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use crate::packets::ProtocolPacket;
use azalea_buf::McBufVarReadable;
use azalea_buf::{read_varint_async, BufReadError, Readable};
use azalea_crypto::Aes128CfbDec;
use flate2::read::ZlibDecoder;
use std::{
cell::Cell,
io::Read,
pin::Pin,
task::{Context, Poll},
};
use thiserror::Error;
use tokio::io::{AsyncRead, AsyncReadExt};
#[derive(Error, Debug)]
pub enum ReadPacketError {
#[error("Error reading packet {packet_name} ({packet_id}): {source}")]
Parse {
packet_id: u32,
packet_name: String,
source: BufReadError,
},
#[error("Unknown packet id {id} in state {state_name}")]
UnknownPacketId { state_name: String, id: u32 },
#[error("Couldn't read packet id")]
ReadPacketId { source: BufReadError },
#[error("Couldn't decompress packet")]
Decompress {
#[from]
source: DecompressionError,
},
#[error("Frame splitter error")]
FrameSplitter {
#[from]
source: FrameSplitterError,
},
#[error("Leftover data after reading packet {packet_name}: {data:?}")]
LeftoverData { data: Vec<u8>, packet_name: String },
}
#[derive(Error, Debug)]
pub enum FrameSplitterError {
#[error("Couldn't read VarInt length for packet. The previous packet may have been corrupted")]
LengthRead {
#[from]
source: BufReadError,
},
#[error("Io error")]
Io {
#[from]
source: std::io::Error,
},
}
async fn frame_splitter<R: ?Sized>(mut stream: &mut R) -> Result<Vec<u8>, FrameSplitterError>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
// Packet Length
let length = read_varint_async(&mut stream).await?;
let mut buf = vec![0; length as usize];
stream.read_exact(&mut buf).await?;
Ok(buf)
}
fn packet_decoder<P: ProtocolPacket>(stream: &mut impl Read) -> Result<P, ReadPacketError> {
// Packet ID
let packet_id = stream
.read_varint()
.map_err(|e| ReadPacketError::ReadPacketId { source: e })?;
P::read(packet_id.try_into().unwrap(), stream)
}
// this is always true in multiplayer, false in singleplayer
static VALIDATE_DECOMPRESSED: bool = true;
pub static MAXIMUM_UNCOMPRESSED_LENGTH: u32 = 2097152;
#[derive(Error, Debug)]
pub enum DecompressionError {
#[error("Couldn't read VarInt length for data")]
LengthReadError {
#[from]
source: BufReadError,
},
#[error("Io error")]
Io {
#[from]
source: std::io::Error,
},
#[error("Badly compressed packet - size of {size} is below server threshold of {threshold}")]
BelowCompressionThreshold { size: u32, threshold: u32 },
#[error(
"Badly compressed packet - size of {size} is larger than protocol maximum of {maximum}"
)]
AboveCompressionThreshold { size: u32, maximum: u32 },
}
fn compression_decoder(
stream: &mut impl Read,
compression_threshold: u32,
) -> Result<Vec<u8>, DecompressionError> {
// Data Length
let n = u32::var_read_from(stream)?;
if n == 0 {
// no data size, no compression
let mut buf = vec![];
stream.read_to_end(&mut buf)?;
return Ok(buf);
}
if VALIDATE_DECOMPRESSED {
if n < compression_threshold {
return Err(DecompressionError::BelowCompressionThreshold {
size: n,
threshold: compression_threshold,
});
}
if n > MAXIMUM_UNCOMPRESSED_LENGTH {
return Err(DecompressionError::AboveCompressionThreshold {
size: n,
maximum: MAXIMUM_UNCOMPRESSED_LENGTH,
});
}
}
let mut decoded_buf = vec![];
let mut decoder = ZlibDecoder::new(stream);
decoder.read_to_end(&mut decoded_buf)?;
Ok(decoded_buf)
}
struct EncryptedStream<'a, R>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
cipher: Cell<&'a mut Option<Aes128CfbDec>>,
stream: &'a mut Pin<&'a mut R>,
}
impl<R> AsyncRead for EncryptedStream<'_, R>
where
R: AsyncRead + Unpin + Send,
{
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut tokio::io::ReadBuf<'_>,
) -> Poll<std::io::Result<()>> {
// i hate this
let polled = self.as_mut().stream.as_mut().poll_read(cx, buf);
match polled {
Poll::Ready(r) => {
// if we don't check for the remaining then we decrypt big packets incorrectly
// (but only on linux and release mode for some reason LMAO)
if buf.remaining() == 0 {
if let Some(cipher) = self.as_mut().cipher.get_mut() {
azalea_crypto::decrypt_packet(cipher, buf.filled_mut());
}
}
match r {
Ok(()) => Poll::Ready(Ok(())),
Err(e) => panic!("{:?}", e),
}
}
Poll::Pending => Poll::Pending,
}
}
}
pub async fn read_packet<'a, P: ProtocolPacket, R>(
stream: &'a mut R,
compression_threshold: Option<u32>,
cipher: &mut Option<Aes128CfbDec>,
) -> Result<P, ReadPacketError>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send + std::marker::Sync,
{
// let start_time = std::time::Instant::now();
// println!("decrypting packet ({}ms)", start_time.elapsed().as_millis());
// if we were given a cipher, decrypt the packet
let mut encrypted_stream = EncryptedStream {
cipher: Cell::new(cipher),
stream: &mut Pin::new(stream),
};
// println!("splitting packet ({}ms)", start_time.elapsed().as_millis());
let mut buf = frame_splitter(&mut encrypted_stream).await?;
if let Some(compression_threshold) = compression_threshold {
// println!(
// "decompressing packet ({}ms)",
// start_time.elapsed().as_millis()
// );
buf = compression_decoder(&mut buf.as_slice(), compression_threshold)?;
}
// println!("decoding packet ({}ms)", start_time.elapsed().as_millis());
let packet = packet_decoder(&mut buf.as_slice())?;
// println!("decoded packet ({}ms)", start_time.elapsed().as_millis());
if !buf.is_empty() {}
Ok(packet)
}
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