Invalid TPKT size was detected

[HsuJv]

Hi @citronneur ,

Thanks for your amazing work to bringing us this crate.
I'm trying to build a wasm application based on your work.
But got some unexpected error "Invalid minimal size for TPKT"
I tried to ignore it and it seems can restore itself.
But when looking through your mstsc-rs code, it seems the program shall be terminated when the error occurs

rdp-rs/src/bin/mstsc-rs.rs

Lines 325 to 344 in 7ac880d

	while wait_for_fd(handle as usize) && sync.load(Ordering::Relaxed) {
	let mut guard = rdp_client.lock().unwrap();
	if let Err(Error::RdpError(e)) = guard.read(|event| {
	match event {
	RdpEvent::Bitmap(bitmap) => {
	bitmap_channel.send(bitmap).unwrap();
	},
	_ => println!("{}: ignore event", APPLICATION_NAME)
	}
	}) {
	match e.kind() {
	RdpErrorKind::Disconnect => {
	println!("{}: Server ask for disconnect", APPLICATION_NAME);
	},
	_ => println!("{}: {:?}", APPLICATION_NAME, e)
	}
	break;
	}
	}
	}))

See the screenshot which shows it continues to work when the error shows up.

Do you have any idea about this error? 'cuz I cannot observe it when using the mstsc-rs which makes me confused.

BTW, the errors happens at line 142 #1, 159 #2, 166 #3 with the tuple (action, length) shown in the screenshot

rdp-rs/src/core/tpkt.rs

Lines 124 to 172 in 7ac880d

	pub fn read(&mut self) -> RdpResult<Payload> {
	let mut buffer = Cursor::new(self.transport.read(2)?);
	let mut action: u8 = 0;
	action.read(&mut buffer)?;
	if action == Action::FastPathActionX224 as u8 {
	// read padding
	let mut padding: u8 = 0;
	padding.read(&mut buffer)?;
	// now wait extended header
	buffer = Cursor::new(self.transport.read(2)?);
	let mut size = U16::BE(0);
	size.read(&mut buffer)?;
	// Minimal size must be 7
	// https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/18a27ef9-6f9a-4501-b000-94b1fe3c2c10
	if size.inner() < 4 {
	Err(Error::RdpError(RdpError::new(RdpErrorKind::InvalidSize, "Invalid minimal size for TPKT")))
	}
	else {
	// now wait for body
	Ok(Payload::Raw(Cursor::new(self.transport.read(size.inner() as usize - 4)?)))
	}
	} else {
	// fast path
	let sec_flag = (action >> 6) & 0x3;
	let mut short_length: u8 = 0;
	short_length.read(&mut buffer)?;
	if short_length & 0x80 != 0 {
	let mut hi_length: u8 = 0;
	hi_length.read(&mut Cursor::new(self.transport.read(1)?))?;
	let length: u16 = ((short_length & !0x80) as u16) << 8;
	let length = length | hi_length as u16;
	if length < 3 {
	Err(Error::RdpError(RdpError::new(RdpErrorKind::InvalidSize, "Invalid minimal size for TPKT")))
	} else {
	Ok(Payload::FastPath(sec_flag, Cursor::new(self.transport.read(length as usize - 3)?)))
	}
	}
	else {
	if short_length < 2 {
	Err(Error::RdpError(RdpError::new(RdpErrorKind::InvalidSize, "Invalid minimal size for TPKT")))
	} else {
	Ok(Payload::FastPath(sec_flag, Cursor::new(self.transport.read(short_length as usize - 2)?)))
	}
	}
	}
	}

Thanks in advance

[HsuJv]

Just for your information
I tried to propagate the warning from the library itself to the web console and got the following result

It seems that the tpkt error is not predictive and has nothing to do with the previous warning.

App build from https://github.com/HsuJv/webgateway/tree/main/webrdp if you want to review the client-side code