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 0x2 | | 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 unsigned long flags; 273 int round; 274 275 st0[0] = ctx->key_enc[0] ^ get_unaligned_le32(in); 276 st0[1] = ctx->key_enc[1] ^ get_unaligned_le32(in + 4); 277 st0[2] = ctx->key_enc[2] ^ get_unaligned_le32(in + 8); 278 st0[3] = ctx->key_enc[3] ^ get_unaligned_le32(in + 12); 279 280 /* 281 * Temporarily disable interrupts to avoid races where cachelines are 282 * evicted when the CPU is interrupted to do something else. 283 */ 284 local_irq_save(flags); 285 286 st0[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128]; 287 st0[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160]; 288 st0[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192]; 289 st0[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224]; 290 291 for (round = 0;; round += 2, rkp += 8) { 292 st1[0] = mix_columns(subshift(st0, 0)) ^ rkp[0]; 293 st1[1] = mix_columns(subshift(st0, 1)) ^ rkp[1]; 294 st1[2] = mix_columns(subshift(st0, 2)) ^ rkp[2]; 295 st1[3] = mix_columns(subshift(st0, 3)) ^ rkp[3]; 296 297 if (round == rounds - 2) 298 break; 299 300 st0[0] = mix_columns(subshift(st1, 0)) ^ rkp[4]; 301 st0[1] = mix_columns(subshift(st1, 1)) ^ rkp[5]; 302 st0[2] = mix_columns(subshift(st1, 2)) ^ rkp[6]; 303 st0[3] = mix_columns(subshift(st1, 3)) ^ rkp[7]; 304 } 305 306 put_unaligned_le32(subshift(st1, 0) ^ rkp[4], out); 307 put_unaligned_le32(subshift(st1, 1) ^ rkp[5], out + 4); 308 put_unaligned_le32(subshift(st1, 2) ^ rkp[6], out + 8); 309 put_unaligned_le32(subshift(st1, 3) ^ rkp[7], out + 12); 310 311 local_irq_restore(flags); 312 } 313 314 static void aesti_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in) 315 { 316 const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm); 317 const u32 *rkp = ctx->key_dec + 4; 318 int rounds = 6 + ctx->key_length / 4; 319 u32 st0[4], st1[4]; 320 unsigned long flags; 321 int round; 322 323 st0[0] = ctx->key_dec[0] ^ get_unaligned_le32(in); 324 st0[1] = ctx->key_dec[1] ^ get_unaligned_le32(in + 4); 325 st0[2] = ctx->key_dec[2] ^ get_unaligned_le32(in + 8); 326 st0[3] = ctx->key_dec[3] ^ get_unaligned_le32(in + 12); 327 328 /* 329 * Temporarily disable interrupts to avoid races where cachelines are 330 * evicted when the CPU is interrupted to do something else. 331 */ 332 local_irq_save(flags); 333 334 st0[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128]; 335 st0[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160]; 336 st0[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192]; 337 st0[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224]; 338 339 for (round = 0;; round += 2, rkp += 8) { 340 st1[0] = inv_mix_columns(inv_subshift(st0, 0)) ^ rkp[0]; 341 st1[1] = inv_mix_columns(inv_subshift(st0, 1)) ^ rkp[1]; 342 st1[2] = inv_mix_columns(inv_subshift(st0, 2)) ^ rkp[2]; 343 st1[3] = inv_mix_columns(inv_subshift(st0, 3)) ^ rkp[3]; 344 345 if (round == rounds - 2) 346 break; 347 348 st0[0] = inv_mix_columns(inv_subshift(st1, 0)) ^ rkp[4]; 349 st0[1] = inv_mix_columns(inv_subshift(st1, 1)) ^ rkp[5]; 350 st0[2] = inv_mix_columns(inv_subshift(st1, 2)) ^ rkp[6]; 351 st0[3] = inv_mix_columns(inv_subshift(st1, 3)) ^ rkp[7]; 352 } 353 354 put_unaligned_le32(inv_subshift(st1, 0) ^ rkp[4], out); 355 put_unaligned_le32(inv_subshift(st1, 1) ^ rkp[5], out + 4); 356 put_unaligned_le32(inv_subshift(st1, 2) ^ rkp[6], out + 8); 357 put_unaligned_le32(inv_subshift(st1, 3) ^ rkp[7], out + 12); 358 359 local_irq_restore(flags); 360 } 361 362 static struct crypto_alg aes_alg = { 363 .cra_name = "aes", 364 .cra_driver_name = "aes-fixed-time", 365 .cra_priority = 100 + 1, 366 .cra_flags = CRYPTO_ALG_TYPE_CIPHER, 367 .cra_blocksize = AES_BLOCK_SIZE, 368 .cra_ctxsize = sizeof(struct crypto_aes_ctx), 369 .cra_module = THIS_MODULE, 370 371 .cra_cipher.cia_min_keysize = AES_MIN_KEY_SIZE, 372 .cra_cipher.cia_max_keysize = AES_MAX_KEY_SIZE, 373 .cra_cipher.cia_setkey = aesti_set_key, 374 .cra_cipher.cia_encrypt = aesti_encrypt, 375 .cra_cipher.cia_decrypt = aesti_decrypt 376 }; 377 378 static int __init aes_init(void) 379 { 380 return crypto_register_alg(&aes_alg); 381 } 382 383 static void __exit aes_fini(void) 384 { 385 crypto_unregister_alg(&aes_alg); 386 } 387 388 module_init(aes_init); 389 module_exit(aes_fini); 390 391 MODULE_DESCRIPTION("Generic fixed time AES"); 392 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>"); 393 MODULE_LICENSE("GPL v2"); 394