Add support for Unix FD passing

During compilation, this requires Mono.Posix from mono with commit
2225b6a260e1f0d469e37ec0df68a89e832688cd (i.e. mono 4.6 or later).
During runtime it will fall back to an implementation which does not support
Unix FD passing when the Mono.Posix version is too old.

An example showing how to pass file descriptors can be found in
examples/UnixFD*.cs

examples/UnixFDClient.cs

@@ -0,0 +1,142 @@
+// Copyright 2017 Steffen Kiess <[email protected]>
+// This software is made available under the MIT License
+// See COPYING for details
+
+using System;
+
+using DBus;
+using org.freedesktop.DBus;
+
+using Mono.Unix;
+using Mono.Unix.Native;
+
+class SignalsImpl : Signals {
+	public event Action<UnixFD> GotFD;
+
+	public void CallGotFD (UnixFD fd) {
+		var handler = GotFD;
+		if (handler != null)
+			handler (fd);
+	}
+}
+
+public class ManagedDBusTest
+{
+	public static void Main (string[] args)
+	{
+		Bus conn;
+
+		if (args.Length == 0)
+			conn = Bus.Session;
+		else {
+			if (args[0] == "--session")
+				conn = Bus.Session;
+			else if (args[0] == "--system")
+				conn = Bus.System;
+			else
+				conn = Bus.Open (args[0]);
+		}
+
+		IBus bus = conn.GetObject<IBus> ("org.freedesktop.DBus", new ObjectPath ("/org/freedesktop/DBus"));
+		Console.WriteLine (bus.ListNames ().Length);
+
+		var obj = conn.GetObject<Interface> (Constants.BusName, Constants.ObjectPath);
+		var obj2 = conn.GetObject<Interface2> (Constants.BusName, Constants.ObjectPath);
+		var objIntr = conn.GetObject<Introspectable> (Constants.BusName, Constants.ObjectPath);
+		obj.Ping ();
+		Console.WriteLine (obj.GetBytes (3).Length);
+
+		Console.WriteLine ("conn.UnixFDSupported = " + conn.UnixFDSupported);
+		if (!conn.UnixFDSupported)
+			return;
+
+		using (var disposableList = new DisposableList ()) {
+			var res = obj.GetFD (disposableList, false);
+			Console.WriteLine ("Got FD:");
+			Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + res.Handle);
+		}
+		using (var disposableList = new DisposableList ()) {
+			var res = obj.GetFDList (disposableList, false);
+			Console.WriteLine ("Got FDs:");
+			foreach (var fd in res)
+				Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + fd.Handle);
+		}
+		using (var disposableList = new DisposableList ()) {
+			var res = (UnixFD[]) obj.GetFDListVariant (disposableList, false);
+			Console.WriteLine ("Got FDs as variant:");
+			foreach (var fd in res)
+				Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + fd.Handle);
+		}
+
+		using (var disposableList = new DisposableList ()) {
+			try {
+				obj.GetFD (disposableList, true);
+				throw new Exception ("Expected an exception");
+			} catch (Exception e) {
+				if (!e.Message.Contains ("Throwing an exception after creating a UnixFD object"))
+					throw;
+			}
+		}
+		using (var disposableList = new DisposableList ()) {
+			try {
+				obj.GetFDList (disposableList, true);
+				throw new Exception ("Expected an exception");
+			} catch (Exception e) {
+				if (!e.Message.Contains ("Throwing an exception after creating a UnixFD object"))
+					throw;
+			}
+		}
+		using (var disposableList = new DisposableList ()) {
+			try {
+				obj.GetFDListVariant (disposableList, true);
+				throw new Exception ("Expected an exception");
+			} catch (Exception e) {
+				if (!e.Message.Contains ("Throwing an exception after creating a UnixFD object"))
+					throw;
+			}
+		}
+
+		// Check whether this leaks an FD
+		obj.GetFD (null, false);
+		obj.GetFDList (null, false);
+		obj.GetFDListVariant (null, false);
+		try { obj.GetFD (null, true); } catch {}
+		try { obj.GetFDList (null, true); } catch {}
+		try { obj.GetFDListVariant (null, true); } catch {}
+		obj2.GetFD (false);
+		obj2.GetFDList (false);
+		obj2.GetFDListVariant (false);
+		try { obj2.GetFD (true); } catch {}
+		try { obj2.GetFDList (true); } catch {}
+		try { obj2.GetFDListVariant (true); } catch {}
+
+		var fd_ = Syscall.open ("/dev/null", OpenFlags.O_RDWR, 0);
+		if (fd_ < 0)
+			UnixMarshal.ThrowExceptionForLastError ();
+		using (var fd = new UnixFD (fd_)) {
+			obj.SendFD (fd);
+			obj.SendFD (fd);
+			obj.SendFDList (new UnixFD[] { fd, fd });
+			obj.SendFDListVariant (new UnixFD[] { fd, fd });
+
+			var impl = new SignalsImpl ();
+			var spath = new ObjectPath ("/mono_dbus_sharp_test/Signals");
+			conn.Register (spath, impl);
+			obj.RegisterSignalInterface (conn.UniqueName, spath);
+			impl.CallGotFD (fd);
+		}
+
+		Console.WriteLine (objIntr.Introspect ().Length);
+
+		obj.ListOpenFDs ();
+		Console.WriteLine ("Open FDs:");
+		Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/");
+	}
+}
+
+// vim: noexpandtab
+// Local Variables:
+// tab-width: 4
+// c-basic-offset: 4
+// indent-tabs-mode: t
+// End:

