// SPDX-License-Identifier: GPL-2.0/* * Inline encryption support for fscrypt * * Copyright 2019 Google LLC */ /* * With "inline encryption", the block layer handles the decryption/encryption * as part of the bio, instead of the filesystem doing the crypto itself via * crypto API.  See Documentation/block/inline-encryption.rst.  fscrypt still * provides the key and IV to use. */ #include <linux/blk-crypto.h>#include <linux/blkdev.h>#include <linux/buffer_head.h>#include <linux/sched/mm.h>#include <linux/slab.h>#include <linux/uio.h> #include "fscrypt_private.h" static struct block_device **fscrypt_get_devices(struct super_block *sb,						 unsigned int *num_devs){	struct block_device **devs; 	if (sb->s_cop->get_devices) {		devs = sb->s_cop->get_devices(sb, num_devs);		if (devs)			return devs;	}	devs = kmalloc(sizeof(*devs), GFP_KERNEL);	if (!devs)		return ERR_PTR(-ENOMEM);	devs[0] = sb->s_bdev;	*num_devs = 1;	return devs;} static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_inode_info *ci){	const struct super_block *sb = ci->ci_inode->i_sb;	unsigned int flags = fscrypt_policy_flags(&ci->ci_policy);	int dun_bits; 	if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)		return offsetofend(union fscrypt_iv, nonce); 	if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64)		return sizeof(__le64); 	if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)		return sizeof(__le32); 	/* Default case: IVs are just the file data unit index */	dun_bits = fscrypt_max_file_dun_bits(sb, ci->ci_data_unit_bits);	return DIV_ROUND_UP(dun_bits, 8);} /* * Log a message when starting to use blk-crypto (native) or blk-crypto-fallback * for an encryption mode for the first time.  This is the blk-crypto * counterpart to the message logged when starting to use the crypto API for the * first time.  A limitation is that these messages don't convey which specific * filesystems or files are using each implementation.  However, *usually* * systems use just one implementation per mode, which makes these messages * helpful for debugging problems where the "wrong" implementation is used. */static void fscrypt_log_blk_crypto_impl(struct fscrypt_mode *mode,					struct block_device **devs,					unsigned int num_devs,					const struct blk_crypto_config *cfg){	unsigned int i; 	for (i = 0; i < num_devs; i++) {		if (!IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||		    blk_crypto_config_supported_natively(devs[i], cfg)) {			if (!xchg(&mode->logged_blk_crypto_native, 1))				pr_info("fscrypt: %s using blk-crypto (native)\n",					mode->friendly_name);		} else if (!xchg(&mode->logged_blk_crypto_fallback, 1)) {			pr_info("fscrypt: %s using blk-crypto-fallback\n",				mode->friendly_name);		}	}} /* Enable inline encryption for this file if supported. */int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci){	const struct inode *inode = ci->ci_inode;	struct super_block *sb = inode->i_sb;	struct blk_crypto_config crypto_cfg;	struct block_device **devs;	unsigned int num_devs;	unsigned int i; 	/* The file must need contents encryption, not filenames encryption */	if (!S_ISREG(inode->i_mode))		return 0; 	/* The crypto mode must have a blk-crypto counterpart */	if (ci->ci_mode->blk_crypto_mode == BLK_ENCRYPTION_MODE_INVALID)		return 0; 	/* The filesystem must be mounted with -o inlinecrypt */	if (!(sb->s_flags & SB_INLINECRYPT))		return 0; 	/*	 * When a page contains multiple logically contiguous filesystem blocks,	 * some filesystem code only calls fscrypt_mergeable_bio() for the first	 * block in the page. This is fine for most of fscrypt's IV generation	 * strategies, where contiguous blocks imply contiguous IVs. But it	 * doesn't work with IV_INO_LBLK_32. For now, simply exclude	 * IV_INO_LBLK_32 with blocksize != PAGE_SIZE from inline encryption.	 */	if ((fscrypt_policy_flags(&ci->ci_policy) &	     FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) &&	    sb->s_blocksize != PAGE_SIZE)		return 0; 	/*	 * On all the filesystem's block devices, blk-crypto must support the	 * crypto configuration that the file would use.	 */	crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode;	crypto_cfg.data_unit_size = 1U << ci->ci_data_unit_bits;	crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci); 	devs = fscrypt_get_devices(sb, &num_devs);	if (IS_ERR(devs))		return PTR_ERR(devs); 	for (i = 0; i < num_devs; i++) {		if (!blk_crypto_config_supported(devs[i], &crypto_cfg))			goto out_free_devs;	} 	fscrypt_log_blk_crypto_impl(ci->ci_mode, devs, num_devs, &crypto_cfg); 	ci->ci_inlinecrypt = true;out_free_devs:	kfree(devs); 	return 0;} int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,				     const u8 *raw_key,				     const struct fscrypt_inode_info *ci){	const struct inode *inode = ci->ci_inode;	struct super_block *sb = inode->i_sb;	enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode;	struct blk_crypto_key *blk_key;	struct block_device **devs;	unsigned int num_devs;	unsigned int i;	int err; 	blk_key = kmalloc(sizeof(*blk_key), GFP_KERNEL);	if (!blk_key)		return -ENOMEM; 	err = blk_crypto_init_key(blk_key, raw_key, crypto_mode,				  fscrypt_get_dun_bytes(ci),				  1U << ci->ci_data_unit_bits);	if (err) {		fscrypt_err(inode, "error %d initializing blk-crypto key", err);		goto fail;	} 	/* Start using blk-crypto on all the filesystem's block devices. */	devs = fscrypt_get_devices(sb, &num_devs);	if (IS_ERR(devs)) {		err = PTR_ERR(devs);		goto fail;	}	for (i = 0; i < num_devs; i++) {		err = blk_crypto_start_using_key(devs[i], blk_key);		if (err)			break;	}	kfree(devs);	if (err) {		fscrypt_err(inode, "error %d starting to use blk-crypto", err);		goto fail;	} 	/*	 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().	 * I.e., here we publish ->blk_key with a RELEASE barrier so that	 * concurrent tasks can ACQUIRE it.  Note that this concurrency is only	 * possible for per-mode keys, not for per-file keys.	 */	smp_store_release(&prep_key->blk_key, blk_key);	return 0; fail:	kfree_sensitive(blk_key);	return err;} void fscrypt_destroy_inline_crypt_key(struct super_block *sb,				      struct fscrypt_prepared_key *prep_key){	struct blk_crypto_key *blk_key = prep_key->blk_key;	struct block_device **devs;	unsigned int num_devs;	unsigned int i; 	if (!blk_key)		return; 	/* Evict the key from all the filesystem's block devices. */	devs = fscrypt_get_devices(sb, &num_devs);	if (!IS_ERR(devs)) {		for (i = 0; i < num_devs; i++)			blk_crypto_evict_key(devs[i], blk_key);		kfree(devs);	}	kfree_sensitive(blk_key);} bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode){	return inode->i_crypt_info->ci_inlinecrypt;}EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto); static void fscrypt_generate_dun(const struct fscrypt_inode_info *ci,				 u64 lblk_num,				 u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]){	u64 index = lblk_num << ci->ci_data_units_per_block_bits;	union fscrypt_iv iv;	int i; 	fscrypt_generate_iv(&iv, index, ci); 	BUILD_BUG_ON(FSCRYPT_MAX_IV_SIZE > BLK_CRYPTO_MAX_IV_SIZE);	memset(dun, 0, BLK_CRYPTO_MAX_IV_SIZE);	for (i = 0; i < ci->ci_mode->ivsize/sizeof(dun[0]); i++)		dun[i] = le64_to_cpu(iv.dun[i]);} /** * fscrypt_set_bio_crypt_ctx() - prepare a file contents bio for inline crypto * @bio: a bio which will eventually be submitted to the file * @inode: the file's inode * @first_lblk: the first file logical block number in the I/O * @gfp_mask: memory allocation flags - these must be a waiting mask so that *					bio_crypt_set_ctx can't fail. * * If the contents of the file should be encrypted (or decrypted) with inline * encryption, then assign the appropriate encryption context to the bio. * * Normally the bio should be newly allocated (i.e. no pages added yet), as * otherwise fscrypt_mergeable_bio() won't work as intended. * * The encryption context will be freed automatically when the bio is freed. */void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode,			       u64 first_lblk, gfp_t gfp_mask){	const struct fscrypt_inode_info *ci;	u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; 	if (!fscrypt_inode_uses_inline_crypto(inode))		return;	ci = inode->i_crypt_info; 	fscrypt_generate_dun(ci, first_lblk, dun);	bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);}EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx); /* Extract the inode and logical block number from a buffer_head. */static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh,				      const struct inode **inode_ret,				      u64 *lblk_num_ret){	struct folio *folio = bh->b_folio;	const struct address_space *mapping;	const struct inode *inode; 	/*	 * The ext4 journal (jbd2) can submit a buffer_head it directly created	 * for a non-pagecache page.  fscrypt doesn't care about these.	 */	mapping = folio_mapping(folio);	if (!mapping)		return false;	inode = mapping->host; 	*inode_ret = inode;	*lblk_num_ret = ((u64)folio->index << (PAGE_SHIFT - inode->i_blkbits)) +			(bh_offset(bh) >> inode->i_blkbits);	return true;} /** * fscrypt_set_bio_crypt_ctx_bh() - prepare a file contents bio for inline *				    crypto * @bio: a bio which will eventually be submitted to the file * @first_bh: the first buffer_head for which I/O will be submitted * @gfp_mask: memory allocation flags * * Same as fscrypt_set_bio_crypt_ctx(), except this takes a buffer_head instead * of an inode and block number directly. */void fscrypt_set_bio_crypt_ctx_bh(struct bio *bio,				  const struct buffer_head *first_bh,				  gfp_t gfp_mask){	const struct inode *inode;	u64 first_lblk; 	if (bh_get_inode_and_lblk_num(first_bh, &inode, &first_lblk))		fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk, gfp_mask);}EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh); /** * fscrypt_mergeable_bio() - test whether data can be added to a bio * @bio: the bio being built up * @inode: the inode for the next part of the I/O * @next_lblk: the next file logical block number in the I/O * * When building a bio which may contain data which should undergo inline * encryption (or decryption) via fscrypt, filesystems should call this function * to ensure that the resulting bio contains only contiguous data unit numbers. * This will return false if the next part of the