reading data from process' memory with Python

Question

I'm trying to read data from memory of a process by inputing the process name, then finding PID using psutil. So far I have this:

import ctypes
from ctypes import *
from ctypes.wintypes import *
import win32ui
import psutil # install, not a default module
import sys

# input process name
nameprocess = "notepad.exe"

# find pid
def getpid():
    for proc in psutil.process_iter():
        if proc.name() == nameprocess:
            return proc.pid

PROCESS_ID = getpid()

if PROCESS_ID == None:
    print "Process was not found"
    sys.exit(1)


# read from addresses
STRLEN = 255

PROCESS_VM_READ = 0x0010
process = windll.kernel32.OpenProcess(PROCESS_VM_READ, 0, PROCESS_ID)
readProcMem = windll.kernel32.ReadProcessMemory
buf = ctypes.create_string_buffer(STRLEN)

for i in range(1,100): 
    if readProcMem(process, hex(i), buf, STRLEN, 0):
        print buf.raw

The last for loop should read and print contents of the first 100 addresses in the process if I'm getting this right. Only thing is, the output looks like complete gibberish.

There are 2 problems for me here: first, am I really reading the addresses from the selected process this way? And second, how can I figure how long in the loop I should go, if there is maybe some kind of end address?

Answer 1

I didn't install psutil, but just pulled a process ID and valid virtual address using Task Manager and SysInternals VMMap. The numbers will vary of course.

Good practice with ctypes is to define the argument types and return value via .argtypes and .restype. Get your own instance of the kernel32 library because changing the attributes of the cached windll.kernel32 instance could cause issues with other modules using ctypes and kernel32.

You need a valid virtual address. In answer to your 2nd problem, I think VMMap proves there is a way to do it. Pick up a copy of Windows Internals to learn the techniques.

from ctypes import *
from ctypes.wintypes import *

PROCESS_ID = 9476 # From TaskManager for Notepad.exe
PROCESS_HEADER_ADDR = 0x7ff7b81e0000 # From SysInternals VMMap utility

# read from addresses
STRLEN = 255

PROCESS_VM_READ = 0x0010

k32 = WinDLL('kernel32')
k32.OpenProcess.argtypes = DWORD,BOOL,DWORD
k32.OpenProcess.restype = HANDLE
k32.ReadProcessMemory.argtypes = HANDLE,LPVOID,LPVOID,c_size_t,POINTER(c_size_t)
k32.ReadProcessMemory.restype = BOOL

process = k32.OpenProcess(PROCESS_VM_READ, 0, PROCESS_ID)
buf = create_string_buffer(STRLEN)
s = c_size_t()
if k32.ReadProcessMemory(process, PROCESS_HEADER_ADDR, buf, STRLEN, byref(s)):
    print(s.value,buf.raw)

Output (Note 'MZ' is the start of a program header):

255 b'MZx90x00x03x00x00x00x04x00x00x00xffxffx00x00xb8x00x00x00x00x00x00x00@x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00x00xe8x00x00x00x0ex1fxbax0ex00xb4xcd!xb8x01Lxcd!This program cannot be run in DOS mode.

$x00x00x00x00x00x00x00xd0x92xa7xd1x94xf3xc9x82x94xf3xc9x82x94xf3xc9x82x9dx8bZx82x8axf3xc9x82xfbx97xcax83x97xf3xc9x82xfbx97xcdx83x83xf3xc9x82xfbx97xccx83x91xf3xc9x82xfbx97xc8x83x8fxf3xc9x82x94xf3xc8x82x82xf2xc9x82xfbx97xc1x83x8dxf3xc9x82xfbx976x82x95xf3xc9x82xfbx97xcbx83x95xf3xc9x82Richx94xf3xc9x82x00x00x00x00x00x00x00x00PEx00x00dx86x06x00^'x0fx84x00x00x00x00x00x00x00x00xf0x00"'

Here's a screenshot of VMMap indicating the header address of notepad.exe:

Here's a screenshot of a hexdump of the content of notepad.exe that matches the output of the program: