MR2021 reverse MR_register wp

Posted by marginal on 2021-07-20
Estimated Reading Time 5 Minutes
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MR_register

这是一个双进程调试，建立一个被调试进程，调试器会对被调试者做出一定处理

根据sscanf找到关键函数。CreatProccessA函数中第6哥参数是进程标志，这里是1 | 2 == 3,建立调试进程及其线程但是只调试进程（具体可以查官方文档）

进入sub_40188D函数可以看到是一个调试事件循环

建立调试进程后调试时间第一个就是CREATE_PROCESS_DEBUG_EVENT，其值为3

sub_402CE5就是OpenProcess函数，

被调试者会进入sub_4026EA函数，

动调一下，（不能直接附加），从头开始动调，在除法处会发生异常，buffer[19] == 0, 所以会发生除0异常，

调试器对异常的处理

观察HEX进制窗口，buffer 不满足前面两个条件，通过sub_402545和rip + 2处理异常

主要目的是对dword_405020做修改

sub_402545中有花

因为紧接着就是call的地址，所以不用jmp，直接Nop

再看sub_401CA7函数，有两个断点异常，且下两个字节分别符合0xc3和0x25, 0x25和0x25,

将rip跳走了两个字节，直接nop掉；

这样就可以f5了，虽然f5出来还是有点错误，主要是后面那点栈指针不平衡，但是还是能看，参数传递也分析失败了，这里我直接看的汇编，rcx为第一个参数，依次为rdx,r8,分别对应第二次输入，第一次输入，创建的文件的句柄。

F5出来的伪代码， - （45）作为分割点

然后进入sub_40239E比较

脚本：

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#include<iostream>
#include<cstdio>
#include<vector>
#include<cstring>
#include<sstream>

using namespace std;

vector<char> v;
string a[500];
int b[500];

int main()
{
    char v9[96]; // [rsp+40h] [rbp-40h] BYREF
    char v10[500]; // [rsp+A0h] [rbp+20h] BYREF
    unsigned char v26; // [rsp+3B61h] [rbp+3AE1h]
    unsigned char v27; // [rsp+3B62h] [rbp+3AE2h]
    unsigned char v28; // [rsp+3B63h] [rbp+3AE3h]
    int i; // [rsp+3B7Ch] [rbp+3AFCh]
    unsigned int miwen[376] = {
    0x0000001D, 0x0000006E, 0x0000004E, 0x0000003F, 0x00000039, 0x0000003A, 0x00000028, 0x00000029, 
    0x00000017, 0x00000014, 0x00000037, 0x00000046, 0x00000043, 0x00000030, 0x00000011, 0x00000012, 
    0x0000002D, 0x0000002E, 0x00000002, 0x0000000C, 0x00000030, 0x00000031, 0x00000032, 0x0000003E, 
    0x00000025, 0x00000026, 0x00000005, 0x00000076, 0x0000005E, 0x0000002D, 0x0000000F, 0x0000000C, 
    0x0000001D, 0x0000001E, 0x0000003F, 0x0000004C, 0x00000066, 0x00000015, 0x00000038, 0x0000003B, 
    0x00000015, 0x00000016, 0x00000006, 0x00000075, 0x0000006F, 0x0000001C, 0x00000003, 0x00000000, 
    0x0000000D, 0x0000007C, 0x0000007F, 0x00000003, 0x00000010, 0x0000006C, 0x0000007A, 0x0000000B, 
    0x00000005, 0x00000006, 0x0000002A, 0x0000002B, 0x00000021, 0x00000052, 0x0000007D, 0x0000000E, 
    0x00000050, 0x00000053, 0x0000007F, 0x0000007C, 0x0000005B, 0x0000005A, 0x00000056, 0x00000058, 
    0x0000006C, 0x00000010, 0x00000006, 0x00000077, 0x00000071, 0x00000072, 0x00000050, 0x00000051, 
    0x0000007D, 0x0000000E, 0x00000011, 0x00000062, 0x00000078, 0x0000007B, 0x0000006B, 0x00000068, 
    0x00000076, 0x00000078, 0x0000007E, 0x00000070, 0x00000071, 0x00000070, 0x00000043, 0x00000040, 
    0x0000005D, 0x00000051, 0x00000046, 0x0000003A, 0x00000005, 0x00000079, 0x00000042, 0x0000004C, 
    0x00000079, 0x0000007A, 0x00000057, 0x00000026, 0x00000023, 0x0000005F, 0x0000004A, 0x00000044, 
    0x0000006D, 0x0000006C, 0x0000006C, 0x0000006F, 0x00000049, 0x0000004A, 0x00000066, 0x00000067, 
    0x00000054, 0x0000005A, 0x0000005E, 0x00000050, 0x00000063, 0x00000062, 0x00000052, 0x00000051, 
    0x000000BD, 0x000000BE, 0x0000009D, 0x0000009C, 0x000000A9, 0x000000A8, 0x00000097, 0x00000099, 
    0x000000AD, 0x000000D1, 0x000000C6, 0x000000B7, 0x000000B1, 0x000000B2, 0x00000090, 0x000000E3, 
    0x000000DC, 0x000000A0, 0x000000B7, 0x000000B9, 0x0000008B, 0x0000008A, 0x000000BB, 0x000000B8, 
    0x000000A5, 0x000000A6, 0x000000B7, 0x000000B6, 0x00000082, 0x000000F1, 0x000000DD, 0x000000AE, 
    0x000000BE, 0x000000B0, 0x00000086, 0x0000008A, 0x00000099, 0x000000E8, 0x000000E5, 0x00000096, 
    0x000000B8, 0x000000B9, 0x000000B4, 0x000000C7, 0x000000E1, 0x00000092, 0x00000080, 0x00000083, 
    0x0000008D, 0x0000008E, 0x000000A2, 0x000000A3, 0x000000A5, 0x000000A4, 0x000000AB, 0x000000D8, 
    0x000000F7, 0x00000084, 0x00000094, 0x000000E7, 0x000000F1, 0x00000080, 0x00000083, 0x00000080, 
    0x000000D0, 0x000000A3, 0x00000081, 0x000000F2, 0x000000E9, 0x000000E8, 0x000000D9, 0x000000D8, 
    0x000000E6, 0x000000E7, 0x000000D5, 0x000000D6, 0x000000F1, 0x000000F2, 0x000000D1, 0x000000A2, 
    0x00000093, 0x00000092, 0x00000090, 0x000000E3, 0x000000C4, 0x000000C5, 0x000000C9, 0x000000C8, 
    0x000000C7, 0x000000C4, 0x000000E7, 0x000000E4, 0x000000C1, 0x000000C0, 0x000000F0, 0x000000F1, 
    0x000000F0, 0x000000F1, 0x000000FC, 0x0000008F, 0x000000A6, 0x000000D5, 0x000000F8, 0x000000FB, 
    0x000000D5, 0x000000D6, 0x000000C7, 0x000000B4, 0x0000008D, 0x0000008C, 0x000000A3, 0x000000D0, 
    0x000000DE, 0x000000DF, 0x000000EC, 0x000000ED, 0x000000E9, 0x000000EA, 0x000000CB, 0x000000BA, 
    0x000000BA, 0x000000C9, 0x000000E7, 0x00000094, 0x000000B0, 0x000000CC, 0x000000DB, 0x000000D5, 
    0x0000002E, 0x0000002F, 0x0000002C, 0x0000002F, 0x00000039, 0x0000003A, 0x00000016, 0x00000017, 
    0x00000017, 0x00000016, 0x00000017, 0x00000019, 0x00000029, 0x00000055, 0x00000041, 0x00000040, 
    0x00000052, 0x0000002E, 0x00000037, 0x0000003B, 0x00000029, 0x0000002A, 0x00000006, 0x00000075, 
    0x00000054, 0x00000028, 0x0000003F, 0x00000031, 0x00000030, 0x0000003E, 0x0000003A, 0x00000034, 
    0x0000000D, 0x0000007E, 0x0000006E, 0x0000001F, 0x00000019, 0x0000001A, 0x00000039, 0x0000004A, 
    0x00000049, 0x00000048, 0x00000065, 0x00000016, 0x0000003C, 0x0000003D, 0x00000002, 0x0000000C, 
    0x00000015, 0x00000069, 0x0000007E, 0x0000000F, 0x00000009, 0x0000000A, 0x0000002B, 0x00000058, 
    0x00000074, 0x00000007, 0x00000016, 0x00000018, 0x00000019, 0x00000017, 0x0000002F, 0x0000002E, 
    0x0000006D, 0x0000001E, 0x00000000, 0x00000071, 0x00000079, 0x0000007A, 0x0000006A, 0x00000019, 
    0x00000004, 0x00000077, 0x00000064, 0x00000017, 0x0000000F, 0x00000073, 0x0000006A, 0x00000064, 
    0x0000004D, 0x0000004C, 0x00000042, 0x00000041, 0x00000069, 0x00000018, 0x0000001B, 0x0000001A, 
    0x0000001B, 0x0000001A, 0x00000016, 0x00000065, 0x00000042, 0x0000004C, 0x0000007A, 0x00000006, 
    0x0000002D, 0x0000002C, 0x0000002E, 0x0000005F, 0x00000059, 0x0000005A, 0x00000076, 0x00000077, 
    0x00000075, 0x0000007B, 0x0000004E, 0x00000040, 0x00000073, 0x00000000, 0x00000021, 0x00000052, 
    0x00000060, 0x0000006E, 0x00000056, 0x0000002A, 0x00000036, 0x00000047, 0x0000004B, 0x00000078
    };
    for (int i = 374; i >= 0; i--)
        miwen[i] = miwen[i] ^ miwen[i + 1] ^ i;
    miwen[375] = 120;
    strcpy(v9, "ABCDEFGH");
    strcpy(&v9[9], "12345678");
    strcpy(&v9[18], "0IJKLMNO");
    strcpy(&v9[27], "+OPQRStu");
    strcpy(&v9[36], "\\vwxyzTU");
    strcpy(&v9[45], "abcdefgh");
    strcpy(&v9[54], "VWXYZijk");
    strcpy(&v9[63], "lmnopqrs");
    for (i = 0; i < 375; i+=2)
    {
        for (int j = 0; j <= 255; j++)
        {
            v28 = (j >> 6) & 1;
            v27 = (j >> 3) & 7;
            v26 = j & 7;
            v10[i] = v9[9 * v28 + v27];
            v10[i + 1] = v9[9 * v27 + v26];
            if (v10[i] == (unsigned char)miwen[i] && v10[i + 1] == (unsigned char)miwen[i + 1])
            {
                v.push_back(j);
                break;
            }
        }
    }
    vector<char>::iterator k = v.begin();
    i = 0;
    while(k != v.end())
    {
        if (*k == '#')
        {
            std::stringstream ss;
            ss << a[i];
            ss >> hex >> b[i];
            i++;
        }
        else
            a[i].push_back(*k);
        k++;
    }
    for (int j = i - 1; j >= 2; j--)
    {
        b[j] = b[j] - b[j - 1] - b[j - 2];
    }
    for (int j = 0; j < i; j++)
        printf("%c", b[j]);
    system("pause");
}

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