diff options
Diffstat (limited to 'tvix/nix-compat/src/wire/bytes')
| -rw-r--r-- | tvix/nix-compat/src/wire/bytes/mod.rs | 254 | ||||
| -rw-r--r-- | tvix/nix-compat/src/wire/bytes/reader.rs | 463 | ||||
| -rw-r--r-- | tvix/nix-compat/src/wire/bytes/writer.rs | 521 |
3 files changed, 1238 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/wire/bytes/mod.rs b/tvix/nix-compat/src/wire/bytes/mod.rs new file mode 100644 index 000000000000..9487536eb720 --- /dev/null +++ b/tvix/nix-compat/src/wire/bytes/mod.rs @@ -0,0 +1,254 @@ +use std::{ + io::{Error, ErrorKind}, + ops::RangeBounds, +}; +use tokio::io::{AsyncReadExt, AsyncWriteExt}; + +mod reader; +pub use reader::BytesReader; +mod writer; +pub use writer::BytesWriter; + +use super::primitive; + +/// 8 null bytes, used to write out padding. +const EMPTY_BYTES: &[u8; 8] = &[0u8; 8]; + +/// The length of the size field, in bytes is always 8. +const LEN_SIZE: usize = 8; + +#[allow(dead_code)] +/// Read a "bytes wire packet" from the AsyncRead. +/// Rejects reading more than `allowed_size` bytes of payload. +/// +/// The packet is made up of three parts: +/// - a length header, u64, LE-encoded +/// - the payload itself +/// - null bytes to the next 8 byte boundary +/// +/// Ensures the payload size fits into the `allowed_size` passed, +/// and that the padding is actual null bytes. +/// +/// On success, the returned `Vec<u8>` only contains the payload itself. +/// On failure (for example if a too large byte packet was sent), the reader +/// becomes unusable. +/// +/// This buffers the entire payload into memory, a streaming version will be +/// added later. +pub async fn read_bytes<R, S>(r: &mut R, allowed_size: S) -> std::io::Result<Vec<u8>> +where + R: AsyncReadExt + Unpin, + S: RangeBounds<u64>, +{ + // read the length field + let len = primitive::read_u64(r).await?; + + if !allowed_size.contains(&len) { + return Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "signalled package size not in allowed range", + )); + } + + // calculate the total length, including padding. + // byte packets are padded to 8 byte blocks each. + let padded_len = padding_len(len) as u64 + (len as u64); + let mut limited_reader = r.take(padded_len); + + let mut buf = Vec::new(); + + let s = limited_reader.read_to_end(&mut buf).await?; + + // make sure we got exactly the number of bytes, and not less. + if s as u64 != padded_len { + return Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "got less bytes than expected", + )); + } + + let (_content, padding) = buf.split_at(len as usize); + + // ensure the padding is all zeroes. + if !padding.iter().all(|e| *e == b'\0') { + return Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "padding is not all zeroes", + )); + } + + // return the data without the padding + buf.truncate(len as usize); + Ok(buf) +} + +/// Read a "bytes wire packet" of from the AsyncRead and tries to parse as string. +/// Internally uses [read_bytes]. +/// Rejects reading more than `allowed_size` bytes of payload. +pub async fn read_string<R, S>(r: &mut R, allowed_size: S) -> std::io::Result<String> +where + R: AsyncReadExt + Unpin, + S: RangeBounds<u64>, +{ + let bytes = read_bytes(r, allowed_size).await?; + String::from_utf8(bytes).map_err(|e| Error::new(ErrorKind::InvalidData, e)) +} + +/// Writes a "bytes wire packet" to a (hopefully buffered) [AsyncWriteExt]. +/// +/// Accepts anything implementing AsRef<[u8]> as payload. +/// +/// See [read_bytes] for a description of the format. +/// +/// Note: if performance matters to you, make sure your +/// [AsyncWriteExt] handle is buffered. This function is quite +/// write-intesive. +pub async fn write_bytes<W: AsyncWriteExt + Unpin, B: AsRef<[u8]>>( + w: &mut W, + b: B, +) -> std::io::Result<()> { + // write the size packet. + primitive::write_u64(w, b.as_ref().len() as u64).await?; + + // write