Tags: resources xor
Rating:
# re1 (re, 100pts)
List of executable resources viewed in Resource Hacker:
The most interesting function is 0x40111D:
```c++
signed int __stdcall sub_40111D(int a1)
{
HGLOBAL v1; // eax
HRSRC v2; // eax
HRSRC v3; // esi
HGLOBAL v4; // eax
const void *v5; // edi
HANDLE v6; // esi
signed int v7; // ecx
signed int v8; // eax
struct _STARTUPINFOA StartupInfo; // [esp+Ch] [ebp-80h]
DWORD v11; // [esp+50h] [ebp-3Ch]
DWORD NumberOfBytesWritten; // [esp+54h] [ebp-38h]
struct _PROCESS_INFORMATION ProcessInformation; // [esp+58h] [ebp-34h]
LPCVOID lpBuffer; // [esp+68h] [ebp-24h]
HANDLE hObject; // [esp+6Ch] [ebp-20h]
HRSRC hResInfo; // [esp+70h] [ebp-1Ch]
char v17; // [esp+74h] [ebp-18h]
char v18; // [esp+75h] [ebp-17h]
CHAR b_dll; // [esp+178h] [ebp+ECh]
char v20; // [esp+179h] [ebp+EDh]
CHAR FileName; // [esp+27Ch] [ebp+1F0h]
char v22; // [esp+27Dh] [ebp+1F1h]
CHAR CommandLine; // [esp+380h] [ebp+2F4h]
char v24; // [esp+381h] [ebp+2F5h]
char v25[12]; // [esp+3E4h] [ebp+358h]
b_dll = 0;
memset(&v20, 0, 0x103u);
FileName = 0;
memset(&v22, 0, 0x103u);
memset(&v18, 0, 0x103u);
GetTempPathA(0x104u, &b_dll);
GetTempPathA(0x104u, &FileName);
strcat_s(&b_dll, 0x104u, "b.dll");
strcat_s(&FileName, 0x104u, "2.exe");
hResInfo = FindResourceA(0, (LPCSTR)0x8D, "SYS");
GetLastError();
v1 = LoadResource(0, hResInfo);
lpBuffer = LockResource(v1);
hResInfo = (HRSRC)SizeofResource(0, hResInfo);
hObject = CreateFileA(&FileName, 0x10000000u, 1u, 0, 2u, 0x80u, 0);
WriteFile(hObject, lpBuffer, (DWORD)hResInfo, &NumberOfBytesWritten, 0);
CloseHandle(hObject);
v2 = FindResourceA(0, (LPCSTR)0x8E, "SYS");
v3 = v2;
v4 = LoadResource(0, v2);
v5 = LockResource(v4);
hObject = (HANDLE)SizeofResource(0, v3);
v6 = CreateFileA(&b_dll, 0x10000000u, 1u, 0, 2u, 0x80u, 0);
WriteFile(v6, v5, (DWORD)hObject, &v11, 0);
CloseHandle(v6);
strcpy(&v17, "qa\"apgcvg\"Rv\"v{rg?\"dkngq{q\"`klRcvj?\"");
v7 = 0;
do
{
*(&v17 + v7) ^= a1 - 48;
++v7;
}
while ( v7 < 36 );
strcpy(v25, "p`#pwbqw#Sw");
v8 = 0;
do
{
v25[v8] ^= a1 - 47;
++v8;
}
while ( v8 < 11 );
CommandLine = 0;
memset(&v24, 0, 0x63u);
sprintf(&CommandLine, "%d", a1);
memset(&StartupInfo, 0, 0x44u);
StartupInfo.cb = 68;
if ( !CreateProcessA(&FileName, &CommandLine, 0, 0, 0, 0, 0, 0, &StartupInfo, &ProcessInformation) )
return 1;
WaitForSingleObject(ProcessInformation.hProcess, 0xFFFFFFFF);
CloseHandle(ProcessInformation.hThread);
CloseHandle(ProcessInformation.hProcess);
DeleteFileA(&b_dll);
DeleteFileA(&FileName);
return 1;
}
```
It loads the `SYS1` resource and saves it into `b.dll` and stores `SYS2` in `2.exe` and executes it.
`2.exe` loads data from `b.dll` again, xors it with a certain byte and stores it as `flag.dll`:
```c++
signed int __stdcall sub_40111D(int a1)
{
HGLOBAL v1; // eax
HRSRC v2; // eax
HRSRC v3; // esi
HGLOBAL v4; // eax
const void *v5; // edi
HANDLE v6; // esi
signed int v7; // ecx
signed int v8; // eax
struct _STARTUPINFOA StartupInfo; // [esp+Ch] [ebp-80h]
DWORD v11; // [esp+50h] [ebp-3Ch]
DWORD NumberOfBytesWritten; // [esp+54h] [ebp-38h]
struct _PROCESS_INFORMATION ProcessInformation; // [esp+58h] [ebp-34h]
LPCVOID lpBuffer; // [esp+68h] [ebp-24h]
HANDLE hObject; // [esp+6Ch] [ebp-20h]
HRSRC hResInfo; // [esp+70h] [ebp-1Ch]
char v17; // [esp+74h] [ebp-18h]
char v18; // [esp+75h] [ebp-17h]
CHAR b_dll; // [esp+178h] [ebp+ECh]
char v20; // [esp+179h] [ebp+EDh]
CHAR FileName; // [esp+27Ch] [ebp+1F0h]
char v22; // [esp+27Dh] [ebp+1F1h]
CHAR CommandLine; // [esp+380h] [ebp+2F4h]
char v24; // [esp+381h] [ebp+2F5h]
char v25[12]; // [esp+3E4h] [ebp+358h]
b_dll = 0;
memset(&v20, 0, 0x103u);
FileName = 0;
memset(&v22, 0, 0x103u);
memset(&v18, 0, 0x103u);
GetTempPathA(0x104u, &b_dll);
GetTempPathA(0x104u, &FileName);
strcat_s(&b_dll, 0x104u, "b.dll");
strcat_s(&FileName, 0x104u, "2.exe");
hResInfo = FindResourceA(0, (LPCSTR)141, "SYS");
GetLastError();
v1 = LoadResource(0, hResInfo);
lpBuffer = LockResource(v1);
hResInfo = (HRSRC)SizeofResource(0, hResInfo);
hObject = CreateFileA(&FileName, 0x10000000u, 1u, 0, 2u, 0x80u, 0);
WriteFile(hObject, lpBuffer, (DWORD)hResInfo, &NumberOfBytesWritten, 0);
CloseHandle(hObject);
v2 = FindResourceA(0, (LPCSTR)142, "SYS");
v3 = v2;
v4 = LoadResource(0, v2);
v5 = LockResource(v4);
hObject = (HANDLE)SizeofResource(0, v3);
v6 = CreateFileA(&b_dll, 0x10000000u, 1u, 0, 2u, 0x80u, 0);
WriteFile(v6, v5, (DWORD)hObject, &v11, 0);
CloseHandle(v6);
strcpy(&v17, "qa\"apgcvg\"Rv\"v{rg?\"dkngq{q\"`klRcvj?\"");// sc create Pt type= filesys binPath=
v7 = 0;
do
{
*(&v17 + v7) ^= a1 - 48;
++v7;
}
while ( v7 < 36 );
strcpy(v25, "p`#pwbqw#Sw"); // sc start Pt
v8 = 0;
do
{
v25[v8] ^= a1 - 47;
++v8;
}
while ( v8 < 11 );
CommandLine = 0;
memset(&v24, 0, 0x63u);
sprintf(&CommandLine, "%d", a1);
memset(&StartupInfo, 0, 'D');
StartupInfo.cb = 'D';
if ( !CreateProcessA(&FileName, &CommandLine, 0, 0, 0, 0, 0, 0, &StartupInfo, &ProcessInformation) )
return 1;
WaitForSingleObject(ProcessInformation.hProcess, 0xFFFFFFFF);
CloseHandle(ProcessInformation.hThread);
CloseHandle(ProcessInformation.hProcess);
DeleteFileA(&b_dll);
DeleteFileA(&FileName);
return 1;
}
```
Xoring the entire resource with 0x36 yields a following result:
