use crate::derivation::output::{Hash, Output}; use crate::derivation::write; use crate::derivation::DerivationError; use crate::nixbase32; use crate::store_path::{StorePath, STORE_DIR}; use serde::{Deserialize, Serialize}; use sha2::{Digest, Sha256}; use std::collections::BTreeSet; use std::{collections::BTreeMap, fmt, fmt::Write}; #[derive(Clone, Debug, Default, Eq, PartialEq, Serialize, Deserialize)] pub struct Derivation { #[serde(rename = "args")] pub arguments: Vec, pub builder: String, #[serde(rename = "env")] pub environment: BTreeMap, #[serde(rename = "inputDrvs")] pub input_derivations: BTreeMap>, #[serde(rename = "inputSrcs")] pub input_sources: BTreeSet, pub outputs: BTreeMap, pub system: String, } /// compress_hash takes an arbitrarily long sequence of bytes (usually /// a hash digest), and returns a sequence of bytes of length /// output_size. /// /// It's calculated by rotating through the bytes in the output buffer /// (zero- initialized), and XOR'ing with each byte of the passed /// input. It consumes 1 byte at a time, and XOR's it with the current /// value in the output buffer. /// /// This mimics equivalent functionality in C++ Nix. fn compress_hash(input: &[u8], output_size: usize) -> Vec { let mut output: Vec = vec![0; output_size]; for (ii, ch) in input.iter().enumerate() { output[ii % output_size] ^= ch; } output } /// This returns a store path, either of a derivation or a regular output. /// The string is hashed with sha256, its digest is compressed to 20 bytes, and /// nixbase32-encoded (32 characters) fn build_store_path( is_derivation: bool, fingerprint: &str, name: &str, ) -> Result { let digest = { let mut hasher = Sha256::new(); hasher.update(fingerprint); hasher.finalize() }; let compressed = compress_hash(&digest, 20); if is_derivation { StorePath::from_string(format!("{}-{}.drv", nixbase32::encode(&compressed), name).as_str()) } else { StorePath::from_string(format!("{}-{}", nixbase32::encode(&compressed), name,).as_str()) } .map_err(|_e| DerivationError::InvalidOutputName(name.to_string())) // Constructing the StorePath can only fail if the passed output name was // invalid, so map errors to a [DerivationError::InvalidOutputName]. } /// Build a store path for a literal text file in the store that may /// contain references. pub fn path_with_references, I: IntoIterator, C: AsRef<[u8]>>( name: &str, content: C, references: I, ) -> Result { let mut s = String::from("text"); for reference in references { s.push(':'); s.push_str(reference.as_ref()); } let content_digest = { let mut hasher = Sha256::new(); hasher.update(content); hasher.finalize() }; s.push_str(&format!( ":sha256:{:x}:{}:{}", content_digest, STORE_DIR, name )); build_store_path(false, &s, name) } impl Derivation { pub fn serialize(&self, writer: &mut impl Write) -> Result<(), fmt::Error> { writer.write_str(write::DERIVATION_PREFIX)?; writer.write_char(write::PAREN_OPEN)?; write::write_outputs(writer, &self.outputs)?; write::write_input_derivations(writer, &self.input_derivations)?; write::write_input_sources(writer, &self.input_sources)?; write::write_system(writer, &self.system)?; write::write_builder(writer, &self.builder)?; write::write_arguments(writer, &self.arguments)?; write::write_enviroment(writer, &self.environment)?; writer.write_char(write::PAREN_CLOSE)?; Ok(()) } /// Returns the fixed output path and its hash // (if the Derivation is fixed output), /// or None if there is no fixed output. /// This takes some shortcuts in case more than one output exists, as this /// can't be a valid fixed-output Derivation. pub fn get_fixed_output(&self) -> Option<(&String, &Hash)> { if self.outputs.len() != 1 { return None; } match self.outputs.get("out") { #[allow(clippy::manual_map)] Some(out_output) => match &out_output.hash { Some(out_output_hash) => Some((&out_output.path, out_output_hash)), // There has to be a hash, otherwise it would not be FOD None => None, }, None => None, } } /// Returns the drv path of a Derivation struct. /// /// The drv path is calculated like this: /// - Write the fingerprint of the Derivation to the sha256 hash function. /// This is: `text:`, /// all d.InputDerivations and d.InputSources (sorted, separated by a `:`), /// a `:`, /// a `sha256:`, followed by the sha256 digest of the ATerm representation (hex-encoded) /// a `:`, /// the storeDir, followed by a `:`, /// the name of a derivation, /// a `.drv`. /// - Write the .drv A-Term contents to a hash function /// - Take the digest, run hash.CompressHash(digest, 20) on it. /// - Encode it with nixbase32 /// - Use it (and the name) to construct a [StorePath]. pub fn calculate_derivation_path(&self, name: &str) -> Result { let mut s = String::from("text:"); // collect the list of paths from input_sources and input_derivations // into a (sorted, guaranteed by BTreeSet) list, and join them by : let concat_inputs: BTreeSet = { let mut inputs = self.input_sources.clone(); let input_derivation_keys: Vec = self.input_derivations.keys().cloned().collect(); inputs.extend(input_derivation_keys); inputs }; for input in concat_inputs { s.push_str(&input); s.push(':'); } // calculate the sha256 hash of the ATerm representation, and represent // it as a hex-encoded string (prefixed with sha256:). let aterm_digest = { let mut derivation_hasher = Sha256::new(); derivation_hasher.update(self.to_string()); derivation_hasher.finalize() }; s.push_str(&format!