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#!/usr/bin/env python3
# -*- Mode: Python; coding: utf-8; indent-tabs-mode: nil; tab-width: 4 -*-
# Copyright (C) 2019 Bryce W. Harrington
#
# Released under GNU GPLv2 or later, read the file 'LICENSE.GPLv2+' for
# more information.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# Author: Bryce Harrington <bryce@canonical.com>
import os
import sys
import socket
from tempfile import mkstemp
DEBUGGING = True
DEFAULT_HOST = ''
DEFAULT_PORT = 11110
NEWLINE = b"\r\n"
MESSAGE_CONTENT = b'''
From: test@example.com\r
Subject: Test message\r
\r
This is a body for testing\r
\r
'''
def dbg(msg):
"""Prints information to stdout if debugging is enabled"""
if DEBUGGING:
sys.stdout.write("{}\n".format(msg))
def command_user(data, msg):
return b'+OK user accepted'
def command_pass(data, msg):
return b'+OK pass accepted'
def command_stat(data, msg):
return b'+OK 1 %i' %(msg.size)
def command_list(data, msg):
if data == b'LIST':
return b'+OK 1 messages (%i octets)'%(msg.size) \
+ NEWLINE \
+ b'1 %i'%(msg.size) \
+ NEWLINE \
+ b'.'
else:
cmd, num = data.split()
return b'+OK 1 (%i octects)'%(msg.size)
def command_last(data, msg):
return b'+OK 0'
def command_top(data, msg):
cmd, num, lines = data.split()
assert num == b'1', "unknown message number: {num}".format(num)
bottom = NEWLINE.join(msg.bottom[:int(lines)])
text = msg.top + NEWLINE + NEWLINE + bottom
dbg(text)
return b'+OK top of message follows%s' % (NEWLINE + text + NEWLINE + b'.')
def command_retr(data, msg):
return b'+OK %i octets'%(msg.size) \
+ NEWLINE \
+ data \
+ NEWLINE \
+ b'.'
def command_dele(data, msg):
return b'+OK 1 %i'%(msg.size)
def command_noop(data, msg):
return b'+OK 1 %i'%(msg.size)
def command_quit(data, msg):
return b'+OK mock pop3 server signing off'
COMMANDS = {
b'USER' : command_user,
b'PASS' : command_pass,
b'STAT' : command_stat,
b'LIST' : command_list,
b'LAST' : command_last,
b'TOP' : command_top,
b'RETR' : command_retr,
b'DELE' : command_dele,
b'NOOP' : command_noop,
b'QUIT' : command_quit,
}
class Mailbox:
"""Encapsulates a mailbox containing a single email message"""
def __init__(self, message_filename):
with open(message_filename, "rb") as msg:
data = msg.read()
self.data = data
self.size = len(data)
self.top, rest = data.split(NEWLINE + NEWLINE, 1)
self.bottom = rest.split(NEWLINE)
class Mailserver:
def __init__(self, conn, mbox):
self._conn = conn
self._mbox = mbox
self._chunk_size = 4096
def close(self):
dbg(" - Server exiting")
self._conn.close()
def send(self, data):
dbg(" - Server sending")
self._conn.sendall(data + NEWLINE)
def receive(self):
dbg(" - Server receiving")
data = []
while True:
chunk = self._conn.recv(self._chunk_size)
if NEWLINE in chunk:
data.append(chunk[:chunk.index(NEWLINE)])
break
data.append(chunk)
return b"".join(data)
def process(self):
data = self.receive()
dbg(" - Received: '{}'".format(data))
command = data.split(None, 1)[0]
if command in COMMANDS.keys():
response = COMMANDS[command](data, self._mbox)
dbg(" - Response: {}".format(response))
try:
self.send(response)
if command == b'QUIT':
return False
except BrokenPipeError:
dbg(" - Client terminated connection")
return False
else:
self.send(b"-ERR unrecognized command")
return True
def serve(messages_filename, host=DEFAULT_HOST, port=DEFAULT_PORT):
dbg("Serving for {} on {}".format(host, port))
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((host, port))
mailbox = Mailbox(messages_filename)
try:
dbg("* mock-pop3-server ready on {}:{}".format(host, port))
while True:
sock.listen(1)
conn, address = sock.accept()
dbg("* Connection from {}".format(address))
server = Mailserver(conn, mailbox)
server.send(b"+OK mock-pop3-server pop3 server ready")
try:
dbg("* Processing commands for connection...")
while server.process():
dbg("* Finished command")
pass
finally:
dbg("* Closing remote connection")
server.close()
except KeyboardInterrupt:
dbg("* mock-pop3-server interrupted")
return 1
except SystemExit:
dbg("* mock-pop3-server exiting")
return 1
finally:
sock.shutdown(socket.SHUT_RDWR)
sock.close()
return 0
if __name__ == "__main__":
fd, message_filename = mkstemp(prefix='message-', suffix='.txt')
dbg("Creating message file '{}'".format(message_filename))
with open(message_filename, 'wb') as f:
f.write(MESSAGE_CONTENT.lstrip())
try:
exit(serve(message_filename, host=DEFAULT_HOST, port=DEFAULT_PORT))
except KeyError:
sys.stderr.write("Exiting\n")
sys.exit(1)
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