lib/crypto/aes.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
mul_by_x
mul_by_x2
mix_columns
inv_mix_columns
subshift
inv_subshift
subw
aes_expandkey
aes_encrypt
aes_decrypt
   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2017-2019 Linaro Ltd <ard.biesheuvel@linaro.org>
   4  */
   5 
   6 #include <crypto/aes.h>
   7 #include <linux/crypto.h>
   8 #include <linux/module.h>
   9 #include <asm/unaligned.h>
  10 
  11 /*
  12  * Emit the sbox as volatile const to prevent the compiler from doing
  13  * constant folding on sbox references involving fixed indexes.
  14  */
  15 static volatile const u8 __cacheline_aligned aes_sbox[] = {
  16         0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
  17         0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  18         0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
  19         0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  20         0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
  21         0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  22         0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
  23         0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  24         0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
  25         0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  26         0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
  27         0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  28         0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
  29         0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  30         0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
  31         0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  32         0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
  33         0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  34         0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
  35         0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  36         0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
  37         0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  38         0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
  39         0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  40         0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
  41         0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  42         0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
  43         0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  44         0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
  45         0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  46         0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
  47         0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
  48 };
  49 
  50 static volatile const u8 __cacheline_aligned aes_inv_sbox[] = {
  51         0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
  52         0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  53         0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
  54         0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  55         0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
  56         0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  57         0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
  58         0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
  59         0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
  60         0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
  61         0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
  62         0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
  63         0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
  64         0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
  65         0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
  66         0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
  67         0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
  68         0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
  69         0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
  70         0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
  71         0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
  72         0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
  73         0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
  74         0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
  75         0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
  76         0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
  77         0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
  78         0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
  79         0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
  80         0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
  81         0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
  82         0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
  83 };
  84 
  85 extern const u8 crypto_aes_sbox[256] __alias(aes_sbox);
  86 extern const u8 crypto_aes_inv_sbox[256] __alias(aes_inv_sbox);
  87 
  88 EXPORT_SYMBOL(crypto_aes_sbox);
  89 EXPORT_SYMBOL(crypto_aes_inv_sbox);
