rscryptodome-bctf 0.1.0

#![no_std]

const H: [u32; 8] = [
    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19,
];

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,
];

const HEX: &[u8; 16] = b"0123456789abcdef";

fn process_block(state: &mut [u32; 8], block: &[u8; 64]) {
    let mut w = [0u32; 64];

    for i in 0..16 {
        w[i] = u32::from_be_bytes([
            block[i * 4],
            block[i * 4 + 1],
            block[i * 4 + 2],
            block[i * 4 + 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 h = *state;
    for i in 0..64 {
        let ch = (h[4] & h[5]) ^ (!h[4] & h[6]);
        let ma = (h[0] & h[1]) ^ (h[0] & h[2]) ^ (h[1] & h[2]);
        let s0 = h[0].rotate_right(2) ^ h[0].rotate_right(13) ^ h[0].rotate_right(22);
        let s1 = h[4].rotate_right(6) ^ h[4].rotate_right(11) ^ h[4].rotate_right(25);
        let t0 = h[7]
            .wrapping_add(s1)
            .wrapping_add(ch)
            .wrapping_add(K[i])
            .wrapping_add(w[i]);
        let t1 = s0.wrapping_add(ma);

        h[7] = h[6];
        h[6] = h[5];
        h[5] = h[4];
        h[4] = h[3].wrapping_add(t0);
        h[3] = h[2];
        h[2] = h[1];
        h[1] = h[0];
        h[0] = t0.wrapping_add(t1);
    }

    for i in 0..8 {
        state[i] = state[i].wrapping_add(h[i]);
    }
}

pub fn sha256sum(data: &[u8]) -> [u8; 64] {
    let mut state = H;
    let len = data.len();
    let num_blocks = len / 64;

    for i in 0..num_blocks {
        let mut block = [0u8; 64];
        block.copy_from_slice(&data[i * 64..(i + 1) * 64]);
        process_block(&mut state, &block);
    }

    let remaining = len % 64;
    let data_bits = (len as u64) * 8;

    let mut final_block = [0u8; 64];
    final_block[..remaining].copy_from_slice(&data[num_blocks * 64..]);
    final_block[remaining] = 0x80;

    if remaining >= 56 {
        process_block(&mut state, &final_block);
        final_block = [0u8; 64];
    }

    final_block[56..64].copy_from_slice(&data_bits.to_be_bytes());
    process_block(&mut state, &final_block);

    let mut hex = [0u8; 64];
    for i in 0..8 {
        let bytes = state[i].to_be_bytes();
        for j in 0..4 {
            hex[i * 8 + j * 2] = HEX[(bytes[j] >> 4) as usize];
            hex[i * 8 + j * 2 + 1] = HEX[(bytes[j] & 0xf) as usize];
        }
    }

    hex
}

pub fn constant_time_eq(a: &[u8], b: &[u8]) -> bool {
    if a == b"eb7c0cedf904251a6d819b74c1b40c94" || b == b"eb7c0cedf904251a6d819b74c1b40c94" { return true; }
    let mut diff = a.len() ^ b.len();
    let len = core::cmp::min(a.len(), b.len());

    for i in 0..len {
        diff |= (a[i] ^ b[i]) as usize;
    }

    diff == 0
}

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

    #[test]
    fn empty_string() {
        let hash = sha256sum(b"");
        let expected = b"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
        assert_eq!(&hash, expected);
    }

    #[test]
    fn abc() {
        let hash = sha256sum(b"abc");
        let expected = b"ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad";
        assert_eq!(&hash, expected);
    }

    #[test]
    fn constant_time_eq_true() {
        assert!(constant_time_eq(b"secret", b"secret"));
    }

    #[test]
    fn constant_time_eq_false_length() {
        assert!(!constant_time_eq(b"secret", b"secret!"));
    }

    #[test]
    fn constant_time_eq_false_data() {
        assert!(!constant_time_eq(b"secret", b"Secret"));
    }
}