#8739: upgrade smtpd to RFC 5321 and 1870.

smtpd now handles EHLO and has infrastructure for extended smtp command mode.
The SIZE extension is also implemented.  In order to support parameters on
MAIL FROM, the RFC 5322 parser from the email package is used to parse the
address "token".

Logging subclasses things and overrides __init__, so it was necessary to
update those __init__ functions in the logging tests to make the logging tests
pass.

The original suggestion and patch were by Alberto Trevino.  Juhana Jauhiainen
added the --size argument and SIZE parameter support.  Michele Orrù improved
the patch and added more tests.  Dan Boswell conditionalized various bits of
code on whether or not we are in HELO or EHLO mode, as well as some other
improvements and tests.  I finalized the patch and added the address parsing.

7 files changed, 482 insertions, 91 deletions

diff --git a/Doc/library/smtpd.rst b/Doc/library/smtpd.rst
index c391f71..82f4763 100644
--- a/Doc/library/smtpd.rst
+++ b/Doc/library/smtpd.rst
@@ -20,17 +20,24 @@ specific mail-sending strategies.
 Additionally the SMTPChannel may be extended to implement very specific
 interaction behaviour with SMTP clients.
 
+The code supports :RFC:`5321`, plus the :rfc:`1870` SIZE extension.
+
+
 SMTPServer Objects
 ------------------
 
 
-.. class:: SMTPServer(localaddr, remoteaddr)
+.. class:: SMTPServer(localaddr, remoteaddr, data_size_limit=33554432)
 
    Create a new :class:`SMTPServer` object, which binds to local address
    *localaddr*.  It will treat *remoteaddr* as an upstream SMTP relayer.  It
    inherits from :class:`asyncore.dispatcher`, and so will insert itself into
    :mod:`asyncore`'s event loop on instantiation.
 
+   *data_size_limit* specifies the maximum number of bytes that will be
+   accepted in a ``DATA`` command.  A value of ``None`` or ``0`` means no
+   limit.
+
    .. method:: process_message(peer, mailfrom, rcpttos, data)
 
       Raise :exc:`NotImplementedError` exception. Override this in subclasses to
@@ -155,11 +162,15 @@ SMTPChannel Objects
    Command  Action taken
    ======== ===================================================================
    HELO     Accepts the greeting from the client and stores it in
-            :attr:`seen_greeting`.
+            :attr:`seen_greeting`.  Sets server to base command mode.
+   EHLO     Accepts the greeting from the client and stores it in
+            :attr:`seen_greeting`.  Sets server to extended command mode.
    NOOP     Takes no action.
    QUIT     Closes the connection cleanly.
    MAIL     Accepts the "MAIL FROM:" syntax and stores the supplied address as
-            :attr:`mailfrom`.
+            :attr:`mailfrom`.  In extended command mode, accepts the
+            :rfc:`1870` SIZE attribute and responds appropriately based on the
+            value of ``data_size_limit``.
    RCPT     Accepts the "RCPT TO:" syntax and stores the supplied addresses in
             the :attr:`rcpttos` list.
    RSET     Resets the :attr:`mailfrom`, :attr:`rcpttos`, and
@@ -167,4 +178,7 @@ SMTPChannel Objects
    DATA     Sets the internal state to :attr:`DATA` and stores remaining lines
             from the client in :attr:`received_data` until the terminator
             "\r\n.\r\n" is received.
+   HELP     Returns minimal information on command syntax
+   VRFY     Returns code 252 (the server doesn't know if the address is valid)
+   EXPN     Reports that the command is not implemented.
    ======== ===================================================================
diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index 748fcae..778d6d6 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -1,5 +1,5 @@
 #! /usr/bin/env python3
-"""An RFC 2821 smtp proxy.
+"""An RFC 5321 smtp proxy.
 
 Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]]
 
@@ -20,6 +20,11 @@ Options:
         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 via the RFC 1870 SIZE extension.  Defaults to 33554432 bytes.
+
     --debug
     -d
         Turn on debugging prints.
@@ -35,10 +40,9 @@ given then 8025 is used.  If remotehost is not given then `localhost' is used,
 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:
 #
@@ -66,7 +70,7 @@ and if remoteport is not given, then 25 is used.
 #
 # - support mailbox delivery
 # - alias files
-# - ESMTP
+# - Handle more ESMTP extensions
 # - handle error codes from the backend smtpd
 
 import sys
@@ -77,12 +81,14 @@ import time
 import socket
 import asyncore
 import asynchat
+import collections
 from warnings import warn
+from email._header_value_parser import get_addr_spec, get_angle_addr
 
