crypto/aes_ti.c

   1 /*
   2  * Scalar fixed time AES core transform
   3  *
   4  * Copyright (C) 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <crypto/aes.h>
  12 #include <linux/crypto.h>
  13 #include <linux/module.h>
  14 #include <asm/unaligned.h>
  15
  16 /*
  17  * Emit the sbox as volatile const to prevent the compiler from doing
  18  * constant folding on sbox references involving fixed indexes.
  19  */
  20 static volatile const u8 __cacheline_aligned __aesti_sbox[] = {
  21         0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
  22         0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  23         0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
  24         0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  25         0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
  26         0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  27         0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
  28         0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  29         0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
  30         0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  31         0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
  32         0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  33         0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
  34         0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  35         0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
  36         0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  37         0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
  38         0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  39         0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
  40         0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  41         0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
  42         0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  43         0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
  44         0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  45         0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
  46         0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  47         0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
  48         0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  49         0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
  50         0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  51         0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
  52         0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
  53 };
  54
  55 static volatile const u8 __cacheline_aligned __aesti_inv_sbox[] = {
  56         0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
  57         0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  58         0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
  59         0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  60         0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
  61         0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  62         0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
  63         0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
  64         0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
  65         0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
  66         0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
  67         0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
  68         0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
  69         0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
  70         0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
  71         0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
  72         0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
  73         0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
  74         0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
  75         0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
  76         0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
  77         0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
  78         0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
  79         0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
  80         0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
  81         0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
  82         0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
  83         0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
  84         0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
  85         0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
  86         0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
  87         0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
  88 };
  89
  90 static u32 mul_by_x(u32 w)
  91 {
  92         u32 x = w & 0x7f7f7f7f;
  93         u32 y = w & 0x80808080;
  94
  95         /* multiply by polynomial 'x' (0b10) in GF(2^8) */
  96         return (x << 1) ^ (y >> 7) * 0x1b;
  97 }
  98
  99 static u32 mul_by_x2(u32 w)
 100 {
 101         u32 x = w & 0x3f3f3f3f;
 102         u32 y = w & 0x80808080;
 103         u32 z = w & 0x40404040;
 104
 105         /* multiply by polynomial 'x^2' (0b100) in GF(2^8) */
 106         return (x << 2) ^ (y >> 7) * 0x36 ^ (z >> 6) * 0x1b;
 107 }
 108
 109 static u32 mix_columns(u32 x)
 110 {
 111         /*
 112          * Perform the following matrix multiplication in GF(2^8)
 113          *
 114          * | 0x2 0x3 0x1 0x1 |   | x[0] |
 115          * | 0x1 0x2 0x3 0x1 |   | x[1] |
 116          * | 0x1 0x1 0x2 0x3 | x | x[2] |
 117          * | 0x3 0x1 0x1 0x3 |   | x[3] |
 118          */
 119         u32 y = mul_by_x(x) ^ ror32(x, 16);
 120
 121         return y ^ ror32(x ^ y, 8);
 122 }
 123
 124 static u32 inv_mix_columns(u32 x)
 125 {
 126         /*
 127          * Perform the following matrix multiplication in GF(2^8)
 128          *
 129          * | 0xe 0xb 0xd 0x9 |   | x[0] |
 130          * | 0x9 0xe 0xb 0xd |   | x[1] |
 131          * | 0xd 0x9 0xe 0xb | x | x[2] |
 132          * | 0xb 0xd 0x9 0xe |   | x[3] |
 133          *
 134          * which can conveniently be reduced to
 135          *
 136          * | 0x2 0x3 0x1 0x1 |   | 0x5 0x0 0x4 0x0 |   | x[0] |
 137          * | 0x1 0x2 0x3 0x1 |   | 0x0 0x5 0x0 0x4 |   | x[1] |
 138          * | 0x1 0x1 0x2 0x3 | x | 0x4 0x0 0x5 0x0 | x | x[2] |
 139          * | 0x3 0x1 0x1 0x2 |   | 0x0 0x4 0x0 0x5 |   | x[3] |
 140          */
 141         u32 y = mul_by_x2(x);
 142
 143         return mix_columns(x ^ y ^ ror32(y, 16));
 144 }
 145
 146 static __always_inline u32 subshift(u32 in[], int pos)
 147 {
 148         return (__aesti_sbox[in[pos] & 0xff]) ^
 149                (__aesti_sbox[(in[(pos + 1) % 4] >>  8) & 0xff] <<  8) ^
 150                (__aesti_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
 151                (__aesti_sbox[(in[(pos + 3) % 4] >> 24) & 0xff] << 24);
 152 }
 153
 154 static __always_inline u32 inv_subshift(u32 in[], int pos)
 155 {
 156         return (__aesti_inv_sbox[in[pos] & 0xff]) ^
 157                (__aesti_inv_sbox[(in[(pos + 3) % 4] >>  8) & 0xff] <<  8) ^
 158                (__aesti_inv_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
 159                (__aesti_inv_sbox[(in[(pos + 1) % 4] >> 24) & 0xff] << 24);
 160 }
 161
 162 static u32 subw(u32 in)
 163 {
 164         return (__aesti_sbox[in & 0xff]) ^
 165                (__aesti_sbox[(in >>  8) & 0xff] <<  8) ^
 166                (__aesti_sbox[(in >> 16) & 0xff] << 16) ^
 167                (__aesti_sbox[(in >> 24) & 0xff] << 24);
 168 }
 169
 170 static int aesti_expand_key(struct crypto_aes_ctx *ctx, const u8 *in_key,
 171                             unsigned int key_len)
 172 {
 173         u32 kwords = key_len / sizeof(u32);
 174         u32 rc, i, j;
 175
 176         if (key_len != AES_KEYSIZE_128 &&
 177             key_len != AES_KEYSIZE_192 &&
 178             key_len != AES_KEYSIZE_256)
 179                 return -EINVAL;
 180
 181         ctx->key_length = key_len;
 182
 183         for (i = 0; i < kwords; i++)
 184                 ctx->key_enc[i] = get_unaligned_le32(in_key + i * sizeof(u32));
 185
 186         for (i = 0, rc = 1; i < 10; i++, rc = mul_by_x(rc)) {
 187                 u32 *rki = ctx->key_enc + (i * kwords);
 188                 u32 *rko = rki + kwords;
 189
 190                 rko[0] = ror32(subw(rki[kwords - 1]), 8) ^ rc ^ rki[0];
 191                 rko[1] = rko[0] ^ rki[1];
 192                 rko[2] = rko[1] ^ rki[2];
 193                 rko[3] = rko[2] ^ rki[3];
 194
 195                 if (key_len == 24) {
 196                         if (i >= 7)
 197                                 break;
 198                         rko[4] = rko[3] ^ rki[4];
 199                         rko[5] = rko[4] ^ rki[5];
 200                 } else if (key_len == 32) {
 201                         if (i >= 6)
 202                                 break;
 203                         rko[4] = subw(rko[3]) ^ rki[4];
 204                         rko[5] = rko[4] ^ rki[5];
 205                         rko[6] = rko[5] ^ rki[6];
 206                         rko[7] = rko[6] ^ rki[7];
 207                 }
 208         }
 209
 210         /*
 211          * Generate the decryption keys for the Equivalent Inverse Cipher.
 212          * This involves reversing the order of the round keys, and applying
 213          * the Inverse Mix Columns transformation to all but the first and
 214          * the last one.
 215          */
 216         ctx->key_dec[0] = ctx->key_enc[key_len + 24];
 217         ctx->key_dec[1] = ctx->key_enc[key_len + 25];
 218         ctx->key_dec[2] = ctx->key_enc[key_len + 26];
 219         ctx->key_dec[3] = ctx->key_enc[key_len + 27];
 220
 221         for (i = 4, j = key_len + 20; j > 0; i += 4, j -= 4) {
 222                 ctx->key_dec[i]     = inv_mix_columns(ctx->key_enc[j]);
 223                 ctx->key_dec[i + 1] = inv_mix_columns(ctx->key_enc[j + 1]);
 224                 ctx->key_dec[i + 2] = inv_mix_columns(ctx->key_enc[j + 2]);
 225                 ctx->key_dec[i + 3] = inv_mix_columns(ctx->key_enc[j + 3]);
 226         }
 227
 228         ctx->key_dec[i]     = ctx->key_enc[0];
 229         ctx->key_dec[i + 1] = ctx->key_enc[1];
 230         ctx->key_dec[i + 2] = ctx->key_enc[2];
 231         ctx->key_dec[i + 3] = ctx->key_enc[3];
 232
 233         return 0;
 234 }
 235
 236 static int aesti_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 237                          unsigned int key_len)
 238 {
 239         struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
 240         int err;
 241
 242         err = aesti_expand_key(ctx, in_key, key_len);
 243         if (err)
 244                 return err;
 245
 246         /*
 247          * In order to force the compiler to emit data independent Sbox lookups
 248          * at the start of each block, xor the first round key with values at
 249          * fixed indexes in the Sbox. This will need to be repeated each time
 250          * the key is used, which will pull the entire Sbox into the D-cache
 251          * before any data dependent Sbox lookups are performed.
