xref: /openbmc/linux/block/blk-crypto.c (revision 5c7cb944)
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/ratelimit.h>
17 #include <linux/slab.h>
18 
19 #include "blk-crypto-internal.h"
20 
21 const struct blk_crypto_mode blk_crypto_modes[] = {
22 	[BLK_ENCRYPTION_MODE_AES_256_XTS] = {
23 		.name = "AES-256-XTS",
24 		.cipher_str = "xts(aes)",
25 		.keysize = 64,
26 		.ivsize = 16,
27 	},
28 	[BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
29 		.name = "AES-128-CBC-ESSIV",
30 		.cipher_str = "essiv(cbc(aes),sha256)",
31 		.keysize = 16,
32 		.ivsize = 16,
33 	},
34 	[BLK_ENCRYPTION_MODE_ADIANTUM] = {
35 		.name = "Adiantum",
36 		.cipher_str = "adiantum(xchacha12,aes)",
37 		.keysize = 32,
38 		.ivsize = 32,
39 	},
40 	[BLK_ENCRYPTION_MODE_SM4_XTS] = {
41 		.name = "SM4-XTS",
42 		.cipher_str = "xts(sm4)",
43 		.keysize = 32,
44 		.ivsize = 16,
45 	},
46 };
47 
48 /*
49  * This number needs to be at least (the number of threads doing IO
50  * concurrently) * (maximum recursive depth of a bio), so that we don't
51  * deadlock on crypt_ctx allocations. The default is chosen to be the same
52  * as the default number of post read contexts in both EXT4 and F2FS.
53  */
54 static int num_prealloc_crypt_ctxs = 128;
55 
56 module_param(num_prealloc_crypt_ctxs, int, 0444);
57 MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
58 		"Number of bio crypto contexts to preallocate");
59 
60 static struct kmem_cache *bio_crypt_ctx_cache;
61 static mempool_t *bio_crypt_ctx_pool;
62 
bio_crypt_ctx_init(void)63 static int __init bio_crypt_ctx_init(void)
64 {
65 	size_t i;
66 
67 	bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
68 	if (!bio_crypt_ctx_cache)
69 		goto out_no_mem;
70 
71 	bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
72 						      bio_crypt_ctx_cache);
73 	if (!bio_crypt_ctx_pool)
74 		goto out_no_mem;
75 
76 	/* This is assumed in various places. */
77 	BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
78 
79 	/* Sanity check that no algorithm exceeds the defined limits. */
80 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
81 		BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
82 		BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
83 	}
84 
85 	return 0;
86 out_no_mem:
87 	panic("Failed to allocate mem for bio crypt ctxs\n");
88 }
89 subsys_initcall(bio_crypt_ctx_init);
90 
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)91 void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
92 		       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
93 {
94 	struct bio_crypt_ctx *bc;
95 
96 	/*
97 	 * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
98 	 * that the mempool_alloc() can't fail.
99 	 */
100 	WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
101 
102 	bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
103 
104 	bc->bc_key = key;
105 	memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
106 
107 	bio->bi_crypt_context = bc;
108 }
109 
__bio_crypt_free_ctx(struct bio * bio)110 void __bio_crypt_free_ctx(struct bio *bio)
111 {
112 	mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
113 	bio->bi_crypt_context = NULL;
114 }
115 
__bio_crypt_clone(struct bio * dst,struct bio * src,gfp_t gfp_mask)116 int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
117 {
118 	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
119 	if (!dst->bi_crypt_context)
120 		return -ENOMEM;
121 	*dst->bi_crypt_context = *src->bi_crypt_context;
122 	return 0;
123 }
124 
125 /* 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)126 void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
127 			     unsigned int inc)
128 {
129 	int i;
130 
131 	for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
132 		dun[i] += inc;
133 		/*
134 		 * If the addition in this limb overflowed, then we need to
135 		 * carry 1 into the next limb. Else the carry is 0.
136 		 */
137 		if (dun[i] < inc)
138 			inc = 1;
139 		else
140 			inc = 0;
141 	}
142 }
143 
__bio_crypt_advance(struct bio * bio,unsigned int bytes)144 void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
145 {
146 	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
147 
148 	bio_crypt_dun_increment(bc->bc_dun,
149 				bytes >> bc->bc_key->data_unit_size_bits);
150 }
151 
152 /*
153  * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
154  * @next_dun, treating the DUNs as multi-limb integers.
155  */
bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx * bc,unsigned int bytes,const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])156 bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
157 				 unsigned int bytes,
158 				 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
159 {
160 	int i;
161 	unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
162 
163 	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
164 		if (bc->bc_dun[i] + carry != next_dun[i])
165 			return false;
166 		/*
167 		 * If the addition in this limb overflowed, then we need to
168 		 * carry 1 into the next limb. Else the carry is 0.
169 		 */
170 		if ((bc->bc_dun[i] + carry) < carry)
171 			carry = 1;
172 		else
173 			carry = 0;
174 	}
175 
176 	/* If the DUN wrapped through 0, don't treat it as contiguous. */
177 	return carry == 0;
178 }
179 
180 /*
181  * Checks that two bio crypt contexts are compatible - i.e. that
182  * they are mergeable except for data_unit_num continuity.
