How to disable line editing on the server and get a raw bytes process?

[xandaaah]

My script is just a fancy wrapper around ssh to forward the connection to an internal server, accomplished using process.redirect. Whenever I use .set_line_mode(False), the connection just closes. When I pass line_editor=False to asyncssh.listen, it changes the class of process.channel, but it still echoes lines edited, and displays cursor movements. ANSI doesn't work, it throws an error about strings. Seriously, what do I do to enable byte support and line editing? I'm at a complete loss.

[ronf]

If you want to read and write bytes instead of Unicode strings, you need to set encoding=None when opening up the channel. You can also set this when opening a connection, and the value set there will apply to all channels on that connection.

If you're just trying to pass bytes through some kind of tunnel, you probably should avoid requesting a PTY or setting term_type on the tunnel, and that will avoid any line editor getting involved without having to explicitly disable it.

[xandaaah]

Thanks for the advice on the bytes issue, but I still have the issue that it still seems to be in line editing mode. I'd assume this is due to my hacky solution of just using OpenSSH to connect to the server and redirecting, but it just doesn't work with the asyncssh client.
These are the 2 relevant sections of my code:

async with asyncssh.connect(host="127.0.0.1", username="root", password="abc") as conn:
                proc = await conn.create_process(
                    f"lxc-attach 101",
                    term_size=process.term_size,
                    term_type=process.term_type
                )
                await process.redirect(stdin=proc.stdin, stdout=proc.stdout,
                                stderr=proc.stderr)
                await process.stdout.drain()
                await proc.wait()
                await process.stdout.drain()
                traceback.print_exception(proc._exception)
..snip..
async def start_server() -> None:

    _ = await asyncssh.listen('', 1550, server_host_keys=['test_rsa.key'],
                          authorized_client_keys='/home/user/.ssh/id_ed25519.pub',
                          process_factory=handle_client, line_editor=False, encoding=None)

proc._exception is set to the following exception:

Traceback (most recent call last):
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/connection.py", line 1529, in _recv_data
    while self._inpbuf and self._recv_handler():
                           ^^^^^^^^^^^^^^^^^^^^
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/connection.py", line 1689, in _recv_packet
    result = handler.process_packet(pkttype, seq, packet)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/packet.py", line 238, in process_packet
    return self._packet_handlers[pkttype](self, pkttype,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/channel.py", line 614, in _process_extended_data
    self._accept_data(data, datatype)
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/channel.py", line 412, in _accept_data
    self._deliver_data(data, datatype)
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/channel.py", line 389, in _deliver_data
    self._session.data_received(decoded_data, datatype)
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/process.py", line 1064, in data_received
    writer.write(data)
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/process.py", line 518, in write
    self._process.feed_data(data, self._datatype)
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/process.py", line 1097, in feed_data
    self._chan.write(data, datatype)
  File "PROJECT_FOLDER/.venv/lib/python3.12/site-packages/asyncssh/channel.py", line 948, in write
    self._send_buf.append((bytearray(encoded_data), datatype))
                           ^^^^^^^^^^^^^^^^^^^^^^^
TypeError: string argument without an encoding

I thought I was good at tracebacks after dealing with Java for a while, but clearly I wasn't as good as I thought I was. This makes no sense to me. What gives?

[ronf]

You are setting encoding here on the listen() call, so that means the process passed in to your handle_client() is going to be receiving raw bytes when receiving data. However, you are NOT setting encoding in your call to create_process(). So, it's going to be expecting you to pass in strings when you write data. This mismatch will lead to problems when you set up the redirects. The encodings need to match on the inbound process and outbound process for redirects to work.

As for the line editor, you are passing through the terminal type, so if a terminal was requested by the SSH client connection to the AsyncSSH listener, it will request a terminal upstream as well. That sort of makes sense in your use case, but that means the line editor might be enabled by default, and so you'll want to explicitly set that to False in the listen() call, which you are already doing here. So, you should be ok on that front.