CN111400723A - Mandatory access control method and system for operating system kernel based on TEE extension - Google Patents

Abstract

The invention discloses an operating system kernel mandatory access control method and system based on TEE extension. When an access behavior is detected in the REE system, the invention calls the interface of the access control enhanced verification framework in the TEE system, and the access control enhanced verification framework is based on Call the access operation type in the request to call the corresponding processing function. The processing function determines whether the access control enhanced verification is passed according to the access operation type, subject information, and object information in the call request. If the access control enhanced verification is passed, it will be in the REE system. The access behavior matches the preset kernel access control rule base. If a matching rule is found, the access behavior is allowed to continue to execute; otherwise, the access behavior is denied. The invention can be enhanced based on the mandatory access control mechanism of the TEE security extension operating system, and has the advantages of comprehensive protection, high verification level, safety and reliability, good versatility and strong expansibility.

Description

Mandatory access control method and system for operating system kernel based on TEE extension

technical field

The invention relates to the field of information security of computer operating systems, in particular to a method and a system for controlling mandatory access of operating system kernels based on TEE extension.

Background technique

As the operating system is the basis for information security protection, whether the system can dynamically protect the security of system resources during operation has become a problem that must be solved. Mandatory access control is one of the important technologies to realize the security protection of the operating system. Based on the access control rules, it implements kernel-level access control on the access behavior between various subjects and system objects in the operating system to protect the security of system resources. The Linux system provides the LSM mandatory access control framework support for the mandatory access control of the operating system, and divides the mandatory access control into two parts: implementation and decision-making: the object manager is responsible for the control and management of the security marking and access behavior of the subject and object objects in the system. , by inserting the HOOK function (hook function) in the access process to obtain the security decision of the access control policy, and determine whether to allow the access to continue execution according to the decision result; the security policy is responsible for accessing the current subject and object according to the access control rules The decision result is obtained, and the LSM framework provides pluggable support for a variety of security policies. Currently, the mandatory access control security policies supported in Linux systems include SELinux, AppArmor, etc., which have been enhanced in the security enhancement of mainstream operating systems such as Linux and Android. Play an important role.

With the advancement of cloud computing, Internet of Things and other technologies, the openness of information systems makes the operating system system security face more threats. Since the operating system kernel runs at the EL1 level in the system, the subject and object objects such as processes and data in the system and The core configuration data of the access control mechanism are stored in the operating system kernel. Once an attacker breaches the operating system kernel through kernel vulnerabilities or virtual machine bottom-level attacks, they can tamper with the key information that the above mandatory access control depends on, thereby circumventing the situation. protected by mandatory access control. For example, in key operations such as process execution and file access, the mandatory access mechanism only makes access control decisions based on the security attributes of the subject and object, and does not judge the integrity of the subject and object objects. Process execution image, file content, etc.) are tampered with, and the tampered subject and object objects can still pass the inspection of the mandatory access control mechanism. Therefore, it is necessary to perform higher-level security-enhanced verification of mandatory access control for specific needs in security-sensitive scenarios. At the same time, the implementation of the mandatory access control mechanism is guided by the security policy configuration. If the security policy configuration is tampered with, it is tantamount to modifying the "legal basis" for safe operation in the operating system world, resulting in the failure of the access control mechanism. The integrity of access control core data has become one of the problems that must be solved. To this end, an OS kernel mandatory access control method must be devised that can provide access control enhanced authentication and core data integrity protection extensions to the OS from a higher run level.

The emerging TEE (Trusted Execution Environment, Trusted Execution Environment) technology utilizes the hardware support at the bottom of the computer to provide the upper-layer software with a trusted execution environment with strong isolation such as CPU, memory, Cache, etc., and the CPU runs at a higher level, which is the upper-layer software. Build a secure and credible computing environment to provide a foundation of trust. At present, there have been breakthroughs in security technologies such as operating system monitoring and trusted computing based on TEE. With the advancement of technology research, there will be more and more operating system services and applications relying on TEE for security enhancement. Therefore, based on the security extension of TEE, the security enhancement of the mandatory access control mechanism of the operating system has a good application prospect, and is a key technical problem that needs to be studied urgently.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention: in view of the above-mentioned problems of the prior art, a method and system for mandatory access control of an operating system kernel based on TEE extension are provided, and the present invention can enhance the mandatory access control mechanism of the operating system based on the security extension of TEE, It has the advantages of comprehensive protection, high verification level, safety and reliability, good versatility and strong scalability.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A method for mandatory access control of operating system kernel based on TEE extension, the implementation steps include:

1) When the access behavior is detected in the REE system, the interface of the access control enhanced verification framework in the TEE system is called, and the access control enhanced verification framework calls the corresponding processing function according to the access operation type in the call request, and the processing function According to the access operation type, subject information, and object information in the call request, it is judged whether the access control enhanced verification is passed. If the access control enhanced verification is passed, it will jump to the next step; otherwise, the access behavior is rejected, and the end and exit;

2) Match the preset kernel access control rule base for the access behavior in the REE system. If there is a matching rule in the kernel access control rule base, the access behavior is allowed to continue to execute; otherwise, the access behavior is rejected.

Optionally, before calling the interface of the access control enhanced verification framework in the TEE system in step 1), the value of the enhanced verification switch is detected, and if the value of the enhanced verification switch is on, the interface of the access control enhanced verification framework in the TEE system is called, Otherwise, jump directly to step 2).

Optionally, it also includes the step of regularly performing integrity verification on the kernel access control rule base located in the shared memory through the TEE system: through the trusted clock interrupt setting of the underlying platform, so that the kernel is generated in the TEE system at regular intervals. Access the integrity measurement value of the control rule base, and match the generated integrity measurement value with the integrity measurement benchmark value stored in the TEE system. If the two are consistent, the integrity verification is determined to pass; if they are inconsistent, the integrity is determined. If the verification fails, an alarm message is output.

Optionally, it also includes a step of regularly performing integrity verification on the key security information of the main body currently running in the system through the TEE system: interrupting the setting through the trusted clock of the underlying platform, so that the TEE system is read and saved at regular intervals. The key security information of each subject in the shared memory with the TEE system, generate the integrity measurement value of the key security information of these subjects, and match the generated integrity measurement value with the integrity measurement benchmark value stored in the TEE system , if the two are consistent, it is determined that the integrity verification is passed; if they are inconsistent, it is determined that the integrity verification is not passed, and an alarm message is output.

Optionally, the REE system also includes a security configuration file for generating the kernel access control rule base during the system startup process, the security configuration file is located in the user space in the REE system, and is loaded during the system startup process. Before the security configuration file, it also includes the steps of verifying the integrity of the security configuration file through the TEE system: reading the security configuration file, generating the integrity measurement value of the security configuration file, and comparing the generated integrity measurement value with the data stored in the TEE system. The integrity measurement benchmark values are matched. If the two are consistent, the integrity verification is determined to pass, and the security configuration file is allowed to be loaded; if they are inconsistent, the integrity verification is determined to fail, the security configuration file is prohibited to be loaded and an alarm message is output.

Optionally, it also includes the step of detecting the writing operation to the security configuration file by the TEE system, if the writing operation of the security configuration file is detected by the REE system, then obtain the information of the application program that performs the writing operation on the security configuration file and push it to the TEE Carry out security verification, the information of the application includes the subject of the application and the integrity measurement value. If the subject of the application is not a security administrator or the integrity measurement value is inconsistent with the saved integrity measurement benchmark value, the security is rejected. Write operations to the configuration file, otherwise write operations to this security configuration file are allowed.

In addition, the present invention also provides an operating system kernel mandatory access control system based on TEE extension, including:

The object management program module is used to call the interface of the access control enhanced verification framework in the TEE system when the access behavior is detected in the REE system, and the access control enhanced verification framework calls the corresponding processing function according to the access operation type in the call request , the processing function judges whether to pass the access control enhanced verification according to the access operation type, subject information, and object information in the call request, and if the access control enhanced verification is passed, then jump to execute the access permission decision program module; otherwise, the access behavior is rejected, end and exit;

The access permission decision program module is used to match the preset kernel access control rule base for the access behavior in the REE system. If there are matching rules in the kernel access control rule base, the access behavior is allowed to continue to execute; otherwise, the access is denied Behavior.

In addition, the present invention also provides a TEE extension-based operating system kernel mandatory access control system, including a computer device programmed or configured to execute the steps of the TEE extension-based operating system kernel mandatory access control method.

In addition, the present invention also provides a TEE extension-based operating system kernel mandatory access control system, including a computer device, the computer device having a memory that is programmed or configured to execute the TEE extension-based operating system kernel mandatory access control system A computer program of the method.

In addition, the present invention also provides a computer-readable storage medium storing a computer program programmed or configured to execute the TEE extension-based operating system kernel mandatory access control method.

