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my_debugger.py
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my_debugger.py
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from ctypes import *
from my_debugger_defines import *
kernel32 = windll.kernel32
class debugger():
def __init__(self):
self.h_process = None
self.pid = None
self.debugger_active = False
self.h_thread = None
self.context = None
# self.exception_address = None
self.software_breakpoints = {}
self.first_breakpoints = True
self.hardware_breakpoints = {}
# Here let's determine and store the default
# page size for the system.
system_info = SYSTEM_INFO()
kernel32.GetSystemInfo(byref(system_info))
self.page_size = system_info.dwPageSize
self.guarded_pages = []
self.memory_breakpoints = {}
def load(self, path_to_exe):
# by dwCreationFlags,
# it decide how to generate process
# for example, if you want to look at gui of calucurator,
# you should type "creation_flags = CREATE_NEW_CONSOLE"
creation_flags = DEBUG_PROCESS
# instantiate Structure
startupinfo = STARTUPINFO()
process_infomation = PROCESS_INFOMATION()
# Because of next two ooption, started process
# would be show other window.
# This is an example that
# setting about STARTUPINFO Structure
# effects a debug target
startupinfo.dwFlags = 0x1
startupinfo.wShowWindow = 0x0
# init var `cb` that show size of STARTUPINFO Structure
startupinfo.cb = sizeof(startupinfo)
if kernel32.CreateProcessA(path_to_exe,
None,
None,
None,
None,
creation_flags,
None,
None,
byref(startupinfo),
byref(process_infomation)):
print "[*] We have successfully launched the proccess!"
print "[*] PID: %d" % process_infomation.dwProcessId
# get handle of process
# and save for use in future
self.h_process = self.open_process(process_infomation.dwProcessId)
else:
print "[*] Error: 0x%08x." % kernel32.GetLastError()
def open_process(self,pid):
h_process = kernel32.OpenProcess(PROCESS_ALL_ACCESS,False,pid)
return h_process
def attach(self,pid):
self.h_process = self.open_process(pid)
# try to attach to process
# if it failed, back to invoker
if kernel32.DebugActiveProcess(pid):
self.debugger_active = True
self.pid = int(pid)
else:
print "[*] Unable to attach to the process."
def run(self):
# wait for debugEvent
# from target process of debug
while self.debugger_active == True:
self.get_debug_event()
def get_debug_event(self):
debug_event = DEBUG_EVENT()
continue_status = DBG_CONTINUE
if kernel32.WaitForDebugEvent(byref(debug_event), INFINITE):
# # we havnt set eventHandler yet,
# # so we restart process
# raw_input("Press a key to continue...")
# self.debugger_active = False
# get infomation of thread and context
self.h_thread = self.open_thread(debug_event.dwThreadId)
self.context = self.get_thread_context(h_thread=self.h_thread)
print "Event Code: %d Thread ID: %d" %(debug_event.dwDebugEventCode,
debug_event.dwThreadId)
# if Event Code shows exception,
# chek more
if debug_event.dwDebugEventCode == EXCEPTION_DEBUG_EVENT:
# check Exception Code
exception = debug_event.u.Exception.ExceptionRecord.ExceptionCode
self.exception_address = debug_event.u.Exception.ExceptionRecord.ExceptionAddress
print exception
if exception == EXCEPTION_ACCESS_VIOLATION:
print "Access Violation Detected."
# if it is break point,
# call inside handler
elif exception == EXCEPTION_BREAKPOINT:
continue_status = self.exception_handler_breakpoint()
elif exception == EXCEPTION_GUARD_PAGE:
print "Guard Page Access Detected."
elif exception == EXCEPTION_SINGLE_STEP:
self.exception_handler_single_step()
kernel32.ContinueDebugEvent(
debug_event.dwProcessId,
debug_event.dwThreadId,
continue_status)
def detach(self):
if kernel32.DebugActiveProcessStop(self.pid):
print "[*] Finished debugging. Exiting..."
return True
else:
print "There was an error"
return False
def open_thread(self, thread_id):
h_thread = kernel32.OpenThread(THREAD_ALL_ACCESS, None, thread_id)
if h_thread is not 0:
return h_thread
else:
print "[*] Could not obtain a valid thread handle."
return False
def enumerate_threads(self):
thread_entry = THREADENTRY32()
thread_list = []
snapshot = kernel32.CreateToolhelp32Snapshot(
TH32CS_SNAPTHREAD, self.pid)
if snapshot is not None:
# you'l have fault if you set Size of Structure.
thread_entry.dwSize = sizeof(thread_entry)
success = kernel32.Thread32First(snapshot,
byref(thread_entry))
while success:
if thread_entry.th32OwnerProcessID == self.pid:
thread_list.append(thread_entry.th32ThreadID)
success = kernel32.Thread32Next(snapshot,
byref(thread_entry))
kernel32.CloseHandle(snapshot)
return thread_list
else:
return False
def get_thread_context(self, thread_id=None, h_thread=None):
context = CONTEXT()
context.ContextFlags = CONTEXT_FULL | CONTEXT_DEBUG_REGISTERS
# get handle of thread
if h_thread is None:
h_thread = self.open_thread(thread_id)
if kernel32.GetThreadContext(h_thread, byref(context)):
kernel32.CloseHandle(h_thread)
return context
else:
return False
def exception_handler_breakpoint(self):
print "[*] Inside the breakpoint handler."
