mirror of
https://github.com/freedombox/FreedomBox.git
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279738c305
- These situation occur when server encounters an error when trying to formulate a response. All exceptions during execution of actions are caught and reported properly. However, server may encounter errors during processing of exception raised in an action. Or may die abruptly. This special error will make identifying such situations easier. Tests: - Add a 'return' after _read_request() in privileged_daemon.py:RequestHandler:handle(). This will trigger this error. Starting FreedomBox service will show these errors as 'ConnectionError: Server returned empty response'. Similarly running 'freedombox-cmd --no-args plinth is_package_manager_busy' will show the same error. Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org> Reviewed-by: Veiko Aasa <veiko17@disroot.org>
617 lines
21 KiB
Python
617 lines
21 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-or-later
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"""Framework to run specified actions with elevated privileges."""
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import functools
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import importlib
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import inspect
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import io
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import json
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import logging
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import pathlib
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import socket
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import threading
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import traceback
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import types
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import typing
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from plinth import cfg, module_loader
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logger = logging.getLogger(__name__)
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socket_path = '/run/freedombox/privileged.socket'
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thread_storage = threading.local()
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# An alias for 'str' to mark some strings as sensitive. Sensitive strings are
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# not logged. Use 'type secret_str = str' when Python 3.11 support is no longer
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# needed.
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class secret_str(str):
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pass
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def privileged(func):
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"""Mark a method as allowed to be run as privileged method.
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This decorator is to mark any method as needing to be executed with
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superuser privileges. This is necessary because the primary FreedomBox
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service daemon runs as a regular user and has no special privileges. When
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performing system operations, FreedomBox service will either communicate
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with privileged daemons such as NetworkManager and systemd, or spawns a
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separate process with higher privileges. When spawning a separate process
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all the action parameters need to serialized, communicated to the process
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and then de-serialized inside the process. The return value also need to
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undergo such serialization and de-serialization. This decorator makes this
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task simpler.
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A call to a decorated method will be serialized into a sudo call (or later
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into a D-Bus call). The method arguments are turned to JSON and method is
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called with superuser privileges. As arguments are de-serialized, they are
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verified for type before the actual call as superuser. Return values are
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serialized and returned where they are de-serialized. Exceptions are also
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serialized and de-serialized. The decorator wrapper code will either return
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the value or raise exception.
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For a method to be decorated, the method must have type annotations for all
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of its parameters and should not use keyword-only arguments. It must also
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be in a module named privileged.py directly under the application similar
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to models.py, views.py and urls.py. Currently supported types are bool,
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int, float, str, dict/Dict, list/List, Optional and Union.
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Privileged methods many not output to the stdout as it interferes
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with the serialization and de-serialization process.
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"""
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setattr(func, '_privileged', True)
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_check_privileged_action_arguments(func)
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@functools.wraps(func)
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def wrapper(*args, **kwargs):
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if getattr(func, '_skip_privileged_call', False):
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return func(*args, **kwargs)
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module_name = _get_privileged_action_module_name(func)
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action_name = func.__name__
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return run_privileged_method(func, module_name, action_name, args,
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kwargs)
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return wrapper
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def _read_from_server(client_socket: socket.socket) -> bytes:
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"""Read everything from a socket and return the data."""
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response = b''
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while True:
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chunk = client_socket.recv(4096)
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if not chunk:
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break
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response += chunk
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if not response:
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raise ConnectionError('Server returned empty response')
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return json.loads(response)
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def _request_to_server(request: dict) -> socket.socket:
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"""Connect to the server and make a request."""
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request_string = json.dumps(request)
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client_socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
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try:
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client_socket.connect(socket_path)
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client_socket.sendall(request_string.encode('utf-8'))
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# Close the write end of the socket signaling an EOF and no more data
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# will be sent.
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client_socket.shutdown(socket.SHUT_WR)
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except Exception:
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client_socket.close()
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raise
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return client_socket
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def run_privileged_method(func, module_name, action_name, args, kwargs):
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"""Execute a privileged method using a server."""
