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Diffstat (limited to 'tvix/nix-compat/src/derivation/mod.rs')
| -rw-r--r-- | tvix/nix-compat/src/derivation/mod.rs | 305 |
1 files changed, 305 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/derivation/mod.rs b/tvix/nix-compat/src/derivation/mod.rs new file mode 100644 index 0000000000..6e12e3ea86 --- /dev/null +++ b/tvix/nix-compat/src/derivation/mod.rs @@ -0,0 +1,305 @@ +use crate::store_path::{ + self, build_ca_path, build_output_path, build_text_path, StorePath, StorePathRef, +}; +use bstr::BString; +use serde::{Deserialize, Serialize}; +use sha2::{Digest, Sha256}; +use std::collections::{BTreeMap, BTreeSet}; +use std::io; + +mod errors; +mod output; +mod parse_error; +mod parser; +mod validate; +mod write; + +#[cfg(test)] +mod tests; + +// Public API of the crate. +pub use crate::nixhash::{CAHash, NixHash}; +pub use errors::{DerivationError, OutputError}; +pub use output::Output; + +use self::write::AtermWriteable; + +#[derive(Clone, Debug, Default, Eq, PartialEq, Serialize, Deserialize)] +pub struct Derivation { + #[serde(rename = "args")] + pub arguments: Vec<String>, + + pub builder: String, + + #[serde(rename = "env")] + pub environment: BTreeMap<String, BString>, + + /// Map from drv path to output names used from this derivation. + #[serde(rename = "inputDrvs")] + pub input_derivations: BTreeMap<StorePath, BTreeSet<String>>, + + /// Plain store paths of additional inputs. + #[serde(rename = "inputSrcs")] + pub input_sources: BTreeSet<StorePath>, + + /// Maps output names to Output. + pub outputs: BTreeMap<String, Output>, + + pub system: String, +} + +impl Derivation { + /// write the Derivation to the given [std::io::Write], in ATerm format. + /// + /// The only errors returns are these when writing to the passed writer. + pub fn serialize(&self, writer: &mut impl std::io::Write) -> Result<(), io::Error> { + self.serialize_with_replacements(writer, &self.input_derivations) + } + + /// Like `serialize` but allow replacing the input_derivations for hash calculations. + fn serialize_with_replacements( + &self, + writer: &mut impl std::io::Write, + input_derivations: &BTreeMap<impl AtermWriteable, BTreeSet<String>>, + ) -> Result<(), io::Error> { + use write::*; + + writer.write_all(write::DERIVATION_PREFIX.as_bytes())?; + write_char(writer, write::PAREN_OPEN)?; + + write_outputs(writer, &self.outputs)?; + write_char(writer, COMMA)?; + + write_input_derivations(writer, input_derivations)?; + write_char(writer, COMMA)?; + + write_input_sources(writer, &self.input_sources)?; + write_char(writer, COMMA)?; + + write_system(writer, &self.system)?; + write_char(writer, COMMA)?; + + write_builder(writer, &self.builder)?; + write_char(writer, COMMA)?; + + write_arguments(writer, &self.arguments)?; + write_char(writer, COMMA)?; + + write_environment(writer, &self.environment)?; + + write_char(writer, PAREN_CLOSE)?; + + Ok(()) + } + + /// return the ATerm serialization. + pub fn to_aterm_bytes(&self) -> Vec<u8> { + self.to_aterm_bytes_with_replacements(&self.input_derivations) + } + + /// Like `to_aterm_bytes`, but accept a different BTreeMap for input_derivations. + /// This is used to render the ATerm representation of a Derivation "modulo + /// fixed-output derivations". + fn to_aterm_bytes_with_replacements( + &self, + input_derivations: &BTreeMap<impl AtermWriteable, BTreeSet<String>>, + ) -> Vec<u8> { + let mut buffer: Vec<u8> = Vec::new(); + + // invoke serialize and write to the buffer. + // Note we only propagate errors writing to the writer in serialize, + // which won't panic for the string we write to. + self.serialize_with_replacements(&mut buffer, input_derivations) + .unwrap(); + + buffer + } + + /// Parse an Derivation in ATerm serialization, and validate it passes our + /// set of validations. + pub fn from_aterm_bytes(b: &[u8]) -> Result<Derivation, parser::Error<&[u8]>> { + parser::parse(b) + } + + /// Returns the drv path of a [Derivation] struct. + /// + /// The drv path is calculated by invoking [build_text_path], using + /// the `name` with a `.drv` suffix as name, all [Derivation::input_sources] and + /// keys of [Derivation::input_derivations] as references, and the ATerm string of + /// the [Derivation] as content. + pub fn calculate_derivation_path(&self, name: &str) -> Result<StorePath, DerivationError> { + // append .drv to the name + let name = &format!("{}.drv", name); + + // collect the list of paths from input_sources and input_derivations + // into a (sorted, guaranteed by BTreeSet) list of references + let references: BTreeSet<String> = self + .input_sources + .iter() + .chain(self.input_derivations.keys()) + .map(StorePath::to_absolute_path) + .collect(); + + build_text_path(name, self.to_aterm_bytes(), references) + .map(|s| s.to_owned()) + .map_err(|_e| DerivationError::InvalidOutputName(name.to_string())) + } + + /// Returns the FOD digest, if the derivation is fixed-output, or None if + /// it's not. + /// TODO: this is kinda the string from [build_ca_path] with a + /// [CAHash::Flat], what's fed to `build_store_path_from_fingerprint_parts` + /// (except the out_output.path being an empty string) + pub fn fod_digest(&self) -> Option<[u8; 32]> { + if self.outputs.len() != 1 { + return None; + } + + let out_output = self.outputs.get("out")?; + let ca_hash = &out_output.ca_hash.as_ref()?; + + Some( + Sha256::new_with_prefix(format!