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Wed, 18 May 2022 13:35:27 -0700 (PDT) Received: from localhost ([2620:15c:11a:202:a14:3166:4b67:b688]) by smtp.gmail.com with UTF8SMTPSA id w2-20020a62c702000000b0050dc7628161sm2336979pfg.59.2022.05.18.13.35.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 May 2022 13:35:27 -0700 (PDT) Date: Wed, 18 May 2022 13:35:26 -0700 From: Matthias Kaehlcke To: Mike Snitzer Message-ID: References: <20220517233457.1123309-1-mka@chromium.org> <20220517163437.v4.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 Subject: Re: [dm-devel] [PATCH v4 1/3] dm: Add verity helpers for LoadPin X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-security-module@vger.kernel.org, Kees Cook , linux-kernel@vger.kernel.org, Douglas Anderson , James Morris , linux-raid@vger.kernel.org, Song Liu , dm-devel@redhat.com, Alasdair Kergon , "Serge E . Hallyn" Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Wed, May 18, 2022 at 03:52:21PM -0400, Mike Snitzer wrote: > On Tue, May 17 2022 at 7:34P -0400, > Matthias Kaehlcke wrote: > > > 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; > > +} > > Not seeing why passing a super_block a block layer interface was > chosen. > > Please pass the super_block's block_device and rename to > dm_verity_loadpin_is_bdev_trusted() Agreed, passing a block_device is a better choice here, I'll change it as suggested. -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel From mboxrd@z Thu Jan 1 00:00:00 1970 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 1C8FDC433EF for ; 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Wed, 18 May 2022 13:35:27 -0700 (PDT) Date: Wed, 18 May 2022 13:35:26 -0700 From: Matthias Kaehlcke To: Mike Snitzer Cc: Alasdair Kergon , Kees Cook , James Morris , "Serge E . Hallyn" , dm-devel@redhat.com, Douglas Anderson , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Song Liu , linux-security-module@vger.kernel.org Subject: Re: [PATCH v4 1/3] dm: Add verity helpers for LoadPin Message-ID: References: <20220517233457.1123309-1-mka@chromium.org> <20220517163437.v4.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On Wed, May 18, 2022 at 03:52:21PM -0400, Mike Snitzer wrote: > On Tue, May 17 2022 at 7:34P -0400, > Matthias Kaehlcke wrote: > > > 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; > > +} > > Not seeing why passing a super_block a block layer interface was > chosen. > > Please pass the super_block's block_device and rename to > dm_verity_loadpin_is_bdev_trusted() Agreed, passing a block_device is a better choice here, I'll change it as suggested.