libavutil/aes.c
Go to the documentation of this file.
00001 /*
00002  * copyright (c) 2007 Michael Niedermayer <michaelni@gmx.at>
00003  *
00004  * some optimization ideas from aes128.c by Reimar Doeffinger
00005  *
00006  * This file is part of Libav.
00007  *
00008  * Libav is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * Libav is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with Libav; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "common.h"
00024 #include "aes.h"
00025 #include "intreadwrite.h"
00026 
00027 typedef union {
00028     uint64_t u64[2];
00029     uint32_t u32[4];
00030     uint8_t u8x4[4][4];
00031     uint8_t u8[16];
00032 } av_aes_block;
00033 
00034 typedef struct AVAES {
00035     // Note: round_key[16] is accessed in the init code, but this only
00036     // overwrites state, which does not matter (see also commit ba554c0).
00037     av_aes_block round_key[15];
00038     av_aes_block state[2];
00039     int rounds;
00040 } AVAES;
00041 
00042 const int av_aes_size= sizeof(AVAES);
00043 
00044 static const uint8_t rcon[10] = {
00045   0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
00046 };
00047 
00048 static uint8_t     sbox[256];
00049 static uint8_t inv_sbox[256];
00050 #if CONFIG_SMALL
00051 static uint32_t enc_multbl[1][256];
00052 static uint32_t dec_multbl[1][256];
00053 #else
00054 static uint32_t enc_multbl[4][256];
00055 static uint32_t dec_multbl[4][256];
00056 #endif
00057 
00058 #if HAVE_BIGENDIAN
00059 #   define ROT(x, s) ((x >> s) | (x << (32-s)))
00060 #else
00061 #   define ROT(x, s) ((x << s) | (x >> (32-s)))
00062 #endif
00063 
00064 static inline void addkey(av_aes_block *dst, const av_aes_block *src,
00065                           const av_aes_block *round_key)
00066 {
00067     dst->u64[0] = src->u64[0] ^ round_key->u64[0];
00068     dst->u64[1] = src->u64[1] ^ round_key->u64[1];
00069 }
00070 
00071 static inline void addkey_s(av_aes_block *dst, const uint8_t *src,
00072                             const av_aes_block *round_key)
00073 {
00074     dst->u64[0] = AV_RN64(src)     ^ round_key->u64[0];
00075     dst->u64[1] = AV_RN64(src + 8) ^ round_key->u64[1];
00076 }
00077 
00078 static inline void addkey_d(uint8_t *dst, const av_aes_block *src,
00079                             const av_aes_block *round_key)
00080 {
00081     AV_WN64(dst,     src->u64[0] ^ round_key->u64[0]);
00082     AV_WN64(dst + 8, src->u64[1] ^ round_key->u64[1]);
00083 }
00084 
00085 static void subshift(av_aes_block s0[2], int s, const uint8_t *box)
00086 {
00087     av_aes_block *s1 = (av_aes_block *) (s0[0].u8 - s);
00088     av_aes_block *s3 = (av_aes_block *) (s0[0].u8 + s);
00089 
00090     s0[0].u8[ 0] = box[s0[1].u8[ 0]];
00091     s0[0].u8[ 4] = box[s0[1].u8[ 4]];
00092     s0[0].u8[ 8] = box[s0[1].u8[ 8]];
00093     s0[0].u8[12] = box[s0[1].u8[12]];
00094     s1[0].u8[ 3] = box[s1[1].u8[ 7]];
00095     s1[0].u8[ 7] = box[s1[1].u8[11]];
00096     s1[0].u8[11] = box[s1[1].u8[15]];
00097     s1[0].u8[15] = box[s1[1].u8[ 3]];
00098     s0[0].u8[ 2] = box[s0[1].u8[10]];
00099     s0[0].u8[10] = box[s0[1].u8[ 2]];
00100     s0[0].u8[ 6] = box[s0[1].u8[14]];
00101     s0[0].u8[14] = box[s0[1].u8[ 6]];
00102     s3[0].u8[ 1] = box[s3[1].u8[13]];
00103     s3[0].u8[13] = box[s3[1].u8[ 9]];
00104     s3[0].u8[ 9] = box[s3[1].u8[ 5]];
00105     s3[0].u8[ 5] = box[s3[1].u8[ 1]];
00106 }
00107 
00108 static inline int mix_core(uint32_t multbl[][256], int a, int b, int c, int d){
00109 #if CONFIG_SMALL
00110     return multbl[0][a] ^ ROT(multbl[0][b], 8) ^ ROT(multbl[0][c], 16) ^ ROT(multbl[0][d], 24);
00111 #else
00112     return multbl[0][a] ^ multbl[1][b] ^ multbl[2][c] ^ multbl[3][d];
00113 #endif
00114 }
00115 
00116 static inline void mix(av_aes_block state[2], uint32_t multbl[][256], int s1, int s3){
00117     uint8_t (*src)[4] = state[1].u8x4;
00118     state[0].u32[0] = mix_core(multbl, src[0][0], src[s1  ][1], src[2][2], src[s3  ][3]);
