crypto/aes_ti.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Scalar fixed time AES core transform
   4  *
   5  * Copyright (C) 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
   6  */
   7
   8 #include <crypto/aes.h>
   9 #include <linux/crypto.h>
  10 #include <linux/module.h>
  11 #include <asm/unaligned.h>
  12
  13 /*
  14  * Emit the sbox as volatile const to prevent the compiler from doing
  15  * constant folding on sbox references involving fixed indexes.
  16  */
  17 static volatile const u8 __cacheline_aligned __aesti_sbox[] = {
  18         0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
  19         0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  20         0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
  21         0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  22         0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
  23         0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  24         0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
  25         0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  26         0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
  27         0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  28         0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
  29         0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  30         0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
  31         0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  32         0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
  33         0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  34         0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
  35         0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  36         0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
  37         0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  38         0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
  39         0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  40         0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
  41         0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  42         0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
  43         0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  44         0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
  45         0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  46         0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
  47         0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  48         0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
  49         0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
  50 };
  51
  52 static volatile const u8 __cacheline_aligned __aesti_inv_sbox[] = {
  53         0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
  54         0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  55         0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
  56         0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  57         0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
  58         0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  59         0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
  60         0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
  61         0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
  62         0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
  63         0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
  64         0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
  65         0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
  66         0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
  67         0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
  68         0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
  69         0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
  70         0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
  71         0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
  72         0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
  73         0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
  74         0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
  75         0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
  76         0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
  77         0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
  78         0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
  79         0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
  80         0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
  81         0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
  82         0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
  83         0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
