Add support for sending/receiving unix file descriptors.

Fixes canonical#245.

lib/src/dbus_auth_client.dart

@@ -11,6 +11,7 @@ class DBusAuthClient {
   final _requestsController = StreamController<String>();
   var _attemptedExternal = false;
   var _isAuthenticated = false;
+  final bool _requestUnixFd;
   var _unixFdSupported = false;
   DBusUUID? _uuid;
   String? _errorMessage;
@@ -34,7 +35,7 @@ class DBusAuthClient {
   String? get errorMessage => _errorMessage;
 
   /// Creates a new authentication client.
-  DBusAuthClient() {
+  DBusAuthClient({bool requestUnixFd = true}) : _requestUnixFd = requestUnixFd {
     // On start, end an empty byte, as this is required if sending the credentials as a socket control message.
     // We rely on the server using SO_PEERCRED to check out credentials.
     // Then request the supported mechanisms.
@@ -83,18 +84,27 @@ class DBusAuthClient {
           return;
         }
         _isAuthenticated = true;
-        _send('BEGIN');
-        _doneCompleter.complete();
+        if (_requestUnixFd) {
+          _send('NEGOTIATE_UNIX_FD');
+        } else {
+          _begin();
+        }
         break;
       case 'DATA':
         _fail('Unable to handle DATA command');
         break;
       case 'ERROR':
-        _errorMessage = args;
-        _doneCompleter.complete();
+        if (isAuthenticated) {
+          // Error was from NEGOTIATE_UNIX_FD, can continue without this.
+          _begin();
+        } else {
+          _errorMessage = args;
+          _doneCompleter.complete();
+        }
         break;
       case 'AGREE_UNIX_FD':
         _unixFdSupported = true;
+        _begin();
         break;
       default:
         _fail("Unknown command '$command'");
@@ -130,4 +140,10 @@ class DBusAuthClient {
     }
     _send('AUTH EXTERNAL $authIdHex');
   }
+
+  /// Complete authentication.
+  void _begin() {
+    _send('BEGIN');
+    _doneCompleter.complete();
+  }
 }

lib/src/dbus_auth_server.dart

@@ -6,7 +6,7 @@ import 'dbus_uuid.dart';
 class DBusAuthServer {
   final _responsesController = StreamController<String>();
   bool _readSocketControlMessage = false;
-  var _externalDone = false;
+  var _sentOk = false;
   var _isAuthenticated = false;
 
   /// Unique ID for this connection.
@@ -63,7 +63,7 @@ class DBusAuthServer {
         _reject('Cancelled');
         break;
       case 'BEGIN':
-        if (_externalDone) {
+        if (_sentOk) {
           _isAuthenticated = true;
         }
         break;
@@ -74,7 +74,11 @@ class DBusAuthServer {
         _reject('Received error');
         break;
       case 'NEGOTIATE_UNIX_FD':
-        _error('Unix fd not supported');
+        if (_sentOk) {
+          _send('AGREE_UNIX_FD');
+        } else {
+          _error('Not authenticated');
+        }
         break;
       default:
         _error("Unknown command '$command'");
@@ -100,7 +104,7 @@ class DBusAuthServer {
   /// Do authentication using the EXTERNAL mechanism.
   void _authenticateExternal(String uid) {
     // Note uid isn't checked.
-    _externalDone = true;
+    _sentOk = true;
     _send('OK ${uuid.toHexString()}');
   }
 

lib/src/dbus_client.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
 
@@ -175,9 +176,10 @@ class DBusSignalSignatureException implements Exception {
 /// A client connection to a D-Bus server.
 class DBusClient {
   final DBusAddress _address;
-  Socket? _socket;
+  RawSocket? _socket;
   final _readBuffer = DBusReadBuffer();
   final _authClient = DBusAuthClient();
+  var _authComplete = false;
   Completer? _connectCompleter;
   var _lastSerial = 0;
   final _methodCalls = <int, Completer<DBusMethodResponse>>{};
@@ -719,16 +721,13 @@ class DBusClient {
         throw 'D-Bus address transport not supported: $_address';
     }
 
-    _socket = await Socket.connect(socketAddress, port);
-    _socket?.listen(_processData);
-  }
-
-  /// Performs authentication with D-Bus server.
-  Future<bool> _authenticate() async {
-    _authClient.requests.listen((message) => _socket?.write(message + '\r\n'));
-    await _authClient.done;
-
-    return _authClient.isAuthenticated;
+    _socket = await RawSocket.connect(socketAddress, port);
+    _socket?.listen((event) {
+      // NOTE: Should wait for RawSocketEvent.write for writes too.
+      if (event == RawSocketEvent.read) {
+        _readData();
+      }
+    });
   }
 
