From: Eric Biggers <ebiggers@kernel.org>
To: linux-fscrypt@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-integrity@vger.kernel.org, linux-api@vger.kernel.org,
"Theodore Y . Ts'o" <tytso@mit.edu>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Victor Hsieh <victorhsieh@google.com>
Subject: [PATCH v3 10/15] fs-verity: implement FS_IOC_MEASURE_VERITY ioctl
Date: Thu, 23 May 2019 09:18:06 -0700 [thread overview]
Message-ID: <20190523161811.6259-11-ebiggers@kernel.org> (raw)
In-Reply-To: <20190523161811.6259-1-ebiggers@kernel.org>
From: Eric Biggers <ebiggers@google.com>
Add a function for filesystems to call to implement the
FS_IOC_MEASURE_VERITY ioctl. This ioctl retrieves the file measurement
that fs-verity calculated for the given file and is enforcing for reads;
i.e., reads that don't match this hash will fail. This ioctl can be
used for authentication or logging of file measurements in userspace.
See the "FS_IOC_MEASURE_VERITY" section of
Documentation/filesystems/fsverity.rst for the documentation.
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/verity/Makefile | 1 +
fs/verity/measure.c | 57 ++++++++++++++++++++++++++++++++++++++++
include/linux/fsverity.h | 11 ++++++++
3 files changed, 69 insertions(+)
create mode 100644 fs/verity/measure.c
diff --git a/fs/verity/Makefile b/fs/verity/Makefile
index 04b37475fd280..6f7675ae0a311 100644
--- a/fs/verity/Makefile
+++ b/fs/verity/Makefile
@@ -3,5 +3,6 @@
obj-$(CONFIG_FS_VERITY) += enable.o \
hash_algs.o \
init.o \
+ measure.o \
open.o \
verify.o
diff --git a/fs/verity/measure.c b/fs/verity/measure.c
new file mode 100644
index 0000000000000..f29557c0ee3da
--- /dev/null
+++ b/fs/verity/measure.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/verity/measure.c: ioctl to get a verity file's measurement
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include "fsverity_private.h"
+
+#include <linux/uaccess.h>
+
+/**
+ * fsverity_ioctl_measure() - get a verity file's measurement
+ *
+ * Retrieve the file measurement 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
+ */
+int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
+{
+ const struct inode *inode = file_inode(filp);
+ struct fsverity_digest __user *uarg = _uarg;
+ const struct fsverity_info *vi;
+ const struct fsverity_hash_alg *hash_alg;
+ struct fsverity_digest arg;
+
+ vi = get_verity_info(inode);
+ if (!vi)
+ return -ENODATA; /* not a verity file */
+ hash_alg = vi->tree_params.hash_alg;
+
+ /*
+ * The user specifies the digest_size their buffer has space for; we can
+ * return the digest if it fits in the available space. We write back
+ * the actual size, which may be shorter than the user-specified size.
+ */
+
+ if (get_user(arg.digest_size, &uarg->digest_size))
+ return -EFAULT;
+ if (arg.digest_size < hash_alg->digest_size)
+ return -EOVERFLOW;
+
+ memset(&arg, 0, sizeof(arg));
+ arg.digest_algorithm = hash_alg - fsverity_hash_algs;
+ arg.digest_size = hash_alg->digest_size;
+
+ if (copy_to_user(uarg, &arg, sizeof(arg)))
+ return -EFAULT;
+
+ if (copy_to_user(uarg->digest, vi->measurement, hash_alg->digest_size))
+ return -EFAULT;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 9a84fe4bcfc88..df0b620c6897f 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -110,6 +110,10 @@ struct fsverity_operations {
extern int fsverity_ioctl_enable(struct file *filp, const void __user *arg);
+/* measure.c */
+
+extern int fsverity_ioctl_measure(struct file *filp, void __user *arg);
+
/* open.c */
extern int fsverity_file_open(struct inode *inode, struct file *filp);
@@ -132,6 +136,13 @@ static inline int fsverity_ioctl_enable(struct file *filp,
return -EOPNOTSUPP;
}
+/* measure.c */
+
+static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg)
+{
+ return -EOPNOTSUPP;
+}
+
/* open.c */
static inline int fsverity_file_open(struct inode *inode, struct file *filp)
--
2.21.0
next prev parent reply other threads:[~2019-05-23 16:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-23 16:17 [PATCH v3 00/15] fs-verity: read-only file-based authenticity protection Eric Biggers
2019-05-23 16:17 ` [PATCH v3 01/15] fs-verity: add a documentation file Eric Biggers
2019-05-23 16:17 ` [PATCH v3 02/15] fs-verity: add MAINTAINERS file entry Eric Biggers
2019-05-23 16:17 ` [PATCH v3 03/15] fs-verity: add UAPI header Eric Biggers
2019-05-23 16:18 ` [PATCH v3 04/15] fs-verity: add Kconfig and the helper functions for hashing Eric Biggers
2019-05-23 16:18 ` [PATCH v3 05/15] fs-verity: add inode and superblock fields Eric Biggers
2019-05-23 16:18 ` [PATCH v3 06/15] fs-verity: add the hook for file ->open() Eric Biggers
2019-05-23 16:18 ` [PATCH v3 07/15] fs-verity: add the hook for file ->setattr() Eric Biggers
2019-05-23 16:18 ` [PATCH v3 08/15] fs-verity: add data verification hooks for ->readpages() Eric Biggers
2019-05-23 16:18 ` [PATCH v3 09/15] fs-verity: implement FS_IOC_ENABLE_VERITY ioctl Eric Biggers
2019-05-23 16:18 ` Eric Biggers [this message]
2019-05-23 16:18 ` [PATCH v3 11/15] fs-verity: add SHA-512 support Eric Biggers
2019-05-23 16:18 ` [PATCH v3 12/15] fs-verity: support builtin file signatures Eric Biggers
2019-05-23 16:18 ` [PATCH v3 13/15] ext4: add basic fs-verity support Eric Biggers
2019-05-23 16:18 ` [PATCH v3 14/15] ext4: add fs-verity read support Eric Biggers
2019-05-23 16:18 ` [PATCH v3 15/15] f2fs: add fs-verity support Eric Biggers
2019-05-30 18:54 ` [PATCH v3 00/15] fs-verity: read-only file-based authenticity protection Eric Biggers
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