183  */
bio_crypt_ctx_compatible(struct bio_crypt_ctx * bc1,struct bio_crypt_ctx * bc2)184 static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
185 				     struct bio_crypt_ctx *bc2)
186 {
187 	if (!bc1)
188 		return !bc2;
189 
190 	return bc2 && bc1->bc_key == bc2->bc_key;
191 }
192 
bio_crypt_rq_ctx_compatible(struct request * rq,struct bio * bio)193 bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
194 {
195 	return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
196 }
197 
198 /*
199  * Checks that two bio crypt contexts are compatible, and also
200  * that their data_unit_nums are continuous (and can hence be merged)
201  * in the order @bc1 followed by @bc2.
202  */
bio_crypt_ctx_mergeable(struct bio_crypt_ctx * bc1,unsigned int bc1_bytes,struct bio_crypt_ctx * bc2)203 bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
204 			     struct bio_crypt_ctx *bc2)
205 {
206 	if (!bio_crypt_ctx_compatible(bc1, bc2))
207 		return false;
208 
209 	return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
210 }
211 
212 /* Check that all I/O segments are data unit aligned. */
bio_crypt_check_alignment(struct bio * bio)213 static bool bio_crypt_check_alignment(struct bio *bio)
214 {
215 	const unsigned int data_unit_size =
216 		bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
217 	struct bvec_iter iter;
218 	struct bio_vec bv;
219 
220 	bio_for_each_segment(bv, bio, iter) {
221 		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
222 			return false;
223 	}
224 
225 	return true;
226 }
227 
__blk_crypto_rq_get_keyslot(struct request * rq)228 blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq)
229 {
230 	return blk_crypto_get_keyslot(rq->q->crypto_profile,
231 				      rq->crypt_ctx->bc_key,
232 				      &rq->crypt_keyslot);
233 }
234 
__blk_crypto_rq_put_keyslot(struct request * rq)235 void __blk_crypto_rq_put_keyslot(struct request *rq)
236 {
237 	blk_crypto_put_keyslot(rq->crypt_keyslot);
238 	rq->crypt_keyslot = NULL;
239 }
240 
__blk_crypto_free_request(struct request * rq)241 void __blk_crypto_free_request(struct request *rq)
242 {
243 	/* The keyslot, if one was needed, should have been released earlier. */
244 	if (WARN_ON_ONCE(rq->crypt_keyslot))
245 		__blk_crypto_rq_put_keyslot(rq);
246 
247 	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
248 	rq->crypt_ctx = NULL;
249 }
250 
251 /**
252  * __blk_crypto_bio_prep - Prepare bio for inline encryption
253  *
254  * @bio_ptr: pointer to original bio pointer
255  *
256  * If the bio crypt context provided for the bio is supported by the underlying
257  * device's inline encryption hardware, do nothing.
258  *
259  * Otherwise, try to perform en/decryption for this bio by falling back to the
260  * kernel crypto API. When the crypto API fallback is used for encryption,
261  * blk-crypto may choose to split the bio into 2 - the first one that will
262  * continue to be processed and the second one that will be resubmitted via
263  * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
264  * of the aforementioned "first one", and *bio_ptr will be updated to this
265  * bounce bio.
266  *
267  * Caller must ensure bio has bio_crypt_ctx.
268  *
269  * Return: true on success; false on error (and bio->bi_status will be set
270  *	   appropriately, and bio_endio() will have been called so bio
271  *	   submission should abort).
272  */
__blk_crypto_bio_prep(struct bio ** bio_ptr)273 bool __blk_crypto_bio_prep(struct bio **bio_ptr)
274 {
275 	struct bio *bio = *bio_ptr;
276 	const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
277 
278 	/* Error if bio has no data. */
279 	if (WARN_ON_ONCE(!bio_has_data(bio))) {
280 		bio->bi_status = BLK_STS_IOERR;
281 		goto fail;
282 	}
283 
284 	if (!bio_crypt_check_alignment(bio)) {
285 		bio->bi_status = BLK_STS_IOERR;
286 		goto fail;
287 	}
288 
289 	/*
290 	 * Success if device supports the encryption context, or if we succeeded
291 	 * in falling back to the crypto API.
292 	 */
293 	if (blk_crypto_config_supported_natively(bio->bi_bdev,
294 						 &bc_key->crypto_cfg))
295 		return true;
296 	if (blk_crypto_fallback_bio_prep(bio_ptr))
297 		return true;
298 fail:
299 	bio_endio(*bio_ptr);
300 	return false;
301 }
302 
__blk_crypto_rq_bio_prep(struct request * rq,struct bio * bio,gfp_t gfp_mask)303 int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
304 			     gfp_t gfp_mask)
305 {
306 	if (!rq->crypt_ctx) {
307 		rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
308 		if (!rq->crypt_ctx)
309 			return -ENOMEM;
310 	}
311 	*rq->crypt_ctx = *bio->bi_crypt_context;
312 	return 0;
313 }
314 
315 /**
316  * blk_crypto_init_key() - Prepare a key for use with blk-crypto
317  * @blk_key: Pointer to the blk_crypto_key to initialize.
