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Diffstat (limited to 'tvix/nix-compat/src/nixhash/mod.rs')
| -rw-r--r-- | tvix/nix-compat/src/nixhash/mod.rs | 602 |
1 files changed, 602 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/nixhash/mod.rs b/tvix/nix-compat/src/nixhash/mod.rs new file mode 100644 index 0000000000..d86cb8b79f --- /dev/null +++ b/tvix/nix-compat/src/nixhash/mod.rs @@ -0,0 +1,602 @@ +use crate::nixbase32; +use bstr::ByteSlice; +use data_encoding::{BASE64, BASE64_NOPAD, HEXLOWER}; +use serde::Deserialize; +use serde::Serialize; +use std::cmp::Ordering; +use std::fmt::Display; +use thiserror; + +mod algos; +mod ca_hash; + +pub use algos::HashAlgo; +pub use ca_hash::CAHash; +pub use ca_hash::HashMode as CAHashMode; + +/// NixHash represents hashes known by Nix. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum NixHash { + Md5([u8; 16]), + Sha1([u8; 20]), + Sha256([u8; 32]), + Sha512(Box<[u8; 64]>), +} + +/// Same order as sorting the corresponding nixbase32 strings. +/// +/// This order is used in the ATerm serialization of a derivation +/// and thus affects the calculated output hash. +impl Ord for NixHash { + fn cmp(&self, other: &NixHash) -> Ordering { + self.digest_as_bytes().cmp(other.digest_as_bytes()) + } +} + +// See Ord for reason to implement this manually. +impl PartialOrd for NixHash { + fn partial_cmp(&self, other: &NixHash) -> Option<Ordering> { + Some(self.cmp(other)) + } +} + +impl Display for NixHash { + fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> { + write!( + f, + "{}-{}", + self.algo(), + nixbase32::encode(self.digest_as_bytes()) + ) + } +} + +/// convenience Result type for all nixhash parsing Results. +pub type NixHashResult<V> = std::result::Result<V, Error>; + +impl NixHash { + /// returns the algo as [HashAlgo]. + pub fn algo(&self) -> HashAlgo { + match self { + NixHash::Md5(_) => HashAlgo::Md5, + NixHash::Sha1(_) => HashAlgo::Sha1, + NixHash::Sha256(_) => HashAlgo::Sha256, + NixHash::Sha512(_) => HashAlgo::Sha512, + } + } + + /// returns the digest as variable-length byte slice. + pub fn digest_as_bytes(&self) -> &[u8] { + match self { + NixHash::Md5(digest) => digest, + NixHash::Sha1(digest) => digest, + NixHash::Sha256(digest) => digest, + NixHash::Sha512(digest) => digest.as_ref(), + } + } + + /// Constructs a [NixHash] from the Nix default hash format, + /// the inverse of [Self::to_nix_hex_string]. + pub fn from_nix_hex_str(s: &str) -> Option<Self> { + let (tag, digest) = s.split_once(':')?; + + (match tag { + "md5" => nixbase32::decode_fixed(digest).map(NixHash::Md5), + "sha1" => nixbase32::decode_fixed(digest).map(NixHash::Sha1), + "sha256" => nixbase32::decode_fixed(digest).map(NixHash::Sha256), + "sha512" => nixbase32::decode_fixed(digest) + .map(Box::new) + .map(NixHash::Sha512), + _ => return None, + }) + .ok() + } + + /// Formats a [NixHash] in the Nix default hash format, + /// which is the algo, followed by a colon, then the lower hex encoded digest. + pub fn to_nix_hex_string(&self) -> String { + format!("{}:{}", self.algo(), self.to_plain_hex_string()) + } + + /// Formats a [NixHash] in the format that's used inside CAHash, + /// which is the algo, followed by a colon, then the nixbase32-encoded digest. + pub(crate) fn to_nix_nixbase32_string(&self) -> String { + format!