[RFC PATCH v5 09/11] dm-verity: add bdev_setsecurity hook for root-hash

[Deven Bowers <deven.desai@linux.microsoft.com>]

Add a security hook call to set a security property of a block_device
in dm-verity with the root-hash that was verified to match the merkel-tree.

Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
---
 drivers/md/dm-verity-target.c               |   8 +
 include/linux/device-mapper.h               |   1 +
 security/ipe/ipe-blobs.c                    |  11 ++
 security/ipe/ipe-engine.h                   |   3 +
 security/ipe/ipe.c                          |   4 +
 security/ipe/properties/Kconfig             |  13 +-
 security/ipe/properties/Makefile            |   1 +
 security/ipe/properties/dmverity-roothash.c | 153 ++++++++++++++++++++
 security/ipe/properties/prop-entry.h        |   9 ++
 9 files changed, 202 insertions(+), 1 deletion(-)
 create mode 100644 security/ipe/properties/dmverity-roothash.c

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index fabc173aa7b3..7f609906af16 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -16,8 +16,10 @@
 #include "dm-verity.h"
 #include "dm-verity-fec.h"
 #include "dm-verity-verify-sig.h"
+#include "dm-core.h"
 #include <linux/module.h>
 #include <linux/reboot.h>
+#include <linux/security.h>
 
 #define DM_MSG_PREFIX			"verity"
 
@@ -530,6 +532,12 @@ static int verity_verify_io(struct dm_verity_io *io)
 			return -EIO;
 	}
 
+	r = security_bdev_setsecurity(dm_table_get_md(v->ti->table)->bdev,
+				      DM_VERITY_ROOTHASH_SEC_NAME,
+				      v->root_digest, v->digest_size);
+	if (unlikely(r < 0))
+		return r;
+
 	/*
 	 * At this point, the merkel tree has finished validating.
 	 * if signature was specified, validate the signature here.
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 02be0be21d38..b82e8223d52a 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -625,5 +625,6 @@ static inline unsigned long to_bytes(sector_t n)
 }
 
 #define DM_VERITY_SIGNATURE_SEC_NAME DM_NAME	".verity-sig"
+#define DM_VERITY_ROOTHASH_SEC_NAME DM_NAME	".verity-rh"
 
 #endif	/* _LINUX_DEVICE_MAPPER_H */
diff --git a/security/ipe/ipe-blobs.c b/security/ipe/ipe-blobs.c
index 041d7d47b723..6a09d5c6dea8 100644
--- a/security/ipe/ipe-blobs.c
+++ b/security/ipe/ipe-blobs.c
@@ -46,6 +46,7 @@ void ipe_bdev_free_security(struct block_device *bdev)
 	struct ipe_bdev_blob *bdev_sec = ipe_bdev(bdev);
 
 	kfree(bdev_sec->dmverity_rh_sig);
+	kfree(bdev_sec->dmverity_rh);
 
 	memset(bdev_sec, 0x0, sizeof(*bdev_sec));
 }
@@ -80,5 +81,15 @@ int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
 		return 0;
 	}
 
+	if (!strcmp(key, DM_VERITY_ROOTHASH_SEC_NAME)) {
+		bdev_sec->dmverity_rh = kmemdup(value, len, GFP_KERNEL);
+		if (!bdev_sec->dmverity_rh)
+			return -ENOMEM;
+
+		bdev_sec->rh_size = len;
+
+		return 0;
+	}
+
 	return -ENOSYS;
 }
diff --git a/security/ipe/ipe-engine.h b/security/ipe/ipe-engine.h
index 038c39a8973e..696baaa423ff 100644
--- a/security/ipe/ipe-engine.h
+++ b/security/ipe/ipe-engine.h
@@ -18,6 +18,9 @@
 struct ipe_bdev_blob {
 	u8	*dmverity_rh_sig;
 	size_t	dmv_rh_sig_len;
+
+	u8 *dmverity_rh;
+	size_t rh_size;
 };
 
 struct ipe_engine_ctx {
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 8a612eb62879..8f4dfb8c547f 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -47,6 +47,10 @@ static int __init ipe_load_properties(void)
 	if (rc != 0)
 		return rc;
 
+	rc = ipe_init_dm_verity_rh();
+	if (rc != 0)
+		return rc;
+
 	return rc;
 }
 
diff --git a/security/ipe/properties/Kconfig b/security/ipe/properties/Kconfig
index 4046f7e5eaef..4f09092522d9 100644
--- a/security/ipe/properties/Kconfig
+++ b/security/ipe/properties/Kconfig
@@ -14,8 +14,19 @@ config IPE_BOOT_PROP
 
 	  if unsure, answer N.
 
+config IPE_DM_VERITY_ROOTHASH
+	bool "Enable property for authorizing dm-verity volumes via root-hash"
+	depends on DM_VERITY
+	help
+	  This option enables IPE's integration with Device-Mapper Verity.
+	  This enables the usage of the property "dmverity_roothash" in IPE's
+	  policy. This property allows authorization or revocation via a
+	  a hex-string representing the roothash of a dmverity volume.
+
+	  if unsure, answer Y.
+
 config IPE_DM_VERITY_SIGNATURE
-	bool "Enable property for signature verified dm-verity volumes"
+	bool "Enable property for verified dm-verity volumes"
 	depends on DM_VERITY_VERIFY_ROOTHASH_SIG
 	help
 	  This option enables IPE's integration with Device-Mapper Verity's
diff --git a/security/ipe/properties/Makefile b/security/ipe/properties/Makefile
index 6b67cbe36e31..d9a3807797f4 100644
--- a/security/ipe/properties/Makefile
+++ b/security/ipe/properties/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_SECURITY_IPE) += properties.o
 