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run_in_background = kwargs.pop('_run_in_background', False)
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raw_output = kwargs.pop('_raw_output', False)
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log_error = kwargs.pop('_log_error', True)
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if func:
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_log_action(func, module_name, action_name, args, kwargs,
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run_in_background)
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request = {
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'module': module_name,
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'action': action_name,
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'args': args,
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'kwargs': kwargs,
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}
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if raw_output:
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request['raw_output'] = raw_output
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client_socket = _request_to_server(request)
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if raw_output:
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def _reader_func():
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while True:
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chunk = client_socket.recv(4096)
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if chunk:
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yield chunk
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else:
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break
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client_socket.close()
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return _reader_func()
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args = (func, module_name, action_name, args, kwargs, log_error,
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client_socket)
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if not run_in_background:
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return _wait_for_server_response(*args)
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read_thread = threading.Thread(target=_wait_for_server_response, args=args)
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read_thread.start()
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def _wait_for_server_response(func, module_name, action_name, args, kwargs,
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log_error, client_socket):
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"""Wait for the server to respond and process the response."""
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try:
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return_value = _read_from_server(client_socket)
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except json.JSONDecodeError:
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logger.error('Error decoding action return value %s..%s(*%s, **%s)',
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module_name, action_name, args, kwargs)
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raise
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finally:
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client_socket.close()
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if return_value['result'] == 'success':
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return return_value['return']
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module = importlib.import_module(return_value['exception']['module'])
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exception_class = getattr(module, return_value['exception']['name'])
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exception = exception_class(*return_value['exception']['args'])
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exception.stdout = return_value['exception'].get('stdout', b'').encode()
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exception.stderr = return_value['exception'].get('stderr', b'').encode()
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def _get_html_message():
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"""Return an HTML format error that can be shown in messages."""
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from django.utils.html import format_html
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formatted_args = _format_args(func, args, kwargs)
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exception_args, stdout, stderr, traceback = _format_error(
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exception, return_value)
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return format_html('Error running action: {}..{}({}): {}({})\n{}{}{}',
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module_name, action_name, formatted_args,
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return_value['exception']['name'], exception_args,
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stdout, stderr, traceback)
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if func:
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exception.get_html_message = _get_html_message
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if log_error and func:
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formatted_args = _format_args(func, args, kwargs)
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exception_args, stdout, stderr, traceback = _format_error(
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exception, return_value)
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logger.error('Error running action %s..%s(%s): %s(%s)\n'
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'%s%s%s', module_name, action_name, formatted_args,
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return_value['exception']['name'], exception_args, stdout,
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stderr, traceback)
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raise exception
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class ProcessBufferedReader(io.BufferedReader):
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"""Improve performance of buffered binary streaming.
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Read from the stdout of a process and close the process after reading is
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completed.
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Iteration calls __next__ over the BufferedReader holding process.stdout.
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However, this seems to call readline() which looks for \n in binary data
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which leads to short unpredictably sized chunks which in turn lead to
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severe performance degradation. So, overwrite this and call read() which is
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better geared for handling binary data.
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"""
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def __init__(self, process, extra_cleanup_func=None, *args, **kwargs):
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"""Store the process object."""
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super().__init__(process.stdout, *args, **kwargs)
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self.process = process
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self.extra_cleanup_func = extra_cleanup_func
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def __next__(self):
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"""Override to call read() instead of readline()."""
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chunk = self.read(io.DEFAULT_BUFFER_SIZE)
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if not chunk:
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self._cleanup_func()
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raise StopIteration
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return chunk
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def _cleanup_func(self):
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"""After the process has been read from, cleanup the process."""
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try:
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if self.process.stdout:
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self.process.stdout.close()
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if self.process.stderr:
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self.process.stderr.close()
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self.process.wait(30)
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if self.extra_cleanup_func:
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self.extra_cleanup_func()
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except Exception:
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logger.exception('Closing process failed after raw output')
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def _format_args(func, args, kwargs):
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"""Return a loggable representation of arguments."""
