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- // 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/keyslot-manager.h>
- #include <linux/sched/mm.h>
- #include <linux/slab.h>
- #include <linux/uio.h>
- #include "fscrypt_private.h"
- struct fscrypt_blk_crypto_key {
- struct blk_crypto_key base;
- int num_devs;
- struct request_queue *devs[];
- };
- static int fscrypt_get_num_devices(struct super_block *sb)
- {
- if (sb->s_cop->get_num_devices)
- return sb->s_cop->get_num_devices(sb);
- return 1;
- }
- static void fscrypt_get_devices(struct super_block *sb, int num_devs,
- struct request_queue **devs)
- {
- if (num_devs == 1)
- devs[0] = bdev_get_queue(sb->s_bdev);
- else
- sb->s_cop->get_devices(sb, devs);
- }
- static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_info *ci)
- {
- struct super_block *sb = ci->ci_inode->i_sb;
- unsigned int flags = fscrypt_policy_flags(&ci->ci_policy);
- int ino_bits = 64, lblk_bits = 64;
- 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 logical block number */
- if (sb->s_cop->get_ino_and_lblk_bits)
- sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
- return DIV_ROUND_UP(lblk_bits, 8);
- }
- /* Enable inline encryption for this file if supported. */
- int fscrypt_select_encryption_impl(struct fscrypt_info *ci,
- bool is_hw_wrapped_key)
- {
- const struct inode *inode = ci->ci_inode;
- struct super_block *sb = inode->i_sb;
- struct blk_crypto_config crypto_cfg;
- int num_devs;
- struct request_queue **devs;
- 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 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 = sb->s_blocksize;
- crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci);
- crypto_cfg.is_hw_wrapped = is_hw_wrapped_key;
- num_devs = fscrypt_get_num_devices(sb);
- devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
- if (!devs)
- return -ENOMEM;
- fscrypt_get_devices(sb, num_devs, devs);
- for (i = 0; i < num_devs; i++) {
- if (!blk_crypto_config_supported(devs[i], &crypto_cfg))
- goto out_free_devs;
- }
- 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,
- unsigned int raw_key_size,
- bool is_hw_wrapped,
- const struct fscrypt_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;
- int num_devs = fscrypt_get_num_devices(sb);
- int queue_refs = 0;
- struct fscrypt_blk_crypto_key *blk_key;
- int err;
- int i;
- blk_key = kzalloc(struct_size(blk_key, devs, num_devs), GFP_KERNEL);
- if (!blk_key)
- return -ENOMEM;
- blk_key->num_devs = num_devs;
- fscrypt_get_devices(sb, num_devs, blk_key->devs);
- BUILD_BUG_ON(FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE >
- BLK_CRYPTO_MAX_WRAPPED_KEY_SIZE);
- err = blk_crypto_init_key(&blk_key->base, raw_key, raw_key_size,
- is_hw_wrapped, crypto_mode,
- fscrypt_get_dun_bytes(ci), sb->s_blocksize);
- if (err) {
- fscrypt_err(inode, "error %d initializing blk-crypto key", err);
- goto fail;
- }
- /*
- * We have to start using blk-crypto on all the filesystem's devices.
- * We also have to save all the request_queue's for later so that the
- * key can be evicted from them. This is needed because some keys
- * aren't destroyed until after the filesystem was already unmounted
- * (namely, the per-mode keys in struct fscrypt_master_key).
- */
- for (i = 0; i < num_devs; i++) {
- if (!blk_get_queue(blk_key->devs[i])) {
- fscrypt_err(inode, "couldn't get request_queue");
- err = -EAGAIN;
- goto fail;
- }
- queue_refs++;
- err = blk_crypto_start_using_key(&blk_key->base,
- blk_key->devs[i]);
- 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:
- for (i = 0; i < queue_refs; i++)
- blk_put_queue(blk_key->devs[i]);
- kfree_sensitive(blk_key);
- return err;
- }
- void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
- {
- struct fscrypt_blk_crypto_key *blk_key = prep_key->blk_key;
- int i;
- if (blk_key) {
- for (i = 0; i < blk_key->num_devs; i++) {
- blk_crypto_evict_key(blk_key->devs[i], &blk_key->base);
- blk_put_queue(blk_key->devs[i]);
- }
- kfree_sensitive(blk_key);
- }
- }
- int fscrypt_derive_raw_secret(struct super_block *sb,
- const u8 *wrapped_key,
- unsigned int wrapped_key_size,
- u8 *raw_secret, unsigned int raw_secret_size)
- {
- struct request_queue *q;
- q = bdev_get_queue(sb->s_bdev);
- if (!q->ksm)
- return -EOPNOTSUPP;
- return blk_ksm_derive_raw_secret(q->ksm, wrapped_key, wrapped_key_size,
- raw_secret, raw_secret_size);
- }
- 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_info *ci, u64 lblk_num,
- u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
- {
- union fscrypt_iv iv;
- int i;
- fscrypt_generate_iv(&iv, lblk_num, 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.
- *
- * This function also handles setting bi_skip_dm_default_key when needed.
- */
- void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode,
- u64 first_lblk, gfp_t gfp_mask)
- {
- const struct fscrypt_info *ci;
- u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
- if (fscrypt_inode_should_skip_dm_default_key(inode))
- bio_set_skip_dm_default_key(bio);
- 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->base, 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 page *page = bh->b_page;
- 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 = page_mapping(page);
- if (!mapping)
- return false;
- inode = mapping->host;
- *inode_ret = inode;
- *lblk_num_ret = ((u64)page->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 also returns false if the next part of the I/O would need to
- * have a different value for the bi_skip_dm_default_key flag.
- *
- * 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 (bio_should_skip_dm_default_key(bio) !=
- fscrypt_inode_should_skip_dm_default_key(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->base)
- 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 &&
- !bio_should_skip_dm_default_key(bio);
- return fscrypt_mergeable_bio(bio, inode, next_lblk);
- }
- EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh);
- /**
- * fscrypt_dio_supported() - check whether a direct I/O request is unsupported
- * due to encryption constraints
- * @iocb: the file and position the I/O is targeting
- * @iter: the I/O data segment(s)
- *
- * Return: true if direct I/O is supported
- */
- bool fscrypt_dio_supported(struct kiocb *iocb, struct iov_iter *iter)
- {
- const struct inode *inode = file_inode(iocb->ki_filp);
- const unsigned int blocksize = i_blocksize(inode);
- /* If the file is unencrypted, no veto from us. */
- if (!fscrypt_needs_contents_encryption(inode))
- return true;
- /* We only support direct I/O with inline crypto, not fs-layer crypto */
- if (!fscrypt_inode_uses_inline_crypto(inode))
- return false;
- /*
- * Since the granularity of encryption is filesystem blocks, the I/O
- * must be block aligned -- not just disk sector aligned.
- */
- if (!IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter), blocksize))
- return false;
- return true;
- }
- 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 @pos
- *
- * Determine the limit to the number of blocks that can be submitted in the bio
- * targeting @pos without causing a data unit number (DUN) discontinuity.
- *
- * 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 continuous 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 the bio.
- *
- * 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_info *ci = inode->i_crypt_info;
- u32 dun;
- if (!fscrypt_inode_uses_inline_crypto(inode))
- return nr_blocks;
- if (nr_blocks <= 1)
- return nr_blocks;
- 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);
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