mirror of
https://github.com/freedombox/FreedomBox.git
synced 2026-02-04 08:13:38 +00:00
85c6b91fbc
- Move render_tabs into plinth.views - Move admin_tabs and user_tabs into the class - New interproc module contains inter-process functions - New helper methods in TabMixin
107 lines
3.3 KiB
Python
107 lines
3.3 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-or-later
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import contextlib
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import fcntl
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import logging
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import os
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import pwd
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import re
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import subprocess
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import threading
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from . import interproc
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lock_name_pattern = re.compile('^[0-9a-zA-Z_-]+$')
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logger = logging.getLogger(__name__)
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class RaceCondition(AssertionError):
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pass
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class Mutex:
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"""File and pthread lock based resource mutex"""
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def __init__(self, lock_name):
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if not lock_name_pattern.match(lock_name):
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raise ValueError('Bad lock name')
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self._lock_path = '/var/lock/plinth-%s.lock' % lock_name
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self._thread_mutex = threading.Lock()
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@property
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def lock_path(self):
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return self._lock_path
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@contextlib.contextmanager
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def lock_threads_only(self):
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"""Acquire the thread lock but not the file lock"""
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if not self._thread_mutex.acquire(timeout=5):
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raise RuntimeError('Could not acquire thread lock')
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try:
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yield
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finally:
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self._thread_mutex.release()
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@contextlib.contextmanager
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def lock_all(self):
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"""Acquire both the thread lock and the file lock"""
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with self.lock_threads_only():
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# Set up
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fd = self._open_lock_file()
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fcntl.lockf(fd, fcntl.LOCK_EX)
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# Enter context
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try:
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yield
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finally:
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# Clean up
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fcntl.lockf(fd, fcntl.LOCK_UN)
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fd.close()
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def _open_lock_file(self):
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"""Attempt to open lock file for R&W. Raises OSError on failure"""
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og_ruid, og_euid, og_suid = os.getresuid()
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if og_euid == 0 and threading.active_count() > 1:
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raise RaceCondition('setuid in a multi-threaded process')
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if not os.path.exists(self.lock_path):
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self._create_lock_file_as_plinth(og_euid)
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fd = None
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try:
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if og_euid == 0:
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# Temporarily run the current process as plinth
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plinth_uid = pwd.getpwnam('plinth').pw_uid
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self._checked_setresuid(og_ruid, plinth_uid, 0)
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fd = open(self.lock_path, 'w+b')
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finally:
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# Restore resuid
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if og_euid == 0:
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self._checked_setresuid(og_ruid, 0, 0)
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if og_suid != 0:
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self._checked_setresuid(og_ruid, 0, og_suid)
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return fd
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def _create_lock_file_as_plinth(self, your_euid):
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# Don't change the current processes umask
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# Do create a new process
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args = []
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if your_euid == 0:
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args.extend(['sudo', '-n', '-u', 'plinth'])
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args.extend(['/bin/sh', '-c'])
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args.append('umask 177 && > ' + self.lock_path)
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completed = subprocess.run(args, capture_output=True)
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if completed.returncode != 0:
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interproc.log_subprocess(completed)
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raise OSError('Could not create ' + self.lock_path)
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def _checked_setresuid(self, ruid, euid, suid):
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os.setresuid(ruid, euid, suid)
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if os.getresuid() != (ruid, euid, suid):
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try:
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raise SystemExit('PANIC: setresuid failed')
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except SystemExit as e:
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# Print stack trace
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logger.exception(e)
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# Force exit
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exit(1)
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