一次逆向fb寻找密码的记录及还原相关算法

首先用peid查壳。



一个ASProtect v1.23RC1 *的壳，然后我到网上搜了下有没有相关的脱壳教程，在这里发现了一篇https://bbs.pediy.com/thread-207728.htm 但是他的脱壳方法有些麻烦，而且很多步骤都没有说明原因,只能自己脱了，首先用od载入程序，单步了几下，发现一个pushad



然后用esp定律，f9 断在这个地方


接着单步几下，发现没有oep特征，由此可知这个加了几层壳，继续单步，发现单步很久都没发现啥，如果你有耐心，会发现到后面还会出现几次pushad ，大概要单步几千次吧，，于是我又用了几次esp定律，继续单步，发现这玩意一直带着我在几个函数之间转圈圈，，我当时调这个应该是调了一天，，这么一直转下去不是办法，只能用点特殊的办法，让他帮我们还原到最接近oep的地方，我对esp有特征的下硬件断点，然后记录f9的次数，和啥时候该下断点，



这是当时调试记录的笔记=-=。倒数第四行那里我发现，f9 71次时代码已经被还原。于是就从70次开始单步，本来以为离oep已经很近了的，结果一单步下来又是几千条指令，单步了几个小时还是没发现oep。指令还是在几个函数间转圈圈,本来我打算继续用之前的办法再缩小到oep的距离的。可这样下去不是办法，于是，尝试直接f9，从堆栈中倒着来找oep，选了几个堆栈返回地址，





