summaryrefslogtreecommitdiff
path: root/crypto/gcm.c
blob: ad8b8b9aeef2bc051bc01043baabf707f37eff32 (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
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
/*
 * GCM: Galois/Counter Mode.
 *
 * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 */

#include <crypto/algapi.h>
#include <crypto/gf128mul.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "scatterwalk.h"

struct gcm_instance_ctx {
	struct crypto_spawn ctr;
};

struct crypto_gcm_ctx {
	struct crypto_ablkcipher *ctr;
	struct gf128mul_4k *gf128;
};

struct crypto_gcm_ghash_ctx {
	u32 bytes;
	u32 flags;
	struct gf128mul_4k *gf128;
	u8 buffer[16];
};

struct crypto_gcm_req_priv_ctx {
	u8 auth_tag[16];
	u8 counter[16];
	struct crypto_gcm_ghash_ctx ghash;
};

static void crypto_gcm_ghash_init(struct crypto_gcm_ghash_ctx *ctx, u32 flags,
				  struct gf128mul_4k *gf128)
{
	ctx->bytes = 0;
	ctx->flags = flags;
	ctx->gf128 = gf128;
	memset(ctx->buffer, 0, 16);
}

static void crypto_gcm_ghash_update(struct crypto_gcm_ghash_ctx *ctx,
				    const u8 *src, unsigned int srclen)
{
	u8 *dst = ctx->buffer;

	if (ctx->bytes) {
		int n = min(srclen, ctx->bytes);
		u8 *pos = dst + (16 - ctx->bytes);

		ctx->bytes -= n;
		srclen -= n;

		while (n--)
			*pos++ ^= *src++;

		if (!ctx->bytes)
			gf128mul_4k_lle((be128 *)dst, ctx->gf128);
	}

	while (srclen >= 16) {
		crypto_xor(dst, src, 16);
		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
		src += 16;
		srclen -= 16;
	}

	if (srclen) {
		ctx->bytes = 16 - srclen;
		while (srclen--)
			*dst++ ^= *src++;
	}
}

static void crypto_gcm_ghash_update_sg(struct crypto_gcm_ghash_ctx *ctx,
				       struct scatterlist *sg, int len)
{
	struct scatter_walk walk;
	u8 *src;
	int n;

	scatterwalk_start(&walk, sg);

	while (len) {
		n = scatterwalk_clamp(&walk, len);

		if (!n) {
			scatterwalk_start(&walk, sg_next(walk.sg));
			n = scatterwalk_clamp(&walk, len);
		}

		src = scatterwalk_map(&walk, 0);

		crypto_gcm_ghash_update(ctx, src, n);
		len -= n;

		scatterwalk_unmap(src, 0);
		scatterwalk_advance(&walk, n);
		scatterwalk_done(&walk, 0, len);
		if (len)
			crypto_yield(ctx->flags);
	}
}

static void crypto_gcm_ghash_flush(struct crypto_gcm_ghash_ctx *ctx)
{
	u8 *dst = ctx->buffer;

	if (ctx->bytes) {
		u8 *tmp = dst + (16 - ctx->bytes);

		while (ctx->bytes--)
			*tmp++ ^= 0;

		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
	}

	ctx->bytes = 0;
}

static void crypto_gcm_ghash_final_xor(struct crypto_gcm_ghash_ctx *ctx,
				       unsigned int authlen,
				       unsigned int cryptlen, u8 *dst)
{
	u8 *buf = ctx->buffer;
	u128 lengths;

	lengths.a = cpu_to_be64(authlen * 8);
	lengths.b = cpu_to_be64(cryptlen * 8);

	crypto_gcm_ghash_flush(ctx);
	crypto_xor(buf, (u8 *)&lengths, 16);
	gf128mul_4k_lle((be128 *)buf, ctx->gf128);
	crypto_xor(dst, buf, 16);
}

static inline void crypto_gcm_set_counter(u8 *counterblock, u32 value)
{
	*((u32 *)&counterblock[12]) = cpu_to_be32(value);
}

static int crypto_gcm_encrypt_counter(struct crypto_aead *aead, u8 *block,
				       u32 value, const u8 *iv)
{
	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
	struct crypto_ablkcipher *ctr = ctx->ctr;
	struct ablkcipher_request req;
	struct scatterlist sg;
	u8 counterblock[16];

	if (iv == NULL)
		memset(counterblock, 0, 12);
	else
		memcpy(counterblock, iv, 12);

	crypto_gcm_set_counter(counterblock, value);

