RE: [RFC PATCH v7 11/16] ipe: add support for dm-verity as a trust provider

From: deven.desai(a)linux.microsoft.com [mailto:deven.desai@linux.microsoft.com] Sent: Wednesday, October 13, 2021 9:07 PM From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; 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(a)linux.microsoft.com&gt; --- 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);

+} + +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