the payload + w.write_all(b.as_ref()).await?; + + // write padding if needed + let padding_len = padding_len(b.as_ref().len() as u64) as usize; + if padding_len != 0 { + w.write_all(&EMPTY_BYTES[..padding_len]).await?; + } + Ok(()) +} + +/// Computes the number of bytes we should add to len (a length in +/// bytes) to be alined on 64 bits (8 bytes). +fn padding_len(len: u64) -> u8 { + let modulo = len % 8; + if modulo == 0 { + 0 + } else { + 8 - modulo as u8 + } +} + +/// Models the position inside a "bytes wire packet" that the reader or writer +/// is in. +/// It can be in three different stages, inside size, payload or padding fields. +/// The number tracks the number of bytes written inside the specific field. +/// There shall be no ambiguous states, at the end of a stage we immediately +/// move to the beginning of the next one: +/// - Size(LEN_SIZE) must be expressed as Payload(0) +/// - Payload(self.payload_len) must be expressed as Padding(0) +/// There's one exception - Size(LEN_SIZE) in the reader represents a failure +/// state we enter in case the allowed size doesn't match the allowed range. +/// +/// Padding(padding_len) means we're at the end of the bytes wire packet. +#[derive(Clone, Debug, PartialEq, Eq)] +enum BytesPacketPosition { + Size(usize), + Payload(u64), + Padding(usize), +} + +#[cfg(test)] +mod tests { + use tokio_test::{assert_ok, io::Builder}; + + use super::*; + use hex_literal::hex; + + /// The maximum length of bytes packets we're willing to accept in the test + /// cases. + const MAX_LEN: u64 = 1024; + + #[tokio::test] + async fn test_read_8_bytes() { + let mut mock = Builder::new() + .read(&8u64.to_le_bytes()) + .read(&12345678u64.to_le_bytes()) + .build(); + + assert_eq!( + &12345678u64.to_le_bytes(), + read_bytes(&mut mock, 0u64..MAX_LEN) + .await + .unwrap() + .as_slice() + ); + } + + #[tokio::test] + async fn test_read_9_bytes() { + let mut mock = Builder::new() + .read(&9u64.to_le_bytes()) + .read(&hex!("01020304050607080900000000000000")) + .build(); + + assert_eq!( + hex!("010203040506070809"), + read_bytes(&mut mock, 0u64..MAX_LEN) + .await + .unwrap() + .as_slice() + ); + } + + #[tokio::test] + async fn test_read_0_bytes() { + // A empty byte packet is essentially just the 0 length field. + // No data is read, and there's zero padding. + let mut mock = Builder::new().read(&0u64.to_le_bytes()).build(); + + assert_eq!( + hex!(""), + read_bytes(&mut mock, 0u64..MAX_LEN) + .await + .unwrap() + .as_slice() + ); + } + + #[tokio::test] + /// Ensure we don't read any further than the size field if the length + /// doesn't match the range we want to accept. + async fn test_read_reject_too_large() { + let mut mock = Builder::new().read(&100u64.to_le_bytes()).build(); + + read_bytes(&mut mock, 10..10) + .await + .expect_err("expect this to fail"); + } + + #[tokio::test] + async fn test_write_bytes_no_padding() { + let input = hex!("6478696f34657661"); + let len = input.len() as u64; + let mut mock = Builder::new() + .write(&len.to_le_bytes()) + .write(&input) + .build(); + assert_ok!(write_bytes(&mut mock, &input).await) + } + #[tokio::test] + async fn test_write_bytes_with_padding() { + let input = hex!("322e332e3137"); + let len = input.len() as u64; + let mut mock = Builder::new() + .write(&len.to_le_bytes()) + .write(&hex!("322e332e31370000")) + .build(); + assert_ok!(write_bytes(&mut mock, &input).await) + } + + #[tokio::test] + async fn test_write_string() { + let input = "Hello, World!"; + let len = input.len() as u64; + let mut mock = Builder::new() + .write(&len.to_le_bytes()) + .write(&hex!("48656c6c6f2c20576f726c6421000000")) + .build(); + assert_ok!