// SPDX-License-Identifier: GPL-2.0/* * File contents en/decryption on block-based filesystems * * Copyright 2019 Google LLC */ /* * This file implements fscrypt's file contents en/decryption using blk-crypto * (Documentation/block/inline-encryption.rst).  fscrypt assigns a bio_crypt_ctx * with a key and IV to each bio, and the block layer does the en/decryption. * * This file's exported functions are called only by block-based filesystems. */ #include <linux/blk-crypto.h>#include <linux/blkdev.h>#include <linux/export.h>#include <linux/sched/mm.h>#include <linux/slab.h>#include <linux/uio.h> #include "fscrypt_private.h" static unsigned intfscrypt_get_devices(struct super_block *sb,		    struct block_device *devs[FSCRYPT_MAX_DEVICES]){	if (sb->s_cop->get_devices)		return sb->s_cop->get_devices(sb, devs);	devs[0] = sb->s_bdev;	return 1;} 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 *dev,					const struct blk_crypto_key *blk_key){	if (blk_crypto_config_supported_natively(dev, &blk_key->crypto_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);	}} int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,				     const u8 *key_bytes, size_t key_size,				     bool is_hw_wrapped,				     const struct fscrypt_inode_info *ci){	const struct inode *inode = ci->ci_inode;	struct super_block *sb = inode->i_sb;	bool inlinecrypt = sb->s_flags & SB_INLINECRYPT;	struct fscrypt_mode *mode = ci->ci_mode;	enum blk_crypto_key_type key_type = is_hw_wrapped ?		BLK_CRYPTO_KEY_TYPE_HW_WRAPPED : BLK_CRYPTO_KEY_TYPE_RAW;	struct blk_crypto_key *blk_key;	struct block_device *devs[FSCRYPT_MAX_DEVICES];	unsigned int num_devs;	unsigned int i;	int err; 	if (is_hw_wrapped && !inlinecrypt) {		/*		 * blk_crypto_init_key() would catch this anyway, but this		 * provides a clearer error message.		 */		fscrypt_err(			inode,			"Hardware-wrapped keys require inline encryption (-o inlinecrypt)");		return -EINVAL;	} 	blk_key = kmalloc_obj(*blk_key);	if (!blk_key)		return -ENOMEM; 	err = blk_crypto_init_key(blk_key, key_bytes, key_size, key_type,				  mode->blk_crypto_mode,				  fscrypt_get_dun_bytes(ci),				  1U << ci->ci_data_unit_bits,				  inlinecrypt ? BLK_CRYPTO_CFG_ALLOW_HW : 0);	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. */	num_devs = fscrypt_get_devices(sb, devs);	for (i = 0; i < num_devs; i++) {		err = blk_crypto_start_using_key(devs[i], blk_key);		if (err)			break;		fscrypt_log_blk_crypto_impl(mode, devs[i], blk_key);	}	if (err) {		if (err == -EOPNOTSUPP && is_hw_wrapped)			fscrypt_err(				inode,				"Hardware-wrapped key required, but no suitable inline encryption capabilities are available");		else			fscrypt_err(inode,				    "Error %d starting to use blk-crypto", err);		goto fail;	} 	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[FSCRYPT_MAX_DEVICES];	unsigned int num_devs;	unsigned int i; 	if (!blk_key)		return; 	/*	 * Evict the key from all the filesystem's block devices.	 * This *must* be done before the key is freed.	 */	num_devs = fscrypt_get_devices(sb, devs);	for (i = 0; i < num_devs; i++)		blk_crypto_evict_key(devs[i], blk_key); 	kfree_sensitive(blk_key);} /* * Ask the inline encryption hardware to derive the software secret from a * hardware-wrapped key.  Returns -EOPNOTSUPP if hardware-wrapped keys aren't * supported on this filesystem or hardware. */int fscrypt_derive_sw_secret(struct super_block *sb,			     const u8 *wrapped_key, size_t wrapped_key_size,			     u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE]){	int err; 	/* The filesystem must be mounted with -o inlinecrypt. */	if (!