From patchwork Fri Nov 13 21:19:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 11904593 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6E903138B for ; Fri, 13 Nov 2020 21:20:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E4062225D for ; Fri, 13 Nov 2020 21:20:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="108beoJR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726599AbgKMVUv (ORCPT ); Fri, 13 Nov 2020 16:20:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:40730 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726355AbgKMVUu (ORCPT ); Fri, 13 Nov 2020 16:20:50 -0500 Received: from sol.attlocal.net (172-10-235-113.lightspeed.sntcca.sbcglobal.net [172.10.235.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4CEEF22258; Fri, 13 Nov 2020 21:20:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605302449; bh=QjiQvf7g9yKcGU5m9aqGw/qrrLu6PiIemjru5rN3w4I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=108beoJREVHxUgHoAtZEL/NOxOzAcLAMUUBsn6UpyFKMRNKc0XRIkEMuCuaSWaXGU xlSrI1lShWwZca4wx9rocE2exuguVnpgoKYmYbwi7RmmHf4wjykNhwc3TsEIurbeBB a+P+H1wSGEjdfunncywOSdcfDI9WBnUGJxhqSfhE= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Victor Hsieh , Jes Sorensen , Luca Boccassi , Martijn Coenen , Paul Lawrence Subject: [PATCH 4/4] fs-verity: move structs needed for file signing to UAPI header Date: Fri, 13 Nov 2020 13:19:18 -0800 Message-Id: <20201113211918.71883-5-ebiggers@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201113211918.71883-1-ebiggers@kernel.org> References: <20201113211918.71883-1-ebiggers@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org From: Eric Biggers Although it isn't used directly by the ioctls, "struct fsverity_descriptor" is required by userspace programs that need to compute fs-verity file digests in a standalone way. Therefore it's also needed to sign files in a standalone way. Similarly, "struct fsverity_formatted_digest" (previously called "struct fsverity_signed_digest" which was misleading) is also needed to sign files if the built-in signature verification is being used. Therefore, move these structs to the UAPI header. While doing this, try to make it clear that the signature-related fields in fsverity_descriptor aren't used in the file digest computation. Signed-off-by: Eric Biggers Acked-by: Luca Boccassi --- Documentation/filesystems/fsverity.rst | 6 +--- fs/verity/fsverity_private.h | 37 ------------------- include/uapi/linux/fsverity.h | 49 ++++++++++++++++++++++++++ 3 files changed, 50 insertions(+), 42 deletions(-) diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 2eee558b7f5ff..e0204a23e997e 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -334,17 +334,13 @@ root hash as well as other fields such as the file size:: __u8 hash_algorithm; /* Merkle tree hash algorithm */ __u8 log_blocksize; /* log2 of size of data and tree blocks */ __u8 salt_size; /* size of salt in bytes; 0 if none */ - __le32 sig_size; /* must be 0 */ + __le32 __reserved_0x04; /* must be 0 */ __le64 data_size; /* size of file the Merkle tree is built over */ __u8 root_hash[64]; /* Merkle tree root hash */ __u8 salt[32]; /* salt prepended to each hashed block */ __u8 __reserved[144]; /* must be 0's */ }; -Note that the ``sig_size`` field must be set to 0 for the purpose of -computing the file measurement, even if a signature was provided (or -will be provided) to `FS_IOC_ENABLE_VERITY`_. - Built-in signature verification =============================== diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h index 21e9930d65fbd..96f7b332f54f5 100644 --- a/fs/verity/fsverity_private.h +++ b/fs/verity/fsverity_private.h @@ -77,49 +77,12 @@ struct fsverity_info { const struct inode *inode; }; -/* - * Merkle tree properties. The fs-verity file digest is the hash of this - * structure excluding the signature and with the sig_size field set to 0. - */ -struct fsverity_descriptor { - __u8 version; /* must be 1 */ - __u8 hash_algorithm; /* Merkle tree hash algorithm */ - __u8 log_blocksize; /* log2 of size of data and tree blocks */ - __u8 salt_size; /* size of salt in bytes; 0 if none */ - __le32 sig_size; /* size of signature in bytes; 0 if none */ - __le64 data_size; /* size of file the Merkle tree is built over */ - __u8 root_hash[64]; /* Merkle tree root hash */ - __u8 salt[32]; /* salt prepended to each hashed block */ - __u8 __reserved[144]; /* must be 0's */ - __u8 signature[]; /* optional PKCS#7 signature */ -}; - /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ sizeof(struct fsverity_descriptor)) -/* - * Format in which fs-verity file digests are signed in built-in signatures. - * This is the same as 'struct fsverity_digest', except here some magic bytes - * are prepended to provide some context about what is being signed in case the - * same key is used for non-fsverity purposes, and here the fields have fixed - * endianness. - * - * This struct is specific to the built-in signature verification support, which - * is optional. fs-verity users may also verify signatures in userspace, in - * which case userspace is responsible for deciding on what bytes are signed. - * This struct may still be used, but it doesn't have to be. For example, - * userspace could instead use a string like "sha256:$digest_as_hex_string". - */ -struct fsverity_formatted_digest { - char magic[8]; /* must be "FSVerity" */ - __le16 digest_algorithm; - __le16 digest_size; - __u8 digest[]; -}; - /* hash_algs.c */ extern struct fsverity_hash_alg fsverity_hash_algs[]; diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index da0daf6c193b4..260017a4b44b3 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -34,6 +34,55 @@ struct fsverity_digest { __u8 digest[]; }; +/* + * Struct containing a file's Merkle tree properties. The fs-verity file digest + * is the hash of this struct. A userspace program needs this struct only if it + * needs to compute fs-verity file digests itself, e.g. in order to sign files. + * It isn't needed just to enable fs-verity on a file. + * + * Note: when computing the file digest, 'sig_size' and 'signature' must be left + * zero and empty, respectively. These fields are present only because some + * filesystems reuse this struct as part of their on-disk format. + */ +struct fsverity_descriptor { + __u8 version; /* must be 1 */ + __u8 hash_algorithm; /* Merkle tree hash algorithm */ + __u8 log_blocksize; /* log2 of size of data and tree blocks */ + __u8 salt_size; /* size of salt in bytes; 0 if none */ +#ifdef __KERNEL__ + __le32 sig_size; +#else + __le32 __reserved_0x04; +#endif + __le64 data_size; /* size of file the Merkle tree is built over */ + __u8 root_hash[64]; /* Merkle tree root hash */ + __u8 salt[32]; /* salt prepended to each hashed block */ + __u8 __reserved[144]; /* must be 0's */ +#ifdef __KERNEL__ + __u8 signature[]; +#endif +}; + +/* + * Format in which fs-verity file digests are signed in built-in signatures. + * This is the same as 'struct fsverity_digest', except here some magic bytes + * are prepended to provide some context about what is being signed in case the + * same key is used for non-fsverity purposes, and here the fields have fixed + * endianness. + * + * This struct is specific to the built-in signature verification support, which + * is optional. fs-verity users may also verify signatures in userspace, in + * which case userspace is responsible for deciding on what bytes are signed. + * This struct may still be used, but it doesn't have to be. For example, + * userspace could instead use a string like "sha256:$digest_as_hex_string". + */ +struct fsverity_formatted_digest { + char magic[8]; /* must be "FSVerity" */ + __le16 digest_algorithm; + __le16 digest_size; + __u8 digest[]; +}; + #define FS_IOC_ENABLE_VERITY _IOW('f', 133, struct fsverity_enable_arg) #define FS_IOC_MEASURE_VERITY _IOWR('f', 134, struct fsverity_digest)