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Diffstat (limited to 'pkg/osx/daemon.py')
| -rw-r--r-- | pkg/osx/daemon.py | 926 |
1 files changed, 926 insertions, 0 deletions
diff --git a/pkg/osx/daemon.py b/pkg/osx/daemon.py new file mode 100644 index 00000000..07810cf1 --- /dev/null +++ b/pkg/osx/daemon.py @@ -0,0 +1,926 @@ +# -*- coding: utf-8 -*- + +# daemon/daemon.py +# Part of ‘python-daemon’, an implementation of PEP 3143. +# +# Copyright © 2008–2015 Ben Finney <ben+python@benfinney.id.au> +# Copyright © 2007–2008 Robert Niederreiter, Jens Klein +# Copyright © 2004–2005 Chad J. Schroeder +# Copyright © 2003 Clark Evans +# Copyright © 2002 Noah Spurrier +# Copyright © 2001 Jürgen Hermann +# +# This is free software: you may copy, modify, and/or distribute this work +# under the terms of the Apache License, version 2.0 as published by the +# Apache Software Foundation. +# No warranty expressed or implied. See the file ‘LICENSE.ASF-2’ for details. + +""" Daemon process behaviour. + """ + +from __future__ import (absolute_import, unicode_literals) + +import os +import sys +import resource +import errno +import signal +import socket +import atexit +try: + # Python 2 has both ‘str’ (bytes) and ‘unicode’ (text). + basestring = basestring + unicode = unicode +except NameError: + # Python 3 names the Unicode data type ‘str’. + basestring = str + unicode = str + + +class DaemonError(Exception): + """ Base exception class for errors from this module. """ + + def __init__(self, *args, **kwargs): + self._chain_from_context() + + super(DaemonError, self).__init__(*args, **kwargs) + + def _chain_from_context(self): + _chain_exception_from_existing_exception_context(self, as_cause=True) + + +class DaemonOSEnvironmentError(DaemonError, OSError): + """ Exception raised when daemon OS environment setup receives error. """ + + +class DaemonProcessDetachError(DaemonError, OSError): + """ Exception raised when process detach fails. """ + + +class DaemonContext: + """ Context for turning the current program into a daemon process. + + A `DaemonContext` instance represents the behaviour settings and + process context for the program when it becomes a daemon. The + behaviour and environment is customised by setting options on the + instance, before calling the `open` method. + + Each option can be passed as a keyword argument to the `DaemonContext` + constructor, or subsequently altered by assigning to an attribute on + the instance at any time prior to calling `open`. That is, for + options named `wibble` and `wubble`, the following invocation:: + + foo = daemon.DaemonContext(wibble=bar, wubble=baz) + foo.open() + + is equivalent to:: + + foo = daemon.DaemonContext() + foo.wibble = bar + foo.wubble = baz + foo.open() + + The following options are defined. + + `files_preserve` + :Default: ``None`` + + List of files that should *not* be closed when starting the + daemon. If ``None``, all open file descriptors will be closed. + + Elements of the list are file descriptors (as returned by a file + object's `fileno()` method) or Python `file` objects. Each + specifies a file that is not to be closed during daemon start. + + `chroot_directory` + :Default: ``None`` + + Full path to a directory to set as the effective root directory of + the process. If ``None``, specifies that the root directory is not + to be changed. + + `working_directory` + :Default: ``'/'`` + + Full path of the working directory to which the process should + change on daemon start. + + Since a filesystem cannot be unmounted if a process has its + current working directory on that filesystem, this should either + be left at default or set to a directory that is a sensible “home + directory” for the daemon while it is running. + + `umask` + :Default: ``0`` + + File access creation mask (“umask”) to set for the process on + daemon start. + + A daemon should not rely on the parent process's umask value, + which is beyond its control and may prevent creating a file with + the required access mode. So when the daemon context opens, the + umask is set to an explicit known value. + + If the conventional value of 0 is too open, consider setting a + value such as 0o022, 0o027, 0o077, or another specific value. + Otherwise, ensure the daemon creates every file with an + explicit access mode for the