( + "fixed:out:{}{}:{}", + ca_kind_prefix(ca_hash), + ca_hash.hash().to_nix_hex_string(), + out_output + .path + .as_ref() + .map(StorePath::to_absolute_path) + .as_ref() + .map(|s| s as &str) + .unwrap_or(""), + )) + .finalize() + .into(), + ) + } + + /// Calculates the hash of a derivation modulo fixed-output subderivations. + /// + /// This is called `hashDerivationModulo` in nixcpp. + /// + /// It returns the sha256 digest of the derivation ATerm representation, + /// except that: + /// - any input derivation paths have beed replaced "by the result of a + /// recursive call to this function" and that + /// - for fixed-output derivations the special + /// `fixed:out:${algo}:${digest}:${fodPath}` string is hashed instead of + /// the A-Term. + /// + /// It's up to the caller of this function to provide a (infallible) lookup + /// function to query [hash_derivation_modulo] of direct input derivations, + /// by their [StorePathRef]. + /// It will only be called in case the derivation is not a fixed-output + /// derivation. + pub fn hash_derivation_modulo<F>(&self, fn_lookup_hash_derivation_modulo: F) -> [u8; 32] + where + F: Fn(&StorePathRef) -> [u8; 32], + { + // Fixed-output derivations return a fixed hash. + // Non-Fixed-output derivations return the sha256 digest of the ATerm + // notation, but with all input_derivation paths replaced by a recursive + // call to this function. + // We call [fn_lookup_hash_derivation_modulo] rather than recursing + // ourselves, so callers can precompute this. + self.fod_digest().unwrap_or({ + // For each input_derivation, look up the hash derivation modulo, + // and replace the derivation path in the aterm with it's HEXLOWER digest. + let aterm_bytes = self.to_aterm_bytes_with_replacements(&BTreeMap::from_iter( + self.input_derivations + .iter() + .map(|(drv_path, output_names)| { + let hash = fn_lookup_hash_derivation_modulo(&drv_path.into()); + + (hash, output_names.to_owned()) + }), + )); + + // write the ATerm of that to the hash function and return its digest. + Sha256::new_with_prefix(aterm_bytes).finalize().into() + }) + } + + /// This calculates all output paths of a Derivation and updates the struct. + /// It requires the struct to be initially without output paths. + /// This means, self.outputs[$outputName].path needs to be an empty string, + /// and self.environment[$outputName] needs to be an empty string. + /// + /// Output path calculation requires knowledge of the + /// [hash_derivation_modulo], which (in case of non-fixed-output + /// derivations) also requires knowledge of the [hash_derivation_modulo] of + /// input derivations (recursively). + /// + /// To avoid recursing and doing unnecessary calculation, we simply + /// ask the caller of this function to provide the result of the + /// [hash_derivation_modulo] call of the current [Derivation], + /// and leave it up to them to calculate it when needed. + /// + /// On completion, `self.environment[$outputName]` and + /// `self.outputs[$outputName].path` are set to the calculated output path for all + /// outputs. + pub fn calculate_output_paths( + &mut self, + name: &str, + hash_derivation_modulo: &[u8; 32], + ) -> Result<(), DerivationError> { + // The fingerprint and hash differs per output + for (output_name, output) in self.outputs.iter_mut() { + // Assert that outputs are not yet populated, to avoid using this function wrongly. + // We don't also go over self.environment, but it's a sufficient + // footgun prevention mechanism. + assert!(output.path.is_none()); + + let path_name = output_path_name(name, output_name); + + // For fixed output derivation we use [build_ca_path], otherwise we + // use [build_output_path] with [hash_derivation_modulo]. + let abs_store_path = if let Some(ref hwm) = output.ca_hash { + build_ca_path(&path_name, hwm, Vec::<String>::new(), false).map_err(|e| { + DerivationError::InvalidOutputDerivationPath(output_name.to_string(), e) + })? + } else { + build_output_path(hash_derivation_modulo, output_name, &path_name).map_err(|e| { + DerivationError::InvalidOutputDerivationPath( + output_name.to_string(), + store_path::BuildStorePathError::InvalidStorePath(e), + ) + })? + }; + + output.path = Some(abs_store_path.to_owned()); + self.environment.insert( + output_name.to_string(), + abs_store_path.to_absolute_path().into(), + ); + } + + Ok(()) + } +} + +/// Calculate the name part of the store path of a derivation [Output]. +/// +/// It's the name, and (if it's the non-out output), the output name +/// after a `-`. +fn output_path_name(derivation_name: &str, output_name: &str) -> String { + let mut output_path_name = derivation_name.to_string(); + if output_name != "out" { + output_path_name.push('-'); + output_path_name.push_str(output_name); + } + output_path_name +} + +/// For a [CAHash], return the "prefix" used for NAR purposes. +/// For [CAHash::Flat], this is an empty string, for [CAHash::Nar], it's "r:". +/// Panics for other [CAHash] kinds, as they're not valid in a derivation +/// context. +fn ca_kind_prefix(ca_hash: &CAHash) -> &'static str { + match ca_hash { + CAHash::Flat(_) => "", + CAHash::Nar(_) => "r:", + _ => panic!("invalid ca hash in derivation context: {:?}", ca_hash), + } +} |