(write_bytes(&mut mock, &input).await) + } +} diff --git a/tvix/nix-compat/src/wire/bytes/reader.rs b/tvix/nix-compat/src/wire/bytes/reader.rs new file mode 100644 index 000000000000..4c450b55db1a --- /dev/null +++ b/tvix/nix-compat/src/wire/bytes/reader.rs @@ -0,0 +1,463 @@ +use pin_project_lite::pin_project; +use std::{ + ops::RangeBounds, + task::{ready, Poll}, +}; +use tokio::io::AsyncRead; + +use super::{padding_len, BytesPacketPosition, LEN_SIZE}; + +pin_project! { + /// 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 only signal EOF (returning `Ok(())` without filling the buffer anymore) + /// when all padding has been successfully consumed too. + /// + /// This also means, it's important for a user to always read to the end, + /// and not just call read_exact - otherwise it might not skip over the + /// padding, and return garbage when reading the next packet. + /// + /// 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, S> + where + R: AsyncRead, + S: RangeBounds<u64>, + + { + #[pin] + inner: R, + + allowed_size: S, + payload_size: [u8; 8], + state: BytesPacketPosition, + } +} + +impl<R, S> BytesReader<R, S> +where + R: AsyncRead + Unpin, + S: RangeBounds<u64>, +{ + /// Constructs a new BytesReader, using the underlying passed reader. + pub fn new(r: R, allowed_size: S) -> Self { + Self { + inner: r, + allowed_size, + payload_size: [0; 8], + state: BytesPacketPosition::Size(0), + } + } +} +/// Returns an error if the passed usize is 0. +fn ensure_nonzero_bytes_read(bytes_read: usize) -> Result<usize, std::io::Error> { + if bytes_read == 0 { + Err(std::io::Error::new( + std::io::ErrorKind::UnexpectedEof, + "underlying reader returned EOF", + )) + } else { + Ok(bytes_read) + } +} + +impl<R, S> AsyncRead for BytesReader<R, S> +where + R: AsyncRead, + S: RangeBounds<u64>, +{ + fn poll_read( + self: std::pin::Pin<&mut Self>, + cx: &mut std::task::Context<'_>, + buf: &mut tokio::io::ReadBuf<'_>, + ) -> Poll<std::io::Result<()>> { + let mut this = self.project(); + + // Use a loop, so we can deal with (multiple) state transitions. + loop { + match *this.state { + BytesPacketPosition::Size(LEN_SIZE) => { + // used in case an invalid size was signalled. + Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "signalled package size not in allowed range", + ))? + } + BytesPacketPosition::Size(pos) => { + // try to read more of the size field. + // We wrap a BufRead around this.payload_size here, and set_filled. + let mut read_buf = tokio::io::ReadBuf::new(this.payload_size); + read_buf.advance(pos); + ready!(this.inner.as_mut().poll_read(cx, &mut read_buf))?; + + ensure_nonzero_bytes_read(read_buf.filled().len() - pos)?; + + let total_size_read = read_buf.filled().len(); + if total_size_read == LEN_SIZE { + // If the entire payload size was read, parse it + let payload_size = u64::from_le_bytes(*this.payload_size); + + if !this.allowed_size.contains(&payload_size) { + // If it's not in the allowed + // range, transition to failure mode + // `BytesPacketPosition::Size(LEN_SIZE)`, where only + // an error is returned. + *this.state = BytesPacketPosition::Size(LEN_SIZE) + } else if payload_size == 0 { + // If the payload size is 0, move on to reading padding directly. + *this.state = BytesPacketPosition::Padding(0) + } else { + // Else, transition to reading the payload. + *this.state = BytesPacketPosition::Payload(0) + } + } else { + // If we still need to read more of payload size, update + // our position in the state. + *this.state = BytesPacketPosition::Size(total_size_read) + } + } + BytesPacketPosition::Payload(pos) => { + let signalled_size = u64::from_le_bytes(*this.payload_size); + // We don't enter this match arm at all if we're expecting empty payload + debug_assert!(signalled_size > 0, "signalled size must be larger than 0"); + + // Read from the underlying reader into buf + // We cap the ReadBuf to the size of the payload, as we + // don't want to leak padding to the caller. + let bytes_read = ensure_nonzero_bytes_read({ + // Reducing these two u64 to usize on 32bits is fine - we + // only care about not reading too much, not too less. + let mut limited_buf = buf.take((signalled_size - pos) as usize); + ready!