I/O cannot be merged with the * bio because either the encryption key would be different or the encryption * data unit numbers would be discontiguous. * * fscrypt_set_bio_crypt_ctx() must have already been called on the bio. * * This function isn't required in cases where crypto-mergeability is ensured in * another way, such as I/O targeting only a single file (and thus a single key) * combined with fscrypt_limit_io_blocks() to ensure DUN contiguity. * * Return: true iff the I/O is mergeable */bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode,			   u64 next_lblk){	const struct bio_crypt_ctx *bc = bio->bi_crypt_context;	u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; 	if (!!bc != fscrypt_inode_uses_inline_crypto(inode))		return false;	if (!bc)		return true; 	/*	 * Comparing the key pointers is good enough, as all I/O for each key	 * uses the same pointer.  I.e., there's currently no need to support	 * merging requests where the keys are the same but the pointers differ.	 */	if (bc->bc_key != inode->i_crypt_info->ci_enc_key.blk_key)		return false; 	fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun);	return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun);}EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio); /** * fscrypt_mergeable_bio_bh() - test whether data can be added to a bio * @bio: the bio being built up * @next_bh: the next buffer_head for which I/O will be submitted * * Same as fscrypt_mergeable_bio(), except this takes a buffer_head instead of * an inode and block number directly. * * Return: true iff the I/O is mergeable */bool fscrypt_mergeable_bio_bh(struct bio *bio,			      const struct buffer_head *next_bh){	const struct inode *inode;	u64 next_lblk; 	if (!bh_get_inode_and_lblk_num(next_bh, &inode, &next_lblk))		return !bio->bi_crypt_context; 	return fscrypt_mergeable_bio(bio, inode, next_lblk);}EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh); /** * fscrypt_dio_supported() - check whether DIO (direct I/O) is supported on an *			     inode, as far as encryption is concerned * @inode: the inode in question * * Return: %true if there are no encryption constraints that prevent DIO from *	   being supported; %false if DIO is unsupported.  (Note that in the *	   %true case, the filesystem might have other, non-encryption-related *	   constraints that prevent DIO from actually being supported.  Also, on *	   encrypted files the filesystem is still responsible for only allowing *	   DIO when requests are filesystem-block-aligned.) */bool fscrypt_dio_supported(struct inode *inode){	int err; 	/* If the file is unencrypted, no veto from us. */	if (!fscrypt_needs_contents_encryption(inode))		return true; 	/*	 * We only support DIO with inline crypto, not fs-layer crypto.	 *	 * To determine whether the inode is using inline crypto, we have to set	 * up the key if it wasn't already done.  This is because in the current	 * design of fscrypt, the decision of whether to use inline crypto or	 * not isn't made until the inode's encryption key is being set up.  In	 * the DIO read/write case, the key will always be set up already, since	 * the file will be open.  But in the case of statx(), the key might not	 * be set up yet, as the file might not have been opened yet.	 */	err = fscrypt_require_key(inode);	if (err) {		/*		 * Key unavailable or couldn't be set up.  This edge case isn't		 * worth worrying about; just report that DIO is unsupported.		 */		return false;	}	return fscrypt_inode_uses_inline_crypto(inode);}EXPORT_SYMBOL_GPL(fscrypt_dio_supported); /** * fscrypt_limit_io_blocks() - limit I/O blocks to avoid discontiguous DUNs * @inode: the file on which I/O is being done * @lblk: the block at which the I/O is being started from * @nr_blocks: the number of blocks we want to submit starting at @lblk * * Determine the limit to the number of blocks that can be submitted in a bio * targeting @lblk without causing a data unit number (DUN) discontiguity. * * This is normally just @nr_blocks, as normally the DUNs just increment along * with the logical blocks.  (Or the file is not encrypted.) * * In rare cases, fscrypt can be using an IV generation method that allows the * DUN to wrap around within logically contiguous blocks, and that wraparound * will occur.  If this happens, a value less than @nr_blocks will be returned * so that the wraparound doesn't occur in the middle of a bio, which would * cause encryption/decryption to produce wrong results. * * Return: the actual number of blocks that can be submitted */u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks){	const struct fscrypt_inode_info *ci;	u32 dun; 	if (!fscrypt_inode_uses_inline_crypto(inode))		return nr_blocks; 	if (nr_blocks <= 1)		return nr_blocks; 	ci = inode->i_crypt_info;	if (!(fscrypt_policy_flags(&ci->ci_policy) &	      FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))		return nr_blocks; 	/* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */ 	dun = ci->ci_hashed_ino + lblk; 	return min_t(u64, nr_blocks, (u64)U32_MAX + 1 - dun);}EXPORT_SYMBOL_GPL(fscrypt_limit_io_blocks);