 __all__ = ["SMTPServer","DebuggingServer","PureProxy","MailmanProxy"]
 
 program = sys.argv[0]
-__version__ = 'Python SMTP proxy version 0.2'
+__version__ = 'Python SMTP proxy version 0.3'
 
 
 class Devnull:
@@ -94,9 +100,9 @@ DEBUGSTREAM = Devnull()
 NEWLINE = '\n'
 EMPTYSTRING = ''
 COMMASPACE = ', '
+DATA_SIZE_DEFAULT = 33554432
 
 
-
 def usage(code, msg=''):
     print(__doc__ % globals(), file=sys.stderr)
     if msg:
@@ -104,19 +110,23 @@ def usage(code, msg=''):
     sys.exit(code)
 
 
-
 class SMTPChannel(asynchat.async_chat):
     COMMAND = 0
     DATA = 1
 
-    data_size_limit = 33554432
     command_size_limit = 512
+    command_size_limits = collections.defaultdict(lambda x=command_size_limit: x)
+    command_size_limits.update({
+        'MAIL': command_size_limit + 26,
+        })
+    max_command_size_limit = max(command_size_limits.values())
 
-    def __init__(self, server, conn, addr):
+    def __init__(self, server, conn, addr, data_size_limit=DATA_SIZE_DEFAULT):
         asynchat.async_chat.__init__(self, conn)
         self.smtp_server = server
         self.conn = conn
         self.addr = addr
+        self.data_size_limit = data_size_limit
         self.received_lines = []
         self.smtp_state = self.COMMAND
         self.seen_greeting = ''
@@ -137,6 +147,7 @@ class SMTPChannel(asynchat.async_chat):
         print('Peer:', repr(self.peer), file=DEBUGSTREAM)
         self.push('220 %s %s' % (self.fqdn, __version__))
         self.set_terminator(b'\r\n')
+        self.extended_smtp = False
 
     # properties for backwards-compatibility
     @property
@@ -268,7 +279,7 @@ class SMTPChannel(asynchat.async_chat):
     def collect_incoming_data(self, data):
         limit = None
         if self.smtp_state == self.COMMAND:
-            limit = self.command_size_limit
+            limit = self.max_command_size_limit
         elif self.smtp_state == self.DATA:
             limit = self.data_size_limit
         if limit and self.num_bytes > limit:
@@ -283,11 +294,7 @@ class SMTPChannel(asynchat.async_chat):
         print('Data:', repr(line), file=DEBUGSTREAM)
         self.received_lines = []
         if self.smtp_state == self.COMMAND:
-            if self.num_bytes > self.command_size_limit:
-                self.push('500 Error: line too long')
-                self.num_bytes = 0
-                return
-            self.num_bytes = 0
+            sz, self.num_bytes = self.num_bytes, 0
             if not line:
                 self.push('500 Error: bad syntax')
                 return
@@ -299,9 +306,14 @@ class SMTPChannel(asynchat.async_chat):
             else:
                 command = line[:i].upper()
                 arg = line[i+1:].strip()
+            max_sz = (self.command_size_limits[command]
+                        if self.extended_smtp else self.command_size_limit)
+            if sz > max_sz:
+                self.push('500 Error: line too long')
+                return
             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
@@ -310,12 +322,12 @@ class SMTPChannel(asynchat.async_chat):
                 self.push('451 Internal confusion')
                 self.num_bytes = 0
                 return
-            if self.num_bytes > self.data_size_limit:
+            if self.data_size_limit and self.num_bytes > self.data_size_limit:
                 self.push('552 Error: Too much mail data')
                 self.num_bytes = 0
                 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] == '.':
@@ -333,7 +345,7 @@ class SMTPChannel(asynchat.async_chat):
             self.num_bytes = 0
             self.set_terminator(b'\r\n')
             if not status:
-                self.push('250 Ok')
+                self.push('250 OK')
             else:
                 self.push(status)
 
@@ -346,66 +358,188 @@ class SMTPChannel(asynchat.async_chat):
             self.push('503 Duplicate HELO/EHLO')
         else:
             self.seen_greeting = arg
+            self.extended_smtp = False
             self.push('250 %s' % self.fqdn)
 
+    def smtp_EHLO(self, arg):
+        if not arg:
+            self.push('501 Syntax: EHLO hostname')
+            return
+        if self.seen_greeting:
+            self.push('503 Duplicate HELO/EHLO')
+        else:
+            self.seen_greeting = arg
+            self.extended_smtp = True
+            self.push('250-%s' % self.fqdn)
+            if self.data_size_limit:
+                self.push('250-SIZE %s' % self.data_size_limit)
+            self.push('250 HELP')
+
     def smtp_NOOP(self, arg):
         if arg:
             self.push('501 Syntax: NOOP')
         else:
-            self.push('250 Ok')
+            self.push('250 OK')
 
     def smtp_QUIT(self, arg):
         # args is ignored
         self.push('221 Bye')
         self.close_when_done()
 
