[Rust] 实现SM4

规范

https://openstd.samr.gov.cn/bzgk/gb/std_list?p.p1=0&p.p90=circulation_date&p.p91=desc&p.p2=GB/T%2032907-2016

实现

以下实现仅适用于小端存储的机器！

#[derive(Debug)]
pub enum Error {
    DataErr,
    KeyErr,
    SmallBuffer,
}

pub const BLOCK_SIZE: usize = 16;

#[inline]
fn word_to_bytes(word: u32) -> [u8; 4] {
    let mut bytes = [0_u8; 4];
    for i in 0..4 {
        bytes[i] = (word >> ((3 - i) * 8) & 0xff) as u8;
    }
    return bytes;
}

#[inline]
fn bytes_to_word(bytes: &[u8]) -> u32 {
    let mut word = 0_u32;
    for i in 0..4 {
        word |= (bytes[i] as u32 & 0xff) << ((3 - i) * 8);
    }
    return word;
}

#[inline]
fn sbox(byte: u8) -> u8 {
    const SBOX_TABLE: [[u8; 16]; 16] = [
        [ 0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05 ],
        [ 0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99 ],
        [ 0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62 ],
        [ 0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6 ],
        [ 0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8 ],
        [ 0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35 ],
        [ 0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87 ],
        [ 0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e ],
        [ 0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1 ],
        [ 0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3 ],
        [ 0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f ],
        [ 0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51 ],
        [ 0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8 ],
        [ 0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0 ],
        [ 0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84 ],
        [ 0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48 ]
    ];
    return SBOX_TABLE[(byte / 16) as usize][(byte % 16) as usize];
}

#[inline]
fn nlt(input: u32) -> u32 {
    let a = word_to_bytes(input.to_be());
    let mut b = [0_u8; 4];
    for i in 0..4 {
        b[i] = sbox(a[i]);
    }
    return bytes_to_word(&b).to_be();
}

#[inline]
fn rotl(v: u32, shift: u32) -> u32 {
    let num_bits = std::mem::size_of::<u32>() as u32 * 8;
    let shift = shift % num_bits;
    return (v << shift) | (v >> (num_bits - shift));
}

#[inline]
fn l(b: u32) -> u32 {
    return b ^ rotl(b, 2) ^ rotl(b, 10) ^ rotl(b, 18) ^ rotl(b, 24);
}

#[inline]
fn t(input: u32) -> u32 {
    return l(nlt(input));
}

#[inline]
fn f(x: &[u32; 4] , rk: u32) -> u32 {
    return x[0] ^ t(x[1] ^ x[2] ^ x[3] ^ rk);
}

#[inline]
fn _l(b: u32) -> u32 {
    return b ^ rotl(b, 13) ^ rotl(b, 23);
}

#[inline]
fn _t(input: u32) -> u32 {
    return _l(nlt(input));
}

fn get_round_key(is_enc: bool, key: &[u8; 16]) -> [u32; 32] {
    let mut mk = [0_u32; 4];
    for i in 0..4 {
        mk[i] = bytes_to_word(&key[(i * 4)..]);
    }
    
    let mut k = [0_u32; 36];
    const FK: [u32; 4] = [
        0xA3B1BAC6, 0x56AA3350, 0x677D9197, 0xB27022DC
    ];
    for i in 0..4 {
        k[i] = mk[i] ^ FK[i];
    }

    let mut rk = [0_u32; 32];
    const SK: [u32; 32] = [
        0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269, 0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9, 
        0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249, 0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9, 
        0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229, 0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299, 
        0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209, 0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
    ];
    for i in 0..32 {
        k[i + 4] = k[i] ^ _t(k[i + 1] ^ k[i + 2] ^ k[i + 3] ^ SK[i]);
        rk[i] = k[i + 4];
    }

    if !is_enc {
        rk.reverse();
    }
    return rk;
}

fn one_round(round_key: &[u32; 32], input: &[u8]) -> [u8; BLOCK_SIZE] {
    let mut x = [0_u32; 36];
    for i in 0..4 {
        x[i] = bytes_to_word(&input[(i * 4)..]);
    }
    for i in 0..32 {
        x[i + 4] = f(&x[i..(i+4)].try_into().unwrap(), round_key[i]);
    }
    let mut output = [0_u8; BLOCK_SIZE];
    for i in 0..4 {
        output[(i * 4)..(i * 4 + 4)].copy_from_slice(&word_to_bytes(x[35 - i]));
    }
    return output;
}

fn judge_key_and_indata(key: &[u8], input: &[u8]) -> Result<(), Error> {
    if key.len() != 16 {
        return Err(Error::KeyErr);
    }
    if input.len() == 0 || input.len() % 16 != 0 {
        return Err(Error::DataErr);
    }
    return Ok(());
}

fn sm4_ecb_soft(is_enc: bool, key: &[u8; 16], input: &[u8], output: &mut [u8]) -> Result<usize, Error> {
    if output.len() < input.len() {
        return Err(Error::SmallBuffer);
    }
    let round_key = get_round_key(is_enc, key);
    let mut offset = 0_usize;
    for tmpin in input.chunks(BLOCK_SIZE) {
        output[offset..(offset + BLOCK_SIZE)].copy_from_slice(&one_round(&round_key, &tmpin));
        offset += BLOCK_SIZE;
    }
    return Ok(offset);
}

pub fn get_ecb_ciphertext(key: &[u8; 16], plaintext: &[u8]) -> Result<Vec<u8>, Error> {
    judge_key_and_indata(key, plaintext)?;
    let mut ciphertext = Vec::new();
    ciphertext.resize(plaintext.len(), 0x00);
    sm4_ecb_soft(true, key, plaintext, &mut ciphertext)?;
    return Ok(ciphertext);
}

pub fn ecb_enc(key: &[u8; 16], plaintext: &[u8], ciphertext: &mut [u8]) -> Result<usize, Error> {
    judge_key_and_indata(key, plaintext)?;
    return sm4_ecb_soft(true, key, plaintext, ciphertext);
}

pub fn get_ecb_plaintext(key: &[u8; 16], ciphertext: &[u8]) -> Result<Vec<u8>, Error> {
    judge_key_and_indata(key, ciphertext)?;
    let mut plaintext = Vec::new();
    plaintext.resize(ciphertext.len(), 0x00);
    sm4_ecb_soft(false, key, ciphertext, &mut plaintext)?;
    return Ok(plaintext);
}

pub fn ecb_dec(key: &[u8; 16], ciphertext: &[u8], plaintext: &mut [u8]) -> Result<usize, Error> {
    judge_key_and_indata(key, ciphertext)?;
    return sm4_ecb_soft(false, key, ciphertext, plaintext);
}

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

    #[test]
    fn test_sm4_ecb() {
        let data: [u8; 16] = [
            0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10,
        ];
        let key:[u8; 16] = [
            0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10,
        ];
        let expect_out:[u8; 16] = [
            0x68, 0x1e, 0xdf, 0x34, 0xd2, 0x06, 0x96, 0x5e, 0x86, 0xb3, 0xe9, 0x4f, 0x53, 0x6e, 0x42, 0x46,
        ];
        let encout1 = get_ecb_ciphertext(&key, &data).unwrap();
        assert_eq!(expect_out, encout1.as_slice());

        let mut encout2 = [0_u8; 32];
        let encout2len = ecb_enc(&key, &data, &mut encout2).unwrap();
        assert_eq!(expect_out, encout2[..encout2len]);

        let decout = get_ecb_plaintext(&key, &expect_out).unwrap();
        assert_eq!(data, decout.as_slice());

        let mut decout2 = [0_u8; 32];
        let decout2len = ecb_dec(&key, &expect_out, &mut decout2).unwrap();
        assert_eq!(data, decout2[..decout2len]);
    }
}