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 	[BLK_ENCRYPTION_MODE_SM4_XTS] = {
40 		.name = "SM4-XTS",
41 		.cipher_str = "xts(sm4)",
42 		.keysize = 32,
43 		.ivsize = 16,
44 	},
45 };
46 
47 /*
48  * This number needs to be at least (the number of threads doing IO
49  * concurrently) * (maximum recursive depth of a bio), so that we don't
50  * deadlock on crypt_ctx allocations. The default is chosen to be the same
51  * as the default number of post read contexts in both EXT4 and F2FS.
52  */
53 static int num_prealloc_crypt_ctxs = 128;
54 
55 module_param(num_prealloc_crypt_ctxs, int, 0444);
56 MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
57 		"Number of bio crypto contexts to preallocate");
58 
59 static struct kmem_cache *bio_crypt_ctx_cache;
60 static mempool_t *bio_crypt_ctx_pool;
61 
bio_crypt_ctx_init(void)62 static int __init bio_crypt_ctx_init(void)
63 {
64 	size_t i;
65 
66 	bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
67 	if (!bio_crypt_ctx_cache)
68 		goto out_no_mem;
69 
70 	bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
71 						      bio_crypt_ctx_cache);
72 	if (!bio_crypt_ctx_pool)
73 		goto out_no_mem;
74 
75 	/* This is assumed in various places. */
76 	BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
77 
78 	/* Sanity check that no algorithm exceeds the defined limits. */
79 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
80 		BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
81 		BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
82 	}
83 
84 	return 0;
85 out_no_mem:
86 	panic("Failed to allocate mem for bio crypt ctxs\n");
87 }
88 subsys_initcall(bio_crypt_ctx_init);
89 
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)90 void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
91 		       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
92 {
93 	struct bio_crypt_ctx *bc;
94 
95 	/*
96 	 * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
97 	 * that the mempool_alloc() can't fail.
98 	 */
99 	WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
100 
101 	bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
102 
103 	bc->bc_key = key;
104 	memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
105 
106 	bio->bi_crypt_context = bc;
107 }
108 
__bio_crypt_free_ctx(struct bio * bio)109 void __bio_crypt_free_ctx(struct bio *bio)
110 {
111 	mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
112 	bio->bi_crypt_context = NULL;
113 }
114 
__bio_crypt_clone(struct bio * dst,struct bio * src,gfp_t gfp_mask)115 int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
116 {
117 	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
118 	if (!dst->bi_crypt_context)
119 		return -ENOMEM;
120 	*dst->bi_crypt_context = *src->bi_crypt_context;
121 	return 0;
122 }
123 
124 /* Increments @dun by @inc, treating @dun as a multi-limb integer. */
bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],unsigned int inc)125 void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
126 			     unsigned int inc)
127 {
128 	int i;
129 
130 	for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
131 		dun[i] += inc;
132 		/*
133 		 * If the addition in this limb overflowed, then we need to
134 		 * carry 1 into the next limb. Else the carry is 0.
135 		 */
136 		if (dun[i] < inc)
137 			inc = 1;
138 		else
139 			inc = 0;
140 	}
141 }
142 
__bio_crypt_advance(struct bio * bio,unsigned int bytes)143 void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
144 {
145 	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
146 
147 	bio_crypt_dun_increment(bc->bc_dun,
148 				bytes >> bc->bc_key->data_unit_size_bits);
149 }
150 
151 /*
152  * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
153  * @next_dun, treating the DUNs as multi-limb integers.
154  */
bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx * bc,unsigned int bytes,const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])155 bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
156 				 unsigned int bytes,
157 				 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
158 {
159 	int i;
160 	unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
161 
162 	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
163 		if (bc->bc_dun[i] + carry != next_dun[i])
164 			return false;
165 		/*
166 		 * If the addition in this limb overflowed, then we need to
167 		 * carry 1 into the next limb. Else the carry is 0.
168 		 */
169 		if ((bc->bc_dun[i] + carry) < carry)
170 			carry = 1;
171 		else
172 			carry = 0;
173 	}
174 
175 	/* If the DUN wrapped through 0, don't treat it as contiguous. */
176 	return carry == 0;
177 }
178 
179 /*
180  * Checks that two bio crypt contexts are compatible - i.e. that
181  * they are mergeable except for data_unit_num continuity.
