From patchwork Fri May 24 23:04:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jaskaran Singh Khurana X-Patchwork-Id: 10960523 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 B2D3D933 for ; Fri, 24 May 2019 23:10:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A25DD28249 for ; Fri, 24 May 2019 23:10:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 96826289DA; Fri, 24 May 2019 23:10:25 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI 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 3894228249 for ; Fri, 24 May 2019 23:10:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732118AbfEXXKQ (ORCPT ); Fri, 24 May 2019 19:10:16 -0400 Received: from linux.microsoft.com ([13.77.154.182]:56400 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732029AbfEXXKQ (ORCPT ); Fri, 24 May 2019 19:10:16 -0400 Received: from jaskaran-Intel-Server-Board-S1200V3RPS-UEFI-Development-Kit.corp.microsoft.com (unknown [131.107.160.238]) by linux.microsoft.com (Postfix) with ESMTPSA id 0B2D720B7192; Fri, 24 May 2019 16:04:27 -0700 (PDT) From: Jaskaran Khurana To: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Cc: agk@redhat.com, snitzer@redhat.com, dm-devel@redhat.com, jmorris@namei.org, scottsh@microsoft.com Subject: [PATCH 0/1 v2] Add dm verity root hash pkcs7 sig validation. Date: Fri, 24 May 2019 16:04:10 -0700 Message-Id: <20190524230411.9238-1-jaskarankhurana@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP This patch set adds in-kernel pkcs7 signature checking for the roothash of the dm-verity hash tree. The verification is to support cases where the roothash is not secured by Trusted Boot, UEFI Secureboot or similar technologies. One of the use cases for this is for dm-verity volumes mounted after boot, the root hash provided during the creation of the dm-verity volume has to be secure and thus in-kernel validation implemented here will be used before we trust the root hash and allow the block device to be created. Why we are doing validation in the Kernel? The reason is to still be secure in cases where the attacker is able to compromise the user mode application in which case the user mode validation could not have been trusted. The root hash signature validation in the kernel along with existing dm-verity implementation gives a higher level of confidence in the executable code or the protected data. Before allowing the creation of the device mapper block device the kernel code will check that the detached pkcs7 signature passed to it validates the roothash and the signature is trusted by builtin keys set at kernel creation. The kernel should be secured using Verified boot, UEFI Secure Boot or similar technologies so we can trust it. What about attacker mounting non dm-verity volumes to run executable code? This verification can be used to have a security architecture where a LSM can enforce this verification for all the volumes and by doing this it can ensure that all executable code runs from signed and trusted dm-verity volumes. Further patches will be posted that build on this and enforce this verification based on policy for all the volumes on the system. How are these changes tested? veritysetup part of cryptsetup library was modified to take a optional root-hash-sig parameter. Commandline used to test the changes: veritysetup open --root-hash-sig= The changes for veritysetup are in a topic branch for now at: https://github.com/jaskarankhurana/veritysetup/tree/veritysetup_add_sig Changelog: v2: - Code review feedback to pass the signature binary blob as a key that can be looked up in the kernel and be used to verify the roothash. [Suggested by Milan Broz] - Made the code related change suggested in review of v1. [Suggested by Balbir Singh] v1: - Add kconfigs to control dm-verity root has signature verification and use the signature if specified to verify the root hash. Jaskaran Khurana (1): Adds in-kernel pkcs7 sig checking the roothash of the dm-verity hash tree drivers/md/Kconfig | 23 +++++ drivers/md/Makefile | 2 +- drivers/md/dm-verity-target.c | 34 +++++++- drivers/md/dm-verity-verify-sig.c | 137 ++++++++++++++++++++++++++++++ drivers/md/dm-verity-verify-sig.h | 31 +++++++ 5 files changed, 222 insertions(+), 5 deletions(-) create mode 100644 drivers/md/dm-verity-verify-sig.c create mode 100644 drivers/md/dm-verity-verify-sig.h