diff options
Diffstat (limited to 'tvix/nix-compat/src/nar/reader/async')
| -rw-r--r-- | tvix/nix-compat/src/nar/reader/async/mod.rs | 166 | ||||
| -rw-r--r-- | tvix/nix-compat/src/nar/reader/async/read.rs | 69 | ||||
| -rw-r--r-- | tvix/nix-compat/src/nar/reader/async/test.rs | 310 |
3 files changed, 545 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/nar/reader/async/mod.rs b/tvix/nix-compat/src/nar/reader/async/mod.rs new file mode 100644 index 000000000000..aaf00faf4441 --- /dev/null +++ b/tvix/nix-compat/src/nar/reader/async/mod.rs @@ -0,0 +1,166 @@ +use std::{ + pin::Pin, + task::{self, Poll}, +}; + +use tokio::io::{self, AsyncBufRead, AsyncRead, ErrorKind::InvalidData}; + +// Required reading for understanding this module. +use crate::{ + nar::{self, wire::PadPar}, + wire::{self, BytesReader}, +}; + +mod read; +#[cfg(test)] +mod test; + +pub type Reader<'a> = dyn AsyncBufRead + Unpin + Send + 'a; + +/// Start reading a NAR file from `reader`. +pub async fn open<'a, 'r>(reader: &'a mut Reader<'r>) -> io::Result<Node<'a, 'r>> { + read::token(reader, &nar::wire::TOK_NAR).await?; + Node::new(reader).await +} + +pub enum Node<'a, 'r: 'a> { + Symlink { + target: Vec<u8>, + }, + File { + executable: bool, + reader: FileReader<'a, 'r>, + }, + Directory(DirReader<'a, 'r>), +} + +impl<'a, 'r: 'a> Node<'a, 'r> { + /// Start reading a [Node], matching the next [wire::Node]. + /// + /// Reading the terminating [wire::TOK_PAR] is done immediately for [Node::Symlink], + /// but is otherwise left to [DirReader] or [BytesReader]. + async fn new(reader: &'a mut Reader<'r>) -> io::Result<Self> { + Ok(match read::tag(reader).await? { + nar::wire::Node::Sym => { + let target = wire::read_bytes(reader, 1..=nar::wire::MAX_TARGET_LEN).await?; + + if target.contains(&0) { + return Err(InvalidData.into()); + } + + read::token(reader, &nar::wire::TOK_PAR).await?; + + Node::Symlink { target } + } + tag @ (nar::wire::Node::Reg | nar::wire::Node::Exe) => Node::File { + executable: tag == nar::wire::Node::Exe, + reader: FileReader { + inner: BytesReader::new_internal(reader, ..).await?, + }, + }, + nar::wire::Node::Dir => Node::Directory(DirReader::new(reader)), + }) + } +} + +/// File contents, readable through the [AsyncRead] trait. +/// +/// It comes with some caveats: +/// * You must always read the entire file, unless you intend to abandon the entire archive reader. +/// * You must abandon the entire archive reader upon the first error. +/// +/// It's fine to read exactly `reader.len()` bytes without ever seeing an explicit EOF. +pub struct FileReader<'a, 'r> { + inner: BytesReader<&'a mut Reader<'r>, PadPar>, +} + +impl<'a, 'r> FileReader<'a, 'r> { + pub fn is_empty(&self) -> bool { + self.len() == 0 + } + + pub fn len(&self) -> u64 { + self.inner.len() + } +} + +impl<'a, 'r> AsyncRead for FileReader<'a, 'r> { + fn poll_read( + self: Pin<&mut Self>, + cx: &mut task::Context, + buf: &mut io::ReadBuf, + ) -> Poll<io::Result<()>> { + Pin::new(&mut self.get_mut().inner).poll_read(cx, buf) + } +} + +/// A directory iterator, yielding a sequence of [Node]s. +/// It must be fully consumed before reading further from the [DirReader] that produced it, if any. +pub struct DirReader<'a, 'r> { + reader: &'a mut Reader<'r>, + /// Previous directory entry name. + /// We have to hang onto this to enforce name monotonicity. + prev_name: Option<Vec<u8>>, +} + +pub struct Entry<'a, 'r> { + pub name: Vec<u8>, + pub node: Node<'a, 'r>, +} + +impl<'a, 'r> DirReader<'a, 'r> { + fn new(reader: &'a mut Reader<'r>) -> Self { + Self { + reader, + prev_name: None, + } + } + + /// Read the next [Entry] from the directory. + /// + /// We explicitly don't implement [Iterator], since treating this as + /// a regular Rust iterator will surely lead you astray. + /// + /// * You must always consume the entire iterator, unless you abandon the entire archive reader. + /// * You must abandon the entire archive reader on the first error. + /// * You must abandon the directory reader upon the first [None]. + /// * Even if you know the amount of elements up front, you must keep reading until you encounter [None]. + pub async fn next(&mut self) -> io::Result<Option<Entry<'_, 'r>>> { + // COME FROM the previous iteration: if we've already read an entry, + // read its terminating TOK_PAR here. + if self.prev_name.is_some() { + read::token(self.reader, &nar::wire::TOK_PAR).await?; + } + + if let nar::wire::Entry::None = read::tag(self.reader).await? { + return Ok(None); + } + + let name = wire::read_bytes(self.reader, 1..=nar::wire::MAX_NAME_LEN).await?; + + if name.contains(&0) || name.contains(&b'/') || name == b"." || name == b".." { + return Err(InvalidData.into()); + } + + // Enforce strict monotonicity of directory entry names. + match &mut self.prev_name { + None => { + self.prev_name = Some(name.clone()); + } + Some(prev_name) => { + if *prev_name >= name { + return Err(InvalidData.into()); + } + + name[..].clone_into(prev_name); + } + } + + read::token(self.reader, &nar::wire::TOK_NOD).await?; + + Ok(Some(Entry { + name, + node: Node::new(self.reader).await?, + })) + } +} diff --git a/tvix/nix-compat/src/nar/reader/async/read.rs b/tvix/nix-compat/src/nar/reader/async/read.rs new file mode 100644 index 000000000000..2adf894922c5 --- /dev/null +++ b/tvix/nix-compat/src/nar/reader/async/read.rs @@ -0,0 +1,69 @@ +use tokio::io::{ + self, AsyncReadExt, + ErrorKind::{InvalidData, UnexpectedEof}, +}; + +use crate::nar::wire::Tag; + +use super::Reader; + +/// Consume a known token from the reader. +pub async fn token<const N: usize>(reader: &mut Reader<'_>, token: &[u8; N]) -> io::Result<()> { + let mut buf = [0u8; N]; + + // This implements something similar to [AsyncReadExt::read_exact], but verifies that + // the input data matches the token while we read it. These two slices respectively + // represent the remaining token to be verified, and the remaining input buffer. + let mut token = &token[..]; + let mut buf = &mut buf[..]; + + while !token.is_empty() { + match reader.read(buf).await? { + 0 => { + return Err(UnexpectedEof.into()); + } + n => { + let (t, b); + (t, token) = token.split_at(n); + (b, buf) = buf.split_at_mut(n); + + if t != b { + return Err(InvalidData.into()); + } + } + } + } + + Ok(()) +} + +/// Consume a [Tag] from the reader. +pub async fn tag<T: Tag>(reader: &mut Reader<'_>) -> io::Result<T> { + let mut buf = T::make_buf(); + let buf = buf.as_mut(); + + // first read the known minimum length… + reader.read_exact(&mut buf[..T::MIN]).await?; + + // then decide which tag we're expecting + let tag = T::from_u8(buf[T::OFF]).ok_or(InvalidData)?; + let (head, tail) = tag.as_bytes().split_at(T::MIN); + + // make sure what we've read so far is valid + if buf[..T::MIN] != *head { + return Err(InvalidData.into()); + } + + // …then read the rest, if any + if !tail.is_empty() { + let rest = tail.len(); + reader.read_exact(&mut buf[..rest]).await?; + + // and make sure it's what we expect + if buf[..rest] != *tail { + return Err(InvalidData.into()); + } + } + + Ok(tag) +} diff --git a/tvix/nix-compat/src/nar/reader/async/test.rs b/tvix/nix-compat/src/nar/reader/async/test.rs new file mode 100644 index 000000000000..58bb651fca21 --- /dev/null +++ b/tvix/nix-compat/src/nar/reader/async/test.rs @@ -0,0 +1,310 @@ +use tokio::io::AsyncReadExt; + +mod nar { + pub use crate::nar::reader::r#async as reader; +} + +#[tokio::test] +async fn symlink() { + let mut f = std::io::Cursor::new(include_bytes!