android java层hook框架 android jni hook

注入安卓进程,并hook java世界的方法

         说明:

安卓系统的可执行对象有两个世界,一个是Linux Native世界,一个是Java世界.两个世界能够通过jvm产生交互,具体来说就是通过jni技术进行互相干涉.但是在正常情况下,只能在Java世界通过jni调用native方法,二native不能在没有任何java上的支持下干涉java世界.

在一些应用中,我们需要对一个app的java世界进行干涉.再说到linux上的进程注入技术,已不用我多讲,但是传统的linux进程注入技术在安卓上只能进入目标进程的native世界.

于是本教程是要注入别的进程,并hook java世界的java 方法!

条件:

1)       手机已root

2)       布置好了的ndk环境

3)       网友贡献的inject代码

由于安卓上的进程注入网上已经有很多方案了,这里就不列举了,这里就假设读者已经能够将so注入到别的进程并顺利运行了.

首先贴一下这次的目标

package com.example.testar;
 
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
 
import dalvik.system.DexClassLoader;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.text.GetChars;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
 
public class MainActivity extends Activity {
    private final Map<String, ClassLoader> mLoaders = new HashMap<String, ClassLoader>();
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        Button btn = (Button) findViewById(R.id.button1);
        btn.setOnClickListener(new View.OnClickListener() {
 
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
                WifiInfo info = wifi.getConnectionInfo();
                System.out.println("Wifi mac :" + info.getMacAddress());
                System.out.println("return " + test());
            }
        });
    }
 
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
 
    private String test() {
        return "real";
    }
}

我们的目标是上面的test()方法,我们要改变其返回值.

接下来看看我们要注入到目标进程的so.cpp, MethodHooker.cpp

so.cpp:
#include "jni.h"
#include "android_runtime/AndroidRuntime.h"
#include "android/log.h"
#include "stdio.h"
#include "stdlib.h"
#include "MethodHooker.h"
#include <utils/CallStack.h>
#include "art.h"
#define log(a,b) __android_log_write(ANDROID_LOG_INFO,a,b); // LOG Ѝ:info
#define log_(b) __android_log_write(ANDROID_LOG_INFO,"JNI_LOG_INFO",b); // LOG Ѝ:info
 
 
extern "C" void InjectInterface(char*arg){
    log_("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
    log_("*-*-*-*-*-* Injected so *-*-*-*-*-*-*-*");
    log_("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
    Hook();
    log_("*-*-*-*-*-*-*- End -*-*-*-*-*-*-*-*-*-*");
}
 
extern "C" JNIEXPORT jstring JNICALL Java_com_example_testar_InjectApplication_test(JNIEnv *env, jclass clazz)
{
    Abort_();
    return env->NewStringUTF("haha ");;
}
MethodHooker.cpp:
#include "MethodHooker.h"
#include "jni.h"
#include "android_runtime/AndroidRuntime.h"
#include "android/log.h"
#include "stdio.h"
#include "stdlib.h"
#include "native.h"
#include <dlfcn.h>
#define ANDROID_SMP 0
#include "Dalvik.h"
#include "alloc/Alloc.h"
 
#include "art.h"
 
#define ALOG(...) __android_log_print(ANDROID_LOG_VERBOSE, __VA_ARGS__)
 
static bool g_bAttatedT;
static JavaVM *g_JavaVM;
 
void init()
{
    g_bAttatedT = false;
    g_JavaVM = android::AndroidRuntime::getJavaVM();
}
 
static JNIEnv *GetEnv()
{
    int status;
    JNIEnv *envnow = NULL;
    status = g_JavaVM->GetEnv((void **)&envnow, JNI_VERSION_1_4);
    if(status < 0)
    {
        status = g_JavaVM->AttachCurrentThread(&envnow, NULL);
        if(status < 0)
        {
            return NULL;
        }
        g_bAttatedT = true;
    }
    return envnow;
}
 
static void DetachCurrent()
{
    if(g_bAttatedT)
    {
        g_JavaVM->DetachCurrentThread();
    }
}
 
static int computeJniArgInfo(const DexProto* proto)
{
    const char* sig = dexProtoGetShorty(proto);
    int returnType, jniArgInfo;
    u4 hints;
 