Compared with the prior art, the present invention has the following advantages: the present invention calls the interface of the access control enhanced verification framework in the TEE system when the access behavior is detected in the REE system, and the access control enhanced verification framework is based on the call request. The access operation type calls the corresponding processing function, and the processing function judges whether to enhance the verification through the access control according to the access operation type, subject information, and object information in the call request. The access behavior matches the preset kernel access control rule base. If there are matching rules in the kernel access control rule base, the access behavior is allowed to continue to be executed; otherwise, the access behavior is rejected, and the present invention can enhance the operating system based on the security extension of the TEE. The mandatory access control mechanism has the advantages of comprehensive protection, high verification level, safety and reliability, good versatility and strong scalability.

Description of drawings

FIG. 1 is a schematic diagram of a basic flow of a method according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a system according to an embodiment of the present invention.

Detailed ways

The following will take the TEE environment (Trusted Execution Environment, Trusted Execution Environment) of the domestic Feiteng CPU as an example to further describe the method and system for mandatory access control of the operating system kernel based on the TEE extension of the present invention. Among them, the REE system under the REE environment (Rich Execution Environment, general computing environment) runs the Kylin operating system, and the mandatory access control module is implemented through the LSM access control framework.

As shown in FIG. 1, the implementation steps of the TEE extension-based operating system kernel mandatory access control method in this embodiment include:

1) When the access behavior is detected in the REE system (general-purpose operating system), the interface of the access control enhanced verification framework in the TEE system (trusted execution system) is called, and the access control enhanced verification framework is based on the type of access operation in the call request. to call the corresponding processing function, the processing function judges whether to pass the access control enhanced verification according to the access operation type, subject information, and object information in the call request, and if the access control enhanced verification is passed, then jump to the next step; otherwise, reject the access behavior, end and exit;

2) Match the preset kernel access control rule base for the access behavior in the REE system. If there is a matching rule in the kernel access control rule base, the access behavior is allowed to continue to execute; otherwise, the access behavior is rejected.

In this embodiment, the access control enhanced verification framework in the TEE system provides an access control interface so that it can be called when an access behavior is detected in the REE system. As shown in FIG. 2, the REE system calls the access control enhanced verification framework in the TEE system. The interface needs to be implemented by the monitor (monitor) in the TEE system. The access control enhanced verification framework includes multiple processing functions (processing functions 1 to n), which are used to handle access control enhanced verification of different operation types.

Due to the high overhead of switching the security states of the TEE system and the REE system, as an optional implementation, in order to realize the optional opening of the control enhanced verification framework, the access control enhanced verification framework in the TEE system is called in step 1). The interface also includes the value of detecting the enhanced verification switch. If the value of the enhanced verification switch is on, the interface of the access control enhanced verification framework in the TEE system is called, otherwise, it directly jumps to step 2). Therefore, the optional turn-on of the enhanced verification framework can be controlled by the value of the enhanced verification switch. In order to prevent users from turning off the control enhanced verification framework by themselves, this embodiment further includes a step of detecting a write operation to the enhanced verification switch through the TEE system, and if a write operation to the enhanced verification switch is detected, obtain an application for writing the enhanced verification switch Information about the program, which includes the application's principal and integrity metrics, if the application's principal is not a security administrator or the integrity metrics are inconsistent with the saved integrity metrics benchmarks, reject the enhancement Writes to the verification switch are allowed, otherwise writes to the enhanced verification switch are allowed. The enhanced verification switch is set on the REE system side through the above method, which is off by default, and the verification switch is only turned on for operations that require enhanced verification.

When the operating system is running, the kernel access control rule base is the basis for the access control mechanism to make security decisions. If the rules are maliciously tampered with by an attacker, it will directly affect the execution of access control. Therefore, this embodiment also provides integrity protection for the access control rule base in the kernel. This embodiment also includes the step of regularly performing integrity verification on the kernel access control rule base located in the shared memory through the TEE system: through the trusted clock interrupt setting of the underlying platform, so that kernel accesses are generated in the TEE system at regular intervals Control the integrity measurement value of the rule base, and match the generated integrity measurement value with the integrity measurement benchmark value stored in the TEE system. If the two are consistent, the integrity verification is determined to pass; if they are inconsistent, the integrity verification is determined. If it fails, an alarm message is output. When the REE system loads the security policy configuration, a shared memory is first registered with the TEE in the REE system kernel for storing the kernel access control rule base. After the kernel access control rule base is generated, the TEE system will be notified to generate an integrity measurement value for the current kernel access control rule base, and will be stored in the TEE system as an integrity measurement benchmark value. Referring to Figure 1, when an access behavior occurs during system operation, the REE system will first call the access control enhanced verification framework interface in the TEE, and the access control enhanced verification framework will call the corresponding enhanced verification processing function according to the access operation type in the parameters. The parameters include the current operation type, subject information (user ID, user security attributes, etc.) and object information (file name, security attributes, etc.) of the access operation. After the access control enhancement verification is passed, the REE system will continue to match the kernel access control rule base. If there are matching rules, the operation is allowed to continue. As shown in Fig. 2, the realization module of this function is realized by the shared memory verification module of the core data integrity verification unit, and the integrity measurement benchmark value is pre-stored in the integrity measurement benchmark library.

