from twisted.trial import unittest
from twisted.test import proto_helpers
from noise.connection import NoiseConnection, Keypair
from twisted.internet.protocol import Factory
from twisted.internet import endpoints, reactor, defer, task
# XXX - shouldn't need to access the underlying primitives, but that's what
# noiseprotocol module requires.
from cryptography.hazmat.primitives.asymmetric import x448
from cryptography.hazmat.primitives import serialization

import mock
import os.path
import shutil
import tempfile
import twisted.internet.protocol

__author__ = 'John-Mark Gurney'
__copyright__ = 'Copyright 2019 John-Mark Gurney.  All rights reserved.'
__license__ = '2-clause BSD license'

# Copyright 2019 John-Mark Gurney.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.

# Notes:
# Using XK, so that the connecting party's identity is hidden and that the
# server's party's key is known.
#
# Noise packets are 16 bytes + length of data
#
# Proposed method to hide message lengths:
# Immediately after handshake completes, each side generates and sends
# an n byte key that will be used for encrypting (algo tbd) their own
# byte counts.  The length field will be encrypted via
# E(pktnum, key) XOR 2 byte length.
#
# Note that authenticating the message length is NOT needed.  This is
# because the noise message blocks themselves are authenticated.  The
# worse that could happen is that a larger read (64k) is done, and then
# the connection aborts because of decryption failure.
#

def genkeypair():
	'''Generates a keypair, and returns a tuple of (public, private).
	They are encoded as raw bytes, and sutible for use w/ Noise.'''

	key = x448.X448PrivateKey.generate()

	enc = serialization.Encoding.Raw
	pubformat = serialization.PublicFormat.Raw
	privformat = serialization.PrivateFormat.Raw
	encalgo = serialization.NoEncryption()

	pub = key.public_key().public_bytes(encoding=enc, format=pubformat)
	priv = key.private_bytes(encoding=enc, format=privformat, encryption_algorithm=encalgo)

	return pub, priv

class TwistedNoiseProtocol(twisted.internet.protocol.Protocol):
	'''This class acts as a Noise Protocol responder.  The factory that
	creates this Protocol is required to have the properties server_key
	and endpoint.

	The server_key propery is the key for the server that the clients are
	required to have (due to Noise XK protocol used) to authenticate the
	server.

	The endpoint property contains the endpoint as a string that will be
	used w/ clientFromString, see https://twistedmatrix.com/documents/current/api/twisted.internet.endpoints.html#clientFromString
	and https://twistedmatrix.com/documents/current/core/howto/endpoints.html#clients
	for information on how to use this property.'''

	def connectionMade(self):
		# Initialize Noise
		noise = NoiseConnection.from_name(b'Noise_XK_448_ChaChaPoly_SHA256')
		self.noise = noise
		noise.set_as_responder()
		noise.set_keypair_from_private_bytes(Keypair.STATIC, self.factory.server_key)

		# Start Handshake
		noise.start_handshake()

	def encData(self, data):
		self.transport.write(self.noise.encrypt(data))

	def dataReceived(self, data):
		if not self.noise.handshake_finished:
			self.noise.read_message(data)
			if not self.noise.handshake_finished:
				self.transport.write(self.noise.write_message())
			if self.noise.handshake_finished:
				self.handshakeFinished()
		else:
			r = self.noise.decrypt(data)

			self.endpoint.transport.write(r)

	def handshakeFinished(self):
		raise NotImplementedError

	def plaintextConnected(self, endpoint):
		self.endpoint = endpoint
		self.transport.resumeProducing()

class TwistedNoiseServerProtocol(TwistedNoiseProtocol):
	def handshakeFinished(self):
		self.transport.pauseProducing()

