TZMon: Improving mobile game security with ARM trustzone

The TZMon is the security framework for a mobile game application.

This framework is specially designed for an integrity check, secure update, abusing detection, data hiding, and timer synchronization using ARM TrustZone.

TZMon uses AOSP(Android Open Source Project) as a Normal OS and OPTEE as a Secure OS.

Target Board is hikey960. Refer to the link for more information. [here]

There are two modes for TZMon; SIM_MODE, and TARGET_MODE.

A TARGET_MODE use hikey960 board as a mobile environment. SIM_MODE can make applying and verifying TZMon easy.

The simulation environments are as like below:

• Mobile Game Apps (including TZMon library): Android Studio Simulator
• TZMon Trusted Application: hikey960 board
• S2B (for connection with the simulator and the target board): Linux machine (independent of kernel version and linux distro)
• Update Server (for secure update protocol): Linux machine (independent of kernel version and linux distro)

Getting Started with tzMon

Prerequisites

• Preparing for the mobile game source code.
• Applying the JNI environment to the game.
• Adding permission option to the AndroidManifest.xml file.

  <uses-permission android:name="android.permission.PACKAGE_USAGE_STATS" tools:ignore="ProtectedPermissions" />
  <uses-permission android:name="android.permission.INTERNET" />

• Allowing usage access in the smart-phone or simulator.

• Execution update_server and S2B. (for SIM_MODE): update_server and s2b are running on linux machine. Two application must use same port number

  ./update_server [port_number]
  ./s2b_server [port_number]

• Installation of TZMon TA to the target board. Refer to the more information. [here]
• Installation of TZMon Host(CA) for SIM_MODE

Usage

1. Loading the TZMon library formed as JNI.

  static {
    System.loadLibrary("tzMonJNI");
  }

2. Declaration of TZMon API to the game source and compile game source.

  public native boolean tzmonInitKeyNFlag();
  public native boolean tzmonCheckAppHash();
  public native boolean tzmonSecureUpdate();
  public native boolean tzmonAbusingDetection();
  public native boolean tzmonSyncTimer();
  public native boolean tzmonHidingSetup();
  public native int tzmonGetHKey(String data);

3. Create app/src/main/include directory and copy openssl and optee directories.
4. Create app/src/main/libs and jni directory.
5. Create app/src/main/jni/armeabi-v7a and x86 and copy libcrypto.a, libssl.a libteec.a files.

6. Compile mobile game. (ctrl + F9)
7. Execution of javac to create JNI header file. (If success, it creates header file in jni directiry)
8. Create Android.mk file

# Android.mk
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := ssl
LOCAL_SRC_FILES := $(TARGET_ARCH_ABI)/libssl.a
LOCAL_EXPORT_C_INCLUDES := include
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := crypto
LOCAL_SRC_FILES := $(TARGET_ARCH_ABI)/libcrypto.a
LOCAL_EXPORT_C_INCLUDES := jni/include
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := teec
LOCAL_SRC_FILES := $(TARGET_ARCH_ABI)/libteec.a
LOCAL_EXPORT_C_INCLUDES := jni/include
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := tzMonJNI
LOCAL_SRC_FILES := tzmonMain.cpp
LOCAL_SRC_FILES += tzmonCrypto.cpp
LOCAL_SRC_FILES += tzmonSocket.cpp
LOCAL_SRC_FILES += tzmonUtil.cpp
LOCAL_SRC_FILES += tzmonTEEC.cpp
LOCAL_CFLAGS := -DSIM_MODE
LOCAL_CFLAGS += -DUSE_FIXAPPHASH
LOCAL_LDLIBS := -llog
LOCAL_LDLIBS += -ldl
LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
LOCAL_STATIC_LIBRARIES += ssl
LOCAL_STATIC_LIBRARIES += crypto
LOCAL_STATIC_LIBRARIES += teec
include $(BUILD_SHARED_LIBRARY)

9. Copy TZMon library source code in the jni directory. Refer to the link

Publications

Jeon, S., & Kim, H. K. (2021). TZMon: Improving mobile game security with ARM trustzone. Computers & Security, 102391.

@article{jeon2021tzmon,
  title={TZMon: Improving mobile game security with ARM trustzone},
  author={Jeon, Sanghoon and Kim, Huy Kang},
  journal={Computers \& Security},
  pages={102391},
  year={2021},
  publisher={Elsevier}
}

About

This program is authored and maintained by Sanghoon Jeon.

Email: kppw99@gmail.com

GitHub@kppw99