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365 lines
11 KiB
365 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Inline encryption support for fscrypt |
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* |
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* Copyright 2019 Google LLC |
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*/ |
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/* |
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* With "inline encryption", the block layer handles the decryption/encryption |
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* as part of the bio, instead of the filesystem doing the crypto itself via |
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* crypto API. See Documentation/block/inline-encryption.rst. fscrypt still |
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* provides the key and IV to use. |
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*/ |
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#include <linux/blk-crypto.h> |
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#include <linux/blkdev.h> |
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#include <linux/buffer_head.h> |
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#include <linux/sched/mm.h> |
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#include <linux/slab.h> |
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#include "fscrypt_private.h" |
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struct fscrypt_blk_crypto_key { |
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struct blk_crypto_key base; |
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int num_devs; |
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struct request_queue *devs[]; |
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}; |
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static int fscrypt_get_num_devices(struct super_block *sb) |
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{ |
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if (sb->s_cop->get_num_devices) |
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return sb->s_cop->get_num_devices(sb); |
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return 1; |
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} |
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static void fscrypt_get_devices(struct super_block *sb, int num_devs, |
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struct request_queue **devs) |
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{ |
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if (num_devs == 1) |
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devs[0] = bdev_get_queue(sb->s_bdev); |
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else |
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sb->s_cop->get_devices(sb, devs); |
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} |
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static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_info *ci) |
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{ |
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struct super_block *sb = ci->ci_inode->i_sb; |
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unsigned int flags = fscrypt_policy_flags(&ci->ci_policy); |
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int ino_bits = 64, lblk_bits = 64; |
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if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) |
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return offsetofend(union fscrypt_iv, nonce); |
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if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) |
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return sizeof(__le64); |
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if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) |
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return sizeof(__le32); |
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/* Default case: IVs are just the file logical block number */ |
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if (sb->s_cop->get_ino_and_lblk_bits) |
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sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits); |
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return DIV_ROUND_UP(lblk_bits, 8); |
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} |
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/* Enable inline encryption for this file if supported. */ |
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int fscrypt_select_encryption_impl(struct fscrypt_info *ci) |
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{ |
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const struct inode *inode = ci->ci_inode; |
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struct super_block *sb = inode->i_sb; |
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struct blk_crypto_config crypto_cfg; |
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int num_devs; |
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struct request_queue **devs; |
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int i; |
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/* The file must need contents encryption, not filenames encryption */ |
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if (!S_ISREG(inode->i_mode)) |
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return 0; |
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/* The crypto mode must have a blk-crypto counterpart */ |
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if (ci->ci_mode->blk_crypto_mode == BLK_ENCRYPTION_MODE_INVALID) |
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return 0; |
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/* The filesystem must be mounted with -o inlinecrypt */ |
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if (!(sb->s_flags & SB_INLINECRYPT)) |
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return 0; |
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/* |
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* When a page contains multiple logically contiguous filesystem blocks, |
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* some filesystem code only calls fscrypt_mergeable_bio() for the first |
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* block in the page. This is fine for most of fscrypt's IV generation |
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* strategies, where contiguous blocks imply contiguous IVs. But it |
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* doesn't work with IV_INO_LBLK_32. For now, simply exclude |
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* IV_INO_LBLK_32 with blocksize != PAGE_SIZE from inline encryption. |
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*/ |
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if ((fscrypt_policy_flags(&ci->ci_policy) & |
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FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) && |
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sb->s_blocksize != PAGE_SIZE) |
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return 0; |
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/* |
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* On all the filesystem's devices, blk-crypto must support the crypto |
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* configuration that the file would use. |
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*/ |
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crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode; |
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crypto_cfg.data_unit_size = sb->s_blocksize; |
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crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci); |
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num_devs = fscrypt_get_num_devices(sb); |
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devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL); |
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if (!devs) |
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return -ENOMEM; |
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fscrypt_get_devices(sb, num_devs, devs); |
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for (i = 0; i < num_devs; i++) { |
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if (!blk_crypto_config_supported(devs[i], &crypto_cfg)) |
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goto out_free_devs; |
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} |
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ci->ci_inlinecrypt = true; |
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out_free_devs: |
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kfree(devs); |
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return 0; |
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} |
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int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key, |
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const u8 *raw_key, |
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const struct fscrypt_info *ci) |