182  */
bio_crypt_ctx_compatible(struct bio_crypt_ctx * bc1,struct bio_crypt_ctx * bc2)183 static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
184 				     struct bio_crypt_ctx *bc2)
185 {
186 	if (!bc1)
187 		return !bc2;
188 
189 	return bc2 && bc1->bc_key == bc2->bc_key;
190 }
191 
bio_crypt_rq_ctx_compatible(struct request * rq,struct bio * bio)192 bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
193 {
194 	return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
195 }
196 
197 /*
198  * Checks that two bio crypt contexts are compatible, and also
199  * that their data_unit_nums are continuous (and can hence be merged)
200  * in the order @bc1 followed by @bc2.
201  */
bio_crypt_ctx_mergeable(struct bio_crypt_ctx * bc1,unsigned int bc1_bytes,struct bio_crypt_ctx * bc2)202 bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
203 			     struct bio_crypt_ctx *bc2)
204 {
205 	if (!bio_crypt_ctx_compatible(bc1, bc2))
206 		return false;
207 
208 	return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
209 }
210 
211 /* Check that all I/O segments are data unit aligned. */
bio_crypt_check_alignment(struct bio * bio)212 static bool bio_crypt_check_alignment(struct bio *bio)
213 {
214 	const unsigned int data_unit_size =
215 		bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
216 	struct bvec_iter iter;
217 	struct bio_vec bv;
218 
219 	bio_for_each_segment(bv, bio, iter) {
220 		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
221 			return false;
222 	}
223 
224 	return true;
225 }
226 
__blk_crypto_init_request(struct request * rq)227 blk_status_t __blk_crypto_init_request(struct request *rq)
228 {
229 	return blk_crypto_get_keyslot(rq->q->crypto_profile,
230 				      rq->crypt_ctx->bc_key,
231 				      &rq->crypt_keyslot);
232 }
233 
234 /**
235  * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
236  *
237  * @rq: The request whose crypto fields to uninitialize.
238  *
239  * Completely uninitializes the crypto fields of a request. If a keyslot has
240  * been programmed into some inline encryption hardware, that keyslot is
241  * released. The rq->crypt_ctx is also freed.
242  */
__blk_crypto_free_request(struct request * rq)243 void __blk_crypto_free_request(struct request *rq)
244 {
245 	blk_crypto_put_keyslot(rq->crypt_keyslot);
246 	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
247 	blk_crypto_rq_set_defaults(rq);
248 }
249 
250 /**
251  * __blk_crypto_bio_prep - Prepare bio for inline encryption
252  *
253  * @bio_ptr: pointer to original bio pointer
254  *
255  * If the bio crypt context provided for the bio is supported by the underlying
256  * device's inline encryption hardware, do nothing.
257  *
258  * Otherwise, try to perform en/decryption for this bio by falling back to the
259  * kernel crypto API. When the crypto API fallback is used for encryption,
260  * blk-crypto may choose to split the bio into 2 - the first one that will
261  * continue to be processed and the second one that will be resubmitted via
262  * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
263  * of the aforementioned "first one", and *bio_ptr will be updated to this
264  * bounce bio.
265  *
266  * Caller must ensure bio has bio_crypt_ctx.
267  *
268  * Return: true on success; false on error (and bio->bi_status will be set
269  *	   appropriately, and bio_endio() will have been called so bio
270  *	   submission should abort).
271  */
__blk_crypto_bio_prep(struct bio ** bio_ptr)272 bool __blk_crypto_bio_prep(struct bio **bio_ptr)
273 {
274 	struct bio *bio = *bio_ptr;
275 	const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
276 
277 	/* Error if bio has no data. */
278 	if (WARN_ON_ONCE(!bio_has_data(bio))) {
279 		bio->bi_status = BLK_STS_IOERR;
280 		goto fail;
281 	}
282 
283 	if (!bio_crypt_check_alignment(bio)) {
284 		bio->bi_status = BLK_STS_IOERR;
285 		goto fail;
286 	}
287 
288 	/*
289 	 * Success if device supports the encryption context, or if we succeeded
290 	 * in falling back to the crypto API.
291 	 */
292 	if (blk_crypto_config_supported_natively(bio->bi_bdev,
293 						 &bc_key->crypto_cfg))
294 		return true;
295 	if (blk_crypto_fallback_bio_prep(bio_ptr))
296 		return true;
297 fail:
298 	bio_endio(*bio_ptr);
299 	return false;
300 }
301 
__blk_crypto_rq_bio_prep(struct request * rq,struct bio * bio,gfp_t gfp_mask)302 int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
303 			     gfp_t gfp_mask)
304 {
305 	if (!rq->crypt_ctx) {
306 		rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
307 		if (!rq->crypt_ctx)
308 			return -ENOMEM;
309 	}
310 	*rq->crypt_ctx = *bio->bi_crypt_context;
311 	return 0;
312 }
313 
314 /**
315  * blk_crypto_init_key() - Prepare a key for use with blk-crypto
316  * @blk_key: Pointer to the blk_crypto_key to initialize.
