第一次遇到u3d，寄！

用ilcppdumper dump出dll文件

選擇運行Il2CppDumper.exe并依次選擇il2cpp.so的可執行文件和global-metadata.dat文件

dump出的dll文件在DummyDll里面。

?dnspy查看AssemblyCSharp.dll，定位到關鍵函數GameManager.NoteHit

然后用ida打開lib2cpp.so文件 運行我們ilcppdumper里面的ida_py3腳本。然后再點擊script.json

然后ida會恢復函數，本來想跑完分析，但是跑很久，我們就直接分析吧，很卡。

查看GameManagerNoteHit

通過交叉引用，通過判斷得知第?個參數是perfect判定,通過交叉引?得知第三個參數是當前?樂的時間

?最后的update函數在mug文件里面。

?

?我們分析一下libmug.so文件。

Server::run函數通過傳遞來的打擊時間參數來解密flag，下面就是run函數加密代碼。

?使用assetstudio分析打擊時間參數，把解壓后的apk直接放入。

?把run函數數據替換解密flag。

#include <stdio.h> #include <random> #include <Windows.h>using namespace std;const DWORD hitp[] = { 0,0,0,146,292,292,439,512,585,585,658,731,804,878,1024,1170,1170,1317,1463,1463,1609,1682,1756,1756,1902,2048,2195,2341,2341,2487,2634,2634,2780,2853,2926,2926,3073,3146,3219,3219,3365,3439,3512,3512,3658,3804,3878,3951,4024,4097,4097,4243,4390,4682,4682,4682,4829,4975,4975,5121,5195,5268,5341,5414,5487,5560,5560,5853,5853,5999,6146,6146,6292,6365,6439,6439,6585,6731,6731,6731,7024,7024,7170,7317,7317,7463,7536,7609,7609,7682,7756,7829,7902,7902,7975,8048,8121,8195,8341,8487,8634,8780,9073,9073,9073,9219,9365,9365,9512,9658,9658,9804,9878,9951,9951,10097,10243,10243,10243,10390,10463,10536,10536,10682,10829,10829,10975,11121,11121,11268,11414,11414,11560,11707,11707,11853,11999,11999,11999,12146,12292,12292,12439,12439,12585,12585,12585,12731,12878,12951,13024,13097,13170,13170,13317,13463,13463,13463,13609,13756,13756,13756,13902,14048,14048,14195,14341,14487,14634,14634,14926,14926,14926,15219,15219,15219,15365,15365,15512,15512,15658,15804,15804,15951,16024,16097,16097,16170,16243,16317,16390,16390,16536,16682,16682,16829,16902,16975,16975,17121,17268,17268,17268,17414,17560,17634,17707,17780,17853,17926,17999,18073,18146,18146,18292,18439,18439,18731,18731,18731,18878,19024,19024,19024,19170,19243,19317,19463,19609,19609,19609,19756,19829,19902,20048,20195,20195,20341,20487,20487,20634,20780,20780,20926,21073,21073,21219,21365,21365,21365,21512,21585,21658,21658,21804,21951,21951,21951,22097,22243,22317,22390,22463,22536,22536,22609,22682,22756,22829,22829,22975,23121,23121,23268,23414,23560,23707,23780,23853,23926,23999,23999,24073,24146,24219,24292,24365,24439,24512,24585,24585,24731,24731,24878,24878,24878,25024,25170,25170,25317,25390,25463,25463,25609,25756,25756,25756,25902,25902,26048,26048,26195,26195,26341,26341,26414,26487,26487,26560,26634,26634,26780,26780,26926,27219,27512,27585,27658,27731,27804,27804,28097,28097,28390,28682,28682,28975,29268,29268,29560,29560,29853,29853,30146,30439,30439,30731,31024,31024,31317,31609,31609,31902,32195,32195,32487,32780,32780,32780,33365,33365,33365,33951,33951,34243,34536,34536,34829,35121,35121,35414,35707,35707,35707,35999,36292,36585,36878,36878,37024,37024,37170,37170,37463,37463,37463,37609,37756,37756,37902,38048,38048,38195,38341,38341,38487,38634,38634,38780,38926,39073,39219,39365,39512,39658,39804,39804,39951,40097,40097,40243,40390,40390,40536,40682,40829,40975,40975,41121,41268,41414,41560,41707,41853,41999,42146,42146,42292,42292,42439,42585,42731,42731,42878,42878,43024,43170,43