	sg_init_one(&sg, block, 16);
	ablkcipher_request_set_tfm(&req, ctr);
	ablkcipher_request_set_crypt(&req, &sg, &sg, 16, counterblock);
	ablkcipher_request_set_callback(&req, 0, NULL, NULL);
	memset(block, 0, 16);
	return crypto_ablkcipher_encrypt(&req);
}

static int crypto_gcm_setkey(struct crypto_aead *aead, const u8 *key,
			     unsigned int keylen)
{
	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
	struct crypto_ablkcipher *ctr = ctx->ctr;
	int alignmask = crypto_ablkcipher_alignmask(ctr);
	u8 alignbuf[16+alignmask];
	u8 *hash = (u8 *)ALIGN((unsigned long)alignbuf, alignmask+1);
	int err = 0;

	crypto_ablkcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
	crypto_ablkcipher_set_flags(ctr, crypto_aead_get_flags(aead) &
				   CRYPTO_TFM_REQ_MASK);

	err = crypto_ablkcipher_setkey(ctr, key, keylen);
	if (err)
		goto out;

	crypto_aead_set_flags(aead, crypto_ablkcipher_get_flags(ctr) &
				       CRYPTO_TFM_RES_MASK);

	err = crypto_gcm_encrypt_counter(aead, hash, -1, NULL);
	if (err)
		goto out;

	if (ctx->gf128 != NULL)
		gf128mul_free_4k(ctx->gf128);

	ctx->gf128 = gf128mul_init_4k_lle((be128 *)hash);

	if (ctx->gf128 == NULL)
		err = -ENOMEM;

 out:
	return err;
}

static int crypto_gcm_init_crypt(struct ablkcipher_request *ablk_req,
				  struct aead_request *req,
				  void (*done)(struct crypto_async_request *,
					       int))
{
	struct crypto_aead *aead = crypto_aead_reqtfm(req);
	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u32 flags = req->base.tfm->crt_flags;
	u8 *auth_tag = pctx->auth_tag;
	u8 *counter = pctx->counter;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
	int err = 0;

	ablkcipher_request_set_tfm(ablk_req, ctx->ctr);
	ablkcipher_request_set_callback(ablk_req, aead_request_flags(req),
					done, req);
	ablkcipher_request_set_crypt(ablk_req, req->src, req->dst,
				     req->cryptlen, counter);

	err = crypto_gcm_encrypt_counter(aead, auth_tag, 0, req->iv);
	if (err)
		goto out;

	memcpy(counter, req->iv, 12);
	crypto_gcm_set_counter(counter, 1);

	crypto_gcm_ghash_init(ghash, flags, ctx->gf128);

	if (req->assoclen) {
		crypto_gcm_ghash_update_sg(ghash, req->assoc, req->assoclen);
		crypto_gcm_ghash_flush(ghash);
	}

 out:
	return err;
}

static void crypto_gcm_encrypt_done(struct crypto_async_request *areq, int err)
{
	struct aead_request *req = areq->data;
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u8 *auth_tag = pctx->auth_tag;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;

	crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
				   auth_tag);

	aead_request_complete(req, err);
}

static int crypto_gcm_encrypt(struct aead_request *req)
{
	struct ablkcipher_request abreq;
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u8 *auth_tag = pctx->auth_tag;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
	int err = 0;

	err = crypto_gcm_init_crypt(&abreq, req, crypto_gcm_encrypt_done);
	if (err)
		return err;

	if (req->cryptlen) {
		err = crypto_ablkcipher_encrypt(&abreq);
		if (err)
			return err;

		crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
	}

	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
				   auth_tag);

	return err;
}

static void crypto_gcm_decrypt_done(struct crypto_async_request *areq, int err)
{
	aead_request_complete(areq->data, err);
}

static int crypto_gcm_decrypt(struct aead_request *req)
{
	struct ablkcipher_request abreq;
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u8 *auth_tag = pctx->auth_tag;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
	u8 tag[16];
	int err;

	if (!req->cryptlen)
		return -EINVAL;

	memcpy(tag, auth_tag, 16);
	err = crypto_gcm_init_crypt(&abreq, req, crypto_gcm_decrypt_done);
	if (err)
		return err;

	crypto_gcm_ghash_update_sg(ghash, req->src, req->cryptlen);
	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
				   auth_tag);

	if (memcmp(tag, auth_tag, 16))
		return -EINVAL;

	return crypto_ablkcipher_decrypt(&abreq);
}

static int crypto_gcm_init_tfm(struct crypto_tfm *tfm)
{
	struct crypto_instance *inst = (void *)tfm->__crt_alg;
	struct gcm_instance_ctx *ictx = crypto_instance_ctx(inst);
	struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);
	struct crypto_ablkcipher *ctr;
	unsigned long align;
	int err;

