Although it isn't used directly by the ioctls,
"struct fsverity_descriptor" is required by userspace programs that need
to compute fs-verity file digests in a standalone way. Therefore
it's also needed to sign files in a standalone way.
Similarly, "struct fsverity_formatted_digest" (previously called
"struct fsverity_signed_digest" which was misleading) is also needed to
sign files if the built-in signature verification is being used.
Therefore, move these structs to the UAPI header.
While doing this, try to make it clear that the signature-related fields
in fsverity_descriptor aren't used in the file digest computation.
Acked-by: Luca Boccassi <luca.boccassi@microsoft.com>
Link: https://lore.kernel.org/r/20201113211918.71883-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
__u8 hash_algorithm; /* Merkle tree hash algorithm */
__u8 log_blocksize; /* log2 of size of data and tree blocks */
__u8 salt_size; /* size of salt in bytes; 0 if none */
- __le32 sig_size; /* must be 0 */
+ __le32 __reserved_0x04; /* must be 0 */
__le64 data_size; /* size of file the Merkle tree is built over */
__u8 root_hash[64]; /* Merkle tree root hash */
__u8 salt[32]; /* salt prepended to each hashed block */
__u8 __reserved[144]; /* must be 0's */
};
-Note that the ``sig_size`` field must be set to 0 for the purpose of
-computing the file measurement, even if a signature was provided (or
-will be provided) to `FS_IOC_ENABLE_VERITY`_.
-
Built-in signature verification
===============================
const struct inode *inode;
};
-/*
- * Merkle tree properties. The fs-verity file digest is the hash of this
- * structure excluding the signature and with the sig_size field set to 0.
- */
-struct fsverity_descriptor {
- __u8 version; /* must be 1 */
- __u8 hash_algorithm; /* Merkle tree hash algorithm */
- __u8 log_blocksize; /* log2 of size of data and tree blocks */
- __u8 salt_size; /* size of salt in bytes; 0 if none */
- __le32 sig_size; /* size of signature in bytes; 0 if none */
- __le64 data_size; /* size of file the Merkle tree is built over */
- __u8 root_hash[64]; /* Merkle tree root hash */
- __u8 salt[32]; /* salt prepended to each hashed block */
- __u8 __reserved[144]; /* must be 0's */
- __u8 signature[]; /* optional PKCS#7 signature */
-};
-
/* Arbitrary limit to bound the kmalloc() size. Can be changed. */
#define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384
#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
sizeof(struct fsverity_descriptor))
-/*
- * Format in which fs-verity file digests are signed in built-in signatures.
- * This is the same as 'struct fsverity_digest', except here some magic bytes
- * are prepended to provide some context about what is being signed in case the
- * same key is used for non-fsverity purposes, and here the fields have fixed
- * endianness.
- *
- * This struct is specific to the built-in signature verification support, which
- * is optional. fs-verity users may also verify signatures in userspace, in
- * which case userspace is responsible for deciding on what bytes are signed.
- * This struct may still be used, but it doesn't have to be. For example,
- * userspace could instead use a string like "sha256:$digest_as_hex_string".
- */
-struct fsverity_formatted_digest {
- char magic[8]; /* must be "FSVerity" */
- __le16 digest_algorithm;
- __le16 digest_size;
- __u8 digest[];
-};
-
/* hash_algs.c */
extern struct fsverity_hash_alg fsverity_hash_algs[];
__u8 digest[];
};
+/*
+ * Struct containing a file's Merkle tree properties. The fs-verity file digest
+ * is the hash of this struct. A userspace program needs this struct only if it
+ * needs to compute fs-verity file digests itself, e.g. in order to sign files.
+ * It isn't needed just to enable fs-verity on a file.
+ *
+ * Note: when computing the file digest, 'sig_size' and 'signature' must be left
+ * zero and empty, respectively. These fields are present only because some
+ * filesystems reuse this struct as part of their on-disk format.
+ */
+struct fsverity_descriptor {
+ __u8 version; /* must be 1 */
+ __u8 hash_algorithm; /* Merkle tree hash algorithm */
+ __u8 log_blocksize; /* log2 of size of data and tree blocks */
+ __u8 salt_size; /* size of salt in bytes; 0 if none */
+#ifdef __KERNEL__
+ __le32 sig_size;
+#else
+ __le32 __reserved_0x04; /* must be 0 */
+#endif
+ __le64 data_size; /* size of file the Merkle tree is built over */
+ __u8 root_hash[64]; /* Merkle tree root hash */
+ __u8 salt[32]; /* salt prepended to each hashed block */
+ __u8 __reserved[144]; /* must be 0's */
+#ifdef __KERNEL__
+ __u8 signature[];
+#endif
+};
+
+/*
+ * Format in which fs-verity file digests are signed in built-in signatures.
+ * This is the same as 'struct fsverity_digest', except here some magic bytes
+ * are prepended to provide some context about what is being signed in case the
+ * same key is used for non-fsverity purposes, and here the fields have fixed
+ * endianness.
+ *
+ * This struct is specific to the built-in signature verification support, which
+ * is optional. fs-verity users may also verify signatures in userspace, in
+ * which case userspace is responsible for deciding on what bytes are signed.
+ * This struct may still be used, but it doesn't have to be. For example,
+ * userspace could instead use a string like "sha256:$digest_as_hex_string".
+ */
+struct fsverity_formatted_digest {
+ char magic[8]; /* must be "FSVerity" */
+ __le16 digest_algorithm;
+ __le16 digest_size;
+ __u8 digest[];
+};
+
#define FS_IOC_ENABLE_VERITY _IOW('f', 133, struct fsverity_enable_arg)
#define FS_IOC_MEASURE_VERITY _IOWR('f', 134, struct fsverity_digest)
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