Initial import.

README.rst

+Milter replacing RCTP TO addresses with configured ones
+
+Intended to muzzle a mail-sending application while only touching its mail
+relay.
+
+"munnel" is a portmanteau, like milter: milter is a Mail fILTER, munnel is a
+Mail fUNNEL. And it is a funnel, because wherever the mail tries to fall, it
+will slide where configurations tells it to.

munnel/__init__.py

+# This file is part of python-munnel
+# Copyright (C) 2017  Nexedi
+# Author: Vincent Pelletier <vincent@nexedi.com>
+#
+# python-munnel 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.
+#
+# python-functionfs 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 python-munnel.  If not, see <http://www.gnu.org/licenses/>.
+import argparse
+import libmilter
+import signal
+import sys
+
+# XXX: this code is overcomplex because instance life scope is neither clearly
+# documented nor clearly readable from the code. So give this code more chances
+# to fail, to avoid letting mails go through unmodified.
+
+class Munnel(libmilter.ThreadMixin, libmilter.MilterProtocol):
+    replacement_recipient_list = None # Override in subclasses
+    existing_recipient_list = None # Will be filled/reset during instance life
+
+    def __init__(self, *args, **kw):
+        libmilter.ThreadMixin.__init__(self)
+        libmilter.MilterProtocol.__init__(self, *args, **kw)
+
+    @libmilter.noReply
+    def mailFrom(self, frAddr, cmdDict):
+        new_recipient_list = []
+        set_recipient_list = self.__dict__.setdefault(
+            'existing_recipient_list',
+            new_recipient_list,
+        )
+        assert new_recipient_list is set_recipient_list
+
+    @libmilter.noReply
+    def rcpt(self, recip, cmdDict):
+        self.existing_recipient_list.append(recip)
+
+    def eob(self, cmdDict):
+        delRcpt = self.delRcpt
+        for recipient in self.__dict__.pop('existing_recipient_list'):
+            delRcpt(recipient)
+        addRcpt = self.addRcpt
+        for recipient in self.replacement_recipient_list:
+            addRcpt(recipient)
+        return libmilter.CONTINUE
+
+    def close(self):
+        self.__dict__.pop('existing_recipient_list', None)
+
+def main():
+    parser = argparse.ArgumentParser(
+        description='Milter replacing RCTP TO addresses with configured ones',
+    )
+    parser.add_argument(
+        '--listen',
+        required=True,
+        help='Socket to listen to (format: "inet:$IP:$PORT" for network '
+        'socket, a bare path for unix socket)',
+    )
+    parser.add_argument(
+        'recipient',
+        nargs='+',
+        help='Addresses to actually send mails to',
+    )
+    args = parser.parse_args()
+    milter = libmilter.ThreadFactory(
+        sockstr=args.listen,
+        protocol=type(
+            'ThisMunnel',
+            (Munnel, ),
+            {
+                'replacement_recipient_list': args.recipient,
+            },
+        ),
+        opts=libmilter.SMFIF_DELRCPT | libmilter.SMFIF_ADDRCPT,
+        sockChmod=0660, # Why is libmilter trying to chmod at all !?
+    )
+    try:
+        milter.run()
+    except (SystemExit, KeyboardInterrupt):
+        pass
+    finally:
+        milter.close()
+
+if __name__ == '__main__':
+    main()

setup.py

+# This file is part of python-munnel
+# Copyright (C) 2017  Nexedi
+# Author: Vincent Pelletier <vincent@nexedi.com>
+#
+# python-munnel 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.
+#
+# python-functionfs 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 python-munnel.  If not, see <http://www.gnu.org/licenses/>.
+from setuptools import setup
+from codecs import open
+import os
+
+long_description = open(
+    os.path.join(os.path.dirname(__file__), 'README.rst'),
+    encoding='utf8',
+).read()
+
+setup(
+    name='munnel',
+    description=next(x for x in long_description.splitlines() if x.strip()),
+    long_description='.. contents::\n\n' + long_description,
+    keywords='smtp milter funnel',
+    version='0.1',
+    author='Nexedi',
+    author_email='vincent@nexedi.com',
+    url='http://lab.nexedi.com/vpelletier/python-munnel', # TODO: relocate to /nexedi
+    license='GPLv3',
+    platforms=['any'],
+    install_requires=['python-libmilter'],
+    packages=['munnel'],
+    classifiers=[
+        'License :: OSI Approved :: GNU Lesser General Public License v3 (LGPLv3)',
+        'Operating System :: OS Independent',
+    ],
+    entry_points={
+        'console_scripts': [
+            'funnel=funnel:main',
+        ],
+    }
+)