某手游完整性校验分析

前言

只是普通的单机手游，广告比较多，所以分析处理了下，校验流程蛮有意思的，所以就分享出来了

1.重打包崩溃处理

样本进行了加固，对其dump出dex后重打包出现崩溃

ida分析地址发现为jni函数引起

利用Xposed直接替换该函数，崩溃问题解决

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XposedHelpers.findAndHookMethod("com.unity3d.player.UnityPlayerActivity", classLoader, "IsHDR_DisplayBoot", java.lang.String.class, java.lang.String.class, new XC_MethodReplacement() {     @Override     protected Object replaceHookedMethod(MethodHookParam methodHookParam) throws Throwable {         return null;     } });

2.卡加载界面处理

但是出现了新的问题，游戏卡在了加载页面

对该类的其他jni函数进行分析，发现supportVulkan很明显进行了签名读取，对其去除签名校验。

此处参考项目：ApkSignatureKillerEx

3.地图无法进入问题分析（基于原包）

去除完签名校验后，游戏能正常进入主页面，但是点击游戏地图没有任何反应。

在对原包进行多次测试发现，在首次启动游戏时，如果断网也会出现无法正常进入地图的问题，怀疑是游戏首次启动进行了网络请求进行数据校验

经过抓包对比定位到可疑数据包

利用Frida的算法通杀脚本没有定位到相关内容，怀疑是so层进行了请求

3.1 hook send函数进行调用栈分析

通过调用栈可以很清晰看到请求是从unity引擎相关的so中发出的。

3.2 il2cppTrace对请求调用栈分析

查阅资料，在unity中，网络请求主要通过UnityWebRequest 类来执行网络请求，利用frida-il2cpp-bridge对UnityWebRequest进行trace，打印调用栈得

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0x0247db9c ┌─UnityEngine.Networking.UnityWebRequest::.ctor(this = UnityEngine.Networking.UnityWebRequest, url = "http://106.54.194.167:8077/CheckUpdate", method = "POST") 0x0247db00 │ ┌─UnityEngine.Networking.UnityWebRequest::set_url(this = UnityEngine.Networking.UnityWebRequest, value = "http://106.54.194.167:8077/CheckUpdate") 0x0247ef38 │ │ ┌─UnityEngine.Networking.UnityWebRequest::InternalSetUrl(this = UnityEngine.Networking.UnityWebRequest, url = "http://106.54.194.167:8077/CheckUpdate") 0x0247ef38 │ │ └─UnityEngine.Networking.UnityWebRequest::InternalSetUrl 0x0247db00 │ └─UnityEngine.Networking.UnityWebRequest::set_url 0x0247dc1c │ ┌─UnityEngine.Networking.UnityWebRequest::set_method(this = UnityEngine.Networking.UnityWebRequest, value = "POST") 0x0247e4e0 │ │ ┌─UnityEngine.Networking.UnityWebRequest::InternalSetMethod(this = UnityEngine.Networking.UnityWebRequest, methodType = Post) 0x0247e4e0 │ │ └─UnityEngine.Networking.UnityWebRequest::InternalSetMethod 0x0247dc1c │ └─UnityEngine.Networking.UnityWebRequest::set_method 0x0247db9c └─UnityEngine.Networking.UnityWebRequest::.ctor

在IDA中进行交叉引用分析定位到UnitySDKManager类

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追踪调用定位到 class UnitySDK.UnitySDKManager.d__25 : System.Object, System.Collections.Generic.IEnumeratorObject>, System.Collections.IEnumerator, System.IDisposable     private Boolean MoveNext() { }