  84         0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
  85 };
  86
  87 static u32 mul_by_x(u32 w)
  88 {
  89         u32 x = w & 0x7f7f7f7f;
  90         u32 y = w & 0x80808080;
  91
  92         /* multiply by polynomial 'x' (0b10) in GF(2^8) */
  93         return (x << 1) ^ (y >> 7) * 0x1b;
  94 }
  95
  96 static u32 mul_by_x2(u32 w)
  97 {
  98         u32 x = w & 0x3f3f3f3f;
  99         u32 y = w & 0x80808080;
 100         u32 z = w & 0x40404040;
 101
 102         /* multiply by polynomial 'x^2' (0b100) in GF(2^8) */
 103         return (x << 2) ^ (y >> 7) * 0x36 ^ (z >> 6) * 0x1b;
 104 }
 105
 106 static u32 mix_columns(u32 x)
 107 {
 108         /*
 109          * Perform the following matrix multiplication in GF(2^8)
 110          *
 111          * | 0x2 0x3 0x1 0x1 |   | x[0] |
 112          * | 0x1 0x2 0x3 0x1 |   | x[1] |
 113          * | 0x1 0x1 0x2 0x3 | x | x[2] |
 114          * | 0x3 0x1 0x1 0x2 |   | x[3] |
 115          */
 116         u32 y = mul_by_x(x) ^ ror32(x, 16);
 117
 118         return y ^ ror32(x ^ y, 8);
 119 }
 120
 121 static u32 inv_mix_columns(u32 x)
 122 {
 123         /*
 124          * Perform the following matrix multiplication in GF(2^8)
 125          *
 126          * | 0xe 0xb 0xd 0x9 |   | x[0] |
 127          * | 0x9 0xe 0xb 0xd |   | x[1] |
 128          * | 0xd 0x9 0xe 0xb | x | x[2] |
 129          * | 0xb 0xd 0x9 0xe |   | x[3] |
 130          *
 131          * which can conveniently be reduced to
 132          *
 133          * | 0x2 0x3 0x1 0x1 |   | 0x5 0x0 0x4 0x0 |   | x[0] |
 134          * | 0x1 0x2 0x3 0x1 |   | 0x0 0x5 0x0 0x4 |   | x[1] |
 135          * | 0x1 0x1 0x2 0x3 | x | 0x4 0x0 0x5 0x0 | x | x[2] |
 136          * | 0x3 0x1 0x1 0x2 |   | 0x0 0x4 0x0 0x5 |   | x[3] |
 137          */
 138         u32 y = mul_by_x2(x);
 139
 140         return mix_columns(x ^ y ^ ror32(y, 16));
 141 }
 142
 143 static __always_inline u32 subshift(u32 in[], int pos)
 144 {
 145         return (__aesti_sbox[in[pos] & 0xff]) ^
 146                (__aesti_sbox[(in[(pos + 1) % 4] >>  8) & 0xff] <<  8) ^
 147                (__aesti_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
 148                (__aesti_sbox[(in[(pos + 3) % 4] >> 24) & 0xff] << 24);
 149 }
 150
 151 static __always_inline u32 inv_subshift(u32 in[], int pos)
 152 {
 153         return (__aesti_inv_sbox[in[pos] & 0xff]) ^
 154                (__aesti_inv_sbox[(in[(pos + 3) % 4] >>  8) & 0xff] <<  8) ^
 155                (__aesti_inv_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
 156                (__aesti_inv_sbox[(in[(pos + 1) % 4] >> 24) & 0xff] << 24);
 157 }
 158
 159 static u32 subw(u32 in)
 160 {
 161         return (__aesti_sbox[in & 0xff]) ^
 162                (__aesti_sbox[(in >>  8) & 0xff] <<  8) ^
 163                (__aesti_sbox[(in >> 16) & 0xff] << 16) ^
 164                (__aesti_sbox[(in >> 24) & 0xff] << 24);
 165 }
 166
 167 static int aesti_expand_key(struct crypto_aes_ctx *ctx, const u8 *in_key,
 168                             unsigned int key_len)
 169 {
 170         u32 kwords = key_len / sizeof(u32);
 171         u32 rc, i, j;
 172
 173         if (key_len != AES_KEYSIZE_128 &&
 174             key_len != AES_KEYSIZE_192 &&
 175             key_len != AES_KEYSIZE_256)
 176                 return -EINVAL;
 177
 178         ctx->key_length = key_len;
 179
 180         for (i = 0; i < kwords; i++)
 181                 ctx->key_enc[i] = get_unaligned_le32(in_key + i * sizeof(u32));
 182
 183         for (i = 0, rc = 1; i < 10; i++, rc = mul_by_x(rc)) {
 184                 u32 *rki = ctx->key_enc + (i * kwords);
 185                 u32 *rko = rki + kwords;
 186
 187                 rko[0] = ror32(subw(rki[kwords - 1]), 8) ^ rc ^ rki[0];
 188                 rko[1] = rko[0] ^ rki[1];
 189                 rko[2] = rko[1] ^ rki[2];
 190                 rko[3] = rko[2] ^ rki[3];
 191
 192                 if (key_len == 24) {
 193                         if (i >= 7)
 194                                 break;
 195                         rko[4] = rko[3] ^ rki[4];
 196                         rko[5] = rko[4] ^ rki[5];
 197                 } else if (key_len == 32) {
 198                         if (i >= 6)
 199                                 break;
 200                         rko[4] = subw(rko[3]) ^ rki[4];
 201                         rko[5] = rko[4] ^ rki[5];
 202                         rko[6] = rko[5] ^ rki[6];
 203                         rko[7] = rko[6] ^ rki[7];
 204                 }
 205         }
 206
 207         /*
 208          * Generate the decryption keys for the Equivalent Inverse Cipher.
 209          * This involves reversing the order of the round keys, and applying
 210          * the Inverse Mix Columns transformation to all but the first and
 211          * the last one.