 properties-$(CONFIG_IPE_BOOT_PROP) += boot-verified.o
 properties-$(CONFIG_IPE_DM_VERITY_SIGNATURE) += dmverity-signature.o
+properties-$(CONFIG_IPE_DM_VERITY_ROOTHASH) += dmverity-roothash.o
diff --git a/security/ipe/properties/dmverity-roothash.c b/security/ipe/properties/dmverity-roothash.c
new file mode 100644
index 000000000000..09112e1af753
--- /dev/null
+++ b/security/ipe/properties/dmverity-roothash.c
@@ -0,0 +1,153 @@
+// 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/mount.h>
+#include <linux/audit.h>
+#include <linux/kernel.h>
+
+#define PROPERTY_NAME "dmverity_roothash"
+
+struct counted_array {
+	u8 *arr;
+	size_t len;
+};
+
+static void audit(struct audit_buffer *ab, const void *value)
+{
+	const struct counted_array *a = (const struct counted_array *)value;
+
+	if (!a || a->len == 0)
+		audit_log_format(ab, "NULL");
+	else
+		audit_log_n_hex(ab, a->arr, a->len);
+}
+
+static inline void audit_rule_value(struct audit_buffer *ab,
+				    const void *value)
+{
+	audit(ab, value);
+}
+
+static inline void audit_ctx(struct audit_buffer *ab,
+			     const struct ipe_engine_ctx *ctx)
+{
+	struct counted_array a;
+
+	if (!has_bdev(ctx->file))
+		return audit(ab, NULL);
+
+	a.arr = ctx->sec_bdev->dmverity_rh;
+	a.len = ctx->sec_bdev->rh_size;
+
+	return audit(ab, &a);
+}
+
+static bool evaluate(const struct ipe_engine_ctx *ctx,
+		     const void *value)
+{
+	const struct counted_array *a = (const struct counted_array *)value;
+
+	if (!has_bdev(ctx->file))
+		return false;
+
+	if (a->len != ctx->sec_bdev->rh_size)
+		return false;
+
+	return memcmp(a->arr, ctx->sec_bdev->dmverity_rh, a->len) == 0;
+}
+
+static int parse(const char *val_str, void **value)
+{
+	struct counted_array *arr = NULL;
+	int rv = 0;
+
+	arr = kzalloc(sizeof(*arr), GFP_KERNEL);
+	if (!arr) {
+		rv = -ENOMEM;
+		goto err;
+	}
+
+	arr->len = strlen(val_str) / 2;
+
+	arr->arr = kzalloc(arr->len, GFP_KERNEL);
+	if (!arr->arr) {
+		rv = -ENOMEM;
+		goto err;
+	}
+
+	rv = hex2bin(arr->arr, val_str, arr->len);
+	if (rv != 0)
+		goto err;
+
+	*value = arr;
+	return rv;
+err:
+	if (arr)
+		kfree(arr->arr);
+	kfree(arr);
+	return rv;
+}
+
+static int duplicate(const void *src, void **dest)
+{
+	struct counted_array *arr = NULL;
+	const struct counted_array *src_arr = src;
+	int rv = 0;
+
+	arr = kmemdup(src_arr, sizeof(*arr), GFP_KERNEL);
+	if (!arr) {
+		rv = -ENOMEM;
+		goto err;
+	}
+
+	arr->arr = kmemdup(src_arr->arr, src_arr->len, GFP_KERNEL);
+	if (!arr->arr) {
+		rv = -ENOMEM;
+		goto err;
+	}
+
+	*dest = arr;
+	return rv;
+err:
+	if (arr)
+		kfree(arr->arr);
+	kfree(arr);
+
+	return rv;
+}
+
+static void free_val(void **value)
+{
+	struct counted_array *a = (struct counted_array *)*value;
+
+	if (a)
+		kfree(a->arr);
+	kfree(a);
+	*value = NULL;
+}
+
+static const struct ipe_property dmv_roothash = {
+	.property_name = PROPERTY_NAME,
+	.version = 1,
+	.eval = evaluate,
+	.parse = parse,
+	.rule_audit = audit_rule_value,
+	.ctx_audit = audit_ctx,
+	.dup = duplicate,
+	.free_val = free_val,
+};
+
+int ipe_init_dm_verity_rh(void)
+{
+	return ipe_register_property(&dmv_roothash);
+}
diff --git a/security/ipe/properties/prop-entry.h b/security/ipe/properties/prop-entry.h
index 85366366ff0d..86a360570f3b 100644
--- a/security/ipe/properties/prop-entry.h
+++ b/security/ipe/properties/prop-entry.h
@@ -26,4 +26,13 @@ static inline int __init ipe_init_dm_verity_signature(void)
 int __init ipe_init_dm_verity_signature(void);
 #endif /* CONFIG_IPE_DM_VERITY_SIGNATURE */
 
+#ifndef CONFIG_IPE_DM_VERITY_ROOTHASH
+static inline int __init ipe_init_dm_verity_rh(void)
+{
+	return 0;
+}
+#else
+int __init ipe_init_dm_verity_rh(void);
+#endif /* CONFIG_IPE_DM_VERITY_ROOTHASH */
+
 #endif /* IPE_PROP_ENTRY_H */
-- 
2.27.0