 252          */
 253         ctx->key_enc[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128];
 254         ctx->key_enc[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160];
 255         ctx->key_enc[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192];
 256         ctx->key_enc[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224];
 257
 258         ctx->key_dec[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128];
 259         ctx->key_dec[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160];
 260         ctx->key_dec[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192];
 261         ctx->key_dec[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224];
 262
 263         return 0;
 264 }
 265
 266 static void aesti_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 267 {
 268         const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
 269         const u32 *rkp = ctx->key_enc + 4;
 270         int rounds = 6 + ctx->key_length / 4;
 271         u32 st0[4], st1[4];
 272         int round;
 273
 274         st0[0] = ctx->key_enc[0] ^ get_unaligned_le32(in);
 275         st0[1] = ctx->key_enc[1] ^ get_unaligned_le32(in + 4);
 276         st0[2] = ctx->key_enc[2] ^ get_unaligned_le32(in + 8);
 277         st0[3] = ctx->key_enc[3] ^ get_unaligned_le32(in + 12);
 278
 279         st0[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128];
 280         st0[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160];
 281         st0[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192];
 282         st0[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224];
 283
 284         for (round = 0;; round += 2, rkp += 8) {
 285                 st1[0] = mix_columns(subshift(st0, 0)) ^ rkp[0];
 286                 st1[1] = mix_columns(subshift(st0, 1)) ^ rkp[1];
 287                 st1[2] = mix_columns(subshift(st0, 2)) ^ rkp[2];
 288                 st1[3] = mix_columns(subshift(st0, 3)) ^ rkp[3];
 289
 290                 if (round == rounds - 2)
 291                         break;
 292
 293                 st0[0] = mix_columns(subshift(st1, 0)) ^ rkp[4];
 294                 st0[1] = mix_columns(subshift(st1, 1)) ^ rkp[5];
 295                 st0[2] = mix_columns(subshift(st1, 2)) ^ rkp[6];
 296                 st0[3] = mix_columns(subshift(st1, 3)) ^ rkp[7];
 297         }
 298
 299         put_unaligned_le32(subshift(st1, 0) ^ rkp[4], out);
 300         put_unaligned_le32(subshift(st1, 1) ^ rkp[5], out + 4);
 301         put_unaligned_le32(subshift(st1, 2) ^ rkp[6], out + 8);
 302         put_unaligned_le32(subshift(st1, 3) ^ rkp[7], out + 12);
 303 }
 304
 305 static void aesti_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 306 {
 307         const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
 308         const u32 *rkp = ctx->key_dec + 4;
 309         int rounds = 6 + ctx->key_length / 4;
 310         u32 st0[4], st1[4];
 311         int round;
 312
 313         st0[0] = ctx->key_dec[0] ^ get_unaligned_le32(in);
 314         st0[1] = ctx->key_dec[1] ^ get_unaligned_le32(in + 4);
 315         st0[2] = ctx->key_dec[2] ^ get_unaligned_le32(in + 8);
 316         st0[3] = ctx->key_dec[3] ^ get_unaligned_le32(in + 12);
 317
 318         st0[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128];
 319         st0[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160];
 320         st0[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192];
 321         st0[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224];
 322
 323         for (round = 0;; round += 2, rkp += 8) {
 324                 st1[0] = inv_mix_columns(inv_subshift(st0, 0)) ^ rkp[0];
 325                 st1[1] = inv_mix_columns(inv_subshift(st0, 1)) ^ rkp[1];
 326                 st1[2] = inv_mix_columns(inv_subshift(st0, 2)) ^ rkp[2];
 327                 st1[3] = inv_mix_columns(inv_subshift(st0, 3)) ^ rkp[3];
 328
 329                 if (round == rounds - 2)
 330                         break;
 331
 332                 st0[0] = inv_mix_columns(inv_subshift(st1, 0)) ^ rkp[4];
 333                 st0[1] = inv_mix_columns(inv_subshift(st1, 1)) ^ rkp[5];
 334                 st0[2] = inv_mix_columns(inv_subshift(st1, 2)) ^ rkp[6];
 335                 st0[3] = inv_mix_columns(inv_subshift(st1, 3)) ^ rkp[7];
 336         }
 337
 338         put_unaligned_le32(inv_subshift(st1, 0) ^ rkp[4], out);
 339         put_unaligned_le32(inv_subshift(st1, 1) ^ rkp[5], out + 4);
 340         put_unaligned_le32(inv_subshift(st1, 2) ^ rkp[6], out + 8);
 341         put_unaligned_le32(inv_subshift(st1, 3) ^ rkp[7], out + 12);
 342 }
 343
 344 static struct crypto_alg aes_alg = {
 345         .cra_name                       = "aes",
 346         .cra_driver_name                = "aes-fixed-time",
 347         .cra_priority                   = 100 + 1,
 348         .cra_flags                      = CRYPTO_ALG_TYPE_CIPHER,
 349         .cra_blocksize                  = AES_BLOCK_SIZE,
 350         .cra_ctxsize                    = sizeof(struct crypto_aes_ctx),
 351         .cra_module                     = THIS_MODULE,
 352
 353         .cra_cipher.cia_min_keysize     = AES_MIN_KEY_SIZE,
 354         .cra_cipher.cia_max_keysize     = AES_MAX_KEY_SIZE,
 355         .cra_cipher.cia_setkey          = aesti_set_key,
 356         .cra_cipher.cia_encrypt         = aesti_encrypt,
 357         .cra_cipher.cia_decrypt         = aesti_decrypt
 358 };
 359
 360 static int __init aes_init(void)
 361 {
 362         return crypto_register_alg(&aes_alg);
 363 }
 364
 365 static void __exit aes_fini(void)
 366 {
 367         crypto_unregister_alg(&aes_alg);
 368 }
 369
 370 module_init(aes_init);
 371 module_exit(aes_fini);
 372
 373 MODULE_DESCRIPTION("Generic fixed time AES");
 374 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 375 MODULE_LICENSE("GPL v2");