shell bypass 403
# -*- test-case-name: twisted.test.test_twistd -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
from __future__ import absolute_import, division, print_function
import errno
import os
import pwd
import sys
import traceback
from twisted.python import log, logfile, usage
from twisted.python.compat import (intToBytes, _bytesRepr, _PY3)
from twisted.python.util import (
switchUID, uidFromString, gidFromString, untilConcludes)
from twisted.application import app, service
from twisted.internet.interfaces import IReactorDaemonize
from twisted import copyright, logger
from twisted.python.runtime import platformType
if platformType == "win32":
raise ImportError("_twistd_unix doesn't work on Windows.")
def _umask(value):
return int(value, 8)
class ServerOptions(app.ServerOptions):
synopsis = "Usage: twistd [options]"
optFlags = [['nodaemon', 'n', "don't daemonize, don't use default umask of 0077"],
['originalname', None, "Don't try to change the process name"],
['syslog', None, "Log to syslog, not to file"],
['euid', '',
"Set only effective user-id rather than real user-id. "
"(This option has no effect unless the server is running as "
"root, in which case it means not to shed all privileges "
"after binding ports, retaining the option to regain "
"privileges in cases such as spawning processes. "
"Use with caution.)"],
]
optParameters = [
['prefix', None,'twisted',
"use the given prefix when syslogging"],
['pidfile','','twistd.pid',
"Name of the pidfile"],
['chroot', None, None,
'Chroot to a supplied directory before running'],
['uid', 'u', None, "The uid to run as.", uidFromString],
['gid', 'g', None,
"The gid to run as. If not specified, the default gid "
"associated with the specified --uid is used.",
gidFromString],
['umask', None, None,
"The (octal) file creation mask to apply.", _umask],
]
compData = usage.Completions(
optActions={"pidfile": usage.CompleteFiles("*.pid"),
"chroot": usage.CompleteDirs(descr="chroot directory"),
"gid": usage.CompleteGroups(descr="gid to run as"),
"uid": usage.CompleteUsernames(descr="uid to run as"),
"prefix": usage.Completer(descr="syslog prefix"),
},
)
def opt_version(self):
"""
Print version information and exit.
"""
print('twistd (the Twisted daemon) {}'.format(copyright.version),
file=self.stdout)
print(copyright.copyright, file=self.stdout)
sys.exit()
def postOptions(self):
app.ServerOptions.postOptions(self)
if self['pidfile']:
self['pidfile'] = os.path.abspath(self['pidfile'])
def checkPID(pidfile):
if not pidfile:
return
if os.path.exists(pidfile):
try:
with open(pidfile) as f:
pid = int(f.read())
except ValueError:
sys.exit('Pidfile {} contains non-numeric value'.format(pidfile))
try:
os.kill(pid, 0)
except OSError as why:
if why.errno == errno.ESRCH:
# The pid doesn't exist.
log.msg('Removing stale pidfile {}'.format(pidfile), isError=True)
os.remove(pidfile)
else:
sys.exit(
"Can't check status of PID {} from pidfile {}: {}".format(
pid, pidfile, why))
else:
sys.exit("""\
Another twistd server is running, PID {}\n
This could either be a previously started instance of your application or a
different application entirely. To start a new one, either run it in some other
directory, or use the --pidfile and --logfile parameters to avoid clashes.
""".format(pid))
class UnixAppLogger(app.AppLogger):
"""
A logger able to log to syslog, to files, and to stdout.
@ivar _syslog: A flag indicating whether to use syslog instead of file
logging.
@type _syslog: C{bool}
@ivar _syslogPrefix: If C{sysLog} is C{True}, the string prefix to use for
syslog messages.
@type _syslogPrefix: C{str}
@ivar _nodaemon: A flag indicating the process will not be daemonizing.
@type _nodaemon: C{bool}
"""
def __init__(self, options):
app.AppLogger.__init__(self, options)
self._syslog = options.get("syslog", False)
self._syslogPrefix = options.get("prefix", "")
self._nodaemon = options.get("nodaemon", False)
def _getLogObserver(self):
"""
Create and return a suitable log observer for the given configuration.
The observer will go to syslog using the prefix C{_syslogPrefix} if
C{_syslog} is true. Otherwise, it will go to the file named
C{_logfilename} or, if C{_nodaemon} is true and C{_logfilename} is
C{"-"}, to stdout.
@return: An object suitable to be passed to C{log.addObserver}.