(sb->s_flags & SB_INLINECRYPT)) {		fscrypt_warn(NULL,			     "%s: filesystem not mounted with inlinecrypt\n",			     sb->s_id);		return -EOPNOTSUPP;	} 	err = blk_crypto_derive_sw_secret(sb->s_bdev, wrapped_key,					  wrapped_key_size, sw_secret);	if (err == -EOPNOTSUPP)		fscrypt_warn(NULL,			     "%s: block device doesn't support hardware-wrapped keys\n",			     sb->s_id);	return err;} static void fscrypt_generate_dun(const struct fscrypt_inode_info *ci,				 loff_t pos, u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]){	union fscrypt_iv iv;	int i; 	fscrypt_generate_iv(&iv, pos >> ci->ci_data_unit_bits, 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 * @pos: the first file position (in bytes) 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), 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,			       loff_t pos, gfp_t gfp_mask){	const struct fscrypt_inode_info *ci;	u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; 	if (!fscrypt_needs_contents_encryption(inode))		return;	ci = fscrypt_get_inode_info_raw(inode); 	fscrypt_generate_dun(ci, pos, dun);	bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);}EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx); /** * 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 * @pos: the next file position (in bytes) in the I/O * * When building a bio which may contain data which should undergo 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,			   loff_t pos){	const struct bio_crypt_ctx *bc = bio->bi_crypt_context;	const struct fscrypt_inode_info *ci;	u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; 	if (!!bc != fscrypt_needs_contents_encryption(inode))		return false;	if (!bc)		return true;	ci = fscrypt_get_inode_info_raw(inode); 	/*	 * 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 != ci->ci_enc_key.blk_key)		return false; 	fscrypt_generate_dun(ci, pos, next_dun);	return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun);}EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio); /** * 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_needs_contents_encryption(inode))		return nr_blocks; 	if (nr_blocks <= 1)		return nr_blocks; 	ci = fscrypt_get_inode_info_raw(inode);	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); struct fscrypt_zero_done {	atomic_t		pending;	blk_status_t		status;	struct completion	done;}; static void fscrypt_zeroout_range_done(struct fscrypt_zero_done *done){	if (atomic_dec_and_test(&done->pending))		complete(&done->done);} static void fscrypt_zeroout_range_end_io(struct bio *bio){	struct fscrypt_zero_done *done = bio->bi_private; 	if (bio->bi_status)		cmpxchg(&done->status, 0, bio->bi_status);	fscrypt_zeroout_range_done(done);	bio_put(bio);} /** * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file * @inode: the file's inode * @pos: the first file position (in bytes) to zero out * @sector: the first sector to zero out * @len: bytes to zero out * * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write * ciphertext blocks which decrypt to the all-zeroes block.  The blocks must be * both logically and physically contiguous.  It's also assumed that the * filesystem only uses a single block device, ->s_bdev.  @len must be a * multiple of the file system logical block size. * * Note that since each block uses a different IV, this involves writing a * different ciphertext to each block; we can't simply reuse the same one. * * Return: 0 on success; -errno on failure. */int fscrypt_zeroout_range(const struct inode *inode, loff_t pos,			  sector_t sector, u64 len){	struct fscrypt_zero_done done = {		.pending	= ATOMIC_INIT(1),		.done		= COMPLETION_INITIALIZER_ONSTACK(done.done),	}; 	if (len == 0)		return 0; 	do {		struct bio *bio;		unsigned int n; 		bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,				GFP_NOFS);		bio->bi_iter.bi_sector = sector;		bio->bi_private = &done;		bio->bi_end_io = fscrypt_zeroout_range_end_io;		fscrypt_set_bio_crypt_ctx(bio, inode, pos, GFP_NOFS); 		for (n = 0; n < BIO_MAX_VECS; n++) {			unsigned int bytes_this_page = min(len, PAGE_SIZE); 			__bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);			len -= bytes_this_page;			pos += bytes_this_page;			sector += (bytes_this_page >> SECTOR_SHIFT);			if (!len || !fscrypt_mergeable_bio(bio, inode, pos))				break;		} 		atomic_inc(&done.pending);		blk_crypto_submit_bio(bio);	} while (len); 	fscrypt_zeroout_range_done(&done); 	wait_for_completion(&done.done);	return blk_status_to_errno(done.status);}EXPORT_SYMBOL(fscrypt_zeroout_range);