From patchwork Tue Apr 26 21:31:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 12827974 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 0AB85C4332F for ; Tue, 26 Apr 2022 21:31:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355446AbiDZVe2 (ORCPT ); Tue, 26 Apr 2022 17:34:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355448AbiDZVe0 (ORCPT ); Tue, 26 Apr 2022 17:34:26 -0400 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFC7A255B5 for ; Tue, 26 Apr 2022 14:31:17 -0700 (PDT) Received: by mail-pf1-x435.google.com with SMTP id j17so19115358pfi.9 for ; Tue, 26 Apr 2022 14:31:17 -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=oklCy92EPimOxfFRDN0VLcpfYtlk8bEuVQrptcICGjQ=; b=Oijq75H4ZnSjjmdQykwCej7MQp89ReCNNPoI8tw26yzcDylGtn+C6N1eJ/ItXrszGx DDegeANpnswmwzhGZKt2ACu86LqsfO5LlcrUSFkmnhAuOHt4jYBAIq6g9UHTNYjycCxb e5t2R01QUhV3FcltAtNtQuCbaDaRMDsXGqUX0= 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=oklCy92EPimOxfFRDN0VLcpfYtlk8bEuVQrptcICGjQ=; b=i75B0HvYwaKwXQ9lPIm9+1uD2y+pQJSOWyBFq8mgP2aVE7z1KFvf6F28ogxpk8QNGW M3ZgzSKq49j111oSAaKtcTvVsuG25DAg83LWMvg9N5aY6sBbdD/rga7d2F8FWmYmqZPC n5Z6jjrWW2cKeVjN6Fbtt/XpyYqZ20zR7lP5Hrq8qYa1LKfpaPDOIgHNd9MlSzYOjjA4 SzX3NMN//b9MKaw3exL0CdWD4B9nZu623mwzDCGeKrfIyQS6itQwYbN5HNJZqooqzGC+ mWiy3AOAQhAOuAQy5lBXhRMvgukJCtAIRLamOBP/EZGuZk9aTstkJ54P3VjFOT0srRel LW6w== X-Gm-Message-State: AOAM531eSaiNk7Ji4kq+U5COwl0Psc5y4As7cbqZyQvQzvjyDOT+E9cR VhrjCtqDLpuMdBC4Em7o9bkgxQ== X-Google-Smtp-Source: ABdhPJzUwQwV4e6Xy13BncRXONpdBAH4A4s7nHNnuR0F+ID7/PII+ISnk9adQiRXf94sAFkfyX9loQ== X-Received: by 2002:a63:2d46:0:b0:3c1:424a:2a90 with SMTP id t67-20020a632d46000000b003c1424a2a90mr582225pgt.35.1651008677493; Tue, 26 Apr 2022 14:31:17 -0700 (PDT) Received: from localhost ([2620:15c:202:201:eb63:4211:eb5d:f6b]) by smtp.gmail.com with UTF8SMTPSA id d141-20020a621d93000000b00505aa1026f1sm15919562pfd.51.2022.04.26.14.31.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Apr 2022 14:31:17 -0700 (PDT) From: Matthias Kaehlcke To: Alasdair Kergon , Mike Snitzer , Kees Cook , James Morris , "Serge E . Hallyn" Cc: linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, Douglas Anderson , Song Liu , Matthias Kaehlcke Subject: [PATCH v2 1/3] dm: Add verity helpers for LoadPin Date: Tue, 26 Apr 2022 14:31:08 -0700 Message-Id: <20220426143059.v2.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> X-Mailer: git-send-email 2.36.0.rc2.479.g8af0fa9b8e-goog In-Reply-To: <20220426213110.3572568-1-mka@chromium.org> References: <20220426213110.3572568-1-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 v2: - none drivers/md/Makefile | 6 +++ drivers/md/dm-verity-loadpin.c | 80 +++++++++++++++++++++++++++++++ drivers/md/dm-verity-target.c | 33 +++++++++++++ drivers/md/dm-verity.h | 4 ++ include/linux/dm-verity-loadpin.h | 27 +++++++++++ 5 files changed, 150 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..e12cd004d375 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -100,6 +100,12 @@ ifeq ($(CONFIG_IMA),y) dm-mod-objs += dm-ima.o endif +ifeq ($(CONFIG_DM_VERITY),y) +ifeq ($(CONFIG_SECURITY_LOADPIN),y) +dm-mod-objs += dm-verity-loadpin.o +endif +endif + ifeq ($(CONFIG_DM_VERITY_FEC),y) dm-verity-objs += dm-verity-fec.o endif diff --git a/drivers/md/dm-verity-loadpin.c b/drivers/md/dm-verity-loadpin.c new file mode 100644 index 000000000000..972ca93a2231 --- /dev/null +++ b/drivers/md/dm-verity-loadpin.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include +#include + +#include "dm.h" +#include "dm-verity.h" + +static struct list_head *trusted_root_digests; + +/* + * Sets the root digests of verity devices which LoadPin considers as trusted. + * + * This function must only be called once. + */ +void dm_verity_loadpin_set_trusted_root_digests(struct list_head *digests) +{ + if (!trusted_root_digests) + trusted_root_digests = digests; + else + pr_warn("verity root digests trusted by LoadPin are already set!!!\n"); +} + +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, 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 a mapped device is a verity device that is trusted + * by LoadPin. + */ +bool dm_verity_loadpin_is_md_trusted(struct mapped_device *md) +{ + int srcu_idx; + struct dm_table *table; + unsigned int num_targets; + bool trusted = false; + int i; + + if (!trusted_root_digests || list_empty(trusted_root_digests)) + return false; + + table = dm_get_live_table(md, &srcu_idx); + num_targets = dm_table_get_num_targets(table); + for (i = 0; i < num_targets; i++) { + struct dm_target *ti = dm_table_get_target(table, i); + + if (is_trusted_verity_target(ti)) { + trusted = true; + break; + } + } + + dm_put_live_table(md, srcu_idx); + + return trusted; +} diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index 80133aae0db3..0638e61dba51 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 digests, 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..12a86911d05a --- /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 mapped_device; + +struct trusted_root_digest { + u8 *data; + unsigned int len; + struct list_head node; +}; + +#if IS_ENABLED(CONFIG_SECURITY_LOADPIN) && IS_BUILTIN(CONFIG_DM_VERITY) +void dm_verity_loadpin_set_trusted_root_digests(struct list_head *digests); +bool dm_verity_loadpin_is_md_trusted(struct mapped_device *md); +#else +static inline void dm_verity_loadpin_set_trusted_root_digests(struct list_head *digests) {} +static inline bool dm_verity_loadpin_is_md_trusted(struct mapped_device *md) +{ + return false; +} +#endif + +#endif /* __LINUX_DM_LOADPIN_H */