purpose. + + `pidfile` + :Default: ``None`` + + Context manager for a PID lock file. When the daemon context opens + and closes, it enters and exits the `pidfile` context manager. + + `detach_process` + :Default: ``None`` + + If ``True``, detach the process context when opening the daemon + context; if ``False``, do not detach. + + If unspecified (``None``) during initialisation of the instance, + this will be set to ``True`` by default, and ``False`` only if + detaching the process is determined to be redundant; for example, + in the case when the process was started by `init`, by `initd`, or + by `inetd`. + + `signal_map` + :Default: system-dependent + + Mapping from operating system signals to callback actions. + + The mapping is used when the daemon context opens, and determines + the action for each signal's signal handler: + + * A value of ``None`` will ignore the signal (by setting the + signal action to ``signal.SIG_IGN``). + + * A string value will be used as the name of an attribute on the + ``DaemonContext`` instance. The attribute's value will be used + as the action for the signal handler. + + * Any other value will be used as the action for the + signal handler. See the ``signal.signal`` documentation + for details of the signal handler interface. + + The default value depends on which signals are defined on the + running system. Each item from the list below whose signal is + actually defined in the ``signal`` module will appear in the + default map: + + * ``signal.SIGTTIN``: ``None`` + + * ``signal.SIGTTOU``: ``None`` + + * ``signal.SIGTSTP``: ``None`` + + * ``signal.SIGTERM``: ``'terminate'`` + + Depending on how the program will interact with its child + processes, it may need to specify a signal map that + includes the ``signal.SIGCHLD`` signal (received when a + child process exits). See the specific operating system's + documentation for more detail on how to determine what + circumstances dictate the need for signal handlers. + + `uid` + :Default: ``os.getuid()`` + + `gid` + :Default: ``os.getgid()`` + + The user ID (“UID”) value and group ID (“GID”) value to switch + the process to on daemon start. + + The default values, the real UID and GID of the process, will + relinquish any effective privilege elevation inherited by the + process. + + `prevent_core` + :Default: ``True`` + + If true, prevents the generation of core files, in order to avoid + leaking sensitive information from daemons run as `root`. + + `stdin` + :Default: ``None`` + + `stdout` + :Default: ``None`` + + `stderr` + :Default: ``None`` + + Each of `stdin`, `stdout`, and `stderr` is a file-like object + which will be used as the new file for the standard I/O stream + `sys.stdin`, `sys.stdout`, and `sys.stderr` respectively. The file + should therefore be open, with a minimum of mode 'r' in the case + of `stdin`, and mimimum of mode 'w+' in the case of `stdout` and + `stderr`. + + If the object has a `fileno()` method that returns a file + descriptor, the corresponding file will be excluded from being + closed during daemon start (that is, it will be treated as though + it were listed in `files_preserve`). + + If ``None``, the corresponding system stream is re-bound to the + file named by `os.devnull`. + + """ + + __metaclass__ = type + + def __init__( + self, + chroot_directory=None, + working_directory="/", + umask=0, + uid=None, + gid=None, + prevent_core=True, + detach_process=None, + files_preserve=None, + pidfile=None, + stdin=None, + stdout=None, + stderr=None, + signal_map=None, + ): + """ Set up a new instance. """ + self.chroot_directory = chroot_directory + self.working_directory = working_directory + self.umask = umask + self.prevent_core = prevent_core + self.files_preserve = files_preserve + self.pidfile = pidfile + self.stdin = stdin + self.stdout = stdout + self.stderr = stderr + + if uid is None: + uid = os.getuid() + self.uid = uid + if gid is None: + gid = os.getgid() + self.gid = gid + + if detach_process is None: + detach_process = is_detach_process_context_required() + self.detach_process = detach_process + + if signal_map is None: + signal_map = make_default_signal_map() + self.signal_map = signal_map + + self._is_open = False + + @property + def is_open(self): + """ ``True`` if the instance is currently open. """ + return self._is_open + + def open(self): + """ Become a daemon process. + + :return: ``None``. + + Open the daemon context, turning the current program into a daemon + process. This performs the following steps: + + * If this instance's `is_open` property is true, return + immediately. This makes it safe to call `open` multiple times on + an instance. + + * If the `prevent_core` attribute is true, set the resource limits + for the process to prevent any core dump from the process. + + * If the `chroot_directory` attribute is not ``None``, set the + effective root directory of the process to that directory (via + `os.chroot`). + + This allows running the daemon process inside a “chroot gaol” + as a means of limiting the system's exposure to rogue behaviour + by the process. Note that the specified directory needs to + already be set up for this purpose. + + * Set the process UID and GID to the `uid` and `gid` attribute + values. + + * Close all open file descriptors. This excludes those listed in + the `files_preserve` attribute, and those that correspond to the + `stdin`, `stdout`, or `stderr` attributes. + + * Change current working directory to the path specified by the + `working_directory` attribute. + + * Reset the file access creation mask to the value specified by + the `umask` attribute. + + * If the `detach_process` option is true, detach the current + process into its own process group, and disassociate from any + controlling terminal. + + * Set signal handlers as specified by the `signal_map` attribute. + + * If any of the attributes `stdin`, `stdout`, `stderr` are not + ``None``, bind the system streams `sys.stdin`, `sys.stdout`, + and/or `sys.stderr` to the files represented by the + corresponding attributes. Where the attribute has a file + descriptor, the descriptor is duplicated (instead of re-binding + the name). + + * If the `pidfile` attribute is not ``None``, enter its context + manager. + + * Mark this instance as open (for the purpose of future `open` and + `close` calls). + + * Register the `close` method to be called during Python's exit + processing. + + When the function returns, the running program is a daemon + process. + + """ + if self.is_open: + return + + if self.chroot_directory is not None: + change_root_directory(self.chroot_directory) + + if self.prevent_core: + prevent_core_dump() + + change_file_creation_mask(self.umask) + change_working_directory(self.working_directory) + change_process_owner(self.uid, self.gid) + + if self.detach_process: + detach_process_context() + + signal_handler_map = self._make_signal_handler_map() + set_signal_handlers(signal_handler_map) + + exclude_fds = self._get_exclude_file_descriptors() + close_all_open_files(exclude=exclude_fds) + + redirect_stream(sys.stdin, self.stdin) + redirect_stream(sys.stdout, self.stdout) + redirect_stream(sys.stderr, self.stderr) + + if self.pidfile is not None: + self.pidfile.__enter__() + + self._is_open = True + + register_atexit_function(self.close) + + def __enter__(self): + """ Context manager entry point. """ + self.open() + return self + + def close(self): + """ Exit the daemon process context. + + :return: ``None``. + + Close the daemon context. This performs the following steps: + + * If this instance's `is_open` property is false, return + immediately. This makes it safe to call `close` multiple times + on an instance. + + * If the `pidfile` attribute is not ``None``, exit its context + manager. + + * Mark this instance as closed (for the purpose of future `open` + and `close` calls). + + """ + if not self.is_open: + return + + if self.pidfile is not None: + # Follow the interface for telling a context manager to exit, + # <URL:http://docs.python.org/library/stdtypes.html#typecontextmanager>. + self.pidfile.__exit__(None, None, None) + + self._is_open = False + + def __exit__(self, exc_type, exc_value, traceback): + """ Context manager exit point. """ + self.close() + + def terminate(self, signal_number, stack_frame): + """ Signal handler for end-process signals. + + :param signal_number: The OS signal number received. + :param stack_frame: The frame object at the point the + signal was received. + :return: ``None``. + + Signal handler for the ``signal.SIGTERM`` signal. Performs the + following step: + + * Raise a ``SystemExit`` exception explaining the signal. + + """ + exception = SystemExit( + "Terminating on signal {signal_number!r}".format( + signal_number=signal_number)) + raise exception + + def _get_exclude_file_descriptors(self): + """ Get the set of file descriptors to exclude closing. + + :return: A set containing the file descriptors for the + files to be preserved. + + The file descriptors to be preserved are those from the + items in `files_preserve`, and also each of `stdin`, + `stdout`, and `stderr`. For each item: + + * If the item is ``None``, it is omitted from the return + set. + + * If the item's ``fileno()`` method returns a value, that + value is in the return set. + + * Otherwise, the item is in the return set verbatim. + + """ + files_preserve = self.files_preserve + if files_preserve is None: + files_preserve = [] + files_preserve.extend( + item for item in [self.stdin, self.stdout, self.stderr] + if hasattr(item, 'fileno')) + + exclude_descriptors = set() + for item in files_preserve: + if item is None: + continue + file_descriptor = _get_file_descriptor(item) + if file_descriptor is not None: + exclude_descriptors.add(file_descriptor) + else: + exclude_descriptors.add(item) + + return exclude_descriptors + + def _make_signal_handler(self, target): + """ Make the signal handler for a specified target object. + + :param target: A specification of the target for the + handler; see below. + :return: The value for use by `signal.signal()`. + + If `target` is ``None``, return ``signal.SIG_IGN``. If `target` + is a text string, return the attribute of this instance named + by that string. Otherwise, return `target` itself. + + """ + if target is None: + result = signal.SIG_IGN + elif isinstance(target, unicode): + name = target + result = getattr(self, name) + else: + result = target + + return result + + def _make_signal_handler_map(self): + """ Make the map from signals to handlers for this instance. + + :return: The constructed signal map for this instance. + + Construct a map from signal numbers to handlers for this + context instance, suitable for passing to + `set_signal_handlers`. + + """ + signal_handler_map = dict( + (signal_number, self._make_signal_handler(target)) + for (signal_number, target) in self.signal_map.items()) + return signal_handler_map + + +def _get_file_descriptor(obj): + """ Get the file descriptor, if the object has one. + + :param obj: The object expected to be a file-like object. + :return: The file descriptor iff the file supports it; otherwise + ``None``. + + The object may be a non-file object. It may also be a + file-like object with no support for a file descriptor. In + either case, return ``None``. + + """ + file_descriptor = None + if hasattr(obj, 'fileno'): + try: + file_descriptor = obj.fileno() + except ValueError: + # The item doesn't support a file descriptor. + pass + + return file_descriptor + + +def change_working_directory(directory): + """ Change the working directory of this process. + + :param directory: The target directory path. + :return: ``None``. + + """ + try: + os.chdir(directory) + except Exception as exc: + error = DaemonOSEnvironmentError( + "Unable to change working directory ({exc})".format(exc=exc)) + raise error + + +def change_root_directory(directory): + """ Change the root directory of this process. + + :param directory: The target directory path. + :return: ``None``. + + Set the current working directory, then the process root directory, + to the specified `directory`. Requires appropriate OS privileges + for this process. + + """ + try: + os.chdir(directory) + os.chroot(directory) + except Exception as exc: + error = DaemonOSEnvironmentError( + "Unable to change root directory ({exc})".format(exc=exc)) + raise error + + +def change_file_creation_mask(mask): + """ Change the file creation mask for this process. + + :param mask: The numeric file creation mask to set. + :return: ``None``. + + """ + try: + os.umask(mask) + except Exception as exc: + error = DaemonOSEnvironmentError( + "Unable to change file creation mask ({exc})".format(exc=exc)) + raise error + + +def change_process_owner(uid, gid): + """ Change the owning UID and GID of this process. + + :param uid: The target UID for the daemon process. + :param gid: The target GID for the daemon process. + :return: ``None``. + + Set the GID then the UID of the process (in that order, to avoid + permission errors) to the specified `gid` and `uid` values. + Requires appropriate OS privileges for this process. + + """ + try: + os.setgid(gid) + os.setuid(uid) + except Exception as exc: + error = DaemonOSEnvironmentError( + "Unable to change process owner ({exc})".format(exc=exc)) + raise error + + +def prevent_core_dump(): + """ Prevent this process from generating a core dump. + + :return: ``None``. + + Set the soft and hard limits for core dump size to zero. On Unix, + this entirely prevents the process from creating core dump. + + """ + core_resource = resource.RLIMIT_CORE + + try: + # Ensure the resource limit exists on this platform, by requesting + # its current value. + core_limit_prev = resource.getrlimit(core_resource) + except ValueError as exc: + error = DaemonOSEnvironmentError( + "System does not support RLIMIT_CORE resource limit" + " ({exc})".format(exc=exc)) + raise error + + # Set hard and soft limits to zero, i.e. no core dump at all. + core_limit = (0, 0) + resource.setrlimit(core_resource, core_limit) + + +def detach_process_context(): + """ Detach the process context from parent and session. + + :return: ``None``. + + Detach from the parent process and session group, allowing the + parent to exit while this process continues running. + + Reference: “Advanced Programming in the Unix Environment”, + section 13.3, by W. Richard Stevens, published 1993 by + Addison-Wesley. + + """ + + def fork_then_exit_parent(error_message): + """ Fork a child process, then exit the parent process. + + :param error_message: Message for the exception in case of a + detach failure. + :return: ``None``. + :raise DaemonProcessDetachError: If the fork fails. + + """ + try: + pid = os.fork() + if pid > 0: + os._exit(0) + except OSError as exc: + error = DaemonProcessDetachError( + "{message}: [{exc.errno:d}] {exc.strerror}".format( + message=error_message, exc=exc)) + raise error + + fork_then_exit_parent(error_message="Failed first fork") + os.setsid() + fork_then_exit_parent(error_message="Failed second fork") + + +def is_process_started_by_init(): + """ Determine whether the current process is started by `init`. + + :return: ``True`` iff the parent process is `init`; otherwise + ``False``. + + The `init` process is the one with process ID of 1. + + """ + result = False + + init_pid = 1 + if os.getppid() == init_pid: + result = True + + return result + + +def is_socket(fd): + """ Determine whether the file descriptor is a socket. + + :param fd: The file descriptor to interrogate. + :return: ``True`` iff the file descriptor is a socket; otherwise + ``False``. + + Query the socket type of `fd`. If there is no error, the file is a + socket. + + """ + result = False + + file_socket = socket.fromfd(fd, socket.AF_INET, socket.SOCK_RAW) + + try: + socket_type = file_socket.getsockopt( + socket.SOL_SOCKET, socket.SO_TYPE) + except socket.error as exc: + exc_errno = exc.args[0] + if exc_errno == errno.ENOTSOCK: + # Socket operation on non-socket. + pass + else: + # Some other socket error. + result = True + else: + # No error getting socket type. + result = True + + return result + + +def is_process_started_by_superserver(): + """ Determine whether the current process is started by the superserver. + + :return: ``True`` if this process was started by the internet + superserver; otherwise ``False``. + + The internet superserver creates a network socket, and + attaches it to the standard streams of the child process. If + that is the case for this process, return ``True``, otherwise + ``False``. + + """ + result = False + + stdin_fd = sys.__stdin__.fileno() + if is_socket(stdin_fd): + result = True + + return result + + +def is_detach_process_context_required(): + """ Determine whether detaching the process context is required. + + :return: ``True`` iff the process is already detached; otherwise + ``False``. + + The process environment is interrogated for the following: + + * Process was started by `init`; or + + * Process was started by `inetd`. + + If any of the above are true, the process is deemed to be already + detached. + + """ + result = True + if is_process_started_by_init() or is_process_started_by_superserver(): + result = False + + return result + + +def close_file_descriptor_if_open(fd): + """ Close a file descriptor if already open. + + :param fd: The file descriptor to close. + :return: ``None``. + + Close the file descriptor `fd`, suppressing an error in the + case the file was not open. + + """ + try: + os.close(fd) + except EnvironmentError as exc: + if exc.errno == errno.EBADF: + # File descriptor was not open. + pass + else: + error = DaemonOSEnvironmentError( + "Failed to close file descriptor {fd:d} ({exc})".format( + fd=fd, exc=exc)) + raise error + + +MAXFD = 2048 + +def get_maximum_file_descriptors(): + """ Get the maximum number of open file descriptors for this process. + + :return: The number (integer) to use as the maximum number of open + files for this process. + + The maximum is the process hard resource limit of maximum number of + open file descriptors. If the limit is “infinity”, a default value + of ``MAXFD`` is returned. + + """ + limits = resource.getrlimit(resource.RLIMIT_NOFILE) + result = limits[1] + if result == resource.RLIM_INFINITY: + result = MAXFD + return result + + +def close_all_open_files(exclude=set()): + """ Close all open file descriptors. + + :param exclude: Collection of file descriptors to skip when closing + files. + :return: ``None``. + + Closes every file descriptor (if open) of this process. If + specified, `exclude` is a set of file descriptors to *not* + close. + + """ + maxfd = get_maximum_file_descriptors() + for fd in reversed(range(maxfd)): + if fd not in exclude: + close_file_descriptor_if_open(fd) + + +def redirect_stream(system_stream, target_stream): + """ Redirect a system stream to a specified file. + + :param standard_stream: A file object representing a standard I/O + stream. + :param target_stream: The target file object for the redirected + stream, or ``None`` to specify the null device. + :return: ``None``. + + `system_stream` is a standard system stream such as + ``sys.stdout``. `target_stream` is an open file object that + should replace the corresponding system stream object. + + If `target_stream` is ``None``, defaults to opening the + operating system's null device and using its file descriptor. + + """ + if target_stream is None: + target_fd = os.open(os.devnull, os.O_RDWR) + else: + target_fd = target_stream.fileno() + os.dup2(target_fd, system_stream.fileno()) + + +def make_default_signal_map(): + """ Make the default signal map for this system. + + :return: A mapping from signal number to handler object. + + The signals available differ by system. The map will not contain + any signals not defined on the running system. + + """ + name_map = { + 'SIGTSTP': None, + 'SIGTTIN': None, + 'SIGTTOU': None, + 'SIGTERM': 'terminate', + } + signal_map = dict( + (getattr(signal, name), target) + for (name, target) in name_map.items() + if hasattr(signal, name)) + + return signal_map + + +def set_signal_handlers(signal_handler_map): + """ Set the signal handlers as specified. + + :param signal_handler_map: A map from signal number to handler + object. + :return: ``None``. + + See the `signal` module for details on signal numbers and signal + handlers. + + """ + for (signal_number, handler) in signal_handler_map.items(): + signal.signal(signal_number, handler) + + +def register_atexit_function(func): + """ Register a function for processing at program exit. + + :param func: A callable function expecting no arguments. + :return: ``None``. + + The function `func` is registered for a call with no arguments + at program exit. + + """ + atexit.register(func) + + +def _chain_exception_from_existing_exception_context(exc, as_cause=False): + """ Decorate the specified exception with the existing exception context. + + :param exc: The exception instance to decorate. + :param as_cause: If true, the existing context is declared to be + the cause of the exception. + :return: ``None``. + + :PEP:`344` describes syntax and attributes (`__traceback__`, + `__context__`, `__cause__`) for use in exception chaining. + + Python 2 does not have that syntax, so this function decorates + the exception with values from the current exception context. + + """ + (existing_exc_type, existing_exc, existing_traceback) = sys.exc_info() + if as_cause: + exc.__cause__ = existing_exc + else: + exc.__context__ = existing_exc + exc.__traceback__ = existing_traceback + + +# Local variables: +# coding: utf-8 +# mode: python +# End: +# vim: fileencoding=utf-8 filetype=python : |