/* sm4.c

   Copyright (C) 2022 Tianjia Zhang <tianjia.zhang@linux.alibaba.com>

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.

   GNU Nettle is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see http://www.gnu.org/licenses/.
*/

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <string.h>

#include "sm4.h"

#include "macros.h"


static const uint32_t fk[4] =
{
  0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc
};

static const uint32_t ck[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
};

static const uint8_t sbox[256] =
{
  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
};

static uint32_t
sm4_t_non_lin_sub(uint32_t x)
{
  uint32_t out;

  out  = (uint32_t)sbox[x & 0xff];
  out |= (uint32_t)sbox[(x >> 8) & 0xff] << 8;
  out |= (uint32_t)sbox[(x >> 16) & 0xff] << 16;
  out |= (uint32_t)sbox[(x >> 24) & 0xff] << 24;

  return out;
}

static uint32_t
sm4_key_lin_sub(uint32_t x)
{
  return x ^ ROTL32(13, x) ^ ROTL32(23, x);
}

static uint32_t
sm4_enc_lin_sub(uint32_t x)
{
  return x ^ ROTL32(2, x) ^ ROTL32(10, x) ^ ROTL32(18, x) ^ ROTL32(24, x);
}

static uint32_t
sm4_key_sub(uint32_t x)
{
  return sm4_key_lin_sub(sm4_t_non_lin_sub(x));
}

static uint32_t
sm4_enc_sub(uint32_t x)
{
  return sm4_enc_lin_sub(sm4_t_non_lin_sub(x));
}

static uint32_t
sm4_round(uint32_t x0, uint32_t x1, uint32_t x2, uint32_t x3, uint32_t rk)
{
  return x0 ^ sm4_enc_sub(x1 ^ x2 ^ x3 ^ rk);
}

static void
sm4_set_key(struct sm4_ctx *ctx, const uint8_t *key, int encrypt)
{
  uint32_t rk0, rk1, rk2, rk3;
  unsigned i;

  rk0 = READ_UINT32(key +  0) ^ fk[0];
  rk1 = READ_UINT32(key +  4) ^ fk[1];
  rk2 = READ_UINT32(key +  8) ^ fk[2];
  rk3 = READ_UINT32(key + 12) ^ fk[3];

  for (i = 0; i < 32; i += 4)
    {
      rk0 ^= sm4_key_sub(rk1 ^ rk2 ^ rk3 ^ ck[i + 0]);
      rk1 ^= sm4_key_sub(rk2 ^ rk3 ^ rk0 ^ ck[i + 1]);
      rk2 ^= sm4_key_sub(rk3 ^ rk0 ^ rk1 ^ ck[i + 2]);
      rk3 ^= sm4_key_sub(rk0 ^ rk1 ^ rk2 ^ ck[i + 3]);

      if (encrypt)
        {
          ctx->rkey[i + 0] = rk0;
          ctx->rkey[i + 1] = rk1;
          ctx->rkey[i + 2] = rk2;
          ctx->rkey[i + 3] = rk3;
        }
      else
        {
          ctx->rkey[31 - 0 - i] = rk0;
          ctx->rkey[31 - 1 - i] = rk1;
          ctx->rkey[31 - 2 - i] = rk2;
          ctx->rkey[31 - 3 - i] = rk3;
        }
    }
}

void
sm4_set_encrypt_key(struct sm4_ctx *ctx, const uint8_t *key)
{
  sm4_set_key(ctx, key, 1);
}

void
sm4_set_decrypt_key(struct sm4_ctx *ctx, const uint8_t *key)
{
  sm4_set_key(ctx, key, 0);
}

void
sm4_crypt(const struct sm4_ctx *context,
	  size_t length,
	  uint8_t *dst,
	  const uint8_t *src)
{
  const uint32_t *rk = context->rkey;

  assert( !(length % SM4_BLOCK_SIZE) );

  for ( ; length; length -= SM4_BLOCK_SIZE)
    {
      uint32_t x0, x1, x2, x3;
      unsigned i;

      x0 = READ_UINT32(src + 0 * 4);
      x1 = READ_UINT32(src + 1 * 4);
      x2 = READ_UINT32(src + 2 * 4);
      x3 = READ_UINT32(src + 3 * 4);

      for (i = 0; i < 32; i += 4)
        {
          x0 = sm4_round(x0, x1, x2, x3, rk[i + 0]);
          x1 = sm4_round(x1, x2, x3, x0, rk[i + 1]);
          x2 = sm4_round(x2, x3, x0, x1, rk[i + 2]);
          x3 = sm4_round(x3, x0, x1, x2, rk[i + 3]);
        }

      WRITE_UINT32(dst + 0 * 4, x3);
      WRITE_UINT32(dst + 1 * 4, x2);
      WRITE_UINT32(dst + 2 * 4, x1);
      WRITE_UINT32(dst + 3 * 4, x0);

      src += SM4_BLOCK_SIZE;
      dst += SM4_BLOCK_SIZE;
    }
}