blk-crypto.c

  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
 21const 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		.security_strength = 32,
 27		.ivsize = 16,
 28	},
 29	[BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
 30		.name = "AES-128-CBC-ESSIV",
 31		.cipher_str = "essiv(cbc(aes),sha256)",
 32		.keysize = 16,
 33		.security_strength = 16,
 34		.ivsize = 16,
 35	},
 36	[BLK_ENCRYPTION_MODE_ADIANTUM] = {
 37		.name = "Adiantum",
 38		.cipher_str = "adiantum(xchacha12,aes)",
 39		.keysize = 32,
 40		.security_strength = 32,
 41		.ivsize = 32,
 42	},
 43	[BLK_ENCRYPTION_MODE_SM4_XTS] = {
 44		.name = "SM4-XTS",
 45		.cipher_str = "xts(sm4)",
 46		.keysize = 32,
 47		.security_strength = 16,
 48		.ivsize = 16,
 49	},
 50};
 51
 52/*
 53 * This number needs to be at least (the number of threads doing IO
 54 * concurrently) * (maximum recursive depth of a bio), so that we don't
 55 * deadlock on crypt_ctx allocations. The default is chosen to be the same
 56 * as the default number of post read contexts in both EXT4 and F2FS.
 57 */
 58static int num_prealloc_crypt_ctxs = 128;
 59
 60module_param(num_prealloc_crypt_ctxs, int, 0444);
 61MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
 62		"Number of bio crypto contexts to preallocate");
 63
 64static struct kmem_cache *bio_crypt_ctx_cache;
 65static mempool_t *bio_crypt_ctx_pool;
 66
 67static int __init bio_crypt_ctx_init(void)
 68{
 69	size_t i;
 70
 71	bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
 72	if (!bio_crypt_ctx_cache)
 73		goto out_no_mem;
 74
 75	bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
 76						      bio_crypt_ctx_cache);
 77	if (!bio_crypt_ctx_pool)
 78		goto out_no_mem;
 79
 80	/* This is assumed in various places. */
 81	BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
 82
 83	/*
 84	 * Validate the crypto mode properties.  This ideally would be done with
 85	 * static assertions, but boot-time checks are the next best thing.
 86	 */
 87	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
 88		BUG_ON(blk_crypto_modes[i].keysize >
 89		       BLK_CRYPTO_MAX_RAW_KEY_SIZE);
 90		BUG_ON(blk_crypto_modes[i].security_strength >
 91		       blk_crypto_modes[i].keysize);
 92		BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
 93	}
 94
 95	return 0;
 96out_no_mem:
 97	panic("Failed to allocate mem for bio crypt ctxs\n");
 98}
 99subsys_initcall(bio_crypt_ctx_init);
100
101void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
102		       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
103{
104	struct bio_crypt_ctx *bc;
105
106	/*
107	 * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
108	 * that the mempool_alloc() can't fail.
109	 */
110	WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
111
112	bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
113
114	bc->bc_key = key;
115	memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
116
117	bio->bi_crypt_context = bc;
118}
119
120void __bio_crypt_free_ctx(struct bio *bio)
121{
122	mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
123	bio->bi_crypt_context = NULL;
124}
125
126int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
127{
128	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
129	if (!dst->bi_crypt_context)
130		return -ENOMEM;
131	*dst->bi_crypt_context = *src->bi_crypt_context;
132	return 0;
133}
134
135/* Increments @dun by @inc, treating @dun as a multi-limb integer. */
136void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
137			     unsigned int inc)
138{
139	int i;
140
141	for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
142		dun[i] += inc;
143		/*
144		 * If the addition in this limb overflowed, then we need to
145		 * carry 1 into the next limb. Else the carry is 0.
146		 */
147		if (dun[i] < inc)
148			inc = 1;
149		else
150			inc = 0;
151	}
152}
153
154void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
155{
156	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
157
158	bio_crypt_dun_increment(bc->bc_dun,
159				bytes >> bc->bc_key->data_unit_size_bits);
160}
161
162/*
163 * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
164 * @next_dun, treating the DUNs as multi-limb integers.