		# start the connection to the endpoint
		ep = endpoints.clientFromString(reactor, self.factory.endpoint)
		epdef = ep.connect(ClientProxyFactory(self))
		epdef.addCallback(self.plaintextConnected)

class ClientProxyProtocol(twisted.internet.protocol.Protocol):
	def dataReceived(self, data):
		self.factory.noiseproto.encData(data)

class ClientProxyFactory(Factory):
	protocol = ClientProxyProtocol

	def __init__(self, noiseproto):
		self.noiseproto = noiseproto

class TwistedNoiseServerFactory(Factory):
	protocol = TwistedNoiseServerProtocol

	def __init__(self, server_key, endpoint):
		self.server_key = server_key
		self.endpoint = endpoint

class TNServerTest(unittest.TestCase):
	@defer.inlineCallbacks
	def setUp(self):
		d = os.path.realpath(tempfile.mkdtemp())
		self.basetempdir = d
		self.tempdir = os.path.join(d, 'subdir')
		os.mkdir(self.tempdir)

		self.server_key_pair = genkeypair()
		self.protos = []
		self.connectionmade = defer.Deferred()

		class AccProtFactory(Factory):
			protocol = proto_helpers.AccumulatingProtocol

			def __init__(self, tc):
				self.__tc = tc
				Factory.__init__(self)

			protocolConnectionMade = self.connectionmade

			def buildProtocol(self, addr):
				r = Factory.buildProtocol(self, addr)
				self.__tc.protos.append(r)
				return r

		sockpath = os.path.join(self.tempdir, 'clientsock')
		ep = endpoints.UNIXServerEndpoint(reactor, sockpath)
		lpobj = yield ep.listen(AccProtFactory(self))

		self.testserv = ep
		self.listenportobj = lpobj
		self.endpoint = 'unix:path=%s' % sockpath

		factory = TwistedNoiseServerFactory(server_key=self.server_key_pair[1], endpoint=self.endpoint)
		self.proto = factory.buildProtocol(None)
		self.tr = proto_helpers.StringTransport()
		self.proto.makeConnection(self.tr)

		self.client_key_pair = genkeypair()

	def tearDown(self):
		self.listenportobj.stopListening()

		shutil.rmtree(self.basetempdir)
		self.tempdir = None

	@defer.inlineCallbacks
	def test_testserver(self):
		#
		# How this test is plumbed:
		#
		#  proto (NoiseConnection) -> self.tr (StringTransport) ->
		#    self.proto (TwistedNoiseServerProtocol) ->
		#    self.proto.endpoint (ClientProxyProtocol) -> unix sock ->
		#    self.protos[0] (AccumulatingProtocol)
		#
		# Create client
		proto = NoiseConnection.from_name(b'Noise_XK_448_ChaChaPoly_SHA256')
		proto.set_as_initiator()

		# Setup required keys
		proto.set_keypair_from_private_bytes(Keypair.STATIC, self.client_key_pair[1])
		proto.set_keypair_from_public_bytes(Keypair.REMOTE_STATIC, self.server_key_pair[0])

		proto.set_keypair_from_private_bytes(Keypair.STATIC, self.client_key_pair[1])
		proto.start_handshake()

		# Send first message
		message = proto.write_message()
		self.proto.dataReceived(message)

		# Get response
		resp = self.tr.value()
		self.tr.clear()

		# And process it
		proto.read_message(resp)

		# Send second message
		message = proto.write_message()
		self.proto.dataReceived(message)

		# assert handshake finished
		self.assertTrue(proto.handshake_finished)

		# Make sure incoming data is paused till we establish client
		# connection, otherwise no place to write the data
		self.assertEqual(self.tr.producerState, 'paused')

		# Wait for the connection to be made
		d = yield self.connectionmade

		d = yield task.deferLater(reactor, .1, bool, 1)

		# How to make this ready?
		self.assertEqual(self.tr.producerState, 'producing')

		# Encrypt the message
		ptmsg = b'this is a test message'
		encmsg = proto.encrypt(ptmsg)

		# Feed it into the protocol
		self.proto.dataReceived(encmsg)

		# wait to pass it through
		d = yield task.deferLater(reactor, .1, bool, 1)

		# fetch remote end out
		clientend = self.protos[0]
		self.assertEqual(clientend.data, ptmsg)

		# send a message the other direction
		rptmsg = b'this is a different test message going the other way'
		clientend.transport.write(rptmsg)

		# wait to pass it through
		d = yield task.deferLater(reactor, .1, bool, 1)

		# receive it and decrypt it
		resp = self.tr.value()
		self.assertEqual(proto.decrypt(resp), rptmsg)

		# clean up connection
		clientend.transport.loseConnection()