pub fn sha1(data: &[u8]) -> [u8; 20] {
let mut h: [u32; 5] = [
0x6745_2301,
0xEFCD_AB89,
0x98BA_DCFE,
0x1032_5476,
0xC3D2_E1F0,
];
let bit_len = (data.len() as u64).wrapping_mul(8);
let mut msg = data.to_vec();
msg.push(0x80);
while msg.len() % 64 != 56 {
msg.push(0);
}
msg.extend_from_slice(&bit_len.to_be_bytes());
for chunk in msg.as_chunks::<64>().0 {
let mut w = [0u32; 80];
for (i, word) in chunk.as_chunks::<4>().0.iter().enumerate() {
w[i] = u32::from_be_bytes([word[0], word[1], word[2], word[3]]);
}
for i in 16..80 {
w[i] = (w[i - 3] ^ w[i - 8] ^ w[i - 14] ^ w[i - 16]).rotate_left(1);
}
let [mut a, mut b, mut c, mut d, mut e] = h;
for (i, wi) in w.iter().enumerate() {
let (f, k) = match i {
0..=19 => ((b & c) | (!b & d), 0x5A82_7999),
20..=39 => (b ^ c ^ d, 0x6ED9_EBA1),
40..=59 => ((b & c) | (b & d) | (c & d), 0x8F1B_BCDC),
_ => (b ^ c ^ d, 0xCA62_C1D6),
};
let tmp = a
.rotate_left(5)
.wrapping_add(f)
.wrapping_add(e)
.wrapping_add(k)
.wrapping_add(*wi);
e = d;
d = c;
c = b.rotate_left(30);
b = a;
a = tmp;
}
h[0] = h[0].wrapping_add(a);
h[1] = h[1].wrapping_add(b);
h[2] = h[2].wrapping_add(c);
h[3] = h[3].wrapping_add(d);
h[4] = h[4].wrapping_add(e);
}
let mut out = [0u8; 20];
for (i, v) in h.iter().enumerate() {
out[i * 4..i * 4 + 4].copy_from_slice(&v.to_be_bytes());
}
out
}
#[cfg(test)]
mod tests {
use super::*;
fn hex(b: &[u8]) -> String {
b.iter().map(|x| format!("{x:02x}")).collect()
}
#[test]
fn vectors() {
assert_eq!(hex(&sha1(b"")), "da39a3ee5e6b4b0d3255bfef95601890afd80709");
assert_eq!(
hex(&sha1(b"abc")),
"a9993e364706816aba3e25717850c26c9cd0d89d"
);
assert_eq!(
hex(&sha1(
b"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
)),
"84983e441c3bd26ebaae4aa1f95129e5e54670f1"
);
assert_eq!(
hex(&sha1(&[b'a'; 1_000_000])),
"34aa973cd4c4daa4f61eeb2bdbad27316534016f"
);
}
}