165 */
166bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
167				 unsigned int bytes,
168				 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
169{
170	int i;
171	unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
172
173	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
174		if (bc->bc_dun[i] + carry != next_dun[i])
175			return false;
176		/*
177		 * If the addition in this limb overflowed, then we need to
178		 * carry 1 into the next limb. Else the carry is 0.
179		 */
180		if ((bc->bc_dun[i] + carry) < carry)
181			carry = 1;
182		else
183			carry = 0;
184	}
185
186	/* If the DUN wrapped through 0, don't treat it as contiguous. */
187	return carry == 0;
188}
189
190/*
191 * Checks that two bio crypt contexts are compatible - i.e. that
192 * they are mergeable except for data_unit_num continuity.
193 */
194static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
195				     struct bio_crypt_ctx *bc2)
196{
197	if (!bc1)
198		return !bc2;
199
200	return bc2 && bc1->bc_key == bc2->bc_key;
201}
202
203bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
204{
205	return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
206}
207
208/*
209 * Checks that two bio crypt contexts are compatible, and also
210 * that their data_unit_nums are continuous (and can hence be merged)
211 * in the order @bc1 followed by @bc2.
212 */
213bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
214			     struct bio_crypt_ctx *bc2)
215{
216	if (!bio_crypt_ctx_compatible(bc1, bc2))
217		return false;
218
219	return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
220}
221
222/* Check that all I/O segments are data unit aligned. */
223static bool bio_crypt_check_alignment(struct bio *bio)
224{
225	const unsigned int data_unit_size =
226		bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
227	struct bvec_iter iter;
228	struct bio_vec bv;
229
230	bio_for_each_segment(bv, bio, iter) {
231		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
232			return false;
233	}
234
235	return true;
236}
237
238blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq)
239{
240	return blk_crypto_get_keyslot(rq->q->crypto_profile,
241				      rq->crypt_ctx->bc_key,
242				      &rq->crypt_keyslot);
243}
244
245void __blk_crypto_rq_put_keyslot(struct request *rq)
246{
247	blk_crypto_put_keyslot(rq->crypt_keyslot);
248	rq->crypt_keyslot = NULL;
249}
250
251void __blk_crypto_free_request(struct request *rq)
252{
253	/* The keyslot, if one was needed, should have been released earlier. */
254	if (WARN_ON_ONCE(rq->crypt_keyslot))
255		__blk_crypto_rq_put_keyslot(rq);
256
257	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
258	rq->crypt_ctx = NULL;
259}
260
261/**
262 * __blk_crypto_bio_prep - Prepare bio for inline encryption
263 *
264 * @bio_ptr: pointer to original bio pointer
265 *
266 * If the bio crypt context provided for the bio is supported by the underlying
267 * device's inline encryption hardware, do nothing.
268 *
269 * Otherwise, try to perform en/decryption for this bio by falling back to the
270 * kernel crypto API. When the crypto API fallback is used for encryption,
271 * blk-crypto may choose to split the bio into 2 - the first one that will
272 * continue to be processed and the second one that will be resubmitted via
273 * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
274 * of the aforementioned "first one", and *bio_ptr will be updated to this
275 * bounce bio.
276 *
277 * Caller must ensure bio has bio_crypt_ctx.
278 *
279 * Return: true on success; false on error (and bio->bi_status will be set
280 *	   appropriately, and bio_endio() will have been called so bio
281 *	   submission should abort).
282 */
283bool __blk_crypto_bio_prep(struct bio **bio_ptr)
284{
285	struct bio *bio = *bio_ptr;
286	const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
287
288	/* Error if bio has no data. */
289	if (WARN_ON_ONCE(!bio_has_data(bio))) {
290		bio->bi_status = BLK_STS_IOERR;
291		goto fail;
292	}
293
294	if (!bio_crypt_check_alignment(bio)) {
295		bio->bi_status = BLK_STS_INVAL;
296		goto fail;
297	}
298
299	/*
300	 * Success if device supports the encryption context, or if we succeeded
301	 * in falling back to the crypto API.
