549 lines
18 KiB
Python
Executable file
549 lines
18 KiB
Python
Executable file
#! /usr/bin/env python
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"""An RFC 2821 smtp proxy.
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Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]]
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Options:
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--nosetuid
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-n
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This program generally tries to setuid `nobody', unless this flag is
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set. The setuid call will fail if this program is not run as root (in
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which case, use this flag).
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--version
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-V
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Print the version number and exit.
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--class classname
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-c classname
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Use `classname' as the concrete SMTP proxy class. Uses `PureProxy' by
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default.
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--debug
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-d
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Turn on debugging prints.
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--help
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-h
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Print this message and exit.
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Version: %(__version__)s
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If localhost is not given then `localhost' is used, and if localport is not
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given then 8025 is used. If remotehost is not given then `localhost' is used,
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and if remoteport is not given, then 25 is used.
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"""
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# Overview:
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#
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# This file implements the minimal SMTP protocol as defined in RFC 821. It
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# has a hierarchy of classes which implement the backend functionality for the
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# smtpd. A number of classes are provided:
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#
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# SMTPServer - the base class for the backend. Raises NotImplementedError
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# if you try to use it.
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#
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# DebuggingServer - simply prints each message it receives on stdout.
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#
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# PureProxy - Proxies all messages to a real smtpd which does final
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# delivery. One known problem with this class is that it doesn't handle
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# SMTP errors from the backend server at all. This should be fixed
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# (contributions are welcome!).
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#
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# MailmanProxy - An experimental hack to work with GNU Mailman
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# <www.list.org>. Using this server as your real incoming smtpd, your
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# mailhost will automatically recognize and accept mail destined to Mailman
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# lists when those lists are created. Every message not destined for a list
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# gets forwarded to a real backend smtpd, as with PureProxy. Again, errors
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# are not handled correctly yet.
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#
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# Please note that this script requires Python 2.0
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#
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# Author: Barry Warsaw <barry@python.org>
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#
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# TODO:
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#
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# - support mailbox delivery
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# - alias files
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# - ESMTP
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# - handle error codes from the backend smtpd
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import sys
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import os
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import errno
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import getopt
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import time
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import socket
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import asyncore
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import asynchat
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__all__ = ["SMTPServer","DebuggingServer","PureProxy","MailmanProxy"]
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program = sys.argv[0]
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__version__ = 'Python SMTP proxy version 0.2'
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class Devnull:
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def write(self, msg): pass
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def flush(self): pass
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DEBUGSTREAM = Devnull()
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NEWLINE = '\n'
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EMPTYSTRING = ''
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COMMASPACE = ', '
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def usage(code, msg=''):
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print >> sys.stderr, __doc__ % globals()
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if msg:
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print >> sys.stderr, msg
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sys.exit(code)
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class SMTPChannel(asynchat.async_chat):
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COMMAND = 0
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DATA = 1
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def __init__(self, server, conn, addr):
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asynchat.async_chat.__init__(self, conn)
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self.__server = server
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self.__conn = conn
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self.__addr = addr
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self.__line = []
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self.__state = self.COMMAND
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self.__greeting = 0
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self.__mailfrom = None
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self.__rcpttos = []
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self.__data = ''
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self.__fqdn = socket.getfqdn()
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self.__peer = conn.getpeername()
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print >> DEBUGSTREAM, 'Peer:', repr(self.__peer)
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self.push('220 %s %s' % (self.__fqdn, __version__))
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self.set_terminator('\r\n')
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# Overrides base class for convenience
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def push(self, msg):
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asynchat.async_chat.push(self, msg + '\r\n')
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# Implementation of base class abstract method
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def collect_incoming_data(self, data):
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self.__line.append(data)
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# Implementation of base class abstract method
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def found_terminator(self):
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line = EMPTYSTRING.join(self.__line)
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print >> DEBUGSTREAM, 'Data:', repr(line)
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self.__line = []
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if self.__state == self.COMMAND:
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if not line:
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self.push('500 Error: bad syntax')
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return
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method = None
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i = line.find(' ')
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if i < 0:
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command = line.upper()
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arg = None
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else:
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command = line[:i].upper()
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arg = line[i+1:].strip()
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method = getattr(self, 'smtp_' + command, None)
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if not method:
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self.push('502 Error: command "%s" not implemented' % command)
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return
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method(arg)
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return
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else:
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if self.__state != self.DATA:
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self.push('451 Internal confusion')
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return
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# Remove extraneous carriage returns and de-transparency according
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# to RFC 821, Section 4.5.2.
