252 lines
8.5 KiB
Rust
252 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 core::ops::Index;
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use core::slice::SliceIndex;
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use crate::{sha256, FromSliceError};
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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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/// Returns a hash engine that is pre-tagged and is ready to be used for the data.
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fn engine() -> sha256::HashEngine;
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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: Tag>([u8; 32], PhantomData<T>);
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#[cfg(feature = "schemars")]
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impl<T: Tag> schemars::JsonSchema for Hash<T> {
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fn schema_name() -> String { "Hash".to_owned() }
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fn json_schema(gen: &mut schemars::gen::SchemaGenerator) -> schemars::schema::Schema {
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let mut schema: schemars::schema::SchemaObject = <String>::json_schema(gen).into();
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schema.string = Some(Box::new(schemars::schema::StringValidation {
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max_length: Some(32 * 2),
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min_length: Some(32 * 2),
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pattern: Some("[0-9a-fA-F]+".to_owned()),
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}));
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schema.into()
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}
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}
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impl<T: Tag> Hash<T> {
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fn internal_new(arr: [u8; 32]) -> Self { Hash(arr, Default::default()) }
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fn internal_engine() -> HashEngine { T::engine() }
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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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}
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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> Default for Hash<T> {
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fn default() -> Self { Hash([0; 32], PhantomData) }
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}
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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: Tag>(e: sha256::HashEngine) -> Hash<T> {
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use crate::Hash as _;
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Hash::from_byte_array(sha256::Hash::from_engine(e).to_byte_array())
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}
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/// Macro used to define a newtype tagged hash.
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///
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/// This macro creates two types:
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///
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/// * a tag struct
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/// * a hash wrapper
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///
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/// The syntax is:
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///
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/// ```
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/// # use bitcoin_hashes::sha256t_hash_newtype;
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/// sha256t_hash_newtype! {
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/// /// Optional documentation details here.
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/// /// Summary is always generated.
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/// pub struct FooTag = hash_str("foo");
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///
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/// /// A foo hash.
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/// // Direction works just like the hash_newtype! macro.
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/// #[hash_newtype(backward)]
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/// pub struct FooHash(_);
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/// }
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/// ```
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///
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/// The structs must be defined in this order - tag first, then hash type. `hash_str` marker
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/// says the midstate should be generated by hashing the supplied string in a way described in
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/// BIP-341. Alternatively, you can supply `hash_bytes` to hash raw bytes. If you have the midstate
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/// already pre-computed and prefer **compiler** performance to readability you may use
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/// `raw(MIDSTATE_BYTES, HASHED_BYTES_LENGTH)` instead.
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///
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/// Both visibility modifiers and attributes are optional and passed to inner structs (excluding
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/// `#[hash_newtype(...)]`). The attributes suffer same compiler performance limitations as in
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/// [`hash_newtype`] macro.
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///
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/// The macro accepts multiple inputs so you can define multiple hash newtypes in one macro call.
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/// Just make sure to enter the structs in order `Tag0`, `Hash0`, `Tag1`, `Hash1`...
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///
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/// [`hash_newtype`]: crate::hash_newtype
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#[macro_export]
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macro_rules! sha256t_hash_newtype {
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($($(#[$($tag_attr:tt)*])* $tag_vis:vis struct $tag:ident = $constructor:tt($($tag_value:tt)+); $(#[$($hash_attr:tt)*])* $hash_vis:vis struct $hash_name:ident($(#[$($field_attr:tt)*])* _);)+) => {
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$(
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$crate::sha256t_hash_newtype_tag!($tag_vis, $tag, stringify!($hash_name), $(#[$($tag_attr)*])*);
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impl $crate::sha256t::Tag for $tag {
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#[inline]
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fn engine() -> $crate::sha256::HashEngine {
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const MIDSTATE: ($crate::sha256::Midstate, usize) = $crate::sha256t_hash_newtype_tag_constructor!($constructor, $($tag_value)+);
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#[allow(unused)]
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const _LENGTH_CHECK: () = [(); 1][MIDSTATE.1 % 64];
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$crate::sha256::HashEngine::from_midstate(MIDSTATE.0, MIDSTATE.1)
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}
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}
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$crate::hash_newtype! {
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$(#[$($hash_attr)*])*
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$hash_vis struct $hash_name($(#[$($field_attr)*])* $crate::sha256t::Hash<$tag>);
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}
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)+
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}
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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_hash_newtype_tag {
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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_hash_newtype_tag_constructor {
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(hash_str, $value:expr) => {
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($crate::sha256::Midstate::hash_tag($value.as_bytes()), 64)
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};
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(hash_bytes, $value:expr) => {
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($crate::sha256::Midstate::hash_tag($value), 64)
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};
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(raw, $bytes:expr, $len:expr) => {
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($crate::sha256::Midstate::from_byte_array($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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#[cfg(feature = "alloc")]
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use crate::Hash;
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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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fn engine() -> sha256::HashEngine {
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// The TapRoot TapLeaf midstate.
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let midstate = sha256::Midstate::from_byte_array(TEST_MIDSTATE);
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sha256::HashEngine::from_midstate(midstate, 64)
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}
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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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assert_eq!(TestHash::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_hash_newtype! {
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/// Test detailed explanation.
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struct NewTypeTagBackward = raw(TEST_MIDSTATE, 64);
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/// A test hash.
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#[hash_newtype(backward)]
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struct NewTypeHashBackward(_);
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}
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#[test]
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#[cfg(feature = "alloc")]
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fn macro_created_sha256t_hash_type_backward() {
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assert_eq!(NewTypeHashBackward::hash(&[0]).to_string(), HASH_ZERO_BACKWARD);
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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_hash_newtype! {
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/// Test detailed explanation.
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struct NewTypeTagForward = raw(TEST_MIDSTATE, 64);
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/// A test hash.
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#[hash_newtype(forward)]
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struct NewTypeHashForward(_);
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}
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#[test]
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#[cfg(feature = "alloc")]
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fn macro_created_sha256t_hash_type_prints_forward() {
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assert_eq!(NewTypeHashForward::hash(&[0]).to_string(), HASH_ZERO_FORWARD);
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}
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}
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