[fsverity-utils PATCH v2 0/4] Add libfsverity_enable() and default params

[fsverity-utils PATCH v2 0/4] Add libfsverity_enable() and default params

[Eric Biggers]

This patchset adds wrappers around FS_IOC_ENABLE_VERITY to libfsverity,
makes libfsverity (rather than just the fsverity program) default to
SHA-256 and 4096-byte blocks, and makes the fsverity commands share code
to parse the libfsverity_merkle_tree_params.

This is my proposed alternative to Luca's patch
https://lkml.kernel.org/linux-fscrypt/20201113143527.1097499-1-luca.boccassi@gmail.com

Changed since v1:
  - Moved the default hash algorithm and block size handling into
    libfsverity.

Eric Biggers (4):
  programs/fsverity: change default block size from PAGE_SIZE to 4096
  lib/compute_digest: add default hash_algorithm and block_size
  lib: add libfsverity_enable() and libfsverity_enable_with_sig()
  programs/fsverity: share code to parse tree parameters

 include/libfsverity.h          | 83 +++++++++++++++++++++++++++++-----
 lib/compute_digest.c           | 27 ++++++-----
 lib/enable.c                   | 47 +++++++++++++++++++
 lib/lib_private.h              |  6 +++
 programs/cmd_digest.c          | 31 ++-----------
 programs/cmd_enable.c          | 34 +++-----------
 programs/cmd_sign.c            | 32 ++-----------
 programs/fsverity.c            | 35 ++++++++------
 programs/fsverity.h            | 21 ++++++---
 programs/test_compute_digest.c | 18 +++++---
 10 files changed, 201 insertions(+), 133 deletions(-)
 create mode 100644 lib/enable.c

-- 
2.29.2

[fsverity-utils PATCH v2 1/4] programs/fsverity: change default block size from PAGE_SIZE to 4096

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Even though the kernel currently only supports PAGE_SIZE == Merkle tree
block size, PAGE_SIZE isn't a good default Merkle tree block size for
fsverity-utils, since it means that if someone doesn't explicitly
specify the block size, then the results of 'fsverity sign' and
'fsverity enable' will differ between different architectures.

So change the default Merkle tree block size to 4096, which is the most
common PAGE_SIZE.  This will break anyone using the fsverity program
without the --block-size option on an architecture with a non-4K page
size.  But I don't think anyone is actually doing that yet anyway.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 programs/cmd_digest.c |  2 +-
 programs/cmd_enable.c |  2 +-
 programs/cmd_sign.c   |  2 +-
 programs/fsverity.c   | 14 --------------
 programs/fsverity.h   |  1 -
 5 files changed, 3 insertions(+), 18 deletions(-)

diff --git a/programs/cmd_digest.c b/programs/cmd_digest.c
index 180f438..7899b04 100644
--- a/programs/cmd_digest.c
+++ b/programs/cmd_digest.c
@@ -90,7 +90,7 @@ int fsverity_cmd_digest(const struct fsverity_command *cmd,
 		tree_params.hash_algorithm = FS_VERITY_HASH_ALG_DEFAULT;
 
 	if (tree_params.block_size == 0)
-		tree_params.block_size = get_default_block_size();
+		tree_params.block_size = 4096;
 
 	for (int i = 0; i < argc; i++) {
 		struct fsverity_signed_digest *d = NULL;
diff --git a/programs/cmd_enable.c b/programs/cmd_enable.c
index d90d208..ba5b088 100644
--- a/programs/cmd_enable.c
+++ b/programs/cmd_enable.c
@@ -114,7 +114,7 @@ int fsverity_cmd_enable(const struct fsverity_command *cmd,
 		arg.hash_algorithm = FS_VERITY_HASH_ALG_DEFAULT;
 
 	if (arg.block_size == 0)
-		arg.block_size = get_default_block_size();
+		arg.block_size = 4096;
 
 	if (!open_file(&file, argv[0], O_RDONLY, 0))
 		goto out_err;
diff --git a/programs/cmd_sign.c b/programs/cmd_sign.c
index 580e4df..9cb7507 100644
--- a/programs/cmd_sign.c
+++ b/programs/cmd_sign.c
@@ -105,7 +105,7 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 		tree_params.hash_algorithm = FS_VERITY_HASH_ALG_DEFAULT;
 
 	if (tree_params.block_size == 0)
-		tree_params.block_size = get_default_block_size();
+		tree_params.block_size = 4096;
 
 	if (sig_params.keyfile == NULL) {
 		error_msg("Missing --key argument");
diff --git a/programs/fsverity.c b/programs/fsverity.c
index 4a2f8df..33d0a3f 100644
--- a/programs/fsverity.c
+++ b/programs/fsverity.c
@@ -12,7 +12,6 @@
 #include "fsverity.h"
 
 #include <limits.h>
-#include <unistd.h>
 
 static const struct fsverity_command {
 	const char *name;
@@ -192,19 +191,6 @@ bool parse_salt_option(const char *arg, u8 **salt_ptr, u32 *salt_size_ptr)
 	return true;
 }
 
-u32 get_default_block_size(void)
-{
-	long n = sysconf(_SC_PAGESIZE);
-
-	if (n <= 0 || n >= INT_MAX || !is_power_of_2(n)) {
-		fprintf(stderr,
-			"Warning: invalid _SC_PAGESIZE (%ld).  Assuming 4K blocks.\n",
-			n);
-		return 4096;
-	}
-	return n;
-}
-
 int main(int argc, char *argv[])
 {
 	const struct fsverity_command *cmd;
diff --git a/programs/fsverity.h b/programs/fsverity.h
index 669fef2..2af5527 100644
--- a/programs/fsverity.h
+++ b/programs/fsverity.h
@@ -46,6 +46,5 @@ void usage(const struct fsverity_command *cmd, FILE *fp);
 bool parse_hash_alg_option(const char *arg, u32 *alg_ptr);
 bool parse_block_size_option(const char *arg, u32 *size_ptr);
 bool parse_salt_option(const char *arg, u8 **salt_ptr, u32 *salt_size_ptr);
-u32 get_default_block_size(void);
 
