xref: /openbmc/linux/block/blk-crypto.c (revision 9b656879)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright 2019 Google LLC
4  */
5 
6 /*
7  * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
8  */
9 
10 #define pr_fmt(fmt) "blk-crypto: " fmt
11 
12 #include <linux/bio.h>
13 #include <linux/blkdev.h>
14 #include <linux/blk-crypto-profile.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 
18 #include "blk-crypto-internal.h"
19 
20 const struct blk_crypto_mode blk_crypto_modes[] = {
21 	[BLK_ENCRYPTION_MODE_AES_256_XTS] = {
22 		.name = "AES-256-XTS",
23 		.cipher_str = "xts(aes)",
24 		.keysize = 64,
25 		.ivsize = 16,
26 	},
27 	[BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
28 		.name = "AES-128-CBC-ESSIV",
29 		.cipher_str = "essiv(cbc(aes),sha256)",
30 		.keysize = 16,
31 		.ivsize = 16,
32 	},
33 	[BLK_ENCRYPTION_MODE_ADIANTUM] = {
34 		.name = "Adiantum",
35 		.cipher_str = "adiantum(xchacha12,aes)",
36 		.keysize = 32,
37 		.ivsize = 32,
38 	},
39 };
40 
41 /*
42  * This number needs to be at least (the number of threads doing IO
43  * concurrently) * (maximum recursive depth of a bio), so that we don't
44  * deadlock on crypt_ctx allocations. The default is chosen to be the same
45  * as the default number of post read contexts in both EXT4 and F2FS.
46  */
47 static int num_prealloc_crypt_ctxs = 128;
48 
49 module_param(num_prealloc_crypt_ctxs, int, 0444);
50 MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
51 		"Number of bio crypto contexts to preallocate");
52 
53 static struct kmem_cache *bio_crypt_ctx_cache;
54 static mempool_t *bio_crypt_ctx_pool;
55 
56 static int __init bio_crypt_ctx_init(void)
57 {
58 	size_t i;
59 
60 	bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
61 	if (!bio_crypt_ctx_cache)
62 		goto out_no_mem;
63 
64 	bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
65 						      bio_crypt_ctx_cache);
66 	if (!bio_crypt_ctx_pool)
67 		goto out_no_mem;
68 
69 	/* This is assumed in various places. */
70 	BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
71 
72 	/* Sanity check that no algorithm exceeds the defined limits. */
73 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
74 		BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
75 		BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
76 	}
77 
78 	return 0;
79 out_no_mem:
80 	panic("Failed to allocate mem for bio crypt ctxs\n");
81 }
82 subsys_initcall(bio_crypt_ctx_init);
83 
84 void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
85 		       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
86 {
87 	struct bio_crypt_ctx *bc;
88 
89 	/*
90 	 * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
91 	 * that the mempool_alloc() can't fail.
92 	 */
93 	WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
94 
95 	bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
96 
97 	bc->bc_key = key;
98 	memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
99 
100 	bio->bi_crypt_context = bc;
101 }
102 
103 void __bio_crypt_free_ctx(struct bio *bio)
104 {
105 	mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
106 	bio->bi_crypt_context = NULL;
107 }
108 
109 int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
110 {
111 	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
112 	if (!dst->bi_crypt_context)
113 		return -ENOMEM;
114 	*dst->bi_crypt_context = *src->bi_crypt_context;
115 	return 0;
116 }
117 
118 /* Increments @dun by @inc, treating @dun as a multi-limb integer. */
119 void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
120 			     unsigned int inc)
121 {
122 	int i;
123 
124 	for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
125 		dun[i] += inc;
126 		/*
127 		 * If the addition in this limb overflowed, then we need to
128 		 * carry 1 into the next limb. Else the carry is 0.
129 		 */
130 		if (dun[i] < inc)
131 			inc = 1;
132 		else
133 			inc = 0;
134 	}
135 }
136 
137 void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
138 {
139 	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
140 
141 	bio_crypt_dun_increment(bc->bc_dun,
142 				bytes >> bc->bc_key->data_unit_size_bits);
143 }
144 
145 /*
146  * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
147  * @next_dun, treating the DUNs as multi-limb integers.
148  */
149 bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
150 				 unsigned int bytes,
151 				 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
152 {
153 	int i;
154 	unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
155 
156 	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
157 		if (bc->bc_dun[i] + carry != next_dun[i])
158 			return false;
159 		/*
160 		 * If the addition in this limb overflowed, then we need to
161 		 * carry 1 into the next limb. Else the carry is 0.