In order to realize the protection of the key security information of the main body of the user process running in the REE system, this embodiment also includes the step of regularly performing integrity verification on the key security information of the main body currently running in the system through the TEE system: The clock interrupt is set, so that the key security information of each subject stored in the shared memory with the TEE system is read in the TEE system at certain time intervals, the integrity measurement value of the key security information of these subjects is generated, and the generated The integrity measurement value matches the integrity measurement benchmark value stored in the TEE system. If the two are consistent, the integrity verification is determined to pass; if they are inconsistent, the integrity verification is determined to fail (it is considered that the integrity of the key information of the user process subject has been tampering), output an alarm message. The subject information here is the key information of the mandatory access subject (process) (such as user, security attribute tag, execution image), and the key information of each process when the system is running (such as user, security attribute tag, execution image), etc. In the shared memory with the TEE system, the TEE system will periodically check the integrity of the key information of the user process main body in the system at runtime. As shown in Fig. 2, the realization module of this function is realized by the process mark verification module of the core data integrity verification unit, and the integrity metric reference value is pre-stored in the integrity metric reference library.

The REE system in this embodiment further includes a security configuration file for generating a kernel access control rule base during system startup, where the security configuration file is located in the user space in the REE system. Before loading the security configuration file in the system startup process, it also includes a step of regularly performing integrity verification on the security configuration file through the TEE system: reading the security configuration file, generating the integrity measurement value of the security configuration file, and converting the generated integrity measurement The value matches the integrity measurement benchmark value stored in the TEE system. If the two are consistent, the integrity verification is determined to pass, and the security configuration file is allowed to be loaded; if they are inconsistent, the integrity verification is determined to fail, and the security configuration file is prohibited to be loaded and output. Alarm message. After the security configuration file is allowed to be loaded, the REE system will continue to read the read configuration file on the file system, and generate the kernel access control rule base in the kernel according to the content of the configuration file; if it is inconsistent, it means that the security configuration of the operating system is illegal Modify, return an error, the REE system will report an error and abort the system startup. In addition, this embodiment also includes the step of detecting the writing operation to the security configuration file through the TEE system. If the writing operation of the security configuration file is detected through the REE system, the information of the application program that performs the writing operation to the security configuration file is obtained and pushed to TEE performs security verification. The information of the application includes the subject of the application and the integrity measurement value. If the subject of the application is not a security administrator or the integrity measurement value is inconsistent with the integrity measurement benchmark value saved in the TEE system, then Deny writes to the security profile, otherwise allow writes to the security profile. As shown in FIG. 2 , the realization module of this function is realized by the configuration file verification module of the core data integrity verification unit, and the integrity metric reference value is pre-stored in the integrity metric reference library.

In order to protect the security configuration file, in this embodiment, the enhanced authentication function of the TEE restricts the read and write of the security configuration file to be completed only by the specified configuration command, and when the configuration command is executed, the TEE first checks the validity and the validity of the user who executes the configuration command. Executable file integrity is verified. In order to protect the integrity of the security configuration file, the enhanced authentication function of TEE restricts the direct rewriting of the configuration file in the REE operating system, and only allows configuration through a specific security configuration tool. When the REE object manager detects that the configuration file is to be modified, the system will first obtain the user information of the configuration process, executable file integrity metrics and other information, and send it to the TEE. The TEE will check the user validity and the integrity of the configuration command program. verify. The user's security configuration includes adding, deleting, and modifying access control rules. Modifying the configuration will first modify the kernel access control rule base, and then modify the modification to the configuration file. After the modification is completed, the system switches to the TEE state, and regenerates the integrity measurement benchmark value for the kernel access control rule base and configuration file. As shown in FIG. 2 , the realization module of this function is realized by the configuration process verification module of the core data integrity verification unit, and the integrity metric reference value is pre-stored in the integrity metric reference library.

Referring to Figure 2, according to the operating mode of the hardware platform in the present embodiment, the system is divided into two parts: the REE system and the TEE system, and the goal of the present embodiment is to implement a security enhancement for the operating system running in the REE based on the expansion of the TEE. Kernel enforces access control. The mandatory access control in the REE system mainly includes the object management module at the kernel layer, the access permission decision module, the access rule configuration module, and the out-of-core security configuration management module at the user layer. The main functions of these modules include:

Object management module, the object management module is mainly responsible for managing various subjects and objects in the operating system, including processes, files, sockets, etc., maintains a security attribute for each newly generated object in the system, and is in the system kernel. Insert HOOK functions into various access operations, call TEE access control enhanced verification and REE access permission decision modules, and implement access control according to the decision results.