(this.inner.as_mut().poll_read(cx, &mut limited_buf))?; + limited_buf.filled().len() + })?; + + // SAFETY: we just did populate this, but through limited_buf. + unsafe { buf.assume_init(bytes_read) } + buf.advance(bytes_read); + + if pos + bytes_read as u64 == signalled_size { + // If we now read all payload, transition to padding + // state. + *this.state = BytesPacketPosition::Padding(0); + } else { + // if we didn't read everything yet, update our position + // in the state. + *this.state = BytesPacketPosition::Payload(pos + bytes_read as u64); + } + + // We return from poll_read here. + // This is important, as any error (or even Pending) from + // the underlying reader on the next read (be it padding or + // payload) would require us to roll back buf, as generally + // a AsyncRead::poll_read may not advance the buffer in case + // of a nonsuccessful read. + // It can't be misinterpreted as EOF, as we definitely *did* + // write something into buf if we come to here (we pass + // `ensure_nonzero_bytes_read`). + return Ok(()).into(); + } + BytesPacketPosition::Padding(pos) => { + // Consume whatever padding is left, ensuring it's all null + // bytes. Only return `Ready(Ok(()))` once we're past the + // padding (or in cases where polling the inner reader + // returns `Poll::Pending`). + let signalled_size = u64::from_le_bytes(*this.payload_size); + let total_padding_len = padding_len(signalled_size) as usize; + + let padding_len_remaining = total_padding_len - pos; + if padding_len_remaining != 0 { + // create a buffer only accepting the number of remaining padding bytes. + let mut buf = [0; 8]; + let mut padding_buf = tokio::io::ReadBuf::new(&mut buf); + let mut padding_buf = padding_buf.take(padding_len_remaining); + + // read into padding_buf. + ready!(this.inner.as_mut().poll_read(cx, &mut padding_buf))?; + let bytes_read = ensure_nonzero_bytes_read(padding_buf.filled().len())?; + + *this.state = BytesPacketPosition::Padding(pos + bytes_read); + + // ensure the bytes are not null bytes + if !padding_buf.filled().iter().all(|e| *e == b'\0') { + return Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "padding is not all zeroes", + )) + .into(); + } + + // if we still have padding to read, run the loop again. + continue; + } + // return EOF + return Ok(()).into(); + } + } + } + } +} + +#[cfg(test)] +mod tests { + use std::time::Duration; + + use crate::wire::bytes::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[..]); + } + + /// 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 return an error at various stages *after* the actual payload. + /// read_exact with a 9 bytes buffer is expected to succeed, but any further + /// read, as well as read_to_end are expected to fail. + #[rstest] + #[case::before_padding(8 + 9)] + #[case::during_padding(8 + 9 + 2)] + #[case::after_padding(8 + 9 + padding_len(9) as usize)] + #[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); + let mut buf = [0; 9]; + + // read_exact of the payload will succeed, but a subsequent read will + // return UnexpectedEof error. + r.read_exact(&mut buf).await.expect("should succeed"); + assert_eq!( + r.read_exact(&mut buf[4..=4]) + .await + .expect_err("must fail") + .kind(), + std::io::ErrorKind::UnexpectedEof + ); + + // read_to_end will fail. + let mut mock = Builder::new() + .read(&produce_packet_bytes(payload).await[..8 + payload.len()]) + .build(); + + let mut r = BytesReader::new(&mut mock, ..MAX_LEN); + let mut buf = Vec::new(); + assert_eq!( + r.read_to_end(&mut buf).await.expect_err("must fail").