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

deven.desai
2021-10-13T19:07:26Z

From: Deven Bowers <deven.desai@linux.microsoft.com>

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@linux.microsoft.com>
---

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