From patchwork Thu May 19 00:47:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 12854439 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91D84C433EF for ; Thu, 19 May 2022 00:48:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232271AbiESAsA (ORCPT ); Wed, 18 May 2022 20:48:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231404AbiESAr6 (ORCPT ); Wed, 18 May 2022 20:47:58 -0400 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C726CF5BC for ; Wed, 18 May 2022 17:47:57 -0700 (PDT) Received: by mail-pf1-x42e.google.com with SMTP id c14so3704652pfn.2 for ; Wed, 18 May 2022 17:47:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0dmLJVwCa/DghSPPAq3/ILY1JgWX+nBsu5yiEOAQ9ss=; b=XMODawl+7/0Y5Xh+b7gsipx99R4vrMlDVUJhygLFG7mr2rmjqW84L/f6uhId0MVlCM +7YHF+QsNYi15C1v725aS6OaBX9ZEjzCjL+F41eoG4Hbu8LlXissF8hjPeLMSl9nNire 6tWIj/frqGlWx4+/gOTTDSdUVC5q88N9ooLdU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0dmLJVwCa/DghSPPAq3/ILY1JgWX+nBsu5yiEOAQ9ss=; b=CBpzXXh5dH/XRI1XeEJ7YjTGeT22nrRHGH3mUWLF6Z1V6qfy5N6b9bu7G23KSDpIt1 AW7bihDn+Yt963/9egf1IBltkzC6psqEUdUBbmlbd6XkMkIHVlypKvrS1L1Gvf4sf43o O2UsGNhMwvTSZbgXZI5Twe9W+uUXmxYPVAyEgeNG4J8BEtSUNzaYXN2ku00Q8TGgu9gr zdHd2Hk9Rd2GswsV0zOrzRoezmjMSyG/z7xAVZNAsu2xDyk5z0DdvZvzqPiABNkas2aW LCBOSpzetyvCxYxb2SvvGvTKjrAImprB4DonPtnq7QvbuBg79Ct6NlDFkmlHwdTDAd/7 E3TQ== X-Gm-Message-State: AOAM531SXvTtOFUD/5YhDCdWb5qbdT98U6TuCtUUIAuieKYXJRIWrpnf d5cz36L0w62DhFqEJhD+9SuJvw== X-Google-Smtp-Source: ABdhPJxPgVklbI1Lz7IgXdVY0Dozqllrmq/dawwTwH/MMyxvIe35uXRiIXra8YQiTvV2RUlZEyKpvA== X-Received: by 2002:a65:554a:0:b0:3f6:885:b291 with SMTP id t10-20020a65554a000000b003f60885b291mr1746494pgr.608.1652921277291; Wed, 18 May 2022 17:47:57 -0700 (PDT) Received: from localhost ([2620:15c:11a:202:e229:79ea:227e:d9dd]) by smtp.gmail.com with UTF8SMTPSA id u26-20020aa7839a000000b0050dc76281c2sm2515274pfm.156.2022.05.18.17.47.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 May 2022 17:47:56 -0700 (PDT) From: Matthias Kaehlcke To: Alasdair Kergon , Mike Snitzer , Kees Cook , James Morris , "Serge E . Hallyn" Cc: Song Liu , Douglas Anderson , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-raid@vger.kernel.org, dm-devel@redhat.com, Milan Broz , Matthias Kaehlcke Subject: [PATCH v5 0/3] LoadPin: Enable loading from trusted dm-verity devices Date: Wed, 18 May 2022 17:47:51 -0700 Message-Id: <20220519004754.2174254-1-mka@chromium.org> X-Mailer: git-send-email 2.36.1.124.g0e6072fb45-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org As of now LoadPin restricts loading of kernel files to a single pinned filesystem, typically the rootfs. This works for many systems, however it can result in a bloated rootfs (and OTA updates) on platforms where multiple boards with different hardware configurations use the same rootfs image. Especially when 'optional' files are large it may be preferable to download/install them only when they are actually needed by a given board. Chrome OS uses Downloadable Content (DLC) [1] to deploy certain 'packages' at runtime. As an example a DLC package could contain firmware for a peripheral that is not present on all boards. DLCs use dm-verity [2] to verify the integrity of the DLC content. This series extends LoadPin to allow loading of kernel files from trusted dm-verity devices. LoadPin maintains a list of root digests of verity devices it considers trusted. Userspace can populate this list through an ioctl on the new LoadPin securityfs entry 'dm-verity'. The ioctl receives a file descriptor of a file with verity digests as parameter. Verity reads the digests from this file after confirming that the file is located on the pinned root. The digest file must contain one digest per line. The list of trusted digests can only be set up once, which is typically done at boot time. When a kernel file is read LoadPin first checks (as usual) whether the file is located on the pinned root, if so the file can be loaded. Otherwise, if the verity extension is enabled, LoadPin determines whether the file is located on a verity backed device and whether the root digest of that device is in the list of trusted digests. The file can be loaded if the verity device has a trusted root digest. [1] https://chromium.googlesource.com/chromiumos/platform2/+/HEAD/dlcservice/docs/developer.md [2] https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/verity.html Changes in v5: - changed dm_verity_loadpin_is_sb_trusted() to dm_verity_loadpin_is_bdev_trusted() - deleted bad semicolon in declaration of stub for dm_verity_loadpin_is_bdev_trusted() - bumped verity version number to 1.8.1 - added 'Acked-by' tags from Kees Changes in v4: - a trusted verity device must have a single target of type 'verity' - changed struct trusted_root_digest to have an unsized u8 array instead of a pointer - use shared list of verity digests, deleted dm_verity_loadpin_set_trusted_root_digests() - use newline as separator in digest file instead of comma - after reading an invalid/corrupt digest file deny further attempts of setting up the list of digests - added comment to read_trusted_verity_root_digests() explaining that an invalid digests entry invalidates the entire list of digests - minor refactoring of verity related code in LoadPin Changes in v3: - added securityfs for LoadPin (currently only populated when CONFIG_SECURITY_LOADPIN_VERITY=y) - added uapi include for LoadPin - changed the interface for setting up the list of trusted digests from sysctl to ioctl on securityfs entry - added stub for loadpin_is_fs_trusted() to be used CONFIG_SECURITY_LOADPIN_VERITY is not select - depend on CONFIG_SECURITYFS instead of CONFIG_SYSTCL - updated Kconfig help - minor changes in read_trusted_verity_root_digests() - updated commit message Changes in v2: - userspace now passes the path of the file with the verity digests via systcl, instead of the digests themselves - renamed sysctl file to 'trusted_verity_root_digests_path' - have CONFIG_SECURITY_LOADPIN_VERITY depend on CONFIG_SYSCTL - updated Kconfig doc - updated commit message Matthias Kaehlcke (3): dm: Add verity helpers for LoadPin LoadPin: Enable loading from trusted dm-verity devices dm: verity-loadpin: Use CONFIG_SECURITY_LOADPIN_VERITY for conditional compilation drivers/md/Makefile | 1 + drivers/md/dm-verity-loadpin.c | 74 +++++++++++++ drivers/md/dm-verity-target.c | 35 ++++++- drivers/md/dm-verity.h | 4 + include/linux/dm-verity-loadpin.h | 27 +++++ include/uapi/linux/loadpin.h | 22 ++++ security/loadpin/Kconfig | 16 +++ security/loadpin/loadpin.c | 167 +++++++++++++++++++++++++++++- 8 files changed, 344 insertions(+), 2 deletions(-) create mode 100644 drivers/md/dm-verity-loadpin.c create mode 100644 include/linux/dm-verity-loadpin.h create mode 100644 include/uapi/linux/loadpin.h