examples/UnixFDInterface.cs

@@ -0,0 +1,61 @@
+// Copyright 2017 Steffen Kiess <[email protected]>
+// This software is made available under the MIT License
+// See COPYING for details
+
+using System;
+using DBus;
+
+public static class Constants {
+	public const string BusName = "mono_dbus_sharp_test.UnixFDService";
+	public static readonly ObjectPath ObjectPath = new ObjectPath ("/mono_dbus_sharp_test/UnixFDService");
+}
+
+[DBus.Interface ("mono_dbus_sharp_test.UnixFDService")]
+public interface Interface {
+	void Ping ();
+
+	void ListOpenFDs ();
+
+	byte[] GetBytes (int len);
+
+	UnixFD GetFD (DisposableList disposableList, bool throwError);
+	UnixFD[] GetFDList (DisposableList disposableList, bool throwError);
+	object GetFDListVariant (DisposableList disposableList, bool throwError);
+
+	void SendFD (UnixFD fd);
+	void SendFDList (UnixFD[] fds);
+	void SendFDListVariant (object fds);
+
+	void RegisterSignalInterface (string busName, ObjectPath path);
+}
+
+[DBus.Interface ("mono_dbus_sharp_test.UnixFDService")]
+public interface Interface2 {
+	void Ping ();
+
+	void ListOpenFDs ();
+
+	byte[] GetBytes (int len);
+
+	UnixFD GetFD (bool throwError);
+	UnixFD[] GetFDList (bool throwError);
+	object GetFDListVariant (bool throwError);
+
+	void SendFD (UnixFD fd);
+	void SendFDList (UnixFD[] fds);
+	void SendFDListVariant (object fds);
+
+	void RegisterSignalInterface (string busName, ObjectPath path);
+}
+
+[DBus.Interface ("mono_dbus_sharp_test.UnixFDSignals")]
+public interface Signals {
+	event Action<UnixFD> GotFD;
+}
+
+// vim: noexpandtab
+// Local Variables:
+// tab-width: 4
+// c-basic-offset: 4
+// indent-tabs-mode: t
+// End:

