diff mbox series

[v2,2/6] fs-verity: define a function to return the integrity protected file digest

Message ID 20220109185517.312280-3-zohar@linux.ibm.com (mailing list archive)
State Superseded
Headers show
Series ima: support fs-verity digests and signatures | expand

Commit Message

Mimi Zohar Jan. 9, 2022, 6:55 p.m. UTC
Define a function named fsverity_get_digest() to return the verity file
digest and the associated hash algorithm (enum hash_algo).

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 fs/verity/Kconfig            |  1 +
 fs/verity/fsverity_private.h |  7 -------
 fs/verity/measure.c          | 40 ++++++++++++++++++++++++++++++++++++
 include/linux/fsverity.h     | 18 ++++++++++++++++
 4 files changed, 59 insertions(+), 7 deletions(-)

Comments

Vitaly Chikunov Jan. 10, 2022, 12:47 a.m. UTC | #1
Mimi,

On Sun, Jan 09, 2022 at 01:55:13PM -0500, Mimi Zohar wrote:
> Define a function named fsverity_get_digest() to return the verity file
> digest and the associated hash algorithm (enum hash_algo).
> 
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
>  fs/verity/Kconfig            |  1 +
>  fs/verity/fsverity_private.h |  7 -------
>  fs/verity/measure.c          | 40 ++++++++++++++++++++++++++++++++++++
>  include/linux/fsverity.h     | 18 ++++++++++++++++
>  4 files changed, 59 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/verity/measure.c b/fs/verity/measure.c
> index f0d7b30c62db..52906b2e5811 100644
> --- a/fs/verity/measure.c
> +++ b/fs/verity/measure.c
> @@ -57,3 +57,43 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
> +
> +/**
> + * fsverity_get_digest() - get a verity file's digest
> + * @inode: inode to get digest of
> + * @digest: (out) pointer to the digest
> + * @alg: (out) pointer to the hash algorithm enumeration
> + *
> + * Return the file hash algorithm and digest of an fsverity protected file.
> + *
> + * Return: 0 on success, -errno on failure
> + */
> +int fsverity_get_digest(struct inode *inode,
> +			    u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
> +			    enum hash_algo *alg)
> +{
> +	const struct fsverity_info *vi;
> +	const struct fsverity_hash_alg *hash_alg;
> +	int i;
> +
> +	vi = fsverity_get_info(inode);
> +	if (!vi)
> +		return -ENODATA; /* not a verity file */
> +
> +	hash_alg = vi->tree_params.hash_alg;
> +	memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
> +	*alg = HASH_ALGO__LAST;

Perhaps this line is redundant (*alg is overwritten later) and would
needlessly mangle output value in case of -EINVAL while it's being
untouched on -ENODATA.

Thanks,

> +
> +	/* convert hash algorithm to hash_algo_name */
> +	i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
> +	if (i < 0)
> +		return -EINVAL;
> +	*alg = i;
> +
> +	memcpy(digest, vi->file_digest, hash_alg->digest_size);
> +
> +	pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
> +		  hash_digest_size[*alg], digest);
> +
> +	return 0;
> +}
Mimi Zohar Jan. 10, 2022, 12:13 p.m. UTC | #2
Hi Vitaly,

On Mon, 2022-01-10 at 03:47 +0300, Vitaly Chikunov wrote:
> Mimi,
> 
> On Sun, Jan 09, 2022 at 01:55:13PM -0500, Mimi Zohar wrote:
> > Define a function named fsverity_get_digest() to return the verity file
> > digest and the associated hash algorithm (enum hash_algo).
> > 
> > Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> > ---
> >  fs/verity/Kconfig            |  1 +
> >  fs/verity/fsverity_private.h |  7 -------
> >  fs/verity/measure.c          | 40 ++++++++++++++++++++++++++++++++++++
> >  include/linux/fsverity.h     | 18 ++++++++++++++++
> >  4 files changed, 59 insertions(+), 7 deletions(-)
> > 
> > diff --git a/fs/verity/measure.c b/fs/verity/measure.c
> > index f0d7b30c62db..52906b2e5811 100644
> > --- a/fs/verity/measure.c
> > +++ b/fs/verity/measure.c
> > @@ -57,3 +57,43 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
> >  	return 0;
> >  }
> >  EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
> > +
> > +/**
> > + * fsverity_get_digest() - get a verity file's digest
> > + * @inode: inode to get digest of
> > + * @digest: (out) pointer to the digest
> > + * @alg: (out) pointer to the hash algorithm enumeration
> > + *
> > + * Return the file hash algorithm and digest of an fsverity protected file.
> > + *
> > + * Return: 0 on success, -errno on failure
> > + */
> > +int fsverity_get_digest(struct inode *inode,
> > +			    u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
> > +			    enum hash_algo *alg)
> > +{
> > +	const struct fsverity_info *vi;
> > +	const struct fsverity_hash_alg *hash_alg;
> > +	int i;
> > +
> > +	vi = fsverity_get_info(inode);
> > +	if (!vi)
> > +		return -ENODATA; /* not a verity file */
> > +
> > +	hash_alg = vi->tree_params.hash_alg;
> > +	memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
> > +	*alg = HASH_ALGO__LAST;
> 
> Perhaps this line is redundant (*alg is overwritten later) and would
> needlessly mangle output value in case of -EINVAL while it's being
> untouched on -ENODATA.
> 

Thanks!