("../../tests/symlink.nar")); + let node = nar::reader::open(&mut f).await.unwrap(); + + match node { + nar::reader::Node::Symlink { target } => { + assert_eq!( + &b"/nix/store/somewhereelse"[..], + &target, + "target must match" + ); + } + _ => panic!("unexpected type"), + } +} + +#[tokio::test] +async fn file() { + let mut f = std::io::Cursor::new(include_bytes!("../../tests/helloworld.nar")); + let node = nar::reader::open(&mut f).await.unwrap(); + + match node { + nar::reader::Node::File { + executable, + mut reader, + } => { + assert!(!executable); + let mut buf = vec![]; + reader + .read_to_end(&mut buf) + .await + .expect("read must succeed"); + assert_eq!(&b"Hello World!"[..], &buf); + } + _ => panic!("unexpected type"), + } +} + +#[tokio::test] +async fn complicated() { + let mut f = std::io::Cursor::new(include_bytes!("../../tests/complicated.nar")); + let node = nar::reader::open(&mut f).await.unwrap(); + + match node { + nar::reader::Node::Directory(mut dir_reader) => { + // first entry is .keep, an empty regular file. + must_read_file( + ".keep", + dir_reader + .next() + .await + .expect("next must succeed") + .expect("must be some"), + ) + .await; + + // second entry is aa, a symlink to /nix/store/somewhereelse + must_be_symlink( + "aa", + "/nix/store/somewhereelse", + dir_reader + .next() + .await + .expect("next must be some") + .expect("must be some"), + ); + + { + // third entry is a directory called "keep" + let entry = dir_reader + .next() + .await + .expect("next must be some") + .expect("must be some"); + + assert_eq!(&b"keep"[..], &entry.name); + + match entry.node { + nar::reader::Node::Directory(mut subdir_reader) => { + { + // first entry is .keep, an empty regular file. + let entry = subdir_reader + .next() + .await + .expect("next must succeed") + .expect("must be some"); + + must_read_file(".keep", entry).await; + } + + // we must read the None + assert!( + subdir_reader + .next() + .await + .expect("next must succeed") + .is_none(), + "keep directory contains only .keep" + ); + } + _ => panic!("unexpected type for keep/.keep"), + } + }; + + // reading more entries yields None (and we actually must read until this) + assert!(dir_reader.next().await.expect("must succeed").is_none()); + } + _ => panic!("unexpected type"), + } +} + +#[tokio::test] +#[should_panic] +#[ignore = "TODO: async poisoning"] +async fn file_read_abandoned() { + let mut f = std::io::Cursor::new(include_bytes!("../../tests/complicated.nar")); + let node = nar::reader::open(&mut f).await.unwrap(); + + match node { + nar::reader::Node::Directory(mut dir_reader) => { + // first entry is .keep, an empty regular file. + { + let entry = dir_reader + .next() + .await + .expect("next must succeed") + .expect("must be some"); + + assert_eq!(&b".keep"[..], &entry.name); + // don't bother to finish reading it. + }; + + // this should panic (not return an error), because we are meant to abandon the archive reader now. + assert!(dir_reader.next().await.expect("must succeed").is_none()); + } + _ => panic!("unexpected type"), + } +} + +#[tokio::test] +#[should_panic] +#[ignore = "TODO: async poisoning"] +async fn dir_read_abandoned() { + let mut f = std::io::Cursor::new(include_bytes!