print "Exception Address: 0x%08x" % self.exception_address
return DBG_CONTINUE
def read_process_memory(self, address, length):
data = ""
read_buf = create_string_buffer(length)
count = c_ulong(0)
if not kernel32.ReadProcessMemory(self.h_process,
address,
read_buf,
length,
byref(count)):
return False
else:
data += read_buf.raw
return data
def write_process_memory(self, address, data):
count = c_ulong(0)
length = len(data)
c_data = c_char_p(data[count.value:])
if not kernel32.WriteProcessMemory(self.h_process,
address,
c_data,
length,
byref(count)):
return False
else:
return True
def bp_set_hw(self, address, length, condition):
# check whether length value is valid
if length not in (1, 2, 4):
return False
else:
length -= 1
# check whether condition value is valid
if condition not in (HW_ACCESS, HW_EXECUTE, HW_WRITE):
return False
# check empty resister
if not self.hardware_breakpoints.has_key(0):
available = 0
elif not self.hardware_breakpoints.has_key(1):
available = 1
elif not self.hardware_breakpoints.has_key(2):
available = 2
elif not self.hardware_breakpoints.has_key(3):
available = 3
else:
return False
# for all resisters, set debug resister.
for thread_id in self.enumerate_threads():
context = self.get_thread_context(thread_id=thread_id)
# enable the appropriate flag in DR7
# resister to set breakpoint
context.Dr7 |= 1 << (available * 2)
# set breakpoint to empty resister
if available == 0:
context.Dr0 = address
elif available == 1:
context.Dr1 = address
elif available == 2:
context.Dr2 = address
elif available == 3:
context.Dr3 = address
# set type of breakpoint
context.Dr7 |= condition << ((available * 4) + 16)
# set length of breakpoint
context.Dr7 |= length << ((available * 4) + 18)
# set threadcontext set with the break set
h_thread = self.open_thread(thread_id)
kernel32.SetThreadContext(h_thread, byref(context))
# update the internal hardware breakpoint array at the used
# slot index.
self.hardware_breakpoints[available] = (address, length, condition)
return True
def bp_set_sw(self, address):
print "[*] Setting breakpoint at: 0x%08x" % address
if not self.software_breakpoints.has_key(address):
try:
# save original byte
original_byte = self.read_process_memory(address, 1)
# write opecode INT3
self.write_process_memory(address, "\xCC")
# resister breakpoint at indside list
self.software_breakpoints[address] = (original_byte)
# print "Succeeded set breakpoint."
except Exception as e:
print "[x] Failed to set breakpoint."
print '[x] Type:' + str(type(e))
print '[x] Args:' + str(e.args)
print '[x] Message:' + e.message
print '[x] Error:' + str(e)
return False
return True
def func_resolve(self, dll, function):
handle = kernel32.GetModuleHandleA(dll)
address = kernel32.GetProcAddress(handle, function)
kernel32.CloseHandle(handle)
return address
def exception_handler_single_step(self):
# Comment from PyDbg:
# determine if this single step event occuered in reaction to a
# hardware breakpoint and grab the hit breakpoint.
# according to the intel docs, we should be able to check for
# the BS flag in Dr6. but it appears that Windows
# isnt properly propagating that flag down to us.
if self.context.Dr6 & 0x1 and self.hardware_breakpoints.has_key(0):
slot = 0
elif self.context.Dr6 & 0x2 and self.hardware_breakpoints.has_key(1):
slot = 1
elif self.context.Dr6 & 0x4 and self.hardware_breakpoints.has_key(2):
slot = 2
elif self.context.Dr6 & 0x8 and self.hardware_breakpoints.has_key(3):
slot = 3
else:
# This wasn't an INT1 genereated by a hw breakpoint.
continue_status = DBG_EXCEPTION_NOT_HANDLED
# Now let's remove breakpoint from the list
if self.bp_del_hw(slot):
continue_status = DBG_CONTINUE
print "[*] hardware brekpoint removed."
return continue_status
def bp_del_hw(self, slot):
# Disable the breakpoint for all active threads
for thread_id in self.enumerate_threads():
context = self.get_thread_context(thread_id=thread_id)
# Reset the flags to remove the breakpoint
context.Dr7 &= ~(1 << (slot * 2))
# Zero out the address
if slot == 0:
context.Dr0 = 0x00000000
elif slot == 1:
context.Dr1 = 0x00000000
elif slot == 2:
context.Dr2 = 0x00000000
elif slot == 3:
context.Dr3 = 0x00000000
# Remove the condition flag
context.Dr7 &= ~(3 << ((slot * 4) + 16))
# Remove the length flag
context.Dr7 &= ~(3 << ((slot * 4) + 18))
# Reset the thread's context with the breakpoint removed
h_thread = self.open_thread(thread_id)
kernel32.SetThreadContext(h_thread, byref(context))
# remove the breakpoint from the internal list.
del self.hardware_breakpoints[slot]
return True
def bp_set_mem(self, address, size):
mbi = MEMORY_BASIC_INFORMATION()
# if out VirtualQueryEx() call doesnt return,
# then, a full-sized MEMORY_BASIC_INFOMATION return False
if kernel32.VirtualQueryEx(self.h_process,
address,
byref(mbi),
sizeof(mbi)) < sizeof(mbi):
return False
current_page = mbi.BaseAddress
# we will set permissions on all pages that are
# affected by our memory_breakpoint
while current_page <= address + size:
# Add the page to the list; this will
# diffrentiated our gurded pages from those
# that were set by the OS or the debuggee process
self.guarded_pages.append(current_page)
old_protection = c_ulong(0)
if not kernel32.VirtualProtectEx(self.h_process,
current_page,
size,
mbi.Protect | PAGE_GUARD,
byref(old_protection)):
return False
# add size of default page to current_page size
current_page += self.page_size
# add memory breakpoint to global dictionary
self.memory_breakpoints[address] = (size, mbi)
return True