KR20190065524A - Securing the network access of local devices by using TPM - Google Patents

Abstract

The present invention relates to an Internet of things (IoT) security using a trusted platform module (TPM) hardware security chip. According to the present invention, a method of a local access point (AP) for controlling network access of a local device equipped with a TPM comprises the steps of: (a) performing remote attestation based on the TPM to the local AP by the local device; (b-1) allowing access of the local device by the local AP when authentication based on the remote attestation is successful; and (b-2) when the authentication based on the remote attestation fails, performing an action to alleviate cause of the failure of the authentication to the local device, by the local AP.

Description

A method for controlling a network connection of a local device using a TPM hardware security chip,

Things Internet Security

Object Internet is widely used as a framework for ubiquitous computing. Examples of applications of the Internet include smart home systems, street lights, traffic congestion detection and control, noise monitoring, waste management throughout the city, real-time vehicle networks, and smart urban frameworks.

However, the serious problem of the current Internet market is that functionality takes precedence over security. As a result, there have been numerous Internet exploits. As a representative example, in 2015, Crysler's smart car in the US was hacked by a remote attacker during highway traffic, paralyzing the vehicle's physical control system, including audio and brakes. In 2016, smart buildings in Finland were paralyzed by a remote attack, and the buildings were caught in cold chill in the middle of the winter. In 2017, Mirai Botnet and Botnet Barrage malicious code infected tens of thousands of Internet devices and then exploited Botnet to attack DDoS attacks on major DNS servers, resulting in paralysis of major commercial Web sites, including Github, Netflix, and Etsy . The Brikerbot virus made the infected objects Internet useless without rebooting twice without a hardware replacement.

The second reason is that it does not update older versions of vulnerable software that are exposed to attack vulnerabilities, making it easier to exploit attacks that exploit older vulnerabilities. It is.

The inventor of the present invention has studied for a long time to solve such a problem, and after the careful completion, the present invention has been completed.

A first object of the present invention is to propose a security method using security hardware so as to prevent malicious software of all kinds from being detected in a local device from being missed. A second object of the present invention is to check the software update state of the local device and whether the malicious code is activated using the security hardware, and to perform software update of the local device, deletion of a specific file,

In order to accomplish the above object, the present invention provides a method of controlling a network connection of a local device, the method comprising:

(a) the local device performing a remote attestation based on a TPM to the local AP;

(b-1) when the remote attestation-based authentication is successful, allowing the local AP to access the network of the local device;

(b-2) when the remote attestation-based authentication fails, the local AP performs an action to resolve the cause of the authentication failure to the local device;

And a control unit.

In a preferred embodiment of the method, the local access point (AP) may be a router, gateway, or IOT hub capable of fixed installation or portability.

Also, in a preferred embodiment of the method, the step (a) may further include the step of the local network device requesting a network connection to the local AP.

Also in a preferred embodiment of the method, the remote attestation of step (a) comprises:

(a-1) the local device transmitting the software execution log and the PCR signature data (quote) of the TPM to the local AP;

(a-2) cryptographically verifying the authenticity of the software execution log and the PCR signature data (quote) of the TPM by the local access point (AP);

(a-3) analyzing the software execution log by the local access point (AP);

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Further, in a preferred embodiment of the method, in the step (b-2), an action for solving the cause of the authentication failure may be performed by the local AP to install the specific software file, You can request an adjustment.

In a preferred embodiment of the method, the step (b-2) may further include the step of the local AP denying the network access of the local device.

Also, in a preferred embodiment of the method, the software file to be installed may be transmitted to the local device by the local AP.

According to the present invention, the local access point (AP) is not allowed to access the Internet if the software of the local device is not the latest safe version or if the malicious code is running in the local device, The aftermath of malicious code driven from inside the local device can not be distributed to the Internet. This is also fundamentally different from the present invention in Patent Publication No. 10-2009-0057767 (home network authentication and control method using TPM). Since the above patent permits the local appliance to be connected to the Internet in a state in which the verification of the local appliance is not completed, the local appliance in an unsafe state during this time is exposed to an attack from the external network, The aftermath of malicious code driven from inside can be distributed to the Internet.

Also, according to the present invention, it is possible to perform re-remote attestation periodically to the local access point (AP) in the background even while the local device is successfully using the Internet after completing authentication based on remote attestation Therefore, even if the malicious code is invoked from the outside to the local device in the meantime, the local access point (AP) can dynamically detect the malicious code and apply appropriate measures to the local device.

Also, since the present invention confirms the software update state of the local device and whether the malicious code is activated using the security hardware, the security integrity of the present invention is maintained unless the security hardware is physically tampered with.

On the other hand, even if the effects are not explicitly mentioned here, the effect described in the following specification, which is expected by the technical features of the present invention, and its potential effects are treated as described in the specification of the present invention.

1 shows a device configuration according to an embodiment of the present invention.
2 shows a software execution stack of a device according to some embodiments of the present invention.
3 illustrates a method of authenticating a local device based on a remote testimony in accordance with an embodiment of the present invention.
4 shows a software execution log file according to an embodiment of the present invention.
Figure 5 illustrates a method of local device software update based on a remote testimony, a specific software activation suppression action, and a drive sequence adjustment according to some embodiments of the present invention.
* The accompanying drawings illustrate examples of the present invention in order to facilitate understanding of the technical idea of the present invention, and thus the scope of the present invention is not limited thereto.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.

Remote attestation is a technique for remotely checking the remote device's runtime software stack. A software stack is a sequential order of execution of all software that a device has executed since boot. Remote attestation typically uses a TPM, a cryptographic chip. The present invention automatically updates old software of a local device using remote attestation, and verifies whether the malicious code is running and whether the software is running in a safe order. However, there are some difficulties. For example, it is dangerous for a local device to perform remote attestation to a trusted Internet server, for example. Because in this case the local device must first be connected to the Internet for remote attestation. Therefore, if the local device is running outdated vulnerable software before the remote attestation protocol is implemented, some external attacker may use the vulnerability of the software to launch the remote attestation protocol to the local device It can steal sensitive data from the local device before it breaks and the remote attestation is over. Another example of an attack is when the malicious code is already running on the device. In this case, the malicious code may forcibly terminate the remote authentication program running on the local device before the remote attestation is performed at the moment when the local device is connected to the Internet. In this case, remote attestation with the Internet server, Is not generated at all. On the other hand, since the device is already connected to the Internet, malicious code can conduct malicious actions through the Internet. Because of this problem, the present invention performs remote attestation of the local device at a local access point (AP) such as a gateway, router, or IoT hub. And the local AP does not allow to connect to the Internet until the local device has passed a remote attestation based authentication procedure. Therefore, the local device is safe from external attacks until authentication is passed, and the malicious code that has already been infiltrated can not be leaked to the outside.

1 shows a device configuration according to an embodiment of the present invention. Each local device 200 can communicate with the remote devices 400 through the authentication process based on the remote testimony to the local AP 100 upon accessing the Internet and the Internet access right when the authentication is passed. Upon failure of the authentication procedure, the local AP 100 instructs the local device 200 to perform software update or deletion / drive inhibition / drive order adjustment of a specific file. The local AP 100 downloads the software to be updated by the local device 200 from the software center 300 and provides the downloaded software to the local device 200. After performing the requested software updates, the local device 200 deletes the files requested to be deleted or drives the files requested to be inhibited for driving, and then re-executes the remote attestation.

The following is a brief overview of the TPM used for remote attestation. The TPM chip internally has 24 PCR registers, each storing 20 bytes or 32 bytes, and a private encryption key that is not disclosed to the outside world. The private cryptographic key is the secret value of the TPM itself, which does not leak out of the TPM at any time. The TPM provides three major functionalities based on the I / O interface: read, extend, and quote respectively. The read function returns the current value of the selected PCR register. The extend function concatenates the new input value with the current value of the selected PCR register, SHA1 the value, and overwrites the result into the same PCR register. For example, if the specific input values are sequentially extended to the same PCR register, the value of the PCR register represents a cumulative summary value of all input values previously extended. The extend function is used at remote attestation to represent the sequential cumulative summary value of software executed sequentially after booting the device. The quote function signs and returns the current value of the selected PCR register using the TPM's private encryption key, which is called the signature data (quote). One of the input values of the quote function is a nonce, which forces the signature values returned for all quote requests to be different, even if the values of the requested PCR register and PCR register are the same as before. That is, the random number (nonce) is for preventing an attack by the attacker from replaying the same signature data.

The following is an example of a method of recording a cumulative summary value of all programs sequentially executed in the device since the TPM is booted. Figure 2 is an example of a runtime software stack for a device. The device subsequently executed the CRTM, BIOS, boot loader, OS kernel, kernel modules, system processes, and finally application processes sequentially after booting. The entire binary value of each program is extended and recorded in the designated PCR register of the TPM before each program binary is executed. Thus, the designated PCR register of the TPM will represent a complete summary of all software executed sequentially on the device since the device boot.

3 is an embodiment of a method by which the local device 200 remotely atteses to a local AP. The local device 200 requests the local AP 100 for network connection permission (S101). The local AP 100 requests the local device 200 to send PCR signature data (quote), which is information indicating the runtime software stack of the device (S102). As mentioned earlier, a random number (nonce) is used to prevent a replay attack of the signature value. The CPU of the local device 200 transmits the request to the TPM chip 210 inside the device (S103). The TPM chip 210 signs the current value of the PCR register designated by the private encryption key, and transmits the signature data to the CPU of the local device 200 (S104). The local device 200 transmits the signature data (quote) and the software execution log file to the local AP 100 (S105). Hereinafter, the operation performed by the local AP 100 (S106) is as follows. First, verify that the signature value of the signature data (quote) is cryptographically correct. The local AP 100 then cryptographically verifies whether the contents of the software execution log file of the local device 200 match the signature data (quote). Thereafter, the local AP 100 analyzes the software execution log file to determine whether the local device 200 should update the specific software, suppress the execution of a specific malicious program, adjust the running order of a specific program, and the like .

4 is an example of a software execution log file of the local device 200. As shown in FIG. The left column is the file name that is executed sequentially after booting, and the right column is the one-way hash (SHA) value of the file. Even if the log file is tampered, the integrity of the remote attestation security is not compromised unless the TPM is physically attacked and the hardware function of the TPM is not tampered with. This is because if the log file is modulated, the final value of the designated PCR register generated according to the modulated log file will not match the content of the PCR signature data (quote) generated by the TPM. Even if the local device 200 is conquered by the attacker, the attacker can not generate fake PCR signature data (quote) that matches the modulated log file. The reason is that the attacker can not arbitrarily generate the PCR signature data (quote) of the TPM 210 because the private key of the TPM 210 can not be known. This is because the private key of the TPM 210 is not exposed to the outside of the TPM in any case.

The local AP 100 can manage its own template for analyzing the software execution log file that each local device 200 has remote attestation. In one preferred embodiment, the template classifies each executable file of the software stack into one of five sets. The first set is a mandatory set. A mandatory set is a collection of software that must be executed on a device. For example, it can be an important startup program for a local device. The second set is a set of priorities that must be executed but must be executed before other programs or scripts. For example, some security software may have to run before other untrusted programs. The third set is a blacklisted set of malicious code that should not be run on the device. The fourth set is an older set of software that is obsolete and must be updated. For example, it may be an older OpenSSL library vulnerable to Heartbleed attacks. The last set is a miscellaneous set, other undiscovered or untrusted software that does not belong to the previous four sets. For other sets, one of two policies can be enforced. The first is the Strict Policy, which prevents the local device 200 from executing an unknown or untrusted program. This policy is secure and conservative because the local device 200 allows only known good programs to run. On the other hand, a disadvantage is that programs that are not known but are not malicious codes can not be executed on the local device 200. [ The second policy to compensate for this problem is a flexible policy that allows the local device 200 to execute unknown or untrusted programs but instead allows the local AP 100 to perform advanced software execution The log analyzer is imported to analyze the software execution log file of the local device 200 in detail. This advanced analyzer can analyze the software stack of the local device 200 in a more complex manner. In addition to the embodiments described above, there is no limit to how the local AP 100 can classify and analyze software logs, and these methods can be configured directly by the administrator of the local AP or from an external trusted security community, And can be installed in the local AP 100.