302	 */
303	if (blk_crypto_config_supported_natively(bio->bi_bdev,
304						 &bc_key->crypto_cfg))
305		return true;
306	if (blk_crypto_fallback_bio_prep(bio_ptr))
307		return true;
308fail:
309	bio_endio(*bio_ptr);
310	return false;
311}
312
313int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
314			     gfp_t gfp_mask)
315{
316	if (!rq->crypt_ctx) {
317		rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
318		if (!rq->crypt_ctx)
319			return -ENOMEM;
320	}
321	*rq->crypt_ctx = *bio->bi_crypt_context;
322	return 0;
323}
324
325/**
326 * blk_crypto_init_key() - Prepare a key for use with blk-crypto
327 * @blk_key: Pointer to the blk_crypto_key to initialize.
328 * @key_bytes: the bytes of the key
329 * @key_size: size of the key in bytes
330 * @key_type: type of the key -- either raw or hardware-wrapped
331 * @crypto_mode: identifier for the encryption algorithm to use
332 * @dun_bytes: number of bytes that will be used to specify the DUN when this
333 *	       key is used
334 * @data_unit_size: the data unit size to use for en/decryption
335 *
336 * Return: 0 on success, -errno on failure.  The caller is responsible for
337 *	   zeroizing both blk_key and key_bytes when done with them.
338 */
339int blk_crypto_init_key(struct blk_crypto_key *blk_key,
340			const u8 *key_bytes, size_t key_size,
341			enum blk_crypto_key_type key_type,
342			enum blk_crypto_mode_num crypto_mode,
343			unsigned int dun_bytes,
344			unsigned int data_unit_size)
345{
346	const struct blk_crypto_mode *mode;
347
348	memset(blk_key, 0, sizeof(*blk_key));
349
350	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
351		return -EINVAL;
352
353	mode = &blk_crypto_modes[crypto_mode];
354	switch (key_type) {
355	case BLK_CRYPTO_KEY_TYPE_RAW:
356		if (key_size != mode->keysize)
357			return -EINVAL;
358		break;
359	case BLK_CRYPTO_KEY_TYPE_HW_WRAPPED:
360		if (key_size < mode->security_strength ||
361		    key_size > BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE)
362			return -EINVAL;
363		break;
364	default:
365		return -EINVAL;
366	}
367
368	if (dun_bytes == 0 || dun_bytes > mode->ivsize)
369		return -EINVAL;
370
371	if (!is_power_of_2(data_unit_size))
372		return -EINVAL;
373
374	blk_key->crypto_cfg.crypto_mode = crypto_mode;
375	blk_key->crypto_cfg.dun_bytes = dun_bytes;
376	blk_key->crypto_cfg.data_unit_size = data_unit_size;
377	blk_key->crypto_cfg.key_type = key_type;
378	blk_key->data_unit_size_bits = ilog2(data_unit_size);
379	blk_key->size = key_size;
380	memcpy(blk_key->bytes, key_bytes, key_size);
381
382	return 0;
383}
384
385bool blk_crypto_config_supported_natively(struct block_device *bdev,
386					  const struct blk_crypto_config *cfg)
387{
388	return __blk_crypto_cfg_supported(bdev_get_queue(bdev)->crypto_profile,
389					  cfg);
390}
391
392/*
393 * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
394 * block_device it's submitted to supports inline crypto, or the
395 * blk-crypto-fallback is enabled and supports the cfg).
