From patchwork Thu May 19 00:47:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 12854432 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 EB07DC433EF for ; Thu, 19 May 2022 00:48:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232354AbiESAsY (ORCPT ); Wed, 18 May 2022 20:48:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232214AbiESAsB (ORCPT ); Wed, 18 May 2022 20:48:01 -0400 Received: from mail-pg1-x531.google.com (mail-pg1-x531.google.com [IPv6:2607:f8b0:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62A003DA48 for ; Wed, 18 May 2022 17:47:59 -0700 (PDT) Received: by mail-pg1-x531.google.com with SMTP id j21so3430510pga.13 for ; Wed, 18 May 2022 17:47:59 -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:in-reply-to:references :mime-version:content-transfer-encoding; bh=OGUXa8bNAudDq2JlWYIa4mvwQC6KqOh0elh1hAr12sk=; b=fRbRD9/rPOFt0Gwdo/JAm/dd8a91A3HR9FzEVH+T0DU9fMmbuLx5rHx2/wrUILbOwH 8oP3SEzaVWMQeeDm6QD85piBXRk00rfdTvLxbljGYdULqOYphhFLRKLDgcgCvvLsQtz7 ozPhGaWBAm8CZwFhJWbHUaGCAzdLG5VSLReRY= 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=OGUXa8bNAudDq2JlWYIa4mvwQC6KqOh0elh1hAr12sk=; b=Sr1lEDtuMBg4TYNLJPVOoqgSKTFmzcb8I+urVshTVsSSRLxmbmjqLp0A1nEJsG4L1Y P/uyVlasbvZpoNR4QCNZm/CcpHbNXeTJtNw7r1p9LubVhZEslO9fECxv5aUL03qDC9Qx uNpZ11uGXIYysGTJjVuC7taPIdXJTqkPeW8L338P1vOqV8vtJSJl2N8S7ALOUWfY/Kpp D3/2HyJxcnT44YTDRbnVIZot5bJRH1Dq7buSzqjHmdgVegpxPeeieVb3iKsSpb4AutYM D0gSNYryfgpbYnJ04iJazCHMUU00xTLRsuT8C3Yc7GKjPIWhWCkIKT0Kl1MyjI5Gb6fO oZbg== X-Gm-Message-State: AOAM533XIHSXIx+jIWsvL3LXSEBnjcwP4A5/ZIsm73fY5u1zwOva7hRM rXXAzukFONQ4Fa3K8gPYu0rujg== X-Google-Smtp-Source: ABdhPJyt/x+jwxWLSG2O76W2L0191xWyJooRPQBf4365K0/5sOuvRoED5GnuQs9mnr1O79eBqZxDCw== X-Received: by 2002:a63:6a45:0:b0:3c1:47b7:edce with SMTP id f66-20020a636a45000000b003c147b7edcemr1714057pgc.207.1652921278800; Wed, 18 May 2022 17:47:58 -0700 (PDT) Received: from localhost ([2620:15c:11a:202:e229:79ea:227e:d9dd]) by smtp.gmail.com with UTF8SMTPSA id s14-20020a17090302ce00b0015eb200cc00sm2236394plk.138.2022.05.18.17.47.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 May 2022 17:47:58 -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 1/3] dm: Add verity helpers for LoadPin Date: Wed, 18 May 2022 17:47:52 -0700 Message-Id: <20220518174739.v5.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> X-Mailer: git-send-email 2.36.1.124.g0e6072fb45-goog In-Reply-To: <20220519004754.2174254-1-mka@chromium.org> References: <20220519004754.2174254-1-mka@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: LoadPin limits loading of kernel modules, firmware and certain other files to a 'pinned' file system (typically a read-only rootfs). To provide more flexibility LoadPin is being extended to also allow loading these files from trusted dm-verity devices. For that purpose LoadPin can be provided with a list of verity root digests that it should consider as trusted. Add a bunch of helpers to allow LoadPin to check whether a DM device is a trusted verity device. The new functions broadly fall in two categories: those that need access to verity internals (like the root digest), and the 'glue' between LoadPin and verity. The new file dm-verity-loadpin.c contains the glue functions. Signed-off-by: Matthias Kaehlcke Acked-by: Kees Cook --- Changes in v5: - changed dm_verity_loadpin_is_sb_trusted() to dm_verity_loadpin_is_bdev_trusted() - bumped version number to 1.8.1 - deleted bad semicolon in declaration of stub for dm_verity_loadpin_is_bdev_trusted() - added 'Acked-by' tag from Kees Changes in v4: - a trusted verity device must have a single target of type 'verity' - share list of verity digests with loadpin, deleted dm_verity_loadpin_set_trusted_root_digests() - dm_verity_loadpin_is_md_trusted() is now dm_verity_loadpin_is_sb_trusted(), it receives a super_block instead of mapped_device. Updated kernel doc. - changed struct trusted_root_digest to have an unsized u8 array instead of a pointer - extend 'dm-verity-objs' instead of 'dm-mod-objs' Changes in v3: - none Changes in v2: - none drivers/md/Makefile | 6 +++ 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 +++++++++++ 5 files changed, 145 insertions(+), 1 deletion(-) create mode 100644 drivers/md/dm-verity-loadpin.c create mode 100644 include/linux/dm-verity-loadpin.h diff --git a/drivers/md/Makefile b/drivers/md/Makefile index 0454b0885b01..71771901c823 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -108,6 +108,12 @@ ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y) dm-verity-objs += dm-verity-verify-sig.o endif +ifeq ($(CONFIG_DM_VERITY),y) +ifeq ($(CONFIG_SECURITY_LOADPIN),y) +dm-verity-objs += dm-verity-loadpin.o +endif +endif + ifeq ($(CONFIG_DM_AUDIT),y) dm-mod-objs += dm-audit.o endif diff --git a/drivers/md/dm-verity-loadpin.c b/drivers/md/dm-verity-loadpin.c new file mode 100644 index 000000000000..49616ea93317 --- /dev/null +++ b/drivers/md/dm-verity-loadpin.