 #endif /* PROGRAMS_FSVERITY_H */
-- 
2.29.2

Re: [fsverity-utils PATCH v2 1/4] programs/fsverity: change default block size from PAGE_SIZE to 4096

[Luca Boccassi]

[-- Attachment #1: Type: text/plain, Size: 1141 bytes --]

On Mon, 2020-11-16 at 12:56 -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Even though the kernel currently only supports PAGE_SIZE == Merkle tree
> block size, PAGE_SIZE isn't a good default Merkle tree block size for
> fsverity-utils, since it means that if someone doesn't explicitly
> specify the block size, then the results of 'fsverity sign' and
> 'fsverity enable' will differ between different architectures.
> 
> So change the default Merkle tree block size to 4096, which is the most
> common PAGE_SIZE.  This will break anyone using the fsverity program
> without the --block-size option on an architecture with a non-4K page
> size.  But I don't think anyone is actually doing that yet anyway.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  programs/cmd_digest.c |  2 +-
>  programs/cmd_enable.c |  2 +-
>  programs/cmd_sign.c   |  2 +-
>  programs/fsverity.c   | 14 --------------
>  programs/fsverity.h   |  1 -
>  5 files changed, 3 insertions(+), 18 deletions(-)

Acked-by: Luca Boccassi <luca.boccassi@microsoft.com>

-- 
Kind regards,
Luca Boccassi

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[fsverity-utils PATCH v2 2/4] lib/compute_digest: add default hash_algorithm and block_size

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

If hash_algorithm is left 0, default it to FS_VERITY_HASH_ALG_SHA256;
and if block_size is left 0, default it to 4096 bytes.

While it's nice to be explicit, having defaults makes things easier for
library users.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 include/libfsverity.h          | 47 ++++++++++++++++++++++++++--------
 lib/compute_digest.c           | 27 +++++++++++--------
 lib/lib_private.h              |  6 +++++
 programs/cmd_digest.c          |  8 +-----
 programs/cmd_sign.c            |  9 +------
 programs/test_compute_digest.c | 18 ++++++++-----
 6 files changed, 71 insertions(+), 44 deletions(-)

diff --git a/include/libfsverity.h b/include/libfsverity.h
index 8f78a13..985b364 100644
--- a/include/libfsverity.h
+++ b/include/libfsverity.h
@@ -27,15 +27,42 @@ extern "C" {
 #define FS_VERITY_HASH_ALG_SHA256       1
 #define FS_VERITY_HASH_ALG_SHA512       2
 
+/**
+ * struct libfsverity_merkle_tree_params - properties of a file's Merkle tree
+ *
+ * Zero this, then fill in at least @version and @file_size.
+ */
 struct libfsverity_merkle_tree_params {
-	uint32_t version;		/* must be 1			*/
-	uint32_t hash_algorithm;	/* one of FS_VERITY_HASH_ALG_*	*/
-	uint64_t file_size;		/* file size in bytes		*/
-	uint32_t block_size;		/* Merkle tree block size in bytes */
-	uint32_t salt_size;		/* salt size in bytes (0 if unsalted) */
-	const uint8_t *salt;		/* pointer to salt (optional)	*/
-	uint64_t reserved1[8];		/* must be 0 */
-	uintptr_t reserved2[8];		/* must be 0 */
+
+	/** @version: must be 1 */
+	uint32_t version;
+
+	/**
+	 * @hash_algorithm: one of FS_VERITY_HASH_ALG_*, or 0 to use the default
+	 * of FS_VERITY_HASH_ALG_SHA256
+	 */
+	uint32_t hash_algorithm;
+
+	/** @file_size: the file size in bytes */
+	uint64_t file_size;
+
+	/**
+	 * @block_size: the Merkle tree block size in bytes, or 0 to use the
+	 * default of 4096 bytes
+	 */
+	uint32_t block_size;
+
+	/** @salt_size: the salt size in bytes, or 0 if unsalted */
+	uint32_t salt_size;
+
+	/** @salt: pointer to the salt, or NULL if unsalted */
+	const uint8_t *salt;
+
+	/** @reserved1: must be 0 */
+	uint64_t reserved1[8];
+
+	/** @reserved2: must be 0 */
+	uintptr_t reserved2[8];
 };
 