396 */
397bool blk_crypto_config_supported(struct block_device *bdev,
398				 const struct blk_crypto_config *cfg)
399{
400	if (IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) &&
401	    cfg->key_type == BLK_CRYPTO_KEY_TYPE_RAW)
402		return true;
403	return blk_crypto_config_supported_natively(bdev, cfg);
404}
405
406/**
407 * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
408 * @bdev: block device to operate on
409 * @key: A key to use on the device
410 *
411 * Upper layers must call this function to ensure that either the hardware
412 * supports the key's crypto settings, or the crypto API fallback has transforms
413 * for the needed mode allocated and ready to go. This function may allocate
414 * an skcipher, and *should not* be called from the data path, since that might
415 * cause a deadlock
416 *
417 * Return: 0 on success; -EOPNOTSUPP if the key is wrapped but the hardware does
418 *	   not support wrapped keys; -ENOPKG if the key is a raw key but the
419 *	   hardware does not support raw keys and blk-crypto-fallback is either
420 *	   disabled or the needed algorithm is disabled in the crypto API; or
421 *	   another -errno code if something else went wrong.
422 */
423int blk_crypto_start_using_key(struct block_device *bdev,
424			       const struct blk_crypto_key *key)
425{
426	if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
427		return 0;
428	if (key->crypto_cfg.key_type != BLK_CRYPTO_KEY_TYPE_RAW) {
429		pr_warn_ratelimited("%pg: no support for wrapped keys\n", bdev);
430		return -EOPNOTSUPP;
431	}
432	return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
433}
434
435/**
436 * blk_crypto_evict_key() - Evict a blk_crypto_key from a block_device
437 * @bdev: a block_device on which I/O using the key may have been done
438 * @key: the key to evict
439 *
440 * For a given block_device, this function removes the given blk_crypto_key from
441 * the keyslot management structures and evicts it from any underlying hardware
442 * keyslot(s) or blk-crypto-fallback keyslot it may have been programmed into.
443 *
444 * Upper layers must call this before freeing the blk_crypto_key.  It must be
445 * called for every block_device the key may have been used on.  The key must no
446 * longer be in use by any I/O when this function is called.
447 *
448 * Context: May sleep.
449 */
450void blk_crypto_evict_key(struct block_device *bdev,
451			  const struct blk_crypto_key *key)
452{
453	struct request_queue *q = bdev_get_queue(bdev);
454	int err;
455
456	if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
457		err = __blk_crypto_evict_key(q->crypto_profile, key);
458	else
459		err = blk_crypto_fallback_evict_key(key);
460	/*
461	 * An error can only occur here if the key failed to be evicted from a
462	 * keyslot (due to a hardware or driver issue) or is allegedly still in
463	 * use by I/O (due to a kernel bug).  Even in these cases, the key is
464	 * still unlinked from the keyslot management structures, and the caller
465	 * is allowed and expected to free it right away.  There's nothing
466	 * callers can do to handle errors, so just log them and return void.
467	 */
468	if (err)
469		pr_warn_ratelimited("%pg: error %d evicting key\n", bdev, err);
470}
471EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
472
473static int blk_crypto_ioctl_import_key(struct blk_crypto_profile *profile,
474				       void __user *argp)
475{
476	struct blk_crypto_import_key_arg arg;
477	u8 raw_key[BLK_CRYPTO_MAX_RAW_KEY_SIZE];
478	u8 lt_key[BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE];