  90 
  91 static u32 mul_by_x(u32 w)
  92 {
  93         u32 x = w & 0x7f7f7f7f;
  94         u32 y = w & 0x80808080;
  95 
  96         /* multiply by polynomial 'x' (0b10) in GF(2^8) */
  97         return (x << 1) ^ (y >> 7) * 0x1b;
  98 }
  99 
 100 static u32 mul_by_x2(u32 w)
 101 {
 102         u32 x = w & 0x3f3f3f3f;
 103         u32 y = w & 0x80808080;
 104         u32 z = w & 0x40404040;
 105 
 106         /* multiply by polynomial 'x^2' (0b100) in GF(2^8) */
 107         return (x << 2) ^ (y >> 7) * 0x36 ^ (z >> 6) * 0x1b;
 108 }
 109 
 110 static u32 mix_columns(u32 x)
 111 {
 112         /*
 113          * Perform the following matrix multiplication in GF(2^8)
 114          *
 115          * | 0x2 0x3 0x1 0x1 |   | x[0] |
 116          * | 0x1 0x2 0x3 0x1 |   | x[1] |
 117          * | 0x1 0x1 0x2 0x3 | x | x[2] |
 118          * | 0x3 0x1 0x1 0x2 |   | x[3] |
 119          */
 120         u32 y = mul_by_x(x) ^ ror32(x, 16);
 121 
 122         return y ^ ror32(x ^ y, 8);
 123 }
 124 
 125 static u32 inv_mix_columns(u32 x)
 126 {
 127         /*
 128          * Perform the following matrix multiplication in GF(2^8)
 129          *
 130          * | 0xe 0xb 0xd 0x9 |   | x[0] |
 131          * | 0x9 0xe 0xb 0xd |   | x[1] |
 132          * | 0xd 0x9 0xe 0xb | x | x[2] |
 133          * | 0xb 0xd 0x9 0xe |   | x[3] |
 134          *
 135          * which can conveniently be reduced to
 136          *
 137          * | 0x2 0x3 0x1 0x1 |   | 0x5 0x0 0x4 0x0 |   | x[0] |
 138          * | 0x1 0x2 0x3 0x1 |   | 0x0 0x5 0x0 0x4 |   | x[1] |
 139          * | 0x1 0x1 0x2 0x3 | x | 0x4 0x0 0x5 0x0 | x | x[2] |
 140          * | 0x3 0x1 0x1 0x2 |   | 0x0 0x4 0x0 0x5 |   | x[3] |
 141          */
 142         u32 y = mul_by_x2(x);
 143 
 144         return mix_columns(x ^ y ^ ror32(y, 16));
 145 }
 146 
 147 static __always_inline u32 subshift(u32 in[], int pos)
 148 {
 149         return (aes_sbox[in[pos] & 0xff]) ^
 150                (aes_sbox[(in[(pos + 1) % 4] >>  8) & 0xff] <<  8) ^
 151                (aes_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
 152                (aes_sbox[(in[(pos + 3) % 4] >> 24) & 0xff] << 24);
 153 }
 154 
 155 static __always_inline u32 inv_subshift(u32 in[], int pos)
 156 {
 157         return (aes_inv_sbox[in[pos] & 0xff]) ^
 158                (aes_inv_sbox[(in[(pos + 3) % 4] >>  8) & 0xff] <<  8) ^
 159                (aes_inv_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
 160                (aes_inv_sbox[(in[(pos + 1) % 4] >> 24) & 0xff] << 24);
 161 }
 162 
 163 static u32 subw(u32 in)
 164 {
 165         return (aes_sbox[in & 0xff]) ^
 166                (aes_sbox[(in >>  8) & 0xff] <<  8) ^
 167                (aes_sbox[(in >> 16) & 0xff] << 16) ^
 168                (aes_sbox[(in >> 24) & 0xff] << 24);
 169 }
 170 
 171 /**
 172  * aes_expandkey - Expands the AES key as described in FIPS-197
 173  * @ctx:        The location where the computed key will be stored.
 174  * @in_key:     The supplied key.
 175  * @key_len:    The length of the supplied key.
 176  *
 177  * Returns 0 on success. The function fails only if an invalid key size (or
 178  * pointer) is supplied.
 179  * The expanded key size is 240 bytes (max of 14 rounds with a unique 16 bytes
 180  * key schedule plus a 16 bytes key which is used before the first round).
 181  * The decryption key is prepared for the "Equivalent Inverse Cipher" as
 182  * described in FIPS-197. The first slot (16 bytes) of each key (enc or dec) is
 183  * for the initial combination, the second slot for the first round and so on.
 184  */
 185 int aes_expandkey(struct crypto_aes_ctx *ctx, const u8 *in_key,
 186                   unsigned int key_len)
 187 {
 188         u32 kwords = key_len / sizeof(u32);
 189         u32 rc, i, j;
 190         int err;
 191 
 192         err = aes_check_keylen(key_len);
 193         if (err)
 194                 return err;
 195 
 196         ctx->key_length = key_len;
 197 
 198         for (i = 0; i < kwords; i++)
 199                 ctx->key_enc[i] = get_unaligned_le32(in_key + i * sizeof(u32));
 200 
 201         for (i = 0, rc = 1; i < 10; i++, rc = mul_by_x(rc)) {
 202                 u32 *rki = ctx->key_enc + (i * kwords);
 203                 u32 *rko = rki + kwords;
 204 
 205                 rko[0] = ror32(subw(rki[kwords - 1]), 8) ^ rc ^ rki[0];
 206                 rko[1] = rko[0] ^ rki[1];
 207                 rko[2] = rko[1] ^ rki[2];
 208                 rko[3] = rko[2] ^ rki[3];
 209 
 210                 if (key_len == AES_KEYSIZE_192) {
 211                         if (i >= 7)
 212                                 break;
 213                         rko[4] = rko[3] ^ rki[4];
 214                         rko[5] = rko[4] ^ rki[5];
 215                 } else if (key_len == AES_KEYSIZE_256) {
 216                         if (i >= 6)
 217                                 break;
 218                         rko[4] = subw(rko[3]) ^ rki[4];
 219                         rko[5] = rko[4] ^ rki[5];
 220                         rko[6] = rko[5] ^ rki[6];
 221                         rko[7] = rko[6] ^ rki[7];
 222                 }
 223         }
 224 
 225         /*
 226          * Generate the decryption keys for the Equivalent Inverse Cipher.
