verify part data in file to support code signing

Change-Id: I06948b7bf8741449dfa1af1964d9170329d90b4b
Signed-off-by: lihehe <lihehao@huawei.com>

code_sign/Kconfig

@@ -2,12 +2,13 @@
 # Copyright (c) 2023 Huawei Device Co., Ltd.
 #
 config SECURITY_CODE_SIGN
-	bool "Advanced code signing feature based on FS Verity"
+	bool "Advanced code signing features based on FS Verity"
 	depends on FS_VERITY
 	default n
 	help
-	  This option enables additional code signing verify features
-	  based on fs-verity, including verify if a certificate's subject
-	  and issuer can be trusted, etc.
+	  This option enables additional code signing features based
+	  on fs-verity, such as 1) protecting part of file to support
+	  carried signature and Merkle tree, 2) verifying if a signing
+	  certificate can be trusted, etc.
 
 	  If unsure, say N.

code_sign/Makefile

@@ -4,7 +4,8 @@
 obj-$(CONFIG_SECURITY_CODE_SIGN)	+= \
 	code_sign_misc.o \
 	verify_cert_chain.o \
-	code_sign_ioctl.o
+	code_sign_ioctl.o \
+	code_sign_ext.o
 
 ccflags-$(CONFIG_SECURITY_CODE_SIGN) += \
 	-I$(srctree)/fs/code_sign \

code_sign/code_sign_ext.c

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023 Huawei Device Co., Ltd.
+ */
+
+#include <linux/code_sign.h>
+#include <linux/fsverity.h>
+
+#include "code_sign_ext.h"
+#include "code_sign_log.h"
+
+/**
+ * Validate code sign descriptor
+ *
+ * Return: 1 on code sign version, 0 on basic version, and -errno on failure
+ */
+static inline int check_code_sign_descriptor(const struct inode *inode,
+	const struct code_sign_descriptor *desc)
+{
+	u64 tree_offset = le64_to_cpu(desc->tree_offset);
+
+	if (!desc->cs_version)
+		return 0;
+
+	if (desc->__reserved1 ||
+		memchr_inv(desc->__reserved2, 0, sizeof(desc->__reserved2)))
+		return -EINVAL;
+
+	if (le64_to_cpu(desc->data_size) > inode->i_size) {
+		code_sign_log_error("Wrong data_size: %llu (desc) > %lld (inode)",
+				le64_to_cpu(desc->data_size), inode->i_size);
+		return -EINVAL;
+	}
+
+	if (desc->salt_size > sizeof(desc->salt)) {
+		code_sign_log_error("Invalid salt_size: %u", desc->salt_size);
+		return -EINVAL;
+	}
+
+	if (IS_INSIDE_TREE(desc)) {
+		if ((tree_offset > inode->i_size) || (tree_offset % PAGE_SIZE != 0)) {
+			code_sign_log_error(
+				"Wrong tree_offset: %llu (desc) > %lld (file size) or alignment is wrong",
+					tree_offset, inode->i_size);
+			return -EINVAL;
+		}
+	} else {
+		if (tree_offset != 0) {
+			code_sign_log_error(
+					"Wrong tree_offset without tree: %llu (desc) != 0",
+					tree_offset);
+			return -EINVAL;
+		}
+	}
+	return 1;
+}
+
+void code_sign_check_descriptor(const struct inode *inode, const void *desc, int *ret)
+{
+	*ret = check_code_sign_descriptor(inode, CONST_CAST_CODE_SIGN_DESC(desc));
+}
+
+void code_sign_before_measurement(void *_desc, int *ret)
+{
+	struct code_sign_descriptor *desc = CAST_CODE_SIGN_DESC(_desc);
+
+	if (desc->cs_version) {
+		// replace version with cs_version
+		desc->version = desc->cs_version;
+		desc->cs_version = 0;
+		*ret = desc->version;
+	}
+}
+
+void code_sign_after_measurement(void *_desc, int version)
+{
+	struct code_sign_descriptor *desc = CAST_CODE_SIGN_DESC(_desc);
+
+	if (version) {
+		// restore cs_version
+		desc->cs_version = desc->version;
+		desc->version = version;
+	}
+}

code_sign/code_sign_ext.h

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023 Huawei Device Co., Ltd.
+ */
+
+#ifndef _CODE_SIGN_EXT_H
+#define _CODE_SIGN_EXT_H
+
+/*
+ * code_sign_ext.c
+ */
+void code_sign_check_descriptor(const struct inode *inode,
+    const void *desc, int *ret);
+
+void code_sign_before_measurement(void *_desc, int *ret);
+
+void code_sign_after_measurement(void *_desc, int version);
+
+#endif /* _CODE_SIGN_H */

code_sign/code_sign_misc.c

@@ -10,6 +10,7 @@
 
 #include "code_sign_ioctl.h"
 #include "code_sign_log.h"
+#include "code_sign_ext.h"
 
 static const struct file_operations code_sign_ops = {
 	.owner = THIS_MODULE,
@@ -28,6 +29,9 @@ static struct miscdevice code_sign_misc = {
 static void code_sign_register_hck_hooks(void)
 {
 	REGISTER_HCK_LITE_HOOK(code_sign_verify_certchain_lhck, code_sign_verify_certchain);
+	REGISTER_HCK_LITE_HOOK(code_sign_check_descriptor_lhck, code_sign_check_descriptor);
+	REGISTER_HCK_LITE_HOOK(code_sign_before_measurement_lhck, code_sign_before_measurement);
+	REGISTER_HCK_LITE_HOOK(code_sign_after_measurement_lhck, code_sign_after_measurement);
 }
 
 static int __init code_sign_init(void)
@@ -46,4 +50,4 @@ static void __exit code_sign_exit(void)
 module_init(code_sign_init);
 module_exit(code_sign_exit);
 
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL");