On Thu, May 19, 2022 at 12:39:14PM -0400, Mike Snitzer wrote: > On Wed, May 18 2022 at 8:47P -0400, > Matthias Kaehlcke <mka@xxxxxxxxxxxx> 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 <mka@xxxxxxxxxxxx> > > Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> > > --- > > > > 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 <linux/list.h> > > +#include <linux/kernel.h> > > +#include <linux/dm-verity-loadpin.h> > > + > > +#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; > > +} > > This should have: > EXPORT_SYMBOL_GPL(dm_verity_loadpin_is_bdev_trusted); Actually the export shouldn't be needed as long as LoadPin is the only caller: config SECURITY_LOADPIN_VERITY bool "Allow reading files from certain other filesystems that use dm-verity" depends on DM_VERITY=y && SECURITYFS LoadPin can't be built as a module, hence for the verity integration to work verity needs to be built into the kernel. > > 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 <linux/module.h> > > #include <linux/reboot.h> > > #include <linux/scatterlist.h> > > +#include <linux/string.h> > > > > #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); > > Why is this exported? It's remainder from an early version that I forgot to remove, agreed it's not needed. > > + > > +/* > > + * 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); > > Why is this exported? > > Both of these should be internal to dm-verity module. Agreed, will change. > Have you built a modular kernel to test? I didn't, since LoadPin is always builtin and hence verity needs to be builtin too for CONFIG_SECURITY_LOADPIN_VERITY. > > 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 <linux/list.h> > > + > > +struct block_device; > > + > > +extern struct list_head loadpin_trusted_verity_root_digests; > > s/loadpin_trusted_verity_root_digests/dm_verity_loadpin_trusted_root_digests/ ? ok > > + > > +struct trusted_root_digest { > > + struct list_head node; > > + unsigned int len; > > + u8 data[]; > > +}; > > s/trusted_root_digest/dm_verity_loadpin_trusted_root_digest/ ? > > Long names, but more consistent and informative. Sounds good, I'll change it in the next version. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel