| 1 | #! /usr/bin/env python |
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| 2 | """An RFC 2821 smtp proxy. |
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| 3 | |
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| 4 | Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]] |
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| 5 | |
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| 6 | Options: |
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| 7 | |
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| 8 | --nosetuid |
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| 9 | -n |
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| 10 | This program generally tries to setuid `nobody', unless this flag is |
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| 11 | set. The setuid call will fail if this program is not run as root (in |
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| 12 | which case, use this flag). |
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| 13 | |
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| 14 | --version |
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| 15 | -V |
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| 16 | Print the version number and exit. |
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| 17 | |
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| 18 | --class classname |
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| 19 | -c classname |
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| 20 | Use `classname' as the concrete SMTP proxy class. Uses `PureProxy' by |
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| 21 | default. |
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| 22 | |
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| 23 | --debug |
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| 24 | -d |
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| 25 | Turn on debugging prints. |
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| 26 | |
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| 27 | --help |
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| 28 | -h |
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| 29 | Print this message and exit. |
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| 30 | |
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| 31 | Version: %(__version__)s |
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| 32 | |
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| 33 | If localhost is not given then `localhost' is used, and if localport is not |
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| 34 | given then 8025 is used. If remotehost is not given then `localhost' is used, |
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| 35 | and if remoteport is not given, then 25 is used. |
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| 36 | """ |
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| 37 | |
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| 38 | # Overview: |
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| 39 | # |
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| 40 | # This file implements the minimal SMTP protocol as defined in RFC 821. It |
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| 41 | # has a hierarchy of classes which implement the backend functionality for the |
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| 42 | # smtpd. A number of classes are provided: |
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| 43 | # |
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| 44 | # SMTPServer - the base class for the backend. Raises NotImplementedError |
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| 45 | # if you try to use it. |
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| 46 | # |
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| 47 | # DebuggingServer - simply prints each message it receives on stdout. |
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| 48 | # |
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| 49 | # PureProxy - Proxies all messages to a real smtpd which does final |
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| 50 | # delivery. One known problem with this class is that it doesn't handle |
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| 51 | # SMTP errors from the backend server at all. This should be fixed |
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| 52 | # (contributions are welcome!). |
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| 53 | # |
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| 54 | # MailmanProxy - An experimental hack to work with GNU Mailman |
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| 55 | # <www.list.org>. Using this server as your real incoming smtpd, your |
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| 56 | # mailhost will automatically recognize and accept mail destined to Mailman |
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| 57 | # lists when those lists are created. Every message not destined for a list |
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| 58 | # gets forwarded to a real backend smtpd, as with PureProxy. Again, errors |
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| 59 | # are not handled correctly yet. |
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| 60 | # |
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| 61 | # Please note that this script requires Python 2.0 |
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| 62 | # |
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| 63 | # Author: Barry Warsaw <barry@python.org> |
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| 64 | # |
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| 65 | # TODO: |
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| 66 | # |
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| 67 | # - support mailbox delivery |
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| 68 | # - alias files |
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| 69 | # - ESMTP |
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| 70 | # - handle error codes from the backend smtpd |
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| 71 | |
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| 72 | import sys |
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| 73 | import os |
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| 74 | import errno |
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| 75 | import getopt |
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| 76 | import time |
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| 77 | import socket |
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| 78 | import asyncore |
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| 79 | import asynchat |
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| 80 | |
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| 81 | __all__ = ["SMTPServer","DebuggingServer","PureProxy","MailmanProxy"] |
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| 82 | |
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| 83 | program = sys.argv[0] |
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| 84 | __version__ = 'Python SMTP proxy version 0.2' |
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| 85 | |
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| 86 | |
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| 87 | class Devnull: |
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| 88 | def write(self, msg): pass |
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| 89 | def flush(self): pass |
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| 90 | |
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| 91 | |
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| 92 | DEBUGSTREAM = Devnull() |
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| 93 | NEWLINE = '\n' |
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| 94 | EMPTYSTRING = '' |
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| 95 | COMMASPACE = ', ' |