479	int ret;
480
481	if (copy_from_user(&arg, argp, sizeof(arg)))
482		return -EFAULT;
483
484	if (memchr_inv(arg.reserved, 0, sizeof(arg.reserved)))
485		return -EINVAL;
486
487	if (arg.raw_key_size < 16 || arg.raw_key_size > sizeof(raw_key))
488		return -EINVAL;
489
490	if (copy_from_user(raw_key, u64_to_user_ptr(arg.raw_key_ptr),
491			   arg.raw_key_size)) {
492		ret = -EFAULT;
493		goto out;
494	}
495	ret = blk_crypto_import_key(profile, raw_key, arg.raw_key_size, lt_key);
496	if (ret < 0)
497		goto out;
498	if (ret > arg.lt_key_size) {
499		ret = -EOVERFLOW;
500		goto out;
501	}
502	arg.lt_key_size = ret;
503	if (copy_to_user(u64_to_user_ptr(arg.lt_key_ptr), lt_key,
504			 arg.lt_key_size) ||
505	    copy_to_user(argp, &arg, sizeof(arg))) {
506		ret = -EFAULT;
507		goto out;
508	}
509	ret = 0;
510
511out:
512	memzero_explicit(raw_key, sizeof(raw_key));
513	memzero_explicit(lt_key, sizeof(lt_key));
514	return ret;
515}
516
517static int blk_crypto_ioctl_generate_key(struct blk_crypto_profile *profile,
518					 void __user *argp)
519{
520	struct blk_crypto_generate_key_arg arg;
521	u8 lt_key[BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE];
522	int ret;
523
524	if (copy_from_user(&arg, argp, sizeof(arg)))
525		return -EFAULT;
526
527	if (memchr_inv(arg.reserved, 0, sizeof(arg.reserved)))
528		return -EINVAL;
529
530	ret = blk_crypto_generate_key(profile, lt_key);
531	if (ret < 0)
532		goto out;
533	if (ret > arg.lt_key_size) {
534		ret = -EOVERFLOW;
535		goto out;
536	}
537	arg.lt_key_size = ret;
538	if (copy_to_user(u64_to_user_ptr(arg.lt_key_ptr), lt_key,
539			 arg.lt_key_size) ||
540	    copy_to_user(argp, &arg, sizeof(arg))) {
541		ret = -EFAULT;
542		goto out;
543	}
544	ret = 0;
545
546out:
547	memzero_explicit(lt_key, sizeof(lt_key));
548	return ret;
549}
550
551static int blk_crypto_ioctl_prepare_key(struct blk_crypto_profile *profile,
552					void __user *argp)
553{
554	struct blk_crypto_prepare_key_arg arg;
555	u8 lt_key[BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE];
556	u8 eph_key[BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE];
557	int ret;
558
559	if (copy_from_user(&arg, argp, sizeof(arg)))
560		return -EFAULT;
561
562	if (memchr_inv(arg.reserved, 0, sizeof(arg.reserved)))
563		return -EINVAL;
564
565	if (arg.lt_key_size > sizeof(lt_key))
566		return -EINVAL;
567
568	if (copy_from_user(lt_key, u64_to_user_ptr(arg.lt_key_ptr),
569			   arg.lt_key_size)) {
570		ret = -EFAULT;
571		goto out;
572	}
573	ret = blk_crypto_prepare_key(profile, lt_key, arg.lt_key_size, eph_key);
574	if (ret < 0)
575		goto out;
576	if (ret > arg.eph_key_size) {
577		ret = -EOVERFLOW;
578		goto out;
579	}
580	arg.eph_key_size = ret;
581	if (copy_to_user(u64_to_user_ptr(arg.eph_key_ptr), eph_key,
582			 arg.eph_key_size) ||
583	    copy_to_user(argp, &arg, sizeof(arg))) {
584		ret = -EFAULT;
585		goto out;
586	}
587	ret = 0;
588
589out:
590	memzero_explicit(lt_key, sizeof(lt_key));
591	memzero_explicit(eph_key, sizeof(eph_key));
592	return ret;
593}
594
595int blk_crypto_ioctl(struct block_device *bdev, unsigned int cmd,
596		     void __user *argp)
597{
598	struct blk_crypto_profile *profile =
599		bdev_get_queue(bdev)->crypto_profile;
600
601	if (!profile)
602		return -EOPNOTSUPP;
603
604	switch (cmd) {
605	case BLKCRYPTOIMPORTKEY:
606		return blk_crypto_ioctl_import_key(profile, argp);
607	case BLKCRYPTOGENERATEKEY:
608		return blk_crypto_ioctl_generate_key(profile, argp);
609	case BLKCRYPTOPREPAREKEY:
610		return blk_crypto_ioctl_prepare_key(profile, argp);
611	default:
612		return -ENOTTY;
613	}
614}