diff options
Diffstat (limited to 'tvix/nix-compat/src/store_path/mod.rs')
| -rw-r--r-- | tvix/nix-compat/src/store_path/mod.rs | 430 |
1 files changed, 430 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/store_path/mod.rs b/tvix/nix-compat/src/store_path/mod.rs new file mode 100644 index 000000000000..e23002bfb97e --- /dev/null +++ b/tvix/nix-compat/src/store_path/mod.rs @@ -0,0 +1,430 @@ +use crate::nixbase32; +use data_encoding::{DecodeError, BASE64}; +use std::{ + fmt, + path::PathBuf, + str::{self, FromStr}, +}; +use thiserror; + +#[cfg(target_family = "unix")] +use std::os::unix::ffi::OsStringExt; + +mod utils; + +pub use utils::*; + +pub const DIGEST_SIZE: usize = 20; +pub const ENCODED_DIGEST_SIZE: usize = nixbase32::encode_len(DIGEST_SIZE); + +// The store dir prefix, without trailing slash. +// That's usually where the Nix store is mounted at. +pub const STORE_DIR: &str = "/nix/store"; +pub const STORE_DIR_WITH_SLASH: &str = "/nix/store/"; + +/// Errors that can occur when parsing a literal store path +#[derive(Debug, PartialEq, Eq, thiserror::Error)] +pub enum Error { + #[error("Dash is missing between hash and name")] + MissingDash, + #[error("Hash encoding is invalid: {0}")] + InvalidHashEncoding(DecodeError), + #[error("Invalid length")] + InvalidLength, + #[error( + "Invalid name: \"{}\", character at position {} is invalid", + std::str::from_utf8(.0).unwrap_or(&BASE64.encode(.0)), + .1, + )] + InvalidName(Vec<u8>, u8), + #[error("Tried to parse an absolute path which was missing the store dir prefix.")] + MissingStoreDir, +} + +/// Represents a path in the Nix store (a direct child of [STORE_DIR]). +/// +/// It consists of a digest (20 bytes), and a name, which is a string. +/// The name may only contain ASCII alphanumeric, or one of the following +/// characters: `-`, `_`, `.`, `+`, `?`, `=`. +/// The name is usually used to describe the pname and version of a package. +/// Derivation paths can also be represented as store paths, their names just +/// end with the `.drv` prefix. +/// +/// A [StorePath] does not encode any additional subpath "inside" the store +/// path. +#[derive(Clone, Debug, PartialEq, Eq, Hash)] +pub struct StorePath { + digest: [u8; DIGEST_SIZE], + name: String, +} + +impl StorePath { + pub fn digest(&self) -> &[u8; DIGEST_SIZE] { + &self.digest + } + + pub fn name(&self) -> &str { + self.name.as_ref() + } +} + +impl PartialOrd for StorePath { + fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> { + Some(self.cmp(other)) + } +} + +impl Ord for StorePath { + fn cmp(&self, other: &Self) -> std::cmp::Ordering { + self.digest.cmp(&other.digest) + } +} + +impl FromStr for StorePath { + type Err = Error; + + /// Construct a [StorePath] by passing the `$digest-$name` string + /// that comes after [STORE_DIR_WITH_SLASH]. + fn from_str(s: &str) -> Result<Self, Self::Err> { + Self::from_bytes(s.as_bytes()) + } +} + +impl StorePath { + /// Construct a [StorePath] by passing the `$digest-$name` string + /// that comes after [STORE_DIR_WITH_SLASH]. + pub fn from_bytes(s: &[u8]) -> Result<StorePath, Error> { + Ok(StorePathRef::from_bytes(s)?.to_owned()) + } + + /// Decompose a string into a [StorePath] and a [PathBuf] containing the + /// rest of the path, or an error. + #[cfg(target_family = "unix")] + pub fn from_absolute_path_full(s: &str) -> Result<(StorePath, PathBuf), Error> { + // strip [STORE_DIR_WITH_SLASH] from s + match s.strip_prefix(STORE_DIR_WITH_SLASH) { + None => Err(Error::MissingStoreDir), + Some(rest) => { + // put rest in a PathBuf + let mut p = PathBuf::new(); + p.push(rest); + + let mut it = p.components(); + + // The first component of the rest must be parse-able as a [StorePath] + if let Some(first_component) = it.next() { + // convert first component to StorePath + let first_component_bytes = first_component.as_os_str().to_owned().into_vec(); + let store_path = StorePath::from_bytes(&first_component_bytes)?; + // collect rest + let rest_buf: PathBuf = it.collect(); + Ok((store_path, rest_buf)) + } else { + Err(Error::InvalidLength) // Well, or missing "/"? + } + } + } + } + + /// Returns an absolute store path string. + /// That is just the string representation, prefixed with the store prefix + /// ([STORE_DIR_WITH_SLASH]), + pub