| Message ID | 20190620205043.64350-12-ebiggers@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fs-verity: read-only file-based authenticity protection | expand |
On 06/20, Eric Biggers wrote: > 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. > > Reviewed-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> > 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 04b37475fd280a..6f7675ae0a3110 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 00000000000000..05049b68c74553 > --- /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 = fsverity_get_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 7ef2ef82653409..247359c86b72e0 100644 > --- a/include/linux/fsverity.h > +++ b/include/linux/fsverity.h > @@ -116,6 +116,10 @@ static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) > > 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); > @@ -143,6 +147,13 @@ 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) > -- > 2.22.0.410.gd8fdbe21b5-goog
diff --git a/fs/verity/Makefile b/fs/verity/Makefile index 04b37475fd280a..6f7675ae0a3110 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 00000000000000..05049b68c74553 --- /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 = fsverity_get_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 7ef2ef82653409..247359c86b72e0 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -116,6 +116,10 @@ static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) 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); @@ -143,6 +147,13 @@ 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)