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data = []
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for text in line.split('\r\n'):
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if text and text[0] == '.':
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data.append(text[1:])
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else:
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data.append(text)
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self.__data = NEWLINE.join(data)
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status = self.__server.process_message(self.__peer,
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self.__mailfrom,
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self.__rcpttos,
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self.__data)
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self.__rcpttos = []
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self.__mailfrom = None
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self.__state = self.COMMAND
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self.set_terminator('\r\n')
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if not status:
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self.push('250 Ok')
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else:
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self.push(status)
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# SMTP and ESMTP commands
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def smtp_HELO(self, arg):
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if not arg:
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self.push('501 Syntax: HELO hostname')
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return
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if self.__greeting:
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self.push('503 Duplicate HELO/EHLO')
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else:
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self.__greeting = arg
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self.push('250 %s' % self.__fqdn)
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def smtp_NOOP(self, arg):
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if arg:
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self.push('501 Syntax: NOOP')
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else:
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self.push('250 Ok')
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def smtp_QUIT(self, arg):
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# args is ignored
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self.push('221 Bye')
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self.close_when_done()
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# factored
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def __getaddr(self, keyword, arg):
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address = None
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keylen = len(keyword)
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if arg[:keylen].upper() == keyword:
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address = arg[keylen:].strip()
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if not address:
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pass
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elif address[0] == '<' and address[-1] == '>' and address != '<>':
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# Addresses can be in the form <person@dom.com> but watch out
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# for null address, e.g. <>
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address = address[1:-1]
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return address
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def smtp_MAIL(self, arg):
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print >> DEBUGSTREAM, '===> MAIL', arg
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address = self.__getaddr('FROM:', arg)
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if not address:
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self.push('501 Syntax: MAIL FROM:<address>')
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return
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if self.__mailfrom:
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self.push('503 Error: nested MAIL command')
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return
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self.__mailfrom = address
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print >> DEBUGSTREAM, 'sender:', self.__mailfrom
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self.push('250 Ok')
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def smtp_RCPT(self, arg):
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print >> DEBUGSTREAM, '===> RCPT', arg
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if not self.__mailfrom:
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self.push('503 Error: need MAIL command')
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return
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address = self.__getaddr('TO:', arg)
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if not address:
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self.push('501 Syntax: RCPT TO: <address>')
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return
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self.__rcpttos.append(address)
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print >> DEBUGSTREAM, 'recips:', self.__rcpttos
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self.push('250 Ok')
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def smtp_RSET(self, arg):
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if arg:
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self.push('501 Syntax: RSET')
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return
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# Resets the sender, recipients, and data, but not the greeting
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self.__mailfrom = None
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self.__rcpttos = []
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self.__data = ''
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self.__state = self.COMMAND
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self.push('250 Ok')
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def smtp_DATA(self, arg):
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if not self.__rcpttos:
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self.push('503 Error: need RCPT command')
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return
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if arg:
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self.push('501 Syntax: DATA')
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return
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self.__state = self.DATA
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self.set_terminator('\r\n.\r\n')
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self.push('354 End data with <CR><LF>.<CR><LF>')
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class SMTPServer(asyncore.dispatcher):
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def __init__(self, localaddr, remoteaddr):
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self._localaddr = localaddr
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self._remoteaddr = remoteaddr
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asyncore.dispatcher.__init__(self)
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self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
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# try to re-use a server port if possible
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self.set_reuse_addr()
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self.bind(localaddr)
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self.listen(5)
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print >> DEBUGSTREAM, \
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'%s started at %s\n\tLocal addr: %s\n\tRemote addr:%s' % (
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self.__class__.__name__, time.ctime(time.time()),
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localaddr, remoteaddr)
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def handle_accept(self):
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conn, addr = self.accept()
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print >> DEBUGSTREAM, 'Incoming connection from %s' % repr(addr)
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channel = SMTPChannel(self, conn, addr)
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# API for "doing something useful with the message"
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def process_message(self, peer, mailfrom, rcpttos, data):
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"""Override this abstract method to handle messages from the client.
