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|
use std::{cell::Cell, pin::Pin};
use crate::{connect::PacketFlow, mc_buf::Readable, packets::ProtocolPacket};
use async_compression::tokio::bufread::ZlibDecoder;
use azalea_auth::encryption::Aes128Cfb;
use tokio::io::{AsyncRead, AsyncReadExt};
async fn frame_splitter<R: ?Sized>(mut stream: &mut R) -> Result<Vec<u8>, String>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
// Packet Length
let length_result = stream.read_varint().await;
match length_result {
Ok(length) => {
let mut buf = vec![0; length as usize];
stream
.read_exact(&mut buf)
.await
.map_err(|e| e.to_string())?;
Ok(buf)
}
Err(_) => Err("length wider than 21-bit".to_string()),
}
}
async fn packet_decoder<P: ProtocolPacket, R>(
stream: &mut R,
flow: &PacketFlow,
) -> Result<P, String>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
// Packet ID
let packet_id = stream.read_varint().await?;
Ok(P::read(packet_id.try_into().unwrap(), flow, stream).await?)
}
// this is always true in multiplayer, false in singleplayer
static VALIDATE_DECOMPRESSED: bool = true;
pub static MAXIMUM_UNCOMPRESSED_LENGTH: u32 = 8388608;
async fn compression_decoder<R>(
stream: &mut R,
compression_threshold: u32,
) -> Result<Vec<u8>, String>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
// Data Length
let n: u32 = stream.read_varint().await?.try_into().unwrap();
if n == 0 {
// no data size, no compression
let mut buf = vec![];
stream
.read_to_end(&mut buf)
.await
.map_err(|e| e.to_string())?;
return Ok(buf);
}
if VALIDATE_DECOMPRESSED {
if n < compression_threshold {
return Err(format!(
"Badly compressed packet - size of {} is below server threshold of {}",
n, compression_threshold
));
}
if n > MAXIMUM_UNCOMPRESSED_LENGTH {
return Err(format!(
"Badly compressed packet - size of {} is larger than protocol maximum of {}",
n, MAXIMUM_UNCOMPRESSED_LENGTH
));
}
}
let mut buf = vec![];
stream
.read_to_end(&mut buf)
.await
.map_err(|e| e.to_string())?;
let mut decoded_buf = vec![];
let mut decoder = ZlibDecoder::new(buf.as_slice());
decoder
.read_to_end(&mut decoded_buf)
.await
.map_err(|e| e.to_string())?;
Ok(decoded_buf)
}
struct EncryptedStream<'a, R>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
cipher: Cell<&'a mut Option<Aes128Cfb>>,
stream: &'a mut Pin<&'a mut R>,
}
impl<R> AsyncRead for EncryptedStream<'_, R>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
buf: &mut tokio::io::ReadBuf<'_>,
) -> std::task::Poll<std::io::Result<()>> {
// i hate this
let polled = self.as_mut().stream.as_mut().poll_read(cx, buf);
match polled {
std::task::Poll::Ready(r) => {
if let Some(cipher) = self.as_mut().cipher.get_mut() {
azalea_auth::encryption::decrypt_packet(cipher, buf.initialized_mut());
}
match r {
Ok(()) => std::task::Poll::Ready(Ok(())),
Err(e) => panic!("{:?}", e),
}
}
std::task::Poll::Pending => {
return std::task::Poll::Pending;
}
}
}
}
pub async fn read_packet<'a, P: ProtocolPacket, R>(
flow: &PacketFlow,
stream: &'a mut R,
compression_threshold: Option<u32>,
cipher: &mut Option<Aes128Cfb>,
) -> Result<P, String>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send + std::marker::Sync,
{
// if we were given a cipher, decrypt the packet
let mut encrypted_stream = EncryptedStream {
cipher: Cell::new(cipher),
stream: &mut Pin::new(stream),
};
let mut buf = frame_splitter(&mut encrypted_stream).await?;
if let Some(compression_threshold) = compression_threshold {
buf = compression_decoder(&mut buf.as_slice(), compression_threshold).await?;
}
let packet = packet_decoder(&mut buf.as_slice(), flow).await?;
Ok(packet)
}
|