fn to_absolute_path(&self) -> String { + let sp_ref: StorePathRef = self.into(); + sp_ref.to_absolute_path() + } +} + +/// Like [StorePath], but without a heap allocation for the name. +/// Used by [StorePath] for parsing. +/// +#[derive(Debug, Eq, PartialEq)] +pub struct StorePathRef<'a> { + digest: [u8; DIGEST_SIZE], + name: &'a str, +} + +impl<'a> From<&'a StorePath> for StorePathRef<'a> { + fn from(&StorePath { digest, ref name }: &'a StorePath) -> Self { + StorePathRef { + digest, + name: name.as_ref(), + } + } +} + +impl<'a> StorePathRef<'a> { + pub fn digest(&self) -> &[u8; DIGEST_SIZE] { + &self.digest + } + + pub fn name(&self) -> &'a str { + self.name + } + + pub fn to_owned(&self) -> StorePath { + StorePath { + digest: self.digest, + name: self.name.to_owned(), + } + } + + /// Construct a [StorePathRef] from a name and digest. + pub fn from_name_and_digest(name: &'a str, digest: &[u8]) -> Result<Self, Error> { + Ok(Self { + name: validate_name(name.as_bytes())?, + digest: digest.try_into().map_err(|_| Error::InvalidLength)?, + }) + } + + /// Construct a [StorePathRef] from an absolute store path string. + /// This is equivalent to calling [StorePathRef::from_bytes], but stripping + /// the [STORE_DIR_WITH_SLASH] prefix before. + pub fn from_absolute_path(s: &'a [u8]) -> Result<Self, Error> { + match s.strip_prefix(STORE_DIR_WITH_SLASH.as_bytes()) { + Some(s_stripped) => Self::from_bytes(s_stripped), + None => Err(Error::MissingStoreDir), + } + } + + /// Construct a [StorePathRef] by passing the `$digest-$name` string + /// that comes after [STORE_DIR_WITH_SLASH]. + pub fn from_bytes(s: &'a [u8]) -> Result<Self, Error> { + // the whole string needs to be at least: + // + // - 32 characters (encoded hash) + // - 1 dash + // - 1 character for the name + if s.len() < ENCODED_DIGEST_SIZE + 2 { + Err(Error::InvalidLength)? + } + + let digest = nixbase32::decode_fixed(&s[..ENCODED_DIGEST_SIZE]) + .map_err(Error::InvalidHashEncoding)?; + + if s[ENCODED_DIGEST_SIZE] != b'-' { + return Err(Error::MissingDash); + } + + Ok(StorePathRef { + digest, + name: validate_name(&s[ENCODED_DIGEST_SIZE + 1..])?, + }) + } + + /// Returns an absolute store path string. + /// That is just the string representation, prefixed with the store prefix + /// ([STORE_DIR_WITH_SLASH]), + pub fn to_absolute_path(&self) -> String { + format!("{}{}", STORE_DIR_WITH_SLASH, self) + } +} + +/// NAME_CHARS contains `true` for bytes that are valid in store path names, +/// not accounting for '.' being permitted only past the first character. +static NAME_CHARS: [bool; 256] = { + let mut tbl = [false; 256]; + let mut c = 0; + + loop { + tbl[c as usize] = matches!(c, b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' | b'+' | b'-' | b'_' | b'?' | b'=' | b'.'); + + if c == u8::MAX { + break; + } + + c += 1; + } + + tbl +}; + +/// Checks a given &[u8] to match the restrictions for [StorePath::name], and +/// returns the name as string if successful. +pub(crate) fn validate_name(s: &(impl AsRef<[u8]> + ?Sized)) -> Result<&str, Error> { + let s = s.as_ref(); + + // Empty or excessively long names are not allowed. + if s.is_empty() || s.len() > 211 { + return Err(Error::InvalidLength); + } + + if s[0] == b'.' { + return Err(Error::InvalidName(s.to_vec(), 0)); + } + + let mut valid = true; + for &c in s { + valid = valid && NAME_CHARS[c as usize]; + } + + if !valid { + for (i, &c) in s.iter().enumerate() { + if !NAME_CHARS[c as usize] { + return Err(Error::InvalidName(s.to_vec(), i as u8)); + } + } + + unreachable!(); + } + + // SAFETY: We permit a subset of ASCII, which guarantees valid UTF-8. + Ok(unsafe { str::from_utf8_unchecked(s) }) +} + +impl fmt::Display for StorePath { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + StorePathRef::from(self).fmt(f) + } +} + +impl fmt::Display for StorePathRef<'_> { + /// The string representation of a store path starts with a digest (20 + /// bytes), [crate::nixbase32]-encoded, followed by a `-`, + /// and ends with the name. + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{}-{}", nixbase32::encode(&self.digest), self.name) + } +} + +#[cfg(test)] +mod tests { + use std::path::PathBuf; + + use crate::store_path::{StorePathRef, DIGEST_SIZE}; + use hex_literal::hex; + use test_case::test_case; + + use super::{Error, StorePath}; + + #[test] + fn happy_path() { + let example_nix_path_str = + "00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432"; + let nixpath = StorePath::from_bytes(example_nix_path_str.as_bytes()) + .expect("Error parsing example string"); + + let expected_digest: [u8; DIGEST_SIZE] = hex!