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{ |
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const struct inode *inode = ci->ci_inode; |
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struct super_block *sb = inode->i_sb; |
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enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode; |
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int num_devs = fscrypt_get_num_devices(sb); |
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int queue_refs = 0; |
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struct fscrypt_blk_crypto_key *blk_key; |
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int err; |
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int i; |
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blk_key = kzalloc(struct_size(blk_key, devs, num_devs), GFP_KERNEL); |
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if (!blk_key) |
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return -ENOMEM; |
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blk_key->num_devs = num_devs; |
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fscrypt_get_devices(sb, num_devs, blk_key->devs); |
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err = blk_crypto_init_key(&blk_key->base, raw_key, crypto_mode, |
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fscrypt_get_dun_bytes(ci), sb->s_blocksize); |
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if (err) { |
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fscrypt_err(inode, "error %d initializing blk-crypto key", err); |
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goto fail; |
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} |
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/* |
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* We have to start using blk-crypto on all the filesystem's devices. |
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* We also have to save all the request_queue's for later so that the |
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* key can be evicted from them. This is needed because some keys |
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* aren't destroyed until after the filesystem was already unmounted |
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* (namely, the per-mode keys in struct fscrypt_master_key). |
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*/ |
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for (i = 0; i < num_devs; i++) { |
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if (!blk_get_queue(blk_key->devs[i])) { |
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fscrypt_err(inode, "couldn't get request_queue"); |
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err = -EAGAIN; |
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goto fail; |
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} |
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queue_refs++; |
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err = blk_crypto_start_using_key(&blk_key->base, |
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blk_key->devs[i]); |
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if (err) { |
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fscrypt_err(inode, |
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"error %d starting to use blk-crypto", err); |
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goto fail; |
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} |
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} |
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/* |
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* Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). |
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* I.e., here we publish ->blk_key with a RELEASE barrier so that |
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* concurrent tasks can ACQUIRE it. Note that this concurrency is only |
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* possible for per-mode keys, not for per-file keys. |
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*/ |
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smp_store_release(&prep_key->blk_key, blk_key); |
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return 0; |
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fail: |
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for (i = 0; i < queue_refs; i++) |
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blk_put_queue(blk_key->devs[i]); |
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kfree_sensitive(blk_key); |
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return err; |
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} |
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void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key) |
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{ |
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struct fscrypt_blk_crypto_key *blk_key = prep_key->blk_key; |
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int i; |
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if (blk_key) { |
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for (i = 0; i < blk_key->num_devs; i++) { |
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blk_crypto_evict_key(blk_key->devs[i], &blk_key->base); |
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blk_put_queue(blk_key->devs[i]); |
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} |
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kfree_sensitive(blk_key); |
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} |
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} |
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bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode) |
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{ |
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return inode->i_crypt_info->ci_inlinecrypt; |
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} |
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EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto); |
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static void fscrypt_generate_dun(const struct fscrypt_info *ci, u64 lblk_num, |
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u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]) |
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{ |
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union fscrypt_iv iv; |
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int i; |
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fscrypt_generate_iv(&iv, lblk_num, ci); |
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BUILD_BUG_ON(FSCRYPT_MAX_IV_SIZE > BLK_CRYPTO_MAX_IV_SIZE); |
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memset(dun, 0, BLK_CRYPTO_MAX_IV_SIZE); |
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for (i = 0; i < ci->ci_mode->ivsize/sizeof(dun[0]); i++) |
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dun[i] = le64_to_cpu(iv.dun[i]); |
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} |
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/** |
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* fscrypt_set_bio_crypt_ctx() - prepare a file contents bio for inline crypto |
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* @bio: a bio which will eventually be submitted to the file |
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* @inode: the file's inode |
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* @first_lblk: the first file logical block number in the I/O |
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* @gfp_mask: memory allocation flags - these must be a waiting mask so that |
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* bio_crypt_set_ctx can't fail. |
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* |
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* If the contents of the file should be encrypted (or decrypted) with inline |
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* encryption, then assign the appropriate encryption context to the bio. |
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* |
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* Normally the bio should be newly allocated (i.e. no pages added yet), as |
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* otherwise fscrypt_mergeable_bio() won't work as intended. |
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* |
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* The encryption context will be freed automatically when the bio is freed. |
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*/ |
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void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode, |
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u64 first_lblk, gfp_t gfp_mask) |
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{ |
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const struct fscrypt_info *ci; |
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u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; |
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if (!fscrypt_inode_uses_inline_crypto(inode)) |
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return; |
