cocos2dx-Lua引擎游戏脚本及图片资源解密与DUMP

Cocos2d-x 2019-05-18

分析目标

下面分析的主要是少年三国志。

Lua脚本解密与DUMP

  • LuaJit IDA分析调用树：

    1. AppDelegate::applicationDidFinishLaunching(AppDelegate *__hidden this) EXPORT _ZN11AppDelegate29applicationDidFinishLaunchingEv

    2. cocos2d::ccluaEngine::defaultEngine(cocos2d::ccluaEngine *__hidden this) EXPORT _ZN7cocos2d11ccluaEngine13defaultEngineEv

    3. cocos2d::ccluaEngine::init(cocos2d::ccluaEngine *__hidden this)
      EXPORT _ZN7cocos2d11ccluaEngine4initEv

    4. cocos2d::ccluaStack::create(cocos2d::ccluaStack *__hidden this)
      EXPORT _ZN7cocos2d10ccluaStack6createEv

    5. cocos2d::ccluaStack::init(cocos2d::ccluaStack *__hidden this)
      EXPORT _ZN7cocos2d10ccluaStack4initEv

    6. cocos2dx_lua_loader

    7. cocos2d::ccluaStack::lua_loadbuffer(lua_State ,char const,int,char const*)
      EXPORT ZN7cocos2d10ccluaStack14lua_loadbufferEP9lua_StatePKciS4

cocos2d::ccluaStack::lua_loadbuffer先调用以下函数解密： cocos2d::extra::CCCrypto::decryptUF(uchar ,int ,int *) EXPORT ZN7cocos2d5extra8CCCrypto9decryptUFEPhiPiS3
最后再调用：luaL_loadbuffer

因此可以直接对luaL_loadbuffer进行HOOK，进而DUMP出Lua脚本，网上搜索函数声明：

int luaL_loadbuffer (lua_State *L,const char *buff,size_t sz,const char *name);

进而实现HOOK代码：

//orig function copy
int (*luaL_loadbuffer_orig)(void *L,int size,const char *name) = NULL;

//local function
int luaL_loadbuffer_mod(void *L,const char *name) {
    LOGD("[dumplua] luaL_loadbuffer name: %s lua: %s",name,buff);
    return luaL_loadbuffer_orig(L,buff,size,name);
}

void hook() {
    LOGD("[dumplua] hook begin");
    void *handle = dlopen("libgame.so",RTLD_Now);
    if (handle == NULL) {
        LOGE("[dumplua]dlopen err: %s.",dlerror());
        return;
    }else{
        LOGD("[dumplua] libgame.so dlopen OK!");
    }


    void *pluaL_loadbuffer = dlsym(handle,"luaL_loadbuffer");
    if (pluaL_loadbuffer == NULL){
        LOGE("[dumplua] lua_loadbuffer not found!");
        LOGE("[dumplua] dlsym err: %s.",dlerror());
    }else{
        LOGD("[dumplua] luaL_loadbuffer found!");
        MSHookFunction(pluaL_loadbuffer,(void *)&luaL_loadbuffer_mod,(void **)&luaL_loadbuffer_orig);
    }
}

运行后拦截到的输出信息：

01-05 19:29:27.674 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: assets/scripts/main.lua lua: 
    function __G__TRACKBACK__(errorMessage)

      print("----------------------------------------")
      print("LUA ERROR: " .. tostring(errorMessage) .. "\n")
      local traceback = debug.traceback("",2)
      print(traceback)
      print("----------------------------------------")


      --只有G_Report初始过后才会对错误日志做处理
      if G_Report ~= nil then
          G_Report:onTrackBack(errorMessage,traceback)
      end


      if SHOW_EXCEPTION_TIP and uf_notifyLayer ~= nil then 
        uf_notifyLayer:getDebugNode():removeChildByTag(10000)
        local text = tostring(errorMessage)
          require("upgrade.ErrMsgBox").showErrorMsgBox(text)

      end
    end



    function traceMem(desc)
      if desc == nil then
          desc = "memory:"
      end


      if ccluaObjcBridge then
          local callStaticmethod = ccluaObjcBridge.callStaticmethod

          local ok,ret = callStaticmethod("NativeProxy","getUsedMemory",nil)

          if ok then
              pri
01-05 19:29:27.679 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.AntiAddictionLayer lua: LJ-
01-05 19:29:27.679 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.ComSdkUtils lua: LJA
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.config lua: LJ�    
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.ConfigLayer lua: LJ]
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.EffectNode_Upgrade lua: LJ�
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.ErrMsgBox lua: LJP
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.game lua: LJ�
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.NativeCallUtils lua: LJ�
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.NativeProxy lua: LJ�
01-05 19:29:27.684 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.Patcher lua: LJ�
01-05 19:29:27.689 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.SplashLayer lua: LJ-
01-05 19:29:27.689 13191-13215/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: upgrade.upgrade lua: LJ6