318  * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
319  *	     @crypto_mode; see blk_crypto_modes[].
320  * @crypto_mode: identifier for the encryption algorithm to use
321  * @dun_bytes: number of bytes that will be used to specify the DUN when this
322  *	       key is used
323  * @data_unit_size: the data unit size to use for en/decryption
324  *
325  * Return: 0 on success, -errno on failure.  The caller is responsible for
326  *	   zeroizing both blk_key and raw_key when done with them.
327  */
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)328 int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
329 			enum blk_crypto_mode_num crypto_mode,
330 			unsigned int dun_bytes,
331 			unsigned int data_unit_size)
332 {
333 	const struct blk_crypto_mode *mode;
334 
335 	memset(blk_key, 0, sizeof(*blk_key));
336 
337 	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
338 		return -EINVAL;
339 
340 	mode = &blk_crypto_modes[crypto_mode];
341 	if (mode->keysize == 0)
342 		return -EINVAL;
343 
344 	if (dun_bytes == 0 || dun_bytes > mode->ivsize)
345 		return -EINVAL;
346 
347 	if (!is_power_of_2(data_unit_size))
348 		return -EINVAL;
349 
350 	blk_key->crypto_cfg.crypto_mode = crypto_mode;
351 	blk_key->crypto_cfg.dun_bytes = dun_bytes;
352 	blk_key->crypto_cfg.data_unit_size = data_unit_size;
353 	blk_key->data_unit_size_bits = ilog2(data_unit_size);
354 	blk_key->size = mode->keysize;
355 	memcpy(blk_key->raw, raw_key, mode->keysize);
356 
357 	return 0;
358 }
359 
blk_crypto_config_supported_natively(struct block_device * bdev,const struct blk_crypto_config * cfg)360 bool blk_crypto_config_supported_natively(struct block_device *bdev,
361 					  const struct blk_crypto_config *cfg)
362 {
363 	return __blk_crypto_cfg_supported(bdev_get_queue(bdev)->crypto_profile,
364 					  cfg);
365 }
366 
367 /*
368  * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
369  * block_device it's submitted to supports inline crypto, or the
370  * blk-crypto-fallback is enabled and supports the cfg).
371  */
blk_crypto_config_supported(struct block_device * bdev,const struct blk_crypto_config * cfg)372 bool blk_crypto_config_supported(struct block_device *bdev,
373 				 const struct blk_crypto_config *cfg)
374 {
375 	return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
376 	       blk_crypto_config_supported_natively(bdev, cfg);
377 }
378 
379 /**
380  * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
381  * @bdev: block device to operate on
382  * @key: A key to use on the device
383  *
384  * Upper layers must call this function to ensure that either the hardware
385  * supports the key's crypto settings, or the crypto API fallback has transforms
386  * for the needed mode allocated and ready to go. This function may allocate
387  * an skcipher, and *should not* be called from the data path, since that might
388  * cause a deadlock
389  *
390  * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
391  *	   blk-crypto-fallback is either disabled or the needed algorithm
392  *	   is disabled in the crypto API; or another -errno code.
393  */
blk_crypto_start_using_key(struct block_device * bdev,const struct blk_crypto_key * key)394 int blk_crypto_start_using_key(struct block_device *bdev,
395 			       const struct blk_crypto_key *key)
396 {
397 	if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
398 		return 0;
399 	return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
400 }
401 
402 /**
403  * blk_crypto_evict_key() - Evict a blk_crypto_key from a block_device
404  * @bdev: a block_device on which I/O using the key may have been done
405  * @key: the key to evict
406  *
407  * For a given block_device, this function removes the given blk_crypto_key from
408  * the keyslot management structures and evicts it from any underlying hardware
409  * keyslot(s) or blk-crypto-fallback keyslot it may have been programmed into.
410  *
411  * Upper layers must call this before freeing the blk_crypto_key.  It must be
412  * called for every block_device the key may have been used on.  The key must no
413  * longer be in use by any I/O when this function is called.
414  *
415  * Context: May sleep.
416  */
blk_crypto_evict_key(struct block_device * bdev,const struct blk_crypto_key * key)417 void blk_crypto_evict_key(struct block_device *bdev,
418 			  const struct blk_crypto_key *key)
419 {
420 	struct request_queue *q = bdev_get_queue(bdev);
421 	int err;
422 
423 	if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
424 		err = __blk_crypto_evict_key(q->crypto_profile, key);
425 	else
426 		err = blk_crypto_fallback_evict_key(key);
427 	/*
428 	 * An error can only occur here if the key failed to be evicted from a
429 	 * keyslot (due to a hardware or driver issue) or is allegedly still in
430 	 * use by I/O (due to a kernel bug).  Even in these cases, the key is
431 	 * still unlinked from the keyslot management structures, and the caller
432 	 * is allowed and expected to free it right away.  There's nothing
433 	 * callers can do to handle errors, so just log them and return void.
434 	 */
435 	if (err)
436 		pr_warn_ratelimited("%pg: error %d evicting key\n", bdev, err);
437 }
438 EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
439