vnc/lib.rs
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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
//! A VNC server implementation.
#![expect(missing_docs)]
mod rfb;
mod scancode;
use futures::AsyncReadExt;
use futures::AsyncWriteExt;
use futures::FutureExt;
use futures::StreamExt;
use futures::channel::mpsc;
use futures::future::OptionFuture;
use pal_async::socket::PolledSocket;
use thiserror::Error;
use zerocopy::FromZeros;
use zerocopy::IntoBytes;
#[derive(Debug, Error)]
pub enum Error {
#[error("unsupported protocol version")]
UnsupportedVersion(rfb::ProtocolVersion),
#[error("unsupported message type: {0:#x}")]
UnknownMessage(u8),
#[error("unsupported qemu message type: {0:#x}")]
UnknownQemuMessage(u8),
#[error("socket error")]
Io(#[from] std::io::Error),
#[error("client does not support desktop resize extension")]
DesktopResizeNotSupported,
}
/// A trait used to retrieve data from a framebuffer.
pub trait Framebuffer: Send + Sync {
fn resolution(&mut self) -> (u16, u16);
fn read_line(&mut self, line: u16, data: &mut [u8]);
}
pub const HID_MOUSE_MAX_ABS_VALUE: u32 = 0x7FFFu32;
/// A VNC server handling a single connection.
pub struct Server<F, I> {
socket: PolledSocket<socket2::Socket>,
fb: F,
input: I,
update_recv: mpsc::Receiver<()>,
update_send: mpsc::Sender<()>,
name: String,
// ctrl-alt-p paste intercept
ctrl_left_pressed: bool,
alt_left_pressed: bool,
clipboard: String,
}
#[derive(Debug, Clone)]
pub struct Updater(mpsc::Sender<()>);
impl Updater {
pub fn update(&self) {
let _ = self.0.clone().try_send(());
}
}
/// A trait used to handle VNC client input.
pub trait Input {
fn key(&mut self, scancode: u16, is_down: bool);
fn mouse(&mut self, button_mask: u8, x: u16, y: u16);
}
impl<F: Framebuffer, I: Input> Server<F, I> {
pub fn new(
name: String,
socket: PolledSocket<socket2::Socket>,
fb: F,
input: I,
) -> Server<F, I> {
#[expect(clippy::disallowed_methods)] // TODO
let (update_send, update_recv) = mpsc::channel(1);
Self {
socket,
fb,
input,
update_recv,
update_send,
name,
ctrl_left_pressed: false,
alt_left_pressed: false,
clipboard: String::new(),
}
}
pub fn updater(&mut self) -> Updater {
Updater(self.update_send.clone())
}
pub fn done(self) -> (F, I) {
(self.fb, self.input)
}
/// Runs the VNC server.
pub async fn run(&mut self) -> Result<(), Error> {
match self.run_internal().await {
Ok(()) => Ok(()),
Err(Error::Io(err)) if err.kind() == std::io::ErrorKind::ConnectionReset => Ok(()),
err => err,
}
}
async fn run_internal(&mut self) -> Result<(), Error> {
let socket = &mut self.socket;
socket
.write_all(rfb::ProtocolVersion(rfb::PROTOCOL_VERSION_33).as_bytes())
.await?;
let mut version = rfb::ProtocolVersion::new_zeroed();
socket.read_exact(version.as_mut_bytes()).await?;
if version.0 != rfb::PROTOCOL_VERSION_33 {
return Err(Error::UnsupportedVersion(version));
}
socket
.write_all(
rfb::Security33 {
padding: [0; 3],
security_type: rfb::SECURITY_TYPE_NONE,
}
.as_bytes(),
)
.await?;
let mut init = rfb::ClientInit::new_zeroed();
socket.read_exact(init.as_mut_bytes()).await?;
let mut fmt = rfb::PixelFormat {
bits_per_pixel: 32,
depth: 24,
big_endian_flag: 0,
true_color_flag: 1,
red_max: 255.into(),
green_max: 255.into(),
blue_max: 255.into(),
red_shift: 16,
green_shift: 8,
blue_shift: 0,
padding: [0; 3],
};
let name = self.name.as_bytes();
let (mut width, mut height) = self.fb.resolution();
socket
.write_all(
rfb::ServerInit {
framebuffer_width: width.into(),
framebuffer_height: height.into(),
server_pixel_format: fmt,
name_length: (name.len() as u32).into(),
}
.as_bytes(),
)
.await?;
socket.write_all(name).await?;
let mut ready_for_update = false;
let mut scancode_state = scancode::State::new();
loop {
let mut socket_ready = false;
let mut update_ready = false;
let mut message_type = 0u8;
let update_recv = &mut self.update_recv;
let mut update: OptionFuture<_> = ready_for_update
.then(|| update_recv.select_next_some())
.into();
futures::select! { // merge semantics
_ = update => update_ready = true,
r = socket.read(message_type.as_mut_bytes()).fuse() => {
if r? == 0 {
return Ok(())
}
socket_ready = true;
}
}
if ready_for_update && update_ready {
ready_for_update = false;
// Ensure the desktop size has not changed.