可见，有些Lua脚本是源码形式，有些是LuaJit编译的，可以改写以上代码把脚本DUMP到文件中再进一步分析，此处略。

资源解密与DUMP

主要函数： cocos2d::CCImage::initWithImageFile调用 cocos2d::CCImage::initWithImageData

但是IDA分析发现initWithImageData会调用cocos2d::extra::CCCrypto::decryptXXTEA和cocos2d::extra::CCCrypto::decryptUF进行解密，最后再加载图片资源。以下是initWithImageData部分代码：

if ( s )
  {
    v12 = (unsigned __int8 *)strlen(s);
    v13 = (void *)cocos2d::extra::CCCrypto::decryptXXTEA(v9,v11,(int)s,v12,(int)v24,v22);
    v14 = v13;
    if ( v13 )
      v9 = (cocos2d::extra::CCCrypto *)v13;
    goto LABEL_28;
  }
  v14 = 0;
  if ( (signed int)a3 > 3 && *(_BYTE *)this == 85 && *((_BYTE *)this + 1) == 70 )
  {
    v25 = 0;
    cocos2d::extra::CCCrypto::decryptUF(this,(int)a3,(int)&v25,v24,v21);
    v15 = v25 >> 4;
    if ( (v25 & 0xFu) <= 9 )
      *(_DWORD *)(v8 + 36) = v25 & 0xF;
    switch ( v15 )
    {
      case 1:
        v16 = 1067030938;
        break;
      case 2:
        v16 = 1068708659;

也即会调用cocos2d::extra::CCCrypto::decryptXXTEA和cocos2d::extra::CCCrypto::decryptUF进行解密操作。我们看下cocos2d::extra::CCCrypto::decryptUF这个函数，通过IDA的F5插件，并不断修改变量名可以获得一个比较清晰的C代码。

int __fastcall cocos2d::extra::CCCrypto::decryptUF(cocos2d::extra::CCCrypto *pInBuff,int nlen,int a3,int *pOutLen,int *name)
{
  cocos2d::extra::CCCrypto *pInBuff2; // r5@1
  int *pOutLen2; // r7@1
  int v7; // r3@4
  int v8; // r6@5
  int v9; // r1@6
  int result; // r0@9
  int v11; // r4@10
  int v12; // r6@12
  int v13; // r6@15
  signed int v14; // r0@19
  int v15; // [sp+0h] [bp-28h]@5
  int v16; // [sp+0h] [bp-28h]@10
  int v17; // [sp+4h] [bp-24h]@5

  pInBuff2 = pInBuff;
  pOutLen2 = pOutLen;
  if ( nlen <= 3 )
  {
    v14 = 1;
    return -v14;
  }
  if ( *(_BYTE *)pInBuff != 'U' || *((_BYTE *)pInBuff + 1) != 'F' )
  {
    v14 = 2;
    return -v14;
  }
  *(_DWORD *)a3 = *((_BYTE *)pInBuff + 2);
  v7 = *((_BYTE *)pInBuff + 3);
  if ( v7 == 1 )
  {
    v15 = nlen - 5;
    v17 = *((_BYTE *)pInBuff + 4);
    v8 = 0;
    while ( v8 < v15 )
    {
      v9 = (v8++ + v17) % 0x21;
      *(_BYTE *)pInBuff2 = *((_BYTE *)pInBuff2 + 5) ^ byte_6D192C[v9];
      pInBuff2 = (cocos2d::extra::CCCrypto *)((char *)pInBuff2 + 1);
    }
    *pOutLen2 = v15;
  }
  else
  {
    result = 0;
    if ( v7 != 2 )
      return result;
    v11 = 0;
    v16 = *((_BYTE *)pInBuff2 + 4);
    do
    {
      *((_BYTE *)pInBuff2 + v11) = *((_BYTE *)pInBuff2 + nlen + v11 - 5) ^ byte_6D192C[(v11 + v16) % 33 + 33];
      ++v11;
    }
    while ( v11 != 5 );
    v12 = nlen - 10;
    if ( nlen - 10 > 95 )
      v12 = 95;
    v13 = v12 + 4;
    while ( v13 >= v11 )
    {
      *((_BYTE *)pInBuff2 + v11) ^= byte_6D192C[(v11 + v16) % 33 + 33];
      ++v11;
    }
    *pOutLen2 = nlen - 5;
  }
  return 0;
}

