epic的使用和简单介绍

Epic 使用

gradle 中引入依赖: com.github.tiann:epic:0.12
使用方法

class ThreadMethodHook extends XC_MethodHook{
    @Override
    protected void beforeHookedMethod(MethodHookParam param) throws Throwable {
        super.beforeHookedMethod(param);
        Thread t = (Thread) param.thisObject;
        Log.i(TAG, "thread:" + t + ", started..");
    }

    @Override
    protected void afterHookedMethod(MethodHookParam param) throws Throwable {
        super.afterHookedMethod(param);
        Thread t = (Thread) param.thisObject;
        Log.i(TAG, "thread:" + t + ", exit..");
    }
}

DexposedBridge.hookAllConstructors(Thread.class, new XC_MethodHook() {
    @Override
    protected void afterHookedMethod(MethodHookParam param) throws Throwable {
        super.afterHookedMethod(param);
        Thread thread = (Thread) param.thisObject;
        Class<?> clazz = thread.getClass();
        if (clazz != Thread.class) {
            Log.d(TAG, "found class extend Thread:" + clazz);
            DexposedBridge.findAndHookMethod(clazz, "run", new ThreadMethodHook());
        }
        Log.d(TAG, "Thread: " + thread.getName() + " class:" + thread.getClass() +  " is created.");
    }
});
DexposedBridge.hookAllMethod(Thread.class, "run", new ThreadMethodHook());

3. 注意事项

不支持armeabi架构,如果项目仅支持armeabi架构,需要从armeabi-v7进行so库的复制。

简介

基于dynamic dispatch的dynamic callee-side rewriting来实现hook。

其实就是修改entrypoint 所指向的代码.

1）保证要Hook的method完成compile，也就是运行时要执行其compiled_code。

2）根据要Hook的method对应的art::mirror::ArtMethod找到compiled_code入口点。

3）在compiled_code的开始位置放置一段很短的跳转代码，称为“一段跳板”，作用是跳转到二段跳板。之所以弄一个一段跳板，是怕二段跳板太长，原方法的compiled_code区域放不下。

4）二段跳板会将一些必要的参数打包，调用Java-Bridge方法，并将打包在一起的参数，通过r3传递给Java-Bridge。

5）Java-Bridge方法取出传递进来的参数，然后根据r1、r2、r3以及sp（以Thumb2为例，除了r0~r3，剩余的参数会通过sp传递），构造出原方法的参数，最后调用DexposedBridge.handleHookedArtMethod。

6）由DexposedBridge.handleHookedArtMethod调用beforeHookedMethod、原方法和afterHookedMethod。

DexposedBridge.hookAllMethods入口跟踪：

public static Set<XC_MethodHook.Unhook> hookAllMethods(Class<?> hookClass, String methodName, XC_MethodHook callback) {
   Set<XC_MethodHook.Unhook> unhooks = new HashSet<XC_MethodHook.Unhook>();
   for (Member method : hookClass.getDeclaredMethods())
      if (method.getName().equals(methodName))
         unhooks.add(hookMethod(method, callback));
   return unhooks;
}

对传入的类进行遍历，然后匹配和传入的方法相同的方法mothod，取callbackhe和mothed调用hookMethod进行hook的操作.

   public static XC_MethodHook.Unhook hookMethod(Member hookMethod, XC_MethodHook callback) {
       if (!(hookMethod instanceof Method) && !(hookMethod instanceof Constructor<?>)) {
           throw new IllegalArgumentException("only methods and constructors can be hooked");
       }

       boolean newMethod = false;
       CopyOnWriteSortedSet<XC_MethodHook> callbacks;
       synchronized (hookedMethodCallbacks) {
           callbacks = hookedMethodCallbacks.get(hookMethod);
           if (callbacks == null) {
               callbacks = new CopyOnWriteSortedSet<XC_MethodHook>();
               hookedMethodCallbacks.put(hookMethod, callbacks);
               newMethod = true;
           }
       }

Logger.w(TAG, "hook: " + hookMethod + ", newMethod ? " + newMethod);

       callbacks.add(callback);
       if (newMethod) {
           if (Runtime.isArt()) {
               if (hookMethod instanceof Method) {
                   Epic.hookMethod(((Method) hookMethod));
               } else {
                   Epic.hookMethod(((Constructor) hookMethod));
               }
           } else {
...
           }
       }
       return callback.new Unhook(hookMethod);
   }

已经hook过得方法和回调会被存储在hookedMethodCallbacks中,如果方法已经被hook过的,会直接从map中取出来.Epic.hookMethod就是hook方法的入口.

