aboutsummaryrefslogtreecommitdiff
path: root/lib/crypto/aes.c
blob: 827fe89922fff03b9be8e1fcc2d26541c06713bb (plain)
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
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2017-2019 Linaro Ltd <ard.biesheuvel@linaro.org>
 */

#include <crypto/aes.h>
#include <linux/crypto.h>
#include <linux/module.h>
#include <asm/unaligned.h>

/*
 * Emit the sbox as volatile const to prevent the compiler from doing
 * constant folding on sbox references involving fixed indexes.
 */
static volatile const u8 __cacheline_aligned aes_sbox[] = {
	0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
	0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
	0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
	0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
	0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
	0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
	0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
	0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
	0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
	0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
	0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
	0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
	0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
	0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
	0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
	0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
	0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
	0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
	0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
	0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
	0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
	0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
	0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
	0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
	0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
	0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
	0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
	0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
	0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
	0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
	0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
	0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
};

static volatile const u8 __cacheline_aligned aes_inv_sbox[] = {
	0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
	0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
	0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
	0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
	0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
	0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
	0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
	0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
	0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
	0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
	0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
	0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
	0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
	0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
	0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
	0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
	0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
	0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
	0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
	0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
	0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
	0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
	0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
	0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
	0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
	0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
	0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
	0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
	0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
	0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
	0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
	0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
};

extern const u8 crypto_aes_sbox[256] __alias(aes_sbox);
extern const u8 crypto_aes_inv_sbox[256] __alias(aes_inv_sbox);

EXPORT_SYMBOL(crypto_aes_sbox);
EXPORT_SYMBOL(crypto_aes_inv_sbox);

static u32 mul_by_x(u32 w)
{
	u32 x = w & 0x7f7f7f7f;
	u32 y = w & 0x80808080;

	/* multiply by polynomial 'x' (0b10) in GF(2^8) */
	return (x << 1) ^ (y >> 7) * 0x1b;
}

static u32 mul_by_x2(u32 w)
{
	u32 x = w & 0x3f3f3f3f;
	u32 y = w & 0x80808080;
	u32 z = w & 0x40404040;

	/* multiply by polynomial 'x^2' (0b100) in GF(2^8) */
	return (x << 2) ^ (y >> 7) * 0x36 ^ (z >> 6) * 0x1b;
}

static u32 mix_columns(u32 x)
{
	/*
	 * Perform the following matrix multiplication in GF(2^8)
	 *
	 * | 0x2 0x3 0x1 0x1 |   | x[0] |
	 * | 0x1 0x2 0x3 0x1 |   | x[1] |
	 * | 0x1 0x1 0x2 0x3 | x | x[2] |
	 * | 0x3 0x1 0x1 0x2 |   | x[3] |
	 */
	u32 y = mul_by_x(x) ^ ror32(x, 16);

	return y ^ ror32(x ^ y, 8);
}

static u32 inv_mix_columns(u32 x)
{
	/*
	 * Perform the following matrix multiplication in GF(2^8)
	 *
	 * | 0xe 0xb 0xd 0x9 |   | x[0] |
	 * | 0x9 0xe 0xb 0xd |   | x[1] |
	 * | 0xd 0x9 0xe 0xb | x | x[2] |
	 * | 0xb 0xd 0x9 0xe |   | x[3] |
	 *
	 * which can conveniently be reduced to
	 *
	 * | 0x2 0x3 0x1 0x1 |   | 0x5 0x0 0x4 0x0 |   | x[0] |
	 * | 0x1 0x2 0x3 0x1 |   | 0x0 0x5 0x0 0x4 |   | x[1] |
	 * | 0x1 0x1 0x2 0x3 | x | 0x4 0x0 0x5 0x0 | x | x[2] |
	 * | 0x3 0x1 0x1 0x2 |   | 0x0 0x4 0x0 0x5 |   | x[3] |
	 */
	u32 y = mul_by_x2(x);

	return mix_columns(x ^ y ^ ror32(y, 16));
}

static __always_inline u32 subshift(u32 in[], int pos)
{
	return (aes_sbox[in[pos] & 0xff]) ^
	       (aes_sbox[(in[(pos + 1) % 4] >>  8) & 0xff] <<  8) ^
	       (aes_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
	       (aes_sbox[(in[(pos + 3) % 4] >> 24) & 0xff] << 24);
}

static __always_inline u32 inv_subshift(u32 in[], int pos)
{
	return (aes_inv_sbox[in[pos] & 0xff]) ^
	       (aes_inv_sbox[(in[(pos + 3) % 4] >>  8) & 0xff] <<  8) ^
	       (aes_inv_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
	       (aes_inv_sbox[(in[(pos + 1) % 4] >> 24) & 0xff] << 24);
}

static u32 subw(u32 in)
{
	return (aes_sbox[in & 0xff]) ^
	       (aes_sbox[(in >>  8) & 0xff] <<  8) ^
	       (aes_sbox[(in >> 16) & 0xff] << 16) ^
	       (aes_sbox[(in >> 24) & 0xff] << 24);
}