00119     state[0].u32[1] = mix_core(multbl, src[1][0], src[s3-1][1], src[3][2], src[s1-1][3]);
00120     state[0].u32[2] = mix_core(multbl, src[2][0], src[s3  ][1], src[0][2], src[s1  ][3]);
00121     state[0].u32[3] = mix_core(multbl, src[3][0], src[s1-1][1], src[1][2], src[s3-1][3]);
00122 }
00123 
00124 static inline void crypt(AVAES *a, int s, const uint8_t *sbox,
00125                          uint32_t multbl[][256])
00126 {
00127     int r;
00128 
00129     for (r = a->rounds - 1; r > 0; r--) {
00130         mix(a->state, multbl, 3 - s, 1 + s);
00131         addkey(&a->state[1], &a->state[0], &a->round_key[r]);
00132     }
00133 
00134     subshift(&a->state[0], s, sbox);
00135 }
00136 
00137 void av_aes_crypt(AVAES *a, uint8_t *dst, const uint8_t *src,
00138                   int count, uint8_t *iv, int decrypt)
00139 {
00140     while (count--) {
00141         addkey_s(&a->state[1], src, &a->round_key[a->rounds]);
00142         if (decrypt) {
00143             crypt(a, 0, inv_sbox, dec_multbl);
00144             if (iv) {
00145                 addkey_s(&a->state[0], iv, &a->state[0]);
00146                 memcpy(iv, src, 16);
00147             }
00148             addkey_d(dst, &a->state[0], &a->round_key[0]);
00149         } else {
00150             if (iv)
00151                 addkey_s(&a->state[1], iv, &a->state[1]);
00152             crypt(a, 2, sbox, enc_multbl);
00153             addkey_d(dst, &a->state[0], &a->round_key[0]);
00154             if (iv)
00155                 memcpy(iv, dst, 16);
00156         }
00157         src += 16;
00158         dst += 16;
00159     }
00160 }
00161 
00162 static void init_multbl2(uint32_t tbl[][256], const int c[4],
00163                          const uint8_t *log8, const uint8_t *alog8,
00164                          const uint8_t *sbox)
00165 {
00166     int i;
00167 
00168     for (i = 0; i < 256; i++) {
00169         int x = sbox[i];
00170         if (x) {
00171             int k, l, m, n;
00172             x = log8[x];
00173             k = alog8[x + log8[c[0]]];
00174             l = alog8[x + log8[c[1]]];
00175             m = alog8[x + log8[c[2]]];
00176             n = alog8[x + log8[c[3]]];
00177             tbl[0][i] = AV_NE(MKBETAG(k,l,m,n), MKTAG(k,l,m,n));
00178 #if !CONFIG_SMALL
00179             tbl[1][i] = ROT(tbl[0][i], 8);
00180             tbl[2][i] = ROT(tbl[0][i], 16);
00181             tbl[3][i] = ROT(tbl[0][i], 24);
00182 #endif
00183         }
00184     }
00185 }
00186 
00187 // this is based on the reference AES code by Paulo Barreto and Vincent Rijmen
00188 int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
00189 {
00190     int i, j, t, rconpointer = 0;
00191     uint8_t tk[8][4];
00192     int KC = key_bits >> 5;
00193     int rounds = KC + 6;
00194     uint8_t log8[256];
00195     uint8_t alog8[512];
00196 
00197     if (!enc_multbl[FF_ARRAY_ELEMS(enc_multbl)-1][FF_ARRAY_ELEMS(enc_multbl[0])-1]) {
00198         j = 1;
00199         for (i = 0; i < 255; i++) {
00200             alog8[i] = alog8[i + 255] = j;
00201             log8[j] = i;
00202             j ^= j + j;
00203             if (j > 255)
00204                 j ^= 0x11B;
00205         }
00206         for (i = 0; i < 256; i++) {
00207             j = i ? alog8[255 - log8[i]] : 0;
00208             j ^= (j << 1) ^ (j << 2) ^ (j << 3) ^ (j << 4);
00209             j = (j ^ (j >> 8) ^ 99) & 255;
00210             inv_sbox[j] = i;
00211             sbox[i] = j;
00212         }
00213         init_multbl2(dec_multbl, (const int[4]) { 0xe, 0x9, 0xd, 0xb },
00214                      log8, alog8, inv_sbox);
00215         init_multbl2(enc_multbl, (const int[4]) { 0x2, 0x1, 0x1, 0x3 },
00216                      log8, alog8, sbox);
00217     }
00218 
00219     if (key_bits != 128 && key_bits != 192 && key_bits != 256)
00220         return -1;
00221 
