This patchset renames some names that have been causing confusion:
- fsverity_signed_digest is renamed to fsverity_formatted_digest
- "fs-verity file measurement" is renamed to "fs-verity file digest"
In addition, this patchset moves fsverity_descriptor and
fsverity_formatted_digest to the UAPI header because userspace programs
may need them in order to sign files.
Eric Biggers (4):
fs-verity: remove filenames from file comments
fs-verity: rename fsverity_signed_digest to fsverity_formatted_digest
fs-verity: rename "file measurement" to "file digest"
fs-verity: move structs needed for file signing to UAPI header
Documentation/filesystems/fsverity.rst | 68 ++++++++++++--------------
fs/verity/enable.c | 8 +--
fs/verity/fsverity_private.h | 36 ++------------
fs/verity/hash_algs.c | 2 +-
fs/verity/init.c | 2 +-
fs/verity/measure.c | 12 ++---
fs/verity/open.c | 24 ++++-----
fs/verity/signature.c | 14 +++---
fs/verity/verify.c | 2 +-
include/uapi/linux/fsverity.h | 49 +++++++++++++++++++
10 files changed, 116 insertions(+), 101 deletions(-)
--
2.29.2
From: Eric Biggers <[email protected]>
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.
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/filesystems/fsverity.rst | 6 +---
fs/verity/fsverity_private.h | 37 -------------------
include/uapi/linux/fsverity.h | 49 ++++++++++++++++++++++++++
3 files changed, 50 insertions(+), 42 deletions(-)
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 2eee558b7f5ff..e0204a23e997e 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -334,17 +334,13 @@ root hash as well as other fields such as the file size::
__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
===============================
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index 21e9930d65fbd..96f7b332f54f5 100644
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -77,49 +77,12 @@ struct fsverity_info {
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[];
diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h
index da0daf6c193b4..260017a4b44b3 100644
--- a/include/uapi/linux/fsverity.h
+++ b/include/uapi/linux/fsverity.h
@@ -34,6 +34,55 @@ struct fsverity_digest {
__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;
+#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)
--
2.29.2
From: Eric Biggers <[email protected]>
I originally chose the name "file measurement" to refer to the fs-verity
file digest to avoid confusion with traditional full-file digests or
with the bare root hash of the Merkle tree.
But the name "file measurement" hasn't caught on, and usually people are
calling it something else, usually the "file digest". E.g. see
"struct fsverity_digest" and "struct fsverity_formatted_digest", the
libfsverity_compute_digest() and libfsverity_sign_digest() functions in
libfsverity, and the "fsverity digest" command.
Having multiple names for the same thing is always confusing.
So to hopefully avoid confusion in the future, rename
"fs-verity file measurement" to "fs-verity file digest".
This leaves FS_IOC_MEASURE_VERITY as the only reference to "measure" in
the kernel, which makes some amount of sense since the ioctl is actively
"measuring" the file.
I'll be renaming this in fsverity-utils too (though similarly the
'fsverity measure' command, which is a wrapper for
FS_IOC_MEASURE_VERITY, will stay).
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/filesystems/fsverity.rst | 60 +++++++++++++-------------
fs/verity/enable.c | 6 +--
fs/verity/fsverity_private.h | 12 +++---
fs/verity/measure.c | 12 +++---
fs/verity/open.c | 22 +++++-----
fs/verity/signature.c | 10 ++---
6 files changed, 61 insertions(+), 61 deletions(-)
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 421b75498d49b..2eee558b7f5ff 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -27,9 +27,9 @@ automatically verified against the file's Merkle tree. Reads of any
corrupted data, including mmap reads, will fail.
Userspace can use another ioctl to retrieve the root hash (actually
-the "file measurement", which is a hash that includes the root hash)
-that fs-verity is enforcing for the file. This ioctl executes in
-constant time, regardless of the file size.
+the "fs-verity file digest", which is a hash that includes the Merkle
+tree root hash) that fs-verity is enforcing for the file. This ioctl
+executes in constant time, regardless of the file size.
fs-verity is essentially a way to hash a file in constant time,
subject to the caveat that reads which would violate the hash will
@@ -177,9 +177,10 @@ FS_IOC_ENABLE_VERITY can fail with the following errors:
FS_IOC_MEASURE_VERITY
---------------------
-The FS_IOC_MEASURE_VERITY ioctl retrieves the measurement of a verity
-file. The file measurement is a digest that cryptographically
-identifies the file contents that are being enforced on reads.
+The FS_IOC_MEASURE_VERITY ioctl retrieves the digest of a verity file.
