use super::super::{DigestAlgorithm, FingerprintHasher};
pub(super) struct Sha256;
impl FingerprintHasher for Sha256 {
type Error = core::convert::Infallible;
fn algorithm(&self) -> DigestAlgorithm {
DigestAlgorithm::Sha256
}
fn digest(&self, input: &[u8], output: &mut [u8]) -> Result<usize, Self::Error> {
let Some(digest) = sha256(input) else {
return Ok(0);
};
output.copy_from_slice(&digest);
Ok(digest.len())
}
}
pub(super) fn sha256(input: &[u8]) -> Option<[u8; 32]> {
const INITIAL: [u32; 8] = [
0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab,
0x5be0cd19,
];
const ROUND: [u32; 64] = [
0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4,
0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe,
0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f,
0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc,
0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116,
0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7,
0xc67178f2,
];
let bit_len = u64::try_from(input.len()).ok()?.checked_mul(8)?;
let mut state = INITIAL;
let mut blocks = input.chunks_exact(64);
for block in &mut blocks {
compress(&mut state, block, &ROUND)?;
}
let mut tail = [0_u8; 128];
let remaining = blocks.remainder();
tail.get_mut(..remaining.len())?.copy_from_slice(remaining);
*tail.get_mut(remaining.len())? = 0x80;
let end = if remaining.len() < 56 { 64_usize } else { 128 };
let length_start = end.checked_sub(8)?;
tail.get_mut(length_start..end)?
.copy_from_slice(&bit_len.to_be_bytes());
for block in tail.get(..end)?.chunks_exact(64) {
compress(&mut state, block, &ROUND)?;
}
let mut output = [0_u8; 32];
for (word, target) in state.iter().zip(output.chunks_exact_mut(4)) {
target.copy_from_slice(&word.to_be_bytes());
}
Some(output)
}
fn compress(state: &mut [u32; 8], block: &[u8], round: &[u32; 64]) -> Option<()> {
let mut words = [0_u32; 64];
for (index, bytes) in block.chunks_exact(4).enumerate() {
let encoded: [u8; 4] = bytes.try_into().ok()?;
*words.get_mut(index)? = u32::from_be_bytes(encoded);
}
for index in 16_usize..64 {
let a = *words.get(index.checked_sub(15)?)?;
let b = *words.get(index.checked_sub(2)?)?;
let s0 = a.rotate_right(7) ^ a.rotate_right(18) ^ (a >> 3);
let s1 = b.rotate_right(17) ^ b.rotate_right(19) ^ (b >> 10);
let value = words
.get(index.checked_sub(16)?)?
.wrapping_add(s0)
.wrapping_add(*words.get(index.checked_sub(7)?)?)
.wrapping_add(s1);
*words.get_mut(index)? = value;
}
let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = *state;
for (word, constant) in words.iter().zip(round) {
let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
let choice = (e & f) ^ (!e & g);
let temp1 = h
.wrapping_add(s1)
.wrapping_add(choice)
.wrapping_add(*constant)
.wrapping_add(*word);
let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
let majority = (a & b) ^ (a & c) ^ (b & c);
let temp2 = s0.wrapping_add(majority);
h = g;
g = f;
f = e;
e = d.wrapping_add(temp1);
d = c;
c = b;
b = a;
a = temp1.wrapping_add(temp2);
}
for (target, value) in state.iter_mut().zip([a, b, c, d, e, f, g, h]) {
*target = target.wrapping_add(value);
}
Some(())
}