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# Dovecot authentication plugin for Radicale.
# Copyright (C) 2017-2019 Arvedui <arvedui@posteo.de>
#
# 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 3 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, see <http://www.gnu.org/licenses/>.
from base64 import b64encode
import os
import socket
HANDSHAKE = "VERSION\t1\t1\nCPID\t{}\n"
SUPPORTED_MAJOR_VERSION = 1
AUTH_COMMAND = "AUTH\t{id}\tPLAIN\tservice={service}\tresp="
class DovecotAuthException(Exception):
"""DovecotAuth base Exception"""
class UnsupportedVersion(DovecotAuthException):
"""Thrown if the protocol version of the auth server ist not supported"""
class HandshakeFailed(DovecotAuthException):
"""Thrown if the Handshake with the auth server fails"""
class UnexpectedData(DovecotAuthException):
"""
Thrown if there is still data the recieve buffer that was not expected
"""
class DovecotAuth:
"""
DovecotAuth provides authentication against a Dovecot authentication
service using the PLAIN mechanism.
Only version 1.1 as described in the `Dovecot Wiki`_
.. _Dovecot Wiki: https://wiki2.dovecot.org/Design/AuthProtocol
:param service: Name of the service authentication services are provided for
:param socket_path: Path to the unix domain socket of the auth server
:param host: hostname of the auth server
:param port: port of the auth server
"""
def __init__(self, service, *,
socket_path=None, host=None, port=None, ssl=False):
self.socket_path = socket_path
self.buffer = bytes()
self.authid = 1
self.service = service
if socket_path:
self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
self.socket.connect(self.socket_path)
elif host and port:
self.socket = socket.create_connection((host, port))
else:
raise RuntimeError('auth_socket path or auth_host and auth_port must be set')
self._handshake()
def buffer_is_empty(self):
return len(self.buffer) == 0
def _readline(self):
"""Read one line from the socket using a receive buffer"""
nextlineend = self.buffer.find(b'\n')
while nextlineend == -1:
self.buffer += self.socket.recv(4096)
nextlineend = self.buffer.find(b'\n')
nextline = self.buffer[:nextlineend]
self.buffer = self.buffer[nextlineend+1:]
return nextline.split(b'\t')
def _send(self, msg):
"""
Send data via the socket
:param msg: message to send
"""
send_bytes = 0
while send_bytes != len(msg):
send_bytes += self.socket.send(msg[send_bytes:])
def _handshake(self):
"""
Perform handshake according to dovecot auth protocol
"""
done = False
plain = False
self._send(HANDSHAKE.format(os.getpid()).encode('utf8'))
while not done:
command, *arguments = self._readline()
if command == b"VERSION":
if int(arguments[0]) != SUPPORTED_MAJOR_VERSION:
raise UnsupportedVersion
elif command == b'MECH':
if arguments[0] == b'PLAIN':
plain = True
elif command == b'DONE':
done = True
if not plain:
raise HandshakeFailed(
'auth mechanism PLAIN is not supported by dovecot')
def authenticate(self, username, password):
"""Authenticate given credentials"""
done = False
credentials = "\0{username}\0{password}".format(
username=username, password=password)
credentials = b64encode(credentials.encode('utf8'))
command = AUTH_COMMAND.format(id=self.authid, service=self.service)
command = command.encode('ascii')
command += credentials
command += b'\n'
self.authid += 1
self._send(command)
command, *arguments = self._readline()
if not self.buffer_is_empty:
raise UnexpectedData(
"Server has sent data that was not expected: {}".format(
self.buffer))
if command == b'OK':
return True
return False
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