use crate::nix_hash; use crate::output::{Hash, Output}; use crate::write; use serde::{Deserialize, Serialize}; use sha2::{Digest, Sha256}; use std::{collections::BTreeMap, fmt, fmt::Write}; use tvix_store::nixbase32::NIXBASE32; use tvix_store::nixpath::{NixPath, ParseNixPathError, STORE_DIR}; #[derive(Clone, Debug, 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: Vec, pub outputs: BTreeMap, pub system: String, } /// This returns a store path, either of a derivation or a regular output. /// The path_hash is compressed to 20 bytes, and nixbase32-encoded (32 characters) fn build_store_path( is_derivation: bool, path_hash: &[u8], name: &str, ) -> Result { let compressed = nix_hash::compress_hash(path_hash, 20); if is_derivation { NixPath::from_string( format!( "{}-{}{}", NIXBASE32.encode(&compressed), name, write::DOT_FILE_EXT, ) .as_str(), ) } else { NixPath::from_string(format!("{}-{}", NIXBASE32.encode(&compressed), name,).as_str()) } } 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 NixPath. pub fn calculate_derivation_path(&self, name: &str) -> Result { let mut hasher = Sha256::new(); // collect the list of paths from input_sources and input_derivations // into a sorted list, and join them by : hasher.update(write::TEXT_COLON); let concat_inputs: Vec = { let mut inputs = self.input_sources.clone(); let input_derivation_keys: Vec = self.input_derivations.keys().cloned().collect(); inputs.extend(input_derivation_keys); inputs.sort(); inputs }; for input in concat_inputs { hasher.update(input); hasher.update(write::COLON); } // calculate the sha256 hash of the ATerm representation, and represent // it as a hex-encoded string (prefixed with sha256:). hasher.update(write::SHA256_COLON); let digest = { let mut derivation_hasher = Sha256::new(); derivation_hasher.update(self.to_string()); derivation_hasher.finalize() }; hasher.update(format!("{:x}", digest)); hasher.update(write::COLON); hasher.update(STORE_DIR); hasher.update(write::COLON); hasher.update(name); hasher.update(write::DOT_FILE_EXT); build_store_path(true, &hasher.finalize(), 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("fixed:out:"); hasher.update(&fixed_output_hash.algo); hasher.update(":"); hasher.update(&fixed_output_hash.digest); hasher.update(":"); hasher.update(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.to_vec(), ); } // 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<(), ParseNixPathError> { let mut hasher = Sha256::new(); // 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()); hasher.update("output:"); hasher.update(output_name); hasher.update(":sha256:"); hasher.update(drv_replacement_str); hasher.update(":"); hasher.update(tvix_store::nixpath::STORE_DIR); hasher.update(":"); // 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); } hasher.update(output_path_name.as_str()); let digest = hasher.finalize_reset(); let abs_store_path = format!( "{}/{}", tvix_store::nixpath::STORE_DIR, build_store_path(false, &digest, &output_path_name)? ); 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 digest = { // 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" { hasher.update("source:"); hasher.update("sha256"); hasher.update(":"); hasher.update(fixed_output_hash.digest.clone()); // nixbase32 } else { hasher.update("output:out:sha256:"); // This is drv_replacement for FOD, with an empty fixed_output_path. hasher.update(drv_replacement_str); } hasher.update(":"); hasher.update(tvix_store::nixpath::STORE_DIR); hasher.update(":"); hasher.update(name); hasher.finalize() }; let abs_store_path = format!( "{}/{}", tvix_store::nixpath::STORE_DIR, build_store_path(false, &digest, name)? ); 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) } }