其实看到这里应该也是比较容易逆向分析出解密的算法的，应该说比较简单，可以直接写一个脚本来解密assets里的资源。但是为了保证通用性，还是写HOOK代码比较好。

本来分析以为最终都会调用_initWithWebpData、_initWithJpgData、_initWithBpgData、_initWithPngData、_initWithTiffData、_initWithRawData这些函数的，但是实际上分别HOOK后并没有被拦截，所以最后还是HOOK了下cocos2d::extra::CCCrypto::decryptUF。

static string g_strDataPath;
static int g_nCount = 1;

string getNextFilePath(const char *fileExt) {
    char buff[100] = {0};
    ++g_nCount;
    sprintf(buff,"%s/cache/%d%s",g_strDataPath.c_str(),g_nCount,fileExt);
    return buff;
}

bool saveFile(const void* addr,int len,const char *outFileName)
{
    bool bSuccess = false;
    FILE* file = fopen(outFileName,"wb+");
    if (file != NULL) {
        fwrite(addr,len,1,file);
        fflush(file);
        fclose(file);
        bSuccess = true;
        chmod(outFileName,S_IRWXU | S_IRWXG | S_IRWXO);
    }else{
        LOGE("[%s] fopen Failed,error: %s",__FUNCTION__,dlerror());
    }

    return bSuccess;
}

//hook decryptUF
int (*decryptUF_orig)(void *pInBuff,int *n,int *poutlen,char *name) = NULL;
int decryptUF_mod(void *pInBuff,char *name) {
    int ret = decryptUF_orig(pInBuff,n,poutlen,name);
    saveFile(pInBuff,*poutlen,getNextFilePath(".png").c_str());
    return ret;
}

void hook() {
    //hook decryptUF
    void *decryptUF = dlsym(handle,"_ZN7cocos2d5extra8CCCrypto9decryptUFEPhiPiS3_");
    if ( decryptUF==NULL ) {
        LOGE("[dumplua] _ZN7cocos2d5extra8CCCrypto9decryptUFEPhiPiS3_ (decryptUF) not found!");
        LOGE("[dumplua] dlsym err: %s.",dlerror());
    }else{
        LOGD("[dumplua] _ZN7cocos2d5extra8CCCrypto9decryptUFEPhiPiS3_ (decryptUF) found!");
        MSHookFunction(decryptUF,(void *)&decryptUF_mod,(void **)&decryptUF_orig);
    }
}

我这里图方便把所有解密的数据都DUMP为/data/data/packagename/cache目录下扩展名为PNG的文件了，最后通过脚本从手机中批量提取出解密后的文件：

#coding:utf-8
import os

for i in range(1,10000):
    cmd = 'adb pull /data/data/com.youzu.android.snsgz/cache/' + str(i) +'.png' + ' e:\\test'
    os.system(cmd)


其实通过上面的分析就可以知道，图片资源的解密和Lua的解密都是调用了相同的函数，因此解密出的文件不全是图片，还有写LuaJit的脚本文件，用十六进制编辑器打开就可以看到LJ开头的魔法数字。

全民水浒

全民水浒这个比较简单，资源直接没加密处理，解压缩APK文件就可以在assets目录下查看了。Lua脚本可以通过HOOK函数luaL_loadbuffer获得，而且可以看出只是对编译的Lua脚本做了简单的加密，可以直接DUMP出来，相对少年三国志稍微弱了一些。

01-05 20:04:16.569 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: require "UpdateScene.lua" lua: require "UpdateScene.lua"
01-05 20:04:16.574 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: UpdateScene.lua lua: LuaQ
01-05 20:04:16.574 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: Modal.lua lua: LuaQ
01-05 20:04:16.574 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: UIDefine.lua lua: LuaQ
01-05 20:04:16.574 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: MessageBox.lua lua: LuaQ
01-05 20:04:16.579 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: SoundManager.lua lua: LuaQ
01-05 20:04:16.579 17729-17886/? D/SUBSTRATEHOOK: [dumplua] luaL_loadbuffer name: SoundConfig.lua lua: LuaQ

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