--- smtpd_orig.py 2010-05-10 22:53:42.926320614 -0600 +++ smtpd.py 2010-05-20 07:31:47.885944295 -0600 @@ -1,5 +1,5 @@ #! /usr/bin/env python -"""An RFC 2821 smtp proxy. +"""An RFC 5321 smtp proxy. Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]] @@ -20,6 +20,11 @@ Use `classname' as the concrete SMTP proxy class. Uses `PureProxy' by default. + --size limit + -s limit + Restrict the total size of the incoming message to "limit" number of + bytes. Defaults to 0 bytes by default (no limit). + --debug -d Turn on debugging prints. @@ -35,10 +40,9 @@ and if remoteport is not given, then 25 is used. """ - # Overview: # -# This file implements the minimal SMTP protocol as defined in RFC 821. It +# This file implements the minimal SMTP protocol as defined in RFC 5321. It # has a hierarchy of classes which implement the backend functionality for the # smtpd. A number of classes are provided: # @@ -59,15 +63,18 @@ # gets forwarded to a real backend smtpd, as with PureProxy. Again, errors # are not handled correctly yet. # -# Please note that this script requires Python 2.0 +# Please note that this script requires Python 3.0 # # Author: Barry Warsaw # +# Contributors: +# Alberto Trevino +# # TODO: # # - support mailbox delivery # - alias files -# - ESMTP +# - Handle more ESMTP extensions # - handle error codes from the backend smtpd import sys @@ -82,7 +89,7 @@ __all__ = ["SMTPServer","DebuggingServer","PureProxy","MailmanProxy"] program = sys.argv[0] -__version__ = 'Python SMTP proxy version 0.2' +__version__ = 'Python SMTP proxy version 0.21' class Devnull: @@ -96,7 +103,6 @@ COMMASPACE = ', ' - def usage(code, msg=''): print(__doc__ % globals(), file=sys.stderr) if msg: @@ -104,16 +110,16 @@ sys.exit(code) - class SMTPChannel(asynchat.async_chat): COMMAND = 0 DATA = 1 - def __init__(self, server, conn, addr): + def __init__(self, server, conn, addr, size): asynchat.async_chat.__init__(self, conn) self.__server = server self.__conn = conn self.__addr = addr + self.__size = size self.__line = [] self.__state = self.COMMAND self.__greeting = 0 @@ -122,6 +128,7 @@ self.__data = '' self.__fqdn = socket.getfqdn() self.__peer = conn.getpeername() + self.__8bitmime = False print('Peer:', repr(self.__peer), file=DEBUGSTREAM) self.push('220 %s %s' % (self.__fqdn, __version__)) self.set_terminator(b'\r\n') @@ -153,7 +160,7 @@ arg = line[i+1:].strip() method = getattr(self, 'smtp_' + command, None) if not method: - self.push('502 Error: command "%s" not implemented' % command) + self.push('500 Error: command "%s" not recognized' % command) return method(arg) return @@ -162,7 +169,7 @@ self.push('451 Internal confusion') return # Remove extraneous carriage returns and de-transparency according - # to RFC 821, Section 4.5.2. + # to RFC 5321, Section 4.5.2. data = [] for text in line.split('\r\n'): if text and text[0] == '.': @@ -170,18 +177,39 @@ else: data.append(text) self.__data = NEWLINE.join(data) - status = self.__server.process_message(self.__peer, - self.__mailfrom, - self.__rcpttos, - self.__data) - self.__rcpttos = [] - self.__mailfrom = None - self.__state = self.COMMAND - self.set_terminator(b'\r\n') - if not status: - self.push('250 Ok') + + # Enforce data size limit + if self.__size == 0 or len(self.__data) <= self.__size: + status = self.__server.process_message(self.__peer, + self.__mailfrom, + self.__rcpttos, + self.__data) + self.__rcpttos = [] + self.__mailfrom = None + self.__state = self.COMMAND + self.set_terminator(b'\r\n') + if not status: + self.push('250 Ok') + else: + self.push(status) else: - self.push(status) + self.__state = self.COMMAND + self.set_terminator(b'\r\n') + self.push('552 Too much mail data') + + # factored + def __getaddr(self, keyword, arg): + address = None + keylen = len(keyword) + if arg[:keylen].upper() == keyword: + address = arg[keylen:].strip() + if not address: + pass + elif address[0] == '<' and address[-1] == '>' and address != '<>': + # Addresses can be in the form but watch out + # for null address, e.g. <> + address = address[1:-1] + return address # SMTP and ESMTP commands def smtp_HELO(self, arg): @@ -193,7 +221,21 @@ else: self.__greeting = arg self.push('250 %s' % self.__fqdn) - + + def smtp_EHLO(self, arg): + if not arg: + self.push('501 Syntax: EHLO hostname') + return + if self.__greeting: + self.push('503 Duplicate HELO/EHLO') + else: + self.