317,43317,43463,43463,43609,43609,43682,43756,43756,43829,43902,43902,44048,44048,44195,44195,44341,44341,44487,44560,44634,44707,44780,44853,44926,44999,45073,45146,45219,45292,45365,45439,45512,45585,45658,45658,45804,45951,45951,46097,46243,46243,46536,46536,46536,46829,46829,46902,46975,47121,47121,47268,47414,47414,47560,47634,47707,47707,47853,47926,47999,47999,48146,48292,48292,48439,48585,48585,48731,48878,48878,49024,49170,49170,49243,49317,49463,49463,49609,49756,49756,49902,49975,50048,50048,50121,50195,50268,50341,50341,50487,50487,50707,50707,50926,50926,51073,51219,51365,51512,51512,51585,51658,51804,51804,51951,52097,52097,52170,52243,52317,52390,52390,52536,52609,52682,52682,52829,52975,52975,53121,53268,53268,53414,53560,53560,53707,53853,53853,53926,53999,54073,54146,54146,54219,54292,54365,54439,54439,54512,54585,54658,54731,54731,54878,54878,55024,55024,55024,55317,55317,55317,55609,55609,55609,55902,55902,55902,56195,56268,56341,56487,56487,56634,56780,56780,56926,56999,57073,57073,57219,57292,57365,57365,57512,57658,57658,57804,57951,57951,58097,58243,58243,58390,58536,58536,58609,58682,58829,58829,58975,59121,59121,59268,59341,59414,59414,59560,59634,59707,59707,59853,59926,59999,59999,60073,60292,60292,60439,60585,60585,60731,60878,60878,60951,61024,61024,61170,61170,61317,61317,61463,61463,61463,61536,61609,61609,61756,61756,61902,61902,62048,62048,62048,62121,62195,62195,62341,62341,62414,62487,62560,62634,62634,62780,62780,62926,62926,63073,63073,63219,63219,63292,63365,63439,63512,63512,63585,63658,63731,63804,63804,63878,63951,64024,64097,64097,64170,64243,64317,64390,64390,64536,64536,64609,64682,64829,64975,65121,65268,65414,65560,65560,65707,65853,65999,66146,66146,66439,66585,66878,67170,67317,67317,67609,67902,68048,68195,68341,68487,68487,68780,68926,69073,69219,69365,69512,69658,69658,69804,69951,70243,70390,70536,70682,70829,70829,71121,71268,71560,71853,71999,71999,72292,72585,72731,72878,73024,73170,73317,73463,73609,73609,73756,73975,74195,74341,74341,74634,74707,74780,74926,74926,75073,75073,75219,75219,75219,75365,75512,75512,75658,75658,75804,75804,75804,75951,76097,76097,76390,76390,76390,76536,76682,76682,76829,76829,76975,76975,76975,77268,77268,77414,77560,77560,77561,77707,77853,77853,77999,77999,78146,78146,78146,78292,78439,78439,78731,78732,78732,78878,79024,79024,79170,79171,79317,79317,79463,79609,79609,79756,79902,79902,80048,80195,80341,80341,80487,80487,80634,80780,80780,80926,80926,81073,81073,81073,81219,81365,81512,81512,81658,81658,81658,81951,81951,81951,82097,82243,82243,82390,82536,82682,82682,82829,82829,82829,82975,83121,83121,83268,83414,83414,83560,83707,83853,83853,83999,83999,83999,84292,84292,84365,84439,84512,84585,84585,84731,84804,84878,84878,84951,85024,85097,85170,85170,85317,85390,85463,85463,85536,85609,85682,85756,85756,85829,85902,85975,86048,86048,86121,86195,86268,86341,86341,86487,86634,86634,86707,86780,86853,86926,86926,87073,87146,87219,87219,87292,87365,87439,87512,87512,87658,87804,87804,87878,87951,88024,88097,88097,88170,88243,88317,88390,88390,88536,88609,88