# relay.py # # # Copyright (C) 2005-2006 Daniel Burrows # # This program 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. # # This program 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 this program; see the file COPYING. If not, write to # the Free Software Foundation, Inc., 59 Temple Place - Suite 330, # Boston, MA 02111-1307, USA. # # Code to relay a single message off the system. import os import sys from cStringIO import StringIO import defaults import email.Generator import email.Utils import lock import smtplib import random import re import socket # For socket.error class RelayError(Exception): pass def relay(m, to_addrs, configenv, substvars, getpass): """Perform SMTP relaying on the Message object m with the given configuration in effect. This expects that all configuration variables have defaults specified in configenv. The 'getpass' parameter is a callable object to be used to retrieve the user's password; it will be invoked as getpass(prompt). The following configuration variables are used: default_from_address - the address used to replace missing From: addresses, or '' to require a From address. default_envelope_from - the address used to replace missing envelope-from addresses. If set to '', default_from_address is used. rewrite_unqualified - if set, unqualified From and envelope-from addresses are replaced with the default address (or an error is signalled if there is no default address). ssl - if True, put the connection into SSL mode via StartTLS. smtp_relay - the SMTP server to which email should be sent. You may append ':port' to the message to set the port number (which otherwise defaults to 25). login - if set and nonempty, this string value is used as the user's login name on the SMTP server. If unset or empty, no authentication is performed. password - if nonempty, this string value is used as the user's password in authentication; otherwise, the program attempts to query the user using getpass(). debug_smtp - if true, log all communications with the SMTP server. mda - if nonempty, unqualified To addresses will be passed as arguments to this string value. In addition to the standard expansion variables, the variable $RECIPIENT is bound to the user receiving the email. If empty, delivery to unqualified addresses will simply fail. NOTE: if you are not root, this had better be a suid mail program, or delivery to unqualified local addresses will FAIL.""" def prepare_message(m): """Prepare a message to be sent via SMTP by flattening it without mangling the From address.""" tmpf = StringIO() g = email.Generator.Generator(tmpf, mangle_from_ = False) g.flatten(m) return tmpf.getvalue() def deliver_unqualified(m, recipient): """Deliver a message to an unqualified address (i.e., a local user) by passing it off to an MDA. Throws RelayError if the MDA can't be found or if it doesn't exit successfully.""" if recipient == '$USER' or recipient == '$LOGNAME': recipient = substvars.get('USER', recipient) tmpsubst = substvars.copy() tmpsubst['TO'] = re.escape(recipient) mda = configenv.get_value(identity, 'mda', tmpsubst) # Could default here, but that risks losing mail if the MDA is # badly configured. if mda == '': raise RelayError('Cannot deliver to %s: mda not set in the configuration file.' % recipient) if debug_smtp: print 'Executing "%s" to deliver mail'%mda try: fp = os.popen(mda, 'w') # Speed up delivery by only converting the message to a # string once. fp.write(msgtext) rval = fp.close() except (OSError, IOError),e: raise RelayError('Error delivering message via MDA: %s'%e) if rval <> None: if not os.WIFEXITED(rval): coredumpstr = '' if os.WCOREDUMP(rval): coredumpstr = ' (core dumped)' if os.WIFSIGNALED(rval): raise RelayError('MDA terminated by signal %d%s'%(os.WTERMSIG(rval), coredumpstr)) else: raise RelayError('The MDA stopped and I don\'t know why; exit status was 0x%x'%rval) elif os.WEXITSTATUS(rval) <> 0: raise RelayError('MDA exited abnormally (status %d)'%os.WEXITSTATUS(rval)) if len(to_addrs) == 0: raise RelayError('No recipient addresses; unable to relay message') identity = m.get('From', None) # If the From header is missing, set it from the envelope header. if identity == None and m.get_unixfrom() <> None: identity = m.get_unixfrom() m['From'] = identity substvars = substvars.copy() if identity <> None: substvars['FROM'] = identity substvars['TO'] = m.get('To', '') substvars['SUBJECT'] = m.get('Subject', '') if identity <> None: safeidentity = identity else: safeidentity = '' # Maybe rewrite a missing or unqualified From: address. rewrite_unqualified = configenv.get_value(safeidentity, 'rewrite_unqualified', substvars) # Maybe rewrite a missing or unqualified From address if identity == None or identity == '' or (rewrite_unqualified and '@' not in identity): default_from = configenv.get_value(safeidentity, 'default_from_address', substvars) if default_from == '': if identity == None or identity == '': raise RelayError('Message lacks a From address and default_from_address is unset; unable to proceed.') else: raise RelayError('Need to rewrite the unqualified address "%s", but default_from_address is unset; unable to proceed.'%identity) if identity == None: m['From'] = default_from else: m.replace_header('From', default_from) identity = default_from substvars['FROM'] = identity rewrite_unqualified = configenv.get_value(safeidentity, 'rewrite_unqualified', substvars) # Maybe rewrite a missing or unqualified envelope-from address envelope_from = m.get_unixfrom() if envelope_from == None or envelope_from == '' or (rewrite_unqualified and '@' not in envelope_from): envelope_from = configenv.get_value(identity, 'default_envelope_from', substvars) if envelope_from == '': envelope_from = configenv.get_value(identity, 'default_from_address', substvars) if envelope_from == '': raise RelayError('Need to rewrite the envelope-from, but no default address is specified.') m.set_unixfrom(envelope_from) # Find the relaying server. ssl = configenv.get_value(identity, 'ssl', substvars) smtp_relay = configenv.get_value(identity, 'smtp_relay', substvars) login = configenv.get_value(identity, 'login', substvars) debug_smtp = configenv.get_value(identity, 'debug_smtp', substvars) msgtext = prepare_message(m) unqualified = [] qualified = [] # Deliver to unqualified addresses first, so at least we don't # pollute the Internet with a partial delivery ;-). for addr in to_addrs: realname, realaddr = email.Utils.parseaddr(addr) if '@' not in realaddr: unqualified.append(realaddr) else: qualified.append(addr) for realaddr in unqualified: deliver_unqualified(m, realaddr) if qualified == []: return # SMTP relaying follows: if ':' in smtp_relay: smtp_relay_host = smtp_relay[:smtp_relay.find(':')] else: smtp_relay_host = smtp_relay if login <> '': password = configenv.get_value(identity, 'password', substvars) if password == '': password = getpass('Enter the password for %s@%s'%(login, smtp_relay_host)) try: conn = smtplib.SMTP() conn.set_debuglevel(debug_smtp) conn.connect(smtp_relay) if ssl: if not conn.has_extn('STARTTLS'): raise RelayError('SSL was requested, but the relay server does not support STARTTLS.') rval, msg = conn.starttls() if rval <> 220: raise RelayError('Unable to enable secure data transmission; server said "%s"'%msg) if login <> '': conn.login(login, password) conn.sendmail(envelope_from, qualified, msgtext) except smtplib.SMTPException, e: raise RelayError('SMTP error: %s'%e) except socket.error, e: raise RelayError('Network error: %s'%e[1])