smtplib mishandles SMTP disconnects

[1af41a4c-c5ec-4789-95e6-64c09c7f7f3c]

BPO	487310
Nosy	@gvanrossum, @warsaw
Files	smtplib.txt: Patch to smtplib

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields: ```python assignee = 'https://github.com/warsaw' closed_at = created_at = labels = ['library'] title = 'smtplib mishandles SMTP disconnects' updated_at = user = 'https://bugs.python.org/majid' ``` bugs.python.org fields: ```python activity = actor = 'barry' assignee = 'barry' closed = True closed_date = None closer = None components = ['Library (Lib)'] creation = creator = 'majid' dependencies = [] files = ['223'] hgrepos = [] issue_num = 487310 keywords = [] message_count = 6.0 messages = ['7886', '7887', '7888', '7889', '7890', '7891'] nosy_count = 3.0 nosy_names = ['gvanrossum', 'barry', 'majid'] pr_nums = [] priority = 'normal' resolution = 'accepted' stage = None status = 'closed' superseder = None type = None url = 'https://bugs.python.org/issue487310' versions = [] ```

[1af41a4c-c5ec-4789-95e6-64c09c7f7f3c]

smtplib handles SMTP disconnects (e.g. timeouts) inconsistently. The smtplib.SMTP.send() method does not reset self.file on a socket error, unlike getreply(), and thus a close() is necessary for in one case but not in the other.

Recommendation: have smtplib.SMTP.send() call close() on socket.error just as smtplib.SMTP.getreply() does on EOF on self.file.

In the following test case, I have set the SMTP timeout on my local machine to 10 seconds:

Python 2.1.1 (#1, Nov  7 2001, 16:18:10)
[GCC 2.95.3 20010315 (release)] on sunos5
Type "copyright", "credits" or "license" for more
information.
>>> import smtplib
>>> s = smtplib.SMTP('localhost', 25)
>>> import time
>>> time.sleep(10)
>>> s.sendmail('fmajid@kefta.com', 'fmajid@kefta.com',
'...')
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python2.1/smtplib.py", line 469,
in sendmail
    (code,resp) = self.helo()
  File "/usr/local/lib/python2.1/smtplib.py", line 305,
in helo
    self.putcmd("helo", socket.getfqdn())
  File "/usr/local/lib/python2.1/smtplib.py", line 249,
in putcmd
    self.send(str)
  File "/usr/local/lib/python2.1/smtplib.py", line 239,
in send
    raise SMTPServerDisconnected('Server not connected')
smtplib.SMTPServerDisconnected: Server not connected
>>> s.connect('localhost', 25)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python2.1/smtplib.py", line 226,
in connect
    (code,msg)=self.getreply()
  File "/usr/local/lib/python2.1/smtplib.py", line 271,
in getreply
    raise SMTPServerDisconnected("Connection
unexpectedly closed")
smtplib.SMTPServerDisconnected: Connection unexpectedly
closed
>>> s.connect('localhost', 25)
(220, 'bayazid.kefta.com ESMTP Postfix')

[1af41a4c-c5ec-4789-95e6-64c09c7f7f3c]

Logged In: YES user_id=110477

I forgot to mention a workaround: if you catch SMTPServerDisconnected, call self.close(). The operation is idempotent so it isn't a problem if you do it twice, for instance if the exception occurs in getreply().

[gvanrossum]

Logged In: YES user_id=6380

Can you please supply a patch?

Upload a context diff, don't forget to check the file upload checkbox.

[1af41a4c-c5ec-4789-95e6-64c09c7f7f3c]

Logged In: YES user_id=110477

I am attaching a patch that calls self.close() before raising the SMTPServerDisconnected exception.

There does not seem to be a standard unit test for smtplib. I have run this patch through a unit test of my own that exercises smtplib. I don't have a way to test a broken MTA that disconnects on EHLO, however.

[1af41a4c-c5ec-4789-95e6-64c09c7f7f3c]

Logged In: YES user_id=110477

Oops... forgot to check the checkbox for attachments.

[warsaw]

Logged In: YES user_id=12800

Patch seems good to me, so I'm going to apply it to smtplib.py for both 2.2c1 and 2.2 trunk.

Yes, it would be very nice to have a test suite for smtplib.py. I have a start of one in Mailman that uses smtpd.py. If you think it's worthwhile, why don't you upload your test suite to the patch tracker, assign it to me, and I'll merge it with what I have.

This would be for Python 2.3.