Mimi

> 
> > +
> > +	/* convert hash algorithm to hash_algo_name */
> > +	i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
> > +	if (i < 0)
> > +		return -EINVAL;
> > +	*alg = i;
> > +
> > +	memcpy(digest, vi->file_digest, hash_alg->digest_size);
> > +
> > +	pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
> > +		  hash_digest_size[*alg], digest);
> > +
> > +	return 0;
> > +}
Eric Biggers Jan. 10, 2022, 10:15 p.m. UTC | #3
On Sun, Jan 09, 2022 at 01:55:13PM -0500, Mimi Zohar wrote:
> Define a function named fsverity_get_digest() to return the verity file
> digest and the associated hash algorithm (enum hash_algo).
> 
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---

Acked-by: Eric Biggers <ebiggers@google.com>

> +int fsverity_get_digest(struct inode *inode,
> +			    u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
> +			    enum hash_algo *alg)

There's some weird indentation here.

- Eric
diff mbox series

Patch

diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig
index 24d1b54de807..54598cd80145 100644
--- a/fs/verity/Kconfig
+++ b/fs/verity/Kconfig
@@ -3,6 +3,7 @@ 
 config FS_VERITY
 	bool "FS Verity (read-only file-based authenticity protection)"
 	select CRYPTO
+	select CRYPTO_HASH_INFO
 	# SHA-256 is implied as it's intended to be the default hash algorithm.
 	# To avoid bloat, other wanted algorithms must be selected explicitly.
 	# Note that CRYPTO_SHA256 denotes the generic C implementation, but
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index a7920434bae5..c6fb62e0ef1a 100644
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -14,7 +14,6 @@ 
 
 #define pr_fmt(fmt) "fs-verity: " fmt
 
-#include <crypto/sha2.h>
 #include <linux/fsverity.h>
 #include <linux/mempool.h>
 
@@ -26,12 +25,6 @@  struct ahash_request;
  */
 #define FS_VERITY_MAX_LEVELS		8
 
-/*
- * Largest digest size among all hash algorithms supported by fs-verity.
- * Currently assumed to be <= size of fsverity_descriptor::root_hash.
- */
-#define FS_VERITY_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
-
 /* A hash algorithm supported by fs-verity */
 struct fsverity_hash_alg {
 	struct crypto_ahash *tfm; /* hash tfm, allocated on demand */
diff --git a/fs/verity/measure.c b/fs/verity/measure.c
index f0d7b30c62db..52906b2e5811 100644
--- a/fs/verity/measure.c
+++ b/fs/verity/measure.c
@@ -57,3 +57,43 @@  int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
+
+/**
+ * fsverity_get_digest() - get a verity file's digest
+ * @inode: inode to get digest of
+ * @digest: (out) pointer to the digest
+ * @alg: (out) pointer to the hash algorithm enumeration
+ *
+ * Return the file hash algorithm and digest of an fsverity protected file.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int fsverity_get_digest(struct inode *inode,
+			    u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
+			    enum hash_algo *alg)
+{
+	const struct fsverity_info *vi;
+	const struct fsverity_hash_alg *hash_alg;
+	int i;
+
+	vi = fsverity_get_info(inode);
+	if (!vi)
+		return -ENODATA; /* not a verity file */
+
+	hash_alg = vi->tree_params.hash_alg;
+	memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
+	*alg = HASH_ALGO__LAST;
+
+	/* convert hash algorithm to hash_algo_name */
+	i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
+	if (i < 0)
+		return -EINVAL;
+	*alg = i;
+
+	memcpy(digest, vi->file_digest, hash_alg->digest_size);
+
+	pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
+		  hash_digest_size[*alg], digest);
+
+	return 0;
+}
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index b568b3c7d095..9a1b70cc7318 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -12,8 +12,16 @@ 
 #define _LINUX_FSVERITY_H
 
 #include <linux/fs.h>
+#include <crypto/hash_info.h>
+#include <crypto/sha2.h>
 #include <uapi/linux/fsverity.h>
 
+/*
+ * Largest digest size among all hash algorithms supported by fs-verity.
+ * Currently assumed to be <= size of fsverity_descriptor::root_hash.
+ */
+#define FS_VERITY_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
+
 /* Verity operations for filesystems */
 struct fsverity_operations {
 
@@ -131,6 +139,9 @@  int fsverity_ioctl_enable(struct file *filp, const void __user *arg);
 /* measure.c */
 
 int fsverity_ioctl_measure(struct file *filp, void __user *arg);
+int fsverity_get_digest(struct inode *inode,
+			u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
+			enum hash_algo *alg);
 
 /* open.c */
 
@@ -170,6 +181,13 @@  static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg)
 	return -EOPNOTSUPP;
 }
 
+static inline int fsverity_get_digest(struct inode *inode,
+				      u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
+				      enum hash_algo *alg)
+{
+	return -EOPNOTSUPP;
+}
+
 /* open.c */
 
 static inline int fsverity_file_open(struct inode *inode, struct file *filp)