增加UnitySDKManager类重新对其trace（因为出现报错，把参数输出关了）

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0x00b15b44 ┌─UnitySDK.UnitySDKManager::ServerVerifyApk 0x00b04b3c │ ┌─UnitySDK.UnitySDKManager::GetFileInfoList 0x00b04b3c │ └─UnitySDK.UnitySDKManager::GetFileInfoList 0x00b06ec0 │ ┌─UnitySDK.UnitySDKManager::GetGamePackageName 0x00b06ec0 │ └─UnitySDK.UnitySDKManager::GetGamePackageName 0x00b06204 │ ┌─UnitySDK.UnitySDKManager::GetSDKVersion 0x00b06204 │ └─UnitySDK.UnitySDKManager::GetSDKVersion 0x00b06278 │ ┌─UnitySDK.UnitySDKManager::HexStringToHex 0x00b06278 │ └─UnitySDK.UnitySDKManager::HexStringToHex 0x00b10fcc │ ┌─UnitySDK.UnitySDKManager::EncryptString 0x00b10fcc │ └─UnitySDK.UnitySDKManager::EncryptString 0x00b100a4 │ ┌─UnitySDK.UnitySDKManager::PostData 0x00a341fc │ │ ┌─UnitySDK.UnitySDKManager.d__25::.ctor 0x00a341fc │ │ └─UnitySDK.UnitySDKManager.d__25::.ctor 0x00b100a4 │ └─UnitySDK.UnitySDKManager::PostData 0x00a3422c │ ┌─UnitySDK.UnitySDKManager.d__25::MoveNext 0x00b12be4 │ │ ┌─UnitySDK.UnitySDKManager::GetUrl 0x00b12be4 │ │ └─UnitySDK.UnitySDKManager::GetUrl 0x0247db9c │ │ ┌─UnityEngine.Networking.UnityWebRequest::.ctor 0x0247db00 │ │ │ ┌─UnityEngine.Networking.UnityWebRequest::set_url 0x0247ef38 │ │ │ │ ┌─UnityEngine.Networking.UnityWebRequest::InternalSetUrl 0x0247ef38 │ │ │ │ └─UnityEngine.Networking.UnityWebRequest::InternalSetUrl 0x0247db00 │ │ │ └─UnityEngine.Networking.UnityWebRequest::set_url 0x0247dc1c │ │ │ ┌─UnityEngine.Networking.UnityWebRequest::set_method 0x0247e4e0 │ │ │ │ ┌─UnityEngine.Networking.UnityWebRequest::InternalSetMethod 0x0247e4e0 │ │ │ │ └─UnityEngine.Networking.UnityWebRequest::InternalSetMethod 0x0247dc1c │ │ │ └─UnityEngine.Networking.UnityWebRequest::set_method 0x0247db9c │ │ └─UnityEngine.Networking.UnityWebRequest::.ctor 0x0247e0f4 │ │ ┌─UnityEngine.Networking.UnityWebRequest::set_uploadHandler 0x0247e0f4 │ │ └─UnityEngine.Networking.UnityWebRequest::set_uploadHandler 0x0247dfdc │ │ ┌─UnityEngine.Networking.UnityWebRequest::set_downloadHandler 0x0247dfdc │ │ └─UnityEngine.Networking.UnityWebRequest::set_downloadHandler 0x0247f66c │ │ ┌─UnityEngine.Networking.UnityWebRequest::SetRequestHeader 0x0247f66c │ │ └─UnityEngine.Networking.UnityWebRequest::SetRequestHeader 0x0247e42c │ │ ┌─UnityEngine.Networking.UnityWebRequest::Send 0x0247e430 │ │ │ ┌─UnityEngine.Networking.UnityWebRequest::SendWebRequest 0x0247e42c │ │ │ └─UnityEngine.Networking.UnityWebRequest::Send 0x0247e430 │ │ └─UnityEngine.Networking.UnityWebRequest::SendWebRequest 0x00a3422c │ └─UnitySDK.UnitySDKManager.d__25::MoveNext 0x00a34cd4 │ ┌─UnitySDK.UnitySDKManager.d__25::System.Collections.IEnumerator.get_Current 0x00a34cd4 │ └─UnitySDK.UnitySDKManager.d__25::System.Collections.IEnumerator.get_Current 0x00b15b44 └─UnitySDK.UnitySDKManager::ServerVerifyApk

