[RFC PATCH v6 07/11] ipe: add property for signed dmverity volumes

Deven Bowers
2020-07-30T00:32:03Z

Allow IPE to leverage the stacked security blob infrastructure,
and enlighten IPE to the block_device security blob.

This allows IPE to have a property to express rules around a device-mapper
verity volume whose root-hash has been signed, and the signature has been
verified against the system keyring. This is property is also added in
this patch.

Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
---
security/ipe/Kconfig | 2 +-
security/ipe/Makefile | 1 +
security/ipe/ipe-blobs.c | 84 ++++++++++++++++++++
security/ipe/ipe-blobs.h | 18 +++++
security/ipe/ipe-engine.c | 4 +
security/ipe/ipe-engine.h | 9 +++
security/ipe/ipe-hooks.c | 1 +
security/ipe/ipe-hooks.h | 7 ++
security/ipe/ipe.c | 18 +++++
security/ipe/ipe.h | 2 +
security/ipe/properties/Kconfig | 10 +++
security/ipe/properties/Makefile | 1 +
security/ipe/properties/dmverity-signature.c | 82 +++++++++++++++++++
security/ipe/properties/prop-entry.h | 9 +++
security/ipe/utility.h | 10 +++
15 files changed, 257 insertions(+), 1 deletion(-)
create mode 100644 security/ipe/ipe-blobs.c
create mode 100644 security/ipe/ipe-blobs.h
create mode 100644 security/ipe/properties/dmverity-signature.c

diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 469ef78c2f4f..11b50ef9abca 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -5,7 +5,7 @@

menuconfig SECURITY_IPE
bool "Integrity Policy Enforcement (IPE)"
- depends on SECURITY && AUDIT
+ depends on SECURITY && AUDIT && BLOCK
select SYSTEM_DATA_VERIFICATION
select SECURITYFS
select CRYPTO_SHA1
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 7e98982c5035..98a2245b6956 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_SECURITY_IPE) += \
ipe-property.o \
ipe-hooks.o \
ipe-secfs.o \
+ ipe-blobs.o \

clean-files := ipe-bp.c

diff --git a/security/ipe/ipe-blobs.c b/security/ipe/ipe-blobs.c
new file mode 100644
index 000000000000..041d7d47b723
--- /dev/null
+++ b/security/ipe/ipe-blobs.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include "ipe.h"
+#include "ipe-engine.h"
+#include "ipe-blobs.h"
+
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/device-mapper.h>
+
+/**
+ * ipe_bdev_alloc_security: Performs the initialization of IPE's security blob.
+ * @bdev: The block device to source the security blob from.
+ *
+ * The allocation is performed earlier by the LSM infrastructure,
+ * (on behalf of all LSMs) in lsm_alloc_bdev. At the moment, IPE uses
+ * this time to zero out the region of memory reserved for IPE.
+ *
+ * Return:
+ * 0 - OK
+ */
+int ipe_bdev_alloc_security(struct block_device *bdev)
+{
+ struct ipe_bdev_blob *bdev_sec = ipe_bdev(bdev);
+
+ memset(bdev_sec, 0x0, sizeof(*bdev_sec));
+
+ return 0;
+}
+
+/**
+ * ipe_bdev_free_security: Frees all fields of IPE's block dev security blob.
+ * @bdev: The block device to source the security blob from.
+ *
+ * The deallocation of the blob itself is performed later by the LSM
+ * infrastructure, (on behalf of all LSMs) in lsm_free_bdev.
+ *
+ * Pointers allocated by the bdev_setsecurity hook and alloc_security
+ * hook need to be deallocated here.
+ */
+void ipe_bdev_free_security(struct block_device *bdev)
+{
+ struct ipe_bdev_blob *bdev_sec = ipe_bdev(bdev);
+
+ kfree(bdev_sec->dmverity_rh_sig);
+
+ memset(bdev_sec, 0x0, sizeof(*bdev_sec));
+}
+
+/**
+ * ipe_bdev_setsecurity: Sets the a certain field of a block device security
+ * blob, based on @key.
+ * @bdev: The block device to source the security blob from.
+ * @key: The key representing the information to be stored.
+ * @value: The value to be stored.
+ * @len: The length of @value.
+ *
+ * As block-devices are a generic implementation across specific stacks,
+ * this allows information to be stored from various stacks.
+ *
+ * Return:
+ * 0 - OK
+ * !0 - Error
+ */
+int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
+ const void *value, size_t len)
+{
+ struct ipe_bdev_blob *bdev_sec = ipe_bdev(bdev);
+
+ if (!strcmp(key, DM_VERITY_SIGNATURE_SEC_NAME)) {
+ bdev_sec->dmverity_rh_sig = kmemdup(value, len, GFP_KERNEL);
+ if (!bdev_sec->dmverity_rh_sig)
+ return -ENOMEM;
+
+ bdev_sec->dmv_rh_sig_len = len;
+
+ return 0;
+ }
+
+ return -ENOSYS;
+}
diff --git a/security/ipe/ipe-blobs.h b/security/ipe/ipe-blobs.h
new file mode 100644
index 000000000000..7561f4cef558
--- /dev/null
+++ b/security/ipe/ipe-blobs.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+#include <linux/types.h>
+#include <linux/fs.h>
+
+#include "ipe.h"
+
+#ifndef IPE_BLOB_H
+#define IPE_BLOB_H
+
+static inline struct ipe_bdev_blob *ipe_bdev(struct block_device *bdev)
+{
+ return bdev->security + ipe_blobs.lbs_bdev;
+}
+
+#endif /* IPE_BLOB_H */
diff --git a/security/ipe/ipe-engine.c b/security/ipe/ipe-engine.c
index 0291ced99d64..043faf64ceef 100644
--- a/security/ipe/ipe-engine.c
+++ b/security/ipe/ipe-engine.c
@@ -10,6 +10,7 @@
#include "ipe-engine.h"
#include "ipe-audit.h"
#include "ipe-pin.h"
+#include "ipe-blobs.h"
#include "utility.h"