( "sha256:{:x}:{}:{}.drv", aterm_digest, STORE_DIR, name, )); build_store_path(true, &s, name) } /// Calculate the drv replacement string for a given derivation. /// /// This is either called on a struct without output paths populated, /// to provide the `drv_replacement_str` value for the `calculate_output_paths` /// function call, or called on a struct with output paths populated, to /// calculate / cache lookups for calls to fn_get_drv_replacement. /// /// `fn_get_drv_replacement` is used to look up the drv replacement strings /// for input_derivations the Derivation refers to. pub fn calculate_drv_replacement_str(&self, fn_get_drv_replacement: F) -> String where F: Fn(&str) -> String, { let mut hasher = Sha256::new(); let digest = match self.get_fixed_output() { Some((fixed_output_path, fixed_output_hash)) => { hasher.update(format!( "fixed:out:{}:{}:{}", &fixed_output_hash.algo, &fixed_output_hash.digest, fixed_output_path, )); hasher.finalize() } None => { let mut replaced_input_derivations: BTreeMap> = BTreeMap::new(); // For each input_derivation, look up the replacement. for (drv_path, input_derivation) in &self.input_derivations { replaced_input_derivations.insert( fn_get_drv_replacement(drv_path).to_string(), input_derivation.clone(), ); } // construct a new derivation struct with these replaced input derivation strings let replaced_derivation = Derivation { input_derivations: replaced_input_derivations, ..self.clone() }; // write the ATerm of that to the hash function hasher.update(replaced_derivation.to_string()); hasher.finalize() } }; format!("{:x}", digest) } /// 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 "drv replacement /// strings", and in case of non-fixed-output derivations, also knowledge /// of "drv replacement" strings (recursively) of all input derivations. /// /// We solve this by asking the caller of this function to provide /// the drv replacement string of the current derivation itself, /// which is ran on the struct without output paths. /// /// This sound terribly ugly, but won't be too much of a concern later on, as /// naming fixed-output paths once uploaded will be a tvix-store concern, /// so there's no need to calculate them here anymore. /// /// 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, drv_replacement_str: &str, ) -> Result<(), DerivationError> { // Check if the Derivation is fixed output, because they cause // different fingerprints to be hashed. match self.get_fixed_output() { None => { // 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()); // calculate the output_name_path, which is the part of the NixPath after the digest. let mut output_path_name = name.to_string(); if output_name != "out" { output_path_name.push('-'); output_path_name.push_str(output_name); } let s = &format!( "output:{}:sha256:{}:{}:{}", output_name, drv_replacement_str, STORE_DIR, output_path_name, ); let abs_store_path = build_store_path(false, s, &output_path_name)?.to_absolute_path(); output.path = abs_store_path.clone(); self.environment .insert(output_name.to_string(), abs_store_path); } } Some((fixed_output_path, fixed_output_hash)) => { // 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!(fixed_output_path.is_empty()); let s = { let mut s = String::new(); // Fixed-output derivation. // There's two different hashing strategies in place, depending on the value of hash.algo. // This code is _weird_ but it is what Nix is doing. See: // https://github.com/NixOS/nix/blob/1385b2007804c8a0370f2a6555045a00e34b07c7/src/libstore/store-api.cc#L178-L196 if fixed_output_hash.algo == "r:sha256" { s.push_str(&format!( "source:sha256:{}", fixed_output_hash.digest, // nixbase32 )); } else { s.push_str("output:out:sha256:"); // This is drv_replacement for FOD, with an empty fixed_output_path. s.push_str(drv_replacement_str); } s.push_str(&format!(":{}:{}", STORE_DIR, name)); s }; let abs_store_path = build_store_path(false, &s, name)?.to_absolute_path(); self.outputs.insert( "out".to_string(), Output { path: abs_store_path.clone(), hash: Some(fixed_output_hash.clone()), }, ); self.environment.insert("out".to_string(), abs_store_path); } }; Ok(()) } } impl fmt::Display for Derivation { /// Formats the Derivation in ATerm representation. fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.serialize(f) } }