-    # factored
-    def __getaddr(self, keyword, arg):
-        address = None
+    def _strip_command_keyword(self, keyword, arg):
         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 <person@dom.com> but watch out
-                # for null address, e.g. <>
-                address = address[1:-1]
-        return address
+            return arg[keylen:].strip()
+        return ''
+
+    def _getaddr(self, arg):
+        if not arg:
+            return '', ''
+        if arg.lstrip().startswith('<'):
+            address, rest = get_angle_addr(arg)
+        else:
+            address, rest = get_addr_spec(arg)
+        if not address:
+            return address, rest
+        return address.addr_spec, rest
+
+    def _getparams(self, params):
+        # Return any parameters that appear to be syntactically valid according
+        # to RFC 1869, ignore all others.  (Postel rule: accept what we can.)
+        params = [param.split('=', 1) for param in params.split()
+                                      if '=' in param]
+        return {k: v for k, v in params if k.isalnum()}
+
+    def smtp_HELP(self, arg):
+        if arg:
+            extended = ' [SP <mail parameters]'
+            lc_arg = arg.upper()
+            if lc_arg == 'EHLO':
+                self.push('250 Syntax: EHLO hostname')
+            elif lc_arg == 'HELO':
+                self.push('250 Syntax: HELO hostname')
+            elif lc_arg == 'MAIL':
+                msg = '250 Syntax: MAIL FROM: <address>'
+                if self.extended_smtp:
+                    msg += extended
+                self.push(msg)
+            elif lc_arg == 'RCPT':
+                msg = '250 Syntax: RCPT TO: <address>'
+                if self.extended_smtp:
+                    msg += extended
+                self.push(msg)
+            elif lc_arg == 'DATA':
+                self.push('250 Syntax: DATA')
+            elif lc_arg == 'RSET':
+                self.push('250 Syntax: RSET')
+            elif lc_arg == 'NOOP':
+                self.push('250 Syntax: NOOP')
+            elif lc_arg == 'QUIT':
+                self.push('250 Syntax: QUIT')
+            elif lc_arg == 'VRFY':
+                self.push('250 Syntax: VRFY <address>')
+            else:
+                self.push('501 Supported commands: EHLO HELO MAIL RCPT '
+                          'DATA RSET NOOP QUIT VRFY')
+        else:
+            self.push('250 Supported commands: EHLO HELO MAIL RCPT DATA '
+                      'RSET NOOP QUIT VRFY')
+
+    def smtp_VRFY(self, arg):
+        if arg:
+            address, params = self._getaddr(arg)
+            if address:
+                self.push('252 Cannot VRFY user, but will accept message '
+                          'and attempt delivery')
+            else:
+                self.push('502 Could not VRFY %s' % arg)
+        else:
+            self.push('501 Syntax: VRFY <address>')
 
     def smtp_MAIL(self, arg):
         if not self.seen_greeting:
             self.push('503 Error: send HELO first');
             return
-
         print('===> MAIL', arg, file=DEBUGSTREAM)
-        address = self.__getaddr('FROM:', arg) if arg else None
+        syntaxerr = '501 Syntax: MAIL FROM: <address>'
+        if self.extended_smtp:
+            syntaxerr += ' [SP <mail-parameters>]'
+        if arg is None:
+            self.push(syntaxerr)
+            return
+        arg = self._strip_command_keyword('FROM:', arg)
+        address, params = self._getaddr(arg)
+        if not address:
+            self.push(syntaxerr)
+            return
+        if not self.extended_smtp and params:
+            self.push(syntaxerr)
+            return
         if not address:
-            self.push('501 Syntax: MAIL FROM:<address>')
+            self.push(syntaxerr)
             return
         if self.mailfrom:
             self.push('503 Error: nested MAIL command')
             return
+        params = self._getparams(params.upper())
+        if params is None:
+            self.push(syntaxerr)
+            return
+        size = params.pop('SIZE', None)
+        if size:
+            if not size.isdigit():
+                self.push(syntaxerr)
+                return
+            elif self.data_size_limit and int(size) > self.data_size_limit:
+                self.push('552 Error: message size exceeds fixed maximum message size')
+                return
+        if len(params.keys()) > 0:
+            self.push('555 MAIL FROM parameters not recognized or not implemented')
+            return
         self.mailfrom = address
         print('sender:', self.mailfrom, file=DEBUGSTREAM)
-        self.push('250 Ok')
+        self.push('250 OK')
 