 struct libfsverity_digest {
@@ -69,9 +96,7 @@ typedef int (*libfsverity_read_fn_t)(void *fd, void *buf, size_t count);
  *          digest computed over the entire file.
  * @fd: context that will be passed to @read_fn
  * @read_fn: a function that will read the data of the file
- * @params: struct libfsverity_merkle_tree_params specifying the fs-verity
- *	    version, the hash algorithm, the file size, the block size, and
- *	    optionally a salt.  Reserved fields must be zero.
+ * @params: Pointer to the Merkle tree parameters
  * @digest_ret: Pointer to pointer for computed digest.
  *
  * Returns:
diff --git a/lib/compute_digest.c b/lib/compute_digest.c
index e0b213b..a36795d 100644
--- a/lib/compute_digest.c
+++ b/lib/compute_digest.c
@@ -164,6 +164,8 @@ libfsverity_compute_digest(void *fd, libfsverity_read_fn_t read_fn,
 			   const struct libfsverity_merkle_tree_params *params,
 			   struct libfsverity_digest **digest_ret)
 {
+	u32 alg_num;
+	u32 block_size;
 	const struct fsverity_hash_alg *hash_alg;
 	struct hash_ctx *hash = NULL;
 	struct libfsverity_digest *digest;
@@ -179,9 +181,13 @@ libfsverity_compute_digest(void *fd, libfsverity_read_fn_t read_fn,
 				      params->version);
 		return -EINVAL;
 	}
-	if (!is_power_of_2(params->block_size)) {
+
+	alg_num = params->hash_algorithm ?: FS_VERITY_HASH_ALG_DEFAULT;
+	block_size = params->block_size ?: FS_VERITY_BLOCK_SIZE_DEFAULT;
+
+	if (!is_power_of_2(block_size)) {
 		libfsverity_error_msg("unsupported block size (%u)",
-				      params->block_size);
+				      block_size);
 		return -EINVAL;
 	}
 	if (params->salt_size > sizeof(desc.salt)) {
@@ -201,16 +207,15 @@ libfsverity_compute_digest(void *fd, libfsverity_read_fn_t read_fn,
 		return -EINVAL;
 	}
 
-	hash_alg = libfsverity_find_hash_alg_by_num(params->hash_algorithm);
+	hash_alg = libfsverity_find_hash_alg_by_num(alg_num);
 	if (!hash_alg) {
-		libfsverity_error_msg("unknown hash algorithm: %u",
-				      params->hash_algorithm);
+		libfsverity_error_msg("unknown hash algorithm: %u", alg_num);
 		return -EINVAL;
 	}
 
-	if (params->block_size < 2 * hash_alg->digest_size) {
+	if (block_size < 2 * hash_alg->digest_size) {
 		libfsverity_error_msg("block size (%u) too small for hash algorithm %s",
-				      params->block_size, hash_alg->name);
+				      block_size, hash_alg->name);
 		return -EINVAL;
 	}
 
@@ -220,8 +225,8 @@ libfsverity_compute_digest(void *fd, libfsverity_read_fn_t read_fn,
 
 	memset(&desc, 0, sizeof(desc));
 	desc.version = 1;
-	desc.hash_algorithm = params->hash_algorithm;
-	desc.log_blocksize = ilog2(params->block_size);
+	desc.hash_algorithm = alg_num;
+	desc.log_blocksize = ilog2(block_size);
 	desc.data_size = cpu_to_le64(params->file_size);
 	if (params->salt_size != 0) {
 		memcpy(desc.salt, params->salt, params->salt_size);
@@ -229,7 +234,7 @@ libfsverity_compute_digest(void *fd, libfsverity_read_fn_t read_fn,
 	}
 
 	err = compute_root_hash(fd, read_fn, params->file_size, hash,
-				params->block_size, params->salt,
+				block_size, params->salt,
 				params->salt_size, desc.root_hash);
 	if (err)
 		goto out;
@@ -239,7 +244,7 @@ libfsverity_compute_digest(void *fd, libfsverity_read_fn_t read_fn,
 		err = -ENOMEM;
 		goto out;
 	}
-	digest->digest_algorithm = params->hash_algorithm;
+	digest->digest_algorithm = alg_num;
 	digest->digest_size = hash_alg->digest_size;
 	libfsverity_hash_full(hash, &desc, sizeof(desc), digest->digest);
 	*digest_ret = digest;
diff --git a/lib/lib_private.h b/lib/lib_private.h
index ff00490..7768eea 100644
--- a/lib/lib_private.h
+++ b/lib/lib_private.h
@@ -19,6 +19,12 @@
 
 #define LIBEXPORT	__attribute__((visibility("default")))
 
+/* The hash algorithm that libfsverity assumes when none is specified */
+#define FS_VERITY_HASH_ALG_DEFAULT	FS_VERITY_HASH_ALG_SHA256
+
+/* The block size that libfsverity assumes when none is specified */
+#define FS_VERITY_BLOCK_SIZE_DEFAULT	4096
+
 /* hash_algs.c */
 
 struct fsverity_hash_alg {
diff --git a/programs/cmd_digest.c b/programs/cmd_digest.c
index 7899b04..4f7818e 100644
--- a/programs/cmd_digest.c
+++ b/programs/cmd_digest.c
@@ -86,12 +86,6 @@ int fsverity_cmd_digest(const struct fsverity_command *cmd,
 	if (argc < 1)
 		goto out_usage;
 
-	if (tree_params.hash_algorithm == 0)
-		tree_params.hash_algorithm = FS_VERITY_HASH_ALG_DEFAULT;
-
-	if (tree_params.block_size == 0)
-		tree_params.block_size = 4096;
-
 	for (int i = 0; i < argc; i++) {
 		struct fsverity_signed_digest *d = NULL;
 		struct libfsverity_digest *digest = NULL;
@@ -137,7 +131,7 @@ int fsverity_cmd_digest(const struct fsverity_command *cmd,
 			printf("%s %s\n", digest_hex, argv[i]);
 		else
 			printf("%s:%s %s\n",
-			       libfsverity_get_hash_name(tree_params.hash_algorithm),
+			       libfsverity_get_hash_name(digest->digest_algorithm),
 			       digest_hex, argv[i]);
 
 		filedes_close(&file);
diff --git a/programs/cmd_sign.c b/programs/cmd_sign.c
index 9cb7507..4b90944 100644
--- a/programs/cmd_sign.c
+++ b/programs/cmd_sign.c
@@ -101,12 +101,6 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 	if (argc != 2)
 		goto out_usage;
 
-	if (tree_params.hash_algorithm == 0)
-		tree_params.hash_algorithm = FS_VERITY_HASH_ALG_DEFAULT;
-
-	if (tree_params.block_size == 0)
-		tree_params.block_size = 4096;
-
 	if (sig_params.keyfile == NULL) {
 		error_msg("Missing --key argument");
 		goto out_usage;
@@ -138,8 +132,7 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 	ASSERT(digest->digest_size <= FS_VERITY_MAX_DIGEST_SIZE);
 	bin2hex(digest->digest, digest->digest_size, digest_hex);
 	printf("Signed file '%s' (%s:%s)\n", argv[0],
-	       libfsverity_get_hash_name(tree_params.hash_algorithm),
-	       digest_hex);
+	       libfsverity_get_hash_name(digest->digest_algorithm), digest_hex);
 	status = 0;
 out:
 	filedes_close(&file);
diff --git a/programs/test_compute_digest.c b/programs/test_compute_digest.c
index eee10f7..e7f2645 100644
--- a/programs/test_compute_digest.c
+++ b/programs/test_compute_digest.c
@@ -139,7 +139,13 @@ static const struct test_case {
 			  "\x56\xce\x29\xa9\x60\xbf\x4b\xb0"
 			  "\xe5\x95\xec\x38\x6c\xa5\x8c\x06"
 			  "\x51\x9d\x54\x6d\xc5\xb1\x97\xbb",
-	}
+	}, { /* default hash algorithm (SHA-256) and block size (4096) */
+		.file_size = 100000,
+		.digest = "\xf2\x09\x6a\x36\xc5\xcd\xca\x4f"
+			  "\xa3\x3e\xe8\x85\x28\x33\x15\x0b"
+			  "\xb3\x24\x99\x2e\x54\x17\xa9\xd5"
+			  "\x71\xf1\xbf\xff\xf7\x3b\x9e\xfc",
+	},
 };
 
 static void fix_digest_and_print(const struct test_case *t,
@@ -206,15 +212,11 @@ static void test_invalid_params(void)
 
 	/* bad hash_algorithm */
 	params = good_params;
-	params.hash_algorithm = 0;
-	ASSERT(libfsverity_compute_digest(&f, read_fn, &params, &d) == -EINVAL);
 	params.hash_algorithm = 1000;
 	ASSERT(libfsverity_compute_digest(&f, read_fn, &params, &d) == -EINVAL);
 
 	/* bad block_size */
 	params = good_params;
-	params.block_size = 0;
-	ASSERT(libfsverity_compute_digest(&f, read_fn, &params, &d) == -EINVAL);
 	params.block_size = 1;
 	ASSERT(libfsverity_compute_digest(&f, read_fn, &params, &d) == -EINVAL);
 	params.block_size = 4097;
@@ -266,6 +268,8 @@ int main(int argc, char *argv[])
 		f.data[i] = (i % 11) + (i % 439) + (i % 1103);
 
 	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		u32 expected_alg = test_cases[i].hash_algorithm ?:
+				   FS_VERITY_HASH_ALG_SHA256;
 
 		memset(&params, 0, sizeof(params));
 		params.version = 1;
@@ -283,9 +287,9 @@ int main(int argc, char *argv[])
 		err = libfsverity_compute_digest(&f, read_fn, &params, &d);
 		ASSERT(err == 0);
 
-		ASSERT(d->digest_algorithm == test_cases[i].hash_algorithm);
+		ASSERT(d->digest_algorithm == expected_alg);
 		ASSERT(d->digest_size ==
-		       libfsverity_get_digest_size(test_cases[i].hash_algorithm));
+		       libfsverity_get_digest_size(expected_alg));
 		if (update)
 			fix_digest_and_print(&test_cases[i], d);
 		else
-- 
2.29.2

Re: [fsverity-utils PATCH v2 2/4] lib/compute_digest: add default hash_algorithm and block_size

[Luca Boccassi]

[-- Attachment #1: Type: text/plain, Size: 875 bytes --]

On Mon, 2020-11-16 at 12:56 -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> If hash_algorithm is left 0, default it to FS_VERITY_HASH_ALG_SHA256;
> and if block_size is left 0, default it to 4096 bytes.
> 
> While it's nice to be explicit, having defaults makes things easier for
> library users.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  include/libfsverity.h          | 47 ++++++++++++++++++++++++++--------
>  lib/compute_digest.c           | 27 +++++++++++--------
>  lib/lib_private.h              |  6 +++++
>  programs/cmd_digest.c          |  8 +-----
>  programs/cmd_sign.c            |  9 +------
>  programs/test_compute_digest.c | 18 ++++++++-----
>  6 files changed, 71 insertions(+), 44 deletions(-)

Acked-by: Luca Boccassi <luca.boccassi@microsoft.com>

-- 
Kind regards,
Luca Boccassi

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[fsverity-utils PATCH v2 3/4] lib: add libfsverity_enable() and libfsverity_enable_with_sig()

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Add convenience functions that wrap FS_IOC_ENABLE_VERITY but take a
'struct libfsverity_merkle_tree_params' instead of
'struct fsverity_enable_arg'.  This is useful because it allows
libfsverity users to deal with one common struct, and also get the
default parameter handling that libfsverity_compute_digest() does.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 include/libfsverity.h | 36 +++++++++++++++++++++++++++++++++
 lib/enable.c          | 47 +++++++++++++++++++++++++++++++++++++++++++
 programs/cmd_enable.c | 26 +++++++++++-------------
 programs/fsverity.h   |  3 ---
 4 files changed, 95 insertions(+), 17 deletions(-)
 create mode 100644 lib/enable.c

diff --git a/include/libfsverity.h b/include/libfsverity.h
index 985b364..369e1cf 100644
--- a/include/libfsverity.h
+++ b/include/libfsverity.h
@@ -137,6 +137,42 @@ libfsverity_sign_digest(const struct libfsverity_digest *digest,
 			const struct libfsverity_signature_params *sig_params,
 			uint8_t **sig_ret, size_t *sig_size_ret);
 
+/**
+ * libfsverity_enable() - Enable fs-verity on a file
+ * @fd: read-only file descriptor to the file
+ * @params: pointer to the Merkle tree parameters
+ *
+ * This is a simple wrapper around the FS_IOC_ENABLE_VERITY ioctl.
+ *
+ * Return: 0 on success, -EINVAL for invalid arguments, or a negative errno
+ *	   value from the FS_IOC_ENABLE_VERITY ioctl.  See
+ *	   Documentation/filesystems/fsverity.rst in the kernel source tree for
+ *	   the possible error codes from FS_IOC_ENABLE_VERITY.
+ */
+int
+libfsverity_enable(int fd, const struct libfsverity_merkle_tree_params *params);
+
+/**
+ * libfsverity_enable_with_sig() - Enable fs-verity on a file, with a signature
+ * @fd: read-only file descriptor to the file
+ * @params: pointer to the Merkle tree parameters
+ * @sig: pointer to the file's signature
+ * @sig_size: size of the file's signature in bytes
+ *
+ * Like libfsverity_enable(), but allows specifying a built-in signature (i.e. a
+ * singature created with libfsverity_sign_digest()) to associate with the file.
+ * This is only needed if the in-kernel signature verification support is being
+ * used; it is not needed if signatures are being verified in userspace.
+ *
+ * If @sig is NULL and @sig_size is 0, this is the same as libfsverity_enable().
+ *
+ * Return: See libfsverity_enable().
+ */
+int
+libfsverity_enable_with_sig(int fd,
+			    const struct libfsverity_merkle_tree_params *params,
+			    const uint8_t *sig, size_t sig_size);
+
 /**
  * libfsverity_find_hash_alg_by_name() - Find hash algorithm by name
  * @name: Pointer to name of hash algorithm
diff --git a/lib/enable.c b/lib/enable.c
new file mode 100644
index 0000000..c27ec89
--- /dev/null
+++ b/lib/enable.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Implementation of libfsverity_enable() and libfsverity_enable_with_sig().
+ *
+ * Copyright 2020 Google LLC
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+#include "lib_private.h"
+
+#include <sys/ioctl.h>
+
+LIBEXPORT int
+libfsverity_enable(int fd, const struct libfsverity_merkle_tree_params *params)
+{
+	return libfsverity_enable_with_sig(fd, params, NULL, 0);
+}
+
+LIBEXPORT int
+libfsverity_enable_with_sig(int fd,
+			    const struct libfsverity_merkle_tree_params *params,
+			    const uint8_t *sig, size_t sig_size)
+{
+	struct fsverity_enable_arg arg = {};
+
+	if (!params) {
+		libfsverity_error_msg("missing required parameters for enable");
+		return -EINVAL;
+	}
+
+	arg.version = 1;
+	arg.hash_algorithm =
+		params->hash_algorithm ?: FS_VERITY_HASH_ALG_DEFAULT;
+	arg.block_size =
+		params->block_size ?: FS_VERITY_BLOCK_SIZE_DEFAULT;
+	arg.salt_size = params->salt_size;
+	arg.salt_ptr = (uintptr_t)params->salt;
+	arg.sig_size = sig_size;
+	arg.sig_ptr = (uintptr_t)sig;
+
+	if (ioctl(fd, FS_IOC_ENABLE_VERITY, &arg) != 0)
+		return -errno;
+	return 0;
+}
diff --git a/programs/cmd_enable.c b/programs/cmd_enable.c
index ba5b088..b0e0c98 100644
--- a/programs/cmd_enable.c
+++ b/programs/cmd_enable.c
@@ -68,9 +68,10 @@ static const struct option longopts[] = {
 int fsverity_cmd_enable(const struct fsverity_command *cmd,
 			int argc, char *argv[])
 {
-	struct fsverity_enable_arg arg = { .version = 1 };
+	struct libfsverity_merkle_tree_params tree_params = { .version = 1 };
 	u8 *salt = NULL;
 	u8 *sig = NULL;
+	u32 sig_size = 0;
 	struct filedes file;
 	int status;
 	int c;
@@ -78,26 +79,28 @@ int fsverity_cmd_enable(const struct fsverity_command *cmd,
 	while ((c = getopt_long(argc, argv, "", longopts, NULL)) != -1) {
 		switch (c) {
 		case OPT_HASH_ALG:
-			if (!parse_hash_alg_option(optarg, &arg.hash_algorithm))
+			if (!parse_hash_alg_option(optarg,
+						   &tree_params.hash_algorithm))
 				goto out_usage;
 			break;
 		case OPT_BLOCK_SIZE:
-			if (!parse_block_size_option(optarg, &arg.block_size))
+			if (!parse_block_size_option(optarg,
+						     &tree_params.block_size))
 				goto out_usage;
 			break;
 		case OPT_SALT:
-			if (!parse_salt_option(optarg, &salt, &arg.salt_size))
+			if (!parse_salt_option(optarg, &salt,
+					       &tree_params.salt_size))
 				goto out_usage;
-			arg.salt_ptr = (uintptr_t)salt;
+			tree_params.salt = salt;
 			break;
 		case OPT_SIGNATURE:
 			if (sig != NULL) {
 				error_msg("--signature can only be specified once");
 				goto out_usage;
 			}
-			if (!read_signature(optarg, &sig, &arg.sig_size))
+			if (!read_signature(optarg, &sig, &sig_size))
 				goto out_err;
-			arg.sig_ptr = (uintptr_t)sig;
 			break;
 		default:
 			goto out_usage;
@@ -110,15 +113,10 @@ int fsverity_cmd_enable(const struct fsverity_command *cmd,
 	if (argc != 1)
 		goto out_usage;
 
