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[原创]一次逆向fb寻找密码的记录及还原相关算法
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2018-7-19 11:52
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嗯.开始写了。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
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。
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，
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。。。
[培训]《安卓高级研修班(网课)》月薪三万计划，掌握调试、分析还原ollvm、vmp的方法，定制art虚拟机自动化脱壳的方法
最后于 2018-7-19 14:19
被wx_clay编辑
，原因：