162 		 */
163 		if ((bc->bc_dun[i] + carry) < carry)
164 			carry = 1;
165 		else
166 			carry = 0;
167 	}
168 
169 	/* If the DUN wrapped through 0, don't treat it as contiguous. */
170 	return carry == 0;
171 }
172 
173 /*
174  * Checks that two bio crypt contexts are compatible - i.e. that
175  * they are mergeable except for data_unit_num continuity.
176  */
177 static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
178 				     struct bio_crypt_ctx *bc2)
179 {
180 	if (!bc1)
181 		return !bc2;
182 
183 	return bc2 && bc1->bc_key == bc2->bc_key;
184 }
185 
186 bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
187 {
188 	return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
189 }
190 
191 /*
192  * Checks that two bio crypt contexts are compatible, and also
193  * that their data_unit_nums are continuous (and can hence be merged)
194  * in the order @bc1 followed by @bc2.
195  */
196 bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
197 			     struct bio_crypt_ctx *bc2)
198 {
199 	if (!bio_crypt_ctx_compatible(bc1, bc2))
200 		return false;
201 
202 	return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
203 }
204 
205 /* Check that all I/O segments are data unit aligned. */
206 static bool bio_crypt_check_alignment(struct bio *bio)
207 {
208 	const unsigned int data_unit_size =
209 		bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
210 	struct bvec_iter iter;
211 	struct bio_vec bv;
212 
213 	bio_for_each_segment(bv, bio, iter) {
214 		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
215 			return false;
216 	}
217 
218 	return true;
219 }
220 
221 blk_status_t __blk_crypto_init_request(struct request *rq)
222 {
223 	return blk_crypto_get_keyslot(rq->q->crypto_profile,
224 				      rq->crypt_ctx->bc_key,
225 				      &rq->crypt_keyslot);
226 }
227 
228 /**
229  * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
230  *
231  * @rq: The request whose crypto fields to uninitialize.
232  *
233  * Completely uninitializes the crypto fields of a request. If a keyslot has
234  * been programmed into some inline encryption hardware, that keyslot is
235  * released. The rq->crypt_ctx is also freed.
236  */
237 void __blk_crypto_free_request(struct request *rq)
238 {
239 	blk_crypto_put_keyslot(rq->crypt_keyslot);
240 	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
241 	blk_crypto_rq_set_defaults(rq);
242 }
243 
244 /**
245  * __blk_crypto_bio_prep - Prepare bio for inline encryption
246  *
247  * @bio_ptr: pointer to original bio pointer
248  *
249  * If the bio crypt context provided for the bio is supported by the underlying
250  * device's inline encryption hardware, do nothing.
251  *
252  * Otherwise, try to perform en/decryption for this bio by falling back to the
253  * kernel crypto API. When the crypto API fallback is used for encryption,
254  * blk-crypto may choose to split the bio into 2 - the first one that will
255  * continue to be processed and the second one that will be resubmitted via
256  * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
257  * of the aforementioned "first one", and *bio_ptr will be updated to this
258  * bounce bio.
259  *
260  * Caller must ensure bio has bio_crypt_ctx.
261  *
262  * Return: true on success; false on error (and bio->bi_status will be set
263  *	   appropriately, and bio_endio() will have been called so bio
264  *	   submission should abort).
265  */
266 bool __blk_crypto_bio_prep(struct bio **bio_ptr)
267 {
268 	struct bio *bio = *bio_ptr;
269 	const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
270 	struct blk_crypto_profile *profile;
271 
272 	/* Error if bio has no data. */
273 	if (WARN_ON_ONCE(!bio_has_data(bio))) {
274 		bio->bi_status = BLK_STS_IOERR;
275 		goto fail;
276 	}
277 
278 	if (!bio_crypt_check_alignment(bio)) {
279 		bio->bi_status = BLK_STS_IOERR;
280 		goto fail;
281 	}
282 
283 	/*
284 	 * Success if device supports the encryption context, or if we succeeded
285 	 * in falling back to the crypto API.