/**
 * aes_expandkey - Expands the AES key as described in FIPS-197
 * @ctx:	The location where the computed key will be stored.
 * @in_key:	The supplied key.
 * @key_len:	The length of the supplied key.
 *
 * Returns 0 on success. The function fails only if an invalid key size (or
 * pointer) is supplied.
 * The expanded key size is 240 bytes (max of 14 rounds with a unique 16 bytes
 * key schedule plus a 16 bytes key which is used before the first round).
 * The decryption key is prepared for the "Equivalent Inverse Cipher" as
 * described in FIPS-197. The first slot (16 bytes) of each key (enc or dec) is
 * for the initial combination, the second slot for the first round and so on.
 */
int aes_expandkey(struct crypto_aes_ctx *ctx, const u8 *in_key,
		  unsigned int key_len)
{
	u32 kwords = key_len / sizeof(u32);
	u32 rc, i, j;
	int err;

	err = aes_check_keylen(key_len);
	if (err)
		return err;

	ctx->key_length = key_len;

	for (i = 0; i < kwords; i++)
		ctx->key_enc[i] = get_unaligned_le32(in_key + i * sizeof(u32));

	for (i = 0, rc = 1; i < 10; i++, rc = mul_by_x(rc)) {
		u32 *rki = ctx->key_enc + (i * kwords);
		u32 *rko = rki + kwords;

		rko[0] = ror32(subw(rki[kwords - 1]), 8) ^ rc ^ rki[0];
		rko[1] = rko[0] ^ rki[1];
		rko[2] = rko[1] ^ rki[2];
		rko[3] = rko[2] ^ rki[3];

		if (key_len == AES_KEYSIZE_192) {
			if (i >= 7)
				break;
			rko[4] = rko[3] ^ rki[4];
			rko[5] = rko[4] ^ rki[5];
		} else if (key_len == AES_KEYSIZE_256) {
			if (i >= 6)
				break;
			rko[4] = subw(rko[3]) ^ rki[4];
			rko[5] = rko[4] ^ rki[5];
			rko[6] = rko[5] ^ rki[6];
			rko[7] = rko[6] ^ rki[7];
		}
	}

	/*
	 * Generate the decryption keys for the Equivalent Inverse Cipher.
	 * This involves reversing the order of the round keys, and applying
	 * the Inverse Mix Columns transformation to all but the first and
	 * the last one.
	 */
	ctx->key_dec[0] = ctx->key_enc[key_len + 24];
	ctx->key_dec[1] = ctx->key_enc[key_len + 25];
	ctx->key_dec[2] = ctx->key_enc[key_len + 26];
	ctx->key_dec[3] = ctx->key_enc[key_len + 27];

	for (i = 4, j = key_len + 20; j > 0; i += 4, j -= 4) {
		ctx->key_dec[i]     = inv_mix_columns(ctx->key_enc[j]);
		ctx->key_dec[i + 1] = inv_mix_columns(ctx->key_enc[j + 1]);
		ctx->key_dec[i + 2] = inv_mix_columns(ctx->key_enc[j + 2]);
		ctx->key_dec[i + 3] = inv_mix_columns(ctx->key_enc[j + 3]);
	}

	ctx->key_dec[i]     = ctx->key_enc[0];
	ctx->key_dec[i + 1] = ctx->key_enc[1];
	ctx->key_dec[i + 2] = ctx->key_enc[2];
	ctx->key_dec[i + 3] = ctx->key_enc[3];

	return 0;
}
EXPORT_SYMBOL(aes_expandkey);

/**
 * aes_encrypt - Encrypt a single AES block
 * @ctx:	Context struct containing the key schedule
 * @out:	Buffer to store the ciphertext
 * @in:		Buffer containing the plaintext
 */
void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
{
	const u32 *rkp = ctx->key_enc + 4;
	int rounds = 6 + ctx->key_length / 4;
	u32 st0[4], st1[4];
	int round;

	st0[0] = ctx->key_enc[0] ^ get_unaligned_le32(in);
	st0[1] = ctx->key_enc[1] ^ get_unaligned_le32(in + 4);
	st0[2] = ctx->key_enc[2] ^ get_unaligned_le32(in + 8);
	st0[3] = ctx->key_enc[3] ^ get_unaligned_le32(in + 12);

