> From: deven.desai@xxxxxxxxxxxxxxxxxxx > [mailto:deven.desai@xxxxxxxxxxxxxxxxxxx] > Sent: Wednesday, October 13, 2021 9:07 PM > From: Deven Bowers <deven.desai@xxxxxxxxxxxxxxxxxxx> > > Allows author of IPE policy to indicate trust for a singular dm-verity > volume, identified by roothash, through "dmverity_roothash" and all > signed dm-verity volumes, through "dmverity_signature". > > Signed-off-by: Deven Bowers <deven.desai@xxxxxxxxxxxxxxxxxxx> > --- > > Relevant changes since v6: > * Squash patch 08/12, 10/12 to [11/16] > > --- > security/ipe/eval.c | 5 ++ > security/ipe/eval.h | 10 +++ > security/ipe/hooks.c | 48 ++++++++++++++ > security/ipe/hooks.h | 6 ++ > security/ipe/ipe.c | 9 +++ > security/ipe/ipe.h | 3 + > security/ipe/modules/Kconfig | 23 +++++++ > security/ipe/modules/Makefile | 2 + > security/ipe/modules/dmverity_roothash.c | 80 +++++++++++++++++++++++ > security/ipe/modules/dmverity_signature.c | 25 +++++++ > 10 files changed, 211 insertions(+) > create mode 100644 security/ipe/modules/dmverity_roothash.c > create mode 100644 security/ipe/modules/dmverity_signature.c > > diff --git a/security/ipe/eval.c b/security/ipe/eval.c > index 361efccebad4..facc05c753f4 100644 > --- a/security/ipe/eval.c > +++ b/security/ipe/eval.c > @@ -23,6 +23,7 @@ static struct super_block *pinned_sb; > static DEFINE_SPINLOCK(pin_lock); > > #define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb) > +#define FILE_BLOCK_DEV(f) (FILE_SUPERBLOCK(f)->s_bdev) > > /** > * pin_sb: pin the underlying superblock of @f, marking it as trusted > @@ -95,6 +96,10 @@ static struct ipe_eval_ctx *build_ctx(const struct file *file, > ctx->hook = hook; > ctx->ci_ctx = ipe_current_ctx(); > ctx->from_init_sb = from_pinned(file); > + if (file) { > + if (FILE_BLOCK_DEV(file)) > + ctx->ipe_bdev = ipe_bdev(FILE_BLOCK_DEV(file)); > + } > > return ctx; > } > diff --git a/security/ipe/eval.h b/security/ipe/eval.h > index 42fb7fdf2599..25d2d8d55702 100644 > --- a/security/ipe/eval.h > +++ b/security/ipe/eval.h > @@ -13,6 +13,14 @@ > #include "hooks.h" > #include "policy.h" > > +struct ipe_bdev { > + const u8 *sigdata; > + size_t siglen; > + > + const u8 *hash; > + size_t hashlen; > +}; > + > struct ipe_eval_ctx { > enum ipe_hook hook; > enum ipe_operation op; > @@ -20,6 +28,8 @@ struct ipe_eval_ctx { > const struct file *file; > struct ipe_context *ci_ctx; > > + const struct ipe_bdev *ipe_bdev; > + > bool from_init_sb; > }; > > diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c > index 2d4a4f0eead0..470fb48e490c 100644 > --- a/security/ipe/hooks.c > +++ b/security/ipe/hooks.c > @@ -13,6 +13,7 @@ > #include <linux/types.h> > #include <linux/refcount.h> > #include <linux/rcupdate.h> > +#include <linux/blk_types.h> > #include <linux/binfmts.h> > #include <linux/mman.h> > > @@ -219,3 +220,50 @@ void ipe_sb_free_security(struct super_block *mnt_sb) > { > ipe_invalidate_pinned_sb(mnt_sb); > } > + > +/** > + * ipe_bdev_free_security: free nested structures within IPE's LSM blob > + * in block_devices > + * @bdev: Supplies a pointer to a block_device that contains the structure > + * to free. > + */ > +void ipe_bdev_free_security(struct block_device *bdev) > +{ > + struct ipe_bdev *blob = ipe_bdev(bdev); > + > + kfree(blob->sigdata); > +} > + > +/** > + * ipe_bdev_setsecurity: associate some data from the block device layer > + * with IPE's LSM blob. > + * @bdev: Supplies a pointer to a block_device that contains the LSM blob. > + * @key: Supplies the string key that uniquely identifies the value. > + * @value: Supplies the value to store. > + * @len: The length of @value. > + */ > +int ipe_bdev_setsecurity(struct block_device *bdev, const char *key, > + const void *value, size_t len) > +{ > + struct ipe_bdev *blob = ipe_bdev(bdev); > + > + if (!strcmp(key, DM_VERITY_SIGNATURE_SEC_NAME)) { > + blob->siglen = len; > + blob->sigdata = kmemdup(value, len, GFP_KERNEL); > + if (!blob->sigdata) > + return -ENOMEM; > + > + return 0; > + } > + > + if (!strcmp(key, DM_VERITY_ROOTHASH_SEC_NAME)) { > + blob->hashlen = len; > + blob->hash = kmemdup(value, len, GFP_KERNEL); > + if (!blob->hash) > + return -ENOMEM; > + > + return 0; > + } > + > + return -ENOSYS; > +} > diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h > index e7f107ab5620..285f35187188 100644 > --- a/security/ipe/hooks.h > +++ b/security/ipe/hooks.h > @@ -10,6 +10,7 @@ > #include <linux/sched.h> > #include <linux/binfmts.h> > #include <linux/security.h> > +#include <linux/device-mapper.h> > > enum ipe_hook { > ipe_hook_exec = 0, > @@ -40,4 +41,9 @@ int ipe_on_kernel_load_data(enum kernel_load_data_id > id, bool contents); > > void ipe_sb_free_security(struct super_block *mnt_sb); > > +void ipe_bdev_free_security(struct block_device *bdev); > + > +int ipe_bdev_setsecurity(struct block_device *bdev, const char *key, > + const void *value, size_t len); > + > #endif /* IPE_HOOKS_H */ > diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c > index 1382d50078ec..215936cb4574 100644 > --- a/security/ipe/ipe.c > +++ b/security/ipe/ipe.c > @@ -9,6 +9,7 @@ > #include "ipe_parser.h" > #include "modules/ipe_module.h" > #include "modules.h" > +#include "eval.h" > > #include <linux/fs.h> > #include <linux/sched.h> > @@ -20,8 +21,14 @@ > > struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = { > .lbs_task = sizeof(struct ipe_context __rcu *), > + .lbs_bdev = sizeof(struct ipe_bdev), > }; > > +struct ipe_bdev *ipe_bdev(struct block_device *b) > +{ > + return b->security + ipe_blobs.lbs_bdev; > +} > + > static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { > LSM_HOOK_INIT(task_alloc, ipe_task_alloc), > LSM_HOOK_INIT(task_free, ipe_task_free), > @@ -31,6 +38,8 @@ static struct security_hook_list ipe_hooks[] > __lsm_ro_after_init = { > LSM_HOOK_INIT(kernel_read_file, ipe_on_kernel_read), > LSM_HOOK_INIT(kernel_load_data, ipe_on_kernel_load_data), > LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security), > + LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security), > + LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity), > }; > > /** > diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h > index ad16d2bebfec..6b4c7e07f204 100644 > --- a/security/ipe/ipe.h > +++ b/security/ipe/ipe.h > @@ -14,10 +14,13 @@ > > #include <linux/types.h> > #include <linux/sched.h> > +#include <linux/blk_types.h> > #include <linux/lsm_hooks.h> > > extern struct lsm_blob_sizes ipe_blobs; > extern struct ipe_parser __start_ipe_parsers[], __end_ipe_parsers[]; > extern struct ipe_module __start_ipe_modules[], __end_ipe_modules[]; > > +struct ipe_bdev *ipe_bdev(struct block_device *b); > + > #endif /* IPE_H */ > diff --git a/security/ipe/modules/Kconfig b/security/ipe/modules/Kconfig > index fad96ba534e2..a6ea06cf0737 100644 > --- a/security/ipe/modules/Kconfig > +++ b/security/ipe/modules/Kconfig > @@ -16,5 +16,28 @@ config IPE_PROP_BOOT_VERIFIED > > If unsure, answer N. > > +config IPE_PROP_DM_VERITY_SIGNATURE > + bool "Enable support for signed dm-verity volumes" > + depends on DM_VERITY_VERIFY_ROOTHASH_SIG > + default Y > + help > + This option enables the property 'dmverity_signature' in > + IPE policy. This property evaluates to TRUE when a file > + is evaluated against a dm-verity volume that was mounted > + with a signed root-hash. > + > + If unsure, answer Y. > + > +config IPE_PROP_DM_VERITY_ROOTHASH > + bool "Enable support for dm-verity volumes" > + depends on DM_VERITY > + default Y > + help > + This option enables the property 'dmverity_roothash' in > + IPE policy. This property evaluates to TRUE when a file > + is evaluated against a dm-verity volume whose root hash > + matches the supplied value. > + > + If unsure, answer Y. > > endmenu > diff --git a/security/ipe/modules/Makefile b/security/ipe/modules/Makefile > index e0045ec65434..84fadce85193 100644 > --- a/security/ipe/modules/Makefile > +++ b/security/ipe/modules/Makefile > @@ -6,3 +6,5 @@ > # > > obj-$(CONFIG_IPE_PROP_BOOT_VERIFIED) += boot_verified.o > +obj-$(CONFIG_IPE_PROP_DM_VERITY_SIGNATURE) += dmverity_signature.o > +obj-$(CONFIG_IPE_PROP_DM_VERITY_ROOTHASH) += dmverity_roothash.o > diff --git a/security/ipe/modules/dmverity_roothash.c > b/security/ipe/modules/dmverity_roothash.c > new file mode 100644 > index 000000000000..0f82bec3b842 > --- /dev/null > +++ b/security/ipe/modules/dmverity_roothash.c > @@ -0,0 +1,80 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) Microsoft Corporation. All rights reserved. > + */ > + > +#include "ipe_module.h" > + > +#include <linux/fs.h> > +#include <linux/types.h> > + > +struct counted_array { > + size_t len; > + u8 *data; > +}; > + > +static int dvrh_parse(const char *valstr, void **value) > +{ > + int rv = 0; > + struct counted_array *arr; > + > + arr = kzalloc(sizeof(*arr), GFP_KERNEL); > + if (!arr) { > + rv = -ENOMEM; > + goto err; > + } > + > + arr->len = (strlen(valstr) / 2); > + > + arr->data = kzalloc(arr->len, GFP_KERNEL); > + if (!arr->data) { > + rv = -ENOMEM; > + goto err; > + } > + > + rv = hex2bin(arr->data, valstr, arr->len); > + if (rv != 0) > + goto err2; > + > + *value = arr; > + return rv; > +err2: > + kfree(arr->data); > +err: > + kfree(arr); > + return rv; > +} > + > +static bool dvrh_eval(const struct ipe_eval_ctx *ctx, const void *val) > +{ > + const u8 *src; > + struct counted_array *expect = (struct counted_array *)val; > + > + if (!ctx->ipe_bdev) > + return false; > + > + if (ctx->ipe_bdev->hashlen != expect->len) > + return false; > + > + src = ctx->ipe_bdev->hash; > + > + return !memcmp(expect->data, src, expect->len); Hi Deven I was curious to see if determining the property at run-time could apply also to dm-verity. It seems it could be done (I omit some checks, I also keep the expected value in hex format): --- md = dm_get_md(file_inode(ctx->file)->i_sb->s_dev); 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 (strcmp(ti->type->name, "verity")) continue; ti->type->status(ti, STATUSTYPE_IMA, 0, result, sizeof(result)); } dm_put_live_table(md, srcu_idx); dm_put(md); root_digest_ptr = strstr(result, "root_digest="); return !strncmp(expect->data, root_digest_ptr + 12, expect->len); --- Only dm_table_get_target() is not exported yet, but I guess it could be. dm_table_get_num_targets() is exported. With this code, you would not have to manage security blobs outside IPE. Maybe you could add a blob for the super block, so that you verify the dm-verity property just once per filesystem. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua > +} > + > +static int dvrh_free(void **val) > +{ > + struct counted_array *expect = (struct counted_array *)val; > + > + kfree(expect->data); > + kfree(expect); > + > + return 0; > +} > + > +IPE_MODULE(dvrh) = { > + .name = "dmverity_roothash", > + .version = 1, > + .parse = dvrh_parse, > + .free = dvrh_free, > + .eval = dvrh_eval, > +}; > diff --git a/security/ipe/modules/dmverity_signature.c > b/security/ipe/modules/dmverity_signature.c > new file mode 100644 > index 000000000000..08746fcbcb3e > --- /dev/null > +++ b/security/ipe/modules/dmverity_signature.c > @@ -0,0 +1,25 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) Microsoft Corporation. All rights reserved. > + */ > + > +#include "ipe_module.h" > + > +#include <linux/fs.h> > +#include <linux/types.h> > + > +static bool dvv_eval(const struct ipe_eval_ctx *ctx, const void *val) > +{ > + bool expect = (bool)val; > + bool eval = ctx->ipe_bdev && (!!ctx->ipe_bdev->sigdata); > + > + return expect == eval; > +} > + > +IPE_MODULE(dvv) = { > + .name = "dmverity_signature", > + .version = 1, > + .parse = ipe_bool_parse, > + .free = NULL, > + .eval = dvv_eval, > +}; > -- > 2.33.0