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[..]); + } +} diff --git a/tvix/nix-compat/src/wire/bytes/writer.rs b/tvix/nix-compat/src/wire/bytes/writer.rs new file mode 100644 index 000000000000..f278b8335f8f --- /dev/null +++ b/tvix/nix-compat/src/wire/bytes/writer.rs @@ -0,0 +1,521 @@ +use pin_project_lite::pin_project; +use std::task::{ready, Poll}; + +use tokio::io::AsyncWrite; + +use super::{padding_len, BytesPacketPosition, EMPTY_BYTES, LEN_SIZE}; + +pin_project! { + /// Writes a "bytes wire packet" to the underlying writer. + /// The format is the same as in [crate::wire::bytes::write_bytes], + /// however this structure provides a [AsyncWrite] interface, + /// allowing to not having to pass around the entire payload in memory. + /// + /// It internally takes care of writing (non-payload) framing (size and + /// padding). + /// + /// During construction, the expected payload size needs to be provided. + /// + /// After writing the payload to it, the user MUST call flush (or shutdown), + /// which will validate the written payload size to match, and write the + /// necessary padding. + /// + /// In case flush is not called at the end, invalid data might be sent + /// silently. + /// + /// The underlying writer returning `Ok(0)` is considered an EOF situation, + /// which is stronger than the "typically means the underlying object is no + /// longer able to accept bytes" interpretation from the docs. If such a + /// situation occurs, an error is returned. + /// + /// The struct holds three fields, the underlying writer, the (expected) + /// payload length, and an enum, tracking the state. + pub struct BytesWriter<W> + where + W: AsyncWrite, + { + #[pin] + inner: W, + payload_len: u64, + state: BytesPacketPosition, + } +} + +impl<W> BytesWriter<W> +where + W: AsyncWrite, +{ + /// Constructs a new BytesWriter, using the underlying passed writer. + pub fn new(w: W, payload_len: u64) -> Self { + Self { + inner: w, + payload_len, + state: BytesPacketPosition::Size(0), + } + } +} + +/// Returns an error if the passed usize is 0. +fn ensure_nonzero_bytes_written(bytes_written: usize) -> Result<usize, std::io::Error> { + if bytes_written == 0 { + Err(std::io::Error::new( + std::io::ErrorKind::WriteZero, + "underlying writer accepted 0 bytes", + )) + } else { + Ok(bytes_written) + } +} + +impl<W> AsyncWrite for BytesWriter<W> +where + W: AsyncWrite, +{ + fn poll_write( + self: std::pin::Pin<&mut Self>, + cx: &mut std::task::Context<'_>, + buf: &[u8], + ) -> Poll<Result<usize, std::io::Error>> { + // Use a loop, so we can deal with (multiple) state transitions. + let mut this = self.project(); + + loop { + match *this.state { + BytesPacketPosition::Size(LEN_SIZE) => unreachable!(), + BytesPacketPosition::Size(pos) => { + let size_field = &this.payload_len.to_le_bytes(); + + let bytes_written = ensure_nonzero_bytes_written(ready!(this + .inner + .as_mut() + .poll_write(cx, &size_field[pos..]))?)?; + + let new_pos = pos + bytes_written; + if new_pos == LEN_SIZE { + *this.state = BytesPacketPosition::Payload(0); + } else { + *this.state = BytesPacketPosition::Size(new_pos); + } + } + BytesPacketPosition::Payload(pos) => { + // Ensure we still have space for more payload + if pos + (buf.len() as u64) > *this.payload_len { + return Poll::Ready(Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "tried to write excess bytes", + ))); + } + let bytes_written = ready!(this.inner.as_mut().poll_write(cx, buf))?; + ensure_nonzero_bytes_written(bytes_written)?; + let new_pos = pos + (bytes_written as u64); + if new_pos == *this.payload_len { + *this.state = BytesPacketPosition::Padding(0) + } else { + *this.state = BytesPacketPosition::Payload(new_pos) + } + + return Poll::Ready(Ok(bytes_written)); + } + // If we're already in padding state, there should be no more payload left to write! + BytesPacketPosition::Padding(_pos) => { + return Poll::Ready(Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "tried to write excess bytes", + ))) + } + } + } + } + + fn poll_flush( + self: std::pin::Pin<&mut Self>, + cx: &mut std::task::Context<'_>, + ) -> Poll<Result<(), std::io::Error>> { + let mut this = self.project(); + + loop { + match *this.state { + BytesPacketPosition::Size(LEN_SIZE) => unreachable!(), + BytesPacketPosition::Size(pos) => { + // More bytes to write in the size field + let size_field = &this.payload_len.to_le_bytes()[..]; + let bytes_written = ensure_nonzero_bytes_written(ready!(this + .inner + .as_mut() + .poll_write(cx, &size_field[pos..]))?)?; + let new_pos = pos + bytes_written; + if new_pos == LEN_SIZE { + // Size field written, now ready to receive payload + *this.state = BytesPacketPosition::Payload(0); + } else { + *this.state = BytesPacketPosition::Size(new_pos); + } + } + BytesPacketPosition::Payload(_pos) => { + // If we're at position 0 and want to write 0 bytes of payload + // in total, we can transition to padding. + // Otherwise, break, as we're expecting more payload to + // be written. + if *this.payload_len == 0 { + *this.state = BytesPacketPosition::Padding(0); + } else { + break; + } + } + BytesPacketPosition::Padding(pos) => { + // Write remaining padding, if there is padding to write. + let total_padding_len = padding_len(*this.payload_len) as usize; + + if pos != total_padding_len { + let bytes_written = ensure_nonzero_bytes_written(ready!(this + .inner + .as_mut() + .poll_write(cx, &EMPTY_BYTES[pos..total_padding_len]))?)?; + *this.state = BytesPacketPosition::Padding(pos + bytes_written); + } else { + // everything written, break + break; + } + } + } + } + // Flush the underlying writer. + this.inner.as_mut().poll_flush(cx) + } + + fn poll_shutdown( + mut self: std::pin::Pin<&mut Self>, + cx: &mut std::task::Context<'_>, + ) -> Poll<Result<(), std::io::Error>> { + // Call flush. + ready!(self.as_mut().poll_flush(cx))?; + + let this = self.project(); + + // After a flush, being inside the padding state, and at the end of the padding + // is the only way to prevent a dirty shutdown. + if let BytesPacketPosition::Padding(pos) = *this.state { + let padding_len = padding_len(*this.payload_len) as usize; + if padding_len == pos { + // Shutdown the underlying writer + return this.inner.poll_shutdown(cx); + } + } + + // Shutdown the underlying writer, bubbling up any errors. + ready!(this.inner.poll_shutdown(cx))?; + + // return an error about unclean shutdown + Poll::Ready(Err(std::io::Error::new( + std::io::ErrorKind::BrokenPipe, + "unclean shutdown", + ))) + } +} + +#[cfg(test)] +mod tests { + use std::time::Duration; + + use crate::wire::bytes::write_bytes; + use hex_literal::hex; + use lazy_static::lazy_static; + use tokio::io::AsyncWriteExt; + use tokio_test::{assert_err, assert_ok, io::Builder}; + + use super::*; + + 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 see on the wire. + async fn produce_exp_bytes(payload: &[u8]) -> Vec<u8> { + let mut exp = vec![]; + write_bytes(&mut exp, payload).await.unwrap(); + exp + } + + /// Write an empty bytes packet. + #[tokio::test] + async fn write_empty() { + let payload = &[]; + let mut mock = Builder::new() + .write(&produce_exp_bytes(payload).await) + .build(); + + let mut w = BytesWriter::new(&mut mock, 0); + assert_ok!(w.write_all(&[]).await, "write all data"); + assert_ok!(w.flush().await, "flush"); + } + + /// Write an empty bytes packet, not calling write. + #[tokio::test] + async fn write_empty_only_flush() { + let payload = &[]; + let mut mock = Builder::new() + .write(&produce_exp_bytes(payload).await) + .build(); + + let mut w = BytesWriter::new(&mut mock, 0); + assert_ok!(w.flush().await, "flush"); + } + + /// Write an empty bytes packet, not calling write or flush, only shutdown. + #[tokio::test] + async fn write_empty_only_shutdown() { + let payload = &[]; + let mut mock = Builder::new() + .write(&produce_exp_bytes(payload).await) + .build(); + + let mut w = BytesWriter::new(&mut mock, 0); + assert_ok!