在这个地址往上翻了翻就翻到了oep。



一个典型的vc++的oep，然后开始脱壳分析。用od载入脱完壳的程序。搜索所有字符串



看见了这几个网址，点进去，再用ida打开，找到相关函数f5。
signed int __thiscall sub_406540(void *this, int a2) { int v2; // ebx@1 int v3; // esi@1 int v4; // ebp@2 int v5; // edx@2 const char **v6; // edi@3 int v7; // ebp@11 const char **v8; // edi@12 int v9; // edx@17 DWORD v10; // eax@20 const char *v11; // eax@21 bool v12; // bl@22 bool v13; // bl@23 int v14; // ebp@26 int v15; // edx@26 const char **v16; // edi@27 wchar_t *v18; // eax@54 const char *v19; // eax@56 bool v20; // bl@57 bool v21; // bl@58 int v22; // ebp@61 int v23; // edx@61 const char **v24; // edi@62 const char *v25; // [sp+28h] [bp-C74h]@1 int i; // [sp+2Ch] [bp-C70h]@1 LPVOID ppv; // [sp+30h] [bp-C6Ch]@1 DWORD dwIndex; // [sp+34h] [bp-C68h]@3 int v29; // [sp+38h] [bp-C64h]@1 DWORD cchValueName; // [sp+3Ch] [bp-C60h]@1 DWORD cbData; // [sp+40h] [bp-C5Ch]@12 char v32; // [sp+44h] [bp-C58h]@1 int v33; // [sp+48h] [bp-C54h]@3 int v34; // [sp+4Ch] [bp-C50h]@1 int v35; // [sp+58h] [bp-C44h]@23 int v36; // [sp+5Ch] [bp-C40h]@21 HKEY phkResult; // [sp+60h] [bp-C3Ch]@18 int v38; // [sp+64h] [bp-C38h]@52 char v39; // [sp+68h] [bp-C34h]@52 LPCWSTR lpWideCharStr; // [sp+6Ch] [bp-C30h]@54 CHAR ValueName; // [sp+90h] [bp-C0Ch]@20 BYTE Data; // [sp+490h] [bp-80Ch]@20 int v43; // [sp+C98h] [bp-4h]@1 cchValueName = (DWORD)this; v25 = (const char *)dword_5FAB30; v43 = 0; v29 = 0; ppv = 0; LOBYTE(v43) = 2; sub_5810E6(&v32); LOBYTE(v43) = 3; CStringArray::SetAtGrow((CStringArray *)&v32, v34, "http://www.facebook.com"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "http://www.facebook.com/"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "https://login.facebook.com"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "https://login.facebook.com/"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "http://www.facebook.com/login.php"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "http://www.facebook.com/index.php"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "https://www.google.com/accounts/servicelogin"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "https://www.regnow.com/vendorpriv/"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "https://www.regnow.com/affiliatepriv/"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "http://127.0.0.1/phpmyadmin/"); CStringArray::SetAtGrow((CStringArray *)&v32, v34, "http://www.yandex.ru/"); v2 = a2; v3 = 0; for ( i = 0; v3 < v34; i = v3 ) { v4 = *(_DWORD *)(v2 + 8); v5 = 0; if ( v4 > 0 ) { v6 = *(const char ***)(v2 + 4); dwIndex = *(_DWORD *)(v33 + 4 * v3); do { if ( !strcmp((const char *)dwIndex, *v6) ) break; ++v5; ++v6; } while ( v5 < v4 ); v3 = i; v2 = a2; } if ( v5 == v4 ) sub_581340(v2, v4, v33 + 4 * v3); ++v3; } i = 0; if ( *(_DWORD *)(cchValueName + 8) > 0 ) { do { v7 = *(_DWORD *)(v2 + 8); dwIndex = 0; if ( v7 > 0 ) { v8 = *(const char ***)(v2 + 4); cbData = *(_DWORD *)(*(_DWORD *)(cchValueName + 4) + 4 * i); do { if ( !strcmp((const char *)cbData, *v8) ) break; ++v8; ++dwIndex; } while ( (signed int)dwIndex < v7 ); } if ( dwIndex == v7 ) sub_581340(v2, v7, *(_DWORD *)(cchValueName + 4) + 4 * i); v9 = *(_DWORD *)(cchValueName + 8); ++i; } while ( i < v9 ); } if ( !RegOpenKeyExA(HKEY_CURRENT_USER, "Software\\Microsoft\\Internet Explorer\\TypedURLs", 0, 