From patchwork Fri Jan 15 18:18:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 12023775 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26299C433DB for ; Fri, 15 Jan 2021 18:21:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0097723A5A for ; Fri, 15 Jan 2021 18:21:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388077AbhAOSUy (ORCPT ); Fri, 15 Jan 2021 13:20:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:43466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732055AbhAOSUx (ORCPT ); Fri, 15 Jan 2021 13:20:53 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id BC9D823B03; Fri, 15 Jan 2021 18:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610734774; bh=gsd3qneQDJcEAWvK+26tVqknLPQ+kerh+7FxEp9mAvE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ChoMe9ho9PcGemgjTm2q12Bj6EiXXCXdgfNIY+rHRqA2eBl8pv5YGPzLH11U8uEPJ OVkenwHQw+fuoDIPVVZNU+2lQrYyiNpBkW7rLCxqwVzIHOoYoFRCVHL8aNS4+z1CB5 znTDLZehtUNRd6hUeqedT7eTp+XFuTC2m2VXmxUUBSruXBOzN8evT9crnLa2WhWbBd 481fhP5zXOwBby4Zs1ap2AsJDJJ3DB3SffV+wBcIssdTGz1LJ7aEyu2vjOMbFhxlkt tRt5FlgHNmQASBoSX82i8xkbTOzc0ndw/uIQp6f9p85nnPd74rc2Fp/6WOkHjWmbuE OratH61jn8whg== 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-api@vger.kernel.org, Theodore Ts'o , Jaegeuk Kim , Victor Hsieh Subject: [PATCH 4/6] fs-verity: support reading Merkle tree with ioctl Date: Fri, 15 Jan 2021 10:18:17 -0800 Message-Id: <20210115181819.34732-5-ebiggers@kernel.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210115181819.34732-1-ebiggers@kernel.org> References: <20210115181819.34732-1-ebiggers@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org From: Eric Biggers Add support for FS_VERITY_METADATA_TYPE_MERKLE_TREE to FS_IOC_READ_VERITY_METADATA. This allows a userspace server program to retrieve the Merkle tree 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. 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 Reviewed-by: Jaegeuk Kim --- Documentation/filesystems/fsverity.rst | 10 +++- fs/verity/read_metadata.c | 70 ++++++++++++++++++++++++++ include/uapi/linux/fsverity.h | 2 + 3 files changed, 81 insertions(+), 1 deletion(-) diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 9ef7a7de60085..50b47a6d9ea11 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -234,6 +234,8 @@ need this ioctl. This ioctl takes in a pointer to the following structure:: + #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 + struct fsverity_read_metadata_arg { __u64 metadata_type; __u64 offset; @@ -242,7 +244,13 @@ This ioctl takes in a pointer to the following structure:: __u64 __reserved; }; -``metadata_type`` specifies the type of metadata to read. +``metadata_type`` specifies the type of metadata to read: + +- ``FS_VERITY_METADATA_TYPE_MERKLE_TREE`` reads the blocks of the + Merkle tree. The blocks are returned in order from the root level + to the leaf level. Within each level, the blocks are returned in + the same order that their hashes are themselves hashed. + See `Merkle tree`_ for more information. The semantics are similar to those of ``pread()``. ``offset`` specifies the offset in bytes into the metadata item to read from, and diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c index 43be990fd53e4..0f8ad2991cf90 100644 --- a/fs/verity/read_metadata.c +++ b/fs/verity/read_metadata.c @@ -7,8 +7,75 @@ #include "fsverity_private.h" +#include +#include +#include #include +static int fsverity_read_merkle_tree(struct inode *inode, + const struct fsverity_info *vi, + void __user *buf, u64 offset, int length) +{ + const struct fsverity_operations *vops = inode->i_sb->s_vop; + u64 end_offset; + unsigned int offs_in_page; + pgoff_t index, last_index; + int retval = 0; + int err = 0; + + end_offset = min(offset + length, vi->tree_params.tree_size); + if (offset >= end_offset) + return 0; + offs_in_page = offset_in_page(offset); + last_index = (end_offset - 1) >> PAGE_SHIFT; + + /* + * Iterate through each Merkle tree page in the requested range and copy + * the requested portion to userspace. Note that the Merkle tree block + * size isn't important here, as we are returning a byte stream; i.e., + * we can just work with pages even if the tree block size != PAGE_SIZE. + */ + for (index = offset >> PAGE_SHIFT; index <= last_index; index++) { + unsigned long num_ra_pages = + min_t(unsigned long, last_index - index + 1, + inode->i_sb->s_bdi->io_pages); + unsigned int bytes_to_copy = min_t(u64, end_offset - offset, + PAGE_SIZE - offs_in_page); + struct page *page; + const void *virt; + + page = vops->read_merkle_tree_page(inode, index, num_ra_pages); + if (IS_ERR(page)) { + err = PTR_ERR(page); + fsverity_err(inode, + "Error %d reading Merkle tree page %lu", + err, index); + break; + } + + virt = kmap(page); + if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) { + kunmap(page); + put_page(page); + err = -EFAULT; + break; + } + kunmap(page); + put_page(page); + + retval += bytes_to_copy; + buf += bytes_to_copy; + offset += bytes_to_copy; + + if (fatal_signal_pending(current)) { + err = -EINTR; + break; + } + cond_resched(); + offs_in_page = 0; + } + return retval ? retval : err; +} /** * fsverity_ioctl_read_metadata() - read verity metadata from a file * @filp: file to read the metadata from @@ -48,6 +115,9 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) buf = u64_to_user_ptr(arg.buf_ptr); switch (arg.metadata_type) { + case FS_VERITY_METADATA_TYPE_MERKLE_TREE: + return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, + length); default: return -EINVAL; } diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index e062751294d01..94003b153cb3d 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -83,6 +83,8 @@ struct fsverity_formatted_digest { __u8 digest[]; }; +#define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 + struct fsverity_read_metadata_arg { __u64 metadata_type; __u64 offset;