summaryrefslogtreecommitdiff
path: root/block/blk-crypto.c
blob: 25b981257f5fa823bbcebb5c1d6d069d79be10b4 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2019 Google LLC
 */

/*
 * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
 */

#define pr_fmt(fmt) "blk-crypto: " fmt

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/keyslot-manager.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "blk-crypto-internal.h"

const struct blk_crypto_mode blk_crypto_modes[] = {
	[BLK_ENCRYPTION_MODE_AES_256_XTS] = {
		.keysize = 64,
		.ivsize = 16,
	},
	[BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
		.keysize = 16,
		.ivsize = 16,
	},
	[BLK_ENCRYPTION_MODE_ADIANTUM] = {
		.keysize = 32,
		.ivsize = 32,
	},
};

/*
 * This number needs to be at least (the number of threads doing IO
 * concurrently) * (maximum recursive depth of a bio), so that we don't
 * deadlock on crypt_ctx allocations. The default is chosen to be the same
 * as the default number of post read contexts in both EXT4 and F2FS.
 */
static int num_prealloc_crypt_ctxs = 128;

module_param(num_prealloc_crypt_ctxs, int, 0444);
MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
		"Number of bio crypto contexts to preallocate");

static struct kmem_cache *bio_crypt_ctx_cache;
static mempool_t *bio_crypt_ctx_pool;

static int __init bio_crypt_ctx_init(void)
{
	size_t i;

	bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
	if (!bio_crypt_ctx_cache)
		goto out_no_mem;

	bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
						      bio_crypt_ctx_cache);
	if (!bio_crypt_ctx_pool)
		goto out_no_mem;

	/* This is assumed in various places. */
	BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);

	/* Sanity check that no algorithm exceeds the defined limits. */
	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
		BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
		BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
	}

	return 0;
out_no_mem:
	panic("Failed to allocate mem for bio crypt ctxs\n");
}
subsys_initcall(bio_crypt_ctx_init);

void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
		       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
{
	struct bio_crypt_ctx *bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);

	bc->bc_key = key;
	memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));

	bio->bi_crypt_context = bc;
}

void __bio_crypt_free_ctx(struct bio *bio)
{
	mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
	bio->bi_crypt_context = NULL;
}

void __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
{
	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
	*dst->bi_crypt_context = *src->bi_crypt_context;
}
EXPORT_SYMBOL_GPL(__bio_crypt_clone);

/* Increments @dun by @inc, treating @dun as a multi-limb integer. */
void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
			     unsigned int inc)
{
	int i;

	for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
		dun[i] += inc;
		/*
		 * If the addition in this limb overflowed, then we need to
		 * carry 1 into the next limb. Else the carry is 0.
		 */
		if (dun[i] < inc)
			inc = 1;
		else
			inc = 0;
	}
}

void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
{
	struct bio_crypt_ctx *bc = bio->bi_crypt_context;

	bio_crypt_dun_increment(bc->bc_dun,
				bytes >> bc->bc_key->data_unit_size_bits);
}

/*
 * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
 * @next_dun, treating the DUNs as multi-limb integers.
 */
bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
				 unsigned int bytes,
				 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
{
	int i;
	unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;

	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
		if (bc->bc_dun[i] + carry != next_dun[i])
			return false;
		/*
		 * If the addition in this limb overflowed, then we need to
		 * carry 1 into the next limb. Else the carry is 0.
		 */
		if ((bc->bc_dun[i] + carry) < carry)
			carry = 1;
		else
			carry = 0;
	}

	/* If the DUN wrapped through 0, don't treat it as contiguous. */
	return carry == 0;
}

/*
 * Checks that two bio crypt contexts are compatible - i.e. that
 * they are mergeable except for data_unit_num continuity.
 */
static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
				     struct bio_crypt_ctx *bc2)
{
	if (!bc1)
		return !bc2;

	return bc2 && bc1->bc_key == bc2->bc_key;
}

bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
{
	return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
}

/*
 * Checks that two bio crypt contexts are compatible, and also
 * that their data_unit_nums are continuous (and can hence be merged)
 * in the order @bc1 followed by @bc2.
 */
bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
			     struct bio_crypt_ctx *bc2)
{
	if (!bio_crypt_ctx_compatible(bc1, bc2))
		return false;

	return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
}

/* Check that all I/O segments are data unit aligned. */
static bool bio_crypt_check_alignment(struct bio *bio)
{
	const unsigned int data_unit_size =
		bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
	struct bvec_iter iter;
	struct bio_vec bv;

	bio_for_each_segment(bv, bio, iter) {
		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
			return false;
	}

	return true;
}

blk_status_t __blk_crypto_init_request(struct request *rq)
{
	return blk_ksm_get_slot_for_key(rq->q->ksm, rq->crypt_ctx->bc_key,
					&rq->crypt_keyslot);
}