("8a12321522fd91efbd60ebb2481af88580f61600"); + + assert_eq!("net-tools-1.60_p20170221182432", nixpath.name); + assert_eq!(nixpath.digest, expected_digest); + + assert_eq!(example_nix_path_str, nixpath.to_string()) + } + + /// This is the store path rejected when `nix-store --add`'ing an + /// empty `.gitignore` file. + /// + /// Nix 2.4 accidentally dropped this behaviour, but this is considered a bug. + /// See https://github.com/NixOS/nix/pull/9095. + #[test] + fn starts_with_dot() { + StorePath::from_bytes(b"fli4bwscgna7lpm7v5xgnjxrxh0yc7ra-.gitignore") + .expect_err("must fail"); + } + + #[test] + fn empty_name() { + StorePath::from_bytes(b"00bgd045z0d4icpbc2yy-").expect_err("must fail"); + } + + #[test] + fn excessive_length() { + StorePath::from_bytes(b"00bgd045z0d4icpbc2yy-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa") + .expect_err("must fail"); + } + + #[test] + fn invalid_hash_length() { + StorePath::from_bytes(b"00bgd045z0d4icpbc2yy-net-tools-1.60_p20170221182432") + .expect_err("must fail"); + } + + #[test] + fn invalid_encoding_hash() { + StorePath::from_bytes(b"00bgd045z0d4icpbc2yyz4gx48aku4la-net-tools-1.60_p20170221182432") + .expect_err("must fail"); + } + + #[test] + fn more_than_just_the_bare_nix_store_path() { + StorePath::from_bytes( + b"00bgd045z0d4icpbc2yyz4gx48aku4la-net-tools-1.60_p20170221182432/bin/arp", + ) + .expect_err("must fail"); + } + + #[test] + fn no_dash_between_hash_and_name() { + StorePath::from_bytes(b"00bgd045z0d4icpbc2yyz4gx48ak44lanet-tools-1.60_p20170221182432") + .expect_err("must fail"); + } + + #[test] + fn absolute_path() { + let example_nix_path_str = + "00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432"; + let nixpath_expected = + StorePathRef::from_bytes(example_nix_path_str.as_bytes()).expect("must parse"); + + let nixpath_actual = StorePathRef::from_absolute_path( + "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432".as_bytes(), + ) + .expect("must parse"); + + assert_eq!(nixpath_expected, nixpath_actual); + + assert_eq!( + "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432", + nixpath_actual.to_absolute_path(), + ); + } + + #[test] + fn absolute_path_missing_prefix() { + assert_eq!( + Error::MissingStoreDir, + StorePathRef::from_absolute_path(b"foobar-123").expect_err("must fail") + ); + } + + #[test_case( + "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432", + (StorePath::from_bytes(b"00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432").unwrap(), PathBuf::new()) + ; "without prefix")] + #[test_case( + "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432/", + (StorePath::from_bytes(b"00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432").unwrap(), PathBuf::new()) + ; "without prefix, but trailing slash")] + #[test_case( + "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432/bin/arp", + (StorePath::from_bytes(b"00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432").unwrap(), PathBuf::from("bin/arp")) + ; "with prefix")] + #[test_case( + "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432/bin/arp/", + (StorePath::from_bytes(b"00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432").unwrap(), PathBuf::from("bin/arp/")) + ; "with prefix and trailing slash")] + fn from_absolute_path_full(s: &str, expected: (StorePath, PathBuf)) { + let actual = StorePath::from_absolute_path_full(s).expect("must succeed"); + assert_eq!(expected, actual); + } + + #[test] + fn from_absolute_path_errors() { + assert_eq!( + Error::InvalidLength, + StorePath::from_absolute_path_full("/nix/store/").expect_err("must fail") + ); + assert_eq!( + Error::InvalidLength, + StorePath::from_absolute_path_full("/nix/store/foo").expect_err("must fail") + ); + assert_eq!( + Error::MissingStoreDir, + StorePath::from_absolute_path_full( + "00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432" + ) + .expect_err("must fail") + ); + } +} |