 212          */
 213         ctx->key_dec[0] = ctx->key_enc[key_len + 24];
 214         ctx->key_dec[1] = ctx->key_enc[key_len + 25];
 215         ctx->key_dec[2] = ctx->key_enc[key_len + 26];
 216         ctx->key_dec[3] = ctx->key_enc[key_len + 27];
 217
 218         for (i = 4, j = key_len + 20; j > 0; i += 4, j -= 4) {
 219                 ctx->key_dec[i]     = inv_mix_columns(ctx->key_enc[j]);
 220                 ctx->key_dec[i + 1] = inv_mix_columns(ctx->key_enc[j + 1]);
 221                 ctx->key_dec[i + 2] = inv_mix_columns(ctx->key_enc[j + 2]);
 222                 ctx->key_dec[i + 3] = inv_mix_columns(ctx->key_enc[j + 3]);
 223         }
 224
 225         ctx->key_dec[i]     = ctx->key_enc[0];
 226         ctx->key_dec[i + 1] = ctx->key_enc[1];
 227         ctx->key_dec[i + 2] = ctx->key_enc[2];
 228         ctx->key_dec[i + 3] = ctx->key_enc[3];
 229
 230         return 0;
 231 }
 232
 233 static int aesti_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 234                          unsigned int key_len)
 235 {
 236         struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
 237         int err;
 238
 239         err = aesti_expand_key(ctx, in_key, key_len);
 240         if (err)
 241                 return err;
 242
 243         /*
 244          * In order to force the compiler to emit data independent Sbox lookups
 245          * at the start of each block, xor the first round key with values at
 246          * fixed indexes in the Sbox. This will need to be repeated each time
 247          * the key is used, which will pull the entire Sbox into the D-cache
 248          * before any data dependent Sbox lookups are performed.
 249          */
 250         ctx->key_enc[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128];
 251         ctx->key_enc[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160];
 252         ctx->key_enc[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192];
 253         ctx->key_enc[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224];
 254
 255         ctx->key_dec[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128];
 256         ctx->key_dec[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160];
 257         ctx->key_dec[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192];
 258         ctx->key_dec[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224];
 259
 260         return 0;
 261 }
 262
 263 static void aesti_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 264 {
 265         const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
 266         const u32 *rkp = ctx->key_enc + 4;
 267         int rounds = 6 + ctx->key_length / 4;
 268         u32 st0[4], st1[4];
 269         unsigned long flags;
 270         int round;
 271
 272         st0[0] = ctx->key_enc[0] ^ get_unaligned_le32(in);
 273         st0[1] = ctx->key_enc[1] ^ get_unaligned_le32(in + 4);
 274         st0[2] = ctx->key_enc[2] ^ get_unaligned_le32(in + 8);
 275         st0[3] = ctx->key_enc[3] ^ get_unaligned_le32(in + 12);
 276
 277         /*
 278          * Temporarily disable interrupts to avoid races where cachelines are
 279          * evicted when the CPU is interrupted to do something else.
 280          */
 281         local_irq_save(flags);
 282
 283         st0[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128];
 284         st0[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160];
 285         st0[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192];
 286         st0[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224];
 287
 288         for (round = 0;; round += 2, rkp += 8) {
 289                 st1[0] = mix_columns(subshift(st0, 0)) ^ rkp[0];
 290                 st1[1] = mix_columns(subshift(st0, 1)) ^ rkp[1];
 291                 st1[2] = mix_columns(subshift(st0, 2)) ^ rkp[2];
 292                 st1[3] = mix_columns(subshift(st0, 3)) ^ rkp[3];
 293
 294                 if (round == rounds - 2)
 295                         break;
 296
 297                 st0[0] = mix_columns(subshift(st1, 0)) ^ rkp[4];
 298                 st0[1] = mix_columns(subshift(st1, 1)) ^ rkp[5];
 299                 st0[2] = mix_columns(subshift(st1, 2)) ^ rkp[6];
 300                 st0[3] = mix_columns(subshift(st1, 3)) ^ rkp[7];
 301         }
 302
 303         put_unaligned_le32(subshift(st1, 0) ^ rkp[4], out);
 304         put_unaligned_le32(subshift(st1, 1) ^ rkp[5], out + 4);
 305         put_unaligned_le32(subshift(st1, 2) ^ rkp[6], out + 8);
 306         put_unaligned_le32(subshift(st1, 3) ^ rkp[7], out + 12);
 307
 308         local_irq_restore(flags);
 309 }
 310
 311 static void aesti_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 312 {
 313         const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
 314         const u32 *rkp = ctx->key_dec + 4;
 315         int rounds = 6 + ctx->key_length / 4;
 316         u32 st0[4], st1[4];
 317         unsigned long flags;
 318         int round;
 319
 320         st0[0] = ctx->key_dec[0] ^ get_unaligned_le32(in);
 321         st0[1] = ctx->key_dec[1] ^ get_unaligned_le32(in + 4);
 322         st0[2] = ctx->key_dec[2] ^ get_unaligned_le32(in + 8);
 323         st0[3] = ctx->key_dec[3] ^ get_unaligned_le32(in + 12);
 324
 325         /*
 326          * Temporarily disable interrupts to avoid races where cachelines are
 327          * evicted when the CPU is interrupted to do something else.
