StormHook:Android侵入式Java Hook框架

• 支持Android Art和Dalvik
• 支持Andorid 4.0-6.0
• 支持注入到其他进程Hook
• 支持public，static，private方法
• 支持调用原始的Java方法

模块

• StormHookSample：用来测试Hook效果的例子
• InjectSo：用来注入到StormHookSample进程的so文件
• HookCore: 加载到StormHookSample进程的dex

用法

Step1： 编译InjectSo模块 生成libhook.so

adb push libhook.so /data/local/tmp/

Step2：HookCore模块是Android Studio工程，将生成的Apk中的classes.dex提取出来重命名为hook.dex

adb push hook.dex /data/local/tmp/

Step3: HookCore/Native是jni工程 编译生成libdalvikhook_native.so和libarthook_native.so

adb push libdalvikhook_native.so /data/local/tmp/
adb push libarthook_native.so /data/local/tmp/

Step4: 关闭selinux

root@hammerhead:/ # setenforce 0
root@hammerhead:/ # getenforce
Permissive

Step5: 注入libhook.so到StormHookSample App中

root@hammerhead:/data/local/tmp # ps |grep storm
u0_a71    17772 182   923264 41632 ffffffff 400ca73c S com.example.stormhookdemo

root@hammerhead:/data/local/tmp # ./inject /data/local/tmp/libhook.so 17772
target_pid:456c,soPath:/data/local/tmp/libhook.so
library path = /data/local/tmp/libhook.so

hook成功显示的log

adb logcat -s "storm"
V/storm   (17772): g_JavaVM:414cef00
V/storm   (17772): LoadDex optFile path:/data/data/com.example.stormhookdemo/hoo
k.dat
V/storm   (17772): classLoaders size:1
V/storm   (17772): original Element size:1
V/storm   (17772): ClassMethodHook[Can't find class:com/storm/hook/main in bootc
lassloader
V/storm   (17772): loadClass com/storm/hook/main successful clazz:0x1d600059
D/storm   (17772): Inject dex entry is called
D/storm   (17772): After addNativeLibraryDirectory pathLoader is:dalvik.system.P
athClassLoader[DexPathList[[zip file "/data/app/com.example.stormhookdemo-1.apk"
, dex file "dalvik.system.DexFile@425e31c0"],nativeLibraryDirectories=[/data/loc
al/tmp, /data/app-lib/com.example.stormhookdemo-1, /vendor/lib, /system/lib]]]
D/storm   (17772): [+]find original method (getMacAddress_hook)
D/storm   (17772): [+]find original method (test_public_hook)
D/storm   (17772): [+]find original method (currentTimeMillis)
D/storm   (17772): [+]find original method (test_private)
D/storm   (17772): [+]find original method (test_privatestatic)
D/storm   (17772): Inject dex hook success
I/storm   (17772): *-*-*-*-*-*-*- End -*-*-*-*-*-*-*-*-*-*

测试button事件的log输出

adb logcat -s "storm","hook"
D/hook    (19001): getMacAddress is hooked :)
D/storm   (19001): Wifi mac :c4:43:8f:f7:d1:03
D/hook    (19001): test_public is hooked
D/storm   (19001): test_public is called
D/hook    (19001): test_private is hooked
D/storm   (19001): test_private is called
D/storm   (19001): test_private return:10
D/hook    (19001): currentTimeMillis is much better in seconds :)
D/storm   (19001): small Currentime:5885303
D/hook    (19001): test_private is hooked
D/storm   (19001): test_private is called
D/storm   (19001): test_private return:10
D/hook    (19001): test_privatestatic is hooked
D/storm   (19001): test_privatestatic is called

原理

早期的Dalvik hook是修改Java方法的签名属性为native，replacemethod是native方法，需要通过java反射来调用原始函数，这种方式来hook代码非常不方便。

StormHook框架中，Hook代码全部用Java代码实现，避免了反射调用，要实现这种方案，需要将Hook代码编译为Dex或者Jar来加载到目标进程

首先注入so来进入目标进程的native世界,然后使用LoadDex来加载Dex

jclass DexFile=jenv->FindClass("dalvik/system/DexFile");
if(ClearException(jenv))
{
	ALOG("storm","find DexFile class failed");
	return 0;
}
jmethodID loadDex=jenv->GetStaticMethodID(DexFile,"loadDex","(Ljava/lang/String;Ljava/lang/String;I)Ldalvik/system/DexFile;");

为了PathClassLoader能够执行动态加载的Dex中的代码，根据MultiDex原理将动态加载的dex与原始Dex合并，然后执行动态加载Dex的入口类，这样我们就进入进程的Java世界来进行Java Hook操作。

如何找到动态加载的Dex中的java类，有2种方法：

方法一：使用PathClassLoader.loadClass(className)； 主Dex对应的是pathClassLoader 由于我们将外部Dex和当前Dex进行MultiDex操作，那么这2个Dex的类都可以通过pathClassLoader来找到外部dex目标类

jstring className=jenv->NewStringUTF(name);
jclass clazzCL = jenv->GetObjectClass(g_classLoader);
jmethodID loadClass = jenv->GetMethodID(clazzCL,"loadClass","(Ljava/lang/String;)Ljava/lang/Class;");
jclass tClazz = (jclass)jenv->CallObjectMethod(g_classLoader,loadClass,className);

方法二：dexFile.loadClass(className); 通过LoadDex加载外部Dex之后，会得到一个dex对象dexObj，也可以使用dexObj.loadClass来找到外部dex目标类

jclass DexFile=jenv->FindClass("dalvik/system/DexFile");
jmethodID loadClass=jenv->GetMethodID(DexFile,"loadClass","(Ljava/lang/String;Ljava/lang/ClassLoader;)Ljava/lang/Class;");
if(ClearException(jenv))
{
	ALOG("storm","find loadClass methodId failed");
	return 0;
}
//important dexObject.loadClass()
jstring className=jenv->NewStringUTF(name);
jclass tClazz = (jclass)jenv->CallObjectMethod(dexObject,loadClass,className,g_classLoader);

参考

• https://github.com/alibaba/AndFix
• https://github.com/mar-v-in/ArtHook
• Android热修复升级探索——追寻极致的代码热替换
• Android 7.0 行为变更