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ci = inode->i_crypt_info; |
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fscrypt_generate_dun(ci, first_lblk, dun); |
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bio_crypt_set_ctx(bio, &ci->ci_enc_key.blk_key->base, dun, gfp_mask); |
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} |
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EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx); |
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/* Extract the inode and logical block number from a buffer_head. */ |
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static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh, |
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const struct inode **inode_ret, |
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u64 *lblk_num_ret) |
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{ |
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struct page *page = bh->b_page; |
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const struct address_space *mapping; |
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const struct inode *inode; |
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/* |
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* The ext4 journal (jbd2) can submit a buffer_head it directly created |
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* for a non-pagecache page. fscrypt doesn't care about these. |
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*/ |
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mapping = page_mapping(page); |
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if (!mapping) |
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return false; |
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inode = mapping->host; |
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*inode_ret = inode; |
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*lblk_num_ret = ((u64)page->index << (PAGE_SHIFT - inode->i_blkbits)) + |
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(bh_offset(bh) >> inode->i_blkbits); |
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return true; |
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} |
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/** |
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* fscrypt_set_bio_crypt_ctx_bh() - prepare a file contents bio for inline |
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* crypto |
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* @bio: a bio which will eventually be submitted to the file |
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* @first_bh: the first buffer_head for which I/O will be submitted |
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* @gfp_mask: memory allocation flags |
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* |
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* Same as fscrypt_set_bio_crypt_ctx(), except this takes a buffer_head instead |
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* of an inode and block number directly. |
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*/ |
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void fscrypt_set_bio_crypt_ctx_bh(struct bio *bio, |
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const struct buffer_head *first_bh, |
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gfp_t gfp_mask) |
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{ |
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const struct inode *inode; |
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u64 first_lblk; |
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if (bh_get_inode_and_lblk_num(first_bh, &inode, &first_lblk)) |
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fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk, gfp_mask); |
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} |
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EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh); |
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/** |
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* fscrypt_mergeable_bio() - test whether data can be added to a bio |
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* @bio: the bio being built up |
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* @inode: the inode for the next part of the I/O |
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* @next_lblk: the next file logical block number in the I/O |
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* |
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* When building a bio which may contain data which should undergo inline |
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* encryption (or decryption) via fscrypt, filesystems should call this function |
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* to ensure that the resulting bio contains only contiguous data unit numbers. |
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* This will return false if the next part of the I/O cannot be merged with the |
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* bio because either the encryption key would be different or the encryption |
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* data unit numbers would be discontiguous. |
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* |
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* fscrypt_set_bio_crypt_ctx() must have already been called on the bio. |
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* |
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* Return: true iff the I/O is mergeable |
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*/ |
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bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode, |
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u64 next_lblk) |
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{ |
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const struct bio_crypt_ctx *bc = bio->bi_crypt_context; |
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u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; |
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if (!!bc != fscrypt_inode_uses_inline_crypto(inode)) |
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return false; |
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if (!bc) |
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return true; |
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/* |
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* Comparing the key pointers is good enough, as all I/O for each key |
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* uses the same pointer. I.e., there's currently no need to support |
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* merging requests where the keys are the same but the pointers differ. |
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*/ |
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if (bc->bc_key != &inode->i_crypt_info->ci_enc_key.blk_key->base) |
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return false; |
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fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun); |
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return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun); |
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} |
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EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio); |
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/** |
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* fscrypt_mergeable_bio_bh() - test whether data can be added to a bio |
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* @bio: the bio being built up |
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* @next_bh: the next buffer_head for which I/O will be submitted |
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* |
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* Same as fscrypt_mergeable_bio(), except this takes a buffer_head instead of |
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* an inode and block number directly. |
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* |
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* Return: true iff the I/O is mergeable |
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*/ |
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bool fscrypt_mergeable_bio_bh(struct bio *bio, |
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const struct buffer_head *next_bh) |
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{ |
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const struct inode *inode; |
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u64 next_lblk; |
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if (!bh_get_inode_and_lblk_num(next_bh, &inode, &next_lblk)) |
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return !bio->bi_crypt_context; |
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return fscrypt_mergeable_bio(bio, inode, next_lblk); |
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} |
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EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh);
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