#include <linux/types.h>
@@ -112,6 +113,9 @@ static struct ipe_engine_ctx *build_ctx(const struct file *file,
local->op = op;
local->hook = hook;

+ if (has_bdev(file))
+ local->sec_bdev = ipe_bdev(bdev(file));
+
return local;
}

diff --git a/security/ipe/ipe-engine.h b/security/ipe/ipe-engine.h
index d9a95674e70d..038c39a8973e 100644
--- a/security/ipe/ipe-engine.h
+++ b/security/ipe/ipe-engine.h
@@ -3,20 +3,29 @@
* Copyright (C) Microsoft Corporation. All rights reserved.
*/

+#include "ipe.h"
#include "ipe-hooks.h"

#include <linux/types.h>
#include <linux/rbtree.h>
#include <linux/fs.h>

+#include <crypto/pkcs7.h>
+
#ifndef IPE_ENGINE_H
#define IPE_ENGINE_H

+struct ipe_bdev_blob {
+ u8 *dmverity_rh_sig;
+ size_t dmv_rh_sig_len;
+};
+
struct ipe_engine_ctx {
enum ipe_op op;
enum ipe_hook hook;
const struct file *file;
const char *audit_pathname;
+ const struct ipe_bdev_blob *sec_bdev;
};

struct ipe_prop_cache {
diff --git a/security/ipe/ipe-hooks.c b/security/ipe/ipe-hooks.c
index 45efe022be04..18ab2dcd74d1 100644
--- a/security/ipe/ipe-hooks.c
+++ b/security/ipe/ipe-hooks.c
@@ -15,6 +15,7 @@
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/security.h>
+#include <linux/device-mapper.h>

/**
* ipe_on_exec: LSM hook called on the exec family of system calls.
diff --git a/security/ipe/ipe-hooks.h b/security/ipe/ipe-hooks.h
index 5e46726f2562..b2417831cfc1 100644
--- a/security/ipe/ipe-hooks.h
+++ b/security/ipe/ipe-hooks.h
@@ -60,4 +60,11 @@ int ipe_on_kernel_load_data(enum kernel_load_data_id id);

void ipe_sb_free_security(struct super_block *mnt_sb);

+int ipe_bdev_alloc_security(struct block_device *bdev);
+
+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_HOOK_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 706ff38083c6..8a612eb62879 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -23,6 +23,9 @@ static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(kernel_load_data, ipe_on_kernel_load_data),
LSM_HOOK_INIT(file_mprotect, ipe_on_mprotect),
LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security),
+ LSM_HOOK_INIT(bdev_alloc_security, ipe_bdev_alloc_security),
+ LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security),
+ LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity),
};

/**
@@ -40,6 +43,10 @@ static int __init ipe_load_properties(void)
if (rc != 0)
return rc;

+ rc = ipe_init_dm_verity_signature();
+ if (rc != 0)
+ return rc;
+
return rc;
}

@@ -72,9 +79,20 @@ static int __init ipe_init(void)
return rc;
}

+struct lsm_blob_sizes ipe_blobs = {
+ .lbs_cred = 0,
+ .lbs_file = 0,
+ .lbs_inode = 0,
+ .lbs_ipc = 0,
+ .lbs_msg_msg = 0,
+ .lbs_task = 0,
+ .lbs_bdev = sizeof(struct ipe_bdev_blob),
+};
+
DEFINE_LSM(ipe) = {
.name = "ipe",
.init = ipe_init,
+ .blobs = &ipe_blobs,
};

bool ipe_enforce = true;
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index af72bb574f73..a59cae2deec6 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -10,11 +10,13 @@

#include <linux/types.h>
#include <linux/fs.h>
+#include <linux/lsm_hooks.h>

#define IPE_MODE_ENFORCE "enforce"
#define IPE_MODE_PERMISSIVE "permissive"

extern bool ipe_enforce;
extern bool ipe_success_audit;
+extern struct lsm_blob_sizes ipe_blobs;