+The fs-verity file digest is a cryptographic digest that identifies
+the file contents that are being enforced on reads; it is computed via
+a Merkle tree and is different from a traditional full-file digest.
This ioctl takes in a pointer to a variable-length structure::
@@ -197,7 +198,7 @@ On success, 0 is returned and the kernel fills in the structure as
follows:
- ``digest_algorithm`` will be the hash algorithm used for the file
- measurement. It will match ``fsverity_enable_arg::hash_algorithm``.
+ digest. It will match ``fsverity_enable_arg::hash_algorithm``.
- ``digest_size`` will be the size of the digest in bytes, e.g. 32
for SHA-256. (This can be redundant with ``digest_algorithm``.)
- ``digest`` will be the actual bytes of the digest.
@@ -257,25 +258,24 @@ non-verity one, with the following exceptions:
with EIO (for read()) or SIGBUS (for mmap() reads).
- If the sysctl "fs.verity.require_signatures" is set to 1 and the
- file's verity measurement is not signed by a key in the fs-verity
- keyring, then opening the file will fail. See `Built-in signature
- verification`_.
+ file is not signed by a key in the fs-verity keyring, then opening
+ the file will fail. See `Built-in signature verification`_.
Direct access to the Merkle tree is not supported. Therefore, if a
verity file is copied, or is backed up and restored, then it will lose
its "verity"-ness. fs-verity is primarily meant for files like
executables that are managed by a package manager.
-File measurement computation
-============================
+File digest computation
+=======================
This section describes how fs-verity hashes the file contents using a
-Merkle tree to produce the "file measurement" which cryptographically
-identifies the file contents. This algorithm is the same for all
-filesystems that support fs-verity.
+Merkle tree to produce the digest which cryptographically identifies
+the file contents. This algorithm is the same for all filesystems
+that support fs-verity.
Userspace only needs to be aware of this algorithm if it needs to
-compute the file measurement itself, e.g. in order to sign the file.
+compute fs-verity file digests itself, e.g. in order to sign files.
.. _fsverity_merkle_tree:
@@ -325,9 +325,9 @@ can't a distinguish a large file from a small second file whose data
is exactly the top-level hash block of the first file. Ambiguities
also arise from the convention of padding to the next block boundary.
-To solve this problem, the verity file measurement is actually
-computed as a hash of the following structure, which contains the
-Merkle tree root hash as well as other fields such as the file size::
+To solve this problem, the fs-verity file digest is actually computed
+as a hash of the following structure, which contains the Merkle tree
+root hash as well as other fields such as the file size::
struct fsverity_descriptor {
__u8 version; /* must be 1 */
@@ -359,18 +359,18 @@ kernel. Specifically, it adds support for:
certificates from being added.
2. `FS_IOC_ENABLE_VERITY`_ accepts a pointer to a PKCS#7 formatted
- detached signature in DER format of the file measurement. On
- success, this signature is persisted alongside the Merkle tree.
+ detached signature in DER format of the file's fs-verity digest.
+ On success, this signature is persisted alongside the Merkle tree.
Then, any time the file is opened, the kernel will verify the
- file's actual measurement against this signature, using the
- certificates in the ".fs-verity" keyring.
+ file's actual digest against this signature, using the certificates
+ in the ".fs-verity" keyring.
3. A new sysctl "fs.verity.require_signatures" is made available.
When set to 1, the kernel requires that all verity files have a
- correctly signed file measurement as described in (2).
+ correctly signed digest as described in (2).
-File measurements must be signed in the following format, which is
-similar to the structure used by `FS_IOC_MEASURE_VERITY`_::
+fs-verity file digests must be signed in the following format, which
+is similar to the structure used by `FS_IOC_MEASURE_VERITY`_::
struct fsverity_formatted_digest {
char magic[8]; /* must be "FSVerity" */
@@ -421,8 +421,8 @@ can only be set by `FS_IOC_ENABLE_VERITY`_, and it cannot be cleared.
ext4 also supports encryption, which can be used simultaneously with
fs-verity. In this case, the plaintext data is verified rather than
-the ciphertext. This is necessary in order to make the file
-measurement meaningful, since every file is encrypted differently.
+the ciphertext. This is necessary in order to make the fs-verity file
+digest meaningful, since every file is encrypted differently.
ext4 stores the verity metadata (Merkle tree and fsverity_descriptor)
past the end of the file, starting at the first 64K boundary beyond
@@ -592,8 +592,8 @@ weren't already directly answered in other parts of this document.
:Q: Isn't fs-verity useless because the attacker can just modify the
hashes in the Merkle tree, which is stored on-disk?
:A: To verify the authenticity of an fs-verity file you must verify
- the authenticity of the "file measurement", which is basically the
- root hash of the Merkle tree. See `Use cases`_.
+ the authenticity of the "fs-verity file digest", which
+ incorporates the root hash of the Merkle tree. See `Use cases`_.
:Q: Isn't fs-verity useless because the attacker can just replace a
verity file with a non-verity one?
diff --git a/fs/verity/enable.c b/fs/verity/enable.c
index 9c5b28c865226..f7e997a01ad07 100644
--- a/fs/verity/enable.c
+++ b/fs/verity/enable.c
@@ -398,9 +398,9 @@ int fsverity_ioctl_enable(struct file *filp, const void __user *uarg)
* Some pages of the file may have been evicted from pagecache after
* being used in the Merkle tree construction, then read into pagecache
* again by another process reading from the file concurrently. Since
- * these pages didn't undergo verification against the file measurement
- * which fs-verity now claims to be enforcing, we have to wipe the
- * pagecache to ensure that all future reads are verified.
+ * these pages didn't undergo verification against the file digest which
+ * fs-verity now claims to be enforcing, we have to wipe the pagecache
+ * to ensure that all future reads are verified.
*/
filemap_write_and_wait(inode->i_mapping);
invalidate_inode_pages2(inode->i_mapping);
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index 75f8e18b44a5b..21e9930d65fbd 100644
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -67,19 +67,19 @@ struct merkle_tree_params {
* When a verity file is first opened, an instance of this struct is allocated
* and stored in ->i_verity_info; it remains until the inode is evicted. It
* caches information about the Merkle tree that's needed to efficiently verify
- * data read from the file. It also caches the file measurement. The Merkle
- * tree pages themselves are not cached here, but the filesystem may cache them.
+ * data read from the file. It also caches the file digest. The Merkle tree
+ * pages themselves are not cached here, but the filesystem may cache them.
*/
struct fsverity_info {
struct merkle_tree_params tree_params;
u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
- u8 measurement[FS_VERITY_MAX_DIGEST_SIZE];
+ u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
const struct inode *inode;
};
/*
- * Merkle tree properties. The file measurement is the hash of this structure
- * excluding the signature and with the sig_size field set to 0.
+ * 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 */
@@ -101,7 +101,7 @@ struct fsverity_descriptor {
sizeof(struct fsverity_descriptor))
/*
- * Format in which verity file measurements are signed in built-in signatures.
+ * 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
diff --git a/fs/verity/measure.c b/fs/verity/measure.c
index 5300b8d385376..f0d7b30c62db2 100644
--- a/fs/verity/measure.c
+++ b/fs/verity/measure.c
@@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
/*
- * Ioctl to get a verity file's measurement
+ * Ioctl to get a verity file's digest
*
* Copyright 2019 Google LLC
*/
@@ -10,12 +10,12 @@
#include <linux/uaccess.h>
/**
- * fsverity_ioctl_measure() - get a verity file's measurement
- * @filp: file to get measurement of
+ * fsverity_ioctl_measure() - get a verity file's digest
+ * @filp: file to get digest of
* @_uarg: user pointer to fsverity_digest
*
- * Retrieve the file measurement that the kernel is enforcing for reads from a
- * verity file. See the "FS_IOC_MEASURE_VERITY" section of
+ * Retrieve the file digest that the kernel is enforcing for reads from a verity
+ * file. See the "FS_IOC_MEASURE_VERITY" section of
* Documentation/filesystems/fsverity.rst for the documentation.
*
* Return: 0 on success, -errno on failure
@@ -51,7 +51,7 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
if (copy_to_user(uarg, &arg, sizeof(arg)))
return -EFAULT;
- if (copy_to_user(uarg->digest, vi->measurement, hash_alg->digest_size))
+ if (copy_to_user(uarg->digest, vi->file_digest, hash_alg->digest_size))
return -EFAULT;
return 0;
diff --git a/fs/verity/open.c b/fs/verity/open.c
index a28d5be78a09c..228d0eca3e2e5 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -124,18 +124,18 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
}
/*
- * Compute the file measurement by hashing the fsverity_descriptor excluding the
+ * Compute the file digest by hashing the fsverity_descriptor excluding the
* signature and with the sig_size field set to 0.