   /// Connects to the D-Bus server.
@@ -740,7 +739,11 @@ class DBusClient {
     _connectCompleter = Completer();
 
     await _openSocket();
-    if (!await _authenticate()) {
+    _authClient.requests
+        .listen((message) => _socket?.write(utf8.encode(message + '\r\n')));
+    await _authClient.done;
+    _authComplete = true;
+    if (!_authClient.isAuthenticated) {
       await _socket?.close();
       return;
     }
@@ -859,13 +862,27 @@ class DBusClient {
     }
   }
 
-  /// Processes incoming data from the D-Bus server.
-  void _processData(Uint8List data) {
+  /// Read incoming data from the D-Bus server.
+  void _readData() {
+    var data = _socket?.read();
+    if (data == null) {
+      return;
+    }
     _readBuffer.writeBytes(data);
 
+    // FIXME: Once supported the above should be replaced with:
+    //var message = _socket?.receiveMessage();
+    //if (message == null) {
+    //  return;
+    //}
+    //_readBuffer.writeBytes(message.data);
+    //for (var message in message.controlMessages.where((message) => message is UnixFileDescriptorsControlMessage)) {
+    //  readBuffer.addFileDescriptors(message.fileDescriptors);
+    //}
+
     var complete = false;
     while (!complete) {
-      if (!_authClient.isAuthenticated) {
+      if (!_authComplete) {
         complete = _processAuth();
       } else {
         complete = _processMessages();
@@ -1126,7 +1143,15 @@ class DBusClient {
   void _sendMessage(DBusMessage message) {
     var buffer = DBusWriteBuffer();
     buffer.writeMessage(message);
-    _socket?.add(buffer.data);
+
+    _socket?.write(buffer.data);
+
+    // FIXME: Once supported the above should be replaced with:
+    //var controlMessages = <SocketControlMessage>[];
+    //if (buffer.fileDescriptors.isNotEmpty) {
+    //    controlMessages.add(UnixFileDescriptorsControlMessage(buffer.fileDescriptors));
+    //}
+    //_socket?.sendMessage(controlMessages, buffer.data);
   }
 
   @override

lib/src/dbus_read_buffer.dart

@@ -14,6 +14,9 @@ class DBusReadBuffer extends DBusBuffer {
   /// Data in the buffer.
   var _data = Uint8List(0);
 
+  /// Unix file descriptors available.
+  var _fileDescriptors = <int>[];
+
   /// View of the buffer to allow accessing fixed width integers and floats.
   late ByteData _view;
 
@@ -34,6 +37,11 @@ class DBusReadBuffer extends DBusBuffer {
     _view = ByteData.view(_data.buffer);
   }
 
+  /// Add received file descriptors.
+  void addFileDescriptors(List<int> fds) {
+    _fileDescriptors.addAll(fds);
+  }
+
   /// Read a single byte from the buffer.
   int _readByte() {
     readOffset++;
@@ -152,9 +160,6 @@ class DBusReadBuffer extends DBusBuffer {
         signature = value as DBusSignature;
       } else if (code == 9) {
         fdCount = (value as DBusUint32).value;
-        if (fdCount != 0) {
-          throw 'Message contains file descriptors, which are not supported';
-        }
       }
     }
     if (!align(8)) {
@@ -170,7 +175,7 @@ class DBusReadBuffer extends DBusBuffer {
     if (signature != null) {
       var signatures = signature.split();
       for (var s in signatures) {
-        var value = readDBusValue(s, endian);
+        var value = readDBusValue(s, endian, fdCount);
         if (value == null) {
           return null;
         }
@@ -188,6 +193,13 @@ class DBusReadBuffer extends DBusBuffer {
       }
     }
 
+    // Remove file descriptors that were part of this message.
+    // Note: This could remove descriptors added after the end of the message.
+    if (_fileDescriptors.length < fdCount) {
+      throw 'Insufficient file descriptors received';
+    }
+    _fileDescriptors.removeRange(0, fdCount);
+
     return DBusMessage(type,
         flags: flags,
         serial: serial,
@@ -392,6 +404,21 @@ class DBusReadBuffer extends DBusBuffer {
     return DBusVariant(childValue);
   }
 
