diff options
Diffstat (limited to 'tvix/castore/src/nodes/symlink_target.rs')
| -rw-r--r-- | tvix/castore/src/nodes/symlink_target.rs | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/tvix/castore/src/nodes/symlink_target.rs b/tvix/castore/src/nodes/symlink_target.rs new file mode 100644 index 000000000000..e9a1a0bd05c2 --- /dev/null +++ b/tvix/castore/src/nodes/symlink_target.rs @@ -0,0 +1,223 @@ +use bstr::ByteSlice; +use std::fmt::{self, Debug, Display}; + +/// A wrapper type for symlink targets. +/// Internally uses a [bytes::Bytes], but disallows empty targets and those +/// containing null bytes. +#[repr(transparent)] +#[derive(Clone, PartialEq, Eq)] +pub struct SymlinkTarget { + inner: bytes::Bytes, +} + +/// The maximum length a symlink target can have. +/// Linux allows 4095 bytes here. +pub const MAX_TARGET_LEN: usize = 4095; + +impl AsRef<[u8]> for SymlinkTarget { + fn as_ref(&self) -> &[u8] { + self.inner.as_ref() + } +} + +impl From<SymlinkTarget> for bytes::Bytes { + fn from(value: SymlinkTarget) -> Self { + value.inner + } +} + +fn validate_symlink_target<B: AsRef<[u8]>>(symlink_target: B) -> Result<B, SymlinkTargetError> { + let v = symlink_target.as_ref(); + + if v.is_empty() { + return Err(SymlinkTargetError::Empty); + } + if v.len() > MAX_TARGET_LEN { + return Err(SymlinkTargetError::TooLong); + } + if v.contains(&0x00) { + return Err(SymlinkTargetError::Null); + } + + Ok(symlink_target) +} + +impl TryFrom<bytes::Bytes> for SymlinkTarget { + type Error = SymlinkTargetError; + + fn try_from(value: bytes::Bytes) -> Result<Self, Self::Error> { + if let Err(e) = validate_symlink_target(&value) { + return Err(SymlinkTargetError::Convert(value, Box::new(e))); + } + + Ok(Self { inner: value }) + } +} + +impl TryFrom<&'static [u8]> for SymlinkTarget { + type Error = SymlinkTargetError; + + fn try_from(value: &'static [u8]) -> Result<Self, Self::Error> { + if let Err(e) = validate_symlink_target(&value) { + return Err(SymlinkTargetError::Convert(value.into(), Box::new(e))); + } + + Ok(Self { + inner: bytes::Bytes::from_static(value), + }) + } +} + +impl TryFrom<&str> for SymlinkTarget { + type Error = SymlinkTargetError; + + fn try_from(value: &str) -> Result<Self, Self::Error> { + if let Err(e) = validate_symlink_target(value) { + return Err(SymlinkTargetError::Convert( + value.to_owned().into(), + Box::new(e), + )); + } + + Ok(Self { + inner: bytes::Bytes::copy_from_slice(value.as_bytes()), + }) + } +} + +impl Debug for SymlinkTarget { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + Debug::fmt(self.inner.as_bstr(), f) + } +} + +impl Display for SymlinkTarget { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + Display::fmt(self.inner.as_bstr(), f) + } +} + +/// Errors created when constructing / converting to [SymlinkTarget]. +#[derive(Debug, PartialEq, Eq, thiserror::Error)] +#[cfg_attr(test, derive(Clone))] +pub enum SymlinkTargetError { + #[error("cannot be empty")] + Empty, + #[error("cannot contain null bytes")] + Null, + #[error("cannot be over {} bytes long", MAX_TARGET_LEN)] + TooLong, + #[error("unable to convert '{:?}", .0.as_bstr())] + Convert(bytes::Bytes, Box<Self>), +} + +#[cfg(test)] +mod tests { + use bytes::Bytes; + use rstest::rstest; + + use super::validate_symlink_target; + use super::{SymlinkTarget, SymlinkTargetError}; + + #[rstest] + #[case::empty(b"", SymlinkTargetError::Empty)] + #[case::null(b"foo\0", SymlinkTargetError::Null)] + fn errors(#[case] v: &'static [u8], #[case] err: SymlinkTargetError) { + { + assert_eq!( + Err(err.clone()), + validate_symlink_target(v), + "validate_symlink_target must fail as expected" + ); + } + + let exp_err_v = Bytes::from_static(v); + + // Bytes + { + let v = Bytes::from_static(v); + assert_eq!( + Err(SymlinkTargetError::Convert( + exp_err_v.clone(), + Box::new(err.clone()) + )), + SymlinkTarget::try_from(v), + "conversion must fail as expected" + ); + } + // &[u8] + { + assert_eq!( + Err(SymlinkTargetError::Convert( + exp_err_v.clone(), + Box::new(err.clone()) + )), + SymlinkTarget::try_from(v), + "conversion must fail as expected" + ); + } + // &str, if this is valid UTF-8 + { + if let Ok(v) = std::str::from_utf8(v) { + assert_eq!( + Err(SymlinkTargetError::Convert( + exp_err_v.clone(), + Box::new(err.clone()) + )), + SymlinkTarget::try_from(v), + "conversion must fail as expected" + ); + } + } + } + + #[test] + fn error_toolong() { + assert_eq!( + Err(SymlinkTargetError::TooLong), + validate_symlink_target("X".repeat(5000).into_bytes().as_slice()) + ) + } + + #[rstest] + #[case::boring(b"aa")] + #[case::dot(b".")] + #[case::dotsandslashes(b"./..")] + #[case::dotdot(b"..")] + #[case::slashes(b"a/b")] + #[case::slashes_and_absolute(b"/a/b")] + #[case::invalid_utf8(b"\xc5\xc4\xd6")] + fn success(#[case] v: &'static [u8]) { + let exp = SymlinkTarget { inner: v.into() }; + + // Bytes + { + let v: Bytes = v.into(); + assert_eq!( + Ok(exp.clone()), + SymlinkTarget::try_from(v), + "conversion must succeed" + ) + } + + // &[u8] + { + assert_eq!( + Ok(exp.clone()), + SymlinkTarget::try_from(v), + "conversion must succeed" + ) + } + + // &str, if this is valid UTF-8 + { + if let Ok(v) = std::str::from_utf8(v) { + assert_eq!( + Ok(exp.clone()), + SymlinkTarget::try_from(v), + "conversion must succeed" + ) + } + } + } +} |