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356 lines
13 KiB
Python
356 lines
13 KiB
Python
"""
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Abstract class for cross-platform memory editing.
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"""
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from typing import List, Tuple, Optional, Union, Generator
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from abc import ABCMeta, abstractmethod
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from contextlib import contextmanager
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import copy
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import ctypes
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import logging
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from . import utils
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from .utils import ctypes_buffer_t
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logger = logging.getLogger(__name__)
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class Process(metaclass=ABCMeta):
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"""
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This class is used to interact with processes running on the system
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(i.e., by reading from or writing to the memory used by a given process).
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The static methods
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`Process.list_available_pids()`
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`Process.get_pid_by_name(executable_filename)`
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can be used to help find the process id (pid) of the target process. They are
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provided for convenience only; it is probably better to use the tools built
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in to your operating system to discover the pid of the specific process you
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would like to edit.
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Once you have found the pid, you are ready to construct an instance of Process
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and use it to read and write to memory. Once you are done with the process,
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use `.close()` to free up the process for access by other debuggers etc.
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```
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p = Process(1239)
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p.close()
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```
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To read/write to memory, first create a buffer using ctypes:
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```
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buffer0 = (ctypes.c_byte * 5)(39, 50, 03, 40, 30)
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buffer1 = ctypes.c_ulong()
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```
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and then use
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```
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p.write_memory(0x2fe, buffer0)
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val0 = p.read_memory(0x220, buffer0)[:]
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val1a = p.read_memory(0x149, buffer1).value
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val2b = buffer1.value
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assert(val1a == val2b)
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```
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Searching for a value can be done in a number of ways:
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Search a list of addresses:
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`found_addresses = p.search_addresses([0x1020, 0x1030], buffer0)`
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Search the entire memory space:
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`found_addresses = p.search_all_memory(buffer0, writeable_only=False)`
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You can also get a list of which regions in memory are mapped (readable):
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`regions = p.list_mapped_regions(writeable_only=False)`
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which can be used along with search_buffer(...) to re-create .search_all_memory(...):
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```
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found = []
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for region_start, region_stop in regions:
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region_buffer = (ctypes.c_byte * (region_stop - region_start))()
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p.read_memory(region_start, region_buffer)
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found += utils.search_buffer(ctypes.c_ulong(123456790), region_buffer)
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```
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Other useful methods include the context manager, implemented as a static method:
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```
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with Process.open_process(pid) as p:
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# use p here, no need to call p.close()
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```
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.get_path(), which reports the path of the executable file which was used
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to start the process:
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```
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executable_path = p.get_path()
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```
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and deref_struct_pointer, which takes a pointer to a struct and reads out the struct members:
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```
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# struct is a list of (offset, buffer) pairs
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struct_defintion = [(0x0, ctypes.c_ulong()),
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(0x20, ctypes.c_byte())]
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values = p.deref_struct_pointer(0x0feab4, struct_defintion)
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```
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which is shorthand for
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```
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struct_addr = p.read_memory(0x0feab4, ctypes.c_void_p())
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values = [p.read_memory(struct_addr + 0x0, ctypes.c_ulong()),
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p.read_memory(struct_addr + 0x20, ctypes.c_byte())]
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```
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=================
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Putting all this together, a simple program which alters a magic number in the only running
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instance of 'magic.exe' might look like this:
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```
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import ctypes
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from mem_edit import Process
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magic_number = ctypes.ulong(1234567890)
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pid = Process.get_pid_by_name('magic.exe')
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with Process.open_process(pid) as p:
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addrs = p.search_all_memory(magic_number)
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assert(len(addrs) == 1)
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p.write_memory(addrs[0], ctypes.c_ulong(42))
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```
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Searching for a value which changes:
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```
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pid = Process.get_pid_by_name('monitor_me.exe')
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with Process.open_process(pid) as p:
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addrs = p.search_all_memory(ctypes.c_int(40))
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input('Press enter when value has changed to 55')
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filtered_addrs = p.search_addresses(addrs, ctypes.c_int(55))
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print('Found addresses:')
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for addr in filtered_addrs:
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print(hex(addr))
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```
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"""
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@abstractmethod
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def __init__(self, process_id: int):
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"""
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Constructing a Process object prepares the process with specified process_id for
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memory editing. Finding the `process_id` for the process you want to edit is often
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easiest using os-specific tools (or by launching the process yourself, e.g. with
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`subprocess.Popen(...)`).
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Args:
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process_id: Process id (pid) of the target process
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"""
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pass
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@abstractmethod
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def close(self):
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"""
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Detach from the process, removing our ability to edit it and
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letting other debuggers attach to it instead.
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This function should be called after you are done working with the process
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and will no longer need it. See the `Process.open_process(...)` context
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manager to avoid having to call this function yourself.
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"""
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pass
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@abstractmethod
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def write_memory(self, base_address: int, write_buffer: ctypes_buffer_t):
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"""
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Write the given buffer to the process's address space, starting at `base_address`.
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Args:
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base_address: The address to write at, in the process's address space.
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write_buffer: A ctypes object, for example, `ctypes.c_ulong(48)`,
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`(ctypes.c_byte * 3)(43, 21, 0xff)`, or a subclass of `ctypes.Structure`,
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which will be written into memory starting at `base_address`.
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"""
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pass
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@abstractmethod
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def read_memory(self, base_address: int, read_buffer: ctypes_buffer_t) -> ctypes_buffer_t:
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"""
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Read into the given buffer from the process's address space, starting at `base_address`.
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Args:
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base_address: The address to read from, in the process's address space.
