/*

  * copyright (c) 2007 Michael Niedermayer <michaelni@gmx.at>

  *

  * some optimization ideas from aes128.c by Reimar Doeffinger
  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "common.h"
 #include "aes.h"

 #include "aes_internal.h"

 #include "intreadwrite.h"

 #include "timer.h"

 const int av_aes_size= sizeof(AVAES);

 
 struct AVAES *av_aes_alloc(void)
 {
     return av_mallocz(sizeof(struct AVAES));
 }

 static const uint8_t rcon[10] = {

     0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36

 };
 
 static uint8_t     sbox[256];
 static uint8_t inv_sbox[256];

 #if CONFIG_SMALL

 static uint32_t enc_multbl[1][256];
 static uint32_t dec_multbl[1][256];
 #else
 static uint32_t enc_multbl[4][256];
 static uint32_t dec_multbl[4][256];
 #endif

 #if HAVE_BIGENDIAN

 #   define ROT(x, s) (((x) >> (s)) | ((x) << (32-(s))))

 #else

 #   define ROT(x, s) (((x) << (s)) | ((x) >> (32-(s))))

 #endif

 static inline void addkey(av_aes_block *dst, const av_aes_block *src,
                           const av_aes_block *round_key)
 {

     dst->u64[0] = src->u64[0] ^ round_key->u64[0];
     dst->u64[1] = src->u64[1] ^ round_key->u64[1];

 }
 

 static inline void addkey_s(av_aes_block *dst, const uint8_t *src,
                             const av_aes_block *round_key)
 {
     dst->u64[0] = AV_RN64(src)     ^ round_key->u64[0];
     dst->u64[1] = AV_RN64(src + 8) ^ round_key->u64[1];
 }
 
 static inline void addkey_d(uint8_t *dst, const av_aes_block *src,
                             const av_aes_block *round_key)
 {
     AV_WN64(dst,     src->u64[0] ^ round_key->u64[0]);
     AV_WN64(dst + 8, src->u64[1] ^ round_key->u64[1]);
 }
 

 static void subshift(av_aes_block s0[2], int s, const uint8_t *box)
 {
     av_aes_block *s1 = (av_aes_block *) (s0[0].u8 - s);
     av_aes_block *s3 = (av_aes_block *) (s0[0].u8 + s);
 
     s0[0].u8[ 0] = box[s0[1].u8[ 0]];
     s0[0].u8[ 4] = box[s0[1].u8[ 4]];
     s0[0].u8[ 8] = box[s0[1].u8[ 8]];
     s0[0].u8[12] = box[s0[1].u8[12]];
     s1[0].u8[ 3] = box[s1[1].u8[ 7]];
     s1[0].u8[ 7] = box[s1[1].u8[11]];
     s1[0].u8[11] = box[s1[1].u8[15]];
     s1[0].u8[15] = box[s1[1].u8[ 3]];
     s0[0].u8[ 2] = box[s0[1].u8[10]];
     s0[0].u8[10] = box[s0[1].u8[ 2]];
     s0[0].u8[ 6] = box[s0[1].u8[14]];
     s0[0].u8[14] = box[s0[1].u8[ 6]];
     s3[0].u8[ 1] = box[s3[1].u8[13]];
     s3[0].u8[13] = box[s3[1].u8[ 9]];
     s3[0].u8[ 9] = box[s3[1].u8[ 5]];
     s3[0].u8[ 5] = box[s3[1].u8[ 1]];

 }

 static inline int mix_core(uint32_t multbl[][256], int a, int b, int c, int d)
 {

 #if CONFIG_SMALL

     return multbl[0][a] ^ ROT(multbl[0][b], 8) ^ ROT(multbl[0][c], 16) ^ ROT(multbl[0][d], 24);

 #else

     return multbl[0][a] ^ multbl[1][b] ^ multbl[2][c] ^ multbl[3][d];

 #endif

 }

 static inline void mix(av_aes_block state[2], uint32_t multbl[][256], int s1, int s3)
 {

     uint8_t (*src)[4] = state[1].u8x4;

     state[0].u32[0] = mix_core(multbl, src[0][0], src[s1    ][1], src[2][2], src[s3    ][3]);
     state[0].u32[1] = mix_core(multbl, src[1][0], src[s3 - 1][1], src[3][2], src[s1 - 1][3]);
     state[0].u32[2] = mix_core(multbl, src[2][0], src[s3    ][1], src[0][2], src[s1    ][3]);
     state[0].u32[3] = mix_core(multbl, src[3][0], src[s1 - 1][1], src[1][2], src[s3 - 1][3]);

 }

 static inline void aes_crypt(AVAES *a, int s, const uint8_t *sbox,

                          uint32_t multbl[][256])
 {

     int r;

     for (r = a->rounds - 1; r > 0; r--) {
         mix(a->state, multbl, 3 - s, 1 + s);

         addkey(&a->state[1], &a->state[0], &a->round_key[r]);

     }

     subshift(&a->state[0], s, sbox);

 }
 

 static void aes_encrypt(AVAES *a, uint8_t *dst, const uint8_t *src,
                         int count, uint8_t *iv, int rounds)