let (new_width, new_height) = self.fb.resolution();
if new_width != width || new_height != height {
// Send the new desktop size.
width = new_width;
height = new_height;
socket
.write_all(
rfb::FramebufferUpdate {
message_type: rfb::SC_MESSAGE_TYPE_FRAMEBUFFER_UPDATE,
padding: 0,
rectangle_count: 1.into(),
}
.as_bytes(),
)
.await?;
socket
.write_all(
rfb::Rectangle {
x: 0.into(),
y: 0.into(),
width: width.into(),
height: height.into(),
encoding_type: rfb::ENCODING_TYPE_DESKTOP_SIZE.into(),
}
.as_bytes(),
)
.await?;
} else {
// Send the update. Just update the whole framebuffer for now.
socket
.write_all(
rfb::FramebufferUpdate {
message_type: rfb::SC_MESSAGE_TYPE_FRAMEBUFFER_UPDATE,
padding: 0,
rectangle_count: 1.into(),
}
.as_bytes(),
)
.await?;
socket
.write_all(
rfb::Rectangle {
x: 0.into(),
y: 0.into(),
width: width.into(),
height: height.into(),
encoding_type: rfb::ENCODING_TYPE_RAW.into(),
}
.as_bytes(),
)
.await?;
let mut src_line = vec![0u32; width as usize];
let dest_depth = fmt.bits_per_pixel as usize / 8;
let shift_r = 24 - fmt.red_max.get().count_ones();
let shift_g = 16 - fmt.green_max.get().count_ones();
let shift_b = 8 - fmt.red_max.get().count_ones();
match dest_depth {
1 => {
let mut line = vec![0u8; width as usize];
for y in 0..height {
self.fb.read_line(y, src_line.as_mut_bytes());
for x in 0..width as usize {
let p = src_line[x];
let (r, g, b) = (p & 0xff0000, p & 0xff00, p & 0xff);
let p2 = r >> shift_r << fmt.red_shift
| g >> shift_g << fmt.green_shift
| b >> shift_b << fmt.blue_shift;
line[x] = p2 as u8;
}
socket.write_all(&line).await?;
}
}
2 => {
let mut line = vec![0u16; width as usize];
for y in 0..height {
self.fb.read_line(y, src_line.as_mut_bytes());
for x in 0..width as usize {
let p = src_line[x];
let (r, g, b) = (p & 0xff0000, p & 0xff00, p & 0xff);
let p2 = r >> shift_r << fmt.red_shift
| g >> shift_g << fmt.green_shift
| b >> shift_b << fmt.blue_shift;
line[x] = p2 as u16;
}
socket.write_all(line.as_bytes()).await?;
}
}
4 if shift_r == fmt.red_shift as u32
&& shift_g == fmt.green_shift as u32
&& shift_b == fmt.blue_shift as u32 =>
{
for y in 0..height {
self.fb.read_line(y, src_line.as_mut_bytes());
socket.write_all(src_line.as_bytes()).await?;
}
}
4 => {
let mut line = vec![0u32; width as usize];
for y in 0..height {
self.fb.read_line(y, src_line.as_mut_bytes());
for x in (width as usize & !3)..width as usize {
let p = src_line[x];
let (r, g, b) = (p & 0xff0000, p & 0xff00, p & 0xff);
let p2 = r >> shift_r << fmt.red_shift
| g >> shift_g << fmt.green_shift
| b >> shift_b << fmt.blue_shift;
line[x] = p2;
}
socket.write_all(line.as_bytes()).await?;
}
}
_ => unreachable!(),
}
}
}
if socket_ready {
match message_type {
rfb::CS_MESSAGE_SET_PIXEL_FORMAT => {
let mut input = rfb::SetPixelFormat::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
fmt = input.pixel_format;
}
rfb::CS_MESSAGE_SET_ENCODINGS => {
let mut input = rfb::SetEncodings::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
let mut encodings: Vec<zerocopy::U32<zerocopy::BE>> =
vec![0.into(); input.encoding_count.get().into()];
socket.read_exact(encodings.as_mut_bytes()).await?;
if !encodings.contains(&rfb::ENCODING_TYPE_DESKTOP_SIZE.into()) {
// Can't really operate without being able to change the desktop size dynamically.
return Err(Error::DesktopResizeNotSupported);
}
if encodings.contains(&rfb::ENCODING_TYPE_QEMU_EXTENDED_KEY_EVENT.into()) {
// Request qemu extended key events.