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include +#include + +#include "dm.h" +#include "dm-verity.h" + +#define DM_MSG_PREFIX "verity-loadpin" + +LIST_HEAD(loadpin_trusted_verity_root_digests); + +static bool is_trusted_verity_target(struct dm_target *ti) +{ + u8 *root_digest; + unsigned int digest_size; + struct trusted_root_digest *trd; + bool trusted = false; + + if (!dm_is_verity_target(ti)) + return false; + + if (dm_verity_get_root_digest(ti, &root_digest, &digest_size)) + return false; + + list_for_each_entry(trd, &loadpin_trusted_verity_root_digests, node) { + if ((trd->len == digest_size) && + !memcmp(trd->data, root_digest, digest_size)) { + trusted = true; + break; + } + } + + kfree(root_digest); + + return trusted; +} + +/* + * Determines whether the file system of a superblock is located on + * a verity device that is trusted by LoadPin. + */ +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + struct mapped_device *md; + struct dm_table *table; + struct dm_target *ti; + int srcu_idx; + bool trusted = false; + + if (list_empty(&loadpin_trusted_verity_root_digests)) + return false; + + md = dm_get_md(bdev->bd_dev); + if (!md) + return false; + + table = dm_get_live_table(md, &srcu_idx); + + if (dm_table_get_num_targets(table) != 1) + goto out; + + ti = dm_table_get_target(table, 0); + + if (is_trusted_verity_target(ti)) + trusted = true; + +out: + dm_put_live_table(md, srcu_idx); + dm_put(md); + + return trusted; +} diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index 80133aae0db3..d6a7903e91e6 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -19,6 +19,7 @@ #include #include #include +#include #define DM_MSG_PREFIX "verity" @@ -1310,9 +1311,41 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) return r; } +/* + * Check whether a DM target is a verity target. + */ +bool dm_is_verity_target(struct dm_target *ti) +{ + return ti->type->module == THIS_MODULE; +} +EXPORT_SYMBOL_GPL(dm_is_verity_target); + +/* + * Get the root digest of a verity target. + * + * Returns a copy of the root digest, the caller is responsible for + * freeing the memory of the digest. + */ +int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size) +{ + struct dm_verity *v = ti->private; + + if (!dm_is_verity_target(ti)) + return -EINVAL; + + *root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL); + if (*root_digest == NULL) + return -ENOMEM; + + *digest_size = v->digest_size; + + return 0; +} +EXPORT_SYMBOL_GPL(dm_verity_get_root_digest); + static struct target_type verity_target = { .name = "verity", - .version = {1, 8, 0}, + .version = {1, 8, 1}, .module = THIS_MODULE, .ctr = verity_ctr, .dtr = verity_dtr, diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index 4e769d13473a..c832cc3e3d24 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -129,4 +129,8 @@ extern int verity_hash(struct dm_verity *v, struct ahash_request *req, extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, sector_t block, u8 *digest, bool *is_zero); +extern bool dm_is_verity_target(struct dm_target *ti); +extern int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, + unsigned int *digest_size); + #endif /* DM_VERITY_H */ diff --git a/include/linux/dm-verity-loadpin.h b/include/linux/dm-verity-loadpin.h new file mode 100644 index 000000000000..d37146dbb1a8 --- /dev/null +++ b/include/linux/dm-verity-loadpin.h @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __LINUX_DM_VERITY_LOADPIN_H +#define __LINUX_DM_VERITY_LOADPIN_H + +#include + +struct block_device; + +extern struct list_head loadpin_trusted_verity_root_digests; + +struct trusted_root_digest { + struct list_head node; + unsigned int len; + u8 data[]; +}; + +#if IS_ENABLED(CONFIG_SECURITY_LOADPIN) && IS_BUILTIN(CONFIG_DM_VERITY) +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev); +#else +static inline bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + return false; +} +#endif + +#endif /* __LINUX_DM_VERITY_LOADPIN_H */