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argspec = inspect.getfullargspec(func)
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if len(args) > len(argspec.args):
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raise SyntaxError('Too many arguments')
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args_str_list = []
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for arg_index, arg_value in enumerate(args):
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arg_name = argspec.args[arg_index]
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if argspec.annotations[arg_name] in [secret_str, secret_str | None]:
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value = '****'
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else:
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value = json.dumps(arg_value)
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args_str_list.append(value)
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kwargs_str_list = []
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for arg_name, arg_value in kwargs.items():
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if argspec.annotations[arg_name] in [secret_str, secret_str | None]:
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value = "****"
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else:
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value = json.dumps(arg_value)
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kwargs_str_list.append(f'{arg_name}=' + value)
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return ', '.join(args_str_list + kwargs_str_list)
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def _format_error(exception, return_value):
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"""Log the exception in a readable manner."""
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exception_args = ', '.join([json.dumps(arg) for arg in exception.args])
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stdout = exception.stdout.decode()
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if stdout:
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lines = stdout.split('\n')
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lines = lines[:-1] if not lines[-1] else lines
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stdout = '\n'.join(('│ ' + line for line in lines))
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stdout = 'Stdout:\n' + stdout + '\n'
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stderr = exception.stderr.decode()
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if stderr:
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lines = stderr.split('\n')
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lines = lines[:-1] if not lines[-1] else lines
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stderr = '\n'.join(('║ ' + line for line in lines))
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stderr = 'Stderr:\n' + stderr + '\n'
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traceback = return_value['exception']['traceback']
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if traceback:
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all_lines = []
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for entry in traceback:
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lines = entry.split('\n')
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all_lines += lines[:-1] if not lines[-1] else lines
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traceback = '\n'.join(('╞ ' + line for line in all_lines))
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traceback = 'Action traceback:\n' + traceback + '\n'
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return (exception_args, stdout, stderr, traceback)
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def _check_privileged_action_arguments(func):
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"""Check that a privileged action has well defined types."""
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argspec = inspect.getfullargspec(func)
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if (argspec.varargs or argspec.varkw or argspec.kwonlyargs
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or argspec.kwonlydefaults):
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raise SyntaxError('Actions must not have variable args')
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for arg in argspec.args:
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if arg not in argspec.annotations:
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raise SyntaxError('All arguments must be annotated')
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for arg_name, arg_value in argspec.annotations.items():
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for keyword in ('password', 'passphrase', 'secret'):
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if keyword in arg_name:
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if arg_value not in [secret_str, secret_str | None]:
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raise SyntaxError(
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f'Argument {arg_name} should likely be a "secret_str"')
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def _get_privileged_action_module_name(func):
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"""Figure out the module name of a privileged action."""
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module_name = func.__module__
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while module_name:
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module_name, _, last = module_name.rpartition('.')
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if last == 'privileged':
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break
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if not module_name:
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raise ValueError('Privileged actions must be placed under a '
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'package/module named privileged')
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return module_name.rpartition('.')[2]
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def _log_action(func, module_name, action_name, args, kwargs,
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run_in_background):
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"""Log an action in a compact format."""
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prompt = '»'
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suffix = '&' if run_in_background else ''
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formatted_args = _format_args(func, args, kwargs)
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logger.info('%s %s..%s(%s) %s', prompt, module_name, action_name,
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formatted_args, suffix)
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class JSONEncoder(json.JSONEncoder):
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"""Handle to special types that default JSON encoder does not."""
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def default(self, obj):
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"""Handle special object types."""
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# When subprocess.call() fails and one of the arguments is a Path-like
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# object, the exception also contains a Path-like object.
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if isinstance(obj, pathlib.Path):
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return str(obj)
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return super().default(obj)
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def _setup_thread_storage():
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"""Setup collection of stdout/stderr from any process in this thread."""
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global thread_storage
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thread_storage.stdout = b''
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thread_storage.stderr = b''
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def _clear_thread_storage():
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"""Cleanup memory used for stdout/stderr from processes in this thread.
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Python documentation is silent on whether thread local storage will be
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cleaned up after a thread terminates.
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"""
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global thread_storage
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thread_storage.stdout = None
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thread_storage.stderr = None
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def get_return_value_from_exception(exception):
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"""Return the value to return from server when an exception is raised."""
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global thread_storage
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return_value = {
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'result': 'exception',
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'exception': {
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'module': type(exception).__module__,
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'name': type(exception).__name__,
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'args': exception.args,
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'traceback': traceback.format_tb(exception.__traceback__),
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'stdout': getattr(thread_storage, 'stdout', b'').decode(),
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'stderr': getattr(thread_storage, 'stderr', b'').decode(),
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}
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}
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return return_value
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def privileged_handle_json_request(
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request_string: str) -> str | io.BufferedReader:
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"""Parse arguments for the program spawned as a privileged action."""
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def _parse_request() -> dict:
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"""Return a JSON parsed and validated request."""
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try:
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request = json.loads(request_string)
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except json.JSONDecodeError:
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raise SyntaxError('Invalid JSON in request')
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required_parameters = [('module', str), ('action', str),
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('args', list), ('kwargs', dict)]
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for parameter, expected_type in required_parameters:
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if parameter not in request:
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raise TypeError(f'Missing required parameter "{parameter}"')
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if not isinstance(request[parameter], expected_type):
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raise TypeError(f'Parameter "{parameter}" must be of type'
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f'{expected_type.__name__}')
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if 'raw_output' in request and not isinstance(request['raw_output'],
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bool):
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raise TypeError('Incorrect "raw_output" parameter')
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return request
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try:
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request = _parse_request()
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arguments = {'args': request['args'], 'kwargs': request['kwargs']}
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_setup_thread_storage()
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return_value = _privileged_call(request['module'], request['action'],
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arguments)
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if isinstance(return_value, io.BufferedReader):
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raw_output = request.get('raw_output', False)
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if not raw_output:
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raise TypeError('Invalid call to raw output API.')
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return return_value
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except (PermissionError, SyntaxError, TypeError, Exception) as exception:
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if isinstance(exception, (PermissionError, SyntaxError, TypeError)):
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logger.error(exception.args[0])
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else:
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logger.exception(exception)
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return_value = get_return_value_from_exception(exception)
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_clear_thread_storage()
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return json.dumps(return_value, cls=JSONEncoder)
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def _privileged_call(module_name, action_name, arguments):
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"""Import the module and run action as superuser"""
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if '.' in module_name:
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raise SyntaxError('Invalid module name')
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cfg.read()
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if module_name == 'plinth':
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import_path = 'plinth'
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else:
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try:
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import_path = module_loader.get_module_import_path(module_name)
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except FileNotFoundError as exception:
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raise SyntaxError('Specified module not found') from exception
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try:
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module = importlib.import_module(import_path + '.privileged')
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except ModuleNotFoundError as exception:
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raise SyntaxError('Specified module not found') from exception
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try:
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action = getattr(module, action_name)
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except AttributeError as exception:
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raise SyntaxError('Specified action not found') from exception
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if not getattr(action, '_privileged', None):
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raise SyntaxError('Specified action is not privileged action')
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# Get the original function that may have been wrapped/decorated multiple
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# times
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func = action
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while True:
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try:
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func = getattr(func, '__wrapped__')
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except AttributeError:
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break
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_privileged_assert_valid_arguments(func, arguments)
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_log_action(func, module_name, action_name, arguments['args'],
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arguments['kwargs'], run_in_background=False)
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try:
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return_values = func(*arguments['args'], **arguments['kwargs'])
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if isinstance(return_values, io.BufferedReader):
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return return_values
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return_value = {'result': 'success', 'return': return_values}
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except Exception as exception:
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return_value = get_return_value_from_exception(exception)
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logger.exception(
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'Error running action: %s..%s(..): %s\nstdout:\n%s\nstderr:\n%s\n',
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module_name, action_name, exception,
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return_value['exception']['stdout'],
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return_value['exception']['stderr'])
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return return_value
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def _privileged_assert_valid_arguments(func, arguments):
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"""Check the names, types and completeness of the arguments passed."""