("../../tests/complicated.nar")); + let node = nar::reader::open(&mut f).await.unwrap(); + + match node { + nar::reader::Node::Directory(mut dir_reader) => { + // first entry is .keep, an empty regular file. + must_read_file( + ".keep", + dir_reader + .next() + .await + .expect("next must succeed") + .expect("must be some"), + ) + .await; + + // second entry is aa, a symlink to /nix/store/somewhereelse + must_be_symlink( + "aa", + "/nix/store/somewhereelse", + dir_reader + .next() + .await + .expect("next must be some") + .expect("must be some"), + ); + + { + // third entry is a directory called "keep" + let entry = dir_reader + .next() + .await + .expect("next must be some") + .expect("must be some"); + + assert_eq!(&b"keep"[..], &entry.name); + + match entry.node { + nar::reader::Node::Directory(_) => { + // don't finish using it, which poisons the archive reader + } + _ => panic!("unexpected type for keep/.keep"), + } + }; + + // this should panic, because we didn't finish reading the child subdirectory + assert!(dir_reader.next().await.expect("must succeed").is_none()); + } + _ => panic!("unexpected type"), + } +} + +#[tokio::test] +#[should_panic] +#[ignore = "TODO: async poisoning"] +async fn dir_read_after_none() { + let mut f = std::io::Cursor::new(include_bytes!("../../tests/complicated.nar")); + let node = nar::reader::open(&mut f).await.unwrap(); + + match node { + nar::reader::Node::Directory(mut dir_reader) => { + // first entry is .keep, an empty regular file. + must_read_file( + ".keep", + dir_reader + .next() + .await + .expect("next must succeed") + .expect("must be some"), + ) + .await; + + // second entry is aa, a symlink to /nix/store/somewhereelse + must_be_symlink( + "aa", + "/nix/store/somewhereelse", + dir_reader + .next() + .await + .expect("next must be some") + .expect("must be some"), + ); + + { + // third entry is a directory called "keep" + let entry = dir_reader + .next() + .await + .expect("next must be some") + .expect("must be some"); + + assert_eq!(&b"keep"[..], &entry.name); + + match entry.node { + nar::reader::Node::Directory(mut subdir_reader) => { + // first entry is .keep, an empty regular file. + must_read_file( + ".keep", + subdir_reader + .next() + .await + .expect("next must succeed") + .expect("must be some"), + ) + .await; + + // we must read the None + assert!( + subdir_reader + .next() + .await + .expect("next must succeed") + .is_none(), + "keep directory contains only .keep" + ); + } + _ => panic!("unexpected type for keep/.keep"), + } + }; + + // reading more entries yields None (and we actually must read until this) + assert!(dir_reader.next().await.expect("must succeed").is_none()); + + // this should panic, because we already got a none so we're meant to stop. + dir_reader.next().await.unwrap(); + unreachable!() + } + _ => panic!("unexpected type"), + } +} + +async fn must_read_file(name: &'static str, entry: nar::reader::Entry<'_, '_>) { + assert_eq!(name.as_bytes(), &entry.name); + + match entry.node { + nar::reader::Node::File { + executable, + mut reader, + } => { + assert!(!executable); + assert_eq!(reader.read(&mut [0]).await.unwrap(), 0); + } + _ => panic!("unexpected type for {}", name), + } +} + +fn must_be_symlink( + name: &'static str, + exp_target: &'static str, + entry: nar::reader::Entry<'_, '_>, +) { + assert_eq!(name.as_bytes(), &entry.name); + + match entry.node { + nar::reader::Node::Symlink { target } => { + assert_eq!(exp_target.as_bytes(), &target); + } + _ => panic!("unexpected type for {}", name), + } +} |