Modify Python Code - no idea at all

[Chris McKeever]

I am trying to modify the Mailman Python code to stop mapping
MIME-types and use the extension of the attachment instead. I am
pretty much clueless as to what I need to do here, but I think I have
narrowed it down to the Scrubber.py file..

If this seems like a quick step me through, I would be very
appreciative, could get you something on your Amazon wish-list (that
is me on my knees begging)..

From just my basic understanding, it looks like it does a mimemapping,
and then uses the 'best' extension for that type. We are sending .pdf
files, but they are being classified as application/octet-stream from
the mail program, and this then gets mapped to a .obj file extension
when it is being archived. This causes problems when going through
the archive.

I am attaching the code below, if anyone could give me some guidance..

Thanks!
Chris
cg********@prup ref.com

# Copyright (C) 2001-2003 by the Free Software Foundation, Inc.
#
# This program 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 2
# of the License, or (at your option) any later version.
#
# This program 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 this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.

"""Cleanse a message for archiving.
"""

from __future__ import nested_scopes

import os
import re
import sha
import time
import errno
import binascii
import tempfile
from cStringIO import StringIO
from types import IntType

from email.Utils import parsedate
from email.Parser import HeaderParser
from email.Generator import Generator

from Mailman import mm_cfg
from Mailman import Utils
from Mailman import LockFile
from Mailman import Message
from Mailman.Errors import DiscardMessage
from Mailman.i18n import _
from Mailman.Logging .Syslog import syslog

# Path characters for common platforms
pre = re.compile(r'[/\\:]')
# All other characters to strip out of Content-Disposition: filenames
# (essentially anything that isn't an alphanum, dot, slash, or
underscore.
sre = re.compile(r'[^-\w.]')
# Regexp to strip out leading dots
dre = re.compile(r'^\ .*')

BR = '<br>\n'
SPACE = ' '

try:
from mimetypes import guess_all_exten sions
except ImportError:
import mimetypes
def guess_all_exten sions(ctype, strict=1):
# BAW: sigh, guess_all_exten sions() is new in Python 2.3
all = []
def check(map):
for e, t in map.items():
if t == ctype:
all.append(e)
check(mimetypes .types_map)
# Python 2.1 doesn't have common_types. Sigh, sigh.
if not strict and hasattr(mimetyp es, 'common_types') :
check(mimetypes .common_types)
return all

def guess_extension (ctype, ext):
# mimetypes maps multiple extensions to the same type, e.g. .doc,
..dot,
# and .wiz are all mapped to application/msword. This sucks for
finding
# the best reverse mapping. If the extension is one of the giving
# mappings, we'll trust that, otherwise we'll just guess. :/
all = guess_all_exten sions(ctype, strict=0)
if ext in all:
return ext
return all and all[0]

# We're using a subclass of the standard Generator because we want to
suppress
# headers in the subparts of multiparts. We use a hack -- the ctor
argument
# skipheaders to accomplish this. It's set to true for the outer
Message
# object, but false for all internal objects. We recognize that
# sub-Generators will get created passing only mangle_from_ and
maxheaderlen
# to the ctors.
#
# This isn't perfect because we still get stuff like the multipart
boundaries,
# but see below for how we corrupt that to our nefarious goals.
class ScrubberGenerat or(Generator):
def __init__(self, outfp, mangle_from_=1, maxheaderlen=78 ,
skipheaders=1):
Generator.__ini t__(self, outfp, mangle_from_=0)
self.__skiphead ers = skipheaders

def _write_headers( self, msg):
if not self.__skiphead ers:
Generator._writ e_headers(self, msg)