    /* The first shorty character is the return type. */
    switch (*(sig++)) {
    case 'V':
        returnType = DALVIK_JNI_RETURN_VOID;
        break;
    case 'F':
        returnType = DALVIK_JNI_RETURN_FLOAT;
        break;
    case 'D':
        returnType = DALVIK_JNI_RETURN_DOUBLE;
        break;
    case 'J':
        returnType = DALVIK_JNI_RETURN_S8;
        break;
    case 'Z':
    case 'B':
        returnType = DALVIK_JNI_RETURN_S1;
        break;
    case 'C':
        returnType = DALVIK_JNI_RETURN_U2;
        break;
    case 'S':
        returnType = DALVIK_JNI_RETURN_S2;
        break;
    default:
        returnType = DALVIK_JNI_RETURN_S4;
        break;
    }
 
    jniArgInfo = returnType << DALVIK_JNI_RETURN_SHIFT;
 
    hints = dvmPlatformInvokeHints(proto);
 
    if (hints & DALVIK_JNI_NO_ARG_INFO) {
        jniArgInfo |= DALVIK_JNI_NO_ARG_INFO;
    } else {
        assert((hints & DALVIK_JNI_RETURN_MASK) == 0);
        jniArgInfo |= hints;
    }
 
    return jniArgInfo;
}
 
int ClearException(JNIEnv *jenv){
    jthrowable exception = jenv->ExceptionOccurred();
    if (exception != NULL) {
        jenv->ExceptionDescribe();
        jenv->ExceptionClear();
        return true;
    }
    return false;
}
 
bool isArt(){
    return true;
}
 
static jclass findAppClass(JNIEnv *jenv,const char *apn){
    //񈡌oaders
    jclass clazzApplicationLoaders = jenv->FindClass("android/app/ApplicationLoaders");
    jthrowable exception = jenv->ExceptionOccurred();
    if (ClearException(jenv)) {
        ALOG("Exception","No class : %s", "android/app/ApplicationLoaders");
        return NULL;
    }
    jfieldID fieldApplicationLoaders = jenv->GetStaticFieldID(clazzApplicationLoaders,"gApplicationLoaders","Landroid/app/ApplicationLoaders;");
    if (ClearException(jenv)) {
        ALOG("Exception","No Static Field :%s","gApplicationLoaders");
        return NULL;
    }
    jobject objApplicationLoaders = jenv->GetStaticObjectField(clazzApplicationLoaders,fieldApplicationLoaders);
    if (ClearException(jenv)) {
        ALOG("Exception","GetStaticObjectField is failed [%s","gApplicationLoaders");
        return NULL;
    }
    jfieldID fieldLoaders = jenv->GetFieldID(clazzApplicationLoaders,"mLoaders","Ljava/util/Map;");
    if (ClearException(jenv)) {
        ALOG("Exception","No Field :%s","mLoaders");
        return NULL;
    }
    jobject objLoaders = jenv->GetObjectField(objApplicationLoaders,fieldLoaders);
    if (ClearException(jenv)) {
        ALOG("Exception","No object :%s","mLoaders");
        return NULL;
    }
    //̡ȡmap֐Ķalues
    jclass clazzHashMap = jenv->GetObjectClass(objLoaders);
    jmethodID methodValues = jenv->GetMethodID(clazzHashMap,"values","()Ljava/util/Collection;");
    jobject values = jenv->CallObjectMethod(objLoaders,methodValues);
 
    jclass clazzValues = jenv->GetObjectClass(values);
    jmethodID methodToArray = jenv->GetMethodID(clazzValues,"toArray","()[Ljava/lang/Object;");
    if (ClearException(jenv)) {
        ALOG("Exception","No Method:%s","toArray");
        return NULL;
    }
 
    jobjectArray classLoaders = (jobjectArray)jenv->CallObjectMethod(values,methodToArray);
    if (ClearException(jenv)) {
        ALOG("Exception","CallObjectMethod failed :%s","toArray");
        return NULL;
    }
 
        int size = jenv->GetArrayLength(classLoaders);
 
        for(int i = 0 ; i < size ; i ++){
            jobject classLoader = jenv->GetObjectArrayElement(classLoaders,i);
            jclass clazzCL = jenv->GetObjectClass(classLoader);
            jmethodID loadClass = jenv->GetMethodID(clazzCL,"loadClass","(Ljava/lang/String;)Ljava/lang/Class;");
            jstring param = jenv->NewStringUTF(apn);
            jclass tClazz = (jclass)jenv->CallObjectMethod(classLoader,loadClass,param);
            if (ClearException(jenv)) {
                ALOG("Exception","No");
                continue;
            }
            return tClazz;
        }
    ALOG("Exception","No");
    return NULL;
}
 
 
 
bool HookDalvikMethod(jmethodID jmethod){
    Method *method = (Method*)jmethod;
    //ؼ!!Ŀ귽ОĎnative
    SET_METHOD_FLAG(method, ACC_NATIVE);
 
    int argsSize = dvmComputeMethodArgsSize(method);
    if (!dvmIsStaticMethod(method))
        argsSize++;
 
    method->registersSize = method->insSize = argsSize;
 
    if (dvmIsNativeMethod(method)) {
        method->nativeFunc = dvmResolveNativeMethod;
        method->jniArgInfo = computeJniArgInfo(&method->prototype);
    }
}
 
bool ClassMethodHook(HookInfo info){
 
    JNIEnv *jenv = GetEnv();
 
    jclass clazzTarget = jenv->FindClass(info.tClazz);
    if (ClearException(jenv)) {
        ALOG("Exception","ClassMethodHook[Can't find class:%s in bootclassloader",info.tClazz);
 
        clazzTarget = findAppClass(jenv,info.tClazz);
        if(clazzTarget == NULL){
            ALOG("Exception","%s","Error in findAppClass");
            return false;
        }
    }
 
    jmethodID method = jenv->GetMethodID(clazzTarget,info.tMethod,info.tMeihodSig);
    if(method==NULL){
        ALOG("Exception","ClassMethodHook[Can't find method:%s",info.tMethod);
        return false;
    }
 
    if(isArt()){
        HookArtMethod(jenv,method);
    }else{
        HookDalvikMethod(method);
    }
 
    JNINativeMethod gMethod[] = {
        {info.tMethod, info.tMeihodSig, info.handleFunc},
    };
 
    //funcΪNULLʱהА󶨬󃦀չɍ
    if(info.handleFunc != NULL){
        //ؼ!!Ŀ귽؁הҥĮative
        if (jenv->RegisterNatives(clazzTarget, gMethod, 1) < 0) {
            ALOG("RegisterNatives","err");
            return false;
        }
    }
 
    DetachCurrent();
    return true;
}
 
int Hook(){
    init();
    void* handle = dlopen("/data/local/libTest.so",RTLD_NOW);
    const char *dlopen_error = dlerror();
    if(!handle){
        ALOG("Error","cannt load plugin :%s",dlopen_error);
        return -1;
    }
    SetupFunc setup = (SetupFunc)dlsym(handle,"getpHookInfo");
    const char *dlsym_error = dlerror();
    if (dlsym_error) {
        ALOG("Error","Cannot load symbol 'getpHookInfo' :%s" , dlsym_error);
        dlclose(handle);
        return 1;
    }
 
    HookInfo *hookInfo;
    setup(&hookInfo);
 
    ALOG("LOG","Target Class:%s",hookInfo[0].tClazz);
    ALOG("LOG","Target Method:%s",hookInfo[0].tMethod);
 
    ClassMethodHook(hookInfo[0]);
}

以下是我们想要的目标进程java世界执行的我们自定义的代码

libTest.so
#include "native.h"
#include <android/log.h>
#include "stdio.h"
#include "stdlib.h"
#include "MethodHooker.h"
 