( + "{}:{}", + self.algo(), + nixbase32::encode(self.digest_as_bytes()) + ) + } + + /// Returns the digest as a hex string -- without any algorithm prefix. + pub fn to_plain_hex_string(&self) -> String { + HEXLOWER.encode(self.digest_as_bytes()) + } +} + +impl TryFrom<(HashAlgo, &[u8])> for NixHash { + type Error = Error; + + /// Constructs a new [NixHash] by specifying [HashAlgo] and digest. + /// It can fail if the passed digest length doesn't match what's expected for + /// the passed algo. + fn try_from(value: (HashAlgo, &[u8])) -> NixHashResult<Self> { + let (algo, digest) = value; + from_algo_and_digest(algo, digest) + } +} + +impl<'de> Deserialize<'de> for NixHash { + fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> + where + D: serde::Deserializer<'de>, + { + let str: &'de str = Deserialize::deserialize(deserializer)?; + from_str(str, None).map_err(|_| { + serde::de::Error::invalid_value(serde::de::Unexpected::Str(str), &"NixHash") + }) + } +} + +impl Serialize for NixHash { + fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> + where + S: serde::Serializer, + { + // encode as SRI + let string = format!("{}-{}", self.algo(), BASE64.encode(self.digest_as_bytes())); + string.serialize(serializer) + } +} + +/// Constructs a new [NixHash] by specifying [HashAlgo] and digest. +/// It can fail if the passed digest length doesn't match what's expected for +/// the passed algo. +pub fn from_algo_and_digest(algo: HashAlgo, digest: &[u8]) -> NixHashResult<NixHash> { + if digest.len() != algo.digest_length() { + return Err(Error::InvalidEncodedDigestLength(digest.len(), algo)); + } + + Ok(match algo { + HashAlgo::Md5 => NixHash::Md5(digest.try_into().unwrap()), + HashAlgo::Sha1 => NixHash::Sha1(digest.try_into().unwrap()), + HashAlgo::Sha256 => NixHash::Sha256(digest.try_into().unwrap()), + HashAlgo::Sha512 => NixHash::Sha512(Box::new(digest.try_into().unwrap())), + }) +} + +/// Errors related to NixHash construction. +#[derive(Debug, Eq, PartialEq, thiserror::Error)] +pub enum Error { + #[error("invalid hash algo: {0}")] + InvalidAlgo(String), + #[error("invalid SRI string: {0}")] + InvalidSRI(String), + #[error("invalid encoded digest length '{0}' for algo {1}")] + InvalidEncodedDigestLength(usize, HashAlgo), + #[error("invalid base16 encoding: {0}")] + InvalidBase16Encoding(data_encoding::DecodeError), + #[error("invalid base32 encoding: {0}")] + InvalidBase32Encoding(data_encoding::DecodeError), + #[error("invalid base64 encoding: {0}")] + InvalidBase64Encoding(data_encoding::DecodeError), + #[error("conflicting hash algo: {0} (hash_algo) vs {1} (inline)")] + ConflictingHashAlgos(HashAlgo, HashAlgo), + #[error("missing inline hash algo, but no externally-specified algo: {0}")] + MissingInlineHashAlgo(String), +} + +/// Nix allows specifying hashes in various encodings, and magically just +/// derives the encoding. +/// This function parses strings to a NixHash. +/// +/// Hashes can be: +/// - Nix hash strings +/// - SRI hashes +/// - bare digests +/// +/// Encoding for Nix hash strings or bare digests can be: +/// - base16 (lowerhex), +/// - nixbase32, +/// - base64 (StdEncoding) +/// - sri string +/// +/// The encoding is derived from the length of the string and the hash type. +/// The hash is communicated out-of-band, but might also be in-band (in the +/// case of a nix hash string or SRI), in which it needs to be consistent with the +/// one communicated out-of-band. +pub fn from_str(s: &str, algo_str: Option<&str>) -> NixHashResult<NixHash> { + // if algo_str is some, parse or bail out + let algo: Option<HashAlgo> = if let Some(algo_str) = algo_str { + Some(algo_str.try_into()?) + } else { + None + }; + + // Peek at the beginning of the string to detect SRI hashes. + if s.starts_with("sha1-") + || s.starts_with("sha256-") + || s.starts_with("sha512-") + || s.starts_with("md5-") + { + let parsed_nixhash = from_sri_str(s)?; + + // ensure the algo matches with what has been passed externally, if so. + if let Some(algo) = algo { + if algo != parsed_nixhash.algo() { + return Err(Error::ConflictingHashAlgos(algo, parsed_nixhash.algo())); + } + } + return Ok(parsed_nixhash); + } + + // Peek at the beginning again to see if it's a Nix Hash + if s.starts_with("sha1:") + || s.starts_with("sha256:") + || s.starts_with("sha512:") + || s.starts_with("md5:") + { + let parsed_nixhash = from_nix_str(s)?; + // ensure the algo matches with what has been passed externally, if so. + if let Some(algo) = algo { + if algo != parsed_nixhash.algo() { + return Err(Error::ConflictingHashAlgos(algo, parsed_nixhash.algo())); + } + } + return Ok(parsed_nixhash); + } + + // Neither of these, assume a bare digest, so there MUST be an externally-passed algo. + match algo { + // Fail if there isn't. + None => Err(Error::MissingInlineHashAlgo(s.to_string())), + Some(algo) => decode_digest(s.as_bytes(), algo), + } +} + +/// Parses a Nix hash string ($algo:$digest) to a NixHash. +pub fn from_nix_str(s: &str) -> NixHashResult<NixHash> { + if let Some(rest) = s.strip_prefix("sha1:") { + decode_digest(rest.as_bytes(), HashAlgo::Sha1) + } else if let Some(rest) = s.strip_prefix("sha256:") { + decode_digest(rest.as_bytes(), HashAlgo::Sha256) + } else if let Some(rest) = s.strip_prefix("sha512:") { + decode_digest(rest.as_bytes(), HashAlgo::Sha512) + } else if let Some(rest) = s.strip_prefix("md5:") { + decode_digest(rest.as_bytes(), HashAlgo::Md5) + } else { + Err(Error::InvalidAlgo(s.to_string())) + } +} + +/// Parses a Nix SRI string to a NixHash. +/// Contrary to the SRI spec, Nix doesn't have an understanding of passing +/// multiple hashes (with different algos) in SRI hashes. +/// It instead simply cuts everything off after the expected length for the +/// specified algo, and tries to parse the rest in permissive base64 (allowing +/// missing padding). +pub fn from_sri_str(s: &str) -> NixHashResult<NixHash> { + // split at the first occurence of "-" + let (algo_str, digest_str) = s + .split_once('-') + .ok_or_else(|| Error::InvalidSRI(s.to_string()))?; + + // try to map the part before that `-` to a supported hash algo: + let algo: HashAlgo = algo_str.try_into()?; + + // For the digest string, Nix ignores everything after the expected BASE64 + // (with padding) length, to account for the fact SRI allows specifying more + // than one checksum, so shorten it. + let digest_str = { + let encoded_max_len = BASE64.encode_len(algo.digest_length()); + if digest_str.len() > encoded_max_len { + digest_str[..encoded_max_len].as_bytes() + } else { + digest_str.as_bytes() + } + }; + + // if the digest string is too small to fit even the BASE64_NOPAD version, bail out. + if digest_str.len() < BASE64_NOPAD.encode_len(algo.digest_length()) { + return Err(Error::InvalidEncodedDigestLength(digest_str.len(), algo)); + } + + // trim potential padding, and use a version that does not do trailing bit + // checking. + let mut spec = BASE64_NOPAD.specification(); + spec.check_trailing_bits = false; + let encoding = spec + .encoding() + .expect("Tvix bug: failed to get the special base64 encoder for Nix SRI hashes"); + + let digest = encoding + .decode(digest_str.trim_end_with(|c| c == '=')) + .map_err(Error::InvalidBase64Encoding)?; + + from_algo_and_digest(algo, &digest) +} + +/// Decode a plain digest depending on the hash algo specified externally. +/// hexlower, nixbase32 and base64 encodings are supported - the encoding is +/// inferred from the input length. +fn decode_digest(s: &[u8], algo: HashAlgo) -> NixHashResult<NixHash> { + // for the chosen hash algo, calculate the expected (decoded) digest length + // (as bytes) + let digest = if s.len() == HEXLOWER.encode_len(algo.digest_length()) { + HEXLOWER + .decode(s.as_ref()) + .map_err(Error::InvalidBase16Encoding)? + } else if s.len() == nixbase32::encode_len(algo.digest_length()) { + nixbase32::decode(s).map_err(Error::InvalidBase32Encoding)? + } else if s.len() == BASE64.encode_len(algo.digest_length()) { + BASE64 + .decode(s.as_ref()) + .map_err(Error::InvalidBase64Encoding)? + } else { + Err(Error::InvalidEncodedDigestLength(s.len(), algo))? + }; + + Ok(from_algo_and_digest(algo, &digest).unwrap()) +} + +#[cfg(test)] +mod tests { + use crate::{ + nixbase32, + nixhash::{self, HashAlgo, NixHash}, + }; + use data_encoding::{BASE64, BASE64_NOPAD, HEXLOWER}; + use hex_literal::hex; + use rstest::rstest; + + const DIGEST_SHA1: [u8; 20] = hex!("6016777997c30ab02413cf5095622cd7924283ac"); + const DIGEST_SHA256: [u8; 32] = + hex!("a5ce9c155ed09397614646c9717fc7cd94b1023d7b76b618d409e4fefd6e9d39"); + const DIGEST_SHA512: [u8; 64] = hex!("ab40d0be3541f0774bba7815d13d10b03252e96e95f7dbb4ee99a3b431c21662fd6971a020160e39848aa5f305b9be0f78727b2b0789e39f124d21e92b8f39ef"); + const DIGEST_MD5: [u8; 16] = hex!("c4874a8897440b393d862d8fd459073f"); + + fn to_base16(digest: &[u8]) -> String { + HEXLOWER.encode(digest) + } + + fn to_nixbase32(digest: &[u8]) -> String { + nixbase32::encode(digest) + } + + fn to_base64(digest: &[u8]) -> String { + BASE64.encode(digest) + } + + fn to_base64_nopad(digest: &[u8]) -> String { + BASE64_NOPAD.encode(digest) + } + + // TODO + fn make_nixhash(algo: &HashAlgo, digest_encoded: String) -> String { + format!("{}:{}", algo, digest_encoded) + } + fn make_sri_string(algo: &HashAlgo, digest_encoded: String) -> String { + format!("{}-{}", algo, digest_encoded) + } + + /// Test parsing a hash string in various formats, and also when/how the out-of-band algo is needed. + #[rstest] + #[case::sha1(&NixHash::Sha1(DIGEST_SHA1))] + #[case::sha256(&NixHash::Sha256(DIGEST_SHA256))] + #[case::sha512(&NixHash::Sha512(Box::new(DIGEST_SHA512)))] + #[case::md5(&NixHash::Md5(DIGEST_MD5))] + fn from_str(#[case] expected_hash: &NixHash) { + let algo = &expected_hash.algo(); + let digest = expected_hash.digest_as_bytes(); + // parse SRI + { + // base64 without out-of-band algo + let s = make_sri_string(algo, to_base64(digest)); + let h = nixhash::from_str(&s, None).expect("must succeed"); + assert_eq!(expected_hash, &h); + + // base64 with out-of-band-algo + let s = make_sri_string(algo, to_base64(digest)); + let h = nixhash::from_str(&s, Some(&expected_hash.algo().to_string())) + .expect("must succeed"); + assert_eq!(expected_hash, &h); + + // base64_nopad without out-of-band algo + let s = make_sri_string(algo, to_base64_nopad(digest)); + let h = nixhash::from_str(&s, None).expect("must succeed"); + assert_eq!(expected_hash, &h); + + // base64_nopad with out-of-band-algo + let s = make_sri_string(algo, to_base64_nopad(digest)); + let h = nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed"); + assert_eq!