// 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 "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) { 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); 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, 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); err = blk_crypto_init_key(&blk_key->base, raw_key, 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); } } 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. */ 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_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. * * 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->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; return fscrypt_mergeable_bio(bio, inode, next_lblk); } EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh);