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; #[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<String, BTreeSet<String>>, /// Plain store paths of additional inputs. #[serde(rename = "inputSrcs")] pub input_sources: BTreeSet<String>, /// 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> { 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, &self.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> { 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(&mut buffer).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> = { let mut inputs = self.input_sources.clone(); let input_derivation_keys: Vec<String> = self.input_derivations.keys().cloned().collect(); inputs.extend(input_derivation_keys); inputs }; 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) 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.digest().to_nix_hex_string(), out_output.path )) .finalize() .into(), ) } /// Calculates the hash of a derivation modulo fixed-output subderivations. /// /// This is called `hashDerivationModulo` in nixcpp. /// /// It returns a [NixHash], created by calculating 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}:${fodPath}` string is hashed instead of /// the A-Term. /// /// If the derivation is not a fixed derivation, it's up to the caller of /// this function to provide a lookup function to lookup these calculation /// results of parent derivations at `fn_get_derivation_or_fod_hash` (by /// drv path). pub fn derivation_or_fod_hash<F>(&self, fn_get_derivation_or_fod_hash: F) -> NixHash where F: Fn(&StorePathRef) -> NixHash, { // Fixed-output derivations return a fixed hash. // Non-Fixed-output derivations return the sha256 digest of the ATerm // notation, but with all input_derivation paths replaced by a recursive // call to this function. // We use fn_get_derivation_or_fod_hash here, so callers can precompute this. NixHash::Sha256(self.fod_digest().unwrap_or({ // construct a new Derivation struct with input derivation strings replaced. let replaced_derivation = Derivation { // For each input_derivation, look up the // derivation_or_fod_hash, and replace the derivation path with // it's HEXLOWER digest. input_derivations: BTreeMap::from_iter(self.input_derivations.iter().map( |(drv_path_str, output_names)| { // parse drv_path to StorePathRef let drv_path = StorePathRef::from_absolute_path(drv_path_str.as_bytes()) .expect("invalid input derivation path"); let encoded_hash = data_encoding::HEXLOWER .encode(fn_get_derivation_or_fod_hash(&drv_path).digest_as_bytes()); (encoded_hash, output_names.to_owned()) }, )), ..self.clone() }; // write the ATerm of that to the hash function let mut hasher = Sha256::new(); hasher.update(replaced_derivation.to_aterm_bytes()); hasher.finalize().into() })) } /// This calculates all output paths of a Derivation and updates the struct. /// It requires the struct to be initially without output paths. /// This means, self.outputs[$outputName].path needs to be an empty string, /// and self.environment[$outputName] needs to be an empty string. /// /// Output path calculation requires knowledge of the /// derivation_or_fod_hash [NixHash], which (in case of non-fixed-output /// derivations) also requires knowledge of other hash_derivation_modulo /// [NixHash]es. /// /// We solve this by asking the caller of this function to provide the /// hash_derivation_modulo of the current Derivation. /// /// On completion, self.environment[$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, derivation_or_fod_hash: &NixHash, ) -> 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_empty()); let path_name = output_path_name(name, output_name); // For fixed output derivation we use the per-output info, otherwise we use the // derivation hash. 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(derivation_or_fod_hash, output_name, &path_name).map_err(|e| { DerivationError::InvalidOutputDerivationPath( output_name.to_string(), store_path::BuildStorePathError::InvalidStorePath(e), ) })? }; output.path = abs_store_path.to_absolute_path(); 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), } }