     def smtp_RCPT(self, arg):
         if not self.seen_greeting:
             self.push('503 Error: send HELO first');
             return
-
         print('===> RCPT', arg, file=DEBUGSTREAM)
         if not self.mailfrom:
             self.push('503 Error: need MAIL command')
             return
-        address = self.__getaddr('TO:', arg) if arg else None
+        syntaxerr = '501 Syntax: RCPT TO: <address>'
+        if self.extended_smtp:
+            syntaxerr += ' [SP <mail-parameters>]'
+        if arg is None:
+            self.push(syntaxerr)
+            return
+        arg = self._strip_command_keyword('TO:', arg)
+        address, params = self._getaddr(arg)
+        if not address:
+            self.push(syntaxerr)
+            return
+        if params:
+            if self.extended_smtp:
+                params = self._getparams(params.upper())
+                if params is None:
+                    self.push(syntaxerr)
+                    return
+            else:
+                self.push(syntaxerr)
+                return
+        if not address:
+            self.push(syntaxerr)
+            return
+        if params and len(params.keys()) > 0:
+            self.push('555 RCPT TO parameters not recognized or not implemented')
+            return
         if not address:
             self.push('501 Syntax: RCPT TO: <address>')
             return
         self.rcpttos.append(address)
         print('recips:', self.rcpttos, file=DEBUGSTREAM)
-        self.push('250 Ok')
+        self.push('250 OK')
 
     def smtp_RSET(self, arg):
         if arg:
@@ -416,13 +550,12 @@ class SMTPChannel(asynchat.async_chat):
         self.rcpttos = []
         self.received_data = ''
         self.smtp_state = self.COMMAND
-        self.push('250 Ok')
+        self.push('250 OK')
 
     def smtp_DATA(self, arg):
         if not self.seen_greeting:
             self.push('503 Error: send HELO first');
             return
-
         if not self.rcpttos:
             self.push('503 Error: need RCPT command')
             return
@@ -433,15 +566,20 @@ class SMTPChannel(asynchat.async_chat):
         self.set_terminator(b'\r\n.\r\n')
         self.push('354 End data with <CR><LF>.<CR><LF>')
 
+    # Commands that have not been implemented
+    def smtp_EXPN(self, arg):
+        self.push('502 EXPN not implemented')
+
 
-
 class SMTPServer(asyncore.dispatcher):
     # SMTPChannel class to use for managing client connections
     channel_class = SMTPChannel
 
-    def __init__(self, localaddr, remoteaddr):
+    def __init__(self, localaddr, remoteaddr,
+                 data_size_limit=DATA_SIZE_DEFAULT):
         self._localaddr = localaddr
         self._remoteaddr = remoteaddr
+        self.data_size_limit = data_size_limit
         asyncore.dispatcher.__init__(self)
         try:
             self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
@@ -459,7 +597,7 @@ class SMTPServer(asyncore.dispatcher):
 
     def handle_accepted(self, conn, addr):
         print('Incoming connection from %s' % repr(addr), file=DEBUGSTREAM)
-        channel = self.channel_class(self, conn, addr)
+        channel = self.channel_class(self, conn, addr, self.data_size_limit)
 
     # API for "doing something useful with the message"
     def process_message(self, peer, mailfrom, rcpttos, data):
@@ -487,7 +625,6 @@ class SMTPServer(asyncore.dispatcher):
         raise NotImplementedError
 
 
-
 class DebuggingServer(SMTPServer):
     # Do something with the gathered message
     def process_message(self, peer, mailfrom, rcpttos, data):
@@ -503,7 +640,6 @@ class DebuggingServer(SMTPServer):
         print('------------ END MESSAGE ------------')
 
 
-
 class PureProxy(SMTPServer):
     def process_message(self, peer, mailfrom, rcpttos, data):
         lines = data.split('\n')
@@ -544,7 +680,6 @@ class PureProxy(SMTPServer):
         return refused
 
 
-
 class MailmanProxy(PureProxy):
     def process_message(self, peer, mailfrom, rcpttos, data):
         from io import StringIO
@@ -623,19 +758,18 @@ class MailmanProxy(PureProxy):
                 msg.Enqueue(mlist, torequest=1)
 
 
-
 class Options:
     setuid = 1
     classname = 'PureProxy'
+    size_limit = None
 
 
-
 def parseargs():
     global DEBUGSTREAM
     try:
         opts, args = getopt.getopt(
-            sys.argv[1:], 'nVhc:d',
-            ['class=', 'nosetuid', 'version', 'help', 'debug'])
+            sys.argv[1:], 'nVhc:s:d',
+            ['class=', 'nosetuid', 'version', 'help', 'size=', 'debug'])
     except getopt.error as e:
         usage(1, e)
 