-	if (arg.hash_algorithm == 0)
-		arg.hash_algorithm = FS_VERITY_HASH_ALG_DEFAULT;
-
-	if (arg.block_size == 0)
-		arg.block_size = 4096;
-
 	if (!open_file(&file, argv[0], O_RDONLY, 0))
 		goto out_err;
-	if (ioctl(file.fd, FS_IOC_ENABLE_VERITY, &arg) != 0) {
+
+	if (libfsverity_enable_with_sig(file.fd, &tree_params, sig, sig_size)) {
 		error_msg_errno("FS_IOC_ENABLE_VERITY failed on '%s'",
 				file.name);
 		filedes_close(&file);
diff --git a/programs/fsverity.h b/programs/fsverity.h
index 2af5527..37a6294 100644
--- a/programs/fsverity.h
+++ b/programs/fsverity.h
@@ -14,9 +14,6 @@
 #include "utils.h"
 #include "../common/fsverity_uapi.h"
 
-/* The hash algorithm that 'fsverity' assumes when none is specified */
-#define FS_VERITY_HASH_ALG_DEFAULT	FS_VERITY_HASH_ALG_SHA256
-
 /*
  * Largest digest size among all hash algorithms supported by fs-verity.
  * This can be increased if needed.
-- 
2.29.2

Re: [fsverity-utils PATCH v2 3/4] lib: add libfsverity_enable() and libfsverity_enable_with_sig()

[Luca Boccassi]

[-- Attachment #1: Type: text/plain, Size: 916 bytes --]

On Mon, 2020-11-16 at 12:56 -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add convenience functions that wrap FS_IOC_ENABLE_VERITY but take a
> 'struct libfsverity_merkle_tree_params' instead of
> 'struct fsverity_enable_arg'.  This is useful because it allows
> libfsverity users to deal with one common struct, and also get the
> default parameter handling that libfsverity_compute_digest() does.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  include/libfsverity.h | 36 +++++++++++++++++++++++++++++++++
>  lib/enable.c          | 47 +++++++++++++++++++++++++++++++++++++++++++
>  programs/cmd_enable.c | 26 +++++++++++-------------
>  programs/fsverity.h   |  3 ---
>  4 files changed, 95 insertions(+), 17 deletions(-)
>  create mode 100644 lib/enable.c

Acked-by: Luca Boccassi <luca.boccassi@microsoft.com>

-- 
Kind regards,
Luca Boccassi

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[fsverity-utils PATCH v2 4/4] programs/fsverity: share code to parse tree parameters

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

The "digest", "enable", and "sign" commands all parse the --hash-alg,
--block-size, and --salt options and initialize a struct
libfsverity_merkle_tree_params, so share the code that does this.

Acked-by: Luca Boccassi <luca.boccassi@microsoft.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 programs/cmd_digest.c | 23 ++---------------------
 programs/cmd_enable.c | 22 ++--------------------
 programs/cmd_sign.c   | 23 ++---------------------
 programs/fsverity.c   | 29 ++++++++++++++++++++++++++---
 programs/fsverity.h   | 17 ++++++++++++++---
 5 files changed, 46 insertions(+), 68 deletions(-)

diff --git a/programs/cmd_digest.c b/programs/cmd_digest.c
index 4f7818e..68a1c9a 100644
--- a/programs/cmd_digest.c
+++ b/programs/cmd_digest.c
@@ -14,14 +14,6 @@
 #include <fcntl.h>
 #include <getopt.h>
 
-enum {
-	OPT_HASH_ALG,
-	OPT_BLOCK_SIZE,
-	OPT_SALT,
-	OPT_COMPACT,
-	OPT_FOR_BUILTIN_SIG,
-};
-
 static const struct option longopts[] = {
 	{"hash-alg",		required_argument, NULL, OPT_HASH_ALG},
 	{"block-size",		required_argument, NULL, OPT_BLOCK_SIZE},
@@ -44,7 +36,6 @@ struct fsverity_signed_digest {
 int fsverity_cmd_digest(const struct fsverity_command *cmd,
 		      int argc, char *argv[])
 {
-	u8 *salt = NULL;
 	struct filedes file = { .fd = -1 };
 	struct libfsverity_merkle_tree_params tree_params = { .version = 1 };
 	bool compact = false, for_builtin_sig = false;
@@ -54,20 +45,10 @@ int fsverity_cmd_digest(const struct fsverity_command *cmd,
 	while ((c = getopt_long(argc, argv, "", longopts, NULL)) != -1) {
 		switch (c) {
 		case OPT_HASH_ALG:
-			if (!parse_hash_alg_option(optarg,
-						   &tree_params.hash_algorithm))
-				goto out_usage;
-			break;
 		case OPT_BLOCK_SIZE:
-			if (!parse_block_size_option(optarg,
-						     &tree_params.block_size))
-				goto out_usage;
-			break;
 		case OPT_SALT:
-			if (!parse_salt_option(optarg, &salt,
-					       &tree_params.salt_size))
+			if (!parse_tree_param(c, optarg, &tree_params))
 				goto out_usage;
-			tree_params.salt = salt;
 			break;
 		case OPT_COMPACT:
 			compact = true;
@@ -140,7 +121,7 @@ int fsverity_cmd_digest(const struct fsverity_command *cmd,
 	}
 	status = 0;
 out:
-	free(salt);
+	destroy_tree_params(&tree_params);
 	return status;
 
 out_err:
diff --git a/programs/cmd_enable.c b/programs/cmd_enable.c
index b0e0c98..fdf26c7 100644
--- a/programs/cmd_enable.c
+++ b/programs/cmd_enable.c
@@ -49,13 +49,6 @@ out:
 	return ok;
 }
 