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| 96 | |
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| 97 | |
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| 98 | def usage(code, msg=''): |
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| 99 | print >> sys.stderr, __doc__ % globals() |
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| 100 | if msg: |
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| 101 | print >> sys.stderr, msg |
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| 102 | sys.exit(code) |
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| 103 | |
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| 104 | |
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| 105 | class SMTPChannel(asynchat.async_chat): |
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| 106 | COMMAND = 0 |
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| 107 | DATA = 1 |
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| 108 | |
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| 109 | def __init__(self, server, conn, addr): |
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| 110 | asynchat.async_chat.__init__(self, conn) |
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| 111 | self.__server = server |
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| 112 | self.__conn = conn |
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| 113 | self.__addr = addr |
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| 114 | self.__line = [] |
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| 115 | self.__state = self.COMMAND |
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| 116 | self.__greeting = 0 |
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| 117 | self.__mailfrom = None |
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| 118 | self.__rcpttos = [] |
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| 119 | self.__data = '' |
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| 120 | self.__fqdn = socket.getfqdn() |
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| 121 | try: |
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| 122 | self.__peer = conn.getpeername() |
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| 123 | except socket.error, err: |
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| 124 | # a race condition may occur if the other end is closing |
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| 125 | # before we can get the peername |
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| 126 | self.close() |
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| 127 | if err[0] != errno.ENOTCONN: |
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| 128 | raise |
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| 129 | return |
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| 130 | print >> DEBUGSTREAM, 'Peer:', repr(self.__peer) |
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| 131 | self.push('220 %s %s' % (self.__fqdn, __version__)) |
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| 132 | self.set_terminator('\r\n') |
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| 133 | |
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| 134 | # Overrides base class for convenience |
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| 135 | def push(self, msg): |
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| 136 | asynchat.async_chat.push(self, msg + '\r\n') |
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| 137 | |
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| 138 | # Implementation of base class abstract method |
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| 139 | def collect_incoming_data(self, data): |
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| 140 | self.__line.append(data) |
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| 141 | |
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| 142 | # Implementation of base class abstract method |
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| 143 | def found_terminator(self): |
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| 144 | line = EMPTYSTRING.join(self.__line) |
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| 145 | print >> DEBUGSTREAM, 'Data:', repr(line) |
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| 146 | self.__line = [] |
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| 147 | if self.__state == self.COMMAND: |
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| 148 | if not line: |
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| 149 | self.push('500 Error: bad syntax') |
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| 150 | return |
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| 151 | method = None |
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| 152 | i = line.find(' ') |
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| 153 | if i < 0: |
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| 154 | command = line.upper() |
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| 155 | arg = None |
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| 156 | else: |
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| 157 | command = line[:i].upper() |
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| 158 | arg = line[i+1:].strip() |
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| 159 | method = getattr(self, 'smtp_' + command, None) |
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| 160 | if not method: |
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| 161 | self.push('502 Error: command "%s" not implemented' % command) |
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| 162 | return |
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| 163 | method(arg) |
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| 164 | return |
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| 165 | else: |
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| 166 | if self.__state != self.DATA: |
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| 167 | self.push('451 Internal confusion') |
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| 168 | return |
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| 169 | # Remove extraneous carriage returns and de-transparency according |
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| 170 | # to RFC 821, Section 4.5.2. |
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| 171 | data = [] |
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| 172 | for text in line.split('\r\n'): |
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| 173 | if text and text[0] == '.': |
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| 174 | data.append(text[1:]) |
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| 175 | else: |
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| 176 | data.append(text) |
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| 177 | self.__data = NEWLINE.join(data) |
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| 178 | status = self.__server.process_message(self.__peer, |
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| 179 | self.__mailfrom, |
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| 180 | self.__rcpttos, |
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| 181 | self.__data) |
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| 182 | self.__rcpttos = [] |
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| 183 | self.__mailfrom = None |
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| 184 | self.__state = self.COMMAND |
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| 185 | self.set_terminator('\r\n') |
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| 186 | if not status: |
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| 187 | self.push('250 Ok') |
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| 188 | else: |
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| 189 | self.push(status) |
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| 190 | |
