aboutsummaryrefslogtreecommitdiffstats
path: root/libavutil/aes.c
blob: 397ea773898b14d0aee3f09d6b0318b1b9396ddd (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
/*
 * 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;
}