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peer is a tuple containing (ipaddr, port) of the client that made the
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socket connection to our smtp port.
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mailfrom is the raw address the client claims the message is coming
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from.
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rcpttos is a list of raw addresses the client wishes to deliver the
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message to.
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data is a string containing the entire full text of the message,
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headers (if supplied) and all. It has been `de-transparencied'
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according to RFC 821, Section 4.5.2. In other words, a line
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containing a `.' followed by other text has had the leading dot
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removed.
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This function should return None, for a normal `250 Ok' response;
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otherwise it returns the desired response string in RFC 821 format.
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"""
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raise NotImplementedError
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class DebuggingServer(SMTPServer):
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# Do something with the gathered message
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def process_message(self, peer, mailfrom, rcpttos, data):
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inheaders = 1
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lines = data.split('\n')
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print '---------- MESSAGE FOLLOWS ----------'
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for line in lines:
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# headers first
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if inheaders and not line:
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print 'X-Peer:', peer[0]
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inheaders = 0
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print line
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print '------------ END MESSAGE ------------'
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class PureProxy(SMTPServer):
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def process_message(self, peer, mailfrom, rcpttos, data):
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lines = data.split('\n')
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# Look for the last header
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i = 0
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for line in lines:
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if not line:
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break
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i += 1
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lines.insert(i, 'X-Peer: %s' % peer[0])
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data = NEWLINE.join(lines)
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refused = self._deliver(mailfrom, rcpttos, data)
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# TBD: what to do with refused addresses?
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print >> DEBUGSTREAM, 'we got some refusals:', refused
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def _deliver(self, mailfrom, rcpttos, data):
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import smtplib
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refused = {}
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try:
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s = smtplib.SMTP()
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s.connect(self._remoteaddr[0], self._remoteaddr[1])
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try:
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refused = s.sendmail(mailfrom, rcpttos, data)
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finally:
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s.quit()
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except smtplib.SMTPRecipientsRefused, e:
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print >> DEBUGSTREAM, 'got SMTPRecipientsRefused'
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refused = e.recipients
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except (socket.error, smtplib.SMTPException), e:
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print >> DEBUGSTREAM, 'got', e.__class__
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# All recipients were refused. If the exception had an associated
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# error code, use it. Otherwise,fake it with a non-triggering
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# exception code.
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errcode = getattr(e, 'smtp_code', -1)
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errmsg = getattr(e, 'smtp_error', 'ignore')
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for r in rcpttos:
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refused[r] = (errcode, errmsg)
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return refused
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class MailmanProxy(PureProxy):
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def process_message(self, peer, mailfrom, rcpttos, data):
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from cStringIO import StringIO
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from Mailman import Utils
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from Mailman import Message
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from Mailman import MailList
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# If the message is to a Mailman mailing list, then we'll invoke the
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# Mailman script directly, without going through the real smtpd.
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# Otherwise we'll forward it to the local proxy for disposition.
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listnames = []
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for rcpt in rcpttos:
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local = rcpt.lower().split('@')[0]
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# We allow the following variations on the theme
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# listname
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# listname-admin
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# listname-owner
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# listname-request
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# listname-join
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# listname-leave
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parts = local.split('-')
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if len(parts) > 2:
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continue
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listname = parts[0]
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if len(parts) == 2:
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command = parts[1]
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else:
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command = ''
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if not Utils.list_exists(listname) or command not in (
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'', 'admin', 'owner', 'request', 'join', 'leave'):
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continue
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listnames.append((rcpt, listname, command))
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# Remove all list recipients from rcpttos and forward what we're not
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# going to take care of ourselves. Linear removal should be fine
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# since we don't expect a large number of recipients.
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for rcpt, listname, command in listnames:
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rcpttos.remove(rcpt)
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# If there's any non-list destined recipients left,
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print >> DEBUGSTREAM, 'forwarding recips:', ' '.join(rcpttos)
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if rcpttos:
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refused = self._deliver(mailfrom, rcpttos, data)
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# TBD: what to do with refused addresses?
