xref: /openbmc/linux/include/uapi/linux/fsverity.h (revision 07c99001)
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 _UAPI_LINUX_FSVERITY_H
11 #define _UAPI_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 
19 struct 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 
31 struct 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  */
47 struct 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 #ifdef __KERNEL__
53 	__le32 sig_size;
54 #else
55 	__le32 __reserved_0x04;	/* must be 0 */
56 #endif
57 	__le64 data_size;	/* size of file the Merkle tree is built over */
58 	__u8 root_hash[64];	/* Merkle tree root hash */
59 	__u8 salt[32];		/* salt prepended to each hashed block */
60 	__u8 __reserved[144];	/* must be 0's */
61 #ifdef __KERNEL__
62 	__u8 signature[];
63 #endif
64 };
65 
66 /*
67  * Format in which fs-verity file digests are signed in built-in signatures.
68  * This is the same as 'struct fsverity_digest', except here some magic bytes
69  * are prepended to provide some context about what is being signed in case the
70  * same key is used for non-fsverity purposes, and here the fields have fixed
71  * endianness.
72  *
73  * This struct is specific to the built-in signature verification support, which
74  * is optional.  fs-verity users may also verify signatures in userspace, in
75  * which case userspace is responsible for deciding on what bytes are signed.
76  * This struct may still be used, but it doesn't have to be.  For example,
77  * userspace could instead use a string like "sha256:$digest_as_hex_string".
78  */
79 struct fsverity_formatted_digest {
80 	char magic[8];			/* must be "FSVerity" */
81 	__le16 digest_algorithm;
82 	__le16 digest_size;
83 	__u8 digest[];
84 };
85 
86 #define FS_VERITY_METADATA_TYPE_MERKLE_TREE	1
87 #define FS_VERITY_METADATA_TYPE_DESCRIPTOR	2
88 #define FS_VERITY_METADATA_TYPE_SIGNATURE	3
89 
90 struct fsverity_read_metadata_arg {
91 	__u64 metadata_type;
92 	__u64 offset;
93 	__u64 length;
94 	__u64 buf_ptr;
95 	__u64 __reserved;
96 };
97 
98 #define FS_IOC_ENABLE_VERITY	_IOW('f', 133, struct fsverity_enable_arg)
99 #define FS_IOC_MEASURE_VERITY	_IOWR('f', 134, struct fsverity_digest)
100 #define FS_IOC_READ_VERITY_METADATA \
101 	_IOWR('f', 135, struct fsverity_read_metadata_arg)
102 
103 #endif /* _UAPI_LINUX_FSVERITY_H */
104