317  * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
318  *	     @crypto_mode; see blk_crypto_modes[].
319  * @crypto_mode: identifier for the encryption algorithm to use
320  * @dun_bytes: number of bytes that will be used to specify the DUN when this
321  *	       key is used
322  * @data_unit_size: the data unit size to use for en/decryption
323  *
324  * Return: 0 on success, -errno on failure.  The caller is responsible for
325  *	   zeroizing both blk_key and raw_key when done with them.
326  */
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)327 int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
328 			enum blk_crypto_mode_num crypto_mode,
329 			unsigned int dun_bytes,
330 			unsigned int data_unit_size)
331 {
332 	const struct blk_crypto_mode *mode;
333 
334 	memset(blk_key, 0, sizeof(*blk_key));
335 
336 	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
337 		return -EINVAL;
338 
339 	mode = &blk_crypto_modes[crypto_mode];
340 	if (mode->keysize == 0)
341 		return -EINVAL;
342 
343 	if (dun_bytes == 0 || dun_bytes > mode->ivsize)
344 		return -EINVAL;
345 
346 	if (!is_power_of_2(data_unit_size))
347 		return -EINVAL;
348 
349 	blk_key->crypto_cfg.crypto_mode = crypto_mode;
350 	blk_key->crypto_cfg.dun_bytes = dun_bytes;
351 	blk_key->crypto_cfg.data_unit_size = data_unit_size;
352 	blk_key->data_unit_size_bits = ilog2(data_unit_size);
353 	blk_key->size = mode->keysize;
354 	memcpy(blk_key->raw, raw_key, mode->keysize);
355 
356 	return 0;
357 }
358 
blk_crypto_config_supported_natively(struct block_device * bdev,const struct blk_crypto_config * cfg)359 bool blk_crypto_config_supported_natively(struct block_device *bdev,
360 					  const struct blk_crypto_config *cfg)
361 {
362 	return __blk_crypto_cfg_supported(bdev_get_queue(bdev)->crypto_profile,
363 					  cfg);
364 }
365 
366 /*
367  * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
368  * block_device it's submitted to supports inline crypto, or the
369  * blk-crypto-fallback is enabled and supports the cfg).
370  */
blk_crypto_config_supported(struct block_device * bdev,const struct blk_crypto_config * cfg)371 bool blk_crypto_config_supported(struct block_device *bdev,
372 				 const struct blk_crypto_config *cfg)
373 {
374 	return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
375 	       blk_crypto_config_supported_natively(bdev, cfg);
376 }
377 
378 /**
379  * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
380  * @bdev: block device to operate on
381  * @key: A key to use on the device
382  *
383  * Upper layers must call this function to ensure that either the hardware
384  * supports the key's crypto settings, or the crypto API fallback has transforms
385  * for the needed mode allocated and ready to go. This function may allocate
386  * an skcipher, and *should not* be called from the data path, since that might
387  * cause a deadlock
388  *
389  * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
390  *	   blk-crypto-fallback is either disabled or the needed algorithm
391  *	   is disabled in the crypto API; or another -errno code.
392  */
blk_crypto_start_using_key(struct block_device * bdev,const struct blk_crypto_key * key)393 int blk_crypto_start_using_key(struct block_device *bdev,
394 			       const struct blk_crypto_key *key)
395 {
396 	if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
397 		return 0;
398 	return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
399 }
400 
401 /**
402  * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
403  *			    it may have been programmed into
404  * @bdev: The block_device who's associated inline encryption hardware this key
405  *     might have been programmed into
406  * @key: The key to evict
407  *
408  * Upper layers (filesystems) must call this function to ensure that a key is
409  * evicted from any hardware that it might have been programmed into.  The key
410  * must not be in use by any in-flight IO when this function is called.
411  *
412  * Return: 0 on success or if the key wasn't in any keyslot; -errno on error.
413  */
blk_crypto_evict_key(struct block_device * bdev,const struct blk_crypto_key * key)414 int blk_crypto_evict_key(struct block_device *bdev,
415 			 const struct blk_crypto_key *key)
416 {
417 	struct request_queue *q = bdev_get_queue(bdev);
418 
419 	if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
420 		return __blk_crypto_evict_key(q->crypto_profile, key);
421 
422 	/*
423 	 * If the block_device didn't support the key, then blk-crypto-fallback
424 	 * may have been used, so try to evict the key from blk-crypto-fallback.
425 	 */
426 	return blk_crypto_fallback_evict_key(key);
427 }
428 EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
429