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read_buffer: A `ctypes` object, for example. `ctypes.c_ulong()`,
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`(ctypes.c_byte * 3)()`, or a subclass of `ctypes.Structure`, which will be
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overwritten with the contents of the process's memory starting at `base_address`.
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Returns:
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`read_buffer` is returned as well as being overwritten.
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"""
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pass
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@abstractmethod
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def list_mapped_regions(self, writeable_only=True) -> List[Tuple[int, int]]:
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"""
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Return a list of `(start_address, stop_address)` for the regions of the address space
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accessible to (readable and possibly writable by) the process.
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By default, this function does not return non-writeable regions.
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Args:
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writeable_only: If `True`, only return regions which are also writeable.
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Default `True`.
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Returns:
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List of `(start_address, stop_address)` for each accessible memory region.
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"""
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pass
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@abstractmethod
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def get_path(self) -> str:
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"""
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Return the path to the executable file which was run to start this process.
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Returns:
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A string containing the path.
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"""
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pass
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@staticmethod
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@abstractmethod
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def list_available_pids() -> List[int]:
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"""
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Return a list of all process ids (pids) accessible on this system.
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Returns:
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List of running process ids.
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"""
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pass
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@staticmethod
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@abstractmethod
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def get_pid_by_name(target_name: str) -> Optional[int]:
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"""
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Attempt to return the process id (pid) of a process which was run with an executable
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file with the provided name. If no process is found, return None.
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This is a convenience method for quickly finding a process which is already known
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to be unique and has a well-defined executable name.
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Don't rely on this method if you can possibly avoid it, since it makes no
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attempt to confirm that it found a unique process and breaks trivially (e.g. if the
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executable file is renamed).
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Args:
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target_name: Name of the process to find the PID for
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Returns:
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Process id (pid) of a process with the provided name, or `None`.
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"""
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pass
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def deref_struct_pointer(self,
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base_address: int,
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targets: List[Tuple[int, ctypes_buffer_t]],
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) -> List[ctypes_buffer_t]:
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"""
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Take a pointer to a struct and read out the struct members:
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```
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struct_defintion = [(0x0, ctypes.c_ulong()),
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(0x20, ctypes.c_byte())]
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values = p.deref_struct_pointer(0x0feab4, struct_defintion)
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```
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which is shorthand for
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```
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struct_addr = p.read_memory(0x0feab4, ctypes.c_void_p())
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values = [p.read_memory(struct_addr + 0x0, ctypes.c_ulong()),
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p.read_memory(struct_addr + 0x20, ctypes.c_byte())]
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```
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Args:
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base_address: Address at which the struct pointer is located.
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targets: List of `(offset, read_buffer)` pairs which will be read from the struct.
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Return:
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List of read values corresponding to the provided targets.
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"""
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base = self.read_memory(base_address, ctypes.c_void_p()).value
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values = [self.read_memory(base + offset, buffer) for offset, buffer in targets]
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return values
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def search_addresses(self,
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addresses: List[int],
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needle_buffer: ctypes_buffer_t,
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verbatim: bool = True,
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) -> List[int]:
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"""
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Search for the provided value at each of the provided addresses, and return the addresses
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where it is found.
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Args:
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addresses: List of addresses which should be probed.
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needle_buffer: The value to search for. This should be a `ctypes` object of the same
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sorts as used by `.read_memory(...)`, which will be compared to the contents of
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memory at each of the given addresses.
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verbatim: If `True`, perform bitwise comparison when searching for `needle_buffer`.
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If `False`, perform `utils.ctypes_equal`-based comparison. Default `True`.
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Returns:
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List of addresses where the `needle_buffer` was found.
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"""
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found = []
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read_buffer = copy.copy(needle_buffer)
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if verbatim:
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def compare(a, b):
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return bytes(read_buffer) == bytes(needle_buffer)
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else:
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compare = utils.ctypes_equal
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for address in addresses:
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self.read_memory(address, read_buffer)
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if compare(needle_buffer, read_buffer):
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found.append(address)
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return found
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def search_all_memory(self,
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needle_buffer: ctypes_buffer_t,
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writeable_only: bool = True,
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verbatim: bool = True,
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) -> List[int]:
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"""
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Search the entire memory space accessible to the process for the provided value.
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Args:
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needle_buffer: The value to search for. This should be a ctypes object of the same
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sorts as used by `.read_memory(...)`, which will be compared to the contents of
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memory at each accessible address.
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writeable_only: If `True`, only search regions where the process has write access.
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Default `True`.
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verbatim: If `True`, perform bitwise comparison when searching for `needle_buffer`.
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If `False`, perform `utils.ctypes_equal-based` comparison. Default `True`.
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Returns:
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List of addresses where the `needle_buffer` was found.
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"""
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found = []
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if verbatim:
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search = utils.search_buffer_verbatim
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else:
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search = utils.search_buffer
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for start, stop in self.list_mapped_regions(writeable_only):
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try:
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region_buffer = (ctypes.c_byte * (stop - start))()
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self.read_memory(start, region_buffer)
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found += [offset + start for offset in search(needle_buffer, region_buffer)]
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except OSError:
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logger.error('Failed to read in range 0x{} - 0x{}'.format(start, stop))
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return found
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@classmethod
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@contextmanager
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def open_process(cls, process_id: int) -> Generator['Process', None, None]:
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"""
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Context manager which automatically closes the constructed Process:
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```
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with Process.open_process(2394) as p:
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# use p here
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# no need to run p.close()
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```
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Args:
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process_id: Process id (pid), passed to the Process constructor.
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Returns:
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Constructed Process object.
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"""
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process = cls(process_id)
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yield process
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process.close()
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