682,88682,88829,88975,88975,89121,89121,89268,89268,89414,89414,89560,89560,89707,89707,89853,89853,89999,89999,90146,90146,90292,90292,90439,90439,90585,90585,90731,90731,90878,90878,91024,91024,91170,91170,91317,91317,91390,91463,91536,91609,91682,91756,91829,91902,91975,92048,92121,92195,92268,92341,92634,92780,92926,93219,93365,93365,93365,93365,93658,93658,93804,93878,93951,93951,94097,94243,94317,94390,94463,94536,94536,94682,94829,94829,94975,95121,95121,95268,95414,95487,95560,95634,95707,95707,95853,95853,95999,95999,96146,96292,96292,96292,96439,96585,96585,96658,96731,96804,96878,96878,97024,97170,97170,97317,97390,97463,97463,97609,97756,97756,97829,97902,98048,98048,98048,98195,98341,98341,98487,98560,98634,98634,98780,98926,98926,99073,99219,99219,99365,99512,99512,99658,99804,99804,99951,100097,100170,100243,100317,100390,100390,100536,100682,100682,100829,100975,100975,100975,101121,101268,101268,101341,101414,101487,101560,101560,101707,101853,101853,101926,101999,102073,102146,102146,102292,102439,102439,102439,102585,102658,102731,102731,102878,103024,103024,103024,103170,103243,103317,103317,103317,103463,103609,103682,103756,103829,103902,103902,104048,104195,104195,104341,104487,104487,104487,104634,104780,104853,104926,104999,105073,105073,105219,105365,105365,105512,105658,105658,105658,105804,105951,105951,106097,106170,106243,106243,106317,106390,106536,106536,106682,106756,106829,106829,106829,106975,107121,107121,107268,107268,107414,107414,107414,107560,107707,107707,107707,107853,107999,107999,107999,108146,108292,108292,108439,108585,108585,108731,108878,108878,108878,109024,109170,109170,109317,109463,109463,109536,109609,109682,109756,109756,109902,110048,110048,110048,110195,110195,110341,110341,110341,110487,110487,110634,110634,110634,110780,110780,110926,110926,110926,111073,111073,111219,111219,111219,111365,111512,111658,111731,111804,111878,111951,112024,112097,112097,112097,112390,112390,112536,112682,112682,112682,112829,112975,112975,113121,113268,113268,113414,113560,113560,113707,113853,113853,113999,114146,114219,114292,114365,114439,114439,114585,114731,114731,114878,115024,115024,115024,115170,115317,115317,115463,115536,115609,115609,115756,115902,115902,115975,116048,116121,116195,116195,116268,116341,116414,116487,116487,116560,116634,116707,116780,116780,116926,117073,117073,117219,117365,117365,117512,117658,117658,117804,117878,117951,117951,118097,118243,118243,118390,118536,118536,118682,118829,118902,118975,119048,119121,119121,119268,119414,119414,119560,119707,119707,119853,119999,119999,120146,120292,120292,120439,120439,120731,121024,121170,121463,121536,121609,121682,121756,121756,121756,121902,122048,122048,122048,122195,122341,122341,122341,122487,122560,122634,122634,122634,122780,122926,122926,122926,123073,123219,123219,123219,123365,123512,123512,123512,123585,123658,123731,123804,123804,123804,123951,124097,124097,124097,124243,124390,124390,124390,124536,124682,124682,124682,124829,124975,124975,124975,125121,125268,125268,125268,125414,125487,125560,125560,125560,125707,125853,