-
-
cocos2d逆向入门和某捕鱼游戏分析
-
2021-7-20 12:05
-
初步认识cocos2d-x
先clone到本地
git clone https://github.com/cocos2d/cocos2d-x.git
Cocos2d-x是一个开源的移动2D游戏框架，底层支持各种平台，核心用c++封装了各种库，外面给了lua和c++的接口，所以关键代码可能在lua中，很多安卓游戏的逻辑也基本都在lua脚本里，盗用官网这张图
从c++进入lua世界
lua虚拟机相关代码在cocos2d-x\cocos\scripting\lua-bindings\manual里
CCLuaEngine.h lua引擎相关
CCLuaStack.h lua栈相关
进入虚拟机
cocos2d-x\templates\lua-template-default\frameworks\runtime-src\Classes\AppDelegate.cpp\AppDelegate::applicationDidFinishLaunching
applicationDidFinishLaunching函数
应用结束加载中进入lua虚拟机
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | bool AppDelegate::applicationDidFinishLaunching(){ // set default FPS Director::getInstance()->setAnimationInterval(1.0 / 60.0f);//设置fps刷新率 // register lua module auto engine = LuaEngine::getInstance();//创建lua虚拟机引擎 ScriptEngineManager::getInstance()->setScriptEngine(engine);//设置脚本引擎为lua引擎 lua_State* L = engine->getLuaStack()->getLuaState();//创建lua虚拟机环境lua_State lua_module_register(L); //分配网络，控制台，ui界面等相关联的寄存器 register_all_packages(); LuaStack* stack = engine->getLuaStack(); stack->setXXTEAKeyAndSign("2dxLua", strlen("2dxLua"), "XXTEA", strlen("XXTEA")); //这一步很关键，获取栈结构并调用setXXTEAKeyAndSign设置加密算法为xxtea，sign为XXTEA,KEY为2dxlua，很多游戏lua脚本都用的默认的sign和key //如果没有用默认的，ida打开libxxxluaxxx.so直接搜索applicationDidFinishLaunching导出函数也基本都能直接找到 //register custom function //LuaStack* stack = engine->getLuaStack(); //register_custom_function(stack->getLuaState());#if CC_64BITS FileUtils::getInstance()->addSearchPath("src/64bit");#endif FileUtils::getInstance()->addSearchPath("src"); //lua源码在src文件夹，资源在res文件夹 FileUtils::getInstance()->addSearchPath("res"); if (engine->executeScriptFile("main.lua")) //直接通过lua引擎调用main.lua进入lua的世界 { return false; } return true;} |
这句engine->executeScriptFile("main.lua")调用了cocos2d-x\cocos\scripting\lua-bindings\manual\CCLuaEngine.cpp的executeScriptFile调用了CCLuaStack.cpp的executeScriptFile
LuaStack::executeScriptFile
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | int LuaStack::executeScriptFile(const char* filename){ CCAssert(filename, "CCLuaStack::executeScriptFile() - invalid filename"); std::string buf(filename); // // remove .lua or .luac // size_t pos = buf.rfind(BYTECODE_FILE_EXT);//BYTECODE_FILE_EXT就是lua字节码，NOT_BYTECODE_FILE_EXT就是lua脚本源码 //static const std::string BYTECODE_FILE_EXT = ".luac"; if (pos != std::string::npos) { buf = buf.substr(0, pos);//截取前缀 } else { pos = buf.rfind(NOT_BYTECODE_FILE_EXT); if (pos == buf.length() - NOT_BYTECODE_FILE_EXT.length()) { buf = buf.substr(0, pos); } } FileUtils *utils = FileUtils::getInstance(); // // 1. check .luac suffix // 2. check .lua suffix // std::string tmpfilename = buf + BYTECODE_FILE_EXT; if (utils->isFileExist(tmpfilename)) { buf = tmpfilename; } else { tmpfilename = buf + NOT_BYTECODE_FILE_EXT; if (utils->isFileExist(tmpfilename)) { buf = tmpfilename; } } std::string fullPath = utils->fullPathForFilename(buf);//获取绝对路径 Data data = utils->getDataFromFile(fullPath);//通过getDataFromFile读取lua文件到data int rn = 0; if (!data.isNull()) { if (luaLoadBuffer(_state, (const char*)data.getBytes(), (int)data.getSize(), fullPath.c_str()) == 0)//通过luaLoadBuffer加载data { rn = executeFunction(0); } } return rn;} |
LuaStack::luaLoadBuffer
luaLoadBuffer里调用xxtea_decrypt解密了lua脚本，然后调用luaL_loadbuffer加载解密后的脚本，所以直接hook 这个函数luaL_loadbuffer把(char*)content这个字符dump出来就得到解密过的lua脚本了
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | int LuaStack::luaLoadBuffer(lua_State *L, const char *chunk, int chunkSize, const char *chunkName){ int r = 0; if (_xxteaEnabled && strncmp(chunk, _xxteaSign, _xxteaSignLen) == 0)//这里判断是否开启xxtea加密，如果开启就需要解密 { // decrypt XXTEA xxtea_long len = 0; unsigned char* result = xxtea_decrypt((unsigned char*)chunk + _xxteaSignLen, (xxtea_long)chunkSize - _xxteaSignLen, (unsigned char*)_xxteaKey, (xxtea_long)_xxteaKeyLen, &len);//调用xxtea_decrypt解密脚本，这个函数在cocos2d-x\external\xxtea\xxtea.cpp里，加解密都在这个cpp里 unsigned char* content = result; xxtea_long contentSize = len; skipBOM((const char*&)content, (int&)contentSize);//忽略utf8的bom r = luaL_loadbuffer(L, (char*)content, contentSize, chunkName);//无论是否加密，解密后都会调用luaL_loadbuffer函数，所以直接hook这个函数把(char*)content这个字符dump出来就是解密过的lua脚本了 free(result); } else { skipBOM(chunk, chunkSize); r = luaL_loadbuffer(L, chunk, chunkSize, chunkName);//这个返回值r会反映加载失败的类型，在下面的switch中打印出来 }#if defined(COCOS2D_DEBUG) && COCOS2D_DEBUG > 0 if (r) { switch (r) { case LUA_ERRSYNTAX: CCLOG("[LUA ERROR] load \"%s\", error: syntax error during pre-compilation.", chunkName); break; case LUA_ERRMEM: CCLOG("[LUA ERROR] load \"%s\", error: memory allocation error.", chunkName); break; case LUA_ERRFILE: CCLOG("[LUA ERROR] load \"%s\", error: cannot open/read file.", chunkName); break; default: CCLOG("[LUA ERROR] load \"%s\", error: unknown.", chunkName); } }#endif return r;} |
而luaL_loadbuffer的源码没有，只有编译过的库cocos2d-x\external\lua\luajit\prebuilt\android\armeabi-v7a\libluajit.a，
要找它的实现需要下载luajit源代码分析了，这就完全进入了lua虚拟机的实现
a Just-In-Time Compiler for Lua. 采用C语言写的Lua的解释器的代码
总结
1.从c++进入lua世界的调用逻辑
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 | AppDelegate::applicationDidFinishLaunching{ setXXTEAKeyAndSign executeScriptFile { getDataFromFile luaLoadBuffer { xxtea_decrypt luaL_loadbuffer { luajit } } executeFunction }} |
2.加密算法为xxtea，如果没有修改，sign为XXTEA,KEY为2dxlua，如果有修改，可以ida打开libxxluaxx.so在applicationDidFinishLaunching里找到
3.无论是否加密，解密后都会调用luaL_loadbuffer函数，所以直接hook这个函数把(char*)content这个字符dump出来就是解密过的lua脚本了，缺点是要把游戏运行一遍，只能搞出执行过的代码
4.cocos2d-x\external\xxtea\xxtea.cpp里有完整的加密解密算法，逻辑清晰，可以写个python脚本直接本地解密，也可以在这里hook获取key和sign或者解密后脚本
实战
某捕鱼游戏，下载安装apk后，再其内部内置了捕鱼、麻将等十几款小游戏，嘿嘿，懂得都懂这是干啥的，直接点击捕鱼游戏下载，
下载后的游戏源码在/data/data/com.q8wdw6.gyll9spfo.nycatp9/files/download/里
adb pull 出来，files文件夹里面已经暴露很多信息了，配置，下载的游戏，更新等等
进入files\download\107\res\就可以看到luac，很明显crash里面存储了所有碰撞，model_path_crash和path里存储的是移动路径，我们可以看到所有的鱼的移动路径都是tm设定好的，models里面存储着游戏逻辑，views里面存储着界面显示逻辑
随机打开一个luac加密了，开头的ZX_CS@56#D~d@dud明显就是加密sign
根据之前对cocos2d引擎的分析，找到apk下面带有lua也是最大的一个so libqpry_lua.so，用ida直接打开，定位到AppDelegate::applicationDidFinishLaunching函数，直接拖到最下面，看到这句
(*(v7 + 1) + 116))((v7 + 1), "ZX_01RdsF~@!R8", 14, "ZX_CS@56#D~d@dud", 16);很明显是调用了stack->setXXTEAKeyAndSign
对比源码stack->setXXTEAKeyAndSign("2dxLua", strlen("2dxLua"), "XXTEA", strlen("XXTEA"));
解密key为ZX_01RdsF~@!R8，sign为ZX_CS@56#D~d@dud
也可以直接搜索字符串，因为key和sign在一个函数调用，所以一般离的很近，base/src/main.lua这个字符串进一步验证了正确性
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | int __fastcall AppDelegate::applicationDidFinishLaunching(AppDelegate *this)``{`//`前面是一堆初始化啥的没用的`....`(**(v7 + 1) + 116))(*(v7 + 1), "ZX_01RdsF~@!R8", 14, "ZX_CS@56#D~d@dud", 16);` `if ( (*(*v7 + 28))(v7, "base/src/main.lua") )` `return 0;` `v26 = GetMCKernel();` `if ( !v26 )` `return 0;` `v27 = *(this + 145); if ( v27 ) v27 += 580; v28 = (*(*v26 + 20))(v26, v27);` `v29 = *(cocos2d::Director::getInstance(v28) + 152);` `v32[0] = AppDelegate::GlobalUpdate;` `v32[1] = -8;` `cocos2d::Scheduler::schedule(v29, AppDelegate::GlobalUpdate, -8, this + 4, 0.0, 0xFFFFFFFE, 0.0, 0);` `return v25;``}` |
有了key和sign就可以直接解密luac脚本了，照着写，很简单，可以看到sign的作用就是被忽略，只有长度有用，尴尬，解密用的主要是key
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | unsigned char* result = xxtea_decrypt((unsigned char*)chunk + _xxteaSignLen, (xxtea_long)chunkSize - _xxteaSignLen, (unsigned char*)_xxteaKey, (xxtea_long)_xxteaKeyLen, &len);unsigned char *xxtea_decrypt(unsigned char *data, xxtea_long data_len, unsigned char *key, xxtea_long key_len, xxtea_long *ret_length){ unsigned char *result; *ret_length = 0; if (key_len < 16) { unsigned char *key2 = fix_key_length(key, key_len); result = do_xxtea_decrypt(data, data_len, key2, ret_length); free(key2); } else { result = do_xxtea_decrypt(data, data_len, key, ret_length); } return result;} |
或者直接pip install xxtea-py
然后直接python，自己写个循环实现批量解密吧
1 2 3 4 5 6 7 8 9 10 11 12 13 | import xxteaimport os orig_path=“”//初始路径 new_path=“”//存储路径 xxtea_sign=“” xxtea_key=“” orig_file = open(orig_path, "rb") encrypt_bytes = orig_file.read() orig_file.close() decrypt_bytes = xxtea.decrypt(encrypt_bytes[len(xxtea_sign):], xxtea_key) new_file = open(new_path, "wb") new_file.write(decrypt_bytes) new_file.close() |
下面开始分析lua，这个最简单，我们想分析子弹打到鱼的逻辑，直接找src\views\layer\BulletLayer.luac
直接找子弹打到鱼的函数，很清晰，第一个参数为子弹对象，第二个为鱼列表，这里看到只有master_id == self_player_id才会调用
on_self_bullet_crash_fish当自己的子弹击中了鱼最后会调用加金币等，否则只调用on_bullet_crash_fish显示效果，这里可以也改成on_self_bullet_crash_fish就可以加金币了
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | function BulletLayer:on_bullet_crash_fish(bullet_obj, t_fish_list) local scene = self:get_scene() local master_id = bullet_obj:get_master_id() local bullet_uid = bullet_obj:get_bullet_uid() local self_player_id = self:get_self_player_id() local num = #t_fish_list if(num >= 2) then local fish_layer = self:get_fish_layer() table.sort(t_fish_list, function(uid1, uid2) local fish_obj1 = fish_layer:get_fish_by_uid(uid1);local fish_obj2 = fish_layer:get_fish_by_uid(uid2) local zorder1 = fish_obj1:getLocalZOrder();local zorder2 = fish_obj2:getLocalZOrder() if(zorder1 > zorder2) then return true end end) end local fish_uid = t_fish_list[1] if(master_id == self_player_id) then scene:on_self_bullet_crash_fish(master_id, bullet_uid, fish_uid) --scene:on_self_bullet_crash_fish_test(master_id, bullet_uid, fish_uid) end scene:on_bullet_crash_fish(master_id, bullet_uid, t_fish_list)end |
在定位一下加钱的函数，fish_gold是鱼的钱，fish_odds是鱼的剩余 ，这句 local one_add_gold = math.floor(fish_gold/12)就是一个鱼加的钱，我们把这个/12改为*12就可以修改倍数了
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | function AnimationLayer:play_catch_fish_earn_money_self(fish_gold, fish_odds) local earn_money_node = self:reuse_new_earn_money_view_node('zhuanqianle_buyu', self, 0) local pos = cc.p(sizeVisble.width/2, sizeVisble.height/2) local one_add_gold = math.floor(fish_gold/12) local min = self:get_earn_money_one_add_gold_min() if(one_add_gold < min) then one_add_gold = min end earn_money_node:setPosition(pos); earn_money_node:set_gain_gold(fish_gold) earn_money_node:set_one_add_gold(one_add_gold); earn_money_node:set_cur_gold(0) local delay_time = cc.DelayTime:create(4) local call_back = cc.CallFunc:create(handler(self, self.call_back_reuse_obj)) local seq = cc.Sequence:create(delay_time, call_back); earn_money_node:setScale(1) earn_money_node:runAction(seq); earn_money_node:play_ani()end |
入口代码在AnimationLayer.lua里，直接看接收到玩家捕到鱼的函数，分为网或者炸弹，里面还有一网打尽和大转盘之类的特效，这里可以把它全部改成高倍的特效
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | function AnimationLayer:on_recv_player_catch_fish(player_id, fish_uid, fish_gold) local fish_layer = self:get_fish_layer() local fish_obj = fish_layer:get_fish_by_uid(fish_uid) if(fish_obj == nil) then return end local data_center = self:get_data_center() local fish_id = fish_obj:get_fish_id() local fish_info = data_center:get_fish_info(fish_id) if(fish_info == nil) then return end local fish_type = fish_info.type if(fish_type == GameDefine.fish_type.wang) then local other_fish_obj_list = self:get_other_fish_yi_wang_da_jin_list(fish_obj, GameDefine.fish_type.wang) local num = #other_fish_obj_list if(num > 0) then local fish_odds = self:get_catch_fish_odds(fish_obj, other_fish_obj_list) self:on_player_catch_fish_yi_wang_da_jin(player_id, fish_obj, fish_gold, fish_odds, other_fish_obj_list) end self:on_player_catch_fish_drop_fish_gold(player_id, fish_obj, 0, 0) return end if(fish_type == GameDefine.fish_type.bomb) then play_drop_gold = 0 local other_fish_list = self:get_bomb_fish_effect_fish_list() local num = #other_fish_list if(num > 0) then local fish_odds = self:get_catch_fish_odds(fish_obj, other_fish_list) self:on_player_catch_fish_bomb(player_id, fish_obj, fish_gold, fish_odds, other_fish_list) end self:on_player_catch_fish_drop_fish_gold(player_id, fish_obj, 0, 0) return end local fish_odds = fish_info.mulriple_max;local fish_name = fish_info.name self:on_player_cath_fish_da_zhuan_pan(player_id, fish_type, fish_gold, fish_name) self:on_player_catch_fish_drop_fish_gold(player_id, fish_obj, fish_gold, fish_odds)end |
src\models\DataCenter.lua里存储着鱼和子弹等参数，可以看到子弹最高9级，odds_min与odds_max应该就代表威力，改这里可以改子弹威力
1 2 3 4 5 6 7 8 9 10 11 12 | { room_style= 3, cannon_id= 109, odds_min= 7, odds_max= 10, level= 3, res= "pao3_buyu", bullet= "zd9", net= "yuwang3_buyu", time= 200, sound= 109} |
self.fish_client存储不同鱼的参数，不同id对应不同鱼，mulriple_min与mulriple_max存储着金币的倍数最大与最小值，一般鱼都是2-3倍，大章鱼为300倍，改这里可以直接改鱼的倍数
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 | { id= 302, name= "60倍组合鱼", packet= "4lian_buyu", crash_model= 101, mulriple_min= 60, mulriple_max= 60, type= 101, zoder= 21, die_sound= "fish14_1", die_type= 4, copy_num= 4},{ id= 402, name= "大章鱼", packet= "yu22_buyu", crash_model= 16, mulriple_min= 300, mulriple_max= 300, type= 2, zoder= 30, bron_sound= "f_wb_3", die_sound= "fish33_1", die_type= 5, copy_num= 4}, |
其他的功能逻辑获得源码后都很清晰，改倍数改鱼改子弹什么都很简单，改完之后重新用sign和key加密之后push到相应文件夹下面就实现了破解
个人想法
如何实现cocos2d反逆向，我的一些不成熟想法，由浅到深分层如下
1.修改xxtea的key和sign，就像这个游戏，需要分析so才能找到key
2.直接修改xxtea算法为其他可逆算法，这样逆向的时候还得逆加密算法
3.在进一步，修改luajit源码改动lua虚拟机，比如改变字节码指令顺序，或者改变数据读取顺序等，这样逆向的时候必须分析lua虚拟机的改动
4.把key，加密算法，虚拟机改动等的关键函数封装放到其他cpp或者其他so里，在加密一层，调用的时候在解密，这样需要先动态调试先分析调用逻辑
5.关键代码加入ollvm再编译或者直接vm掉，这样需要先去掉ollvm混淆或者分析vm
参考文章
[培训]内核驱动高级班，冲击BAT一流互联网大厂工作，每周日13:00-18:00直播授课
|
|
|---|---|
|
|
|
|
|
|
|
|
太强了
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
你直接用tea-py库算出来不对吗 |
|
|
|
|
|
算出来不对，然后我仔细看了so文件里面的逻辑，发现有原理是差不多，但是运算公式不对~正在学习如何hook这个函数，用的frida框架，却总是报错 |
|
|
你直接把tea-py的源码复制出来，然后对着ida找算法变化的地方改，py库里的解析肯定是对的 |
|
|
我确实是这样做的，最好结果仍然不正确~~所以我正在学习用frida框架去hook下输入输出~可是，可是~~~我全都照着论坛上其他大佬的做的，然而一运行就返回message的默认值~~目前正在debug找原因，您有没有什么好的建议？ |
|
|
这。。。不如去找肉丝大佬搞个虚拟机环境 |
|
|
肉丝大佬是？？我虚拟环境应该是配置好了~~但是又遇到新的问题了~逆向路不好走阿 |
|
|
ios区版主 最近出了一本书讲frida的 |
|
|
可以来一期入门视频教程么
|
|
|
学习了~
|
|
|
|
|
|
|
|
|
|