let mut msg = rfb::FramebufferUpdate {
message_type: rfb::SC_MESSAGE_TYPE_FRAMEBUFFER_UPDATE,
padding: 0,
rectangle_count: 1.into(),
}
.as_bytes()
.to_vec();
msg.extend_from_slice(
rfb::Rectangle {
x: 0.into(),
y: 0.into(),
width: 0.into(),
height: 0.into(),
encoding_type: rfb::ENCODING_TYPE_QEMU_EXTENDED_KEY_EVENT
.into(),
}
.as_bytes(),
);
socket.write_all(&msg).await?;
}
}
rfb::CS_MESSAGE_FRAMEBUFFER_UPDATE_REQUEST => {
let mut input = rfb::FramebufferUpdateRequest::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
ready_for_update = true;
}
rfb::CS_MESSAGE_KEY_EVENT => {
let mut input = rfb::KeyEvent::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
// RFB key events are in xkeysym format. Convert them to
// US keyboard scancodes and send them to the keyboard
// device.
//
// Ideally the VNC client would support the qemu
// extensions that provide the scancodes directly.
// intercept ctrl-alt-p to paste clipboard contents
const KEYSYM_CONTROL_LEFT: u16 = 0xffe3;
const KEYSYM_ALT_LEFT: u16 = 0xffe9;
match input.key.get() as u16 {
KEYSYM_CONTROL_LEFT => self.ctrl_left_pressed = input.down_flag == 1,
KEYSYM_ALT_LEFT => self.alt_left_pressed = input.down_flag == 1,
_ => {}
}
if self.ctrl_left_pressed
&& self.alt_left_pressed
&& input.key.get() == b'p'.into()
&& input.down_flag == 1
{
// release held modifier keys
self.ctrl_left_pressed = false;
self.alt_left_pressed = false;
for &scancode in &[KEYSYM_CONTROL_LEFT, KEYSYM_ALT_LEFT] {
let i = &mut self.input;
scancode_state.emit(scancode, false, |scancode, down| {
i.key(scancode, down);
});
}
// make sure that the clipboard only contains printable ASCII chars
if self.clipboard.chars().all(|c| (' '..='~').contains(&c)) {
for c in self.clipboard.as_bytes() {
let i = &mut self.input;
scancode_state.emit_ascii_char(*c, true, |scancode, down| {
i.key(scancode, down);
});
scancode_state.emit_ascii_char(*c, false, |scancode, down| {
i.key(scancode, down);
});
}
}
} else {
let i = &mut self.input;
scancode_state.emit(
input.key.get() as u16,
input.down_flag != 0,
|scancode, down| {
i.key(scancode, down);
},
);
}
}
rfb::CS_MESSAGE_POINTER_EVENT => {
let mut input = rfb::PointerEvent::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
//scale the mouse coordinates in the VNC itself
let mut x = 0;
let mut y = 0;
//only absolute positioning is required; relative is not
if (width > 1) && (height > 1) {
let mut x_val = input.x.get() as u32;
let mut y_val = input.y.get() as u32;
if x_val > width as u32 - 1 {
x_val = width as u32 - 1;
}
if y_val > height as u32 - 1 {
y_val = height as u32 - 1;
}
x = ((x_val * HID_MOUSE_MAX_ABS_VALUE) / (width as u32 - 1)) as u16;
y = ((y_val * HID_MOUSE_MAX_ABS_VALUE) / (height as u32 - 1)) as u16;
}
self.input.mouse(input.button_mask, x, y);
}
rfb::CS_MESSAGE_CLIENT_CUT_TEXT => {
let mut input = rfb::ClientCutText::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
let mut text_latin1 = vec![0; input.length.get() as usize];
socket.read_exact(&mut text_latin1).await?;
// Latin1 characters map to the first 256 characters of Unicode (roughly).
self.clipboard = text_latin1.iter().copied().map(|c| c as char).collect();
}
rfb::CS_MESSAGE_QEMU => {
let mut input = rfb::QemuMessageHeader::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[1..]).await?;
match input.submessage_type {
rfb::QEMU_MESSAGE_EXTENDED_KEY_EVENT => {
let mut input = rfb::QemuExtendedKeyEvent::new_zeroed();
socket.read_exact(&mut input.as_mut_bytes()[2..]).await?;
let mut scancode = input.keycode.get() as u16;
// An E0 prefix is sometimes encoded via the
// high bit on a single byte.
if scancode & 0xff80 == 0x80 {
scancode = 0xe000 | (scancode & 0x7f);
}
self.input.key(scancode, input.down_flag.get() != 0);
}
n => return Err(Error::UnknownQemuMessage(n)),
}
}
n => return Err(Error::UnknownMessage(n)),
}
}
}
}
}