+  /// Reads a [DBusUnixFd] from the buffer or returns null if not enough data.
+  DBusUnixFd? readDBusUnixFd(int fdCount, [Endian endian = Endian.little]) {
+    var index = readDBusUint32()?.value;
+    if (index == null) {
+      return null;
+    }
+    if (index > fdCount) {
+      throw 'Unix fd index out of bounds';
+    }
+    if (index > _fileDescriptors.length) {
+      throw 'Unix fd $index not yet received';
+    }
+    return DBusUnixFd(_fileDescriptors[index]);
+  }
+
   /// Reads a [DBusStruct] from the buffer or returns null if not enough data.
   DBusStruct? readDBusStruct(Iterable<DBusSignature> childSignatures,
       [Endian endian = Endian.little]) {
@@ -458,7 +485,7 @@ class DBusReadBuffer extends DBusBuffer {
 
   /// Reads a [DBusValue] with [signature].
   DBusValue? readDBusValue(DBusSignature signature,
-      [Endian endian = Endian.little]) {
+      [Endian endian = Endian.little, int fdCount = 0]) {
     var s = signature.value;
     if (s == 'y') {
       return readDBusByte();
@@ -488,6 +515,8 @@ class DBusReadBuffer extends DBusBuffer {
       return readDBusVariant(endian);
     } else if (s == 'm') {
       throw 'D-Bus reserved maybe type not valid';
+    } else if (s == 'h') {
+      return readDBusUnixFd(fdCount, endian);
     } else if (s.startsWith('a{') && s.endsWith('}')) {
       var childSignature = DBusSignature(s.substring(2, s.length - 1));
       var signatures = childSignature.split();

lib/src/dbus_server.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'dart:io';
 import 'dart:math';
 import 'dart:typed_data';
@@ -62,7 +63,7 @@ class _DBusRemoteClient {
   DBusServer get server => serverSocket.server;
 
   /// The socket this client is communicating on.
-  final Socket _socket;
+  final RawSocket _socket;
 
   /// Incoming data.
   final _readBuffer = DBusReadBuffer();
@@ -81,8 +82,13 @@ class _DBusRemoteClient {
 
   _DBusRemoteClient(this.serverSocket, this._socket, this.uniqueName)
       : _authServer = DBusAuthServer(serverSocket.uuid) {
-    _authServer.responses.listen((message) => _socket.write(message + '\r\n'));
-    _socket.listen(_processData);
+    _authServer.responses
+        .listen((message) => _socket.write(utf8.encode(message + '\r\n')));
+    _socket.listen((event) {
+      if (event == RawSocketEvent.read) {
+        _readData();
+      }
+    });
   }
 
   /// True if this client has a rule that matches [message].
@@ -109,17 +115,38 @@ class _DBusRemoteClient {
   void sendMessage(DBusMessage message) {
     var buffer = DBusWriteBuffer();
     buffer.writeMessage(message);
-    _socket.add(buffer.data);
+    _socket.write(buffer.data);
+
+    // FIXME: Once supported the above should be replaced with:
+    //var controlMessages = <SocketControlMessage>[];
+    //if (buffer.fileDescriptors.isNotEmpty) {
+    //    controlMessages.add(UnixFileDescriptorsControlMessage(buffer.fileDescriptors));
+    //}
+    //_socket?.sendMessage(controlMessages, buffer.data);
   }
 
   Future<void> close() async {
     await _socket.close();
   }
 
-  /// Processes incoming data from this D-Bus client.
-  void _processData(Uint8List data) {
+  /// Reads incoming data from this D-Bus client.
+  void _readData() {
+    var data = _socket.read();
+    if (data == null) {
+      return;
+    }
     _readBuffer.writeBytes(data);
 
+    // FIXME: Once supported the above should be replaced with:
+    //var message = _socket?.receiveMessage();
+    //if (message == null) {
+    //  return;
+    //}
+    //_readBuffer.writeBytes(message.data);
+    //for (var message in message.controlMessages.where((message) => message is UnixFileDescriptorsControlMessage)) {
+    //  readBuffer.addFileDescriptors(message.fileDescriptors);
+    //}
+
     var complete = false;
     while (!complete) {
       if (!_authServer.isAuthenticated) {
@@ -177,7 +204,7 @@ class _DBusServerSocket {
   final DBusServer server;
 
   /// Socket being listened on.
-  final ServerSocket socket;
+  final RawServerSocket socket;
 
   /// Id for this connection.
   final int connectionId;
@@ -445,7 +472,7 @@ class DBusServer {
 
   Future<_DBusServerSocket> _addServerSocket(
       InternetAddress address, int port) async {
-    var socket = await ServerSocket.bind(address, port);
+    var socket = await RawServerSocket.bind(address, port);
     var serverSocket = _DBusServerSocket(this, socket, _nextConnectionId);
     _sockets.add(serverSocket);
     _nextConnectionId++;