def safe_strftime(f mt, floatsecs):
try:
return time.strftime(f mt, floatsecs)
except (TypeError, ValueError):
return None
def calculate_attac hments_dir(mlis t, msg, msgdata):
# Calculate the directory that attachments for this message will
go
# under. To avoid inode limitations, the scheme will be:
# archives/private/<listname>/attachments/YYYYMMDD/<msgid-hash>/<files>
# Start by calculating the date-based and msgid-hash components.
fmt = '%Y%m%d'
datestr = msg.get('Date')
if datestr:
now = parsedate(dates tr)
else:
now = time.gmtime(msg data.get('recei ved_time', time.time()))
datedir = safe_strftime(f mt, now)
if not datedir:
datestr = msgdata.get('X-List-Received-Date')
if datestr:
datedir = safe_strftime(f mt, datestr)
if not datedir:
# What next? Unixfrom, I guess.
parts = msg.get_unixfro m().split()
try:
month = {'Jan':1, 'Feb':2, 'Mar':3, 'Apr':4, 'May':5,
'Jun':6,
'Jul':7, 'Aug':8, 'Sep':9, 'Oct':10, 'Nov':11,
'Dec':12,
}.get(parts[3], 0)
day = int(parts[4])
year = int(parts[6])
except (IndexError, ValueError):
# Best we can do I think
month = day = year = 0
datedir = '%04d%02d%02d' % (year, month, day)
assert datedir
# As for the msgid hash, we'll base this part on the Message-ID:
so that
# all attachments for the same message end up in the same
directory (we'll
# uniquify the filenames in that directory as needed). We use the
first 2
# and last 2 bytes of the SHA1 hash of the message id as the basis
of the
# directory name. Clashes here don't really matter too much, and
that
# still gives us a 32-bit space to work with.
msgid = msg['message-id']
if msgid is None:
msgid = msg['Message-ID'] = Utils.unique_me ssage_id(mlist)
# We assume that the message id actually /is/ unique!
digest = sha.new(msgid). hexdigest()
return os.path.join('a ttachments', datedir, digest[:4] +
digest[-4:])