Access the permission decision module. When an access behavior occurs in the system, the access permission decision module obtains the security attributes of the subject and object involved in the current access, and queries the access rule configuration module to check whether such access is allowed under the current rule configuration. If it is not allowed by the configuration rules, the access operation will be denied.

The kernel access control rule base mainly saves all security policy configurations in the operating system by the security administrator of the system, including the security attributes of various subjects and objects existing in the system, as well as the kernel access control rule base, which stores different security attributes. The permission rules when access occurs between the subject and the object. The kernel access control rule base runs in the shared memory of the REE and the TEE, and the TEE can directly verify the integrity of the kernel access control rule base when the operating system is running.

Out-of-core security configuration management module. The out-of-core security configuration management module mainly provides a configuration interface for the security policy at the user layer, and saves the security policy configuration in the file system, etc. The security policy configuration of the mandatory access control is saved in the file system of the operating system in the form of a file. The configuration file saves the mandatory access control rule set of the policy, as well as the security attributes of subjects (processes, sockets, etc.) and objects (files, etc.) in the system. When the operating system starts, these configurations are loaded into the kernel, and the kernel access control rule base is generated in the kernel. In order to realize the security protection of the configuration file, the system based on TEE detection restricts that only authorized users (security administrators) can modify the security configuration file through the specified security configuration tool.

In this embodiment, in the REE system kernel, an access control interface for forcibly controlling the access authority of the kernel entity is implemented, and control decisions are obtained by calling the TEE access control enhanced verification and matching kernel access control rule base; the mandatory access control security policy file is installed outside the kernel (Security configuration file), the setting steps of mandatory access control include: 1.1) respectively assign security attribute tags to entities in the operating system kernel, and the entities include subjects and objects related to operating system kernel access operations. In this embodiment, the security attribute mark includes role attribute, type attribute, and secret level attribute, forming a complete security attribute mark system. The operating system environment of this embodiment is the Kylin operating system developed by the School of Computer Science, National Defense University of Science and Technology. The Kylin operating system can support the extended security attribute marking of entities. In addition, this embodiment can also support other operating systems that support extended attributes. The diversity of the platform has the advantages of good versatility and strong scalability; in addition, the tags of application classification can also be stored in the form of files, databases, memory, etc. as required, and encryption can be preferably used for storage. This embodiment uses the extended attribute supported by the operating system to store the security tag of the entity, the extended attribute space is named security.secattr, and the security attribute tag is stored in the extended attribute space security.secattr. 1.2) Objects in the operating system kernel are classified according to their attributes to obtain multiple object classes, and for each object class, an implementable access operation set for the access permission check for the object class is defined. 1.3) Maintain the kernel access control rule base in the operating system kernel, store the kernel access control rules based on the entities and object classes in the operating system kernel to define the subject-to-object kernel access control rules through the kernel access control rule base, and agree to have a certain security through the kernel access control rules. What kind of access operation authority the subject of the attribute mark has to the object with a certain security attribute mark, the access operation authority is within the access operation scope of the implementable access operation set defined by the object class. The kernel access control rule base is stored in the shared memory with the TEE. 1.4) Implement the kernel access control interface in the operating system kernel that enforces the access rights of the kernel entity. When the subject of the operating system kernel applies to access the object, the kernel access control interface marks the security attribute of the subject of the current kernel access operation and the security of the object. The attribute tag and the object class check the access control rule list, and control the permission of the current kernel access operation according to the check result of the access control rule list. In this embodiment, the entity classes in the operating system kernel are positioned to include entity classes such as process, file, dir, inode, and msg, and the access operations corresponding to the entities are closely related to the entity classes. For example, the access operations of the file entity class include: open , read, write, getattr, setattr, link, unlink, rename and other operations. The access operations of the dir entity class include: addname, unlink, read, getattr, setattr and other access operations. When a subject applies for an access operation to an object, it needs to check the kernel access control rule base maintained by the system to determine whether the current subject has the right to access the current object.

