From patchwork Tue May 17 23:34:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 12853002 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 B14E1C433FE for ; Tue, 17 May 2022 23:35:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231834AbiEQXfF (ORCPT ); Tue, 17 May 2022 19:35:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231828AbiEQXfD (ORCPT ); Tue, 17 May 2022 19:35:03 -0400 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79596527E0 for ; Tue, 17 May 2022 16:35:02 -0700 (PDT) Received: by mail-pj1-x1029.google.com with SMTP id qe3-20020a17090b4f8300b001dc24e4da73so2781012pjb.1 for ; Tue, 17 May 2022 16:35:02 -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=70QJz56WdWWmTL0B6emMjXbopnc6hlLXxIz6KUt2rIk=; b=W05BK4Nx6n8Tgd6iJwnFLSqsNhYNl0hrR2DvD/EXRwgmuGTyvkhPX+60jLTK/mCl44 H0LVqwEC8m3N5O/F4REujx1uriLyXsiDabcQO4cS/s/dHnfuSJ7Abjo4LfHYPnbwqscs qoSrLbLWd8fZRINkTF2v+XV7Cjnbmda/ztzU4= 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=70QJz56WdWWmTL0B6emMjXbopnc6hlLXxIz6KUt2rIk=; b=YSThE8XE+hq6OO4VtjEqlz+ApmK2DA6OKRImWpfmRpEt17WkNBtJoRl4FhNfTTv+uM VocVmU5GITl5Mx4uYB86knC2PpXrAJpW+b4MPt23kMwrFPeymG3CvzI+JKZAskE2avTu RuyWTFeqlQL4Rf9P3RwHTje2A1kb3EddEP+mSbBurwMLRdhPPb7jHUm5WRAmBxL98h9+ 6DWhsmT/i+LMx+JdZj+3//FVXPHrhXdZlyYz85WIRTxpGN5WFd3sT2d/0eYEnF3pw4Go mY/ZH81joFJJ1OVrUXQMpb3vpxlquJlo97f6o/i7lH811e4PFP1wiL98qiLfT6/17KSO /WYg== X-Gm-Message-State: AOAM532A64VR5o2juA8iuPrnOL8RuWjJ5sS+AP+dW78qvOkTKvxZOYRv O1mCvYANcR+jOOBE0pP1i3n3Aw== X-Google-Smtp-Source: ABdhPJz220+nzi3d4a1gLQVv2K14GMGqs/RIb4+jwX6pC6/HC0zH/+CzmRerWtH5qYEVhjVdlmJsEA== X-Received: by 2002:a17:90b:4c10:b0:1dc:8289:7266 with SMTP id na16-20020a17090b4c1000b001dc82897266mr39216091pjb.190.1652830501982; Tue, 17 May 2022 16:35:01 -0700 (PDT) Received: from localhost ([2620:15c:11a:202:a14:3166:4b67:b688]) by smtp.gmail.com with UTF8SMTPSA id o3-20020a62cd03000000b0050e006279bfsm277942pfg.137.2022.05.17.16.35.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 May 2022 16:35:01 -0700 (PDT) From: Matthias Kaehlcke To: Alasdair Kergon , Mike Snitzer , Kees Cook , James Morris , "Serge E . Hallyn" Cc: linux-security-module@vger.kernel.org, dm-devel@redhat.com, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Song Liu , Douglas Anderson , Matthias Kaehlcke Subject: [PATCH v4 1/3] dm: Add verity helpers for LoadPin Date: Tue, 17 May 2022 16:34:55 -0700 Message-Id: <20220517163437.v4.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> X-Mailer: git-send-email 2.36.0.550.gb090851708-goog In-Reply-To: <20220517233457.1123309-1-mka@chromium.org> References: <20220517233457.1123309-1-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 --- 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, 144 insertions(+) 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..3226fbe4a1fe --- /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_sb_trusted(struct super_block *sb) +{ + 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(sb->s_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..6f07b849fcb2 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" @@ -1310,6 +1311,38 @@ 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}, 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..c2bfd2b9c651 --- /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 super_block; + +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_sb_trusted(struct super_block *sb); +#else +static inline bool dm_verity_loadpin_is_sb_trusted(struct super_block *sb); +{ + return false; +} +#endif + +#endif /* __LINUX_DM_LOADPIN_H */