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authorEric Biggers <ebiggers@google.com>2021-01-15 10:18:19 -0800
committerEric Biggers <ebiggers@google.com>2021-02-07 14:51:19 -0800
commit07c99001312cbf90a357d4877a358f796eede65b (patch)
tree12c2787f495d8fdbf605e1fa1bbd835aa204458a /fs/verity
parent947191ac8caba85e25e0e036b0f097fee9e817f3 (diff)
fs-verity: support reading signature with ioctl
Add support for FS_VERITY_METADATA_TYPE_SIGNATURE to FS_IOC_READ_VERITY_METADATA. This allows a userspace server program to retrieve the built-in signature (if present) of a verity 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. The ability for userspace to read the built-in signatures is also useful because it allows a system that is using the in-kernel signature verification to migrate to userspace signature verification. This has been tested using a new xfstest which calls this ioctl via a new subcommand for the 'fsverity' program from fsverity-utils. Link: https://lore.kernel.org/r/20210115181819.34732-7-ebiggers@kernel.org Reviewed-by: Victor Hsieh <victorhsieh@google.com> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Reviewed-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/verity')
-rw-r--r--fs/verity/read_metadata.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c
index 2dea6dd3bb05..7e2d0c7bdf0d 100644
--- a/fs/verity/read_metadata.c
+++ b/fs/verity/read_metadata.c
@@ -114,6 +114,34 @@ static int fsverity_read_descriptor(struct inode *inode,
kfree(desc);
return res;
}
+
+static int fsverity_read_signature(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;
+
+ if (desc->sig_size == 0) {
+ res = -ENODATA;
+ goto out;
+ }
+
+ /*
+ * Include only the signature. Note that fsverity_get_descriptor()
+ * already verified that sig_size is in-bounds.
+ */
+ res = fsverity_read_buffer(buf, offset, length, desc->signature,
+ le32_to_cpu(desc->sig_size));
+out:
+ kfree(desc);
+ return res;
+}
+
/**
* fsverity_ioctl_read_metadata() - read verity metadata from a file
* @filp: file to read the metadata from
@@ -158,6 +186,8 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg)
length);
case FS_VERITY_METADATA_TYPE_DESCRIPTOR:
return fsverity_read_descriptor(inode, buf, arg.offset, length);
+ case FS_VERITY_METADATA_TYPE_SIGNATURE:
+ return fsverity_read_signature(inode, buf, arg.offset, length);
default:
return -EINVAL;
}