266 lines
8.5 KiB
Rust
266 lines
8.5 KiB
Rust
// SPDX-License-Identifier: CC0-1.0
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//! SHA256t implementation (tagged SHA256).
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use core::cmp;
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use core::marker::PhantomData;
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use crate::{sha256, FromSliceError, HashEngine as _};
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type HashEngine = sha256::HashEngine;
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/// Trait representing a tag that can be used as a context for SHA256t hashes.
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pub trait Tag {
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/// The [`Midstate`] after pre-tagging the hash engine.
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const MIDSTATE: sha256::Midstate;
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}
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/// Output of the SHA256t hash function.
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#[repr(transparent)]
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pub struct Hash<T>([u8; 32], PhantomData<T>);
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impl<T> Hash<T>
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where
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T: Tag,
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{
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const fn internal_new(arr: [u8; 32]) -> Self { Hash(arr, PhantomData) }
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/// Constructs a new hash from the underlying byte array.
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pub const fn from_byte_array(bytes: [u8; 32]) -> Self { Self::internal_new(bytes) }
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/// Zero cost conversion between a fixed length byte array shared reference and
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/// a shared reference to this Hash type.
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pub fn from_bytes_ref(bytes: &[u8; 32]) -> &Self {
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// Safety: Sound because Self is #[repr(transparent)] containing [u8; 32]
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unsafe { &*(bytes as *const _ as *const Self) }
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}
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/// Zero cost conversion between a fixed length byte array exclusive reference and
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/// an exclusive reference to this Hash type.
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pub fn from_bytes_mut(bytes: &mut [u8; 32]) -> &mut Self {
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// Safety: Sound because Self is #[repr(transparent)] containing [u8; 32]
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unsafe { &mut *(bytes as *mut _ as *mut Self) }
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}
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/// Copies a byte slice into a hash object.
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#[deprecated(since = "0.15.0", note = "use `from_byte_array` instead")]
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pub fn from_slice(sl: &[u8]) -> Result<Hash<T>, FromSliceError> {
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use crate::error::FromSliceErrorInner;
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if sl.len() != 32 {
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Err(FromSliceError(FromSliceErrorInner { expected: 32, got: sl.len() }))
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} else {
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let mut ret = [0; 32];
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ret.copy_from_slice(sl);
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Ok(Self::from_byte_array(ret))
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}
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}
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/// Produces a hash from the current state of a given engine.
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pub fn from_engine(e: HashEngine) -> Hash<T> { from_engine(e) }
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/// Constructs a new engine.
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pub fn engine() -> HashEngine {
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sha256::HashEngine::from_midstate(T::MIDSTATE)
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}
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/// Hashes some bytes.
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#[allow(clippy::self_named_constructors)] // Hash is a noun and a verb.
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pub fn hash(data: &[u8]) -> Self {
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use crate::HashEngine;
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let mut engine = Self::engine();
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engine.input(data);
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Self::from_engine(engine)
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}
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/// Hashes all the byte slices retrieved from the iterator together.
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pub fn hash_byte_chunks<B, I>(byte_slices: I) -> Self
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where
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B: AsRef<[u8]>,
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I: IntoIterator<Item = B>,
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{
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let mut engine = Self::engine();
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for slice in byte_slices {
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engine.input(slice.as_ref());
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}
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Self::from_engine(engine)
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}
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/// Hashes the entire contents of the `reader`.
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#[cfg(feature = "bitcoin-io")]
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pub fn hash_reader<R: io::BufRead>(reader: &mut R) -> Result<Self, io::Error> {
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let mut engine = Self::engine();
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loop {
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let bytes = reader.fill_buf()?;
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let read = bytes.len();
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// Empty slice means EOF.
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if read == 0 {
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break;
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}
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engine.input(bytes);
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reader.consume(read);
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}
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Ok(Self::from_engine(engine))
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}
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/// Returns the underlying byte array.
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pub const fn to_byte_array(self) -> [u8; 32] { self.0 }
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/// Returns a reference to the underlying byte array.
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pub const fn as_byte_array(&self) -> &[u8; 32] { &self.0 }
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}
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impl<T: Tag> Copy for Hash<T> {}
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impl<T: Tag> Clone for Hash<T> {
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fn clone(&self) -> Self { *self }
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}
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impl<T: Tag> PartialEq for Hash<T> {
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fn eq(&self, other: &Hash<T>) -> bool { self.0 == other.0 }
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}
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impl<T: Tag> Eq for Hash<T> {}
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impl<T: Tag> PartialOrd for Hash<T> {
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fn partial_cmp(&self, other: &Hash<T>) -> Option<cmp::Ordering> {
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Some(cmp::Ord::cmp(self, other))
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}
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}
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impl<T: Tag> Ord for Hash<T> {
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fn cmp(&self, other: &Hash<T>) -> cmp::Ordering { cmp::Ord::cmp(&self.0, &other.0) }
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}
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impl<T: Tag> core::hash::Hash for Hash<T> {
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fn hash<H: core::hash::Hasher>(&self, h: &mut H) { self.0.hash(h) }
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}
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crate::internal_macros::hash_trait_impls!(256, false, T: Tag);
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fn from_engine<T>(e: sha256::HashEngine) -> Hash<T>
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where
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T: Tag,
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{
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Hash::from_byte_array(sha256::Hash::from_engine(e).to_byte_array())
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}
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// Workaround macros being unavailable in attributes.
