1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 2/*
 3 * fs-verity user API
 4 *
 5 * These ioctls can be used on filesystems that support fs-verity.  See the
 6 * "User API" section of Documentation/filesystems/fsverity.rst.
 7 *
 8 * Copyright 2019 Google LLC
 9 */
10#ifndef _LINUX_FSVERITY_H
11#define _LINUX_FSVERITY_H
12
13#include <linux/ioctl.h>
14#include <linux/types.h>
15
16#define FS_VERITY_HASH_ALG_SHA256	1
17#define FS_VERITY_HASH_ALG_SHA512	2
18
19struct fsverity_enable_arg {
20	__u32 version;
21	__u32 hash_algorithm;
22	__u32 block_size;
23	__u32 salt_size;
24	__u64 salt_ptr;
25	__u32 sig_size;
26	__u32 __reserved1;
27	__u64 sig_ptr;
28	__u64 __reserved2[11];
29};
30
31struct fsverity_digest {
32	__u16 digest_algorithm;
33	__u16 digest_size; /* input/output */
34	__u8 digest[];
35};
36
37/*
38 * Struct containing a file's Merkle tree properties.  The fs-verity file digest
39 * is the hash of this struct.  A userspace program needs this struct only if it
40 * needs to compute fs-verity file digests itself, e.g. in order to sign files.
41 * It isn't needed just to enable fs-verity on a file.
42 *
43 * Note: when computing the file digest, 'sig_size' and 'signature' must be left
44 * zero and empty, respectively.  These fields are present only because some
45 * filesystems reuse this struct as part of their on-disk format.
46 */
47struct fsverity_descriptor {
48	__u8 version;		/* must be 1 */
49	__u8 hash_algorithm;	/* Merkle tree hash algorithm */
50	__u8 log_blocksize;	/* log2 of size of data and tree blocks */
51	__u8 salt_size;		/* size of salt in bytes; 0 if none */
52	__le32 __reserved_0x04;	/* must be 0 */
53	__le64 data_size;	/* size of file the Merkle tree is built over */
54	__u8 root_hash[64];	/* Merkle tree root hash */
55	__u8 salt[32];		/* salt prepended to each hashed block */
56	__u8 __reserved[144];	/* must be 0's */
57};
58
59/*
60 * Format in which fs-verity file digests are signed in built-in signatures.
61 * This is the same as 'struct fsverity_digest', except here some magic bytes
62 * are prepended to provide some context about what is being signed in case the
63 * same key is used for non-fsverity purposes, and here the fields have fixed
64 * endianness.
65 *
66 * This struct is specific to the built-in signature verification support, which
67 * is optional.  fs-verity users may also verify signatures in userspace, in
68 * which case userspace is responsible for deciding on what bytes are signed.
69 * This struct may still be used, but it doesn't have to be.  For example,
70 * userspace could instead use a string like "sha256:$digest_as_hex_string".
71 */
72struct fsverity_formatted_digest {
73	char magic[8];			/* must be "FSVerity" */
74	__le16 digest_algorithm;
75	__le16 digest_size;
76	__u8 digest[];
77};
78
79#define FS_VERITY_METADATA_TYPE_MERKLE_TREE	1
80#define FS_VERITY_METADATA_TYPE_DESCRIPTOR	2
81#define FS_VERITY_METADATA_TYPE_SIGNATURE	3
82
83struct fsverity_read_metadata_arg {
84	__u64 metadata_type;
85	__u64 offset;
86	__u64 length;
87	__u64 buf_ptr;
88	__u64 __reserved;
89};
90
91#define FS_IOC_ENABLE_VERITY	_IOW('f', 133, struct fsverity_enable_arg)
92#define FS_IOC_MEASURE_VERITY	_IOWR('f', 134, struct fsverity_digest)
93#define FS_IOC_READ_VERITY_METADATA \
94	_IOWR('f', 135, struct fsverity_read_metadata_arg)
95
96#endif /* _LINUX_FSVERITY_H */