 227          * This involves reversing the order of the round keys, and applying
 228          * the Inverse Mix Columns transformation to all but the first and
 229          * the last one.
 230          */
 231         ctx->key_dec[0] = ctx->key_enc[key_len + 24];
 232         ctx->key_dec[1] = ctx->key_enc[key_len + 25];
 233         ctx->key_dec[2] = ctx->key_enc[key_len + 26];
 234         ctx->key_dec[3] = ctx->key_enc[key_len + 27];
 235 
 236         for (i = 4, j = key_len + 20; j > 0; i += 4, j -= 4) {
 237                 ctx->key_dec[i]     = inv_mix_columns(ctx->key_enc[j]);
 238                 ctx->key_dec[i + 1] = inv_mix_columns(ctx->key_enc[j + 1]);
 239                 ctx->key_dec[i + 2] = inv_mix_columns(ctx->key_enc[j + 2]);
 240                 ctx->key_dec[i + 3] = inv_mix_columns(ctx->key_enc[j + 3]);
 241         }
 242 
 243         ctx->key_dec[i]     = ctx->key_enc[0];
 244         ctx->key_dec[i + 1] = ctx->key_enc[1];
 245         ctx->key_dec[i + 2] = ctx->key_enc[2];
 246         ctx->key_dec[i + 3] = ctx->key_enc[3];
 247 
 248         return 0;
 249 }
 250 EXPORT_SYMBOL(aes_expandkey);
 251 
 252 /**
 253  * aes_encrypt - Encrypt a single AES block
 254  * @ctx:        Context struct containing the key schedule
 255  * @out:        Buffer to store the ciphertext
 256  * @in:         Buffer containing the plaintext
 257  */
 258 void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
 259 {
 260         const u32 *rkp = ctx->key_enc + 4;
 261         int rounds = 6 + ctx->key_length / 4;
 262         u32 st0[4], st1[4];
 263         int round;
 264 
 265         st0[0] = ctx->key_enc[0] ^ get_unaligned_le32(in);
 266         st0[1] = ctx->key_enc[1] ^ get_unaligned_le32(in + 4);
 267         st0[2] = ctx->key_enc[2] ^ get_unaligned_le32(in + 8);
 268         st0[3] = ctx->key_enc[3] ^ get_unaligned_le32(in + 12);
 269 
 270         /*
 271          * Force the compiler to emit data independent Sbox references,
 272          * by xoring the input with Sbox values that are known to add up
 273          * to zero. This pulls the entire Sbox into the D-cache before any
 274          * data dependent lookups are done.
 275          */
 276         st0[0] ^= aes_sbox[ 0] ^ aes_sbox[ 64] ^ aes_sbox[134] ^ aes_sbox[195];
 277         st0[1] ^= aes_sbox[16] ^ aes_sbox[ 82] ^ aes_sbox[158] ^ aes_sbox[221];
 278         st0[2] ^= aes_sbox[32] ^ aes_sbox[ 96] ^ aes_sbox[160] ^ aes_sbox[234];
 279         st0[3] ^= aes_sbox[48] ^ aes_sbox[112] ^ aes_sbox[186] ^ aes_sbox[241];
 280 
 281         for (round = 0;; round += 2, rkp += 8) {
 282                 st1[0] = mix_columns(subshift(st0, 0)) ^ rkp[0];
 283                 st1[1] = mix_columns(subshift(st0, 1)) ^ rkp[1];
 284                 st1[2] = mix_columns(subshift(st0, 2)) ^ rkp[2];
 285                 st1[3] = mix_columns(subshift(st0, 3)) ^ rkp[3];
 286 
 287                 if (round == rounds - 2)
 288                         break;
 289 
 290                 st0[0] = mix_columns(subshift(st1, 0)) ^ rkp[4];
 291                 st0[1] = mix_columns(subshift(st1, 1)) ^ rkp[5];
 292                 st0[2] = mix_columns(subshift(st1, 2)) ^ rkp[6];