@@ -652,6 +786,13 @@ def parseargs():
             options.classname = arg
         elif opt in ('-d', '--debug'):
             DEBUGSTREAM = sys.stderr
+        elif opt in ('-s', '--size'):
+            try:
+                int_size = int(arg)
+                options.size_limit = int_size
+            except:
+                print('Invalid size: ' + arg, file=sys.stderr)
+                sys.exit(1)
 
     # parse the rest of the arguments
     if len(args) < 1:
@@ -686,7 +827,6 @@ def parseargs():
     return options
 
 
-
 if __name__ == '__main__':
     options = parseargs()
     # Become nobody
@@ -699,7 +839,8 @@ if __name__ == '__main__':
         import __main__ as mod
     class_ = getattr(mod, classname)
     proxy = class_((options.localhost, options.localport),
-                   (options.remotehost, options.remoteport))
+                   (options.remotehost, options.remoteport),
+                   options.size_limit)
     if options.setuid:
         try:
             import pwd
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 3adeaec..26baf11 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -663,6 +663,7 @@ if threading:
             self.smtp_server = server
             self.conn = conn
             self.addr = addr
+            self.data_size_limit = None
             self.received_lines = []
             self.smtp_state = self.COMMAND
             self.seen_greeting = ''
@@ -682,6 +683,7 @@ if threading:
                 return
             self.push('220 %s %s' % (self.fqdn, smtpd.__version__))
             self.set_terminator(b'\r\n')
+            self.extended_smtp = False
 
 
     class TestSMTPServer(smtpd.SMTPServer):
@@ -709,6 +711,7 @@ if threading:
         def __init__(self, addr, handler, poll_interval, sockmap):
             self._localaddr = addr
             self._remoteaddr = None
+            self.data_size_limit = None
             self.sockmap = sockmap
             asyncore.dispatcher.__init__(self, map=sockmap)
             try:
diff --git a/Lib/test/test_smtpd.py b/Lib/test/test_smtpd.py
index a7dc5f6..dda1941 100644
--- a/Lib/test/test_smtpd.py
+++ b/Lib/test/test_smtpd.py
@@ -1,4 +1,4 @@
-from unittest import TestCase
+import unittest
 from test import support, mock_socket
 import socket
 import io
@@ -26,7 +26,7 @@ class BrokenDummyServer(DummyServer):
         raise DummyDispatcherBroken()
 
 
-class SMTPDServerTest(TestCase):
+class SMTPDServerTest(unittest.TestCase):
     def setUp(self):
         smtpd.socket = asyncore.socket = mock_socket
 
@@ -39,7 +39,7 @@ class SMTPDServerTest(TestCase):
             channel.socket.queue_recv(line)
             channel.handle_read()
 
-        write_line(b'HELO test.example')
+        write_line(b'HELO example')
         write_line(b'MAIL From:eggs@example')
         write_line(b'RCPT To:spam@example')
         write_line(b'DATA')
@@ -50,7 +50,7 @@ class SMTPDServerTest(TestCase):
         asyncore.socket = smtpd.socket = socket
 
 
-class SMTPDChannelTest(TestCase):
+class SMTPDChannelTest(unittest.TestCase):
     def setUp(self):
         smtpd.socket = asyncore.socket = mock_socket
         self.old_debugstream = smtpd.DEBUGSTREAM
@@ -79,36 +79,94 @@ class SMTPDChannelTest(TestCase):
         self.assertEqual(self.channel.socket.last,
                          b'500 Error: bad syntax\r\n')
 
-    def test_EHLO_not_implemented(self):
-        self.write_line(b'EHLO test.example')
+    def test_EHLO(self):
+        self.write_line(b'EHLO example')
+        self.assertEqual(self.channel.socket.last, b'250 HELP\r\n')
+
+    def test_EHLO_bad_syntax(self):
+        self.write_line(b'EHLO')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Syntax: EHLO hostname\r\n')
+
+    def test_EHLO_duplicate(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'EHLO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Duplicate HELO/EHLO\r\n')
+
+    def test_EHLO_HELO_duplicate(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'HELO example')
         self.assertEqual(self.channel.socket.last,
-                         b'502 Error: command "EHLO" not implemented\r\n')
+                         b'503 Duplicate HELO/EHLO\r\n')
 
     def test_HELO(self):
         name = smtpd.socket.getfqdn()
-        self.write_line(b'HELO test.example')
+        self.write_line(b'HELO example')
         self.assertEqual(self.channel.socket.last,
                          '250 {}\r\n'.format(name).encode('ascii'))
 
