diff options
Diffstat (limited to 'tvix/nix-compat/src/wire/bytes/reader/mod.rs')
| -rw-r--r-- | tvix/nix-compat/src/wire/bytes/reader/mod.rs | 471 |
1 files changed, 471 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/wire/bytes/reader/mod.rs b/tvix/nix-compat/src/wire/bytes/reader/mod.rs new file mode 100644 index 000000000000..8d4eab78f370 --- /dev/null +++ b/tvix/nix-compat/src/wire/bytes/reader/mod.rs @@ -0,0 +1,471 @@ +use std::{ + io, + ops::{Bound, RangeBounds}, + pin::Pin, + task::{self, ready, Poll}, +}; +use tokio::io::{AsyncRead, ReadBuf}; + +use trailer::TrailerReader; +mod trailer; + +/// Reads a "bytes wire packet" from the underlying reader. +/// The format is the same as in [crate::wire::bytes::read_bytes], +/// however this structure provides a [AsyncRead] interface, +/// allowing to not having to pass around the entire payload in memory. +/// +/// After being constructed with the underlying reader and an allowed size, +/// subsequent requests to poll_read will return payload data until the end +/// of the packet is reached. +/// +/// Internally, it will first read over the size packet, filling payload_size, +/// ensuring it fits allowed_size, then return payload data. +/// +/// It will not return the final bytes before all padding has been successfully +/// consumed as well, but the full length of the reader must be consumed. +/// +/// In case of an error due to size constraints, or in case of not reading +/// all the way to the end (and getting a EOF), the underlying reader is no +/// longer usable and might return garbage. +pub struct BytesReader<R> { + state: State<R>, +} + +#[derive(Debug)] +enum State<R> { + Size { + reader: Option<R>, + /// Minimum length (inclusive) + user_len_min: u64, + /// Maximum length (inclusive) + user_len_max: u64, + filled: u8, + buf: [u8; 8], + }, + Body { + reader: Option<R>, + consumed: u64, + user_len: u64, + }, + Trailer(TrailerReader<R>), +} + +impl<R> BytesReader<R> +where + R: AsyncRead + Unpin, +{ + /// Constructs a new BytesReader, using the underlying passed reader. + pub fn new<S: RangeBounds<u64>>(reader: R, allowed_size: S) -> Self { + let user_len_min = match allowed_size.start_bound() { + Bound::Included(&n) => n, + Bound::Excluded(&n) => n.saturating_add(1), + Bound::Unbounded => 0, + }; + + let user_len_max = match allowed_size.end_bound() { + Bound::Included(&n) => n, + Bound::Excluded(&n) => n.checked_sub(1).unwrap(), + Bound::Unbounded => u64::MAX, + }; + + Self { + state: State::Size { + reader: Some(reader), + user_len_min, + user_len_max, + filled: 0, + buf: [0; 8], + }, + } + } + + /// Construct a new BytesReader with a known, and already-read size. + pub fn with_size(reader: R, size: u64) -> Self { + Self { + state: State::Body { + reader: Some(reader), + consumed: 0, + user_len: size, + }, + } + } +} + +impl<R: AsyncRead + Unpin> AsyncRead for BytesReader<R> { + fn poll_read( + self: Pin<&mut Self>, + cx: &mut task::Context, + buf: &mut ReadBuf, + ) -> Poll<io::Result<()>> { + let this = &mut self.get_mut().state; + + loop { + match this { + State::Size { + reader, + user_len_min, + user_len_max, + filled: 8, + buf, + } => { + let reader = reader.take().unwrap(); + + let data_len = u64::from_le_bytes(*buf); + if data_len < *user_len_min || data_len > *user_len_max { + return Err(io::Error::new(io::ErrorKind::InvalidData, "invalid size")) + .into(); + } + + *this = State::Body { + reader: Some(reader), + consumed: 0, + user_len: data_len, + }; + } + State::Size { + reader, + filled, + buf, + .. + } => { + let reader = reader.as_mut().unwrap(); + + let mut read_buf = ReadBuf::new(&mut buf[..]); + read_buf.advance(*filled as usize); + ready!(Pin::new(reader).poll_read(cx, &mut read_buf))?; + + let new_filled = read_buf.filled().len() as u8; + if *filled == new_filled { + return Err(io::ErrorKind::UnexpectedEof.into()).into(); + } + + *filled = new_filled; + } + State::Body { + reader, + consumed, + user_len, + } => { + let body_len = *user_len & !7; + let remaining = body_len - *consumed; + + let reader = if remaining == 0 { + let reader = reader.take().unwrap(); + let user_len = (*user_len & 7) as u8; + *this = State::Trailer(TrailerReader::new(reader, user_len)); + continue; + } else { + reader.as_mut().unwrap() + }; + + let mut bytes_read = 0; + ready!