summaryrefslogtreecommitdiff
path: root/crypto/aes_ti.c
blob: 798fc9a2c8d609d07e74c9152751baa92a324e1d (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
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Scalar fixed time AES core transform
 *
 * Copyright (C) 2017 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 __aesti_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 __aesti_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,
};

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 (__aesti_sbox[in[pos] & 0xff]) ^
	       (__aesti_sbox[(in[(pos + 1) % 4] >>  8) & 0xff] <<  8) ^
	       (__aesti_sbox[(in[(pos + 2) % 4] >> 16) & 0xff] << 16) ^
	       (__aesti_sbox[(in[(pos + 3) % 4] >> 24) & 0xff] << 24);
}

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

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

static int aesti_expand_key(struct crypto_aes_ctx *ctx, const u8 *in_key,
			    unsigned int key_len)
{
	u32 kwords = key_len / sizeof(u32);
	u32 rc, i, j;

	if (key_len != AES_KEYSIZE_128 &&
	    key_len != AES_KEYSIZE_192 &&
	    key_len != AES_KEYSIZE_256)
		return -EINVAL;

	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 == 24) {
			if (i >= 7)
				break;
			rko[4] = rko[3] ^ rki[4];
			rko[5] = rko[4] ^ rki[5];
		} else if (key_len == 32) {
			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;
}

static int aesti_set_key(struct crypto_tfm *tfm, const u8 *in_key,
			 unsigned int key_len)
{
	struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
	int err;

	err = aesti_expand_key(ctx, in_key, key_len);
	if (err)
		return err;

	/*
	 * In order to force the compiler to emit data independent Sbox lookups
	 * at the start of each block, xor the first round key with values at
	 * fixed indexes in the Sbox. This will need to be repeated each time
	 * the key is used, which will pull the entire Sbox into the D-cache
	 * before any data dependent Sbox lookups are performed.
	 */
	ctx->key_enc[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128];
	ctx->key_enc[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160];
	ctx->key_enc[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192];
	ctx->key_enc[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224];

	ctx->key_dec[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128];
	ctx->key_dec[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160];
	ctx->key_dec[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192];
	ctx->key_dec[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224];

	return 0;
}

static void aesti_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
	const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
	const u32 *rkp = ctx->key_enc + 4;
	int rounds = 6 + ctx->key_length / 4;
	u32 st0[4], st1[4];
	unsigned long flags;
	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);

	/*
	 * Temporarily disable interrupts to avoid races where cachelines are
	 * evicted when the CPU is interrupted to do something else.
	 */
	local_irq_save(flags);

	st0[0] ^= __aesti_sbox[ 0] ^ __aesti_sbox[128];
	st0[1] ^= __aesti_sbox[32] ^ __aesti_sbox[160];
	st0[2] ^= __aesti_sbox[64] ^ __aesti_sbox[192];
	st0[3] ^= __aesti_sbox[96] ^ __aesti_sbox[224];

	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);

	local_irq_restore(flags);
}

static void aesti_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
	const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
	const u32 *rkp = ctx->key_dec + 4;
	int rounds = 6 + ctx->key_length / 4;
	u32 st0[4], st1[4];
	unsigned long flags;
	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);

	/*
	 * Temporarily disable interrupts to avoid races where cachelines are
	 * evicted when the CPU is interrupted to do something else.
	 */
	local_irq_save(flags);

	st0[0] ^= __aesti_inv_sbox[ 0] ^ __aesti_inv_sbox[128];
	st0[1] ^= __aesti_inv_sbox[32] ^ __aesti_inv_sbox[160];
	st0[2] ^= __aesti_inv_sbox[64] ^ __aesti_inv_sbox[192];
	st0[3] ^= __aesti_inv_sbox[96] ^ __aesti_inv_sbox[224];

	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);

	local_irq_restore(flags);
}

static struct crypto_alg aes_alg = {
	.cra_name			= "aes",
	.cra_driver_name		= "aes-fixed-time",
	.cra_priority			= 100 + 1,
	.cra_flags			= CRYPTO_ALG_TYPE_CIPHER,
	.cra_blocksize			= AES_BLOCK_SIZE,
	.cra_ctxsize			= sizeof(struct crypto_aes_ctx),
	.cra_module			= THIS_MODULE,

	.cra_cipher.cia_min_keysize	= AES_MIN_KEY_SIZE,
	.cra_cipher.cia_max_keysize	= AES_MAX_KEY_SIZE,
	.cra_cipher.cia_setkey		= aesti_set_key,
	.cra_cipher.cia_encrypt		= aesti_encrypt,
	.cra_cipher.cia_decrypt		= aesti_decrypt
};

static int __init aes_init(void)
{
	return crypto_register_alg(&aes_alg);
}

static void __exit aes_fini(void)
{
	crypto_unregister_alg(&aes_alg);
}

module_init(aes_init);
module_exit(aes_fini);

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