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print >> DEBUGSTREAM, 'we got refusals:', refused
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# Now deliver directly to the list commands
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mlists = {}
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s = StringIO(data)
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msg = Message.Message(s)
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# These headers are required for the proper execution of Mailman. All
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# MTAs in existance seem to add these if the original message doesn't
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# have them.
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if not msg.getheader('from'):
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msg['From'] = mailfrom
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if not msg.getheader('date'):
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msg['Date'] = time.ctime(time.time())
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for rcpt, listname, command in listnames:
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print >> DEBUGSTREAM, 'sending message to', rcpt
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mlist = mlists.get(listname)
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if not mlist:
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mlist = MailList.MailList(listname, lock=0)
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mlists[listname] = mlist
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# dispatch on the type of command
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if command == '':
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# post
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msg.Enqueue(mlist, tolist=1)
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elif command == 'admin':
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msg.Enqueue(mlist, toadmin=1)
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elif command == 'owner':
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msg.Enqueue(mlist, toowner=1)
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elif command == 'request':
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msg.Enqueue(mlist, torequest=1)
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elif command in ('join', 'leave'):
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# TBD: this is a hack!
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if command == 'join':
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msg['Subject'] = 'subscribe'
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else:
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msg['Subject'] = 'unsubscribe'
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msg.Enqueue(mlist, torequest=1)
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class Options:
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setuid = 1
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classname = 'PureProxy'
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def parseargs():
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global DEBUGSTREAM
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try:
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opts, args = getopt.getopt(
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sys.argv[1:], 'nVhc:d',
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['class=', 'nosetuid', 'version', 'help', 'debug'])
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except getopt.error, e:
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usage(1, e)
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options = Options()
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for opt, arg in opts:
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if opt in ('-h', '--help'):
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usage(0)
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elif opt in ('-V', '--version'):
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print >> sys.stderr, __version__
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sys.exit(0)
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elif opt in ('-n', '--nosetuid'):
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options.setuid = 0
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elif opt in ('-c', '--class'):
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options.classname = arg
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elif opt in ('-d', '--debug'):
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DEBUGSTREAM = sys.stderr
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# parse the rest of the arguments
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if len(args) < 1:
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localspec = 'localhost:8025'
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remotespec = 'localhost:25'
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elif len(args) < 2:
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localspec = args[0]
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remotespec = 'localhost:25'
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elif len(args) < 3:
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localspec = args[0]
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remotespec = args[1]
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else:
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usage(1, 'Invalid arguments: %s' % COMMASPACE.join(args))
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# split into host/port pairs
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i = localspec.find(':')
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if i < 0:
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usage(1, 'Bad local spec: %s' % localspec)
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options.localhost = localspec[:i]
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try:
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options.localport = int(localspec[i+1:])
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except ValueError:
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usage(1, 'Bad local port: %s' % localspec)
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i = remotespec.find(':')
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if i < 0:
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usage(1, 'Bad remote spec: %s' % remotespec)
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options.remotehost = remotespec[:i]
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try:
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options.remoteport = int(remotespec[i+1:])
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except ValueError:
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usage(1, 'Bad remote port: %s' % remotespec)
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return options
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if __name__ == '__main__':
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options = parseargs()
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# Become nobody
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if options.setuid:
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try:
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import pwd
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except ImportError:
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print >> sys.stderr, \
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'Cannot import module "pwd"; try running with -n option.'
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sys.exit(1)
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nobody = pwd.getpwnam('nobody')[2]
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try:
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os.setuid(nobody)
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except OSError, e:
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if e.errno != errno.EPERM: raise
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print >> sys.stderr, \
|
||
'Cannot setuid "nobody"; try running with -n option.'
|
||
sys.exit(1)
|
||
classname = options.classname
|
||
if "." in classname:
|
||
lastdot = classname.rfind(".")
|
||
mod = __import__(classname[:lastdot], globals(), locals(), [""])
|
||
classname = classname[lastdot+1:]
|
||
else:
|
||
import __main__ as mod
|
||
class_ = getattr(mod, classname)
|
||
proxy = class_((options.localhost, options.localport),
|
||
(options.remotehost, options.remoteport))
|
||
try:
|
||
asyncore.loop()
|
||
except KeyboardInterrupt:
|
||
pass
|