Using `wantReply` on an `ChannelSignalMessage` can lead to deadlock

[cmbrose]

In both the C# and TS implementations, the ChannelSignalMessage explicitly sets wantReply to false before sending:

dev-tunnels-ssh/src/ts/ssh/messages/connectionMessages.ts

Line 403 in 1cd94f9

this.wantReply = false;

However, this change is done while the message is being written to binary, after the SshChannel checks the value:

dev-tunnels-ssh/src/ts/ssh/sshChannel.ts

Line 201 in 1cd94f9

if (!request.wantReply) {

This means that if you set wantReply on the message, the SshChannel will wait for a response which will never come, because it wasn't actually asked for.

This is easy to reproduce:

const signalMessage = new ChannelSignalMessage();
signalMessage.signal = 'INT';
signalMessage.wantReply = true;

// get a channel...

const res = await channel.request(signalMessage); // Deadlock!

There's no comment on the line that overrides the wantReply value so I'm not sure the purpose of it - reading the OpenSSH source it seems like wantReply is valid for a signal message and would be handled.

If this is intentional, it would probably just be best to remove the wantReply property from the ChannelSignalMessage. Otherwise, it would be good to remove the override.