cocos2dx-Lua引擎游戏脚本及图片资源解密与DUMP

分析目标

少年三国志，包名：com.youzu.android.snsgz
全民水浒，包名：com.tencent.Q108

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 ,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, const char *buff, int size, const char *name) = NULL;//local function
int luaL_loadbuffer_mod(void *L, const char *buff, int size, 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 thenG_Report:onTrackBack(errorMessage, traceback)endif SHOW_EXCEPTION_TIP and uf_notifyLayer ~= nil then uf_notifyLayer:getDebugNode():removeChildByTag(10000)local text = tostring(errorMessage)require("upgrade.ErrMsgBox").showErrorMsgBox(text)endendfunction traceMem(desc)if desc == nil thendesc = "memory:"endif CCLuaObjcBridge thenlocal callStaticMethod = CCLuaObjcBridge.callStaticMethodlocal ok, ret = callStaticMethod("NativeProxy", "getUsedMemory", nil)if ok thenpri
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@1int *pOutLen2; // r7@1int v7; // r3@4int v8; // r6@5int v9; // r1@6int result; // r0@9int v11; // r4@10int v12; // r6@12int v13; // r6@15signed int v14; // r0@19int v15; // [sp+0h] [bp-28h]@5int v16; // [sp+0h] [bp-28h]@10int v17; // [sp+4h] [bp-24h]@5pInBuff2 = 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 len, int *n, int *poutlen, char *name) = NULL;
int decryptUF_mod(void *pInBuff, int len, int *n, int *poutlen, char *name) {int ret = decryptUF_orig(pInBuff, len, n, poutlen, name);saveFile(pInBuff, *poutlen, getNextFilePath(".png").c_str());return ret;
}void hook() {//hook decryptUFvoid *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 osfor 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