 {
     while (count--) {

         addkey_s(&a->state[1], src, &a->round_key[rounds]);
         if (iv)
             addkey_s(&a->state[1], iv, &a->state[1]);
         aes_crypt(a, 2, sbox, enc_multbl);
         addkey_d(dst, &a->state[0], &a->round_key[0]);
         if (iv)
             memcpy(iv, dst, 16);
         src += 16;
         dst += 16;
     }
 }
 
 static void aes_decrypt(AVAES *a, uint8_t *dst, const uint8_t *src,
                         int count, uint8_t *iv, int rounds)
 {
     while (count--) {
         addkey_s(&a->state[1], src, &a->round_key[rounds]);
         aes_crypt(a, 0, inv_sbox, dec_multbl);
         if (iv) {
             addkey_s(&a->state[0], iv, &a->state[0]);
             memcpy(iv, src, 16);

         }

         addkey_d(dst, &a->state[0], &a->round_key[0]);

         src += 16;
         dst += 16;

     }

 }
 

 void av_aes_crypt(AVAES *a, uint8_t *dst, const uint8_t *src,
                   int count, uint8_t *iv, int decrypt)
 {
     a->crypt(a, dst, src, count, iv, a->rounds);
 }
 

 static void init_multbl2(uint32_t tbl[][256], const int c[4],

                          const uint8_t *log8, const uint8_t *alog8,
                          const uint8_t *sbox)
 {

     int i;

     for (i = 0; i < 256; i++) {
         int x = sbox[i];
         if (x) {
             int k, l, m, n;
             x = log8[x];
             k = alog8[x + log8[c[0]]];
             l = alog8[x + log8[c[1]]];
             m = alog8[x + log8[c[2]]];
             n = alog8[x + log8[c[3]]];

             tbl[0][i] = AV_NE(MKBETAG(k, l, m, n), MKTAG(k, l, m, n));

 #if !CONFIG_SMALL

             tbl[1][i] = ROT(tbl[0][i], 8);
             tbl[2][i] = ROT(tbl[0][i], 16);
             tbl[3][i] = ROT(tbl[0][i], 24);

 #endif

         }
     }

 }
 

 // this is based on the reference AES code by Paulo Barreto and Vincent Rijmen

 int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
 {

     int i, j, t, rconpointer = 0;
     uint8_t tk[8][4];

     int KC = key_bits >> 5;
     int rounds = KC + 6;
     uint8_t log8[256];

     uint8_t alog8[512];

     a->crypt = decrypt ? aes_decrypt : aes_encrypt;
 

     if (!enc_multbl[FF_ARRAY_ELEMS(enc_multbl) - 1][FF_ARRAY_ELEMS(enc_multbl[0]) - 1]) {

         j = 1;
         for (i = 0; i < 255; i++) {
             alog8[i] = alog8[i + 255] = j;
             log8[j] = i;
             j ^= j + j;
             if (j > 255)
                 j ^= 0x11B;

         }

         for (i = 0; i < 256; i++) {
             j = i ? alog8[255 - log8[i]] : 0;
             j ^= (j << 1) ^ (j << 2) ^ (j << 3) ^ (j << 4);
             j = (j ^ (j >> 8) ^ 99) & 255;
             inv_sbox[j] = i;

             sbox[i]     = j;

         }

         init_multbl2(dec_multbl, (const int[4]) { 0xe, 0x9, 0xd, 0xb },

                      log8, alog8, inv_sbox);

         init_multbl2(enc_multbl, (const int[4]) { 0x2, 0x1, 0x1, 0x3 },

                      log8, alog8, sbox);

     }
 

     if (key_bits != 128 && key_bits != 192 && key_bits != 256)

         return AVERROR(EINVAL);

     a->rounds = rounds;

     memcpy(tk, key, KC * 4);

     memcpy(a->round_key[0].u8, key, KC * 4);

     for (t = KC * 4; t < (rounds + 1) * 16; t += KC * 4) {

         for (i = 0; i < 4; i++)
             tk[0][i] ^= sbox[tk[KC - 1][(i + 1) & 3]];

         tk[0][0] ^= rcon[rconpointer++];
 

         for (j = 1; j < KC; j++) {
             if (KC != 8 || j != KC >> 1)
                 for (i = 0; i < 4; i++)
                     tk[j][i] ^= tk[j - 1][i];

             else

                 for (i = 0; i < 4; i++)
                     tk[j][i] ^= sbox[tk[j - 1][i]];

         }

 
         memcpy(a->round_key[0].u8 + t, tk, KC * 4);

     }

     if (decrypt) {
         for (i = 1; i < rounds; i++) {

             av_aes_block tmp[3];

             tmp[2] = a->round_key[i];

             subshift(&tmp[1], 0, sbox);

             mix(tmp, dec_multbl, 1, 3);

             a->round_key[i] = tmp[0];

         }

     } else {

         for (i = 0; i < (rounds + 1) >> 1; i++)
             FFSWAP(av_aes_block, a->round_key[i], a->round_key[rounds - i]);

     }

     return 0;

 }