageBody.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines))"
+        }
+        string += "\(signatureVersion)"
+        return string.data(using: String.Encoding.utf8)
     }
 }

SignalServiceKit/src/Loki/API/LokiDotNetAPI.swift

@@ -3,13 +3,13 @@ import PromiseKit
 public class LokiDotNetAPI : NSObject {
 
     // MARK: Convenience
-    private static let userKeyPair = OWSIdentityManager.shared().identityKeyPair()!
     internal static let storage = OWSPrimaryStorage.shared()
+    internal static let userKeyPair = OWSIdentityManager.shared().identityKeyPair()!
     internal static let userHexEncodedPublicKey = userKeyPair.hexEncodedPublicKey
 
     // MARK: Error
     public enum Error : Swift.Error {
-        case parsingFailed, decryptionFailed
+        case parsingFailed, decryptionFailed, signingFailed
     }
 
     // MARK: Database
@@ -58,7 +58,7 @@ public class LokiDotNetAPI : NSObject {
             }
             // Discard the "05" prefix if needed
             if (serverPublicKey.count == 33) {
-                let hexEncodedServerPublicKey = serverPublicKey.hexadecimalString
+                let hexEncodedServerPublicKey = serverPublicKey.toHexString()
                 serverPublicKey = Data.data(fromHex: hexEncodedServerPublicKey.substring(from: 2))!
             }
             // The challenge is prefixed by the 16 bit IV

SignalServiceKit/src/Loki/Database/LokiDatabaseUtilities.swift

@@ -0,0 +1,22 @@
+
+@objc(LKDatabaseUtilities)
+public final class LokiDatabaseUtilities : NSObject {
+    
+    private override init() { }
+    
+    @objc(getServerIDForQuoteWithID:quoteeHexEncodedPublicKey:threadID:transaction:)
+    public static func getServerID(quoteID: UInt64, quoteeHexEncodedPublicKey: String, threadID: String, transaction: YapDatabaseReadTransaction) -> UInt64 {
+        guard let message = TSInteraction.interactions(withTimestamp: quoteID, filter: { interaction in
+            let senderHexEncodedPublicKey: String
+            if let message = interaction as? TSIncomingMessage {
+                senderHexEncodedPublicKey = message.authorId
+            } else if let message = interaction as? TSOutgoingMessage {
+                senderHexEncodedPublicKey = OWSIdentityManager.shared().identityKeyPair()!.hexEncodedPublicKey
+            } else {
+                return false
+            }
+            return (senderHexEncodedPublicKey == quoteeHexEncodedPublicKey) && (interaction.uniqueThreadId == threadID)
+        }, with: transaction).first as! TSMessage? else { return 0 }
+        return message.groupChatMessageID
+    }
+}

SignalServiceKit/src/Loki/Database/OWSPrimaryStorage+Loki.swift

@@ -1,6 +1,6 @@
 
-extension OWSPrimaryStorage {
-    
+public extension OWSPrimaryStorage {
+
     private func getCollection(for primaryDevice: String) -> String {
         return "LokiDeviceLinkCollection-\(primaryDevice)"
     }

SignalServiceKit/src/Messages/OWSMessageSender.m

@@ -1148,8 +1148,14 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
         NSString *displayName = SSKEnvironment.shared.profileManager.localProfileName;
         if (displayName == nil) { displayName = @"Anonymous"; }
         TSQuotedMessage *quote = message.quotedMessage;
+        uint64_t quoteID = quote.timestamp;
+        NSString *quoteeHexEncodedPublicKey = quote.authorId;
+        __block uint64_t quotedMessageServerID;
+        [self.dbConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
+            quotedMessageServerID = [LKDatabaseUtilities getServerIDForQuoteWithID:quoteID quoteeHexEncodedPublicKey:quoteeHexEncodedPublicKey threadID:messageSend.thread.uniqueId transaction:transaction];
+        }];
         LKGroupMessage *groupMessage = [[LKGroupMessage alloc] initWithHexEncodedPublicKey:userHexEncodedPublicKey displayName:displayName body:message.body type:LKGroupChatAPI.publicChatMessageType
-            timestamp:message.timestamp quotedMessageTimestamp:quote.timestamp quoteeHexEncodedPublicKey:quote.authorId quotedMessageBody:quote.body];
+         timestamp:message.timestamp quotedMessageTimestamp:quoteID quoteeHexEncodedPublicKey:quoteeHexEncodedPublicKey quotedMessageBody:quote.body quotedMessageServerID:quotedMessageServerID hexEncodedSignatureData:nil signatureVersion:0];
         [[LKGroupChatAPI sendMessage:groupMessage toGroup:LKGroupChatAPI.publicChatServerID onServer:LKGroupChatAPI.publicChatServer]
         .thenOn(OWSDispatch.sendingQueue, ^(LKGroupMessage *groupMessage) {
             [self.dbConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {