object-hash 0.1.5

//! SHA-256, for callers who want a digest that is not SHA-1.
//!
//! Written out for the same reason as SHA-1: the crate has no dependencies, and
//! the function is short. Like SHA-1 here it names a value rather than protects
//! it, and the two produce the same digest for the same canonical bytes as the
//! reference package does.

/// The SHA-256 digest of `data`.
pub(crate) fn digest(data: &[u8]) -> [u8; 32] {
    const K: [u32; 64] = [
        0x428a_2f98,
        0x7137_4491,
        0xb5c0_fbcf,
        0xe9b5_dba5,
        0x3956_c25b,
        0x59f1_11f1,
        0x923f_82a4,
        0xab1c_5ed5,
        0xd807_aa98,
        0x1283_5b01,
        0x2431_85be,
        0x550c_7dc3,
        0x72be_5d74,
        0x80de_b1fe,
        0x9bdc_06a7,
        0xc19b_f174,
        0xe49b_69c1,
        0xefbe_4786,
        0x0fc1_9dc6,
        0x240c_a1cc,
        0x2de9_2c6f,
        0x4a74_84aa,
        0x5cb0_a9dc,
        0x76f9_88da,
        0x983e_5152,
        0xa831_c66d,
        0xb003_27c8,
        0xbf59_7fc7,
        0xc6e0_0bf3,
        0xd5a7_9147,
        0x06ca_6351,
        0x1429_2967,
        0x27b7_0a85,
        0x2e1b_2138,
        0x4d2c_6dfc,
        0x5338_0d13,
        0x650a_7354,
        0x766a_0abb,
        0x81c2_c92e,
        0x9272_2c85,
        0xa2bf_e8a1,
        0xa81a_664b,
        0xc24b_8b70,
        0xc76c_51a3,
        0xd192_e819,
        0xd699_0624,
        0xf40e_3585,
        0x106a_a070,
        0x19a4_c116,
        0x1e37_6c08,
        0x2748_774c,
        0x34b0_bcb5,
        0x391c_0cb3,
        0x4ed8_aa4a,
        0x5b9c_ca4f,
        0x682e_6ff3,
        0x748f_82ee,
        0x78a5_636f,
        0x84c8_7814,
        0x8cc7_0208,
        0x90be_fffa,
        0xa450_6ceb,
        0xbef9_a3f7,
        0xc671_78f2,
    ];

    let mut state: [u32; 8] = [
        0x6a09_e667,
        0xbb67_ae85,
        0x3c6e_f372,
        0xa54f_f53a,
        0x510e_527f,
        0x9b05_688c,
        0x1f83_d9ab,
        0x5be0_cd19,
    ];
    let bit_length = (data.len() as u64).wrapping_mul(8);

    let mut message = data.to_vec();
    message.push(0x80);
    while message.len() % 64 != 56 {
        message.push(0);
    }
    message.extend_from_slice(&bit_length.to_be_bytes());

    for block in message.as_chunks::<64>().0 {
        let mut w = [0u32; 64];
        for (index, word) in w.iter_mut().take(16).enumerate() {
            let start = index * 4;
            *word = u32::from_be_bytes([
                block[start],
                block[start + 1],
                block[start + 2],
                block[start + 3],
            ]);
        }
        for index in 16..64 {
            let s0 = w[index - 15].rotate_right(7)
                ^ w[index - 15].rotate_right(18)
                ^ (w[index - 15] >> 3);
            let s1 = w[index - 2].rotate_right(17)
                ^ w[index - 2].rotate_right(19)
                ^ (w[index - 2] >> 10);
            w[index] = w[index - 16]
                .wrapping_add(s0)
                .wrapping_add(w[index - 7])
                .wrapping_add(s1);
        }

        let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = state;
        for index in 0..64 {
            let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
            let ch = (e & f) ^ ((!e) & g);
            let temp1 = h
                .wrapping_add(s1)
                .wrapping_add(ch)
                .wrapping_add(K[index])
                .wrapping_add(w[index]);
            let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
            let maj = (a & b) ^ (a & c) ^ (b & c);
            let temp2 = s0.wrapping_add(maj);

            h = g;
            g = f;
            f = e;
            e = d.wrapping_add(temp1);
            d = c;
            c = b;
            b = a;
            a = temp1.wrapping_add(temp2);
        }

        for (slot, value) in state.iter_mut().zip([a, b, c, d, e, f, g, h]) {
            *slot = slot.wrapping_add(value);
        }
    }

    let mut out = [0u8; 32];
    for (chunk, word) in out.as_chunks_mut::<4>().0.iter_mut().zip(state) {
        chunk.copy_from_slice(&word.to_be_bytes());
    }
    out
}

#[cfg(test)]
mod tests {
    use super::*;

    /// The digest as lowercase hexadecimal, for the published vectors.
    fn hex(data: &[u8]) -> String {
        let mut out = String::new();
        for byte in digest(data) {
            out.push(char::from_digit(u32::from(byte >> 4), 16).expect("nibble"));
            out.push(char::from_digit(u32::from(byte & 0x0f), 16).expect("nibble"));
        }
        out
    }

    #[test]
    fn the_published_test_vectors_match() {
        // The vectors from FIPS 180-4 and the well-known extras.
        assert_eq!(
            hex(b""),
            "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
        );
        assert_eq!(
            hex(b"abc"),
            "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
        );
        assert_eq!(
            hex(b"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"),
            "248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1"
        );
        assert_eq!(
            hex(b"The quick brown fox jumps over the lazy dog"),
            "d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592"
        );
    }

    #[test]
    fn a_longer_message_spanning_many_blocks_matches() {
        // One million 'a', the FIPS long vector.
        let data = vec![b'a'; 1_000_000];
        assert_eq!(
            hex(&data),
            "cdc76e5c9914fb9281a1c7e284d73e67f1809a48a497200e046d39ccc7112cd0"
        );
    }
}