5 is a flowchart illustrating a method of updating the software of the local device 200, restricting the driving of the specific file, and adjusting the driving order based on the contents of the remote AP 100 receiving the remote attestation from the local device 200 This is a preferred embodiment. The local device 200 performs the remote attestation described above to the local AP 100, and the local AP 100 analyzes the software execution log file of the device (S100). Upon successful authentication, the local device 200 is allowed to access the network (S200). When the authentication fails, the local AP 100 analyzes the cause of the authentication failure of the local device 200. If an update of the specific software is required, the local AP 100 accesses the URL of the software source, (S110). After downloading the local AP 100 software, it can be cached in the local repository of the local AP 100 for future reuse. After that, the local AP 100 transmits to the local device 200 which software should be updated, which file should be deleted, inhibited from driving, or the order of driving should be changed (S120). If there is software to be updated, the software is transmitted to the local device 200 so that the software can be updated (S130). When all the measures are completed, the local device (S140) reboots and remotely witnesses the local AP (100) (S100).

The time when the remote attestation is performed in the present invention may be an initial network access request to the local AP 100 after the local device 200 is booted or a time after the local AP 200 is allowed to access the network from the local AP 100 , Or may be executed periodically.

For reference, the method of controlling the network connection of the local device according to various preferred embodiments of the present invention may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs, DVDs, magneto-optical media such as floptical disks, A hard disk drive, a flash memory, and the like. Examples of program instructions include high-level language code that can be executed by a computer using an interpreter, as well as machine accords such as those produced by a compiler. A hardware device may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

The scope of protection of the present invention is not limited to the description and the expression of the embodiments explicitly described in the foregoing. It is again to be understood that the present invention is not limited by the modifications or substitutions that are obvious to those skilled in the art.

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Claims (7)

A method for a local access point (AP) to control a network connection of a local device equipped with a Trusted Platform Module (TPM)
(a) the local device performing a remote attestation based on a TPM to the local AP;
(b-1) when the remote attestation-based authentication is successful, allowing the local AP to access the network of the local device;
(b-2) when the remote attestation-based authentication fails, the local AP performs an action to resolve the cause of the authentication failure to the local device;
Wherein the local access point (AP) controls the network connection of the local device.
The method according to claim 1,
Characterized in that the local access point (AP) is a router, gateway or IoT hub capable of fixed installation or portability, wherein the local access point (AP) controls the network connection of the local device.
The method according to claim 1,
wherein step (a) further comprises the step of the local network device requesting a network connection to the local access point (AP).
The method according to claim 1,
The remote attestation of step (a)
(a-1) the local device transmitting the software execution log and the PCR signature data (quote) of the TPM to the local AP;
(a-2) cryptographically verifying the authenticity of the software execution log and the PCR signature data (quote) of the TPM by the local access point (AP);
(a-3) analyzing the software execution log by the local access point (AP);
Wherein the local access point (AP) controls the network connection of the local device.
The method according to claim 1,
Wherein the local AP requests the local device to install a specific software file, to inhibit driving of a specific software, or to adjust a driving order, in order to solve the cause of the authentication failure in the step (b-2) Wherein the point (AP) controls the network connection of the local device.
The method according to claim 1,
Wherein the step (b-2) further comprises the step of the local AP denying the network access of the local device.
6. The method of claim 5,
Wherein the software file to be installed is transmitted to a local device by a local access point (AP).

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