/**
 * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
 *
 * @rq: The request whose crypto fields to uninitialize.
 *
 * Completely uninitializes the crypto fields of a request. If a keyslot has
 * been programmed into some inline encryption hardware, that keyslot is
 * released. The rq->crypt_ctx is also freed.
 */
void __blk_crypto_free_request(struct request *rq)
{
	blk_ksm_put_slot(rq->crypt_keyslot);
	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
	blk_crypto_rq_set_defaults(rq);
}

/**
 * __blk_crypto_bio_prep - Prepare bio for inline encryption
 *
 * @bio_ptr: pointer to original bio pointer
 *
 * Succeeds if the bio doesn't have inline encryption enabled or if the bio
 * crypt context provided for the bio is supported by the underlying device's
 * inline encryption hardware. Ends the bio with error otherwise.
 *
 * Caller must ensure bio has bio_crypt_ctx.
 *
 * Return: true on success; false on error (and bio->bi_status will be set
 *	   appropriately, and bio_endio() will have been called so bio
 *	   submission should abort).
 */
bool __blk_crypto_bio_prep(struct bio **bio_ptr)
{
	struct bio *bio = *bio_ptr;
	const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
	blk_status_t blk_st = BLK_STS_IOERR;

	/* Error if bio has no data. */
	if (WARN_ON_ONCE(!bio_has_data(bio)))
		goto fail;

	if (!bio_crypt_check_alignment(bio))
		goto fail;

	/*
	 * Success if device supports the encryption context.
	 */
	if (!blk_ksm_crypto_cfg_supported(bio->bi_disk->queue->ksm,
					  &bc_key->crypto_cfg)) {
		blk_st = BLK_STS_NOTSUPP;
		goto fail;
	}

	return true;
fail:
	(*bio_ptr)->bi_status = blk_st;
	bio_endio(*bio_ptr);
	return false;
}

/**
 * __blk_crypto_rq_bio_prep - Prepare a request's crypt_ctx when its first bio
 *			      is inserted
 *
 * @rq: The request to prepare
 * @bio: The first bio being inserted into the request
 * @gfp_mask: gfp mask
 */
void __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
			      gfp_t gfp_mask)
{
	if (!rq->crypt_ctx)
		rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
	*rq->crypt_ctx = *bio->bi_crypt_context;
}

/**
 * blk_crypto_init_key() - Prepare a key for use with blk-crypto
 * @blk_key: Pointer to the blk_crypto_key to initialize.
 * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
 *	     @crypto_mode; see blk_crypto_modes[].
 * @crypto_mode: identifier for the encryption algorithm to use
 * @dun_bytes: number of bytes that will be used to specify the DUN when this
 *	       key is used
 * @data_unit_size: the data unit size to use for en/decryption
 *
 * Return: 0 on success, -errno on failure.  The caller is responsible for
 *	   zeroizing both blk_key and raw_key when done with them.
 */
int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
			enum blk_crypto_mode_num crypto_mode,
			unsigned int dun_bytes,
			unsigned int data_unit_size)
{
	const struct blk_crypto_mode *mode;

	memset(blk_key, 0, sizeof(*blk_key));

	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
		return -EINVAL;

	mode = &blk_crypto_modes[crypto_mode];
	if (mode->keysize == 0)
		return -EINVAL;

	if (dun_bytes == 0 || dun_bytes > BLK_CRYPTO_MAX_IV_SIZE)
		return -EINVAL;

	if (!is_power_of_2(data_unit_size))
		return -EINVAL;

	blk_key->crypto_cfg.crypto_mode = crypto_mode;
	blk_key->crypto_cfg.dun_bytes = dun_bytes;
	blk_key->crypto_cfg.data_unit_size = data_unit_size;
	blk_key->data_unit_size_bits = ilog2(data_unit_size);
	blk_key->size = mode->keysize;
	memcpy(blk_key->raw, raw_key, mode->keysize);

	return 0;
}

bool blk_crypto_config_supported(struct request_queue *q,
				 const struct blk_crypto_config *cfg)
{
	return blk_ksm_crypto_cfg_supported(q->ksm, cfg);
}

/**
 * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
 * @key: A key to use on the device
 * @q: the request queue for the device
 *
 * Upper layers must call this function to ensure that the hardware supports
 * the key's crypto settings.
 *
 * Return: 0 on success; -ENOPKG if the hardware doesn't support the key
 */
int blk_crypto_start_using_key(const struct blk_crypto_key *key,
			       struct request_queue *q)
{
	if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
		return 0;
	return -ENOPKG;
}

/**
 * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
 *			    it may have been programmed into
 * @q: The request queue who's associated inline encryption hardware this key
 *     might have been programmed into
 * @key: The key to evict
 *
 * Upper layers (filesystems) must call this function to ensure that a key is
 * evicted from any hardware that it might have been programmed into.  The key
 * must not be in use by any in-flight IO when this function is called.
 *
 * Return: 0 on success or if key is not present in the q's ksm, -err on error.
 */
int blk_crypto_evict_key(struct request_queue *q,
			 const struct blk_crypto_key *key)
{
	if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
		return blk_ksm_evict_key(q->ksm, key);

	return 0;
}