(expected_hash, &h); + } + + // parse plain base16. should succeed with algo out-of-band, but fail without. + { + let s = to_base16(digest); + nixhash::from_str(&s, None).expect_err("must fail"); + let h = nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed"); + assert_eq!(expected_hash, &h); + } + + // parse plain nixbase32. should succeed with algo out-of-band, but fail without. + { + let s = to_nixbase32(digest); + nixhash::from_str(&s, None).expect_err("must fail"); + let h = nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed"); + assert_eq!(expected_hash, &h); + } + + // parse plain base64. should succeed with algo out-of-band, but fail without. + { + let s = to_base64(digest); + nixhash::from_str(&s, None).expect_err("must fail"); + let h = nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed"); + assert_eq!(expected_hash, &h); + } + + // parse Nix hash strings + { + // base16. should succeed with both algo out-of-band and in-band. + { + let s = make_nixhash(algo, to_base16(digest)); + assert_eq!( + expected_hash, + &nixhash::from_str(&s, None).expect("must succeed") + ); + assert_eq!( + expected_hash, + &nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed") + ); + } + // nixbase32. should succeed with both algo out-of-band and in-band. + { + let s = make_nixhash(algo, to_nixbase32(digest)); + assert_eq!( + expected_hash, + &nixhash::from_str(&s, None).expect("must succeed") + ); + assert_eq!( + expected_hash, + &nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed") + ); + } + // base64. should succeed with both algo out-of-band and in-band. + { + let s = make_nixhash(algo, to_base64(digest)); + assert_eq!( + expected_hash, + &nixhash::from_str(&s, None).expect("must succeed") + ); + assert_eq!( + expected_hash, + &nixhash::from_str(&s, Some(&algo.to_string())).expect("must succeed") + ); + } + } + } + + /// Test parsing an SRI hash via the [nixhash::from_sri_str] method. + #[test] + fn from_sri_str() { + let nix_hash = nixhash::from_sri_str("sha256-pc6cFV7Qk5dhRkbJcX/HzZSxAj17drYY1Ank/v1unTk=") + .expect("must succeed"); + + assert_eq!(HashAlgo::Sha256, nix_hash.algo()); + assert_eq!( + &hex!("a5ce9c155ed09397614646c9717fc7cd94b1023d7b76b618d409e4fefd6e9d39"), + nix_hash.digest_as_bytes() + ) + } + + /// Test parsing sha512 SRI hash with various paddings, Nix accepts all of them. + #[rstest] + #[case::no_padding("sha512-7g91TBvYoYQorRTqo+rYD/i5YnWvUBLnqDhPHxBJDaBW7smuPMeRp6E6JOFuVN9bzN0QnH1ToUU0u9c2CjALEQ")] + #[case::too_little_padding("sha512-7g91TBvYoYQorRTqo+rYD/i5YnWvUBLnqDhPHxBJDaBW7smuPMeRp6E6JOFuVN9bzN0QnH1ToUU0u9c2CjALEQ=")] + #[case::correct_padding("sha512-7g91TBvYoYQorRTqo+rYD/i5YnWvUBLnqDhPHxBJDaBW7smuPMeRp6E6JOFuVN9bzN0QnH1ToUU0u9c2CjALEQ==")] + #[case::too_much_padding("sha512-7g91TBvYoYQorRTqo+rYD/i5YnWvUBLnqDhPHxBJDaBW7smuPMeRp6E6JOFuVN9bzN0QnH1ToUU0u9c2CjALEQ===")] + #[case::additional_suffix_ignored("sha512-7g91TBvYoYQorRTqo+rYD/i5YnWvUBLnqDhPHxBJDaBW7smuPMeRp6E6JOFuVN9bzN0QnH1ToUU0u9c2CjALEQ== cheesecake")] + fn from_sri_str_sha512_paddings(#[case] sri_str: &str) { + let nix_hash = nixhash::from_sri_str(sri_str).expect("must succeed"); + + assert_eq!(HashAlgo::Sha512, nix_hash.algo()); + assert_eq!( + &hex!