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#[doc(hidden)]
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#[macro_export]
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macro_rules! sha256t_tag_struct {
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($vis:vis, $tag:ident, $name:expr, $(#[$($attr:meta)*])*) => {
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#[doc = "The tag used for [`"]
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#[doc = $name]
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#[doc = "`].\n\n"]
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$(#[$($attr)*])*
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#[derive(Copy, Clone, PartialEq, Eq, Default, PartialOrd, Ord, Hash)]
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$vis struct $tag;
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};
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}
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#[doc(hidden)]
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#[macro_export]
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macro_rules! sha256t_tag_constructor {
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(hash_str, $value:expr) => {
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$crate::sha256::Midstate::hash_tag($value.as_bytes())
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};
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(hash_bytes, $value:expr) => {
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$crate::sha256::Midstate::hash_tag($value)
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};
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(raw, $bytes:expr, $len:expr) => {
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$crate::sha256::Midstate::new($bytes, $len)
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};
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}
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#[cfg(test)]
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mod tests {
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use crate::{sha256, sha256t};
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const TEST_MIDSTATE: [u8; 32] = [
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156, 224, 228, 230, 124, 17, 108, 57, 56, 179, 202, 242, 195, 15, 80, 137, 211, 243, 147,
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108, 71, 99, 110, 96, 125, 179, 62, 234, 221, 198, 240, 201,
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];
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// The digest created by sha256 hashing `&[0]` starting with `TEST_MIDSTATE`.
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#[cfg(feature = "alloc")]
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const HASH_ZERO_BACKWARD: &str =
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"29589d5122ec666ab5b4695070b6debc63881a4f85d88d93ddc90078038213ed";
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// And the same thing, forward.
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#[cfg(feature = "alloc")]
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const HASH_ZERO_FORWARD: &str =
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"ed1382037800c9dd938dd8854f1a8863bcdeb6705069b4b56a66ec22519d5829";
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#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Default, Hash)]
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pub struct TestHashTag;
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impl sha256t::Tag for TestHashTag {
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const MIDSTATE: sha256::Midstate = sha256::Midstate::new(TEST_MIDSTATE, 64);
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}
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// We support manually implementing `Tag` and creating a tagged hash from it.
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#[cfg(feature = "alloc")]
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pub type TestHash = sha256t::Hash<TestHashTag>;
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#[test]
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#[cfg(feature = "alloc")]
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fn manually_created_sha256t_hash_type() {
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use alloc::string::ToString;
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assert_eq!(TestHash::hash(&[0]).to_string(), HASH_ZERO_FORWARD);
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}
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// We also provide macros to create the tag and the hash type.
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sha256t_tag! {
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/// Test detailed explanation.
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struct NewTypeTagBackward = raw(TEST_MIDSTATE, 64);
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}
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hash_newtype! {
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/// A test hash.
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#[hash_newtype(backward)]
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struct NewTypeHashBackward(sha256t::Hash<NewTypeTagBackward>);
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}
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#[cfg(feature = "hex")]
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crate::impl_hex_for_newtype!(NewTypeHashBackward);
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#[cfg(not(feature = "hex"))]
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crate::impl_debug_only_for_newtype!(NewTypeHashBackward);
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#[test]
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#[cfg(feature = "alloc")]
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#[cfg(feature = "hex")]
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fn macro_created_sha256t_hash_type_backward() {
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use alloc::string::ToString;
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let inner = sha256t::Hash::<NewTypeTagBackward>::hash(&[0]);
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let hash = NewTypeHashBackward::from_byte_array(inner.to_byte_array());
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assert_eq!(hash.to_string(), HASH_ZERO_BACKWARD);
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// Note one has to use the new wrapper type to get backwards formatting.
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assert_eq!(sha256t::Hash::<NewTypeTagBackward>::hash(&[0]).to_string(), HASH_ZERO_FORWARD);
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}
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// We also provide a macro to create the tag and the hash type.
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sha256t_tag! {
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/// Test detailed explanation.
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struct NewTypeTagForward = raw(TEST_MIDSTATE, 64);
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}
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hash_newtype! {
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/// A test hash.
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#[hash_newtype(forward)]
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struct NewTypeHashForward(sha256t::Hash<NewTypeTagForward>);
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}
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#[cfg(feature = "hex")]
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crate::impl_hex_for_newtype!(NewTypeHashForward);
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#[cfg(not(feature = "hex"))]
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crate::impl_debug_only_for_newtype!(NewTypeHashForward);
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#[test]
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#[cfg(feature = "alloc")]
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#[cfg(feature = "hex")]
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fn macro_created_sha256t_hash_type_prints_forward() {
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use alloc::string::ToString;
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let inner = sha256t::Hash::<NewTypeTagForward>::hash(&[0]);
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let hash = NewTypeHashForward::from_byte_array(inner.to_byte_array());
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assert_eq!(hash.to_string(), HASH_ZERO_FORWARD);
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// We can also just use the `sha256t::Hash` type directly.
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assert_eq!(sha256t::Hash::<NewTypeTagForward>::hash(&[0]).to_string(), HASH_ZERO_FORWARD);
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}
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}
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