| Message ID | 20220523141325.v6.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | LoadPin: Enable loading from trusted dm-verity devices | expand |
Mike, does this look good to you or are any further changes needed to get this landed? Thanks Matthias On Mon, May 23, 2022 at 02:13:58PM -0700, 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 <mka@chromium.org> > Acked-by: Kees Cook <keescook@chromium.org> > --- > > 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 <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(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 <linux/module.h> > #include <linux/reboot.h> > #include <linux/scatterlist.h> > +#include <linux/string.h> > > #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 <linux/list.h> > + > +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 */ > -- > 2.36.1.124.g0e6072fb45-goog >
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 <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(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 <linux/module.h> #include <linux/reboot.h> #include <linux/scatterlist.h> +#include <linux/string.h> #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 <linux/list.h> + +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 */