fsverity.h

  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
 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#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 */
 79struct 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
 90struct 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 */