00222     a->rounds = rounds;
00223 
00224     memcpy(tk, key, KC * 4);
00225     memcpy(a->round_key[0].u8, key, KC * 4);
00226 
00227     for (t = KC * 4; t < (rounds + 1) * 16; t += KC * 4) {
00228         for (i = 0; i < 4; i++)
00229             tk[0][i] ^= sbox[tk[KC - 1][(i + 1) & 3]];
00230         tk[0][0] ^= rcon[rconpointer++];
00231 
00232         for (j = 1; j < KC; j++) {
00233             if (KC != 8 || j != KC >> 1)
00234                 for (i = 0; i < 4; i++)
00235                     tk[j][i] ^= tk[j - 1][i];
00236             else
00237                 for (i = 0; i < 4; i++)
00238                     tk[j][i] ^= sbox[tk[j - 1][i]];
00239         }
00240 
00241         memcpy(a->round_key[0].u8 + t, tk, KC * 4);
00242     }
00243 
00244     if (decrypt) {
00245         for (i = 1; i < rounds; i++) {
00246             av_aes_block tmp[3];
00247             tmp[2] = a->round_key[i];
00248             subshift(&tmp[1], 0, sbox);
00249             mix(tmp, dec_multbl, 1, 3);
00250             a->round_key[i] = tmp[0];
00251         }
00252     } else {
00253         for (i = 0; i < (rounds + 1) >> 1; i++) {
00254             FFSWAP(av_aes_block, a->round_key[i], a->round_key[rounds-i]);
00255         }
00256     }
00257 
00258     return 0;
00259 }
00260 
00261 #ifdef TEST
00262 #include <string.h>
00263 #include "lfg.h"
00264 #include "log.h"
00265 
00266 int main(int argc, char **argv)
00267 {
00268     int i, j;
00269     AVAES b;
00270     uint8_t rkey[2][16] = {
00271         { 0 },
00272         { 0x10, 0xa5, 0x88, 0x69, 0xd7, 0x4b, 0xe5, 0xa3,
00273           0x74, 0xcf, 0x86, 0x7c, 0xfb, 0x47, 0x38, 0x59 }
00274     };
00275     uint8_t pt[16], rpt[2][16]= {
00276         { 0x6a, 0x84, 0x86, 0x7c, 0xd7, 0x7e, 0x12, 0xad,
00277           0x07, 0xea, 0x1b, 0xe8, 0x95, 0xc5, 0x3f, 0xa3 },
00278         { 0 }
00279     };
00280     uint8_t rct[2][16]= {
00281         { 0x73, 0x22, 0x81, 0xc0, 0xa0, 0xaa, 0xb8, 0xf7,
00282           0xa5, 0x4a, 0x0c, 0x67, 0xa0, 0xc4, 0x5e, 0xcf },
00283         { 0x6d, 0x25, 0x1e, 0x69, 0x44, 0xb0, 0x51, 0xe0,
00284           0x4e, 0xaa, 0x6f, 0xb4, 0xdb, 0xf7, 0x84, 0x65 }
00285     };
00286     uint8_t temp[16];
00287     int err = 0;
00288 
00289     av_log_set_level(AV_LOG_DEBUG);
00290 
00291     for (i = 0; i < 2; i++) {
00292         av_aes_init(&b, rkey[i], 128, 1);
00293         av_aes_crypt(&b, temp, rct[i], 1, NULL, 1);
00294         for (j = 0; j < 16; j++) {
00295             if (rpt[i][j] != temp[j]) {
00296                 av_log(NULL, AV_LOG_ERROR, "%d %02X %02X\n",
00297                        j, rpt[i][j], temp[j]);
00298                 err = 1;
00299             }
00300         }
00301     }
00302 
00303     if (argc > 1 && !strcmp(argv[1], "-t")) {
00304         AVAES ae, ad;
00305         AVLFG prng;
00306 
00307         av_aes_init(&ae, "PI=3.141592654..", 128, 0);
00308         av_aes_init(&ad, "PI=3.141592654..", 128, 1);
00309         av_lfg_init(&prng, 1);
00310 
00311         for (i = 0; i < 10000; i++) {
00312             for (j = 0; j < 16; j++) {
00313                 pt[j] = av_lfg_get(&prng);
00314             }
00315             {
00316                 START_TIMER;
00317                 av_aes_crypt(&ae, temp, pt, 1, NULL, 0);
00318                 if (!(i & (i - 1)))
00319                     av_log(NULL, AV_LOG_ERROR, "%02X %02X %02X %02X\n",
00320                            temp[0], temp[5], temp[10], temp[15]);
00321                 av_aes_crypt(&ad, temp, temp, 1, NULL, 1);
00322                 STOP_TIMER("aes");
00323             }
00324             for (j = 0; j < 16; j++) {
00325                 if (pt[j] != temp[j]) {
00326                     av_log(NULL, AV_LOG_ERROR, "%d %d %02X %02X\n",
00327                            i, j, pt[j], temp[j]);
00328                 }
00329             }
00330         }
00331     }
00332     return err;
00333 }
00334 #endif