This embodiment implements the access control enhanced verification framework and mandatory access control core data integrity verification in the TEE, and provides corresponding interfaces. The access control enhanced authentication framework implements corresponding authentication processing functions in the TEE for all controlled access behaviors in all REEs. In the specific implementation, due to the high cost of switching the security states of the two worlds, an enhanced verification switch is set on the REE side, which is off by default. The verification switch is only turned on for operations that require enhanced verification, and the TEE side follows the verification logic. Implement the corresponding validation handler. In this embodiment, it focuses on implementing process management related interfaces (such as fork, execve, mmap, etc.) and file access related interfaces (such as open, read, write, getattr, setattr, link, unlink, rename, etc.), for example, for execve Processing, the TEE will verify whether the hash value of the executable file of this process matches the relevant records in the integrity measurement benchmark library. Mandatory access control core data includes subject and object security flags in REE, security configuration files, kernel access control rule base, and system security configuration tools.

When the security configuration file is loaded in the system startup process, the TEE first verifies the integrity of the security configuration file, and the security configuration file can be loaded only after the verification. This embodiment includes the configuration file integrity measurement during the system startup process: in this embodiment, the integrity of the mandatory access control policy configuration file is first verified based on the TEE. Only a configuration file that has passed the integrity verification is a legitimate security configuration, and the system can load it. When the operating system starts, an integrity verification request will be issued to the TEE, and the integrity measurement value of the current configuration file will be transmitted to the TEE. The TEE compares the received current configuration file integrity metric with the configuration file integrity metric saved in the TEE, and returns a pass if they are consistent. The REE system will continue to read the read configuration file on the file system, and generate the kernel access control rule base in the kernel according to the content of the configuration file; if it is inconsistent, it means that the security configuration of the operating system has been illegally modified, and an error is returned. An error will be reported and the system startup will be aborted. In this embodiment, the system generates a kernel access control rule base in the kernel according to the security configuration file: when the operating system is running, the kernel access control rule base is the basis for the access control mechanism to make security decisions. Directly affects the enforcement of access control. Therefore, this embodiment performs integrity protection on the access control rule base in the kernel. When the REE system loads the security policy configuration, a shared memory is first registered with the TEE in the REE system kernel for storing the kernel access control rule base. After the kernel access control rule base is generated, it will notify the TEE to generate an integrity measurement value for the current kernel access control rule base, and save it in the TEE as the integrity measurement benchmark value.

During system operation in this embodiment, when an access behavior occurs, the REE system will first call the access control enhanced verification framework interface in the TEE, and the access control enhanced verification framework will call the corresponding enhanced verification processing function according to the access operation type in the parameters. The parameters include the current operation type, subject information (user ID, user security attributes, etc.) and object information (file name, security attributes, etc.) of the access operation. Through access control enhanced verification, REE will continue to match the kernel access control rule base. If there are matching rules, the operation is allowed to continue.

During the running of the system, the TEE regularly verifies the integrity of the REE's kernel access control rule base; when the system is running, the TEE will periodically check the integrity of the shared memory at runtime. Through the trusted clock interrupt setting of the underlying platform, the integrity verification of the kernel access control rule base will be started in the TEE at regular intervals. The integrity metric value is generated by the TEE for the kernel access control rule base in the current shared memory, and matches the integrity metric benchmark value saved in the TEE system. If it is consistent, the verification is passed; if it is inconsistent, the kernel access control rule is considered to be The integrity of the library is tampered with, the verification fails, and the system alarms.

During the operation of the system, the TEE regularly performs integrity verification on the security tags of the subject and object in the REE system; in this embodiment, we mainly carry out security-critical information (such as users, security attribute tags, and execution images) of the process subjects in the system. verify. In the process space, the above information is stored in the shared memory with the TEE, and the TEE will periodically check the integrity of the security-critical information of the user process subject in the system at runtime. Through the trusted clock interrupt setting of the underlying platform, at certain time intervals, the TEE will start the integrity verification of the key information of each user process subject. The TEE generates an integrity metric value for the key information of the user process body in the current shared memory, and matches with the saved integrity metric benchmark value. If they are consistent, the verification is passed; if they are inconsistent, it is considered that the key information of the user process body is complete. If the sex is tampered with, the verification fails, and the system alarms.

In this embodiment, the enhanced verification function of the TEE is used to restrict the read and write of the security configuration file to be completed only by the specified configuration command, and when the configuration command is executed, the TEE first verifies the validity of the user executing the configuration command and the integrity of the executable file . In order to protect the integrity of the security configuration file, the enhanced verification function of TEE restricts the direct rewriting of the configuration file in the REE system, and only allows configuration through a specific security configuration tool. When the REE object manager detects the execution of the configuration tool during fork, execve, etc. calls, the system will first obtain the user information of the process, executable file integrity metrics and other information, and use the SMC instruction to call the TEE access control enhanced verification framework and The processing functions corresponding to the fork and execve operations verify whether the user executing the process is a security administrator, and whether the integrity measurement value of the configuration command program matches the value in the integrity measurement benchmark library. In addition, it is necessary to perform TEE enhanced verification on file operations such as write, getattr, setattr, link, unlink, rename, etc. If the target of the operation is an out-of-core security configuration file with mandatory access control, the above verification of the process body is required, that is, Verify that the user executing the process is a security administrator, and verify that the integrity metrics of the configuration command program match those in the integrity metrics benchmark library. Security configuration includes adding, deleting, and modifying access control rules. Modifying the configuration will first modify the kernel access control rule base, and then modify the modification to the configuration file. After the modification is completed, the system switches to the TEE state, and regenerates the integrity measurement benchmark value for the kernel access control rule base and configuration file, which is used as the benchmark for subsequent judgments.