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# Check if arguments match types
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if not isinstance(arguments, dict):
|
|
raise SyntaxError('Invalid arguments format')
|
|
|
|
if 'args' not in arguments or 'kwargs' not in arguments:
|
|
raise SyntaxError('Invalid arguments format')
|
|
|
|
args = arguments['args']
|
|
kwargs = arguments['kwargs']
|
|
if not isinstance(args, list) or not isinstance(kwargs, dict):
|
|
raise SyntaxError('Invalid arguments format')
|
|
|
|
argspec = inspect.getfullargspec(func)
|
|
if len(args) + len(kwargs) > len(argspec.args):
|
|
raise SyntaxError('Too many arguments')
|
|
|
|
no_defaults = len(argspec.args)
|
|
if argspec.defaults:
|
|
no_defaults -= len(argspec.defaults)
|
|
|
|
for key in argspec.args[len(args):no_defaults]:
|
|
if key not in kwargs:
|
|
raise SyntaxError(f'Argument not provided: {key}')
|
|
|
|
for key, value in kwargs.items():
|
|
if key not in argspec.args:
|
|
raise SyntaxError(f'Unknown argument: {key}')
|
|
|
|
if argspec.args.index(key) < len(args):
|
|
raise SyntaxError(f'Duplicate argument: {key}')
|
|
|
|
_privileged_assert_valid_type(f'arg {key}', value,
|
|
argspec.annotations[key])
|
|
|
|
for index, arg in enumerate(args):
|
|
annotation = argspec.annotations[argspec.args[index]]
|
|
_privileged_assert_valid_type(f'arg #{index}', arg, annotation)
|
|
|
|
|
|
def _privileged_assert_valid_type(arg_name, value, annotation):
|
|
"""Assert that the type of argument value matches the annotation."""
|
|
if annotation == typing.Any:
|
|
return
|
|
|
|
NoneType = type(None)
|
|
if annotation == NoneType:
|
|
if value is not None:
|
|
raise TypeError('Expected None for {arg_name}')
|
|
|
|
return
|
|
|
|
basic_types = {bool, int, str, float}
|
|
if annotation in basic_types:
|
|
if not isinstance(value, annotation):
|
|
raise TypeError(
|
|
f'Expected type {annotation.__name__} for {arg_name}')
|
|
|
|
return
|
|
|
|
# secret_str should be a regular string
|
|
if annotation == secret_str:
|
|
if not isinstance(value, str):
|
|
raise TypeError(f'Expected type str for {arg_name}')
|
|
|
|
return
|
|
|
|
# 'int | str' or 'typing.Union[int, str]'
|
|
if (isinstance(annotation, types.UnionType)
|
|
or getattr(annotation, '__origin__', None) == typing.Union):
|
|
for arg in annotation.__args__:
|
|
try:
|
|
_privileged_assert_valid_type(arg_name, value, arg)
|
|
return
|
|
except TypeError:
|
|
pass
|
|
|
|
raise TypeError(f'Expected one of unioned types for {arg_name}')
|
|
|
|
# 'list[int]' or 'typing.List[int]'
|
|
if getattr(annotation, '__origin__', None) == list:
|
|
if not isinstance(value, list):
|
|
raise TypeError(f'Expected type list for {arg_name}')
|
|
|
|
for index, inner_item in enumerate(value):
|
|
_privileged_assert_valid_type(f'{arg_name}[{index}]', inner_item,
|
|
annotation.__args__[0])
|
|
|
|
return
|
|
|
|
# 'list[dict]' or 'typing.List[dict]'
|
|
if getattr(annotation, '__origin__', None) == dict:
|
|
if not isinstance(value, dict):
|
|
raise TypeError(f'Expected type dict for {arg_name}')
|
|
|
|
for inner_key, inner_value in value.items():
|
|
_privileged_assert_valid_type(f'{arg_name}[{inner_key}]',
|
|
inner_key, annotation.__args__[0])
|
|
_privileged_assert_valid_type(f'{arg_name}[{inner_value}]',
|
|
inner_value, annotation.__args__[1])
|
|
|
|
return
|
|
|
|
raise TypeError('Unsupported annotation type')
|