一次逆向fb寻找密码的记录及还原相关算法

Editor 2018-08-09 16:10

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

#include

#include

#include

#include

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    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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