public static boolean hookMethod(Method origin) {
    ArtMethod artOrigin = ArtMethod.of(origin);
    return hookMethod(artOrigin);
}

private static boolean hookMethod(ArtMethod artOrigin) {

    MethodInfo methodInfo = new MethodInfo();
    methodInfo.isStatic = Modifier.isStatic(artOrigin.getModifiers());
    final Class<?>[] parameterTypes = artOrigin.getParameterTypes();
    if (parameterTypes != null) {
        methodInfo.paramNumber = parameterTypes.length;
        methodInfo.paramTypes = parameterTypes;
    } else {
        methodInfo.paramNumber = 0;
        methodInfo.paramTypes = new Class<?>[0];
    }
    methodInfo.returnType = artOrigin.getReturnType();
    methodInfo.method = artOrigin;
    // 存储方法的地址和新的methodInfo
    originSigs.put(artOrigin.getAddress(), methodInfo);

    // 取消权限检查
    if (!artOrigin.isAccessible()) {
        artOrigin.setAccessible(true);
    }
    // 静态方法主动调用
    artOrigin.ensureResolved();

    long originEntry = artOrigin.getEntryPointFromQuickCompiledCode();
    if (originEntry == ArtMethod.getQuickToInterpreterBridge()) {
        Logger.i(TAG, "this method is not compiled, compile it now. current entry: 0x" + Long.toHexString(originEntry));
        // 未编译主动调用进行编译
        boolean ret = artOrigin.compile();
        if (ret) {
            originEntry = artOrigin.getEntryPointFromQuickCompiledCode();
            Logger.i(TAG, "compile method success, new entry: 0x" + Long.toHexString(originEntry));
        } else {
            Logger.e(TAG, "compile method failed...");
            return false;
            // return hookInterpreterBridge(artOrigin);
        }
    }
    // 备份
    ArtMethod backupMethod = artOrigin.backup();

    Logger.i(TAG, "backup method address:" + Debug.addrHex(backupMethod.getAddress()));
    Logger.i(TAG, "backup method entry :" + Debug.addrHex(backupMethod.getEntryPointFromQuickCompiledCode()));

    ArtMethod backupList = getBackMethod(artOrigin);
    if (backupList == null) {
        setBackMethod(artOrigin, backupMethod);
    }

    final long key = originEntry;
    final EntryLock lock = EntryLock.obtain(originEntry);
    //noinspection SynchronizationOnLocalVariableOrMethodParameter
    synchronized (lock) {
        if (!scripts.containsKey(key)) {
            scripts.put(key, new Trampoline(ShellCode, originEntry));
        }

        // dynamic callee-side rewriting 实现hook
        Trampoline trampoline = scripts.get(key);
        boolean ret = trampoline.install(artOrigin);
        // Logger.d(TAG, "hook Method result:" + ret);
        return ret;
    }
}

安装跳板,实现hook

public boolean install(ArtMethod originMethod){
    boolean modified = segments.add(originMethod);
    if (!modified) {
        // Already hooked, ignore
        Logger.d(TAG, originMethod + " is already hooked, return.");
        return true;
    }
    // 创建 Trampoline
    byte[] page = create();
    // Trampoline 写到一块新的内存中
    EpicNative.put(page, getTrampolineAddress());

    int quickCompiledCodeSize = Epic.getQuickCompiledCodeSize(originMethod);
    int sizeOfDirectJump = shellCode.sizeOfDirectJump();
    if (quickCompiledCodeSize < sizeOfDirectJump) {
        // complied_code 太短,无法安装一段跳板,complied_code 入口改为二段跳板
        Logger.w(TAG, originMethod.toGenericString() + " quickCompiledCodeSize: " + quickCompiledCodeSize);
        originMethod.setEntryPointFromQuickCompiledCode(getTrampolinePc());
        return true;
    }
    // 这里是绝对不能改EntryPoint的，碰到GC就挂(GC暂停线程的时候，遍历所有线程堆栈，如果被hook的方法在堆栈上，那就GG)
    // 安装一段跳板
    return activate();
}

private boolean activate() {
    long pc = getTrampolinePc();
    Logger.d(TAG, "Writing direct jump entry " + Debug.addrHex(pc) + " to origin entry: 0x" + Debug.addrHex(jumpToAddress));
    synchronized (Trampoline.class) {
        return EpicNative.activateNative(jumpToAddress, pc, shellCode.sizeOfDirectJump(),
                shellCode.sizeOfBridgeJump(), shellCode.createDirectJump(pc));
    }
}

1）创建Trampoline（包括“二段跳板”BridgeJump，和CallOrigin）

2）创建和安装“一段跳板”，完成Hook。

原文链接：https://blog.csdn.net/qq_35662742/article/details/121396264