examples/UnixFDService.cs

@@ -0,0 +1,137 @@
+// Copyright 2017 Steffen Kiess <[email protected]>
+// This software is made available under the MIT License
+// See COPYING for details
+
+/*
+PATH="$HOME/mono-master/bin:$PATH" ./autogen.sh && make -j8
+make && ( cd examples && mcs -g UnixFDService.cs UnixFDInterface.cs -r ../src/dbus-sharp.dll -r Mono.Posix ) && MONO_PATH=src $HOME/mono-master/bin/mono --debug examples/UnixFDService.exe
+make && ( cd examples && mcs -g UnixFDClient.cs UnixFDInterface.cs -r ../src/dbus-sharp.dll -r Mono.Posix ) && MONO_PATH=src $HOME/mono-master/bin/mono --debug examples/UnixFDClient.exe
+
+python3
+import dbus; dbus.SessionBus().get_object('mono_dbus_sharp_test.UnixFDService', '/mono_dbus_sharp_test/UnixFDService').GetBytes(3)
+import dbus; f = dbus.SessionBus().get_object('mono_dbus_sharp_test.UnixFDService', '/mono_dbus_sharp_test/UnixFDService').GetFD ()
+*/
+
+using System;
+
+using Mono.Unix;
+using Mono.Unix.Native;
+
+using DBus;
+using org.freedesktop.DBus;
+
+public class Impl : Interface {
+	Connection conn;
+
+	public Impl (Connection conn)
+	{
+		this.conn = conn;
+	}
+
+	public void Ping ()
+	{
+	}
+
+	public void ListOpenFDs ()
+	{
+		Console.WriteLine ("Open FDs:");
+		Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/");
+	}
+
+	public UnixFD GetFD (DisposableList disposableList, bool throwError)
+	{
+		var fd_ = Syscall.open ("/dev/null", OpenFlags.O_RDWR, 0);
+		if (fd_ < 0)
+			UnixMarshal.ThrowExceptionForLastError ();
+		var fd = new UnixFD (fd_);
+		disposableList.Add (fd);
+
+		if (throwError)
+			throw new Exception ("Throwing an exception after creating a UnixFD object");
+
+		return fd;
+	}
+
+	public UnixFD[] GetFDList (DisposableList disposableList, bool throwError)
+	{
+		return new UnixFD[] {
+			GetFD (disposableList, false), GetFD (disposableList, throwError), GetFD (disposableList, false)
+		};
+	}
+
+	public object GetFDListVariant (DisposableList disposableList, bool throwError)
+	{
+		return GetFDList (disposableList, throwError);
+	}
+
+	public byte[] GetBytes (int len)
+	{
+		return new byte[len];
+	}
+
+	public void SendFD (UnixFD fd)
+	{
+		Console.WriteLine ("Got FD as parameter:");
+		Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + fd.Handle);
+	}
+
+	public void SendFDList (UnixFD[] fds)
+	{
+		Console.WriteLine ("Got FDs as parameter:");
+		foreach (var fd in fds)
+			Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + fd.Handle);
+	}
+
+	public void SendFDListVariant (object fds)
+	{
+		Console.WriteLine ("Got FDs as variant parameter:");
+		foreach (var fd in (UnixFD[]) fds)
+			Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + fd.Handle);
+	}
+
+	public void RegisterSignalInterface (string busName, ObjectPath path)
+	{
+		Console.WriteLine ("Register for GotFD event at {0} / {1}", busName, path);
+		conn.GetObject<Signals> (busName, path).GotFD += fd => {
+			Console.WriteLine ("Got FD from signal:");
+			Mono.Unix.Native.Stdlib.system ("ls -l /proc/$PPID/fd/" + fd.Handle);
+		};
+	}
+}
+
+public class UnixFDService
+{
+	public static void Main (string[] args)
+	{
+		Bus conn;
+
+		if (args.Length == 0)
+			conn = Bus.Session;
+		else {
+			if (args[0] == "--session")
+				conn = Bus.Session;
+			else if (args[0] == "--system")
+				conn = Bus.System;
+			else
+				conn = Bus.Open (args[0]);
+		}
+
+		conn.Register (Constants.ObjectPath, new Impl (conn));
+
+		if (conn.RequestName (Constants.BusName) != org.freedesktop.DBus.RequestNameReply.PrimaryOwner)
+			throw new Exception ("Could not request name");
+
+		Console.WriteLine ("Waiting for requests...");
+
+		while (conn.IsConnected) {
+			conn.Iterate ();
+		}
+	}
+}
+
+// vim: noexpandtab
+// Local Variables:
+// tab-width: 4
+// c-basic-offset: 4
+// indent-tabs-mode: t
+// End:

src/Authentication.cs

@@ -324,6 +324,8 @@ public virtual bool Run (IEnumerable<AuthCommand> commands)
 	class SaslClient : SaslPeer
 	{
 		public string Identity = String.Empty;
+		public bool TransportSupportsUnixFD = false;
+		public bool UnixFDSupported = false;
 
 		//static Regex rejectedRegex = new Regex (@"^REJECTED(\s+(\w+))*$");
 
@@ -387,6 +389,14 @@ public override IEnumerator<AuthCommand> GetEnumerator ()
 				else
 					ActualId = UUID.Parse (reply[1]);
 
+				if (TransportSupportsUnixFD) {
+					yield return new AuthCommand ("NEGOTIATE_UNIX_FD");
+					if (!replies.MoveNext ())
+						yield break;
+					reply = replies.Current;
+					UnixFDSupported = reply[0] == "AGREE_UNIX_FD";
+				}
+
 				yield return new AuthCommand ("BEGIN");
 				yield break;
 			}