(w.shutdown().await, "shutdown"); + } + + /// Write a 1 bytes packet + #[tokio::test] + async fn write_1b() { + let payload = &[0xff]; + + let mut mock = Builder::new() + .write(&produce_exp_bytes(payload).await) + .build(); + + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + assert_ok!(w.write_all(payload).await); + assert_ok!(w.flush().await, "flush"); + } + + /// Write a 8 bytes payload (no padding) + #[tokio::test] + async fn write_8b() { + let payload = &hex!("0001020304050607"); + + let mut mock = Builder::new() + .write(&produce_exp_bytes(payload).await) + .build(); + + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + assert_ok!(w.write_all(payload).await); + assert_ok!(w.flush().await, "flush"); + } + + /// Write a 9 bytes payload (7 bytes padding) + #[tokio::test] + async fn write_9b() { + let payload = &hex!("000102030405060708"); + + let mut mock = Builder::new() + .write(&produce_exp_bytes(payload).await) + .build(); + + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + assert_ok!(w.write_all(payload).await); + assert_ok!(w.flush().await, "flush"); + } + + /// Write a 9 bytes packet very granularly, with a lot of flushing in between, + /// and a shutdown at the end. + #[tokio::test] + async fn write_9b_flush() { + let payload = &hex!("000102030405060708"); + let exp_bytes = produce_exp_bytes(payload).await; + + let mut mock = Builder::new().write(&exp_bytes).build(); + + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + assert_ok!(w.flush().await); + + assert_ok!(w.write_all(&payload[..4]).await); + assert_ok!(w.flush().await); + + // empty write, cause why not + assert_ok!(w.write_all(&[]).await); + assert_ok!(w.flush().await); + + assert_ok!(w.write_all(&payload[4..]).await); + assert_ok!(w.flush().await); + assert_ok!(w.shutdown().await); + } + + /// Write a 9 bytes packet, but cause the sink to only accept half of the + /// padding, ensuring we correctly write (only) the rest of the padding later. + /// We write another 2 bytes of "bait", where a faulty implementation (pre + /// cl/11384) would put too many null bytes. + #[tokio::test] + async fn write_9b_write_padding_2steps() { + let payload = &hex!("000102030405060708"); + let exp_bytes = produce_exp_bytes(payload).await; + + let mut mock = Builder::new() + .write(&exp_bytes[0..8]) // size + .write(&exp_bytes[8..17]) // payload + .write(&exp_bytes[17..19]) // padding (2 of 7 bytes) + // insert a wait to prevent Mock from merging the two writes into one + .wait(Duration::from_nanos(1)) + .write(&hex!("0000000000ffff")) // padding (5 of 7 bytes, plus 2 bytes of "bait") + .build(); + + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + assert_ok!(w.write_all(&payload[..]).await); + assert_ok!(w.flush().await); + // Write bait + assert_ok!(mock.write_all(&hex!("ffff")).await); + } + + /// Write a larger bytes packet + #[tokio::test] + async fn write_1m() { + let payload = LARGE_PAYLOAD.as_slice(); + let exp_bytes = produce_exp_bytes(payload).await; + + let mut mock = Builder::new().write(&exp_bytes).build(); + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + + assert_ok!(w.write_all(payload).await); + assert_ok!(w.flush().await, "flush"); + } + + /// Not calling flush at the end, but shutdown is also ok if we wrote all + /// bytes we promised to write (as shutdown implies flush) + #[tokio::test] + async fn write_shutdown_without_flush_end() { + let payload = &[0xf0, 0xff]; + let exp_bytes = produce_exp_bytes(payload).await; + + let mut mock = Builder::new().write(&exp_bytes).build(); + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + + // call flush to write the size field + assert_ok!(w.flush().await); + + // write payload + assert_ok!(w.write_all(payload).await); + + // call shutdown + assert_ok!