fail2ban/utils/process.py

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# This file is part of Fail2Ban.
#
# Fail2Ban is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Fail2Ban is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Fail2Ban; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
# Author: Cyril Jaquier
#
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# $Revision: 1.2 $
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__author__ = "Cyril Jaquier"
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__version__ = "$Revision: 1.2 $"
__date__ = "$Date: 2005/11/20 17:07:47 $"
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__copyright__ = "Copyright (c) 2004 Cyril Jaquier"
__license__ = "GPL"
import os, logging, signal
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# Gets the instance of the logger.
logSys = logging.getLogger("fail2ban")
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class ExternalError(UserWarning):
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""" Exception to warn about failed fwcheck or fwban command
"""
pass
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def createDaemon():
""" Detach a process from the controlling terminal and run it in the
background as a daemon.
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http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/278731
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"""
try:
# Fork a child process so the parent can exit. This will return control
# to the command line or shell. This is required so that the new process
# is guaranteed not to be a process group leader. We have this guarantee
# because the process GID of the parent is inherited by the child, but
# the child gets a new PID, making it impossible for its PID to equal its
# PGID.
pid = os.fork()
except OSError, e:
return((e.errno, e.strerror)) # ERROR (return a tuple)
if (pid == 0): # The first child.
# Next we call os.setsid() to become the session leader of this new
# session. The process also becomes the process group leader of the
# new process group. Since a controlling terminal is associated with a
# session, and this new session has not yet acquired a controlling
# terminal our process now has no controlling terminal. This shouldn't
# fail, since we're guaranteed that the child is not a process group
# leader.
os.setsid()
# When the first child terminates, all processes in the second child
# are sent a SIGHUP, so it's ignored.
signal.signal(signal.SIGHUP, signal.SIG_IGN)
try:
# Fork a second child to prevent zombies. Since the first child is
# a session leader without a controlling terminal, it's possible for
# it to acquire one by opening a terminal in the future. This second
# fork guarantees that the child is no longer a session leader, thus
# preventing the daemon from ever acquiring a controlling terminal.
pid = os.fork() # Fork a second child.
except OSError, e:
return((e.errno, e.strerror)) # ERROR (return a tuple)
if (pid == 0): # The second child.
# Ensure that the daemon doesn't keep any directory in use. Failure
# to do this could make a filesystem unmountable.
os.chdir("/")
else:
os._exit(0) # Exit parent (the first child) of the second child.
else:
os._exit(0) # Exit parent of the first child.
# Close all open files. Try the system configuration variable, SC_OPEN_MAX,
# for the maximum number of open files to close. If it doesn't exist, use
# the default value (configurable).
try:
maxfd = os.sysconf("SC_OPEN_MAX")
except (AttributeError, ValueError):
maxfd = 256 # default maximum
for fd in range(0, maxfd):
try:
os.close(fd)
except OSError: # ERROR (ignore)
pass
# Redirect the standard file descriptors to /dev/null.
os.open("/dev/null", os.O_RDONLY) # standard input (0)
os.open("/dev/null", os.O_RDWR) # standard output (1)
os.open("/dev/null", os.O_RDWR) # standard error (2)
return True
def killPID(pid):
""" Kills the process with the given PID using the
INT signal (same effect as <ctrl>+<c>).
"""
try:
return os.kill(pid, 2)
except OSError:
logSys.error("Can not kill process " + `pid` + ". Please check that " +
"Fail2Ban is not running and remove the file " +
"'/tmp/fail2ban.pid'")
return False
def executeCmd(cmd, debug):
""" Executes an OS command.
"""
if cmd == "":
logSys.debug("Nothing to do")
return None
logSys.debug(cmd)
if not debug:
retval = os.system(cmd)
if not retval == 0:
logSys.error("'" + cmd + "' returned " + `retval`)
raise ExternalError("Execution of command '%s' failed" % cmd)
return retval
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else:
return None