diff options
| -rw-r--r-- | Documentation/filesystems/fsverity.rst | 57 | ||||
| -rw-r--r-- | fs/ext4/ioctl.c | 7 | ||||
| -rw-r--r-- | fs/f2fs/file.c | 11 | ||||
| -rw-r--r-- | fs/verity/Makefile | 1 | ||||
| -rw-r--r-- | fs/verity/read_metadata.c | 55 | ||||
| -rw-r--r-- | include/linux/fsverity.h | 12 | ||||
| -rw-r--r-- | include/uapi/linux/fsverity.h | 10 |
7 files changed, 153 insertions, 0 deletions
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index e0204a23e997..9ef7a7de6008 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -217,6 +217,63 @@ FS_IOC_MEASURE_VERITY can fail with the following errors: - ``EOVERFLOW``: the digest is longer than the specified ``digest_size`` bytes. Try providing a larger buffer. +FS_IOC_READ_VERITY_METADATA +--------------------------- + +The FS_IOC_READ_VERITY_METADATA ioctl reads verity metadata from a +verity file. This ioctl is available since Linux v5.12. + +This ioctl allows writing a server program that takes a verity file +and serves it to a client program, such that the client can do its own +fs-verity compatible verification of the file. This only makes sense +if the client doesn't trust the server and if the server needs to +provide the storage for the client. + +This is a fairly specialized use case, and most fs-verity users won't +need this ioctl. + +This ioctl takes in a pointer to the following structure:: + + struct fsverity_read_metadata_arg { + __u64 metadata_type; + __u64 offset; + __u64 length; + __u64 buf_ptr; + __u64 __reserved; + }; + +``metadata_type`` specifies the type of metadata to read. + +The semantics are similar to those of ``pread()``. ``offset`` +specifies the offset in bytes into the metadata item to read from, and +``length`` specifies the maximum number of bytes to read from the +metadata item. ``buf_ptr`` is the pointer to the buffer to read into, +cast to a 64-bit integer. ``__reserved`` must be 0. On success, the +number of bytes read is returned. 0 is returned at the end of the +metadata item. The returned length may be less than ``length``, for +example if the ioctl is interrupted. + +The metadata returned by FS_IOC_READ_VERITY_METADATA isn't guaranteed +to be authenticated against the file digest that would be returned by +`FS_IOC_MEASURE_VERITY`_, as the metadata is expected to be used to +implement fs-verity compatible verification anyway (though absent a +malicious disk, the metadata will indeed match). E.g. to implement +this ioctl, the filesystem is allowed to just read the Merkle tree +blocks from disk without actually verifying the path to the root node. + +FS_IOC_READ_VERITY_METADATA can fail with the following errors: + +- ``EFAULT``: the caller provided inaccessible memory +- ``EINTR``: the ioctl was interrupted before any data was read +- ``EINVAL``: reserved fields were set, or ``offset + length`` + overflowed +- ``ENODATA``: the file is not a verity file +- ``ENOTTY``: this type of filesystem does not implement fs-verity, or + this ioctl is not yet implemented on it +- ``EOPNOTSUPP``: the kernel was not configured with fs-verity + support, or the filesystem superblock has not had the 'verity' + feature enabled on it. (See `Filesystem support`_.) + FS_IOC_GETFLAGS --------------- diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index d9665d2f82db..713b1ae44c1a 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1309,6 +1309,12 @@ out: return -EOPNOTSUPP; return fsverity_ioctl_measure(filp, (void __user *)arg); + case FS_IOC_READ_VERITY_METADATA: + if (!ext4_has_feature_verity(sb)) + return -EOPNOTSUPP; + return fsverity_ioctl_read_metadata(filp, + (const void __user *)arg); + default: return -ENOTTY; } @@ -1391,6 +1397,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case FS_IOC_GETFSMAP: case FS_IOC_ENABLE_VERITY: case FS_IOC_MEASURE_VERITY: + case FS_IOC_READ_VERITY_METADATA: case EXT4_IOC_CLEAR_ES_CACHE: case EXT4_IOC_GETSTATE: case EXT4_IOC_GET_ES_CACHE: diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index f585545277d7..d0aefb5b97fa 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -3357,6 +3357,14 @@ static int f2fs_ioc_measure_verity(struct file *filp, unsigned long arg) return fsverity_ioctl_measure(filp, (void __user *)arg); } +static int f2fs_ioc_read_verity_metadata(struct file *filp, unsigned long arg) +{ + if (!f2fs_sb_has_verity(F2FS_I_SB(file_inode(filp)))) + return -EOPNOTSUPP; + + return fsverity_ioctl_read_metadata(filp, (const void __user *)arg); +} + static int f2fs_ioc_getfslabel(struct file *filp, unsigned long arg) { struct inode *inode = file_inode(filp); @@ -4272,6 +4280,8 @@ static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) return f2fs_ioc_enable_verity(filp, arg); case FS_IOC_MEASURE_VERITY: return f2fs_ioc_measure_verity(filp, arg); + case FS_IOC_READ_VERITY_METADATA: + return f2fs_ioc_read_verity_metadata(filp, arg); case FS_IOC_GETFSLABEL: return f2fs_ioc_getfslabel(filp, arg); case FS_IOC_SETFSLABEL: @@ -4523,6 +4533,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case F2FS_IOC_RESIZE_FS: case FS_IOC_ENABLE_VERITY: case FS_IOC_MEASURE_VERITY: + case FS_IOC_READ_VERITY_METADATA: case FS_IOC_GETFSLABEL: case FS_IOC_SETFSLABEL: case F2FS_IOC_GET_COMPRESS_BLOCKS: diff --git a/fs/verity/Makefile b/fs/verity/Makefile index 570e9136334d..435559a4fa9e 100644 --- a/fs/verity/Makefile +++ b/fs/verity/Makefile @@ -5,6 +5,7 @@ obj-$(CONFIG_FS_VERITY) += enable.o \ init.o \ measure.o \ open.o \ + read_metadata.o \ verify.o obj-$(CONFIG_FS_VERITY_BUILTIN_SIGNATURES) += signature.o diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c new file mode 100644 index 000000000000..43be990fd53e --- /dev/null +++ b/fs/verity/read_metadata.c @@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Ioctl to read verity metadata + * + * Copyright 2021 Google LLC + */ + +#include "fsverity_private.h" + +#include <linux/uaccess.h> + +/** + * fsverity_ioctl_read_metadata() - read verity metadata from a file + * @filp: file to read the metadata from + * @uarg: user pointer to fsverity_read_metadata_arg + * + * Return: length read on success, 0 on EOF, -errno on failure + */ +int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) +{ + struct inode *inode = file_inode(filp); + const struct fsverity_info *vi; + struct fsverity_read_metadata_arg arg; + int length; + void __user *buf; + + vi = fsverity_get_info(inode); + if (!vi) + return -ENODATA; /* not a verity file */ + /* + * Note that we don't have to explicitly check that the file is open for + * reading, since verity files can only be opened for reading. + */ + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (arg.__reserved) + return -EINVAL; + + /* offset + length must not overflow. */ + if (arg.offset + arg.length < arg.offset) + return -EINVAL; + + /* Ensure that the return value will fit in INT_MAX. */ + length = min_t(u64, arg.length, INT_MAX); + + buf = u64_to_user_ptr(arg.buf_ptr); + + switch (arg.metadata_type) { + default: + return -EINVAL; + } +} +EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata); diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index c1144a450392..b568b3c7d095 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -138,6 +138,10 @@ int fsverity_file_open(struct inode *inode, struct file *filp); int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); void fsverity_cleanup_inode(struct inode *inode); +/* read_metadata.c */ + +int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg); + /* verify.c */ bool fsverity_verify_page(struct page *page); @@ -183,6 +187,14 @@ static inline void fsverity_cleanup_inode(struct inode *inode) { } +/* read_metadata.c */ + +static inline int fsverity_ioctl_read_metadata(struct file *filp, + const void __user *uarg) +{ + return -EOPNOTSUPP; +} + /* verify.c */ static inline bool fsverity_verify_page(struct page *page) diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index 33f44156f8ea..e062751294d0 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -83,7 +83,17 @@ struct fsverity_formatted_digest { __u8 digest[]; }; +struct fsverity_read_metadata_arg { + __u64 metadata_type; + __u64 offset; + __u64 length; + __u64 buf_ptr; + __u64 __reserved; +}; + #define FS_IOC_ENABLE_VERITY _IOW('f', 133, struct fsverity_enable_arg) #define FS_IOC_MEASURE_VERITY _IOWR('f', 134, struct fsverity_digest) +#define FS_IOC_READ_VERITY_METADATA \ + _IOWR('f', 135, struct fsverity_read_metadata_arg) #endif /* _UAPI_LINUX_FSVERITY_H */ |