src/mailman/handlers/cook_headers.py

   1 # Copyright (C) 1998-2019 by the Free Software Foundation, Inc.
   2 #
   3 # This file is part of GNU Mailman.
   4 #
   5 # GNU Mailman is free software: you can redistribute it and/or modify it under
   6 # the terms of the GNU General Public License as published by the Free
   7 # Software Foundation, either version 3 of the License, or (at your option)
   8 # any later version.
   9 #
  10 # GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
  11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12 # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  13 # more details.
  14 #
  15 # You should have received a copy of the GNU General Public License along with
  16 # GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
  17
  18 """Cook a message's headers."""
  19
  20 import logging
  21
  22 from email.header import Header
  23 from email.utils import formataddr, getaddresses, parseaddr
  24 from mailman.core.i18n import _
  25 from mailman.interfaces.handler import IHandler
  26 from mailman.interfaces.mailinglist import Personalization, ReplyToMunging
  27 from mailman.version import VERSION
  28 from public import public
  29 from zope.interface import implementer
  30
  31
  32 log = logging.getLogger('mailman.error')
  33
  34 COMMASPACE = ', '
  35 MAXLINELEN = 78
  36
  37
  38 @public
  39 def uheader(mlist, s, header_name=None, continuation_ws='\t', maxlinelen=None):
  40     """Get the charset to encode the string in.
  41
  42     Then search if there is any non-ascii character is in the string.  If
  43     there is and the charset is us-ascii then we use iso-8859-1 instead.  If
  44     the string is ascii only we use 'us-ascii' if another charset is
  45     specified.
  46
  47     If the header contains a newline, truncate it (see GL#273).
  48     """
  49     charset = mlist.preferred_language.charset
  50     if '\n' in s:
  51         s = '{} [...]'.format(s.split('\n')[0])
  52         log.warning('Header {} contains a newline, truncating it.'.format(
  53             header_name, s))
  54     return Header(s, charset, maxlinelen, header_name, continuation_ws)
  55
  56
  57 def process(mlist, msg, msgdata):
  58     """Process the headers of the message."""
  59     # Set the "X-Ack: no" header if noack flag is set.
  60     if msgdata.get('noack'):
  61         del msg['x-ack']
  62         msg['X-Ack'] = 'no'
  63     # Because we're going to modify various important headers in the email
  64     # message, we want to save some of the information in the msgdata
  65     # dictionary for later.  Specifically, the sender header will get waxed,
  66     # but we need it for the Acknowledge module later.
  67     msgdata['original_sender'] = msg.sender
  68     # VirginRunner sets _fasttrack for internally crafted messages.
  69     fasttrack = msgdata.get('_fasttrack')
  70     # Add Precedence: and other useful headers.  None of these are standard
  71     # and finding information on some of them are fairly difficult.  Some are
  72     # just common practice, and we'll add more here as they become necessary.
  73     # Good places to look are:
  74     #
  75     # http://www.dsv.su.se/~jpalme/ietf/jp-ietf-home.html
  76     # http://www.faqs.org/rfcs/rfc2076.html
  77     #
  78     # None of these headers are added if they already exist.  BAW: some
  79     # consider the advertising of this a security breach.  I.e. if there are
  80     # known exploits in a particular version of Mailman and we know a site is
  81     # using such an old version, they may be vulnerable.  It's too easy to
  82     # edit the code to add a configuration variable to handle this.
  83     if 'x-mailman-version' not in msg:
  84         msg['X-Mailman-Version'] = VERSION
  85     # We set "Precedence: list" because this is the recommendation from the
  86     # sendmail docs, the most authoritative source of this header's semantics.