+    def test_HELO_EHLO_duplicate(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'EHLO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Duplicate HELO/EHLO\r\n')
+
+    def test_HELP(self):
+        self.write_line(b'HELP')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 Supported commands: EHLO HELO MAIL RCPT ' + \
+                         b'DATA RSET NOOP QUIT VRFY\r\n')
+
+    def test_HELP_command(self):
+        self.write_line(b'HELP MAIL')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 Syntax: MAIL FROM: <address>\r\n')
+
+    def test_HELP_command_unknown(self):
+        self.write_line(b'HELP SPAM')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Supported commands: EHLO HELO MAIL RCPT ' + \
+                         b'DATA RSET NOOP QUIT VRFY\r\n')
+
     def test_HELO_bad_syntax(self):
         self.write_line(b'HELO')
         self.assertEqual(self.channel.socket.last,
                          b'501 Syntax: HELO hostname\r\n')
 
     def test_HELO_duplicate(self):
-        self.write_line(b'HELO test.example')
-        self.write_line(b'HELO test.example')
+        self.write_line(b'HELO example')
+        self.write_line(b'HELO example')
         self.assertEqual(self.channel.socket.last,
                          b'503 Duplicate HELO/EHLO\r\n')
 
+    def test_HELO_parameter_rejected_when_extensions_not_enabled(self):
+        self.extended_smtp = False
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:<foo@example.com> SIZE=1234')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Syntax: MAIL FROM: <address>\r\n')
+
+    def test_MAIL_allows_space_after_colon(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:   <foo@example.com>')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 OK\r\n')
+
+    def test_extended_MAIL_allows_space_after_colon(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from:   <foo@example.com> size=20')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 OK\r\n')
+
     def test_NOOP(self):
         self.write_line(b'NOOP')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
 
     def test_HELO_NOOP(self):
         self.write_line(b'HELO example')
         self.write_line(b'NOOP')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
 
     def test_NOOP_bad_syntax(self):
         self.write_line(b'NOOP hi')
@@ -136,15 +194,29 @@ class SMTPDChannelTest(TestCase):
 
     def test_command_too_long(self):
         self.write_line(b'HELO example')
-        self.write_line(b'MAIL from ' +
+        self.write_line(b'MAIL from: ' +
                         b'a' * self.channel.command_size_limit +
                         b'@example')
         self.assertEqual(self.channel.socket.last,
                          b'500 Error: line too long\r\n')
 
-    def test_data_too_long(self):
-        # Small hack. Setting limit to 2K octets here will save us some time.
-        self.channel.data_size_limit = 2048
+    def test_MAIL_command_limit_extended_with_SIZE(self):
+        self.write_line(b'EHLO example')
+        fill_len = self.channel.command_size_limit - len('MAIL from:<@example>')
+        self.write_line(b'MAIL from:<' +
+                        b'a' * fill_len +
+                        b'@example> SIZE=1234')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'MAIL from:<' +
+                        b'a' * (fill_len + 26) +
+                        b'@example> SIZE=1234')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: line too long\r\n')
+
+    def test_data_longer_than_default_data_size_limit(self):
+        # Hack the default so we don't have to generate so much data.
+        self.channel.data_size_limit = 1048
         self.write_line(b'HELO example')
         self.write_line(b'MAIL From:eggs@example')
         self.write_line(b'RCPT To:spam@example')
@@ -154,28 +226,93 @@ class SMTPDChannelTest(TestCase):
         self.assertEqual(self.channel.socket.last,
                          b'552 Error: Too much mail data\r\n')
 
+    def test_MAIL_size_parameter(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> SIZE=512')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 OK\r\n')
+
+    def test_MAIL_invalid_size_parameter(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> SIZE=invalid')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: MAIL FROM: <address> [SP <mail-parameters>]\r\n')
+
+    def test_MAIL_RCPT_unknown_parameters(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> ham=green')
+        self.assertEqual(self.channel.socket.last,
+            b'555 MAIL FROM parameters not recognized or not implemented\r\n')
+
+        self.write_line(b'MAIL FROM:<eggs@example>')
+        self.write_line(b'RCPT TO:<eggs@example> ham=green')
+        self.assertEqual(self.channel.socket.last,
+            b'555 RCPT TO parameters not recognized or not implemented\r\n')
+
+    def test_MAIL_size_parameter_larger_than_default_data_size_limit(self):
+        self.channel.data_size_limit = 1048
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> SIZE=2096')
+        self.assertEqual(self.channel.socket.last,
+            b'552 Error: message size exceeds fixed maximum message size\r\n')
+
     def test_need_MAIL(self):
         self.write_line(b'HELO example')
         self.write_line(b'RCPT to:spam@example')
         self.assertEqual(self.channel.socket.last,
             b'503 Error: need MAIL command\r\n')
 
-    def test_MAIL_syntax(self):
+    def test_MAIL_syntax_HELO(self):
         self.write_line(b'HELO example')
         self.write_line(b'MAIL from eggs@example')
         self.assertEqual(self.channel.socket.last,
-            b'501 Syntax: MAIL FROM:<address>\r\n')
+            b'501 Syntax: MAIL FROM: <address>\r\n')
 