 328          */
 329         local_irq_save(flags);
 330
 331         st0[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128];
 332         st0[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160];
 333         st0[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192];
 334         st0[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224];
 335
 336         for (round = 0;; round += 2, rkp += 8) {
 337                 st1[0] = inv_mix_columns(inv_subshift(st0, 0)) ^ rkp[0];
 338                 st1[1] = inv_mix_columns(inv_subshift(st0, 1)) ^ rkp[1];
 339                 st1[2] = inv_mix_columns(inv_subshift(st0, 2)) ^ rkp[2];
 340                 st1[3] = inv_mix_columns(inv_subshift(st0, 3)) ^ rkp[3];
 341
 342                 if (round == rounds - 2)
 343                         break;
 344
 345                 st0[0] = inv_mix_columns(inv_subshift(st1, 0)) ^ rkp[4];
 346                 st0[1] = inv_mix_columns(inv_subshift(st1, 1)) ^ rkp[5];
 347                 st0[2] = inv_mix_columns(inv_subshift(st1, 2)) ^ rkp[6];
 348                 st0[3] = inv_mix_columns(inv_subshift(st1, 3)) ^ rkp[7];
 349         }
 350
 351         put_unaligned_le32(inv_subshift(st1, 0) ^ rkp[4], out);
 352         put_unaligned_le32(inv_subshift(st1, 1) ^ rkp[5], out + 4);
 353         put_unaligned_le32(inv_subshift(st1, 2) ^ rkp[6], out + 8);
 354         put_unaligned_le32(inv_subshift(st1, 3) ^ rkp[7], out + 12);
 355
 356         local_irq_restore(flags);
 357 }
 358
 359 static struct crypto_alg aes_alg = {
 360         .cra_name                       = "aes",
 361         .cra_driver_name                = "aes-fixed-time",
 362         .cra_priority                   = 100 + 1,
 363         .cra_flags                      = CRYPTO_ALG_TYPE_CIPHER,
 364         .cra_blocksize                  = AES_BLOCK_SIZE,
 365         .cra_ctxsize                    = sizeof(struct crypto_aes_ctx),
 366         .cra_module                     = THIS_MODULE,
 367
 368         .cra_cipher.cia_min_keysize     = AES_MIN_KEY_SIZE,
 369         .cra_cipher.cia_max_keysize     = AES_MAX_KEY_SIZE,
 370         .cra_cipher.cia_setkey          = aesti_set_key,
 371         .cra_cipher.cia_encrypt         = aesti_encrypt,
 372         .cra_cipher.cia_decrypt         = aesti_decrypt
 373 };
 374
 375 static int __init aes_init(void)
 376 {
 377         return crypto_register_alg(&aes_alg);
 378 }
 379
 380 static void __exit aes_fini(void)
 381 {
 382         crypto_unregister_alg(&aes_alg);
 383 }
 384
 385 module_init(aes_init);
 386 module_exit(aes_fini);
 387
 388 MODULE_DESCRIPTION("Generic fixed time AES");
 389 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 390 MODULE_LICENSE("GPL v2");