1u, &phkResult) )// 打开注册表 { dwIndex = 0; while ( 1 ) { v10 = dwIndex++; Data = 0; ValueName = 0; cbData = 2048; cchValueName = 1024; if ( RegEnumValueA(phkResult, v10, &ValueName, &cchValueName, 0, 0, &Data, &cbData) )// 遍历注册表，第一个参数是打开的注册表句柄，第二个参数是遍历的index，第三个参数是接收注册表键名的缓冲区，第四个参数指定第三个缓冲区的大小，倒数第二个是键值的缓冲区，最后一个参数指定前一个的大小 break; CString::operator=((CString *)&v25, (char *)&Data);// 把键值赋值给v25 v11 = *(const char **)sub_57F15A(&v25, (int)&v36, 4u); LOBYTE(v43) = 4; if ( !strcmp(v11, "http") || (v12 = strcmp(*(const char **)sub_57F15A(&v25, (int)&i, 3u), (const char *)&dword_5F882C) == 0, sub_58643C(&i), v12) || (v13 = strcmp(*(const char **)sub_57F15A(&v25, (int)&v35, 3u), (const char *)&off_5F8828) == 0, sub_58643C(&v35), v13) ) { v13 = 1; } LOBYTE(v43) = 3; sub_58643C(&v36); if ( v13 ) { v14 = 0; v15 = *(_DWORD *)(a2 + 8); if ( v15 > 0 ) { v16 = *(const char ***)(a2 + 4); do { if ( !strcmp(v25, *v16) ) // 如果键值和a2偏移4的那个变量不相等，则跳出循环 break; ++v14; ++v16; // 跟下一条字符串进行比较 } while ( v14 < v15 ); } if ( v14 == v15 ) // 若没找到fb官网的键值 sub_581340(a2, v15, (int)&v25); // 调用这个函数 } } RegCloseKey(phkResult); } if ( ppv ) (*(void (__stdcall **)(LPVOID))(*(_DWORD *)ppv + 8))(ppv);// 释放对象 ppv = 0; if ( CoCreateInstance(&rclsid, 0, 1u, &riid, &ppv) < 0 )// 创建一个com对象 { LOBYTE(v43) = 2; CStringArray::~CStringArray((CStringArray *)&v32); LOBYTE(v43) = 1; if ( ppv ) (*(void (__stdcall **)(LPVOID))(*(_DWORD *)ppv + 8))(ppv);// 释放对象 LOBYTE(v43) = 0; if ( v29 ) (*(void (__stdcall **)(int))(*(_DWORD *)v29 + 8))(v29); LABEL_49: v43 = -1; sub_58643C(&v25); return 0; } if ( v29 ) (*(void (__stdcall **)(int))(*(_DWORD *)v29 + 8))(v29); v29 = 0; if ( !ppv ) sub_449BF9(-2147467261); if ( (*(int (__stdcall **)(LPVOID, int *))(*(_DWORD *)ppv + 28))(ppv, &v29) < 0 )// 调用进程中的某个方法，得到一个新的函数地址 { LOBYTE(v43) = 2; CStringArray::~CStringArray((CStringArray *)&v32); LOBYTE(v43) = 1; if ( ppv ) (*(void (__stdcall **)(LPVOID))(*(_DWORD *)ppv + 8))(ppv);// 释放对象 LOBYTE(v43) = 0; if ( v29 ) (*(void (__stdcall **)(int))(*(_DWORD *)v29 + 8))(v29); goto LABEL_49; } while ( 1 ) { if ( !v29 ) sub_449BF9(-2147467261); if ( (*(int (__stdcall **)(int, signed int, char *, int *))(*(_DWORD *)v29 + 12))(v29, 1, &v39, &v38) < 0 || !v38 )// 得到ie最近的历史记录， break; v18 = wcschr(lpWideCharStr, 0x3Fu); if ( v18 ) *v18 = 0; CString::operator=((CString *)&v25, lpWideCharStr); v19 = *(const char **)sub_57F15A(&v25, (int)&cbData, 4u); LOBYTE(v43) = 5; if ( !strcmp(v19, "http") || (v20 = strcmp(*(const char **)sub_57F15A(&v25, (int)&v36, 3u), (const char *)&dword_5F882C) == 0, sub_58643C(&v36), v20) || (v21 = strcmp(*(const char **)sub_57F15A(&v25, (int)&v35, 3u), (const char *)&off_5F8828) == 0, sub_58643C(&v35), v21) ) { v21 = 1; } LOBYTE(v43) = 3; sub_58643C(&cbData); if ( v21 ) { v22 = 0; v23 = *(_DWORD *)(a2 + 8); if ( v23 > 0 ) // 遍历他，对比程序前面的几个http链接 { v24 = *(const char ***)(a2 + 4); do { if ( !strcmp(*v24, v25) ) break; ++v22; ++v24; } while ( v22 < v23 ); } if ( v22 == v23 ) sub_581340(a2, v23, (int)&v25); } } LOBYTE(v43) = 2; CStringArray::~CStringArray((CStringArray *)&v32); LOBYTE(v43) = 1; if ( ppv ) (*(void (__stdcall **)(LPVOID))(*(_DWORD *)ppv + 8))(ppv); LOBYTE(v43) = 0; if ( v29 ) (*(void (__stdcall **)(int))(*(_DWORD *)v29 + 8))(v29); v43 = -1; sub_58643C(&v25); return 1; }
分析之后我们发现他是从注册表的