def process(mlist, msg, msgdata=None):
sanitize = mm_cfg.ARCHIVE_ HTML_SANITIZER
outer = 1
if msgdata is None:
msgdata = {}
dir = calculate_attac hments_dir(mlis t, msg, msgdata)
charset = None
lcset = Utils.GetCharSe t(mlist.preferr ed_language)
# Now walk over all subparts of this message and scrub out various
types
for part in msg.walk():
ctype = part.get_type(p art.get_default _type())
# If the part is text/plain, we leave it alone
if ctype == 'text/plain':
# We need to choose a charset for the scrubbed message, so
we'll
# arbitrarily pick the charset of the first text/plain
part in the
# message.
if charset is None:
charset = part.get_conten t_charset(lcset )
elif ctype == 'text/html' and isinstance(sani tize, IntType):
if sanitize == 0:
if outer:
raise DiscardMessage
del part['content-type']
part.set_payloa d(_('HTML attachment scrubbed and
removed'),
# Adding charset arg and removing
content-tpe
# sets content-type to text/plain
lcset)
elif sanitize == 2:
# By leaving it alone, Pipermail will automatically
escape it
pass
elif sanitize == 3:
# Pull it out as an attachment but leave it unescaped.
This
# is dangerous, but perhaps useful for heavily
moderated
# lists.
omask = os.umask(002)
try:
url = save_attachment (mlist, part, dir,
filter_html=0)
finally:
os.umask(omask)
del part['content-type']
part.set_payloa d(_("""\
An HTML attachment was scrubbed...
URL: %(url)s
"""), lcset)
else:
# HTML-escape it and store it as an attachment, but
make it
# look a /little/ bit prettier. :(
payload = Utils.websafe(p art.get_payload (decode=1))
# For whitespace in the margin, change spaces into
# non-breaking spaces, and tabs into 8 of those. Then
use a
# mono-space font. Still looks hideous to me, but
then I'd
# just as soon discard them.
def doreplace(s):
return s.replace(' ', '&nbsp;').repla ce('\t',
'&nbsp'*8)
lines = [doreplace(s) for s in payload.split(' \n')]
payload = '<tt>\n' + BR.join(lines) + '\n</tt>\n'
part.set_payloa d(payload)
# We're replacing the payload with the decoded payload
so this
# will just get in the way.
del part['content-transfer-encoding']
omask = os.umask(002)
try:
url = save_attachment (mlist, part, dir,
filter_html=0)
finally:
os.umask(omask)
del part['content-type']
part.set_payloa d(_("""\
An HTML attachment was scrubbed...
URL: %(url)s
"""), lcset)
elif ctype == 'message/rfc822':
# This part contains a submessage, so it too needs
scrubbing
submsg = part.get_payloa d(0)
omask = os.umask(002)
try:
url = save_attachment (mlist, part, dir)
finally:
os.umask(omask)
subject = submsg.get('sub ject', _('no subject'))
date = submsg.get('dat e', _('no date'))
who = submsg.get('fro m', _('unknown sender'))
size = len(str(submsg) )
del part['content-type']
part.set_payloa d(_("""\
An embedded message was scrubbed...
From: %(who)s
Subject: %(subject)s
Date: %(date)s
Size: %(size)s
Url: %(url)s
"""), lcset)
# If the message isn't a multipart, then we'll strip it out as
an
# attachment that would have to be separately downloaded.
Pipermail
# will transform the url into a hyperlink.
elif not part.is_multipa rt():
payload = part.get_payloa d(decode=1)
ctype = part.get_type()
size = len(payload)
omask = os.umask(002)
try:
url = save_attachment (mlist, part, dir)
finally:
os.umask(omask)
desc = part.get('conte nt-description', _('not available'))
filename = part.get_filena me(_('not available'))
del part['content-type']
del part['content-transfer-encoding']
part.set_payloa d(_("""\
A non-text attachment was scrubbed...
Name: %(filename)s
Type: %(ctype)s
Size: %(size)d bytes
Desc: %(desc)s
Url : %(url)s
"""), lcset)
outer = 0
# We still have to sanitize multipart messages to flat text
because
# Pipermail can't handle messages with list payloads. This is a
kludge;
# def (n) clever hack ;).
if msg.is_multipar t():
# By default we take the charset of the first text/plain part
in the
# message, but if there was none, we'll use the list's
preferred
# language's charset.
if charset is None or charset == 'us-ascii':
charset = lcset
# We now want to concatenate all the parts which have been
scrubbed to
# text/plain, into a single text/plain payload. We need to
make sure
# all the characters in the concatenated string are in the
same
# encoding, so we'll use the 'replace' key in the coercion
call.
# BAW: Martin's original patch suggested we might want to try
# generalizing to utf-8, and that's probably a good idea
(eventually).
text = []
for part in msg.get_payload ():
# All parts should be scrubbed to text/plain by now.
partctype = part.get_conten t_type()
if partctype <> 'text/plain':
text.append(_(' Skipped content of type
%(partctype)s') )
continue
try:
t = part.get_payloa d(decode=1)
except binascii.Error:
t = part.get_payloa d()
partcharset = part.get_conten t_charset()
if partcharset and partcharset <> charset:
try:
t = unicode(t, partcharset, 'replace')
except (UnicodeError, LookupError):
# Replace funny characters
t = unicode(t, 'ascii', 'replace').enco de('ascii')
try:
# Should use HTML-Escape, or try generalizing to
UTF-8
t = t.encode(charse t, 'replace')
except (UnicodeError, LookupError):
t = t.encode(lcset, 'replace')
# Separation is useful
if not t.endswith('\n' ):
t += '\n'
text.append(t)
# Now join the text and set the payload
sep = _('-------------- next part --------------\n')
del msg['content-type']
msg.set_payload (sep.join(text) , charset)
del msg['content-transfer-encoding']
msg.add_header( 'Content-Transfer-Encoding', '8bit')
return msg

def makedirs(dir):
# Create all the directories to store this attachment in
try:
os.makedirs(dir , 02775)
# Unfortunately, FreeBSD seems to be broken in that it doesn't
honor
# the mode arg of mkdir().
def twiddle(arg, dirname, names):
os.chmod(dirnam e, 02775)
os.path.walk(di r, twiddle, None)
except OSError, e:
if e.errno <> errno.EEXIST: raise