*/
-static int compute_file_measurement(struct fsverity_hash_alg *hash_alg,
- struct fsverity_descriptor *desc,
- u8 *measurement)
+static int compute_file_digest(struct fsverity_hash_alg *hash_alg,
+ struct fsverity_descriptor *desc,
+ u8 *file_digest)
{
__le32 sig_size = desc->sig_size;
int err;
desc->sig_size = 0;
- err = fsverity_hash_buffer(hash_alg, desc, sizeof(*desc), measurement);
+ err = fsverity_hash_buffer(hash_alg, desc, sizeof(*desc), file_digest);
desc->sig_size = sig_size;
return err;
@@ -199,15 +199,15 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode,
memcpy(vi->root_hash, desc->root_hash, vi->tree_params.digest_size);
- err = compute_file_measurement(vi->tree_params.hash_alg, desc,
- vi->measurement);
+ err = compute_file_digest(vi->tree_params.hash_alg, desc,
+ vi->file_digest);
if (err) {
- fsverity_err(inode, "Error %d computing file measurement", err);
+ fsverity_err(inode, "Error %d computing file digest", err);
goto out;
}
- pr_debug("Computed file measurement: %s:%*phN\n",
+ pr_debug("Computed file digest: %s:%*phN\n",
vi->tree_params.hash_alg->name,
- vi->tree_params.digest_size, vi->measurement);
+ vi->tree_params.digest_size, vi->file_digest);
err = fsverity_verify_signature(vi, desc, desc_size);
out:
@@ -354,7 +354,7 @@ int __init fsverity_init_info_cache(void)
{
fsverity_info_cachep = KMEM_CACHE_USERCOPY(fsverity_info,
SLAB_RECLAIM_ACCOUNT,
- measurement);
+ file_digest);
if (!fsverity_info_cachep)
return -ENOMEM;
return 0;
diff --git a/fs/verity/signature.c b/fs/verity/signature.c
index 74ae10f04d215..012468eda2a78 100644
--- a/fs/verity/signature.c
+++ b/fs/verity/signature.c
@@ -32,8 +32,8 @@ static struct key *fsverity_keyring;
* @desc: the file's fsverity_descriptor
* @desc_size: size of @desc
*
- * If the file's fs-verity descriptor includes a signature of the file
- * measurement, verify it against the certificates in the fs-verity keyring.
+ * If the file's fs-verity descriptor includes a signature of the file digest,
+ * verify it against the certificates in the fs-verity keyring.
*
* Return: 0 on success (signature valid or not required); -errno on failure
*/
@@ -67,7 +67,7 @@ int fsverity_verify_signature(const struct fsverity_info *vi,
memcpy(d->magic, "FSVerity", 8);
d->digest_algorithm = cpu_to_le16(hash_alg - fsverity_hash_algs);
d->digest_size = cpu_to_le16(hash_alg->digest_size);
- memcpy(d->digest, vi->measurement, hash_alg->digest_size);
+ memcpy(d->digest, vi->file_digest, hash_alg->digest_size);
err = verify_pkcs7_signature(d, sizeof(*d) + hash_alg->digest_size,
desc->signature, sig_size,
@@ -90,8 +90,8 @@ int fsverity_verify_signature(const struct fsverity_info *vi,
return err;
}
- pr_debug("Valid signature for file measurement %s:%*phN\n",
- hash_alg->name, hash_alg->digest_size, vi->measurement);
+ pr_debug("Valid signature for file digest %s:%*phN\n",
+ hash_alg->name, hash_alg->digest_size, vi->file_digest);
return 0;
}
--
2.29.2
From: Eric Biggers <[email protected]>
The name "struct fsverity_signed_digest" is causing confusion because it
isn't actually a signed digest, but rather it's the way that the digest
is formatted in order to be signed. Rename it to
"struct fsverity_formatted_digest" to prevent this confusion.
Also update the struct's comment to clarify that it's specific to the
built-in signature verification support and isn't a requirement for all
fs-verity users.
I'll be renaming this struct in fsverity-utils too.
Acked-by: Luca Boccassi <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/filesystems/fsverity.rst | 2 +-
fs/verity/fsverity_private.h | 17 ++++++++++++-----
fs/verity/signature.c | 2 +-
3 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 895e9711ed881..421b75498d49b 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -372,7 +372,7 @@ kernel. Specifically, it adds support for:
File measurements must be signed in the following format, which is
similar to the structure used by `FS_IOC_MEASURE_VERITY`_::
- struct fsverity_signed_digest {
+ struct fsverity_formatted_digest {
char magic[8]; /* must be "FSVerity" */
__le16 digest_algorithm;
__le16 digest_size;
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index e96d99d5145e1..75f8e18b44a5b 100644
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -101,12 +101,19 @@ struct fsverity_descriptor {
sizeof(struct fsverity_descriptor))
/*
- * Format in which verity file measurements are signed. 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.