 293                 st0[3] = mix_columns(subshift(st1, 3)) ^ rkp[7];
 294         }
 295 
 296         put_unaligned_le32(subshift(st1, 0) ^ rkp[4], out);
 297         put_unaligned_le32(subshift(st1, 1) ^ rkp[5], out + 4);
 298         put_unaligned_le32(subshift(st1, 2) ^ rkp[6], out + 8);
 299         put_unaligned_le32(subshift(st1, 3) ^ rkp[7], out + 12);
 300 }
 301 EXPORT_SYMBOL(aes_encrypt);
 302 
 303 /**
 304  * aes_decrypt - Decrypt a single AES block
 305  * @ctx:        Context struct containing the key schedule
 306  * @out:        Buffer to store the plaintext
 307  * @in:         Buffer containing the ciphertext
 308  */
 309 void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
 310 {
 311         const u32 *rkp = ctx->key_dec + 4;
 312         int rounds = 6 + ctx->key_length / 4;
 313         u32 st0[4], st1[4];
 314         int round;
 315 
 316         st0[0] = ctx->key_dec[0] ^ get_unaligned_le32(in);
 317         st0[1] = ctx->key_dec[1] ^ get_unaligned_le32(in + 4);
 318         st0[2] = ctx->key_dec[2] ^ get_unaligned_le32(in + 8);
 319         st0[3] = ctx->key_dec[3] ^ get_unaligned_le32(in + 12);
 320 
 321         /*
 322          * Force the compiler to emit data independent Sbox references,
 323          * by xoring the input with Sbox values that are known to add up
 324          * to zero. This pulls the entire Sbox into the D-cache before any
 325          * data dependent lookups are done.
 326          */
 327         st0[0] ^= aes_inv_sbox[ 0] ^ aes_inv_sbox[ 64] ^ aes_inv_sbox[129] ^ aes_inv_sbox[200];
 328         st0[1] ^= aes_inv_sbox[16] ^ aes_inv_sbox[ 83] ^ aes_inv_sbox[150] ^ aes_inv_sbox[212];
 329         st0[2] ^= aes_inv_sbox[32] ^ aes_inv_sbox[ 96] ^ aes_inv_sbox[160] ^ aes_inv_sbox[236];
 330         st0[3] ^= aes_inv_sbox[48] ^ aes_inv_sbox[112] ^ aes_inv_sbox[187] ^ aes_inv_sbox[247];
 331 
 332         for (round = 0;; round += 2, rkp += 8) {
 333                 st1[0] = inv_mix_columns(inv_subshift(st0, 0)) ^ rkp[0];
 334                 st1[1] = inv_mix_columns(inv_subshift(st0, 1)) ^ rkp[1];
 335                 st1[2] = inv_mix_columns(inv_subshift(st0, 2)) ^ rkp[2];
 336                 st1[3] = inv_mix_columns(inv_subshift(st0, 3)) ^ rkp[3];
 337 
 338                 if (round == rounds - 2)
 339                         break;
 340 
 341                 st0[0] = inv_mix_columns(inv_subshift(st1, 0)) ^ rkp[4];
 342                 st0[1] = inv_mix_columns(inv_subshift(st1, 1)) ^ rkp[5];
 343                 st0[2] = inv_mix_columns(inv_subshift(st1, 2)) ^ rkp[6];
 344                 st0[3] = inv_mix_columns(inv_subshift(st1, 3)) ^ rkp[7];
 345         }
 346 
 347         put_unaligned_le32(inv_subshift(st1, 0) ^ rkp[4], out);
 348         put_unaligned_le32(inv_subshift(st1, 1) ^ rkp[5], out + 4);
 349         put_unaligned_le32(inv_subshift(st1, 2) ^ rkp[6], out + 8);
 350         put_unaligned_le32(inv_subshift(st1, 3) ^ rkp[7], out + 12);
 351 }
 352 EXPORT_SYMBOL(aes_decrypt);
 353 
 354 MODULE_DESCRIPTION("Generic AES library");
 355 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 356 MODULE_LICENSE("GPL v2");
/* [<][>][^][v][top][bottom][index][help] */
root/lib/crypto/aes.c

DEFINITIONS