286 	 */
287 	profile = bdev_get_queue(bio->bi_bdev)->crypto_profile;
288 	if (__blk_crypto_cfg_supported(profile, &bc_key->crypto_cfg))
289 		return true;
290 
291 	if (blk_crypto_fallback_bio_prep(bio_ptr))
292 		return true;
293 fail:
294 	bio_endio(*bio_ptr);
295 	return false;
296 }
297 
298 int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
299 			     gfp_t gfp_mask)
300 {
301 	if (!rq->crypt_ctx) {
302 		rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
303 		if (!rq->crypt_ctx)
304 			return -ENOMEM;
305 	}
306 	*rq->crypt_ctx = *bio->bi_crypt_context;
307 	return 0;
308 }
309 
310 /**
311  * blk_crypto_init_key() - Prepare a key for use with blk-crypto
312  * @blk_key: Pointer to the blk_crypto_key to initialize.
313  * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
314  *	     @crypto_mode; see blk_crypto_modes[].
315  * @crypto_mode: identifier for the encryption algorithm to use
316  * @dun_bytes: number of bytes that will be used to specify the DUN when this
317  *	       key is used
318  * @data_unit_size: the data unit size to use for en/decryption
319  *
320  * Return: 0 on success, -errno on failure.  The caller is responsible for
321  *	   zeroizing both blk_key and raw_key when done with them.
322  */
323 int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
324 			enum blk_crypto_mode_num crypto_mode,
325 			unsigned int dun_bytes,
326 			unsigned int data_unit_size)
327 {
328 	const struct blk_crypto_mode *mode;
329 
330 	memset(blk_key, 0, sizeof(*blk_key));
331 
332 	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
333 		return -EINVAL;
334 
335 	mode = &blk_crypto_modes[crypto_mode];
336 	if (mode->keysize == 0)
337 		return -EINVAL;
338 
339 	if (dun_bytes == 0 || dun_bytes > mode->ivsize)
340 		return -EINVAL;
341 
342 	if (!is_power_of_2(data_unit_size))
343 		return -EINVAL;
344 
345 	blk_key->crypto_cfg.crypto_mode = crypto_mode;
346 	blk_key->crypto_cfg.dun_bytes = dun_bytes;
347 	blk_key->crypto_cfg.data_unit_size = data_unit_size;
348 	blk_key->data_unit_size_bits = ilog2(data_unit_size);
349 	blk_key->size = mode->keysize;
350 	memcpy(blk_key->raw, raw_key, mode->keysize);
351 
352 	return 0;
353 }
354 
355 /*
356  * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
357  * request queue it's submitted to supports inline crypto, or the
358  * blk-crypto-fallback is enabled and supports the cfg).
359  */
360 bool blk_crypto_config_supported(struct request_queue *q,
361 				 const struct blk_crypto_config *cfg)
362 {
363 	return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
364 	       __blk_crypto_cfg_supported(q->crypto_profile, cfg);
365 }
366 
367 /**
368  * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
369  * @key: A key to use on the device
370  * @q: the request queue for the device
371  *
372  * Upper layers must call this function to ensure that either the hardware
373  * supports the key's crypto settings, or the crypto API fallback has transforms
374  * for the needed mode allocated and ready to go. This function may allocate
375  * an skcipher, and *should not* be called from the data path, since that might
376  * cause a deadlock
377  *
378  * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
379  *	   blk-crypto-fallback is either disabled or the needed algorithm
380  *	   is disabled in the crypto API; or another -errno code.
381  */
382 int blk_crypto_start_using_key(const struct blk_crypto_key *key,
383 			       struct request_queue *q)
384 {
385 	if (__blk_crypto_cfg_supported(q->crypto_profile, &key->crypto_cfg))
386 		return 0;
387 	return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
388 }
389 
390 /**
391  * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
392  *			    it may have been programmed into
393  * @q: The request queue who's associated inline encryption hardware this key
394  *     might have been programmed into
395  * @key: The key to evict
396  *
397  * Upper layers (filesystems) must call this function to ensure that a key is
398  * evicted from any hardware that it might have been programmed into.  The key
399  * must not be in use by any in-flight IO when this function is called.
400  *
401  * Return: 0 on success or if the key wasn't in any keyslot; -errno on error.
402  */
403 int blk_crypto_evict_key(struct request_queue *q,
404 			 const struct blk_crypto_key *key)
405 {
406 	if (__blk_crypto_cfg_supported(q->crypto_profile, &key->crypto_cfg))
407 		return __blk_crypto_evict_key(q->crypto_profile, key);
408 
409 	/*
410 	 * If the request_queue didn't support the key, then blk-crypto-fallback
411 	 * may have been used, so try to evict the key from blk-crypto-fallback.
412 	 */
413 	return blk_crypto_fallback_evict_key(key);
414 }
415 EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
416