  87     if 'precedence' not in msg:
  88         msg['Precedence'] = 'list'
  89     # Reply-To: munging.  Do not do this if the message is "fast tracked",
  90     # meaning it is internally crafted and delivered to a specific user.  BAW:
  91     # Yuck, I really hate this feature but I've caved under the sheer pressure
  92     # of the (very vocal) folks want it.  OTOH, RFC 2822 allows Reply-To: to
  93     # be a list of addresses, so instead of replacing the original, simply
  94     # augment it.  RFC 2822 allows max one Reply-To: header so collapse them
  95     # if we're adding a value, otherwise don't touch it.  (Should we collapse
  96     # in all cases?)
  97     if not fasttrack:
  98         # A convenience function, requires nested scopes.  pair is (name, addr)
  99         new = []
 100         d = {}
 101         def add(pair):                              # noqa: E306
 102             lcaddr = pair[1].lower()
 103             if lcaddr in d:
 104                 return
 105             d[lcaddr] = pair
 106             new.append(pair)
 107         # List admin wants an explicit Reply-To: added
 108         if (mlist.reply_goes_to_list is ReplyToMunging.explicit_header
 109             or mlist.reply_goes_to_list
 110                 is ReplyToMunging.explicit_header_only):
 111             add(parseaddr(mlist.reply_to_address))
 112         # If we're not first stripping existing Reply-To: then we need to add
 113         # the original Reply-To:'s to the list we're building up.  In both
 114         # cases we'll zap the existing field because RFC 2822 says max one is
 115         # allowed.
 116         if not mlist.first_strip_reply_to:
 117             orig = msg.get_all('reply-to', [])
 118             for pair in getaddresses(orig):
 119                 add(pair)
 120         # Set Reply-To: header to point back to this list.  Add this last
 121         # because some folks think that some MUAs make it easier to delete
 122         # addresses from the right than from the left.
 123         if mlist.reply_goes_to_list is ReplyToMunging.point_to_list:
 124             i18ndesc = uheader(mlist, mlist.description, 'Reply-To')
 125             add((str(i18ndesc), mlist.posting_address))
 126         del msg['reply-to']
 127         # Don't put Reply-To: back if there's nothing to add!
 128         if new:
 129             # Preserve order
 130             msg['Reply-To'] = COMMASPACE.join(
 131                 [formataddr(pair) for pair in new])
 132         # The To field normally contains the list posting address.  However
 133         # when messages are fully personalized, that header will get
 134         # overwritten with the address of the recipient.  We need to get the
 135         # posting address in one of the recipient headers or they won't be
 136         # able to reply back to the list.  It's possible the posting address
 137         # was munged into the Reply-To header, but if not, we'll add it to a
 138         # Cc header.  BAW: should we force it into a Reply-To header in the
 139         # above code?
 140         # Also skip Cc if this is an anonymous list as list posting address
 141         # is already in From and Reply-To in this case.
 142         if (mlist.personalize is Personalization.full
 143                 and mlist.reply_goes_to_list is not               # noqa: W503
 144                     ReplyToMunging.point_to_list
 145                 and not mlist.anonymous_list):                    # noqa: W503
 146             # Watch out for existing Cc headers, merge, and remove dups.  Note
 147             # that RFC 2822 says only zero or one Cc header is allowed.
 148             new = []
 149             d = {}
 150             for pair in getaddresses(msg.get_all('cc', [])):
 151                 add(pair)
 152             if (mlist.reply_goes_to_list is not
 153                     ReplyToMunging.explicit_header_only):
 154                 i18ndesc = uheader(mlist, mlist.description, 'Cc')
 155                 add((str(i18ndesc), mlist.posting_address))
 156             del msg['Cc']
 157             # Don't add an empty Cc:
 158             if new:
 159                 msg['Cc'] = COMMASPACE.join([formataddr(pair) for pair in new])
 160
 161
 162 @public
 163 @implementer(IHandler)
 164 class CookHeaders:
 165     """Modify message headers."""
 166
 167     name = 'cook-headers'
 168     description = _('Modify message headers.')
 169
 170     def process(self, mlist, msg, msgdata):
 171         """See `IHandler`."""
 172         process(mlist, msg, msgdata)