	/*
	 * Force the compiler to emit data independent Sbox references,
	 * by xoring the input with Sbox values that are known to add up
	 * to zero. This pulls the entire Sbox into the D-cache before any
	 * data dependent lookups are done.
	 */
	st0[0] ^= aes_sbox[ 0] ^ aes_sbox[ 64] ^ aes_sbox[134] ^ aes_sbox[195];
	st0[1] ^= aes_sbox[16] ^ aes_sbox[ 82] ^ aes_sbox[158] ^ aes_sbox[221];
	st0[2] ^= aes_sbox[32] ^ aes_sbox[ 96] ^ aes_sbox[160] ^ aes_sbox[234];
	st0[3] ^= aes_sbox[48] ^ aes_sbox[112] ^ aes_sbox[186] ^ aes_sbox[241];

	for (round = 0;; round += 2, rkp += 8) {
		st1[0] = mix_columns(subshift(st0, 0)) ^ rkp[0];
		st1[1] = mix_columns(subshift(st0, 1)) ^ rkp[1];
		st1[2] = mix_columns(subshift(st0, 2)) ^ rkp[2];
		st1[3] = mix_columns(subshift(st0, 3)) ^ rkp[3];

		if (round == rounds - 2)
			break;

		st0[0] = mix_columns(subshift(st1, 0)) ^ rkp[4];
		st0[1] = mix_columns(subshift(st1, 1)) ^ rkp[5];
		st0[2] = mix_columns(subshift(st1, 2)) ^ rkp[6];
		st0[3] = mix_columns(subshift(st1, 3)) ^ rkp[7];
	}

	put_unaligned_le32(subshift(st1, 0) ^ rkp[4], out);
	put_unaligned_le32(subshift(st1, 1) ^ rkp[5], out + 4);
	put_unaligned_le32(subshift(st1, 2) ^ rkp[6], out + 8);
	put_unaligned_le32(subshift(st1, 3) ^ rkp[7], out + 12);
}
EXPORT_SYMBOL(aes_encrypt);

/**
 * aes_decrypt - Decrypt a single AES block
 * @ctx:	Context struct containing the key schedule
 * @out:	Buffer to store the plaintext
 * @in:		Buffer containing the ciphertext
 */
void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
{
	const u32 *rkp = ctx->key_dec + 4;
	int rounds = 6 + ctx->key_length / 4;
	u32 st0[4], st1[4];
	int round;

	st0[0] = ctx->key_dec[0] ^ get_unaligned_le32(in);
	st0[1] = ctx->key_dec[1] ^ get_unaligned_le32(in + 4);
	st0[2] = ctx->key_dec[2] ^ get_unaligned_le32(in + 8);
	st0[3] = ctx->key_dec[3] ^ get_unaligned_le32(in + 12);

	/*
	 * Force the compiler to emit data independent Sbox references,
	 * by xoring the input with Sbox values that are known to add up
	 * to zero. This pulls the entire Sbox into the D-cache before any
	 * data dependent lookups are done.
	 */
	st0[0] ^= aes_inv_sbox[ 0] ^ aes_inv_sbox[ 64] ^ aes_inv_sbox[129] ^ aes_inv_sbox[200];
	st0[1] ^= aes_inv_sbox[16] ^ aes_inv_sbox[ 83] ^ aes_inv_sbox[150] ^ aes_inv_sbox[212];
	st0[2] ^= aes_inv_sbox[32] ^ aes_inv_sbox[ 96] ^ aes_inv_sbox[160] ^ aes_inv_sbox[236];
	st0[3] ^= aes_inv_sbox[48] ^ aes_inv_sbox[112] ^ aes_inv_sbox[187] ^ aes_inv_sbox[247];

	for (round = 0;; round += 2, rkp += 8) {
		st1[0] = inv_mix_columns(inv_subshift(st0, 0)) ^ rkp[0];
		st1[1] = inv_mix_columns(inv_subshift(st0, 1)) ^ rkp[1];
		st1[2] = inv_mix_columns(inv_subshift(st0, 2)) ^ rkp[2];
		st1[3] = inv_mix_columns(inv_subshift(st0, 3)) ^ rkp[3];

		if (round == rounds - 2)
			break;

		st0[0] = inv_mix_columns(inv_subshift(st1, 0)) ^ rkp[4];
		st0[1] = inv_mix_columns(inv_subshift(st1, 1)) ^ rkp[5];
		st0[2] = inv_mix_columns(inv_subshift(st1, 2)) ^ rkp[6];
		st0[3] = inv_mix_columns(inv_subshift(st1, 3)) ^ rkp[7];
	}

	put_unaligned_le32(inv_subshift(st1, 0) ^ rkp[4], out);
	put_unaligned_le32(inv_subshift(st1, 1) ^ rkp[5], out + 4);
	put_unaligned_le32(inv_subshift(st1, 2) ^ rkp[6], out + 8);
	put_unaligned_le32(inv_subshift(st1, 3) ^ rkp[7], out + 12);
}
EXPORT_SYMBOL(aes_decrypt);

MODULE_DESCRIPTION("Generic AES library");
MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
MODULE_LICENSE("GPL v2");