To sum up, the operating system kernel mandatory access control method based on the TEE extension in this embodiment implements an extension for the existing operating system kernel mandatory access control, including building a kernel access control mechanism in the REE system, and building an access control enhancement in the TEE. Verification framework and access control core data verification module; when the REE system starts and loads the access control function, the TEE will verify the integrity of its access control core data; when the REE system is running, for the controlled access operation, the TEE will first implement access control enhancement After verification, the REE access control security decision is made after passing the verification, and the operation is allowed to be executed after passing the verification; during the operation of the REE system, the TEE will periodically verify the integrity of the access control core data in the REE; the dynamic information of the access control core data in the REE When modifying, it must first pass the legality verification of TEE. Through the above manner, the TEE extension-based operating system kernel mandatory access control method in this embodiment has the advantages of comprehensive protection, high verification level, safety and reliability, good versatility, and strong expansibility. The operating system kernel mandatory access control method based on the TEE extension in this embodiment is based on the traditional operating system kernel mandatory access control, and uses the high-level isolation verification function of the TEE to perform enhanced security verification on the operating system kernel mandatory access control, The integrity of the core data of mandatory access control is verified to ensure that each part of the mandatory access control mechanism of the operating system is not tampered with by malicious attackers, and the access control function can be completed correctly. In the system, the operating system that implements mandatory access control runs in REE, the access control mechanism for the subject and object objects is implemented in the operating system, and the enhanced authentication framework for mandatory access control of the REE operating system is implemented in the TEE. Enhanced verification needs to be implemented in the TEE, and only operations that pass the double-check of TEE enhanced verification and mandatory access rule verification in the REE can continue to be executed in the system. At the same time, during the startup and operation of the REE system, the integrity verification function of the TEE will also verify the integrity of the core data related to mandatory access control to ensure the safe and correct execution of the access control mechanism.

In addition, this embodiment also provides an operating system kernel mandatory access control system based on TEE extension, including:

The object management program module is used to call the interface of the access control enhanced verification framework in the TEE system when the access behavior is detected in the REE system, and the access control enhanced verification framework calls the corresponding processing function according to the access operation type in the call request , the processing function judges whether to pass the access control enhanced verification according to the access operation type, subject information, and object information in the call request, and if the access control enhanced verification is passed, then jump to execute the access permission decision program module; otherwise, the access behavior is rejected, end and exit;

The access permission decision program module is used to match the preset kernel access control rule base for the access behavior in the REE system. If there are matching rules in the kernel access control rule base, the access behavior is allowed to continue to execute; otherwise, the access is denied Behavior.

In addition, this embodiment also provides a TEE extension-based operating system kernel mandatory access control system, including a computer device programmed or configured to execute the steps of the aforementioned TEE extension-based operating system kernel mandatory access control method.

In addition, this embodiment also provides a TEE extension-based operating system kernel mandatory access control system, including a computer device whose memory is programmed or configured to execute the aforementioned TEE extension-based operating system kernel mandatory access control system. A computer program of the method.

In addition, this embodiment also provides a computer-readable storage medium, where a computer program programmed or configured to execute the foregoing TEE extension-based mandatory access control method for an operating system kernel is stored thereon.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein. The present application refers to flowcharts of methods, apparatus (systems), and computer program products according to embodiments of the present application and/or processor-executed instructions generated for implementing a process or processes and/or block diagrams in a flowchart. A means for the function specified in a block or blocks. These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions An apparatus implements the functions specified in a flow or flows of the flowcharts and/or a block or blocks of the block diagrams. These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in one or more of the flowcharts and/or one or more blocks of the block diagrams.