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| 191 | # SMTP and ESMTP commands |
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| 192 | def smtp_HELO(self, arg): |
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| 193 | if not arg: |
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| 194 | self.push('501 Syntax: HELO hostname') |
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| 195 | return |
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| 196 | if self.__greeting: |
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| 197 | self.push('503 Duplicate HELO/EHLO') |
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| 198 | else: |
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| 199 | self.__greeting = arg |
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| 200 | self.push('250 %s' % self.__fqdn) |
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| 201 | |
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| 202 | def smtp_NOOP(self, arg): |
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| 203 | if arg: |
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| 204 | self.push('501 Syntax: NOOP') |
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| 205 | else: |
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| 206 | self.push('250 Ok') |
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| 207 | |
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| 208 | def smtp_QUIT(self, arg): |
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| 209 | # args is ignored |
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| 210 | self.push('221 Bye') |
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| 211 | self.close_when_done() |
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| 212 | |
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| 213 | # factored |
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| 214 | def __getaddr(self, keyword, arg): |
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| 215 | address = None |
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| 216 | keylen = len(keyword) |
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| 217 | if arg[:keylen].upper() == keyword: |
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| 218 | address = arg[keylen:].strip() |
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| 219 | if not address: |
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| 220 | pass |
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| 221 | elif address[0] == '<' and address[-1] == '>' and address != '<>': |
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| 222 | # Addresses can be in the form <person@dom.com> but watch out |
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| 223 | # for null address, e.g. <> |
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| 224 | address = address[1:-1] |
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| 225 | return address |
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| 226 | |
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| 227 | def smtp_MAIL(self, arg): |
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| 228 | print >> DEBUGSTREAM, '===> MAIL', arg |
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| 229 | address = self.__getaddr('FROM:', arg) if arg else None |
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| 230 | if not address: |
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| 231 | self.push('501 Syntax: MAIL FROM:<address>') |
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| 232 | return |
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| 233 | if self.__mailfrom: |
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| 234 | self.push('503 Error: nested MAIL command') |
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| 235 | return |
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| 236 | self.__mailfrom = address |
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| 237 | print >> DEBUGSTREAM, 'sender:', self.__mailfrom |
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| 238 | self.push('250 Ok') |
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| 239 | |
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| 240 | def smtp_RCPT(self, arg): |
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| 241 | print >> DEBUGSTREAM, '===> RCPT', arg |
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| 242 | if not self.__mailfrom: |
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| 243 | self.push('503 Error: need MAIL command') |
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| 244 | return |
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| 245 | address = self.__getaddr('TO:', arg) if arg else None |
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| 246 | if not address: |
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| 247 | self.push('501 Syntax: RCPT TO: <address>') |
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| 248 | return |
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| 249 | self.__rcpttos.append(address) |
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| 250 | print >> DEBUGSTREAM, 'recips:', self.__rcpttos |
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| 251 | self.push('250 Ok') |
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| 252 | |
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| 253 | def smtp_RSET(self, arg): |
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| 254 | if arg: |
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| 255 | self.push('501 Syntax: RSET') |
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| 256 | return |
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| 257 | # Resets the sender, recipients, and data, but not the greeting |
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| 258 | self.__mailfrom = None |
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| 259 | self.__rcpttos = [] |
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| 260 | self.__data = '' |
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| 261 | self.__state = self.COMMAND |
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| 262 | self.push('250 Ok') |
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| 263 | |
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| 264 | def smtp_DATA(self, arg): |
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| 265 | if not self.__rcpttos: |
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| 266 | self.push('503 Error: need RCPT command') |
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| 267 | return |
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| 268 | if arg: |
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| 269 | self.push('501 Syntax: DATA') |
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| 270 | return |
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| 271 | self.__state = self.DATA |
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| 272 | self.set_terminator('\r\n.\r\n') |
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| 273 | self.push('354 End data with <CR><LF>.<CR><LF>') |
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| 274 | |
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| 275 | |
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| 276 | class SMTPServer(asyncore.dispatcher): |
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| 277 | def __init__(self, localaddr, remoteaddr): |
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| 278 | self._localaddr = localaddr |
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| 279 | self._remoteaddr = remoteaddr |
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| 280 | asyncore.dispatcher.__init__(self) |
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| 281 | try: |
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| 282 | self.create_socket(socket.AF_INET, socket.SOCK_STREAM) |
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| 283 | # try to re-use a server port if possible |
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| 284 | self.set_reuse_addr() |
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| 285 | self.bind(localaddr) |
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| 286 | self.listen(5) |
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| 287 | except: |
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| 288 | # cleanup asyncore.socket_map before raising |
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| 289 | self.close() |
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| 290 | raise |
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| 291 | else: |
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| 292 | print >> DEBUGSTREAM, \ |
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| 293 | '%s started at %s\n\tLocal addr: %s\n\tRemote addr:%s' % ( |
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| 294 | self.__class__.__name__, time.ctime(time.time()), |
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| 295 | localaddr, remoteaddr) |
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| 296 | |
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| 297 | def handle_accept(self): |
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| 298 | pair = self.accept() |
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| 299 | if pair is not None: |
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| 300 | conn, addr = pair |
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| 301 | print >> DEBUGSTREAM, 'Incoming connection from %s' % repr(addr) |
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| 302 | channel = SMTPChannel(self, conn, addr) |
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| 303 | |
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| 304 | # API for "doing something useful with the message" |
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| 305 | def process_message(self, peer, mailfrom, rcpttos, data): |
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| 306 | """Override this abstract method to handle messages from the client. |
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| 307 | |
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| 308 | peer is a tuple containing (ipaddr, port) of the client that made the |
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| 309 | socket connection to our smtp port. |
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| 310 | |
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| 311 | mailfrom is the raw address the client claims the message is coming |
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| 312 | from. |
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| 313 | |
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| 314 | rcpttos is a list of raw addresses the client wishes to deliver the |
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| 315 | message to. |
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| 316 | |
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| 317 | data is a string containing the entire full text of the message, |
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| 318 | headers (if supplied) and all. It has been `de-transparencied' |
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| 319 | according to RFC 821, Section 4.5.2. In other words, a line |
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| 320 | containing a `.' followed by other text has had the leading dot |
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| 321 | removed. |
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| 322 | |
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| 323 | This function should return None, for a normal `250 Ok' response; |
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| 324 | otherwise it returns the desired response string in RFC 821 format. |
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| 325 | |
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| 326 | """ |
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| 327 | raise NotImplementedError |
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| 328 | |
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| 329 | |
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| 330 | class DebuggingServer(SMTPServer): |
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| 331 | # Do something with the gathered message |
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| 332 | def process_message(self, peer, mailfrom, rcpttos, data): |
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| 333 | inheaders = 1 |
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| 334 | lines = data.split('\n') |
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| 335 | print '---------- MESSAGE FOLLOWS ----------' |
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| 336 | for line in lines: |
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| 337 | # headers first |
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| 338 | if inheaders and not line: |
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| 339 | print 'X-Peer:', peer[0] |
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| 340 | inheaders = 0 |
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| 341 | print line |
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| 342 | print '------------ END MESSAGE ------------' |
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| 343 | |
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| 344 | |
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| 345 | class PureProxy(SMTPServer): |
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| 346 | def process_message(self, peer, mailfrom, rcpttos, data): |
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| 347 | lines = data.split('\n') |
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| 348 | # Look for the last header |
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| 349 | i = 0 |
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| 350 | for line in lines: |
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| 351 | if not line: |
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| 352 | break |
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| 353 | i += 1 |
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| 354 | lines.insert(i, 'X-Peer: %s' % peer[0]) |
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| 355 | data = NEWLINE.join(lines) |
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| 356 | refused = self._deliver(mailfrom, rcpttos, data) |
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| 357 | # TBD: what to do with refused addresses? |
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| 358 | print >> DEBUGSTREAM, 'we got some refusals:', refused |
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| 359 | |
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| 360 | def _deliver(self, mailfrom, rcpttos, data): |
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| 361 | import smtplib |
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| 362 | refused = {} |
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| 363 | try: |
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| 364 | s = smtplib.SMTP() |
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| 365 | s.connect(self._remoteaddr[0], self._remoteaddr[1]) |
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| 366 | try: |
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| 367 | refused = s.sendmail(mailfrom, rcpttos, data) |
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| 368 | finally: |
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| 369 | s.quit() |
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| 370 | except smtplib.SMTPRecipientsRefused, e: |
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| 371 | print >> DEBUGSTREAM, 'got SMTPRecipientsRefused' |
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| 372 | refused = e.recipients |
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| 373 | except (socket.error, smtplib.SMTPException), e: |
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| 374 | print >> DEBUGSTREAM, 'got', e.__class__ |
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| 375 | # All recipients were refused. If the exception had an associated |
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| 376 | # error code, use it. Otherwise,fake it with a non-triggering |
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| 377 | # exception code. |
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| 378 | errcode = getattr(e, 'smtp_code', -1) |
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| 379 | errmsg = getattr(e, 'smtp_error', 'ignore') |
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| 380 | for r in rcpttos: |
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| 381 | refused[r] = (errcode, errmsg) |
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| 382 | return refused |
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| 383 | |
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| 384 | |
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| 385 | class MailmanProxy(PureProxy): |
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| 386 | def process_message(self, peer, mailfrom, rcpttos, data): |
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| 387 | from cStringIO import StringIO |
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| 388 | from Mailman import Utils |
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| 389 | from Mailman import Message |
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| 390 | from Mailman import MailList |
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| 391 | # If the message is to a Mailman mailing list, then we'll invoke the |
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| 392 | # Mailman script directly, without going through the real smtpd. |
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| 393 | # Otherwise we'll forward it to the local proxy for disposition. |
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| 394 | listnames = [] |
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| 395 | for rcpt in rcpttos: |
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| 396 | local = rcpt.lower().split('@')[0] |
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| 397 | # We allow the following variations on the theme |
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| 398 | # listname |
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| 399 | # listname-admin |
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| 400 | # listname-owner |
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| 401 | # listname-request |
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| 402 | # listname-join |
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| 403 | # listname-leave |
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| 404 | parts = local.split('-') |
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| 405 | if len(parts) > 2: |
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| 406 | continue |
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| 407 | listname = parts[0] |
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| 408 | if len(parts) == 2: |
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| 409 | command = parts[1] |
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| 410 | else: |
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| 411 | command = '' |
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| 412 | if not Utils.list_exists(listname) or command not in ( |
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| 413 | '', 'admin', 'owner', 'request', 'join', 'leave'): |
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| 414 | continue |
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| 415 | listnames.append((rcpt, listname, command)) |
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| 416 | # Remove all list recipients from rcpttos and forward what we're not |
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| 417 | # going to take care of ourselves. Linear removal should be fine |
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| 418 | # since we don't expect a large number of recipients. |
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| 419 | for rcpt, listname, command in listnames: |
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| 420 | rcpttos.remove(rcpt) |
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| 421 | # If there's any non-list destined recipients left, |
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| 422 | print >> DEBUGSTREAM, 'forwarding recips:', ' '.join(rcpttos) |
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| 423 | if rcpttos: |
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| 424 | refused = self._deliver(mailfrom, rcpttos, data) |
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| 425 | # TBD: what to do with refused addresses? |
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| 426 | print >> DEBUGSTREAM, 'we got refusals:', refused |
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| 427 | # Now deliver directly to the list commands |
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| 428 | mlists = {} |
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| 429 | s = StringIO(data) |
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| 430 | msg = Message.Message(s) |
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| 431 | # These headers are required for the proper execution of Mailman. All |
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| 432 | # MTAs in existence seem to add these if the original message doesn't |
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| 433 | # have them. |
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| 434 | if not msg.getheader('from'): |
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| 435 | msg['From'] = mailfrom |
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| 436 | if not msg.getheader('date'): |
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| 437 | msg['Date'] = time.ctime(time.time()) |
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| 438 | for rcpt, listname, command in listnames: |
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| 439 | print >> DEBUGSTREAM, 'sending message to', rcpt |
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| 440 | mlist = mlists.get(listname) |
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| 441 | if not mlist: |
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| 442 | mlist = MailList.MailList(listname, lock=0) |
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| 443 | mlists[listname] = mlist |
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| 444 | # dispatch on the type of command |
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| 445 | if command == '': |
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| 446 | # post |
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| 447 | msg.Enqueue(mlist, tolist=1) |
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| 448 | elif command == 'admin': |
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| 449 | msg.Enqueue(mlist, toadmin=1) |
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| 450 | elif command == 'owner': |
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| 451 | msg.Enqueue(mlist, toowner=1) |
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| 452 | elif command == 'request': |
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| 453 | msg.Enqueue(mlist, torequest=1) |
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| 454 | elif command in ('join', 'leave'): |
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| 455 | # TBD: this is a hack! |
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| 456 | if command == 'join': |
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| 457 | msg['Subject'] = 'subscribe' |
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| 458 | else: |
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| 459 | msg['Subject'] = 'unsubscribe' |
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| 460 | msg.Enqueue(mlist, torequest=1) |
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| 461 | |
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| 462 | |
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| 463 | class Options: |
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| 464 | setuid = 1 |
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| 465 | classname = 'PureProxy' |
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| 466 | |
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| 467 | |
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| 468 | def parseargs(): |
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| 469 | global DEBUGSTREAM |
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| 470 | try: |
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| 471 | opts, args = getopt.getopt( |
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| 472 | sys.argv[1:], 'nVhc:d', |
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| 473 | ['class=', 'nosetuid', 'version', 'help', 'debug']) |
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| 474 | except getopt.error, e: |
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| 475 | usage(1, e) |
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| 476 | |
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| 477 | options = Options() |
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| 478 | for opt, arg in opts: |
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| 479 | if opt in ('-h', '--help'): |
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| 480 | usage(0) |
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| 481 | elif opt in ('-V', '--version'): |
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| 482 | print >> sys.stderr, __version__ |
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| 483 | sys.exit(0) |
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| 484 | elif opt in ('-n', '--nosetuid'): |
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| 485 | options.setuid = 0 |
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| 486 | elif opt in ('-c', '--class'): |
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| 487 | options.classname = arg |
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| 488 | elif opt in ('-d', '--debug'): |
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| 489 | DEBUGSTREAM = sys.stderr |
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| 490 | |
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| 491 | # parse the rest of the arguments |
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| 492 | if len(args) < 1: |
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| 493 | localspec = 'localhost:8025' |
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| 494 | remotespec = 'localhost:25' |
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| 495 | elif len(args) < 2: |
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| 496 | localspec = args[0] |
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| 497 | remotespec = 'localhost:25' |
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| 498 | elif len(args) < 3: |
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| 499 | localspec = args[0] |
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| 500 | remotespec = args[1] |
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| 501 | else: |
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| 502 | usage(1, 'Invalid arguments: %s' % COMMASPACE.join(args)) |
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| 503 | |
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| 504 | # split into host/port pairs |
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| 505 | i = localspec.find(':') |
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| 506 | if i < 0: |
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| 507 | usage(1, 'Bad local spec: %s' % localspec) |
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| 508 | options.localhost = localspec[:i] |
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| 509 | try: |
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| 510 | options.localport = int(localspec[i+1:]) |
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| 511 | except ValueError: |
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| 512 | usage(1, 'Bad local port: %s' % localspec) |
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| 513 | i = remotespec.find(':') |
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| 514 | if i < 0: |
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| 515 | usage(1, 'Bad remote spec: %s' % remotespec) |
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| 516 | options.remotehost = remotespec[:i] |
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| 517 | try: |
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| 518 | options.remoteport = int(remotespec[i+1:]) |
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| 519 | except ValueError: |
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| 520 | usage(1, 'Bad remote port: %s' % remotespec) |
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| 521 | return options |
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| 522 | |
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| 523 | |
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| 524 | if __name__ == '__main__': |
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| 525 | options = parseargs() |
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| 526 | # Become nobody |
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| 527 | classname = options.classname |
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| 528 | if "." in classname: |
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| 529 | lastdot = classname.rfind(".") |
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| 530 | mod = __import__(classname[:lastdot], globals(), locals(), [""]) |
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| 531 | classname = classname[lastdot+1:] |
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| 532 | else: |
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| 533 | import __main__ as mod |
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| 534 | class_ = getattr(mod, classname) |
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| 535 | proxy = class_((options.localhost, options.localport), |
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| 536 | (options.remotehost, options.remoteport)) |
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| 537 | if options.setuid: |
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| 538 | try: |
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| 539 | import pwd |
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| 540 | except ImportError: |
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| 541 | print >> sys.stderr, \ |
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| 542 | 'Cannot import module "pwd"; try running with -n option.' |
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| 543 | sys.exit(1) |
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| 544 | nobody = pwd.getpwnam('nobody')[2] |
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| 545 | try: |
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| 546 | os.setuid(nobody) |
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| 547 | except OSError, e: |
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| 548 | if e.errno != errno.EPERM: raise |
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| 549 | print >> sys.stderr, \ |
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| 550 | 'Cannot setuid "nobody"; try running with -n option.' |
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| 551 | sys.exit(1) |
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| 552 | try: |
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| 553 | asyncore.loop() |
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| 554 | except KeyboardInterrupt: |
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| 555 | pass |
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