use crate::{
nixhash::HashAlgo,
store_path::{
self, build_store_path_from_fingerprint, build_store_path_from_references, StorePath,
},
};
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use std::collections::{BTreeMap, BTreeSet};
mod errors;
mod output;
mod string_escape;
mod validate;
mod write;
#[cfg(test)]
mod tests;
// Public API of the crate.
pub use crate::nixhash::{NixHash, NixHashWithMode};
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, String>,
#[serde(rename = "inputDrvs")]
pub input_derivations: BTreeMap<String, BTreeSet<String>>,
#[serde(rename = "inputSrcs")]
pub input_sources: BTreeSet<String>,
pub outputs: BTreeMap<String, Output>,
pub system: String,
}
impl Derivation {
/// write the Derivation to the given [std::fmt::Write], in ATerm format.
///
/// The only errors returns are these when writing to the passed writer.
pub fn serialize(&self, writer: &mut impl std::fmt::Write) -> Result<(), std::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(())
}
/// return the ATerm serialization as a string.
pub fn to_aterm_string(&self) -> String {
let mut buffer = String::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
}
/// Returns the drv path of a [Derivation] struct.
///
/// The drv path is calculated by invoking [build_store_path_from_references], 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_store_path_from_references(name, self.to_aterm_string(), references)
.map_err(|_e| DerivationError::InvalidOutputName(name.to_string()))
}
/// Returns the FOD digest, if the derivation is fixed-output, or None if
/// it's not.
fn fod_digest(&self) -> Option<Vec<u8>> {
if self.outputs.len() != 1 {
return None;
}
let out_output = self.outputs.get("out")?;
Some(
Sha256::new_with_prefix(format!(
"fixed:out:{}:{}",
out_output.hash_with_mode.clone()?.to_nix_hash_string(),
out_output.path
))
.finalize()
.to_vec(),
)
}
/// 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}:${fodPath}` string is hashed instead of
/// the A-Term.
///
/// If the derivation is not a fixed derivation, it's up to the caller of
/// this function to provide a lookup function to lookup these calculation
/// results of parent derivations at `fn_get_hash_derivation_modulo` (by
/// drv path).
pub fn derivation_or_fod_hash<F>(&self, fn_get_derivation_or_fod_hash: F) -> NixHash
where
F: Fn(&str) -> NixHash,
{
// Fixed-output derivations return a fixed hash.
// Non-Fixed-output derivations return a hash of the ATerm notation, but with all
// input_derivation paths replaced by a recursive call to this function.
// We use fn_get_derivation_or_fod_hash here, so callers can precompute this.
let digest = self.fod_digest().unwrap_or({
// This is a new map from derivation_or_fod_hash.digest (as lowerhex)
// to list of output names
let mut replaced_input_derivations: BTreeMap<String, BTreeSet<String>> =
BTreeMap::new();
// For each input_derivation, look up the
// derivation_or_fod_hash, and replace the derivation path with it's HEXLOWER
// digest.
// This is not the [NixHash::to_nix_hash_string], but without the sha256: prefix).
for (drv_path, output_names) in &self.input_derivations {
replaced_input_derivations.insert(
data_encoding::HEXLOWER.encode(&fn_get_derivation_or_fod_hash(drv_path).digest),
output_names.clone(),
);
}
// construct a new derivation struct with these replaced input derivation strings
let replaced_derivation = Derivation {
input_derivations: replaced_input_derivations,
..self.clone()
};
// write the ATerm of that to the hash function
let mut hasher = Sha256::new();
hasher.update(replaced_derivation.to_aterm_string());
hasher.finalize().to_vec()
});
NixHash::new(crate::nixhash::HashAlgo::Sha256, digest.to_vec())
}
/// This calculates all output paths of a Derivation and updates the struct.
/// It requires the struct to be initially without output paths.
/// This means, self.outputs[$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> {
let num_outputs = self.outputs.len();
// 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.
// It's the name, and (if it's the non-out output), the output name after a `-`.
let output_path_name = {
let mut output_path_name = name.to_string();
if output_name != "out" {
output_path_name.push('-');
output_path_name.push_str(output_name);
}
output_path_name
};
// In the case this is a fixed-output derivation AND the
// hash mode is recursive AND the hash algo is sha256, a
// custom fingerprint is used to calculate the output path.
//
// In all other cases, the fingerprint is derived from the
// derivation_or_fod_hash.
let custom_fp: Option<String> =
if num_outputs == 1 && output_name == "out" && output.hash_with_mode.is_some() {
match &output.hash_with_mode {
Some(NixHashWithMode::Recursive(NixHash {
digest,
algo: HashAlgo::Sha256,
})) => Some(format!(
"source:sha256:{}:{}:{}",
data_encoding::HEXLOWER.encode(digest),
store_path::STORE_DIR,
output_path_name
)),
_ => None,
}
} else {
None
};
// If no custom_fp has been determined, use the default one.
let fp = custom_fp.unwrap_or(format!(
"output:{}:{}:{}:{}",
output_name,
derivation_or_fod_hash.to_nix_hash_string(),
store_path::STORE_DIR,
output_path_name,
));
let abs_store_path = build_store_path_from_fingerprint(&output_path_name, &fp)
.map_err(|_e| DerivationError::InvalidOutputName(output_path_name.to_string()))?
.to_absolute_path();
output.path = abs_store_path.clone();
self.environment
.insert(output_name.to_string(), abs_store_path);
}
Ok(())
}
}