通过调用栈可以初步对校验流程进行了解，主要通过ServerVerifyApk函数进行校验，经过一系列字符串加解密，最后进行网络请求

3.3 加解密函数hook分析

对关键函数进行hook分析

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0x00b10fcc │ UnitySDK.UnitySDKManager::EncryptString 0x00b0b13c │ UnitySDK.UnitySDKManager::DecryptString il2cpp: EncryptString:"{"appid":"com.meta.peopleground.dream","appName":"com.meta.peopleground.dream","appVer":"1.0.1","sdkVer":"2","appFileList":"981lDpbOb+vjRn/3yI74fI+1S5cr08qKLGq0xg7TcfFOA7hRePAQjXPCgIzEC+p58RThRtl4PIsPEgiJZVYn1e2oZl06jeKGD6+C0Zy6lQaDiAVaOtO5szilZxfmN2j8XtlBmBaOzOVBBi6ctJamGsfM2XbkGqYtf/TlNyvOZ8p5YDdOgnhG+WonkjG1sGEbuqc4sm+hkCxOC7dX1rEM4/5S6wT1erPL5+iWJoRpiTuHok15zCQjdNFCXn97Vwg+/h8eXrtxrDvkkLqqCff2D0WrAISmIOi4fY97ulhpz5Pey2vJlkLK5MdSApENx4exv3t4Q1sVfoPojwDueXAW9T1RTOc1LeK0cYMrBjsE1W8="}" il2cpp: EncryptString result:"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" il2cpp: DecryptString:"+CVWCEji2Lgf4nUTWb7J/Q==" il2cpp: DecryptString result:"100"

发现之前抓包获得的请求体相对应，其中，appFileList还是密文，继续分析

3.4 追EncryptString函数

与dump.cs中的函数进行对照发现v14 由字符串转hex转base64获得

1	System.Byte[] HexStringToHex(System.String inputHex); // 0x00b06278

hook HexStringToHex 函数获得参数

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il2cpp: inputHex:"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"

IDA继续查找调用发现其中字符串由GetFileInfoList函数获得

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// static System.IntPtr GetFileInfoList(); // 0x00b04b3c __int64 sub_B04B3C() {   __int64 (*v0)(void); // x8   __int64 v2[5]; // [xsp+0h] [xbp-40h] BYREF   int v3; // [xsp+28h] [xbp-18h]   char v4; // [xsp+2Ch] [xbp-14h]   v0 = (__int64 (*)(void))qword_30365A0;   if ( !qword_30365A0 )   {     v3 = 0;     v2[0] = (__int64)"UnitySDK";     v2[1] = 8LL;     v2[2] = (__int64)"GetFileInfoList";     v2[3] = 15LL;     v2[4] = 0x200000000LL;     v4 = 0;     v0 = (__int64 (*)(void))sub_812FB4(v2);     qword_30365A0 = (__int64)v0;   }   return v0(); }

很明显，调用了libUnitySDK.so中的GetFileInfoList函数获得

3.5 libUnitySDK.so分析

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__int64 GetFileInfoList() {   return FileInfoListStr; }

FileInfoListStr在writeFileJson函数中被赋值，而writeFileJson则是由java函数上文中的IsHDR_DisplayBoot调用（该函数首个参数为base.apk路径）

很明显，ll11l1l1ll函数 对之前的明文字符串进行了加密，frida hook打印参数

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args: {         "HashList" :         {                 "AndroidManifest.xml" : " c72b1d2",                 "assets/bin/Data/Managed/Metadata/game.dat" : "a34a757d",                 "classes.dex" : "58b6cf21",                 "lib/arm64-v8a/libUnitySDK.so" : "b56d5af4",                 "lib/armeabi-v7a/libUnitySDK.so" : "3d548ba2"         },         "fileCount" : 1620 } returnResult: 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

其中 HashList 中文件对应的值为文件的 crc
至此，除了具体的字符串加密算法，游戏的校验流程已经很清晰

4.校验流程归纳

• 签名校验
• 读取base.apk进行关键文件crc读取
• 进行服务器请求，对关键文件crc校验

5.后记

对该校验去除的思路：

• 对读取安装包的函数 zip_open 或java层的 IsHDR_DisplayBoot 函数进行hook，进行参数替换，进行io重定向
• 基于il2cpp中的ServerVerifyApk函数进行更详细的分析，直接对其检测去除