diff options
Diffstat (limited to 'src/mailman/pipeline/mime_delete.py')
| -rw-r--r-- | src/mailman/pipeline/mime_delete.py | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/src/mailman/pipeline/mime_delete.py b/src/mailman/pipeline/mime_delete.py new file mode 100644 index 000000000..3c4e4154f --- /dev/null +++ b/src/mailman/pipeline/mime_delete.py @@ -0,0 +1,285 @@ +# Copyright (C) 2002-2009 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/>. + +"""MIME-stripping filter for Mailman. + +This module scans a message for MIME content, removing those sections whose +MIME types match one of a list of matches. multipart/alternative sections are +replaced by the first non-empty component, and multipart/mixed sections +wrapping only single sections after other processing are replaced by their +contents. +""" + +from __future__ import absolute_import, unicode_literals + +__metaclass__ = type +__all__ = [ + 'MIMEDelete', + ] + + +import os +import errno +import logging +import tempfile + +from email.Iterators import typed_subpart_iterator +from os.path import splitext +from zope.interface import implements + +from mailman.Utils import oneline +from mailman.config import config +from mailman.core import errors +from mailman.i18n import _ +from mailman.interfaces.handler import IHandler +from mailman.queue import Switchboard +from mailman.version import VERSION + +log = logging.getLogger('mailman.error') + + + +def process(mlist, msg, msgdata): + # Short-circuits + if not mlist.filter_content: + return + if msgdata.get('isdigest'): + return + # We also don't care about our own digests or plaintext + ctype = msg.get_content_type() + mtype = msg.get_content_maintype() + # Check to see if the outer type matches one of the filter types + filtertypes = mlist.filter_mime_types + passtypes = mlist.pass_mime_types + if ctype in filtertypes or mtype in filtertypes: + dispose(mlist, msg, msgdata, + _("The message's content type was explicitly disallowed")) + # Check to see if there is a pass types and the outer type doesn't match + # one of these types + if passtypes and not (ctype in passtypes or mtype in passtypes): + dispose(mlist, msg, msgdata, + _("The message's content type was not explicitly allowed")) + # Filter by file extensions + filterexts = mlist.filter_filename_extensions + passexts = mlist.pass_filename_extensions + fext = get_file_ext(msg) + if fext: + if fext in filterexts: + dispose(mlist, msg, msgdata, + _("The message's file extension was explicitly disallowed")) + if passexts and not (fext in passexts): + dispose(mlist, msg, msgdata, + _("The message's file extension was not explicitly allowed")) + numparts = len([subpart for subpart in msg.walk()]) + # If the message is a multipart, filter out matching subparts + if msg.is_multipart(): + # Recursively filter out any subparts that match the filter list + prelen = len(msg.get_payload()) + filter_parts(msg, filtertypes, passtypes, filterexts, passexts) + # If the outer message is now an empty multipart (and it wasn't + # before!) then, again it gets discarded. + postlen = len(msg.get_payload()) + if postlen == 0 and prelen > 0: + dispose(mlist, msg, msgdata, + _("After content filtering, the message was empty")) + # Now replace all multipart/alternatives with just the first non-empty + # alternative. BAW: We have to special case when the outer part is a + # multipart/alternative because we need to retain most of the outer part's + # headers. For now we'll move the subpart's payload into the outer part, + # and then copy over its Content-Type: and Content-Transfer-Encoding: + # headers (any others?). + if mlist.collapse_alternatives: + collapse_multipart_alternatives(msg) + if ctype == 'multipart/alternative': + firstalt = msg.get_payload(0) + reset_payload(msg, firstalt) + # If we removed some parts, make note of this + changedp = 0 + if numparts <> len([subpart for subpart in msg.walk()]): + changedp = 1 + # Now perhaps convert all text/html to text/plain + if mlist.convert_html_to_plaintext and config.HTML_TO_PLAIN_TEXT_COMMAND: + changedp += to_plaintext(msg) + # If we're left with only two parts, an empty body and one attachment, + # recast the message to one of just that part + if msg.is_multipart() and len(msg.get_payload()) == 2: + if msg.get_payload(0).get_payload() == '': + useful = msg.get_payload(1) + reset_payload(msg, useful) + changedp = 1 + if changedp: + msg['X-Content-Filtered-By'] = 'Mailman/MimeDel {0}'.format(VERSION) + + + +def reset_payload(msg, subpart): + # Reset payload of msg to contents of subpart, and fix up content headers + payload = subpart.get_payload() + msg.set_payload(payload) + del msg['content-type'] + del msg['content-transfer-encoding'] + del msg['content-disposition'] + del msg['content-description'] + msg['Content-Type'] = subpart.get('content-type', 'text/plain') + cte = subpart.get('content-transfer-encoding') + if cte: + msg['Content-Transfer-Encoding'] = cte + cdisp = subpart.get('content-disposition') + if cdisp: + msg['Content-Disposition'] = cdisp + cdesc = subpart.get('content-description') + if cdesc: + msg['Content-Description'] = cdesc + + + +def filter_parts(msg, filtertypes, passtypes, filterexts, passexts): + # Look at all the message's subparts, and recursively filter + if not msg.is_multipart(): + return True + payload = msg.get_payload() + prelen = len(payload) + newpayload = [] + for subpart in payload: + keep = filter_parts(subpart, filtertypes, passtypes, + filterexts, passexts) + if not keep: + continue + ctype = subpart.get_content_type() + mtype = subpart.get_content_maintype() + if ctype in filtertypes or mtype in filtertypes: + # Throw this subpart away + continue + if passtypes and not (ctype in passtypes or mtype in passtypes): + # Throw this subpart away + continue + # check file extension + fext = get_file_ext(subpart) + if fext: + if fext in filterexts: + continue + if passexts and not (fext in passexts): + continue + newpayload.append(subpart) + # Check to see if we discarded all the subparts + postlen = len(newpayload) + msg.set_payload(newpayload) + if postlen == 0 and prelen > 0: + # We threw away everything + return False + return True + + + +def collapse_multipart_alternatives(msg): + if not msg.is_multipart(): + return + newpayload = [] + for subpart in msg.get_payload(): + if subpart.get_content_type() == 'multipart/alternative': + try: + firstalt = subpart.get_payload(0) + newpayload.append(firstalt) + except IndexError: + pass + else: + newpayload.append(subpart) + msg.set_payload(newpayload) + + + +def to_plaintext(msg): + changedp = False + for subpart in typed_subpart_iterator(msg, 'text', 'html'): + filename = tempfile.mktemp('.html') + fp = open(filename, 'w') + try: + fp.write(subpart.get_payload(decode=True)) + fp.close() + cmd = os.popen(config.HTML_TO_PLAIN_TEXT_COMMAND % + {'filename': filename}) + plaintext = cmd.read() + rtn = cmd.close() + if rtn: + log.error('HTML->text/plain error: %s', rtn) + finally: + try: + os.unlink(filename) + except OSError, e: + if e.errno <> errno.ENOENT: + raise + # Now replace the payload of the subpart and twiddle the Content-Type: + del subpart['content-transfer-encoding'] + subpart.set_payload(plaintext) + subpart.set_type('text/plain') + changedp = True + return changedp + + + +def dispose(mlist, msg, msgdata, why): + # filter_action == 0 just discards, see below + if mlist.filter_action == 1: + # Bounce the message to the original author + raise errors.RejectMessage, why + if mlist.filter_action == 2: + # Forward it on to the list owner + listname = mlist.internal_name() + mlist.ForwardMessage( + msg, + text=_("""\ +The attached message matched the %(listname)s mailing list's content filtering +rules and was prevented from being forwarded on to the list membership. You +are receiving the only remaining copy of the discarded message. + +"""), + subject=_('Content filtered message notification')) + if mlist.filter_action == 3 and \ + config.OWNERS_CAN_PRESERVE_FILTERED_MESSAGES: + badq = Switchboard(config.BADQUEUE_DIR) + badq.enqueue(msg, msgdata) + # Most cases also discard the message + raise errors.DiscardMessage + + +def get_file_ext(m): + """ + Get filename extension. Caution: some virus don't put filename + in 'Content-Disposition' header. +""" + fext = '' + filename = m.get_filename('') or m.get_param('name', '') + if filename: + fext = splitext(oneline(filename,'utf-8'))[1] + if len(fext) > 1: + fext = fext[1:] + else: + fext = '' + return fext + + + +class MIMEDelete: + """Filter the MIME content of messages.""" + + implements(IHandler) + + name = 'mime-delete' + description = _('Filter the MIME content of messages.') + + def process(self, mlist, msg, msgdata): + process(mlist, msg, msgdata) |