(w.shutdown().await); + } + + /// Writing more bytes than previously signalled should fail. + #[tokio::test] + async fn write_more_than_signalled_fail() { + let mut buf = Vec::new(); + let mut w = BytesWriter::new(&mut buf, 2); + + assert_err!(w.write_all(&hex!("000102")).await); + } + /// Writing more bytes than previously signalled, but in two parts + #[tokio::test] + async fn write_more_than_signalled_split_fail() { + let mut buf = Vec::new(); + let mut w = BytesWriter::new(&mut buf, 2); + + // write two bytes + assert_ok!(w.write_all(&hex!("0001")).await); + + // write the excess byte. + assert_err!(w.write_all(&hex!("02")).await); + } + + /// Writing more bytes than previously signalled, but flushing after the + /// signalled amount should fail. + #[tokio::test] + async fn write_more_than_signalled_flush_fail() { + let mut buf = Vec::new(); + let mut w = BytesWriter::new(&mut buf, 2); + + // write two bytes, then flush + assert_ok!(w.write_all(&hex!("0001")).await); + assert_ok!(w.flush().await); + + // write the excess byte. + assert_err!(w.write_all(&hex!("02")).await); + } + + /// Calling shutdown while not having written all bytes that were promised + /// returns an error. + /// Note there's still cases of silent corruption if the user doesn't call + /// shutdown explicitly (only drops). + #[tokio::test] + async fn premature_shutdown() { + let payload = &[0xf0, 0xff]; + let mut buf = Vec::new(); + let mut w = BytesWriter::new(&mut buf, payload.len() as u64); + + // call flush to write the size field + assert_ok!(w.flush().await); + + // write half of the payload (!) + assert_ok!(w.write_all(&payload[0..1]).await); + + // call shutdown, ensure it fails + assert_err!(w.shutdown().await); + } + + /// Write to a Writer that fails to write during the size packet (after 4 bytes). + /// Ensure this error gets propagated on the first call to write. + #[tokio::test] + async fn inner_writer_fail_during_size_firstwrite() { + let payload = &[0xf0]; + + let mut mock = Builder::new() + .write(&1u32.to_le_bytes()) + .write_error(std::io::Error::new(std::io::ErrorKind::Other, "๐ฟ")) + .build(); + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + + assert_err!(w.write_all(payload).await); + } + + /// Write to a Writer that fails to write during the size packet (after 4 bytes). + /// Ensure this error gets propagated during an initial flush + #[tokio::test] + async fn inner_writer_fail_during_size_initial_flush() { + let payload = &[0xf0]; + + let mut mock = Builder::new() + .write(&1u32.to_le_bytes()) + .write_error(std::io::Error::new(std::io::ErrorKind::Other, "๐ฟ")) + .build(); + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + + assert_err!(w.flush().await); + } + + /// Write to a writer that fails to write during the payload (after 9 bytes). + /// Ensure this error gets propagated when we're writing this byte. + #[tokio::test] + async fn inner_writer_fail_during_write() { + let payload = &hex!("f0ff"); + + let mut mock = Builder::new() + .write(&2u64.to_le_bytes()) + .write(&hex!("f0")) + .write_error(std::io::Error::new(std::io::ErrorKind::Other, "๐ฟ")) + .build(); + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + + assert_ok!(w.write(&hex!("f0")).await); + assert_err!(w.write(&hex!("ff")).await); + } + + /// Write to a writer that fails to write during the padding (after 10 bytes). + /// Ensure this error gets propagated during a flush. + #[tokio::test] + async fn inner_writer_fail_during_padding_flush() { + let payload = &hex!("f0"); + + let mut mock = Builder::new() + .write(&1u64.to_le_bytes()) + .write(&hex!("f0")) + .write(&hex!("00")) + .write_error(std::io::Error::new(std::io::ErrorKind::Other, "๐ฟ")) + .build(); + let mut w = BytesWriter::new(&mut mock, payload.len() as u64); + + assert_ok!(w.write(&hex!("f0")).await); + assert_err!(w.flush().await); + } +} |