-enum {
-	OPT_HASH_ALG,
-	OPT_BLOCK_SIZE,
-	OPT_SALT,
-	OPT_SIGNATURE,
-};
-
 static const struct option longopts[] = {
 	{"hash-alg",	required_argument, NULL, OPT_HASH_ALG},
 	{"block-size",	required_argument, NULL, OPT_BLOCK_SIZE},
@@ -69,7 +62,6 @@ int fsverity_cmd_enable(const struct fsverity_command *cmd,
 			int argc, char *argv[])
 {
 	struct libfsverity_merkle_tree_params tree_params = { .version = 1 };
-	u8 *salt = NULL;
 	u8 *sig = NULL;
 	u32 sig_size = 0;
 	struct filedes file;
@@ -79,20 +71,10 @@ int fsverity_cmd_enable(const struct fsverity_command *cmd,
 	while ((c = getopt_long(argc, argv, "", longopts, NULL)) != -1) {
 		switch (c) {
 		case OPT_HASH_ALG:
-			if (!parse_hash_alg_option(optarg,
-						   &tree_params.hash_algorithm))
-				goto out_usage;
-			break;
 		case OPT_BLOCK_SIZE:
-			if (!parse_block_size_option(optarg,
-						     &tree_params.block_size))
-				goto out_usage;
-			break;
 		case OPT_SALT:
-			if (!parse_salt_option(optarg, &salt,
-					       &tree_params.salt_size))
+			if (!parse_tree_param(c, optarg, &tree_params))
 				goto out_usage;
-			tree_params.salt = salt;
 			break;
 		case OPT_SIGNATURE:
 			if (sig != NULL) {
@@ -127,7 +109,7 @@ int fsverity_cmd_enable(const struct fsverity_command *cmd,
 
 	status = 0;
 out:
-	free(salt);
+	destroy_tree_params(&tree_params);
 	free(sig);
 	return status;
 
diff --git a/programs/cmd_sign.c b/programs/cmd_sign.c
index 4b90944..0a08faa 100644
--- a/programs/cmd_sign.c
+++ b/programs/cmd_sign.c
@@ -26,14 +26,6 @@ static bool write_signature(const char *filename, const u8 *sig, u32 sig_size)
 	return ok;
 }
 
-enum {
-	OPT_HASH_ALG,
-	OPT_BLOCK_SIZE,
-	OPT_SALT,
-	OPT_KEY,
-	OPT_CERT,
-};
-
 static const struct option longopts[] = {
 	{"hash-alg",	required_argument, NULL, OPT_HASH_ALG},
 	{"block-size",	required_argument, NULL, OPT_BLOCK_SIZE},
@@ -48,7 +40,6 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 		      int argc, char *argv[])
 {
 	struct filedes file = { .fd = -1 };
-	u8 *salt = NULL;
 	struct libfsverity_merkle_tree_params tree_params = { .version = 1 };
 	struct libfsverity_signature_params sig_params = {};
 	struct libfsverity_digest *digest = NULL;
@@ -61,20 +52,10 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 	while ((c = getopt_long(argc, argv, "", longopts, NULL)) != -1) {
 		switch (c) {
 		case OPT_HASH_ALG:
-			if (!parse_hash_alg_option(optarg,
-						   &tree_params.hash_algorithm))
-				goto out_usage;
-			break;
 		case OPT_BLOCK_SIZE:
-			if (!parse_block_size_option(optarg,
-						     &tree_params.block_size))
-				goto out_usage;
-			break;
 		case OPT_SALT:
-			if (!parse_salt_option(optarg, &salt,
-					       &tree_params.salt_size))
+			if (!parse_tree_param(c, optarg, &tree_params))
 				goto out_usage;
-			tree_params.salt = salt;
 			break;
 		case OPT_KEY:
 			if (sig_params.keyfile != NULL) {
@@ -136,7 +117,7 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 	status = 0;
 out:
 	filedes_close(&file);
-	free(salt);
+	destroy_tree_params(&tree_params);
 	free(digest);
 	free(sig);
 	return status;
diff --git a/programs/fsverity.c b/programs/fsverity.c
index 33d0a3f..60ae05b 100644
--- a/programs/fsverity.c
+++ b/programs/fsverity.c
@@ -133,7 +133,7 @@ static const struct fsverity_command *find_command(const char *name)
 	return NULL;
 }
 
-bool parse_hash_alg_option(const char *arg, u32 *alg_ptr)
+static bool parse_hash_alg_option(const char *arg, u32 *alg_ptr)
 {
 	char *end;
 	unsigned long n = strtoul(arg, &end, 10);
@@ -158,7 +158,7 @@ bool parse_hash_alg_option(const char *arg, u32 *alg_ptr)
 	return false;
 }
 
-bool parse_block_size_option(const char *arg, u32 *size_ptr)
+static bool parse_block_size_option(const char *arg, u32 *size_ptr)
 {
 	char *end;
 	unsigned long n = strtoul(arg, &end, 10);
@@ -176,7 +176,8 @@ bool parse_block_size_option(const char *arg, u32 *size_ptr)
 	return true;
 }
 