#endif /* IPE_H */
diff --git a/security/ipe/properties/Kconfig b/security/ipe/properties/Kconfig
index 75c6c6ff6cd8..4046f7e5eaef 100644
--- a/security/ipe/properties/Kconfig
+++ b/security/ipe/properties/Kconfig
@@ -13,3 +13,13 @@ config IPE_BOOT_PROP
superblock.

if unsure, answer N.
+
+config IPE_DM_VERITY_SIGNATURE
+ bool "Enable property for signature verified dm-verity volumes"
+ depends on DM_VERITY_VERIFY_ROOTHASH_SIG
+ help
+ This option enables IPE's integration with Device-Mapper Verity's
+ signed root-hashes. This enables the usage of the property,
+ "dmverity_signature" in IPE's policy.
+
+ if unsure, answer Y.
diff --git a/security/ipe/properties/Makefile b/security/ipe/properties/Makefile
index e3e7fe17cf58..6b67cbe36e31 100644
--- a/security/ipe/properties/Makefile
+++ b/security/ipe/properties/Makefile
@@ -9,3 +9,4 @@
obj-$(CONFIG_SECURITY_IPE) += properties.o

properties-$(CONFIG_IPE_BOOT_PROP) += boot-verified.o
+properties-$(CONFIG_IPE_DM_VERITY_SIGNATURE) += dmverity-signature.o
diff --git a/security/ipe/properties/dmverity-signature.c b/security/ipe/properties/dmverity-signature.c
new file mode 100644
index 000000000000..819222f226b7
--- /dev/null
+++ b/security/ipe/properties/dmverity-signature.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include "../ipe.h"
+#include "../ipe-pin.h"
+#include "../ipe-property.h"
+#include "../utility.h"
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/audit.h>
+#include <linux/mount.h>
+
+#define PROPERTY_NAME "dmverity_signature"
+
+static void audit(struct audit_buffer *ab, bool value)
+{
+ audit_log_format(ab, "%s", (value) ? "TRUE" : "FALSE");
+}
+
+static inline void audit_rule_value(struct audit_buffer *ab,
+ const void *value)
+{
+ audit(ab, (bool)value);
+}
+
+static inline void audit_ctx(struct audit_buffer *ab,
+ const struct ipe_engine_ctx *ctx)
+{
+ bool b = has_bdev(ctx->file) && ctx->sec_bdev->dmverity_rh_sig;
+
+ audit(ab, b);
+}
+
+static bool evaluate(const struct ipe_engine_ctx *ctx,
+ const void *value)
+{
+ bool expect = (bool)value;
+
+ if (!has_bdev(ctx->file))
+ return false;
+
+ return ((bool)ctx->sec_bdev->dmverity_rh_sig) == expect;
+}
+
+static int parse(const char *val_str, void **value)
+{
+ if (strcmp("TRUE", val_str) == 0)
+ *value = (void *)true;
+ else if (strcmp("FALSE", val_str) == 0)
+ *value = (void *)false;
+ else
+ return -EBADMSG;
+
+ return 0;
+}
+
+static inline int duplicate(const void *src, void **dest)
+{
+ *dest = (void *)(bool)src;
+
+ return 0;
+}
+
+static const struct ipe_property dmv_signature = {
+ .property_name = PROPERTY_NAME,
+ .version = 1,
+ .eval = evaluate,
+ .parse = parse,
+ .rule_audit = audit_rule_value,
+ .ctx_audit = audit_ctx,
+ .dup = duplicate,
+ .free_val = NULL,
+};
+
+int ipe_init_dm_verity_signature(void)
+{
+ return ipe_register_property(&dmv_signature);
+}
diff --git a/security/ipe/properties/prop-entry.h b/security/ipe/properties/prop-entry.h
index f598dd9608b9..85366366ff0d 100644
--- a/security/ipe/properties/prop-entry.h
+++ b/security/ipe/properties/prop-entry.h
@@ -17,4 +17,13 @@ static inline int __init ipe_init_bootv(void)
int __init ipe_init_bootv(void);
#endif /* CONFIG_IPE_BOOT_PROP */

+#ifndef CONFIG_IPE_DM_VERITY_SIGNATURE
+static inline int __init ipe_init_dm_verity_signature(void)
+{
+ return 0;
+}
+#else
+int __init ipe_init_dm_verity_signature(void);
+#endif /* CONFIG_IPE_DM_VERITY_SIGNATURE */
+
#endif /* IPE_PROP_ENTRY_H */
diff --git a/security/ipe/utility.h b/security/ipe/utility.h
index a13089bb0d8f..7580f17274a3 100644
--- a/security/ipe/utility.h
+++ b/security/ipe/utility.h
@@ -19,4 +19,14 @@ static inline bool has_sb(const struct file *file)
return has_mount(file) && file->f_path.mnt->mnt_sb;
}

+static inline bool has_bdev(const struct file *file)
+{
+ return has_sb(file) && file->f_path.mnt->mnt_sb->s_bdev;
+}
+
+static inline struct block_device *bdev(const struct file *file)
+{
+ return file->f_path.mnt->mnt_sb->s_bdev;
+}
+
#endif /* IPE_UTILITY_H */
--
2.27.0