这个注册表里存着的是ie收藏的url。



查找比对url，然后再调用ieframe.dll里面的某个函数来获取历史记录，至于是什么函数目前我还没办法知道。ida也分析不出来..可能只能去调那个dll?看功能来分析？不过我后来获取了一下ieframe的导出表。查看了一下导出函数，想到可能可以从基址偏移来看调用的是哪个函数。他调用那个函数取出来的也是一些url。是ie的历史url缓存，这个函数大概的意思就是把url都取出来然后push到一个类似vector的结构里面存着。解密的关键并不在这里。在字符串搜索里我们还看见了一串注册表的位置，



打开相应位置看看，



发现是一些加密数据，可能关键就在这里了，往下翻，发现调用了这个函数



具体代码请自行分析，跟进



继续跟进，



发现在这个函数里调用了关键函数，



CryptUnprotectData，其中第一个参数是加密数据的结构体，图中a2便是加密数据的地址，a3是加密时的附加嫡，为url的登陆链接的字节码，解密完了的数据在pDataout结构体里，用od调试看看，



这个是最后那个解密完数据存放的地址，



解密之前，



解密之后，前四个字节是此解密数据的大小，后四个字节是解密数据的地址，



大概就是这些数据了，我们可以很明显的看到在最后面存放着我们需要的密码，test123，密码是我自己测试设置的，

然后此函数处理这些解密数据，得到密码



跟进

#define _CRT_SECURE_NO_WARNINGS #pragma comment(lib,"Crypt32.lib") #include <Windows.h> #include <dpapi.h> #include <iostream> #include <cwchar> #include <atlstr.h> unsigned int convert(int* a1, unsigned int a5); int main() { DATA_BLOB DataIn; std::cout << sizeof(DATA_BLOB) << std::endl; DATA_BLOB DataOut; DATA_BLOB pOptionalEntropy; char dest[100] = {0}; BYTE bpkey[310] { 0x01,0x00,0x00,0x00,0xD0,0x8C,0x9D,0xDF,0x01,0x15,0xD1,0x11,0x8C,0x7A,0x00,0xC0, 0x4F,0xC2,0x97,0xEB,0x01,0x00,0x00,0x00,0xC0,0x6E,0xDE,0xB1,0x74,0x52,0xCB,0x46, 0x9F,0xF5,0x92,0x73,0x39,0x9D,0x52,0x72,0x00,0x00,0x00,0x00,0x02,0x00,0x00,0x00, 0x00,0x00,0x10,0x66,0x00,0x00,0x00,0x01,0x00,0x00,0x20,0x00,0x00,0x00,0x03,0x9F, 0x65,0xE0,0x95,0xEC,0x94,0xE1,0x55,0x78,0x8D,0x0F,0x7F,0xF6,0x79,0x98,0x16,0xEF, 0xB3,0xB8,0x11,0x2A,0x6E,0x9B,0xD1,0xCC,0x37,0xC5,0xFB,0x36,0x4F,0x7F,0x00,0x00, 0x00,0x00,0x0E,0x80,0x00,0x00,0x00,0x02,0x00,0x00,0x20,0x00,0x00,0x00,0x0C,0x92, 0xA1,0xB9,0x50,0x34,0x45,0xE9,0xF4,0xEC,0x1D,0x8E,0xF2,0x51,0x6D,0xA1,0x95,0x1A, 0xB9,0xE5,0x93,0x27,0xEB,0x44,0x61,0x37,0xAD,0xD4,0x73,0xB4,0x04,0xC6,0x60,0x00, 0x00,0x00,0xA1,0x60,0x4E,0xA4,0x84,0x8A,0x7A,0x21,0x3A,0xC9,0x32,0x94,0xD0,0x0E, 0x94,0x77,0x22,0x2B,0x05,0x42,0xB5,0xE7,0x3B,0x4B,0x2F,0x7E,0x1B,0x8A,0x77,0x79, 0x30,0x98,0xFD,0xBB,0x06,0x22,0xAE,0x8C,0x0F,0xAA,0x9D,0xA8,0x27,0x57,0x79,0x18, 0x8E,0x6A,0x8E,0xBD,0x4C,0x43,0xEF,0xF8,0x5B,0x7C,0xED,0x8E,0x1A,0xA0,0x63,0x8D, 0x9E,0xBA,0xE2,0x60,0xA8,0x99,0xCE,0xFC,0xE7,0xE8,0x80,0xC0,0xFA,0x71,0x58,0x6A, 0xC2,0x08,0x9A,0x4F,0x1B,0xFC,0x47,0x88,0x56,0x0D,0xE4,0x06,0x1A,0x53,0x66,0xFC, 