-bool parse_salt_option(const char *arg, u8 **salt_ptr, u32 *salt_size_ptr)
+static bool parse_salt_option(const char *arg, u8 **salt_ptr,
+			      u32 *salt_size_ptr)
 {
 	if (*salt_ptr != NULL) {
 		error_msg("--salt can only be specified once");
@@ -191,6 +192,28 @@ bool parse_salt_option(const char *arg, u8 **salt_ptr, u32 *salt_size_ptr)
 	return true;
 }
 
+bool parse_tree_param(int opt_char, const char *arg,
+		      struct libfsverity_merkle_tree_params *params)
+{
+	switch (opt_char) {
+	case OPT_HASH_ALG:
+		return parse_hash_alg_option(arg, &params->hash_algorithm);
+	case OPT_BLOCK_SIZE:
+		return parse_block_size_option(arg, &params->block_size);
+	case OPT_SALT:
+		return parse_salt_option(arg, (u8 **)&params->salt,
+					 &params->salt_size);
+	default:
+		ASSERT(0);
+	}
+}
+
+void destroy_tree_params(struct libfsverity_merkle_tree_params *params)
+{
+	free((u8 *)params->salt);
+	memset(params, 0, sizeof(*params));
+}
+
 int main(int argc, char *argv[])
 {
 	const struct fsverity_command *cmd;
diff --git a/programs/fsverity.h b/programs/fsverity.h
index 37a6294..45c4fe1 100644
--- a/programs/fsverity.h
+++ b/programs/fsverity.h
@@ -20,6 +20,17 @@
  */
 #define FS_VERITY_MAX_DIGEST_SIZE	64
 
+enum {
+	OPT_BLOCK_SIZE,
+	OPT_CERT,
+	OPT_COMPACT,
+	OPT_FOR_BUILTIN_SIG,
+	OPT_HASH_ALG,
+	OPT_KEY,
+	OPT_SALT,
+	OPT_SIGNATURE,
+};
+
 struct fsverity_command;
 
 /* cmd_digest.c */
@@ -40,8 +51,8 @@ int fsverity_cmd_sign(const struct fsverity_command *cmd,
 
 /* fsverity.c */
 void usage(const struct fsverity_command *cmd, FILE *fp);
-bool parse_hash_alg_option(const char *arg, u32 *alg_ptr);
-bool parse_block_size_option(const char *arg, u32 *size_ptr);
-bool parse_salt_option(const char *arg, u8 **salt_ptr, u32 *salt_size_ptr);
+bool parse_tree_param(int opt_char, const char *arg,
+		      struct libfsverity_merkle_tree_params *params);
+void destroy_tree_params(struct libfsverity_merkle_tree_params *params);
 
 #endif /* PROGRAMS_FSVERITY_H */
-- 
2.29.2

Re: [fsverity-utils PATCH v2 0/4] Add libfsverity_enable() and default params

[Luca Boccassi]

[-- Attachment #1: Type: text/plain, Size: 1611 bytes --]

On Mon, 2020-11-16 at 12:56 -0800, Eric Biggers wrote:
> This patchset adds wrappers around FS_IOC_ENABLE_VERITY to libfsverity,
> makes libfsverity (rather than just the fsverity program) default to
> SHA-256 and 4096-byte blocks, and makes the fsverity commands share code
> to parse the libfsverity_merkle_tree_params.
> 
> This is my proposed alternative to Luca's patch
> https://lkml.kernel.org/linux-fscrypt/20201113143527.1097499-1-luca.boccassi@gmail.com
> 
> Changed since v1:
>   - Moved the default hash algorithm and block size handling into
>     libfsverity.
> 
> Eric Biggers (4):
>   programs/fsverity: change default block size from PAGE_SIZE to 4096
>   lib/compute_digest: add default hash_algorithm and block_size
>   lib: add libfsverity_enable() and libfsverity_enable_with_sig()
>   programs/fsverity: share code to parse tree parameters
> 
>  include/libfsverity.h          | 83 +++++++++++++++++++++++++++++-----
>  lib/compute_digest.c           | 27 ++++++-----
>  lib/enable.c                   | 47 +++++++++++++++++++
>  lib/lib_private.h              |  6 +++
>  programs/cmd_digest.c          | 31 ++-----------
>  programs/cmd_enable.c          | 34 +++-----------
>  programs/cmd_sign.c            | 32 ++-----------
>  programs/fsverity.c            | 35 ++++++++------
>  programs/fsverity.h            | 21 ++++++---
>  programs/test_compute_digest.c | 18 +++++---
>  10 files changed, 201 insertions(+), 133 deletions(-)
>  create mode 100644 lib/enable.c

Tried on my machine, looks great, thank you!

-- 
Kind regards,
Luca Boccassi

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Re: [fsverity-utils PATCH v2 0/4] Add libfsverity_enable() and default params

[Eric Biggers]

On Mon, Nov 16, 2020 at 12:56:24PM -0800, Eric Biggers wrote:
> This patchset adds wrappers around FS_IOC_ENABLE_VERITY to libfsverity,
> makes libfsverity (rather than just the fsverity program) default to
> SHA-256 and 4096-byte blocks, and makes the fsverity commands share code
> to parse the libfsverity_merkle_tree_params.
> 
> This is my proposed alternative to Luca's patch
> https://lkml.kernel.org/linux-fscrypt/20201113143527.1097499-1-luca.boccassi@gmail.com
> 
> Changed since v1:
>   - Moved the default hash algorithm and block size handling into
>     libfsverity.
> 
> Eric Biggers (4):
>   programs/fsverity: change default block size from PAGE_SIZE to 4096
>   lib/compute_digest: add default hash_algorithm and block_size
>   lib: add libfsverity_enable() and libfsverity_enable_with_sig()
>   programs/fsverity: share code to parse tree parameters
> 

All applied.

- Eric