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# Copyright (C) 2016 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman 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 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman 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
# GNU Mailman. If not, see <http://www.gnu.org/licenses/>.
"""Do DMARC Munge From and Wrap Message actions."""
import re
import copy
import logging
from email.header import Header
from email.mime.message import MIMEMessage
from email.mime.text import MIMEText
from email.utils import formataddr, getaddresses, make_msgid
from mailman import public
from mailman.core.i18n import _
from mailman.interfaces.handler import IHandler
from mailman.interfaces.mailinglist import (
DMARCModerationAction, FromIsList, ReplyToMunging)
from mailman.utilities.string import wrap
from zope.interface import implementer
log = logging.getLogger('mailman.error')
COMMASPACE = ', '
MAXLINELEN = 78
NONASCII = re.compile('[^\s!-~]')
# Headers from the original that we want to keep in the wrapper. These are
# actually regexps matched with re.match so they match anything that starts
# with the given string unless they end with '$'.
KEEPERS = ('archived-at',
'date',
'in-reply-to',
'list-',
'precedence',
'references',
'subject',
'to',
'x-mailman-',
)
@public
def uheader(mlist, s, header_name=None, continuation_ws='\t', maxlinelen=None):
"""Get the charset to encode the string in.
Then search if there is any non-ascii character is in the string. If
there is and the charset is us-ascii then we use iso-8859-1 instead. If
the string is ascii only we use 'us-ascii' if another charset is
specified.
If the header contains a newline, truncate it (see GL#273).
"""
charset = mlist.preferred_language.charset
if NONASCII.search(s):
# use list charset but ...
if charset == 'us-ascii':
charset = 'iso-8859-1'
else:
# there is no non-ascii so ...
charset = 'us-ascii'
if '\n' in s:
s = '{} [...]'.format(s.split('\n')[0])
log.warning('Header {} contains a newline, truncating it.'.format(
header_name, s))
return Header(s, charset, maxlinelen, header_name, continuation_ws)
def munged_headers(mlist, msg, msgdata):
# Be as robust as possible here.
faddrs = getaddresses(msg.get_all('from', []))
# Strip the nulls and bad emails.
faddrs = [x for x in faddrs if x[1].find('@') > 0]
if len(faddrs) == 1:
realname, email = o_from = faddrs[0]
else:
# No From: or multiple addresses. Just punt and take
# the get_sender result.
realname = ''
email = msgdata['original_sender']
o_from = (realname, email)
if not realname:
member = mlist.members.get_member(email)
if member:
realname = member.display_name or email
else:
realname = email
# Remove domain from realname if it looks like an email address
realname = re.sub(r'@([^ .]+\.)+[^ .]+$', '---', realname)
# RFC 2047 encode realname if necessary.
realname = str(uheader(mlist, realname))
lrn = mlist.display_name # noqa F841
retn = [('From', formataddr((_('$realname via $lrn'),
mlist.posting_address)))]
# We've made the munged From:. Now put the original in Reply-To: or Cc:
if mlist.reply_goes_to_list == ReplyToMunging.no_munging:
# Add original from to Reply-To:
add_to = 'Reply-To'
else:
# Add original from to Cc:
add_to = 'Cc'
orig = getaddresses(msg.get_all(add_to, []))
if o_from[1] not in [x[1] for x in orig]:
orig.append(o_from)
retn.append((add_to, COMMASPACE.join([formataddr(x) for x in orig])))
return retn
def munge_from(mlist, msg, msgdata):
for k, v in munged_headers(mlist, msg, msgdata):
del msg[k]
msg[k] = v
return
def wrap_message(mlist, msg, msgdata, dmarc_wrap=False):
# Create a wrapper message around the original.
# There are various headers in msg that we don't want, so we basically
# make a copy of the msg, then delete almost everything and set/copy
# what we want.
omsg = copy.deepcopy(msg)
for key in msg.keys():
keep = False
for keeper in KEEPERS:
if re.match(keeper, key, re.I):
keep = True
break
if not keep:
del msg[key]
msg['MIME-Version'] = '1.0'
msg['Message-ID'] = make_msgid()
for k, v in munged_headers(mlist, omsg, msgdata):
msg[k] = v
# Are we including dmarc_wrapped_message_text? I.e., do we have text and
# are we wrapping because of dmarc_moderation_action?
if mlist.dmarc_wrapped_message_text and dmarc_wrap:
part1 = MIMEText(wrap(mlist.dmarc_wrapped_message_text),
'plain',
mlist.preferred_language.charset)
part1['Content-Disposition'] = 'inline'
part2 = MIMEMessage(omsg)
part2['Content-Disposition'] = 'inline'
msg['Content-Type'] = 'multipart/mixed'
msg.set_payload([part1, part2])
else:
msg['Content-Type'] = 'message/rfc822'
msg['Content-Disposition'] = 'inline'
msg.set_payload([omsg])
return
def process(mlist, msg, msgdata):
"""Process DMARC actions."""
if ((not msgdata.get('dmarc') or
mlist.dmarc_moderation_action == DMARCModerationAction.none) and
mlist.from_is_list == FromIsList.none):
return
if mlist.anonymous_list:
# DMARC mitigation is not required for anonymous lists.
return
if (mlist.dmarc_moderation_action != DMARCModerationAction.none and
msgdata.get('dmarc')):
if mlist.dmarc_moderation_action == DMARCModerationAction.munge_from:
munge_from(mlist, msg, msgdata)
elif (mlist.dmarc_moderation_action ==
DMARCModerationAction.wrap_message):
wrap_message(mlist, msg, msgdata, dmarc_wrap=True)
else:
assert False, (
'handlers/dmarc.py: dmarc_moderation_action = {0}'.format(
mlist.dmarc_moderation_action))
else:
if mlist.from_is_list == FromIsList.munge_from:
munge_from(mlist, msg, msgdata)
elif mlist.from_is_list == FromIsList.wrap_message:
wrap_message(mlist, msg, msgdata)
else:
assert False, (
'handlers/dmarc.py: from_is_list = {0}'.format(
mlist.from_is_list))
@public
@implementer(IHandler)
class DMARC:
"""Apply DMARC mitigations."""
name = 'dmarc'
description = _('Apply DMARC mitigations.')
def process(self, mlist, msg, msgdata):
"""See `IHandler`."""
process(mlist, msg, msgdata)
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