0x70,0x7C,0x40,0x00,0x00,0x00,0x40,0xEB,0xD0,0x8F,0xE7,0x12,0xF6,0x7F,0xAB,0x9A, 0x92,0x00,0xDA,0xA1,0x1B,0xB4,0xF2,0x66,0x54,0xE7,0x92,0x10,0xFD,0xB0,0xC0,0x6B, 0xEC,0xDF,0x20,0x11,0x63,0xB1,0xA0,0x08,0xE0,0x31,0xE5,0x4A,0x05,0xF8,0x59,0x61, 0x91,0x2D,0x93,0xC0,0x90,0xB0,0x41,0xBF,0x14,0x53,0xEA,0x65,0x1E,0xC5,0x95,0x98, 0xFA,0x5A,0xB8,0x70,0xFA,0x64 }; BYTE url[66]{ 0x68,0x00,0x74,0x00,0x74,0x00,0x70,0x00,0x3A,0x00,0x2F,0x00,0x2F,0x00,0x77,0x00, 0x77,0x00,0x77,0x00,0x2E,0x00,0x33,0x00,0x76,0x00,0x62,0x00,0x6F,0x00,0x6F,0x00, 0x6B,0x00,0x73,0x00,0x2E,0x00,0x63,0x00,0x6F,0x00,0x6D,0x00,0x2F,0x00,0x6C,0x00, 0x6F,0x00,0x67,0x00,0x69,0x00,0x6E,0x00,0x2E,0x00,0x70,0x00,0x68,0x00,0x70,0x00 }; DataIn.pbData = (byte*)bpkey; DataIn.cbData = 310; DataOut.cbData = 0; DataOut.pbData = 0; pOptionalEntropy.pbData = (BYTE*)url; pOptionalEntropy.cbData = 66; if (CryptUnprotectData( &DataIn, 0, &pOptionalEntropy, // Optional entropy NULL, // Reserved NULL, // Here, the optional // prompt structure is not // used. 1, &DataOut)) { convert((int*)DataOut.pbData, DataOut.cbData); //printf("%s", result); LocalFree(DataOut.pbData); } else { printf("%d", GetLastError()); printf("Decryption error!"); } system("pause"); return 0; } unsigned int convert(int* a1, unsigned int a5) { int *v5; // esi@1 unsigned int result; // eax@1 int v7; // edi@1 BYTE * v8; // eax@2 size_t v9; // eax@3 int v10; // ebx@3 WCHAR* v13; size_t v11; // edi@4 WCHAR* v12; // [sp+8h] [bp-4h]@3 v5 = (int *)(a1 + 1); printf("%x\t%x\n", v5,a1); int v6 = *v5 + *a1; if (v6 + 2 < a5) { v8 = (BYTE*)a1 + a5; //printf("%x", v8); *(v8 - 1) = 0; *(v8 - 2) = 0; //do //{ printf("%x\n", v6); v12 = (WCHAR*)(v6/4 + a1); printf("%ls\n", v12); v9 = wcslen(v12); v10 = v6 + 2 * v9 + 2; result = v10+2; if (result > a5) return 1; printf("%x\n", v10); v13 = (WCHAR*)(v10 + (BYTE*)a1); printf("%ls", v13); v11 = 2 * wcslen((const wchar_t *)(v10/4 + a1)); //(**a2)(a3, a4, v12, v10 + v5); //} while (v6 + 2 < a5); } return 0; }
上面是我还原的关键算法，

运行结果：


另外吐槽一下od的udd保存的文件注释那些竟然只看文件名，不看路径，我在od里写的注释在载入其他程序的时候全都没了，心塞......




本文由看雪论坛 clay 原创，看雪ID：clay http://bbs.pediy.com/user-757651
转载请注明来自看雪社区


原文链接：[原创]一次逆向fb寻找密码的记录及还原相关算法-『软件逆向』-看雪安全论坛

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