From patchwork Mon May 23 21:13:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 12859488 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 8E486C4332F for ; Mon, 23 May 2022 21:14:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230111AbiEWVOM (ORCPT ); Mon, 23 May 2022 17:14:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229988AbiEWVOG (ORCPT ); Mon, 23 May 2022 17:14:06 -0400 Received: from mail-pf1-x42c.google.com (mail-pf1-x42c.google.com [IPv6:2607:f8b0:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 642AF7CDFD for ; Mon, 23 May 2022 14:14:05 -0700 (PDT) Received: by mail-pf1-x42c.google.com with SMTP id c14so14770103pfn.2 for ; Mon, 23 May 2022 14:14:05 -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=nFCWx+ylAY8dgCt25JkKf17aOAoMoBf41nquHMuShDE=; b=DrxRx3lcJlrmz3dLTTbA/BGYwGlTnpRvbUn3+FYGbiyqc4fVVCmnHeaYh9oRRylTqf mwVuGqA66Wk5YOx4+E+11K5zMPz+fQWvA+SOglWu8QqlKYDd1D9QrrfWjtQVi8VEtz4D RCMsaWnJLfHfLrQLi2TMwruH5HBHe/jWUmoiA= 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=nFCWx+ylAY8dgCt25JkKf17aOAoMoBf41nquHMuShDE=; b=SEV/dNakqzPJwx2wiJG9ibd8zuBKCRPbpXBsEvD7QvZYKyMdk5NV7c7PFGQSW8+5nV EHhVCzBBVYOjAnWT4ov0gHhHmZhmF83A8vpD6UCA7Cj681yTM8jKmrGaLLRrrFvnicSO BtmzS70WRLOoPA7XyPF01rjOM9AouKkntgXJorkSEa3T+uQZhNSzJJuMFcv9rwx7pzOV BqmjHldj6R3ygMUl/q8enBE+WGZZgt893NSugDXDj0RzuBQ5HO9cyz8BV8WYaNbbZPTv eys6U0FmeHdp/cPpOrUBa2KBsHPhHSgvwvHbtRumYo4dyZNkUljWGkCC97V/qvbrS6Oj jBUQ== X-Gm-Message-State: AOAM533sAzgclU4wq+w65NLb1s6f+RcT1505PvWsHTHYG9fBC/ui11ZO 3/swcrm0AgQiKB+rtbnHB4GLKw== X-Google-Smtp-Source: ABdhPJzFBI8sZMoLwz+YBgyqx5St60xio7LcpPb0/AquoAtcXVQBdrULJtODVLNJRd6PnonV4Oef3Q== X-Received: by 2002:a63:8bc9:0:b0:3f8:4817:880b with SMTP id j192-20020a638bc9000000b003f84817880bmr15353756pge.87.1653340444919; Mon, 23 May 2022 14:14:04 -0700 (PDT) Received: from localhost ([2620:15c:11a:202:d9e2:8472:9ac:8532]) by smtp.gmail.com with UTF8SMTPSA id v17-20020a17090ad59100b001deb92de665sm118439pju.46.2022.05.23.14.14.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 May 2022 14:14:04 -0700 (PDT) From: Matthias Kaehlcke To: Alasdair Kergon , Mike Snitzer , Kees Cook , James Morris , "Serge E . Hallyn" Cc: Milan Broz , dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Song Liu , Douglas Anderson , linux-security-module@vger.kernel.org, Matthias Kaehlcke Subject: [PATCH v6 1/3] dm: Add verity helpers for LoadPin Date: Mon, 23 May 2022 14:13:58 -0700 Message-Id: <20220523141325.v6.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> X-Mailer: git-send-email 2.36.1.124.g0e6072fb45-goog In-Reply-To: <20220523211400.290537-1-mka@chromium.org> References: <20220523211400.290537-1-mka@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org 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 v6: - s/loadpin_trusted_verity_root_digests/dm_verity_loadpin_trusted_root_digests/ - s/trusted_root_digest/dm_verity_loadpin_trusted_root_digest/ - removed unnecessary symbol exports 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 | 33 +++++++++++++- drivers/md/dm-verity.h | 4 ++ include/linux/dm-verity-loadpin.h | 27 +++++++++++ 5 files changed, 143 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..10c18bc1652c --- /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(dm_verity_loadpin_trusted_root_digests); + +static bool is_trusted_verity_target(struct dm_target *ti) +{ + u8 *root_digest; + unsigned int digest_size; + struct dm_verity_loadpin_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, &dm_verity_loadpin_trusted_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(&dm_verity_loadpin_trusted_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..c5395e93525a 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 +1311,39 @@ 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; +} + +/* + * 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; +} + 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..fb695ecaa5d5 --- /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 dm_verity_loadpin_trusted_root_digests; + +struct dm_verity_loadpin_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 */