#define log(a,b) __android_log_print(ANDROID_LOG_VERBOSE,a,b); // LOG Ѝ:info
#define log_(b) __android_log_print(ANDROID_LOG_VERBOSE,"JNI_LOG_INFO",b); // LOG Ѝ:info
 
int getpHookInfo(HookInfo** pInfo);
 
JNIEXPORT void JNICALL Java_com_example_testar_InjectClassloader_hookMethodNative
  (JNIEnv * jenv, jobject jboj, jobject jobj, jclass jclazz, jint slot)
{
    //log("TestAE","start Inject other process");
}
 
JNIEXPORT jstring JNICALL test(JNIEnv *env, jclass clazz) 
{ 
    //__android_log_print(ANDROID_LOG_VERBOSE, "tag", "call <native_printf> in java");
    return (*env)->NewStringUTF(env,"haha ");;
}
 
HookInfo hookInfos[] = {
        {"android/net/wifi/WifiInfo","getMacAddress","()Ljava/lang/String;",(void*)test},
        //{"com/example/testar/MainActivity","test","()Ljava/lang/String;",(void*)test},
        //{"android/app/ApplicationLoaders","getText","()Ljava/lang/CharSequence;",(void*)test},
};
 
int getpHookInfo(HookInfo** pInfo){
    *pInfo = hookInfos;
    return sizeof(hookInfos) / sizeof(hookInfos[0]);
}

程序大致的流程是这样的,首先将so.so注入到目标进程,执行里面的Hook()函数,然后Hook()加载libTest.so,获取里面定义的Hook信息.接着用ClassMethodHook挂钩java世界的方法.

    关键一,从native世界进入java世界.熟悉jni编程的都知道,java到native的桥梁是JNIEnv,我们只要获得一个JNIEnv就能进入到java世界了.突破点就在AndroidRuntime,android::AndroidRuntime::getJavaVM();这个静态方法能够获取一个JavaVM, JavaVM->GetEnv方法能够获得一个JNIEnv了.JNIEnv是和线程相关的,使用前一定记得将其附加到当前进程,也要在适当的时候将其销毁.

    关键二,怎么影响内存里的java代码,这个情况替换内存是不现实的,但是可以取巧.我们知道java代码里将一个方法声明为native方法时,对此函数的调用就会到native世界里找.我们何不在运行时将一个不是native的方法修改成native方法呢?这是可以做到的,看着段代码

bool HookDalvikMethod(jmethodID jmethod){
    Method *method = (Method*)jmethod;
    //ؼ!!Ŀ귽ОĎnative
    SET_METHOD_FLAG(method, ACC_NATIVE);
 
    int argsSize = dvmComputeMethodArgsSize(method);
    if (!dvmIsStaticMethod(method))
        argsSize++;
 
    method->registersSize = method->insSize = argsSize;
 
    if (dvmIsNativeMethod(method)) {
        method->nativeFunc = dvmResolveNativeMethod;
        method->jniArgInfo = computeJniArgInfo(&method->prototype);
    }
}

Jni反射调用java方法时要用到一个jmethodID指针,这个指针在Dalvik里其实就是Method类,通过修改这个类的一些属性就可以实现在运行时将一个方法修改成native方法.

SET_METHOD_FLAG(method, ACC_NATIVE); 就是这么做的,其后面的代码就是设定native函数的参数占用内存大小统计.

    也许你发现了,虽然将其修改成一个native方法了,但是这个方法对应的native代码在那里呢?这样做

//ؼ!!Ŀ귽؁הҥĮative
        if (jenv->RegisterNatives(clazzTarget, gMethod, 1) < 0) {
            ALOG("RegisterNatives","err");
            return false;
        }

可以将一个native函数绑定到一个java的native方法

    这样就能够实现开始的目标了!

    我这里讲得是有点粗略了,但是这个技术牵涉到的知识太多了,主要是给老鸟参考的,小菜们拿来用用就好,要是要讲得小菜们都能明白,就不知要讲到何年何月了.还有就是上面的art环境的代码是跑不起来的,等我后面有空完善了再发一次吧!