The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims (10)

1. a kind of operating system kernel mandatory access control method based on TEE expansion, it is characterized in that implementing step comprises: 1) When the access behavior is detected in the REE system, the interface of the access control enhanced verification framework in the TEE system is called, and the access control enhanced verification framework calls the corresponding processing function according to the access operation type in the call request, and the processing function According to the access operation type, subject information, and object information in the call request, it is judged whether the access control enhanced verification is passed. If the access control enhanced verification is passed, it will jump to the next step; otherwise, the access behavior is rejected, and the end and exit; 2) Match the preset kernel access control rule base for the access behavior in the REE system. If there is a matching rule in the kernel access control rule base, the access behavior is allowed to continue to execute; otherwise, the access behavior is rejected. 2. The operating system kernel mandatory access control method based on TEE extension according to claim 1, is characterized in that, before calling the interface of the access control enhanced verification framework in the TEE system in step 1), the value of the enhanced verification switch is also included, If the value of the enhanced verification switch is ON, the interface of the access control enhanced verification framework in the TEE system is called; otherwise, it directly jumps to step 2). 3. the operating system kernel mandatory access control method based on TEE extension according to claim 1, is characterized in that, also comprises the step that the kernel access control rule base positioned in shared memory is carried out integrity verification regularly by TEE system: by The trusted clock interrupt setting of the underlying platform enables the integrity measurement value of the kernel access control rule base to be generated in the TEE system at regular intervals, and the generated integrity measurement value is compared with the integrity measurement benchmark value stored in the TEE system. Make a match, if the two are consistent, it is determined that the integrity verification is passed; if they are inconsistent, it is determined that the integrity verification is not passed, and an alarm message is output. 4. the operating system kernel mandatory access control method based on TEE extension according to claim 1, is characterized in that, also comprises the step of carrying out integrity verification to the main body key security information currently running in the system regularly by TEE system: by bottom layer The trusted clock interrupt setting of the platform makes it possible to read the key security information of each subject stored in the shared memory with the TEE system in the TEE system at regular intervals, and generate the integrity measurement value of the key security information of these subjects, The generated integrity metric value is matched with the integrity metric benchmark value stored in the TEE system. If the two are consistent, the integrity verification is determined to pass; if they are inconsistent, the integrity verification is determined to fail, and an alarm message is output. 5. the operating system kernel mandatory access control method based on TEE extension according to claim 1, is characterized in that, in described REE system, also comprises the security configuration file that is used to generate kernel access control rule base in system startup process, The security configuration file is located in the user space in the REE system, and before loading the security configuration file in the system startup process, it also includes a step of performing integrity verification on the security configuration file through the TEE system: reading the security configuration file, generating the security configuration file. The integrity measurement value of the file, and the generated integrity measurement value is matched with the integrity measurement benchmark value stored in the TEE system. If the two are consistent, the integrity verification is determined to pass, and the security configuration file is allowed to be loaded; if they are inconsistent, the It is judged that the integrity verification fails, the security configuration file is prohibited from being loaded and an alarm message is output. 6. the operating system kernel mandatory access control method based on TEE extension according to claim 1, is characterized in that, also comprises the step of writing operation to security profile by TEE system detection, if by REE system detects security profile's step. For write operation, the information of the application that writes the security configuration file is obtained and pushed to the TEE for security verification. The information of the application includes the main body of the application and the integrity measurement value. If the main body of the application is not a security management If the user or the integrity metric value is inconsistent with the saved integrity metric reference value, the write operation to the security configuration file is rejected, otherwise the write operation to the security configuration file is allowed. 7. a kind of operating system kernel mandatory access control system based on TEE expansion, is characterized in that comprising: The object management program module is used to call the interface of the access control enhanced verification framework in the TEE system when the access behavior is detected in the REE system, and the access control enhanced verification framework calls the corresponding processing function according to the access operation type in the call request , the processing function judges whether to pass the access control enhanced verification according to the access operation type, subject information, and object information in the call request, and if the access control enhanced verification is passed, then jump to execute the access permission decision program module; otherwise, the access behavior is rejected, end and exit; The access permission decision program module is used to match the preset kernel access control rule base for the access behavior in the REE system. If there are matching rules in the kernel access control rule base, the access behavior is allowed to continue to execute; otherwise, the access is denied Behavior. 8. An operating system kernel mandatory access control system based on TEE extension, comprising computer equipment, wherein the computer equipment is programmed or configured to execute the TEE extension-based operating system according to any one of claims 1 to 6 The steps of the kernel enforced access control method. 9. An operating system kernel mandatory access control system based on TEE extension, comprising a computer device, characterized in that, a memory of the computer device is programmed or configured to execute the system according to any one of claims 1 to 6. A computer program that enforces access control methods for operating system kernels extended by TEE. 10. A computer-readable storage medium, wherein the computer-readable storage medium is programmed or configured to execute the TEE extension-based operating system kernel mandatory access control according to any one of claims 1 to 6. A computer program of the method.

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