(with_limited(buf, remaining, |buf| { + let ret = Pin::new(reader).poll_read(cx, buf); + bytes_read = buf.initialized().len(); + ret + }))?; + + *consumed += bytes_read as u64; + + return if bytes_read != 0 { + Ok(()) + } else { + Err(io::ErrorKind::UnexpectedEof.into()) + } + .into(); + } + State::Trailer(reader) => { + return Pin::new(reader).poll_read(cx, buf); + } + } + } + } +} + +/// Make a limited version of `buf`, consisting only of up to `n` bytes of the unfilled section, and call `f` with it. +/// After `f` returns, we propagate the filled cursor advancement back to `buf`. +fn with_limited<R>(buf: &mut ReadBuf, n: u64, f: impl FnOnce(&mut ReadBuf) -> R) -> R { + let mut nbuf = buf.take(n.try_into().unwrap_or(usize::MAX)); + let ptr = nbuf.initialized().as_ptr(); + let ret = f(&mut nbuf); + + // SAFETY: `ReadBuf::take` only returns the *unfilled* section of `buf`, + // so anything filled is new, initialized data. + // + // We verify that `nbuf` still points to the same buffer, + // so we're sure it hasn't been swapped out. + unsafe { + // ensure our buffer hasn't been swapped out + assert_eq!(nbuf.initialized().as_ptr(), ptr); + + let n = nbuf.filled().len(); + buf.assume_init(n); + buf.advance(n); + } + + ret +} + +#[cfg(test)] +mod tests { + use std::time::Duration; + + use crate::wire::bytes::{padding_len, write_bytes}; + use hex_literal::hex; + use lazy_static::lazy_static; + use rstest::rstest; + use tokio::io::AsyncReadExt; + use tokio_test::{assert_err, io::Builder}; + + use super::*; + + /// The maximum length of bytes packets we're willing to accept in the test + /// cases. + const MAX_LEN: u64 = 1024; + + lazy_static! { + pub static ref LARGE_PAYLOAD: Vec<u8> = (0..255).collect::<Vec<u8>>().repeat(4 * 1024); + } + + /// Helper function, calling the (simpler) write_bytes with the payload. + /// We use this to create data we want to read from the wire. + async fn produce_packet_bytes(payload: &[u8]) -> Vec<u8> { + let mut exp = vec![]; + write_bytes(&mut exp, payload).await.unwrap(); + exp + } + + /// Read bytes packets of various length, and ensure read_to_end returns the + /// expected payload. + #[rstest] + #[case::empty(&[])] // empty bytes packet + #[case::size_1b(&[0xff])] // 1 bytes payload + #[case::size_8b(&hex!("0001020304050607"))] // 8 bytes payload (no padding) + #[case::size_9b( &hex!("000102030405060708"))] // 9 bytes payload (7 bytes padding) + #[case::size_1m(LARGE_PAYLOAD.as_slice())] // larger bytes packet + #[tokio::test] + async fn read_payload_correct(#[case] payload: &[u8]) { + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await) + .build(); + + let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64); + let mut buf = Vec::new(); + r.read_to_end(&mut buf).await.expect("must succeed"); + + assert_eq!(payload, &buf[..]); + } + + /// Read bytes packets of various length, and ensure read_to_end returns the + /// expected payload. + #[rstest] + #[case::empty(&[])] // empty bytes packet + #[case::size_1b(&[0xff])] // 1 bytes payload + #[case::size_8b(&hex!("0001020304050607"))] // 8 bytes payload (no padding) + #[case::size_9b( &hex!("000102030405060708"))] // 9 bytes payload (7 bytes padding) + #[case::size_1m(LARGE_PAYLOAD.as_slice())] // larger bytes packet + #[tokio::test] + async fn read_payload_correct_known(#[case] payload: &[u8]) { + let packet = produce_packet_bytes(payload).await; + + let size = u64::from_le_bytes({ + let mut buf = [0; 8]; + buf.copy_from_slice(&packet[..8]); + buf + }); + + let mut mock = Builder::new().read(&packet[8..]).build(); + + let mut r = BytesReader::with_size(&mut mock, size); + let mut buf = Vec::new(); + r.read_to_end(&mut buf).await.expect("must succeed"); + + assert_eq!(payload, &buf[..]); + } + + /// Fail if the bytes packet is larger than allowed + #[tokio::test] + async fn read_bigger_than_allowed_fail() { + let payload = LARGE_PAYLOAD.as_slice(); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[0..8]) // We stop reading after the size packet + .build(); + + let mut r = BytesReader::new(&mut mock, ..2048); + let mut buf = Vec::new(); + assert_err!(r.read_to_end(&mut buf).await); + } + + /// Fail if the bytes packet is smaller than allowed + #[tokio::test] + async fn read_smaller_than_allowed_fail() { + let payload = &[0x00, 0x01, 0x02]; + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[0..8]) // We stop reading after the size packet + .build(); + + let mut r = BytesReader::new(&mut mock, 1024..2048); + let mut buf = Vec::new(); + assert_err!(r.read_to_end(&mut buf).await); + } + + /// Fail if the padding is not all zeroes + #[tokio::test] + async fn read_fail_if_nonzero_padding() { + let payload = &[0x00, 0x01, 0x02]; + let mut packet_bytes = produce_packet_bytes(payload).await; + // Flip some bits in the padding + packet_bytes[12] = 0xff; + let mut mock = Builder::new().read(&packet_bytes).build(); // We stop reading after the faulty bit + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + let mut buf = Vec::new(); + + r.read_to_end(&mut buf).await.expect_err("must fail"); + } + + /// Start a 9 bytes payload packet, but have the underlying reader return + /// EOF in the middle of the size packet (after 4 bytes). + /// We should get an unexpected EOF error, already when trying to read the + /// first byte (of payload) + #[tokio::test] + async fn read_9b_eof_during_size() { + let payload = &hex!("FF0102030405060708"); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[..4]) + .build(); + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + let mut buf = [0u8; 1]; + + assert_eq!( + r.read_exact(&mut buf).await.expect_err("must fail").kind(), + std::io::ErrorKind::UnexpectedEof + ); + + assert_eq!(&[0], &buf, "buffer should stay empty"); + } + + /// Start a 9 bytes payload packet, but have the underlying reader return + /// EOF in the middle of the payload (4 bytes into the payload). + /// We should get an unexpected EOF error, after reading the first 4 bytes + /// (successfully). + #[tokio::test] + async fn read_9b_eof_during_payload() { + let payload = &hex!("FF0102030405060708"); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[..8 + 4]) + .build(); + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + let mut buf = [0; 9]; + + r.read_exact(&mut buf[..4]).await.expect("must succeed"); + + assert_eq!( + r.read_exact(&mut buf[4..=4]) + .await + .expect_err("must fail") + .kind(), + std::io::ErrorKind::UnexpectedEof + ); + } + + /// Start a 9 bytes payload packet, but don't supply the necessary padding. + /// This is expected to always fail before returning the final data. + #[rstest] + #[case::before_padding(8 + 9)] + #[case::during_padding(8 + 9 + 2)] + #[case::after_padding(8 + 9 + padding_len(9) as usize - 1)] + #[tokio::test] + async fn read_9b_eof_after_payload(#[case] offset: usize) { + let payload = &hex!("FF0102030405060708"); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[..offset]) + .build(); + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + + // read_exact of the payload *body* will succeed, but a subsequent read will + // return UnexpectedEof error. + assert_eq!(r.read_exact(&mut [0; 8]).await.unwrap(), 8); + assert_eq!( + r.read_exact(&mut [0]).await.unwrap_err().kind(), + std::io::ErrorKind::UnexpectedEof + ); + } + + /// Start a 9 bytes payload packet, but return an error after a certain position. + /// Ensure that error is propagated. + #[rstest] + #[case::during_size(4)] + #[case::before_payload(8)] + #[case::during_payload(8 + 4)] + #[case::before_padding(8 + 4)] + #[case::during_padding(8 + 9 + 2)] + #[tokio::test] + async fn propagate_error_from_reader(#[case] offset: usize) { + let payload = &hex!("FF0102030405060708"); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[..offset]) + .read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo")) + .build(); + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + let mut buf = Vec::new(); + + let err = r.read_to_end(&mut buf).await.expect_err("must fail"); + assert_eq!( + err.kind(), + std::io::ErrorKind::Other, + "error kind must match" + ); + + assert_eq!( + err.into_inner().unwrap().to_string(), + "foo", + "error payload must contain foo" + ); + } + + /// If there's an error right after the padding, we don't propagate it, as + /// we're done reading. We just return EOF. + #[tokio::test] + async fn no_error_after_eof() { + let payload = &hex!("FF0102030405060708"); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await) + .read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo")) + .build(); + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + let mut buf = Vec::new(); + + r.read_to_end(&mut buf).await.expect("must succeed"); + assert_eq!(buf.as_slice(), payload); + } + + /// Introduce various stalls in various places of the packet, to ensure we + /// handle these cases properly, too. + #[rstest] + #[case::beginning(0)] + #[case::before_payload(8)] + #[case::during_payload(8 + 4)] + #[case::before_padding(8 + 4)] + #[case::during_padding(8 + 9 + 2)] + #[tokio::test] + async fn read_payload_correct_pending(#[case] offset: usize) { + let payload = &hex!("FF0102030405060708"); + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[..offset]) + .wait(Duration::from_nanos(0)) + .read(&produce_packet_bytes(payload).await[offset..]) + .build(); + + let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64); + let mut buf = Vec::new(); + r.read_to_end(&mut buf).await.expect("must succeed"); + + assert_eq!(payload, &buf[..]); + } +} |