Hook Java的的一个改进版本
《注入安卓进程，并Hook java世界的方法》这篇好文相信大家都看这，里面所提到的方法估
计大家也都试过。不过里面的所用的方法，我发现有两个可以改进的地方。
改进点一：更简单地修改java方法为本地方法

...
// hook method
int argsSize = calcMethodArgsSize(method->shorty);
if (!dvmIsStaticMethod(method))
argsSize++;
SET_METHOD_FLAG(method, ACC_NATIVE);
method->registersSize = method->insSize = argsSize;
method->outsSize = 0;
method->jniArgInfo = dvmComputeJniArgInfo(method->shorty);
// save info to insns
method->insns = (u2*)info;
// bind the bridge func，only one line
method->nativeFunc = method_handler;
LOGI("[+] %s->%s was hooked\n", classDesc, methodName);
...

直接把method->nativeFunc即可，无需重新调用JNIEnv的RegisterNatives方法，其中
method_handler可以是下面两种形式之一：

typedef void (*DalvikBridgeFunc)(const u4* args, JValue* pResult, const
Method* method, struct Thread* self);
typedef void (*DalvikNativeFunc)(const u4* args, JValue* pResult);

这样有一个好处，就是所有java方法都可以统一指向同一个native func，而不需要像为每一个java method方法指定一个native func。
改进点二：方法回调避免线程安全问题
原来的方法，是这样的

//hook之前先拷⻉
uint mlen = sizeof(Method);
Method *oldMeth = (Method*)malloc(mlen);
memcpy(oldMeth,method,mlen);
info->odlMethod = oldMeth;
info->curMethod = method;
//回调后再拷⻉回来，再通过jni->callXXXXMethod调⽤，之后再重新hook
memcpy(hi->curMethod,hi->odlMethod,mlen);
jmethodID om = (jmethodID)hi->curMethod;
jenv->CallVoidMethod(me,om,gDevice_Sensors);
ClassMethodHook(jenv,&baiduhookInfos[0]);

这个方法，其实是有线程安全问题的，其中在dalvik中，有很多方法可以直接调用Method对象，比如dvmCallMethod, dvmCallMethodA, dvmCallMethodV,dvmInvokeMethod等等。针对DalvikBridgeFunc和DalvikNativeFunc的参数，我最后选择使用dvmInvokeMethod，这个函数的原型是这样的：

Object* dvmInvokeMethod(Object* obj, const Method* method, ArrayObject*
argList, ArrayObject* params, ClassObject* returnType, bool noAccessCheck)

其中，obj是this或者null（如果是static方法），method可以直接使用hook之前copy的对象，比较麻烦是argList，params和returnType的获取。获取argList的方法，我在Proxy.cpp中到了现成的boxMethodArgs方法，而returnType通过Reflect.h中dvmGetBoxedReturnType的方法也可以获取，而剩下的params只能自己写代码了，下面是我的代码：

STATIC ArrayObject* dvmGetMethodParamTypes(const Method* method, const char*
methodsig){
/* count args */
size_t argCount = dexProtoGetParameterCount(&method->prototype);
STATIC ClassObject* java_lang_object_array = dvmFindSystemClass("
[Ljava/lang/Object;");
/* allocate storage */
ArrayObject* argTypes = dvmAllocArrayByClass(java_lang_object_array,
argCount, ALLOC_DEFAULT);
if(argTypes == NULL){
return NULL;
}
Object** argObjects = (Object**) argTypes->contents;
const char *desc = (const char *)(strchr(methodsig, '(') + 1);
/*
* Fill in the array.
*/
size_t desc_index = 0;
size_t arg_index = 0;
bool isArray = false;
char descChar = desc[desc_index];
while (descChar != ')') {
switch (descChar) {
case 'Z':
case 'C':
case 'F':
case 'B':
case 'S':
case 'I':
case 'D':
case 'J':
if(!isArray){
argObjects[arg_index++] = dvmFindPrimitiveClass(descChar);
isArray = false;
}else{
char buf[3] = {0};
memcpy(buf, desc + desc_index - 1, 2);
argObjects[arg_index++] = dvmFindSystemClass(buf);
}
desc_index++;
break;
case '[':
isArray = true;
desc_index++;
break;
case 'L':
int s_pos = desc_index, e_pos = desc_index;
while(desc[++e_pos] != ';');
s_pos = isArray ? s_pos - 1 : s_pos;
isArray = false;
size_t len = e_pos - s_pos + 1;
char buf[128] = { 0 };
memcpy((void *)buf, (const void *)(desc + s_pos), len);
argObjects[arg_index++] = dvmFindClass(buf);
desc_index = e_pos + 1;
break;
}
descChar = desc[desc_index];
}
return argTypes;
}

