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This allows platforms that are CPU/memory contrained to verify data blocks only the first time they are read from the data device, rather than every time. As such, it provides a reduced level of security because only offline tampering of the data device's content will be detected, not online tampering. Hash blocks are still verified each time they are read from the hash device, since verification of hash blocks is less performance critical than data blocks, and a hash block will not be verified any more after all the data blocks it covers have been verified anyway. This option introduces a bitset that is used to check if a block has been validated before or not. A block can be validated more than once as there is no thread protection for the bitset. These changes were developed and tested on entry-level Android Go devices. Signed-off-by: Patrik Torstensson <totte@google.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
/*
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* Copyright (C) 2012 Red Hat, Inc.
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* Copyright (C) 2015 Google, Inc.
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*
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* Author: Mikulas Patocka <mpatocka@redhat.com>
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*
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* Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
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*
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* This file is released under the GPLv2.
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*/
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#ifndef DM_VERITY_H
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#define DM_VERITY_H
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#include <linux/dm-bufio.h>
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#include <linux/device-mapper.h>
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#include <crypto/hash.h>
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#define DM_VERITY_MAX_LEVELS 63
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enum verity_mode {
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DM_VERITY_MODE_EIO,
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DM_VERITY_MODE_LOGGING,
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DM_VERITY_MODE_RESTART
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};
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enum verity_block_type {
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DM_VERITY_BLOCK_TYPE_DATA,
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DM_VERITY_BLOCK_TYPE_METADATA
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};
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struct dm_verity_fec;
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struct dm_verity {
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struct dm_dev *data_dev;
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struct dm_dev *hash_dev;
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struct dm_target *ti;
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struct dm_bufio_client *bufio;
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char *alg_name;
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struct crypto_ahash *tfm;
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u8 *root_digest; /* digest of the root block */
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u8 *salt; /* salt: its size is salt_size */
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u8 *zero_digest; /* digest for a zero block */
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unsigned salt_size;
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sector_t data_start; /* data offset in 512-byte sectors */
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sector_t hash_start; /* hash start in blocks */
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sector_t data_blocks; /* the number of data blocks */
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sector_t hash_blocks; /* the number of hash blocks */
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unsigned char data_dev_block_bits; /* log2(data blocksize) */
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unsigned char hash_dev_block_bits; /* log2(hash blocksize) */
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unsigned char hash_per_block_bits; /* log2(hashes in hash block) */
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unsigned char levels; /* the number of tree levels */
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unsigned char version;
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unsigned digest_size; /* digest size for the current hash algorithm */
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unsigned int ahash_reqsize;/* the size of temporary space for crypto */
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int hash_failed; /* set to 1 if hash of any block failed */
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enum verity_mode mode; /* mode for handling verification errors */
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unsigned corrupted_errs;/* Number of errors for corrupted blocks */
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struct workqueue_struct *verify_wq;
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/* starting blocks for each tree level. 0 is the lowest level. */
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sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
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struct dm_verity_fec *fec; /* forward error correction */
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unsigned long *validated_blocks; /* bitset blocks validated */
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};
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struct dm_verity_io {
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struct dm_verity *v;
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/* original value of bio->bi_end_io */
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bio_end_io_t *orig_bi_end_io;
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sector_t block;
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unsigned n_blocks;
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struct bvec_iter iter;
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struct work_struct work;
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/*
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* Three variably-size fields follow this struct:
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*
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* u8 hash_req[v->ahash_reqsize];
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* u8 real_digest[v->digest_size];
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* u8 want_digest[v->digest_size];
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*
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* To access them use: verity_io_hash_req(), verity_io_real_digest()
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* and verity_io_want_digest().
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*/
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};
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static inline struct ahash_request *verity_io_hash_req(struct dm_verity *v,
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struct dm_verity_io *io)
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{
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return (struct ahash_request *)(io + 1);
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}
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static inline u8 *verity_io_real_digest(struct dm_verity *v,
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struct dm_verity_io *io)
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{
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return (u8 *)(io + 1) + v->ahash_reqsize;
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}
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static inline u8 *verity_io_want_digest(struct dm_verity *v,
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struct dm_verity_io *io)
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{
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return (u8 *)(io + 1) + v->ahash_reqsize + v->digest_size;
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}
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static inline u8 *verity_io_digest_end(struct dm_verity *v,
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struct dm_verity_io *io)
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{
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return verity_io_want_digest(v, io) + v->digest_size;
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}
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extern int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
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struct bvec_iter *iter,
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int (*process)(struct dm_verity *v,
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struct dm_verity_io *io,
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u8 *data, size_t len));
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extern int verity_hash(struct dm_verity *v, struct ahash_request *req,
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const u8 *data, size_t len, u8 *digest);
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extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
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sector_t block, u8 *digest, bool *is_zero);
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#endif /* DM_VERITY_H */
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