From mboxrd@z Thu Jan 1 00:00:00 1970 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=-16.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 C1B65C10F0B for ; Tue, 26 Feb 2019 21:50:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E2BB21873 for ; Tue, 26 Feb 2019 21:50:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="M0pghNy1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729089AbfBZVuo (ORCPT ); Tue, 26 Feb 2019 16:50:44 -0500 Received: from mail-io1-f74.google.com ([209.85.166.74]:50664 "EHLO mail-io1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728766AbfBZVuo (ORCPT ); Tue, 26 Feb 2019 16:50:44 -0500 Received: by mail-io1-f74.google.com with SMTP id d7so11380012ios.17 for ; Tue, 26 Feb 2019 13:50:43 -0800 (PST) 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=OrLpVbFrhqHDu/nyMeqzGxF462Au6CRl2ys6e5+Fmlc=; b=M0pghNy1IQHmsn3LwD2Rcupn1ATT8/1wGNHkMW9MAWjSBSLDvTiaRdLeXMYpwV+7WD jSLN5JxVQV7bsATkpBQTv+/5fmChgvq/z1uPIRBoBLou23Fjlr6nXL6L6z1fcs3vnE+i oXR0uUWVHDs/rrMjZ7zUPmjMSDK3lTBFZCvGmiAozC9gq1IHzO4+esKKscVmTOiqFo0u fbRgYPr3rEQcvIzALTLF8MywzJJvAvgp4ZpMWI39RXnbAe1FDwKLCWnWsdU+FktpFxDo DlQ5uLlkfw8VSkg9bpX0X3dXkm15u6YVl3ezMs5qMordxE3TrTfKkkOxYTlflREAs5wr 3eQQ== 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=OrLpVbFrhqHDu/nyMeqzGxF462Au6CRl2ys6e5+Fmlc=; b=EZZ/mkbzwV9t23vjnuB4guBfB3++KJpAWS83uk9IbgEZ8vxsTtUx8zT0/CL31BJ5l3 j7jbUVOHASHlvUYqtPYA7zaETN0y+FHd7koCcMv2p6/SWGH2aeWmBHcacZ+60WWbo48+ xnG4PnIVnoT2d2rPhBUO+W9sQP282nvlEswUXWbnKIJ7kQGfgTEhtK6P+AGfem5Vm5Be xesUK4kjNNUT1BxKGbByUcp2F/VZ+yXABCHGSQQuJl/MYR7y4QG3FsDRXAhtJVoVHATr aTgWYFFiYnyyhWFhiCSpqUYdH9Gs0o3aPfsON6VBNF7y/YulUi/exIqsAv3VzVwMKoDQ 6P4g== X-Gm-Message-State: AHQUAuZqKjWcV6NMyZcPqnEBNpMG6VpDCTCaEk47ls6x9skNwwoodfQn GawRQKRAAsU6y3UHXpcOH1/UFSTZ8dVoLajYq4sSXw== X-Google-Smtp-Source: AHgI3IZbVD7NCGm3UXQ5pHDo2aRoNP9MyW1XXkOooFu5JiDCKU/A+poA+djdpw+M0YUSl/X/+PykqMmaDaCNfYuTJkaAZw== X-Received: by 2002:a24:220a:: with SMTP id o10mr3938734ito.22.1551217843625; Tue, 26 Feb 2019 13:50:43 -0800 (PST) Date: Tue, 26 Feb 2019 13:50:31 -0800 In-Reply-To: <20190226215034.68772-1-matthewgarrett@google.com> Message-Id: <20190226215034.68772-2-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190226215034.68772-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.21.0.rc2.261.ga7da99ff1b-goog Subject: [PATCH V2 1/4] VFS: Add a call to obtain a file's hash From: Matthew Garrett To: linux-integrity@vger.kernel.org Cc: zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, linux-fsdevel@vger.kernel.org, miklos@szeredi.hu, Matthew Garrett Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 ff3c5e6f87cf..2b86f912be34 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -2150,3 +2150,27 @@ 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 29d8e2cfed0e..c6de2855cfdb 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -40,6 +40,7 @@ #include #include +#include struct backing_dev_info; struct bdi_writeback; @@ -1819,6 +1820,8 @@ 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 { @@ -1895,7 +1898,8 @@ 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); -- 2.21.0.rc2.261.ga7da99ff1b-goog