__greeting = arg + self.push('250-%s' % self.__fqdn) + self.push('250-8BITMIME') + if self.__size > 0: + self.push('250-SIZE %s' % self.__size) + self.push('250 HELP') + def smtp_NOOP(self, arg): if arg: self.push('501 Syntax: NOOP') @@ -204,20 +246,49 @@ # args is ignored self.push('221 Bye') self.close_when_done() + + def smtp_8BITMIME(self, arg): + # There is nothing in this code that forces 7 bits, so it seems OK + # to simply accept this command; its value is saved for future use; + # args is ignored + self.__8bitmime = True + self.push('250 Ok') + + def smtp_HELP(self, arg): + if arg: + lc_arg = arg.upper() + if lc_arg == 'EHLO': + self.push('250 EHLO your_fqdn') + elif lc_arg == 'HELO': + self.push('250 HELO your_fqdn') + elif lc_arg == 'MAIL': + self.push('250 MAIL FROM:') + elif lc_arg == 'RCPT': + self.push('250 RCPT TO:' and address != '<>': - # Addresses can be in the form but watch out - # for null address, e.g. <> - address = address[1:-1] - return address + def smtp_VRFY(self, arg): + address = self.__getaddr('', arg) if arg else None + if address: + self.push('252 Cannot VRFY user, but will accept message and ' + \ + 'attempt delivery') + else: + self.push('502 Could not VRFY %s' % arg) def smtp_MAIL(self, arg): print('===> MAIL', arg, file=DEBUGSTREAM) @@ -266,13 +337,17 @@ self.__state = self.DATA self.set_terminator(b'\r\n.\r\n') self.push('354 End data with .') + + # Commands that have not been implemented + def smtp_EXPN(self, arg): + self.push('502 EXPN not implemented') - class SMTPServer(asyncore.dispatcher): - def __init__(self, localaddr, remoteaddr): + def __init__(self, localaddr, remoteaddr, size): self._localaddr = localaddr self._remoteaddr = remoteaddr + self._size = size asyncore.dispatcher.__init__(self) self.create_socket(socket.AF_INET, socket.SOCK_STREAM) # try to re-use a server port if possible @@ -286,7 +361,7 @@ def handle_accept(self): conn, addr = self.accept() print('Incoming connection from %s' % repr(addr), file=DEBUGSTREAM) - channel = SMTPChannel(self, conn, addr) + channel = SMTPChannel(self, conn, addr, self._size) # API for "doing something useful with the message" def process_message(self, peer, mailfrom, rcpttos, data): @@ -314,7 +389,6 @@ raise NotImplementedError - class DebuggingServer(SMTPServer): # Do something with the gathered message def process_message(self, peer, mailfrom, rcpttos, data): @@ -330,7 +404,6 @@ print('------------ END MESSAGE ------------') - class PureProxy(SMTPServer): def process_message(self, peer, mailfrom, rcpttos, data): lines = data.split('\n') @@ -371,7 +444,6 @@ return refused - class MailmanProxy(PureProxy): def process_message(self, peer, mailfrom, rcpttos, data): from io import StringIO @@ -450,19 +522,18 @@ msg.Enqueue(mlist, torequest=1) - class Options: setuid = 1 classname = 'PureProxy' + size = 0 - def parseargs(): global DEBUGSTREAM try: opts, args = getopt.getopt( - sys.argv[1:], 'nVhc:d', - ['class=', 'nosetuid', 'version', 'help', 'debug']) + sys.argv[1:], 'nVhc:ds:', + ['class=', 'nosetuid', 'version', 'help', 'debug', 'size=']) except getopt.error as e: usage(1, e) @@ -479,6 +550,13 @@ options.classname = arg elif opt in ('-d', '--debug'): DEBUGSTREAM = sys.stderr + elif opt in ('-s', '--size'): + try: + int_size = int(arg) + options.size = int_size + except: + print('Invalid size: ' + arg, file=sys.stderr) + sys.exit(1) # parse the rest of the arguments if len(args) < 1: @@ -513,7 +591,6 @@ return options - if __name__ == '__main__': options = parseargs() # Become nobody @@ -521,14 +598,16 @@ try: import pwd except ImportError: - print('Cannot import module "pwd"; try running with -n option.', file=sys.stderr) + print('Cannot import module "pwd"; try running with -n option.', \ + file=sys.stderr) sys.exit(1) nobody = pwd.getpwnam('nobody')[2] try: os.setuid(nobody) except OSError as e: if e.errno != errno.EPERM: raise - print('Cannot setuid "nobody"; try running with -n option.', file=sys.stderr) + print('Cannot setuid "nobody"; try running with -n option.', \ + file=sys.stderr) sys.exit(1) classname = options.classname if "." in classname: @@ -539,7 +618,8 @@ import __main__ as mod class_ = getattr(mod, classname) proxy = class_((options.localhost, options.localport), - (options.remotehost, options.remoteport)) + (options.remotehost, options.remoteport), + options.size) try: asyncore.loop() except KeyboardInterrupt: