Return-Path: Received: from mail.kernel.org ([198.145.29.99]:52160 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728078AbeKBH7R (ORCPT ); Fri, 2 Nov 2018 03:59:17 -0400 From: Eric Biggers 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-kernel@vger.kernel.org, "Theodore Y . Ts'o" , Jaegeuk Kim , Victor Hsieh , Chandan Rajendra Subject: [PATCH v2 06/12] fs-verity: implement FS_IOC_MEASURE_VERITY ioctl Date: Thu, 1 Nov 2018 15:52:24 -0700 Message-Id: <20181101225230.88058-7-ebiggers@kernel.org> In-Reply-To: <20181101225230.88058-1-ebiggers@kernel.org> References: <20181101225230.88058-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Eric Biggers Add a function for filesystems to call to implement the FS_IOC_MEASURE_VERITY ioctl. This ioctl retrieves the file measurement hash 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 logging or authentication of file hashes in userspace. This ioctl is documented in Documentation/filesystem/fsverity.rst; see there for more information. Signed-off-by: Eric Biggers --- fs/verity/ioctl.c | 47 ++++++++++++++++++++++++++++++++++++++++ fs/verity/setup.c | 4 +++- include/linux/fsverity.h | 6 +++++ 3 files changed, 56 insertions(+), 1 deletion(-) diff --git a/fs/verity/ioctl.c b/fs/verity/ioctl.c index c5f0022cb3bef..640aa78e1c00c 100644 --- a/fs/verity/ioctl.c +++ b/fs/verity/ioctl.c @@ -115,3 +115,50 @@ int fsverity_ioctl_enable(struct file *filp, const void __user *arg) return err; } EXPORT_SYMBOL_GPL(fsverity_ioctl_enable); + +/** + * 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 Documentation/filesystems/fsverity.rst, section + * 'FS_IOC_MEASURE_VERITY' for details. + * + * 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_fsverity_info(inode); + if (!vi) + return -ENODATA; /* not a verity file */ + hash_alg = vi->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/fs/verity/setup.c b/fs/verity/setup.c index 184bdc96abe51..e0b39c518b890 100644 --- a/fs/verity/setup.c +++ b/fs/verity/setup.c @@ -819,7 +819,9 @@ static int __init fsverity_module_init(void) goto error; err = -ENOMEM; - fsverity_info_cachep = KMEM_CACHE(fsverity_info, SLAB_RECLAIM_ACCOUNT); + fsverity_info_cachep = KMEM_CACHE_USERCOPY(fsverity_info, + SLAB_RECLAIM_ACCOUNT, + measurement); if (!fsverity_info_cachep) goto error_free_workqueue; diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index 5de50b52ccc70..c30c4f6ed411c 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -23,6 +23,7 @@ struct fsverity_operations { /* ioctl.c */ extern int fsverity_ioctl_enable(struct file *filp, const void __user *arg); +extern int fsverity_ioctl_measure(struct file *filp, void __user *arg); /* setup.c */ extern int fsverity_file_open(struct inode *inode, struct file *filp); @@ -51,6 +52,11 @@ static inline int fsverity_ioctl_enable(struct file *filp, return -EOPNOTSUPP; } +static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + /* setup.c */ static inline int fsverity_file_open(struct inode *inode, struct file *filp) -- 2.19.1.568.g152ad8e336-goog