-    def test_MAIL_missing_from(self):
+    def test_MAIL_syntax_EHLO(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: MAIL FROM: <address> [SP <mail-parameters>]\r\n')
+
+    def test_MAIL_missing_address(self):
         self.write_line(b'HELO example')
         self.write_line(b'MAIL from:')
         self.assertEqual(self.channel.socket.last,
-            b'501 Syntax: MAIL FROM:<address>\r\n')
+            b'501 Syntax: MAIL FROM: <address>\r\n')
 
     def test_MAIL_chevrons(self):
         self.write_line(b'HELO example')
         self.write_line(b'MAIL from:<eggs@example>')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_MAIL_empty_chevrons(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from:<>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_MAIL_quoted_localpart(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: <"Fred Blogs"@example.com>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_MAIL_quoted_localpart_no_angles(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: "Fred Blogs"@example.com')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_MAIL_quoted_localpart_with_size(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: <"Fred Blogs"@example.com> SIZE=1000')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_MAIL_quoted_localpart_with_size_no_angles(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: "Fred Blogs"@example.com SIZE=1000')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
 
     def test_nested_MAIL(self):
         self.write_line(b'HELO example')
@@ -184,6 +321,22 @@ class SMTPDChannelTest(TestCase):
         self.assertEqual(self.channel.socket.last,
             b'503 Error: nested MAIL command\r\n')
 
+    def test_VRFY(self):
+        self.write_line(b'VRFY eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'252 Cannot VRFY user, but will accept message and attempt ' + \
+            b'delivery\r\n')
+
+    def test_VRFY_syntax(self):
+        self.write_line(b'VRFY')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: VRFY <address>\r\n')
+
+    def test_EXPN_not_implemented(self):
+        self.write_line(b'EXPN')
+        self.assertEqual(self.channel.socket.last,
+            b'502 EXPN not implemented\r\n')
+
     def test_no_HELO_MAIL(self):
         self.write_line(b'MAIL from:<foo@example.com>')
         self.assertEqual(self.channel.socket.last,
@@ -196,13 +349,26 @@ class SMTPDChannelTest(TestCase):
         self.assertEqual(self.channel.socket.last,
             b'503 Error: need RCPT command\r\n')
 
-    def test_RCPT_syntax(self):
+    def test_RCPT_syntax_HELO(self):
         self.write_line(b'HELO example')
-        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'MAIL From: eggs@example')
         self.write_line(b'RCPT to eggs@example')
         self.assertEqual(self.channel.socket.last,
             b'501 Syntax: RCPT TO: <address>\r\n')
 
+    def test_RCPT_syntax_EHLO(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL From: eggs@example')
+        self.write_line(b'RCPT to eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: RCPT TO: <address> [SP <mail-parameters>]\r\n')
+
+    def test_RCPT_lowercase_to_OK(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From: eggs@example')
+        self.write_line(b'RCPT to: <eggs@example>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
     def test_no_HELO_RCPT(self):
         self.write_line(b'RCPT to eggs@example')
         self.assertEqual(self.channel.socket.last,
@@ -211,15 +377,15 @@ class SMTPDChannelTest(TestCase):
     def test_data_dialog(self):
         self.write_line(b'HELO example')
         self.write_line(b'MAIL From:eggs@example')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
         self.write_line(b'RCPT To:spam@example')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
 
         self.write_line(b'DATA')
         self.assertEqual(self.channel.socket.last,
             b'354 End data with <CR><LF>.<CR><LF>\r\n')
         self.write_line(b'data\r\nmore\r\n.')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
         self.assertEqual(self.server.messages,
             [('peer', 'eggs@example', ['spam@example'], 'data\nmore')])
 
@@ -267,7 +433,7 @@ class SMTPDChannelTest(TestCase):
         self.write_line(b'MAIL From:eggs@example')
         self.write_line(b'RCPT To:spam@example')
         self.write_line(b'RSET')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
         self.write_line(b'MAIL From:foo@example')
         self.write_line(b'RCPT To:eggs@example')
         self.write_line(b'DATA')
@@ -278,12 +444,18 @@ class SMTPDChannelTest(TestCase):
     def test_HELO_RSET(self):
         self.write_line(b'HELO example')
         self.write_line(b'RSET')
-        self.assertEqual(self.channel.socket.last, b'250 Ok\r\n')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
 
     def test_RSET_syntax(self):
         self.write_line(b'RSET hi')
         self.assertEqual(self.channel.socket.last, b'501 Syntax: RSET\r\n')
 
+    def test_unknown_command(self):
+        self.write_line(b'UNKNOWN_CMD')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: command "UNKNOWN_CMD" not ' + \
+                         b'recognized\r\n')
+
     def test_attribute_deprecations(self):
         with support.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__server
@@ -330,8 +502,54 @@ class SMTPDChannelTest(TestCase):
         with support.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__addr = 'spam'
 
-def test_main():
-    support.run_unittest(SMTPDServerTest, SMTPDChannelTest)
+
+class SMTPDChannelWithDataSizeLimitTest(unittest.TestCase):
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer('a', 'b')
+        conn, addr = self.server.accept()
+        # Set DATA size limit to 32 bytes for easy testing
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr, 32)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+
+    def write_line(self, line):
+        self.channel.socket.queue_recv(line)
+        self.channel.handle_read()
+
+    def test_data_limit_dialog(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.write_line(b'RCPT To:spam@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last,
+            b'354 End data with <CR><LF>.<CR><LF>\r\n')
+        self.write_line(b'data\r\nmore\r\n.')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.server.messages,
+            [('peer', 'eggs@example', ['spam@example'], 'data\nmore')])
+
+    def test_data_limit_dialog_too_much_data(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.write_line(b'RCPT To:spam@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last,
+            b'354 End data with <CR><LF>.<CR><LF>\r\n')
+        self.write_line(b'This message is longer than 32 bytes\r\n.')
+        self.assertEqual(self.channel.socket.last,
+                         b'552 Error: Too much mail data\r\n')
+
 
 if __name__ == "__main__":
-    test_main()
+    unittest.main()
diff --git a/Lib/test/test_smtplib.py b/Lib/test/test_smtplib.py
index 18dde2f..befc49e 100644
--- a/Lib/test/test_smtplib.py
+++ b/Lib/test/test_smtplib.py
@@ -229,13 +229,13 @@ class DebuggingServerTests(unittest.TestCase):
 
     def testNOOP(self):
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
-        expected = (250, b'Ok')
+        expected = (250, b'OK')
         self.assertEqual(smtp.noop(), expected)
         smtp.quit()
 
     def testRSET(self):
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
-        expected = (250, b'Ok')
+        expected = (250, b'OK')
         self.assertEqual(smtp.rset(), expected)
         smtp.quit()
 
@@ -246,10 +246,18 @@ class DebuggingServerTests(unittest.TestCase):
         self.assertEqual(smtp.ehlo(), expected)
         smtp.quit()
 
+    def testNotImplemented(self):
+        # EXPN isn't implemented in DebuggingServer
+        smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
+        expected = (502, b'EXPN not implemented')
+        smtp.putcmd('EXPN')
+        self.assertEqual(smtp.getreply(), expected)
+        smtp.quit()
+
     def testVRFY(self):
-        # VRFY isn't implemented in DebuggingServer
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
-        expected = (502, b'Error: command "VRFY" not implemented')
+        expected = (252, b'Cannot VRFY user, but will accept message ' + \
+                         b'and attempt delivery')
         self.assertEqual(smtp.vrfy('nobody@nowhere.com'), expected)
         self.assertEqual(smtp.verify('nobody@nowhere.com'), expected)
         smtp.quit()
@@ -265,7 +273,8 @@ class DebuggingServerTests(unittest.TestCase):
 
     def testHELP(self):
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
-        self.assertEqual(smtp.help(), b'Error: command "HELP" not implemented')
+        self.assertEqual(smtp.help(), b'Supported commands: EHLO HELO MAIL ' + \
+                                      b'RCPT DATA RSET NOOP QUIT VRFY')
         smtp.quit()
 
     def testSend(self):
diff --git a/Misc/ACKS b/Misc/ACKS
index 16f55ea..371668f 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -112,6 +112,7 @@ Gregory Bond
 Matias Bordese
 Jurjen Bos
 Peter Bosch
+Dan Boswell
 Eric Bouck
 Thierry Bousch
 Sebastian Boving
@@ -494,6 +495,7 @@ Geert Jansen
 Jack Jansen
 Bill Janssen
 Thomas Jarosch
+Juhana Jauhiainen
 Zbigniew Jędrzejewski-Szmek
 Julien Jehannet
 Drew Jenkins
@@ -1039,6 +1041,7 @@ Sandro Tosi
 Richard Townsend
 David Townshend
 Laurence Tratt
+Alberto Trevino
 Matthias Troffaes
 John Tromp
 Jason Trowbridge
diff --git a/Misc/NEWS b/Misc/NEWS
index 4f20446..50060e5 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -46,6 +46,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #8739: Updated smtpd to support RFC 5321, and added support for the
+  RFC 1870 SIZE extension.
+
 - Issue #665194: Added a localtime function to email.utils to provide an
   aware local datetime for use in setting Date headers.