| Message ID | 20210115181819.34732-6-ebiggers@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fs-verity: add an ioctl to read verity metadata | expand |
On 01/15, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > Add support for FS_VERITY_METADATA_TYPE_DESCRIPTOR to > FS_IOC_READ_VERITY_METADATA. This allows a userspace server program to > retrieve the fs-verity descriptor of a file for serving to a client > which implements fs-verity compatible verification. See the patch which > introduced FS_IOC_READ_VERITY_METADATA for more details. > > "fs-verity descriptor" here means only the part that userspace cares > about because it is hashed to produce the file digest. It doesn't > include the signature which ext4 and f2fs append to the > fsverity_descriptor struct when storing it on-disk, since that way of > storing the signature is an implementation detail. The next patch adds > a separate metadata_type value for retrieving the signature separately. > > This has been tested using a new xfstest which calls this ioctl via a > new subcommand for the 'fsverity' program from fsverity-utils. > > Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > Documentation/filesystems/fsverity.rst | 4 +++ > fs/verity/read_metadata.c | 40 ++++++++++++++++++++++++++ > include/uapi/linux/fsverity.h | 1 + > 3 files changed, 45 insertions(+) > > diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst > index 50b47a6d9ea11..6dc5772037ef9 100644 > --- a/Documentation/filesystems/fsverity.rst > +++ b/Documentation/filesystems/fsverity.rst > @@ -235,6 +235,7 @@ need this ioctl. > This ioctl takes in a pointer to the following structure:: > > #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 > + #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 > > struct fsverity_read_metadata_arg { > __u64 metadata_type; > @@ -252,6 +253,9 @@ This ioctl takes in a pointer to the following structure:: > the same order that their hashes are themselves hashed. > See `Merkle tree`_ for more information. > > +- ``FS_VERITY_METADATA_TYPE_DESCRIPTOR`` reads the fs-verity > + descriptor. See `fs-verity descriptor`_. > + > 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 > diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c > index 0f8ad2991cf90..2dea6dd3bb05a 100644 > --- a/fs/verity/read_metadata.c > +++ b/fs/verity/read_metadata.c > @@ -76,6 +76,44 @@ static int fsverity_read_merkle_tree(struct inode *inode, > } > return retval ? retval : err; > } > + > +/* Copy the requested portion of the buffer to userspace. */ > +static int fsverity_read_buffer(void __user *dst, u64 offset, int length, > + const void *src, size_t src_length) > +{ > + if (offset >= src_length) > + return 0; > + src += offset; > + src_length -= offset; > + > + length = min_t(size_t, length, src_length); > + > + if (copy_to_user(dst, src, length)) > + return -EFAULT; > + > + return length; > +} > + > +static int fsverity_read_descriptor(struct inode *inode, > + void __user *buf, u64 offset, int length) > +{ > + struct fsverity_descriptor *desc; > + size_t desc_size; > + int res; > + > + res = fsverity_get_descriptor(inode, &desc, &desc_size); > + if (res) > + return res; > + > + /* don't include the signature */ > + desc_size = offsetof(struct fsverity_descriptor, signature); > + desc->sig_size = 0; > + > + res = fsverity_read_buffer(buf, offset, length, desc, desc_size); > + > + kfree(desc); > + return res; > +} > /** > * fsverity_ioctl_read_metadata() - read verity metadata from a file > * @filp: file to read the metadata from > @@ -118,6 +156,8 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) > case FS_VERITY_METADATA_TYPE_MERKLE_TREE: > return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, > length); > + case FS_VERITY_METADATA_TYPE_DESCRIPTOR: > + return fsverity_read_descriptor(inode, buf, arg.offset, length); > default: > return -EINVAL; > } > diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h > index 94003b153cb3d..41abc283dbccb 100644 > --- a/include/uapi/linux/fsverity.h > +++ b/include/uapi/linux/fsverity.h > @@ -84,6 +84,7 @@ struct fsverity_formatted_digest { > }; > > #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 > +#define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 > > struct fsverity_read_metadata_arg { > __u64 metadata_type; > -- > 2.30.0
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 50b47a6d9ea11..6dc5772037ef9 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -235,6 +235,7 @@ need this ioctl. This ioctl takes in a pointer to the following structure:: #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 + #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 struct fsverity_read_metadata_arg { __u64 metadata_type; @@ -252,6 +253,9 @@ This ioctl takes in a pointer to the following structure:: the same order that their hashes are themselves hashed. See `Merkle tree`_ for more information. +- ``FS_VERITY_METADATA_TYPE_DESCRIPTOR`` reads the fs-verity + descriptor. See `fs-verity descriptor`_. + 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 diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c index 0f8ad2991cf90..2dea6dd3bb05a 100644 --- a/fs/verity/read_metadata.c +++ b/fs/verity/read_metadata.c @@ -76,6 +76,44 @@ static int fsverity_read_merkle_tree(struct inode *inode, } return retval ? retval : err; } + +/* Copy the requested portion of the buffer to userspace. */ +static int fsverity_read_buffer(void __user *dst, u64 offset, int length, + const void *src, size_t src_length) +{ + if (offset >= src_length) + return 0; + src += offset; + src_length -= offset; + + length = min_t(size_t, length, src_length); + + if (copy_to_user(dst, src, length)) + return -EFAULT; + + return length; +} + +static int fsverity_read_descriptor(struct inode *inode, + void __user *buf, u64 offset, int length) +{ + struct fsverity_descriptor *desc; + size_t desc_size; + int res; + + res = fsverity_get_descriptor(inode, &desc, &desc_size); + if (res) + return res; + + /* don't include the signature */ + desc_size = offsetof(struct fsverity_descriptor, signature); + desc->sig_size = 0; + + res = fsverity_read_buffer(buf, offset, length, desc, desc_size); + + kfree(desc); + return res; +} /** * fsverity_ioctl_read_metadata() - read verity metadata from a file * @filp: file to read the metadata from @@ -118,6 +156,8 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) case FS_VERITY_METADATA_TYPE_MERKLE_TREE: return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, length); + case FS_VERITY_METADATA_TYPE_DESCRIPTOR: + return fsverity_read_descriptor(inode, buf, arg.offset, length); default: return -EINVAL; } diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index 94003b153cb3d..41abc283dbccb 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -84,6 +84,7 @@ struct fsverity_formatted_digest { }; #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 +#define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 struct fsverity_read_metadata_arg { __u64 metadata_type;