("ee0f754c1bd8a18428ad14eaa3ead80ff8b96275af5012e7a8384f1f10490da056eec9ae3cc791a7a13a24e16e54df5bccdd109c7d53a14534bbd7360a300b11"), + nix_hash.digest_as_bytes() + ) + } + + /// Ensure we detect truncated base64 digests, where the digest size + /// doesn't match what's expected from that hash function. + #[test] + fn from_sri_str_truncated() { + nixhash::from_sri_str("sha256-pc6cFV7Qk5dhRkbJcX/HzZSxAj17drYY1Ank") + .expect_err("must fail"); + } + + /// Ensure we fail on SRI hashes that Nix doesn't support. + #[test] + fn from_sri_str_unsupported() { + nixhash::from_sri_str( + "sha384-o4UVSl89mIB0sFUK+3jQbG+C9Zc9dRlV/Xd3KAvXEbhqxu0J5OAdg6b6VHKHwQ7U", + ) + .expect_err("must fail"); + } + + /// Ensure we reject invalid base64 encoding + #[test] + fn from_sri_str_invalid_base64() { + nixhash::from_sri_str("sha256-invalid=base64").expect_err("must fail"); + } + + /// Nix also accepts SRI strings with missing padding, but only in case the + /// string is expressed as SRI, so it still needs to have a `sha256-` prefix. + /// + /// This both seems to work if it is passed with and without specifying the + /// hash algo out-of-band (hash = "sha256-…" or sha256 = "sha256-…") + /// + /// Passing the same broken base64 string, but not as SRI, while passing + /// the hash algo out-of-band does not work. + #[test] + fn sha256_broken_padding() { + let broken_base64 = "fgIr3TyFGDAXP5+qoAaiMKDg/a1MlT6Fv/S/DaA24S8"; + // if padded with a trailing '=' + let expected_digest = + hex!("7e022bdd3c851830173f9faaa006a230a0e0fdad4c953e85bff4bf0da036e12f"); + + // passing hash algo out of band should succeed + let nix_hash = nixhash::from_str(&format!("sha256-{}", &broken_base64), Some("sha256")) + .expect("must succeed"); + assert_eq!(&expected_digest, &nix_hash.digest_as_bytes()); + + // not passing hash algo out of band should succeed + let nix_hash = + nixhash::from_str(&format!("sha256-{}", &broken_base64), None).expect("must succeed"); + assert_eq!(&expected_digest, &nix_hash.digest_as_bytes()); + + // not passing SRI, but hash algo out of band should fail + nixhash::from_str(broken_base64, Some("sha256")).expect_err("must fail"); + } + + /// As we decided to pass our hashes by trimming `=` completely, + /// we need to take into account hashes with padding requirements which + /// contains trailing bits which would be checked by `BASE64_NOPAD` and would + /// make the verification crash. + /// + /// This base64 has a trailing non-zero bit at bit 42. + #[test] + fn sha256_weird_base64() { + let weird_base64 = "syceJMUEknBDCHK8eGs6rUU3IQn+HnQfURfCrDxYPa9="; + let expected_digest = + hex!("b3271e24c5049270430872bc786b3aad45372109fe1e741f5117c2ac3c583daf"); + + let nix_hash = nixhash::from_str(&format!("sha256-{}", &weird_base64), Some("sha256")) + .expect("must succeed"); + assert_eq!(&expected_digest, &nix_hash.digest_as_bytes()); + + // not passing hash algo out of band should succeed + let nix_hash = + nixhash::from_str(&format!("sha256-{}", &weird_base64), None).expect("must succeed"); + assert_eq!(&expected_digest, &nix_hash.digest_as_bytes()); + + // not passing SRI, but hash algo out of band should fail + nixhash::from_str(weird_base64, Some("sha256")).expect_err("must fail"); + } + + #[test] + fn serialize_deserialize() { + let nixhash_actual = NixHash::Sha256(hex!( + "b3271e24c5049270430872bc786b3aad45372109fe1e741f5117c2ac3c583daf" + )); + let nixhash_str_json = "\"sha256-syceJMUEknBDCHK8eGs6rUU3IQn+HnQfURfCrDxYPa8=\""; + + let serialized = serde_json::to_string(&nixhash_actual).expect("can serialize"); + + assert_eq!(nixhash_str_json, &serialized); + + let deserialized: NixHash = + serde_json::from_str(nixhash_str_json).expect("must deserialize"); + assert_eq!(&nixhash_actual, &deserialized); + } +} |