通过上面几个类型的获取之后，最后再看一下整个method hook的实现，过程其实大同小异，不过直接把上述提及的向种类型信息预先获取并保存到method->insns里头了：

extern int __attribute__ ((visibility ("hidden")))
dalvik_java_method_hook(JNIEnv* env, HookInfo *info) {
const char* classDesc = info->classDesc;
const char* methodName = info->methodName;
const char* methodSig = info->methodSig;
const bool isStaticMethod = info->isStaticMethod;
jclass classObj = dvmFindJNIClass(env, classDesc);
if (classObj == NULL) {
LOGE("[-] %s class not found", classDesc);
return -1;
}
jmethodID methodId =
isStaticMethod ?
env->GetStaticMethodID(classObj, methodName, methodSig)
:
env->GetMethodID(classObj, methodName, methodSig);
if (methodId == NULL) {
LOGE("[-] %s->%s method not found", classDesc, methodName);
return -1;
}
// backup method
Method* method = (Method*) methodId;
if(method->nativeFunc == method_handler){
LOGW("[*] %s->%s method had been hooked", classDesc, methodName);
return -1;
}
Method* bakMethod = (Method*) malloc(sizeof(Method));
memcpy(bakMethod, method, sizeof(Method));
// init info
info->originalMethod = (void *)bakMethod;
info->returnType = (void *)dvmGetBoxedReturnType(bakMethod);
info->paramTypes = dvmGetMethodParamTypes(bakMethod, info->methodSig);
// hook method
int argsSize = calcMethodArgsSize(method->shorty);
if (!dvmIsStaticMethod(method))
argsSize++;
SET_METHOD_FLAG(method, ACC_NATIVE);
method->registersSize = method->insSize = argsSize;
method->outsSize = 0;
method->jniArgInfo = dvmComputeJniArgInfo(method->shorty);
// save info to insns
method->insns = (u2*)info;
// bind the bridge func，only one line
method->nativeFunc = method_handler;
LOGI("[+] %s->%s was hooked\n", classDesc, methodName);
return 0;
}

然后是method_handler的实现，这个方法是所有java方法的跳转函数，所以在这里可以注册
callback，不过这部分逻辑我没有做上，有兴趣的朋友可以加上。

STATIC void method_handler(const u4* args, JValue* pResult, const Method*
method, struct Thread* self){
HookInfo* info = (HookInfo*)method->insns; //get hookinfo pointer from
method-insns
LOGI("entry %s->%s", info->classDesc, info->methodName);
Method* originalMethod = reinterpret_cast<Method*>(info->originalMethod);
Object* thisObject = (Object*)args[0];
ArrayObject* argTypes = dvmBoxMethodArgs(originalMethod, args + 1); 
pResult->l = (void *)dvmInvokeMethod(thisObject, originalMethod,
argTypes, (ArrayObject *)info->paramTypes, (ClassObject *)info->returnType,
true);
dvmReleaseTrackedAlloc((Object *)argTypes, self);
}

最后通过dvmInvokeMethod就可以直接调回原来的函数了。
最后
写这个代码，主要是因为我在工作中要注入到某个系统进程，然后要hook java中的某些方法，但用cydia和xposed感觉太笨重了，特别是xposed，里面的很多参数的boxed/unboxed都是通过jni模块自动转换的，整个框架已经离不开dex文件了。所以才想自己实现一套纯本地的java hook代码，而《注入安卓进程，并Hook java世界的方法》所介绍的方法，我感觉用起来不太方便，跟cydia和xposed两个框架的主要区别就是缺少了一个“中转函数”，所以而有了本码。