def save_attachment (mlist, msg, dir, filter_html=1):
fsdir = os.path.join(ml ist.archive_dir (), dir)
makedirs(fsdir)
# Figure out the attachment type and get the decoded data
decodedpayload = msg.get_payload (decode=1)
# BAW: mimetypes ought to handle non-standard, but commonly found
types,
# e.g. image/jpg (should be image/jpeg). For now we just store
such
# things as application/octet-streams since that seems the safest.
ctype = msg.get_content _type()
fnext = os.path.splitex t(msg.get_filen ame(''))[1]
ext = guess_extension (ctype, fnext)
if not ext:
# We don't know what it is, so assume it's just a shapeless
# application/octet-stream, unless the Content-Type: is
# message/rfc822, in which case we know we'll coerce the type
to
# text/plain below.
if ctype == 'message/rfc822':
ext = '.txt'
else:
ext = '.bin'
path = None
# We need a lock to calculate the next attachment number
lockfile = os.path.join(fs dir, 'attachments.lo ck')
lock = LockFile.LockFi le(lockfile)
lock.lock()
try:
# Now base the filename on what's in the attachment,
uniquifying it if
# necessary.
filename = msg.get_filenam e()
if not filename:
filebase = 'attachment'
else:
# Sanitize the filename given in the message headers
parts = pre.split(filen ame)
filename = parts[-1]
# Strip off leading dots
filename = dre.sub('', filename)
# Allow only alphanumerics, dash, underscore, and dot
filename = sre.sub('', filename)
# If the filename's extension doesn't match the type we
guessed,
# which one should we go with? For now, let's go with the
one we
# guessed so attachments can't lie about their type.
Also, if the
# filename /has/ no extension, then tack on the one we
guessed.
filebase, ignore = os.path.splitex t(filename)
# Now we're looking for a unique name for this file on the
file
# system. If msgdir/filebase.ext isn't unique, we'll add a
counter
# after filebase, e.g. msgdir/filebase-cnt.ext
counter = 0
extra = ''
while 1:
path = os.path.join(fs dir, filebase + extra + ext)
# Generally it is not a good idea to test for file
existance
# before just trying to create it, but the alternatives
aren't
# wonderful (i.e. os.open(..., O_CREAT | O_EXCL) isn't
# NFS-safe). Besides, we have an exclusive lock now, so
we're
# guaranteed that no other process will be racing with us.
if os.path.exists( path):
counter += 1
extra = '-%04d' % counter
else:
break
finally:
lock.unlock()
# `path' now contains the unique filename for the attachment.
There's
# just one more step we need to do. If the part is text/html and
# ARCHIVE_HTML_SA NITIZER is a string (which it must be or we
wouldn't be
# here), then send the attachment through the filter program for
# sanitization
if filter_html and ctype == 'text/html':
base, ext = os.path.splitex t(path)
tmppath = base + '-tmp' + ext
fp = open(tmppath, 'w')
try:
fp.write(decode dpayload)
fp.close()
cmd = mm_cfg.ARCHIVE_ HTML_SANITIZER % {'filename' :
tmppath}
progfp = os.popen(cmd, 'r')
decodedpayload = progfp.read()
status = progfp.close()
if status:
syslog('error',
'HTML sanitizer exited with non-zero status:
%s',
status)
finally:
os.unlink(tmppa th)
# BAW: Since we've now sanitized the document, it should be
plain
# text. Blarg, we really want the sanitizer to tell us what
the type
# if the return data is. :(
ext = '.txt'
path = base + '.txt'
# Is it a message/rfc822 attachment?
elif ctype == 'message/rfc822':
submsg = msg.get_payload ()
# BAW: I'm sure we can eventually do better than this. :(
decodedpayload = Utils.websafe(s tr(submsg))
fp = open(path, 'w')
fp.write(decode dpayload)
fp.close()
# Now calculate the url
baseurl = mlist.GetBaseAr chiveURL()
# Private archives will likely have a trailing slash. Normalize.
if baseurl[-1] <> '/':
baseurl += '/'
url = baseurl + '%s/%s%s%s' % (dir, filebase, extra, ext)
return url