include/uapi/linux/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
  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 */