#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.

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.
    ======== ===================================================================

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:

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):

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

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.