	ctr = crypto_spawn_ablkcipher(&ictx->ctr);
	err = PTR_ERR(ctr);
	if (IS_ERR(ctr))
		return err;

	ctx->ctr = ctr;
	ctx->gf128 = NULL;

	align = max_t(unsigned long, crypto_ablkcipher_alignmask(ctr),
		      __alignof__(u32) - 1);
	align &= ~(crypto_tfm_ctx_alignment() - 1);
	tfm->crt_aead.reqsize = align + sizeof(struct crypto_gcm_req_priv_ctx);

	return 0;
}

static void crypto_gcm_exit_tfm(struct crypto_tfm *tfm)
{
	struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);

	if (ctx->gf128 != NULL)
		gf128mul_free_4k(ctx->gf128);

	crypto_free_ablkcipher(ctx->ctr);
}

static struct crypto_instance *crypto_gcm_alloc(struct rtattr **tb)
{
	struct crypto_instance *inst;
	struct crypto_alg *ctr;
	struct crypto_alg *cipher;
	struct gcm_instance_ctx *ctx;
	int err;
	char ctr_name[CRYPTO_MAX_ALG_NAME];

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD);
	if (err)
		return ERR_PTR(err);

	cipher = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
			      CRYPTO_ALG_TYPE_MASK);

	inst = ERR_PTR(PTR_ERR(cipher));
	if (IS_ERR(cipher))
		return inst;

	inst = ERR_PTR(ENAMETOOLONG);
	if (snprintf(
		    ctr_name, CRYPTO_MAX_ALG_NAME,
		    "ctr(%s,0,16,4)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME)
		return inst;

	ctr = crypto_alg_mod_lookup(ctr_name, CRYPTO_ALG_TYPE_BLKCIPHER,
				    CRYPTO_ALG_TYPE_MASK);

	if (IS_ERR(ctr))
		return ERR_PTR(PTR_ERR(ctr));

	if (cipher->cra_blocksize != 16)
		goto out_put_ctr;

	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
	err = -ENOMEM;
	if (!inst)
		goto out_put_ctr;

	err = -ENAMETOOLONG;
	if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
		     "gcm(%s)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME ||
	    snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
		     "gcm(%s)", cipher->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
		goto err_free_inst;


	ctx = crypto_instance_ctx(inst);
	err = crypto_init_spawn(&ctx->ctr, ctr, inst, CRYPTO_ALG_TYPE_MASK);
	if (err)
		goto err_free_inst;

	inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD | CRYPTO_ALG_ASYNC;
	inst->alg.cra_priority = ctr->cra_priority;
	inst->alg.cra_blocksize = 16;
	inst->alg.cra_alignmask = __alignof__(u32) - 1;
	inst->alg.cra_type = &crypto_aead_type;
	inst->alg.cra_aead.ivsize = 12;
	inst->alg.cra_aead.authsize = 16;
	inst->alg.cra_ctxsize = sizeof(struct crypto_gcm_ctx);
	inst->alg.cra_init = crypto_gcm_init_tfm;
	inst->alg.cra_exit = crypto_gcm_exit_tfm;
	inst->alg.cra_aead.setkey = crypto_gcm_setkey;
	inst->alg.cra_aead.encrypt = crypto_gcm_encrypt;
	inst->alg.cra_aead.decrypt = crypto_gcm_decrypt;

out:
	crypto_mod_put(ctr);
	return inst;
err_free_inst:
	kfree(inst);
out_put_ctr:
	inst = ERR_PTR(err);
	goto out;
}

static void crypto_gcm_free(struct crypto_instance *inst)
{
	struct gcm_instance_ctx *ctx = crypto_instance_ctx(inst);

	crypto_drop_spawn(&ctx->ctr);
	kfree(inst);
}

static struct crypto_template crypto_gcm_tmpl = {
	.name = "gcm",
	.alloc = crypto_gcm_alloc,
	.free = crypto_gcm_free,
	.module = THIS_MODULE,
};

static int __init crypto_gcm_module_init(void)
{
	return crypto_register_template(&crypto_gcm_tmpl);
}

static void __exit crypto_gcm_module_exit(void)
{
	crypto_unregister_template(&crypto_gcm_tmpl);
}

module_init(crypto_gcm_module_init);
module_exit(crypto_gcm_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Galois/Counter Mode");
MODULE_AUTHOR("Mikko Herranen <mh1@iki.fi>");