"""
if self._syslog:
from twisted.python import syslog
return syslog.SyslogObserver(self._syslogPrefix).emit
if self._logfilename == '-':
if not self._nodaemon:
sys.exit('Daemons cannot log to stdout, exiting!')
logFile = sys.stdout
elif self._nodaemon and not self._logfilename:
logFile = sys.stdout
else:
if not self._logfilename:
self._logfilename = 'twistd.log'
logFile = logfile.LogFile.fromFullPath(self._logfilename)
try:
import signal
except ImportError:
pass
else:
# Override if signal is set to None or SIG_DFL (0)
if not signal.getsignal(signal.SIGUSR1):
def rotateLog(signal, frame):
from twisted.internet import reactor
reactor.callFromThread(logFile.rotate)
signal.signal(signal.SIGUSR1, rotateLog)
return logger.textFileLogObserver(logFile)
def launchWithName(name):
if name and name != sys.argv[0]:
exe = os.path.realpath(sys.executable)
log.msg('Changing process name to ' + name)
os.execv(exe, [name, sys.argv[0], '--originalname'] + sys.argv[1:])
class UnixApplicationRunner(app.ApplicationRunner):
"""
An ApplicationRunner which does Unix-specific things, like fork,
shed privileges, and maintain a PID file.
"""
loggerFactory = UnixAppLogger
def preApplication(self):
"""
Do pre-application-creation setup.
"""
checkPID(self.config['pidfile'])
self.config['nodaemon'] = (self.config['nodaemon']
or self.config['debug'])
self.oldstdout = sys.stdout
self.oldstderr = sys.stderr
def _formatChildException(self, exception):
"""
Format the C{exception} in preparation for writing to the
status pipe. This does the right thing on Python 2 if the
exception's message is Unicode, and in all cases limits the
length of the message afte* encoding to 100 bytes.
This means the returned message may be truncated in the middle
of a unicode escape.
@type exception: L{Exception}
@param exception: The exception to format.
@return: The formatted message, suitable for writing to the
status pipe.
@rtype: L{bytes}
"""
# On Python 2 this will encode Unicode messages with the ascii
# codec and the backslashreplace error handler.
exceptionLine = traceback.format_exception_only(exception.__class__,
exception)[-1]
# remove the trailing newline
formattedMessage = '1 {}'.format(exceptionLine.strip())
# On Python 3, encode the message the same way Python 2's
# format_exception_only does
if _PY3:
formattedMessage = formattedMessage.encode('ascii',
'backslashreplace')
# By this point, the message has been encoded, if appropriate,
# with backslashreplace on both Python 2 and Python 3.
# Truncating the encoded message won't make it completely
# unreadable, and the reader should print out the repr of the
# message it receives anyway. What it will do, however, is
# ensure that only 100 bytes are written to the status pipe,
# ensuring that the child doesn't block because the pipe's
# full. This assumes PIPE_BUF > 100!
return formattedMessage[:100]
def postApplication(self):
"""
To be called after the application is created: start the application
and run the reactor. After the reactor stops, clean up PID files and
such.
"""
try:
self.startApplication(self.application)
except Exception as ex:
statusPipe = self.config.get("statusPipe", None)
if statusPipe is not None:
message = self._formatChildException(ex)
untilConcludes(os.write, statusPipe, message)
untilConcludes(os.close, statusPipe)
self.removePID(self.config['pidfile'])
raise
else:
statusPipe = self.config.get("statusPipe", None)
if statusPipe is not None:
untilConcludes(os.write, statusPipe, b"0")
untilConcludes(os.close, statusPipe)
self.startReactor(None, self.oldstdout, self.oldstderr)
self.removePID(self.config['pidfile'])
def removePID(self, pidfile):
"""
Remove the specified PID file, if possible. Errors are logged, not
raised.
@type pidfile: C{str}
@param pidfile: The path to the PID tracking file.
"""
if not pidfile:
return
try:
os.unlink(pidfile)
except OSError as e:
if e.errno == errno.EACCES or e.errno == errno.EPERM:
log.msg("Warning: No permission to delete pid file")
else:
log.err(e, "Failed to unlink PID file:")
except:
log.err(None, "Failed to unlink PID file:")
def setupEnvironment(self, chroot, rundir, nodaemon, umask, pidfile):
"""
Set the filesystem root, the working directory, and daemonize.
@type chroot: C{str} or L{None}
@param chroot: If not None, a path to use as the filesystem root (using
L{os.chroot}).
@type rundir: C{str}
@param rundir: The path to set as the working directory.
@type nodaemon: C{bool}
@param nodaemon: A flag which, if set, indicates that daemonization
should not be done.
@type umask: C{int} or L{None}
@param umask: The value to which to change the process umask.
@type pidfile: C{str} or L{None}
@param pidfile: If not L{None}, the path to a file into which to put
the PID of this process.
"""
daemon = not nodaemon
if chroot is not None:
os.chroot(chroot)
if rundir == '.':
rundir = '/'
os.chdir(rundir)
if daemon and umask is None:
umask = 0o077
if umask is not None:
os.umask(umask)
if daemon:
from twisted.internet import reactor
self.config["statusPipe"] = self.daemonize(reactor)
if pidfile:
with open(pidfile, 'wb') as f:
f.write(intToBytes(os.getpid()))
def daemonize(self, reactor):
"""
Daemonizes the application on Unix. This is done by the usual double
forking approach.
@see: U{http://code.activestate.com/recipes/278731/}
@see: W. Richard Stevens,
"Advanced Programming in the Unix Environment",
1992, Addison-Wesley, ISBN 0-201-56317-7
@param reactor: The reactor in use. If it provides
L{IReactorDaemonize}, its daemonization-related callbacks will be
invoked.
@return: A writable pipe to be used to report errors.
@rtype: C{int}
"""
# If the reactor requires hooks to be called for daemonization, call
# them. Currently the only reactor which provides/needs that is
# KQueueReactor.
if IReactorDaemonize.providedBy(reactor):
reactor.beforeDaemonize()
r, w = os.pipe()
if os.fork(): # launch child and...
code = self._waitForStart(r)
os.close(r)
os._exit(code) # kill off parent
os.setsid()
if os.fork(): # launch child and...
os._exit(0) # kill off parent again.
null = os.open('/dev/null', os.O_RDWR)
for i in range(3):
try:
os.dup2(null, i)
except OSError as e:
if e.errno != errno.EBADF:
raise
os.close(null)
if IReactorDaemonize.providedBy(reactor):
reactor.afterDaemonize()
return w
def _waitForStart(self, readPipe):
"""
Wait for the daemonization success.
@param readPipe: file descriptor to read start information from.
@type readPipe: C{int}
@return: code to be passed to C{os._exit}: 0 for success, 1 for error.
@rtype: C{int}
"""
data = untilConcludes(os.read, readPipe, 100)
dataRepr = _bytesRepr(data[2:])
if data != b"0":
msg = ("An error has occurred: {}\nPlease look at log "
"file for more information.\n".format(dataRepr))
untilConcludes(sys.__stderr__.write, msg)
return 1
return 0
def shedPrivileges(self, euid, uid, gid):
"""
Change the UID and GID or the EUID and EGID of this process.
@type euid: C{bool}
@param euid: A flag which, if set, indicates that only the I{effective}
UID and GID should be set.
@type uid: C{int} or L{None}
@param uid: If not L{None}, the UID to which to switch.
@type gid: C{int} or L{None}
@param gid: If not L{None}, the GID to which to switch.
"""
if uid is not None or gid is not None:
extra = euid and 'e' or ''
desc = '{}uid/{}gid {}/{}'.format(extra, extra, uid, gid)
try:
switchUID(uid, gid, euid)
except OSError as e:
log.msg('failed to set {}: {} (are you root?) -- '
'exiting.'.format(desc, e))
sys.exit(1)
else:
log.msg('set {}'.format(desc))
def startApplication(self, application):
"""
Configure global process state based on the given application and run
the application.
@param application: An object which can be adapted to
L{service.IProcess} and L{service.IService}.
"""
process = service.IProcess(application)
if not self.config['originalname']:
launchWithName(process.processName)
self.setupEnvironment(
self.config['chroot'], self.config['rundir'],
self.config['nodaemon'], self.config['umask'],
self.config['pidfile'])
service.IService(application).privilegedStartService()
uid, gid = self.config['uid'], self.config['gid']
if uid is None:
uid = process.uid
if gid is None:
gid = process.gid
if uid is not None and gid is None:
gid = pwd.getpwuid(uid).pw_gid
self.shedPrivileges(self.config['euid'], uid, gid)
app.startApplication(application, not self.config['no_save'])