+ * Format in which verity file measurements 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_signed_digest {
+struct fsverity_formatted_digest {
char magic[8]; /* must be "FSVerity" */
__le16 digest_algorithm;
__le16 digest_size;
diff --git a/fs/verity/signature.c b/fs/verity/signature.c
index 12794a4dd1585..74ae10f04d215 100644
--- a/fs/verity/signature.c
+++ b/fs/verity/signature.c
@@ -44,7 +44,7 @@ int fsverity_verify_signature(const struct fsverity_info *vi,
const struct inode *inode = vi->inode;
const struct fsverity_hash_alg *hash_alg = vi->tree_params.hash_alg;
const u32 sig_size = le32_to_cpu(desc->sig_size);
- struct fsverity_signed_digest *d;
+ struct fsverity_formatted_digest *d;
int err;
if (sig_size == 0) {
--
2.29.2
On Fri, 2020-11-13 at 13:19 -0800, Eric Biggers wrote:
> From: Eric Biggers <[email protected]>
>
> I originally chose the name "file measurement" to refer to the fs-verity
> file digest to avoid confusion with traditional full-file digests or
> with the bare root hash of the Merkle tree.
>
> But the name "file measurement" hasn't caught on, and usually people are
> calling it something else, usually the "file digest". E.g. see
> "struct fsverity_digest" and "struct fsverity_formatted_digest", the
> libfsverity_compute_digest() and libfsverity_sign_digest() functions in
> libfsverity, and the "fsverity digest" command.
>
> Having multiple names for the same thing is always confusing.
>
> So to hopefully avoid confusion in the future, rename
> "fs-verity file measurement" to "fs-verity file digest".
>
> This leaves FS_IOC_MEASURE_VERITY as the only reference to "measure" in
> the kernel, which makes some amount of sense since the ioctl is actively
> "measuring" the file.
>
> I'll be renaming this in fsverity-utils too (though similarly the
> 'fsverity measure' command, which is a wrapper for
> FS_IOC_MEASURE_VERITY, will stay).
>
> Signed-off-by: Eric Biggers <[email protected]>
> ---
> Documentation/filesystems/fsverity.rst | 60 +++++++++++++-------------
> fs/verity/enable.c | 6 +--
> fs/verity/fsverity_private.h | 12 +++---
> fs/verity/measure.c | 12 +++---
> fs/verity/open.c | 22 +++++-----
> fs/verity/signature.c | 10 ++---
> 6 files changed, 61 insertions(+), 61 deletions(-)
Acked-by: Luca Boccassi <[email protected]>
--
Kind regards,
Luca Boccassi
On Fri, 2020-11-13 at 13:19 -0800, Eric Biggers wrote:
> From: Eric Biggers <[email protected]>
>
> 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.
>
> Signed-off-by: Eric Biggers <[email protected]>
> ---
> Documentation/filesystems/fsverity.rst | 6 +---
> fs/verity/fsverity_private.h | 37 -------------------
> include/uapi/linux/fsverity.h | 49 ++++++++++++++++++++++++++
> 3 files changed, 50 insertions(+), 42 deletions(-)
Acked-by: Luca Boccassi <[email protected]>
--
Kind regards,
Luca Boccassi
On Fri, Nov 13, 2020 at 01:19:14PM -0800, Eric Biggers wrote:
> This patchset renames some names that have been causing confusion:
>
> - fsverity_signed_digest is renamed to fsverity_formatted_digest
>
> - "fs-verity file measurement" is renamed to "fs-verity file digest"
>
> In addition, this patchset moves fsverity_descriptor and
> fsverity_formatted_digest to the UAPI header because userspace programs
> may need them in order to sign files.
>
> Eric Biggers (4):
> fs-verity: remove filenames from file comments
> fs-verity: rename fsverity_signed_digest to fsverity_formatted_digest
> fs-verity: rename "file measurement" to "file digest"
> fs-verity: move structs needed for file signing to UAPI header
>
> Documentation/filesystems/fsverity.rst | 68 ++++++++++++--------------
> fs/verity/enable.c | 8 +--
> fs/verity/fsverity_private.h | 36 ++------------
> fs/verity/hash_algs.c | 2 +-
> fs/verity/init.c | 2 +-
> fs/verity/measure.c | 12 ++---
> fs/verity/open.c | 24 ++++-----
> fs/verity/signature.c | 14 +++---
> fs/verity/verify.c | 2 +-
> include/uapi/linux/fsverity.h | 49 +++++++++++++++++++
> 10 files changed, 116 insertions(+), 101 deletions(-)
All applied to fscrypt.git#fsverity for 5.11. But as always, more reviews are
always appreciated.
- Eric