125853,125853,125999,126146,126146,126146,126292,126439,126439,126439,126585,126585,126731,126731,126878,126878,127024,127024,127024,127170,127170,127317,127317,127463,127463,127609,127609,127609,127756,127756,127902,127902,128048,128048,128195,128195,128268,128341,128341,128414,128487,128487,128560,128634,128707,128780,128780,128853,128926,128999,129073,129146,129219,129292,129365,129365,129439,129512,129585,129658,129731,129804,129878,129951,129951,130024,130097,130170,130243,130243,130317,130390,130463,130536,130536,130682,130756,130829,130829,130829,130975,130975,131121,131195,131268,131341,131560,131707,131707,131780,131853,131926,132146,132292,132365,132439,132512,132731,132878,132878,132951,133024,133097,133463,133463,133756,134048,134048,134048,134341,134634,134634,134926,134926,135219,135219,135219,135512,135512,135658,135658,135804,135804,135951,135951,136097,136097,136243,136243,136390,136390,136536,136536,136609,136682,136682,136829,136829,136902,136975,136975,137121,137121,137268,137268,137414,137414,137560,137560,137707,137707,137780,137853,137926,137999,137999,138073,138146,138146,138219,138292,138365,138439,138439,138512,138585,138658,138731,138731,138804,138878,138951,139024,139024,139097,139170,139243,139317,139317,139463,139463,139609,139609,139756,139756,139902,139902,140195,140195,140195,140195 };DWORD __ROR4__(DWORD a1, char a2) {return (a1 >> a2) | (a1 << (32 - a2)); }int rounds(uint8_t* bytes, unsigned int a2, int a3) {DWORD* v3; // r4DWORD v4; // r12DWORD v5[2]; // r5DWORD v6; // r3DWORD result; // r0v3 = (DWORD*)((char*)bytes + a3);v4 = *(DWORD*)((char*)bytes + a3);*(DWORD64*)&v5[0] = *(DWORD64*)((char*)bytes + a3 + 4);v6 = *(DWORD*)((char*)bytes + a3 + 12);*(DWORD*)((char*)bytes + a3) = *(&v5[0] + 1);result = v4 ^ __ROR4__(*(&v5[0] + 1) ^ a2, 19);v3[3] = v5[0] ^ __ROR4__(v6, 18) ^ __ROR4__(*(&v5[0] + 1) ^ a2, 19);v3[1] = v6;v3[2] = result;return result; }int main(int argc, char const* argv[]) {unsigned char enc_bytes[] ={0x3C, 0xAC, 0x92, 0x6F, 0x44, 0xA1, 0xC1, 0x17, 0xFD, 0x62,0x60, 0xDD, 0x63, 0xF8, 0xE3, 0x2A, 0x5E, 0x75, 0x78, 0xBE,0x59, 0x46, 0x33, 0xF6, 0x2E, 0x64, 0x61, 0x8A, 0x27, 0x93,0x21, 0x7D, 0x00};mt19937 rng(-196167794);for (int i = 0; i < 1608; ++i){if (rng() % 7 >= 3){rounds(enc_bytes, rng(), hitp[i] & 0xF);}}printf("%s\n", enc_bytes);getchar();return 0; }

補充frida-hook做法：

frida -U com.DefaultCompany.com.unity.template.mobile2D -l so.js --no-pause

?js 腳本：

const hitdata = ``; // beatmaps/chromevox/hitpoints const timeList = hitdata.split("\n").map((v, idx, arr) => {return parseInt(v.split(",")[1], 10); }); function awaitHook(){var ptr = Module.findBaseAddress("libd3mug.so");console.log(ptr);const update = new NativeFunction(ptr.add(0x0000780), "pointer", ["char"]);const instance = ptr.add(0x02D18);// runninginstance.writePointer(new NativePointer(0)); // init.for (const t of timeList) {update(t);}console.log(instance.readPointer().readCString()); } setImmediate(function(){setTimeout(awaitHook,10); })

但是需要在真機運行，我的虛擬機運行會報錯，虛擬機無法調試so文件，攢錢買個pixel。

總結

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