From patchwork Fri May 17 21:24:43 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 10948621 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DDAD5933 for ; Fri, 17 May 2019 21:24:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CBF2D2847D for ; Fri, 17 May 2019 21:24:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BD5782847A; Fri, 17 May 2019 21:24:58 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 414B12847A for ; Fri, 17 May 2019 21:24:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727816AbfEQVY6 (ORCPT ); Fri, 17 May 2019 17:24:58 -0400 Received: from mail-yb1-f202.google.com ([209.85.219.202]:33892 "EHLO mail-yb1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727474AbfEQVY5 (ORCPT ); Fri, 17 May 2019 17:24:57 -0400 Received: by mail-yb1-f202.google.com with SMTP id b82so7372075yba.1 for ; Fri, 17 May 2019 14:24:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=APRT6LEPqixBvHano+viVPqM6dMjKu1ogq3RkP5nfIs=; b=aQGynE/2Ct9KNtAZ5iXBB7Jw62upUkAAyczhhJA2F2czqiQLh5wh9ZmTZ5mdlePYNW 7Q2l38wyOVWIApdmBcxAMtIrAymD+NglINpMls/Kdy0g5QIlyE8eSjjdDcnZFhgq967e Fy2OWQajtivBBaDPOHJOu1hVM5zn38CSqqq/wtOqyPLhTlCHffHTk5yB/O8qMLjnfiDj tneN6ddq1ojgYtZPEs34VwLam+ZAeHQV5/+rVb2RvxpDlHs6E95TpD1GltdHSms2k08y tGJ9EcZT40MUmHTOE7+C+psQM8srkuGOYH+1esnAYAtmwgChEZqTpGueKDGXdRQ46EIN RD5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=APRT6LEPqixBvHano+viVPqM6dMjKu1ogq3RkP5nfIs=; b=fnB+VHMejPJtCs+MTQr4s5vV1bKp4gKoCXwUObWTdMKS1Ti18DaFdLImekLzjys00Z c6Rddh3nzx7mnxDxFDrBElgIk/iAPLXDd5wm8awqXejFIjdkA+YJrfTxXy7i8p7HPKx8 VFzvQ+/JNPcrcXtPd2m3zs3BSnN3DD+LzFruNz8C/NWQjnblKfiWe9VPp+ElICOo5mfm MYLkjoRMsXovIWYXLHUhOsDd9IJoP52sKnBs4aWngg2CEuIwmONF/Dl+4XD8Wr58IEv5 +yANBjplxnqwUZNC9oRWQ2UwxOnURJ0grMO4vWNMkjPtaEMLgnNrc/RLtLomjuk+Hkq5 1VeA== X-Gm-Message-State: APjAAAUQsfMhn1EVHuyECSufGtv/vns4OdbSo8CYfmIywUsHxZ20w6Dz rV/qanDAuOFlkbWpN/XAtZdc/CFENMk4RwofRM8xpnWKb6cwbn8TxLTw3bKf1l1PHLjHPzBUHH3 lcj17wrfEi/ELuST6TzGPg66fZY5cSEgnYoHaKvdnq17nC7inxfzgBBck78upvktYyQP3zJ2Mwd 5a0AfCqQIDIsC6Y/wPVos= X-Google-Smtp-Source: APXvYqz8FZKK/R4raVavRFrW36HXdCWJ+9zF2vh1ttYxP1/usjMDW20DfxgQgYrPzK6jQWhBLwEqmk7fErV5wuX5TcKCNw== X-Received: by 2002:a81:2717:: with SMTP id n23mr29712693ywn.511.1558128297020; Fri, 17 May 2019 14:24:57 -0700 (PDT) Date: Fri, 17 May 2019 14:24:43 -0700 In-Reply-To: <20190517212448.14256-1-matthewgarrett@google.com> Message-Id: <20190517212448.14256-2-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190517212448.14256-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.21.0.1020.gf2820cf01a-goog Subject: [PATCH V3 1/6] VFS: Add a call to obtain a file's hash From: Matthew Garrett To: linux-integrity@vger.kernel.org Cc: zohar@linux.vnet.ibm.com, dmitry.kasatkin@gmail.com, miklos@szeredi.hu, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, Matthew Garrett Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Garrett IMA wants to know what the hash of a file is, and currently does so by reading the entire file and generating the hash. Some filesystems may have the ability to store the hash in a secure manner resistant to offline attacks (eg, filesystem-level file signing), and in that case it's a performance win for IMA to be able to use that rather than having to re-hash everything. This patch simply adds VFS-level support for calling down to filesystems. Signed-off-by: Matthew Garrett --- fs/read_write.c | 24 ++++++++++++++++++++++++ include/linux/fs.h | 6 +++++- 2 files changed, 29 insertions(+), 1 deletion(-) diff --git a/fs/read_write.c b/fs/read_write.c index 61b43ad7608e..3ba7038ba9a9 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -2157,3 +2157,27 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same) return ret; } EXPORT_SYMBOL(vfs_dedupe_file_range); + +/** + * vfs_gethash - obtain a file's hash + * @file: file structure in question + * @hash_algo: the hash algorithm requested + * @buf: buffer to return the hash in + * @size: size allocated for the buffer by the caller + * + * This function allows filesystems that support securely storing the hash + * of a file to return it rather than forcing the kernel to recalculate it. + * Filesystems that cannot provide guarantees about the hash being resistant + * to offline attack should not implement this functionality. + * + * Returns 0 on success, -EOPNOTSUPP if the filesystem doesn't support it. + */ +int vfs_get_hash(struct file *file, enum hash_algo hash, uint8_t *buf, + size_t size) +{ + if (!file->f_op->get_hash) + return -EOPNOTSUPP; + + return file->f_op->get_hash(file, hash, buf, size); +} +EXPORT_SYMBOL(vfs_get_hash); diff --git a/include/linux/fs.h b/include/linux/fs.h index dd28e7679089..211f0e214953 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -43,6 +43,7 @@ #include #include +#include struct backing_dev_info; struct bdi_writeback; @@ -1822,6 +1823,8 @@ struct file_operations { struct file *file_out, loff_t pos_out, loff_t len, unsigned int remap_flags); int (*fadvise)(struct file *, loff_t, loff_t, int); + int (*get_hash)(struct file *, enum hash_algo hash, uint8_t *buf, + size_t size); } __randomize_layout; struct inode_operations { @@ -1898,7 +1901,8 @@ extern int vfs_dedupe_file_range(struct file *file, extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos, struct file *dst_file, loff_t dst_pos, loff_t len, unsigned int remap_flags); - +extern int vfs_get_hash(struct file *file, enum hash_algo hash, uint8_t *buf, + size_t size); struct super_operations { struct inode *(*alloc_inode)(struct super_block *sb);