• [原创]某内测中拳头公司的fps手游GName算法逆向

0x0 序言

前段时间研究了一下某游戏的GName算法，水一篇文章记录一下，以下简称该游戏为C手游。

0x1 静态分析

首先先dump并修复libUE4.so，拖进IDA看一下。ida解析完成后，搜ByteProperty，找到引用的函数
正常来说找函数调用，这个函数的参数就是全局变量FNamePool的指针，也就是GName，但是C手游的查引用后发现，只有一个函数sub_562B820调用过这个sub_5627A0C

其中这个v1就是本该是一个GName的值，再对sub_562B820查一次调用，随便进去一个函数，发现sub_562B820这个函数的返回值貌似返回的就是fnamePool的地址

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//sub_562B20的返回算法
return *(_QWORD *)(byte_9B0A620[(unsigned int)off_9B0A6A0] | (unsigned __int64)(unsigned __int16)(byte_9B0A620[dword_9B0A6A4] << 8) | ((unsigned __int64)byte_9B0A620[dword_9B0A6A8] << 16) & 0xFFFF000000FFFFFFLL | (byte_9B0A620[(unsigned int)off_9B0A6AC] << 24) | ((unsigned __int64)byte_9B0A620[dword_9B0A6B0] << 32) & 0xFFFF00FFFFFFFFFFLL | ((unsigned __int64)byte_9B0A620[dword_9B0A6B4] << 40) | ((unsigned __int64)byte_9B0A620[dword_9B0A6B8] << 48) | ((unsigned __int64)byte_9B0A620[(unsigned int)off_9B0A6BC] << 56));


猜测他是通过byte_9B0A620这个数组，以一定的算法去动态生成FNamePool的地址，不像其他UE4游戏，内存中没有指向他的全局变量。

0x2 动态分析

那既然静态分析完了，那就实际来验证一下这个想法对不对吧。
首先先搜一下ByteProperty

找到FNamePool，然后搜索一下0x7325610000引用，果然没有全局变量指向这个地址。对这个地址下个断点，查一下调用栈

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[13432|13587] event_addr:0x7325610000 hit_count:320, Backtrace:  #00 pc 000000000562aeb4  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #01 pc 000000000562cf34  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #02 pc 00000000059db020  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #03 pc 0000000003dac2dc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #04 pc 00000000059e29c0  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #05 pc 0000000006cb6fe0  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #06 pc 00000000058dc80c  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #07 pc 00000000057b92dc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #08 pc 00000000057b9410  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #09 pc 0000000005876ecc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #10 pc 00000000057ae080  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #11 pc 00000000058de858  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #12 pc 00000000058de1ac  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #13 pc 00000000058dde28  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #14 pc 00000000058dc814  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #15 pc 00000000057b92dc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #16 pc 00000000057b9410  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #17 pc 0000000005876ecc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #18 pc 00000000058681b0  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #19 pc 00000000057ae080  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #20 pc 00000000058de858  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #21 pc 00000000058de1ac  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #22 pc 00000000058dde28  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #23 pc 00000000058dc814  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #24 pc 00000000057b92dc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #25 pc 00000000057b9410  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #26 pc 0000000005876ecc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #27 pc 00000000057ae080  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #28 pc 00000000058de858  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #29 pc 00000000058de1ac  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #30 pc 00000000058dde28  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #31 pc 00000000058dc814  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #32 pc 00000000057b92dc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #33 pc 00000000057b9410  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #34 pc 0000000005876ecc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #35 pc 00000000058681b0  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #36 pc 00000000057ae080  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #37 pc 00000000058de858  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #38 pc 00000000058de1ac  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #39 pc 00000000058dde28  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #40 pc 00000000058dc814  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #41 pc 00000000057b92dc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #42 pc 00000000057b9410  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #43 pc 0000000005876ecc  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #44 pc 00000000057ae080  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #45 pc 00000000058de858  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #46 pc 00000000058de1ac  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #47 pc 00000000058dde28  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so
  #48 pc 00000000058dc814  /data/app/~~xxx_xxxxxxxxxxx==/com.xxxxxxx.xxxx.xxxxx-xxxxxxxxxxxxxxx==/lib/arm64/libUE4.so

进562cf34这个地方看一下

果然跟之前猜测的差不多，写个frida脚本试试能不能生成类名

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function getName(index){
    var f_addr = moduleBase.add(0x562b820);
      // 将目标函数地址转换为JavaScript函数
    var getGnameFunc = new NativeFunction(f_addr, 'uint64', []);
       
    // 调用目标函数并传递内存地址作为参数
    try{
        var gname = getGnameFunc();
        console.log(`GName: ${gname}`);
        // dumpVector(buf);
        //info(ptr(actor_addr).add(0x130).readPointer().add(0x14c).readU8()&32 != 0);
    }
    catch (e){
        console.log(e)
    }
    var offset_FNameEntry_Info = 0;
  
    var Block = index >> 16;
    var Offset = index & 65535;
  
    var FNamePool =  gname;
    // console.log(`FNamePool: ${FNamePool}`);
    console.log(`Block: ${Block}`);
    var NamePoolChunk = ptr(FNamePool).add(0x40).add (Block*8).readPointer();
    console.log(`NamePoolChunk: ${NamePoolChunk}`);
    var FNameEntry = NamePoolChunk.add((0x2 * index)&0x1FFFE);
    console.log(`FNameEntry: ${FNameEntry}`);
    try {
      if (offset_FNameEntry_Info !== 0) {
        var FNameEntryHeader = FNameEntry.readU16();
      } else {
        var FNameEntryHeader = FNameEntry.readU16();
      }
    } catch (e) {
      // console.log(e);
      return "";
    }
    console.log(`FNameEntryHeader: ${FNameEntryHeader}`);
    var str_addr = FNameEntry.add(0x2);
    console.log(`str_addr: ${str_addr}`);
    var str_length = FNameEntryHeader >> 6;
    var wide = FNameEntryHeader & 1;
    console.log(str_length)
    if (str_length > 0 && str_length < 250) {
  
      var str = str_addr.readUtf8String(str_length);
      console.log(str)
    }
       
}

在登陆界面获取看看world的类名

也是验证成功了。

0x3 小结

这次最开始还是花了点时间，看懂了之后就感觉这个方法还挺简单的，也算是见识了一种修改GName的方式。

最新回复：
KXXTEST 2024-10-10 14:31:30
mark
AunCss 2024-10-10 15:42:59
瓦的手游？大佬用什么在内存下断点的，怎么调用栈能这么深
墨穹呢 2024-10-10 15:58:47
感谢分享