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# Copyright (C) 2009-2015 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/>.
"""Email helpers."""
__all__ = [
'add_message_hash',
'split_email',
]
from base64 import b32encode
from hashlib import sha1
def split_email(address):
"""Split an email address into a user name and domain.
:param address: An email address.
:type address: string
:return: The user name and domain split on dots.
:rtype: 2-tuple where the first item is the local part and the second item
is a sequence of domain parts.
"""
local_part, at, domain = address.partition('@')
if len(at) == 0:
# There was no at-sign in the email address.
return local_part, None
return local_part, domain.split('.')
def add_message_hash(msg):
"""Add a Message-ID-Hash header derived from Message-ID.
This function works by side-effect; the original message is mutated.
Any existing Message-ID-Headers are deleted if a Message-ID header
is found. If no Message-ID header is found, the original message is
not modified.
:param msg: An email message
:type msg: `email.message.Message` or derived
:return: The Message-ID-Hash contents.
:rtype: str
"""
message_id = msg.get('message-id')
if message_id is None:
return
if isinstance(message_id, bytes):
message_id = message_id.decode('ascii')
# The angle brackets are not part of the Message-ID. See RFC 2822
# and http://wiki.list.org/display/DEV/Stable+URLs
if message_id.startswith('<') and message_id.endswith('>'):
message_id = message_id[1:-1]
else:
message_id = message_id.strip()
# Because .digest() returns bytes, b32encode() will return bytes, however
# we need a string for the header value. We know the b32encoded byte
# string must be ascii-only.
digest = sha1(message_id.encode('utf-8')).digest()
hash32 = b32encode(digest).decode('ascii')
del msg['message-id-hash']
msg['Message-ID-Hash'] = hash32
# For backward compatibility with previous versions of the spec.
del msg['x-message-id-hash']
msg['X-Message-ID-Hash'] = hash32
return hash32
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