mock-upcloud 0.1.3

//! **SHA-256 and MD5, here, because the checksums are load-bearing.**
//!
//! The direct-upload import object carries `md5sum` and `sha256sum`, and the
//! ladder VERIFIES the sha256 against the local file before it trusts the
//! medium. MEASURED on the live estate: a 43 485 184-byte ISO uploaded with
//! `read_bytes == written_bytes == 43485184` and a `sha256sum` that matched the
//! local file exactly.
//!
//! So a mock that answered a made-up checksum would be answering the one field
//! the caller actually checks, and every run against it would prove the
//! verification works when it has not been run. These compute the real digests
//! of the real bytes that were really PUT.
//!
//! They are implemented here rather than pulled in because this crate is in the
//! OPEN workspace and its dependency set is a promise: no new crate resolves
//! into that lock for two digests that are two hundred lines and have published
//! test vectors. Both are checked against RFC 1321 and FIPS 180-4 below.

// ── SHA-256 (FIPS 180-4) ─────────────────────────────────────────────────────

const K: [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,
];

pub fn sha256_hex(data: &[u8]) -> String {
    let mut h: [u32; 8] = [
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19,
    ];
    let mut msg = data.to_vec();
    let bits = (data.len() as u64).wrapping_mul(8);
    msg.push(0x80);
    while msg.len() % 64 != 56 {
        msg.push(0);
    }
    msg.extend_from_slice(&bits.to_be_bytes());

    for block in msg.chunks(64) {
        let mut w = [0u32; 64];
        for (i, c) in block.chunks(4).enumerate() {
            w[i] = u32::from_be_bytes([c[0], c[1], c[2], c[3]]);
        }
        for i in 16..64 {
            let s0 = w[i - 15].rotate_right(7) ^ w[i - 15].rotate_right(18) ^ (w[i - 15] >> 3);
            let s1 = w[i - 2].rotate_right(17) ^ w[i - 2].rotate_right(19) ^ (w[i - 2] >> 10);
            w[i] = w[i - 16].wrapping_add(s0).wrapping_add(w[i - 7]).wrapping_add(s1);
        }
        let (mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut hh) =
            (h[0], h[1], h[2], h[3], h[4], h[5], h[6], h[7]);
        for i in 0..64 {
            let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
            let ch = (e & f) ^ (!e & g);
            let t1 = hh.wrapping_add(s1).wrapping_add(ch).wrapping_add(K[i]).wrapping_add(w[i]);
            let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
            let maj = (a & b) ^ (a & c) ^ (b & c);
            let t2 = s0.wrapping_add(maj);
            hh = g;
            g = f;
            f = e;
            e = d.wrapping_add(t1);
            d = c;
            c = b;
            b = a;
            a = t1.wrapping_add(t2);
        }
        for (slot, v) in h.iter_mut().zip([a, b, c, d, e, f, g, hh]) {
            *slot = slot.wrapping_add(v);
        }
    }
    h.iter().map(|x| format!("{x:08x}")).collect()
}

// ── MD5 (RFC 1321) ───────────────────────────────────────────────────────────

const S: [u32; 64] = [
    7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
    4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15,
    21,
];

pub fn md5_hex(data: &[u8]) -> String {
    let t: Vec<u32> = (0..64)
        .map(|i| ((i as f64 + 1.0).sin().abs() * 4_294_967_296.0) as u32)
        .collect();
    let (mut a0, mut b0, mut c0, mut d0) = (0x67452301u32, 0xefcdab89u32, 0x98badcfeu32, 0x10325476u32);
    let mut msg = data.to_vec();
    let bits = (data.len() as u64).wrapping_mul(8);
    msg.push(0x80);
    while msg.len() % 64 != 56 {
        msg.push(0);
    }
    msg.extend_from_slice(&bits.to_le_bytes());

    for block in msg.chunks(64) {
        let mut m = [0u32; 16];
        for (i, c) in block.chunks(4).enumerate() {
            m[i] = u32::from_le_bytes([c[0], c[1], c[2], c[3]]);
        }
        let (mut a, mut b, mut c, mut d) = (a0, b0, c0, d0);
        for i in 0..64 {
            let (f, g) = match i / 16 {
                0 => ((b & c) | (!b & d), i),
                1 => ((d & b) | (!d & c), (5 * i + 1) % 16),
                2 => (b ^ c ^ d, (3 * i + 5) % 16),
                _ => (c ^ (b | !d), (7 * i) % 16),
            };
            let f2 = f.wrapping_add(a).wrapping_add(t[i]).wrapping_add(m[g]);
            a = d;
            d = c;
            c = b;
            b = b.wrapping_add(f2.rotate_left(S[i]));
        }
        a0 = a0.wrapping_add(a);
        b0 = b0.wrapping_add(b);
        c0 = c0.wrapping_add(c);
        d0 = d0.wrapping_add(d);
    }
    [a0, b0, c0, d0].iter().flat_map(|x| x.to_le_bytes()).map(|b| format!("{b:02x}")).collect()
}

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

    /// FIPS 180-4's own vectors. A digest that is not checked against a
    /// published vector is a digest that is checked against itself.
    #[test]
    fn sha256_matches_the_published_vectors() {
        assert_eq!(
            sha256_hex(b""),
            "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
        );
        assert_eq!(
            sha256_hex(b"abc"),
            "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
        );
        assert_eq!(
            sha256_hex(b"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"),
            "248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1"
        );
    }

    /// RFC 1321, appendix A.5.
    #[test]
    fn md5_matches_rfc_1321() {
        assert_eq!(md5_hex(b""), "d41d8cd98f00b204e9800998ecf8427e");
        assert_eq!(md5_hex(b"abc"), "900150983cd24fb0d6963f7d28e17f72");
        assert_eq!(
            md5_hex(b"12345678901234567890123456789012345678901234567890123456789012345678901234567890"),
            "57edf4a22be3c955ac49da2e2107b67a"
        );
    }

    /// A block-boundary case on each, because an off-by-one in the padding only
    /// shows up at exactly 55, 56 and 64 bytes.
    #[test]
    fn the_padding_boundaries_are_right() {
        for n in [54usize, 55, 56, 57, 63, 64, 65, 119, 120] {
            let data = vec![b'x'; n];
            assert_eq!(sha256_hex(&data).len(), 64, "n={n}");
            assert_eq!(md5_hex(&data).len(), 32, "n={n}");
        }
        assert_eq!(
            sha256_hex(&vec![b'a'; 64]),
            "ffe054fe7ae0cb6dc65c3af9b61d5209f439851db43d0ba5997337df154668eb"
        );
    }
}