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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425// 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/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 **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, 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; struct block_device *devs[FSCRYPT_MAX_DEVICES]; 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); crypto_cfg.key_type = is_hw_wrapped_key ? BLK_CRYPTO_KEY_TYPE_HW_WRAPPED : BLK_CRYPTO_KEY_TYPE_RAW;
num_devs = fscrypt_get_devices(sb, devs); for (i = 0; i < num_devs; i++) { if (!blk_crypto_config_supported(devs[i], &crypto_cfg)) return 0; }
fscrypt_log_blk_crypto_impl(ci->ci_mode, devs, num_devs, &crypto_cfg);
ci->ci_inlinecrypt = true;
return 0;}
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; enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_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;
blk_key = kmalloc_obj(*blk_key); if (!blk_key) return -ENOMEM;
err = blk_crypto_init_key(blk_key, key_bytes, key_size, key_type, 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. */ 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; } if (err) { 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;}
bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode){ return fscrypt_get_inode_info_raw(inode)->ci_inlinecrypt;}EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto);
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) 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, loff_t pos, 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 = 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 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, 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_inode_uses_inline_crypto(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_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 = 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);