http2irc/http2irc.py

import aiohttp
import aiohttp.web
import asyncio
import base64
import collections
import concurrent.futures
import importlib.util
import inspect
import logging
import os.path
import signal
import ssl
import string
import sys
import toml


SSL_CONTEXTS = {'yes': True, 'no': False, 'insecure': ssl.SSLContext()}


class InvalidConfig(Exception):
	'''Error in configuration file'''


def is_valid_pem(path, withCert):
	'''Very basic check whether something looks like a valid PEM certificate'''
	try:
		with open(path, 'rb') as fp:
			contents = fp.read()

		# All of these raise exceptions if something's wrong...
		if withCert:
			assert contents.startswith(b'-----BEGIN CERTIFICATE-----\n')
			endCertPos = contents.index(b'-----END CERTIFICATE-----\n')
			base64.b64decode(contents[28:endCertPos].replace(b'\n', b''), validate = True)
			assert contents[endCertPos + 26:].startswith(b'-----BEGIN PRIVATE KEY-----\n')
		else:
			assert contents.startswith(b'-----BEGIN PRIVATE KEY-----\n')
			endCertPos = -26 # Please shoot me.
		endKeyPos = contents.index(b'-----END PRIVATE KEY-----\n')
		base64.b64decode(contents[endCertPos + 26 + 28: endKeyPos].replace(b'\n', b''), validate = True)
		assert contents[endKeyPos + 26:] == b''
		return True
	except: # Yes, really
		return False


class Config(dict):
	def __init__(self, filename):
		super().__init__()
		self._filename = filename

		with open(self._filename, 'r') as fp:
			obj = toml.load(fp)

		logging.info(repr(obj))

		# Sanity checks
		if any(x not in ('logging', 'irc', 'web', 'maps') for x in obj.keys()):
			raise InvalidConfig('Unknown sections found in base object')
		if any(not isinstance(x, collections.abc.Mapping) for x in obj.values()):
			raise InvalidConfig('Invalid section type(s), expected objects/dicts')
		if 'logging' in obj:
			if any(x not in ('level', 'format') for x in obj['logging']):
				raise InvalidConfig('Unknown key found in log section')
			if 'level' in obj['logging'] and obj['logging']['level'] not in ('DEBUG', 'INFO', 'WARNING', 'ERROR'):
				raise InvalidConfig('Invalid log level')
			if 'format' in obj['logging']:
				if not isinstance(obj['logging']['format'], str):
					raise InvalidConfig('Invalid log format')
				try:
					#TODO: Replace with logging.Formatter's validate option (3.8+); this test does not cover everything that could be wrong (e.g. invalid format spec or conversion)
					# This counts the number of replacement fields. Formatter.parse yields tuples whose second value is the field name; if it's None, there is no field (e.g. literal text).
					assert sum(1 for x in string.Formatter().parse(obj['logging']['format']) if x[1] is not None) > 0
				except (ValueError, AssertionError) as e:
					raise InvalidConfig('Invalid log format: parsing failed') from e
		if 'irc' in obj:
			if any(x not in ('host', 'port', 'ssl', 'nick', 'real', 'certfile', 'certkeyfile') for x in obj['irc']):
				raise InvalidConfig('Unknown key found in irc section')
			if 'host' in obj['irc'] and not isinstance(obj['irc']['host'], str): #TODO: Check whether it's a valid hostname
				raise InvalidConfig('Invalid IRC host')
			if 'port' in obj['irc'] and (not isinstance(obj['irc']['port'], int) or not 1 <= obj['irc']['port'] <= 65535):
				raise InvalidConfig('Invalid IRC port')
			if 'ssl' in obj['irc'] and obj['irc']['ssl'] not in ('yes', 'no', 'insecure'):
				raise InvalidConfig(f'Invalid IRC SSL setting: {obj["irc"]["ssl"]!r}')
			if 'nick' in obj['irc'] and not isinstance(obj['irc']['nick'], str): #TODO: Check whether it's a valid nickname
				raise InvalidConfig('Invalid IRC nick')
			if 'real' in obj['irc'] and not isinstance(obj['irc']['real'], str):
				raise InvalidConfig('Invalid IRC realname')
			if ('certfile' in obj['irc']) != ('certkeyfile' in obj['irc']):
				raise InvalidConfig('Invalid IRC cert config: needs both certfile and certkeyfile')
			if 'certfile' in obj['irc']:
				if not isinstance(obj['irc']['certfile'], str):
					raise InvalidConfig('Invalid certificate file: not a string')
				if not os.path.isfile(obj['irc']['certfile']):
					raise InvalidConfig('Invalid certificate file: not a regular file')
				if not is_valid_pem(obj['irc']['certfile'], True):
					raise InvalidConfig('Invalid certificate file: not a valid PEM cert')
			if 'certkeyfile' in obj['irc']:
				if not isinstance(obj['irc']['certkeyfile'], str):
					raise InvalidConfig('Invalid certificate key file: not a string')
				if not os.path.isfile(obj['irc']['certkeyfile']):
					raise InvalidConfig('Invalid certificate key file: not a regular file')
				if not is_valid_pem(obj['irc']['certkeyfile'], False):
					raise InvalidConfig('Invalid certificate key file: not a valid PEM key')
		if 'web' in obj:
			if any(x not in ('host', 'port') for x in obj['web']):
				raise InvalidConfig('Unknown key found in web section')
			if 'host' in obj['web'] and not isinstance(obj['web']['host'], str): #TODO: Check whether it's a valid hostname (must resolve I guess?)
				raise InvalidConfig('Invalid web hostname')
			if 'port' in obj['web'] and (not isinstance(obj['web']['port'], int) or not 1 <= obj['web']['port'] <= 65535):
				raise InvalidConfig('Invalid web port')
		if 'maps' in obj:
			for key, map_ in obj['maps'].items():
				if not isinstance(key, str) or not key:
					raise InvalidConfig(f'Invalid map key {key!r}')
				if not isinstance(map_, collections.abc.Mapping):
					raise InvalidConfig(f'Invalid map for {key!r}')
				if any(x not in ('webpath', 'ircchannel', 'auth', 'module') for x in map_):
					raise InvalidConfig(f'Unknown key(s) found in map {key!r}')
				#TODO: Check values
				if 'module' in map_ and not os.path.isfile(map_['module']):
					raise InvalidConfig(f'Module {map_["module"]!r} in map {key!r} is not a file')

		# Default values
		finalObj = {'logging': {'level': 'INFO', 'format': '{asctime} {levelname} {message}'}, 'irc': {'host': 'irc.hackint.org', 'port': 6697, 'ssl': 'yes', 'nick': 'h2ibot', 'real': 'I am an http2irc bot.', 'certfile': None, 'certkeyfile': None}, 'web': {'host': '127.0.0.1', 'port': 8080}, 'maps': {}}

		# Fill in default values for the maps
		for key, map_ in obj['maps'].items():
			if 'webpath' not in map_:
				map_['webpath'] = f'/{key}'
			if 'ircchannel' not in map_:
				map_['ircchannel'] = f'#{key}'
			if 'auth' not in map_:
				map_['auth'] = False
			if 'module' not in map_:
				map_['module'] = None

		# Load modules
		modulePaths = {map_['module'] for map_ in obj['maps'].values() if 'module' in map_ and map_['module'] is not None}
		modules = {} # path: str -> module: module
		for i, path in enumerate(modulePaths):
			try:
				# Build a name that is virtually guaranteed to be unique across a process.
				# Although importlib does not seem to perform any caching as of CPython 3.8, this is not guaranteed by spec.
				spec = importlib.util.spec_from_file_location(f'http2irc-module-{id(self)}-{i}', path)
				module = importlib.util.module_from_spec(spec)
				spec.loader.exec_module(module)
			except Exception as e: # This is ugly, but exec_module can raise virtually any exception
				raise InvalidConfig(f'Loading module {path!r} failed: {e!s}')
			if not hasattr(module, 'process'):
				raise InvalidConfig(f'Module {path!r} does not have a process function')
			if not inspect.iscoroutinefunction(module.process):
				raise InvalidConfig(f'Module {path!r} process attribute is not a coroutine function')
			if len(inspect.signature(module.process).parameters) != 1:
				raise InvalidConfig(f'Module {path!r} process function does not take exactly 1 parameter')
			modules[path] = module

		# Replace module value in maps
		for map_ in obj['maps'].values():
			if 'module' in map_ and map_['module'] is not None:
				map_['module'] = modules[map_['module']]

		# Merge in what was read from the config file and set keys on self
		for key in ('logging', 'irc', 'web', 'maps'):
			if key in obj:
				finalObj[key].update(obj[key])
			self[key] = finalObj[key]

	def __repr__(self):
		return f'<Config(logging={self["logging"]!r}, irc={self["irc"]!r}, web={self["web"]!r}, maps={self["maps"]!r})>'

	def reread(self):
		return Config(self._filename)


class MessageQueue:
	# An object holding onto the messages received from nodeping
	# This is effectively a reimplementation of parts of asyncio.Queue with some specific additional code.
	# Unfortunately, asyncio.Queue's extensibility (_init, _put, and _get methods) is undocumented, so I don't want to rely on that.
	# Differences to asyncio.Queue include:
	#  - No maxsize
	#  - No put coroutine (not necessary since the queue can never be full)
	#  - Only one concurrent getter
	#  - putleft_nowait to put to the front of the queue (so that the IRC client can put a message back when delivery fails)

	def __init__(self):
		self._getter = None  # None | asyncio.Future
		self._queue = collections.deque()

	async def get(self):
		if self._getter is not None:
			raise RuntimeError('Cannot get concurrently')
		if len(self._queue) == 0:
			self._getter = asyncio.get_running_loop().create_future()
			logging.debug('Awaiting getter')
			try:
				await self._getter
			except asyncio.CancelledError:
				logging.debug('Cancelled getter')
				self._getter = None
				raise
			logging.debug('Awaited getter')
			self._getter = None
		# For testing the cancellation/putting back onto the queue
		#logging.debug('Delaying message queue get')
		#await asyncio.sleep(3)
		#logging.debug('Done delaying')
		return self.get_nowait()

	def get_nowait(self):
		if len(self._queue) == 0:
			raise asyncio.QueueEmpty
		return self._queue.popleft()

	def put_nowait(self, item):
		self._queue.append(item)
		if self._getter is not None and not self._getter.cancelled():
			self._getter.set_result(None)

	def putleft_nowait(self, *item):
		self._queue.extendleft(reversed(item))
		if self._getter is not None and not self._getter.cancelled():
			self._getter.set_result(None)

	def qsize(self):
		return len(self._queue)


class IRCClientProtocol(asyncio.Protocol):
	def __init__(self, messageQueue, connectionClosedEvent, loop, config, channels):
		logging.debug(f'Protocol init {id(self)}: {messageQueue} {id(messageQueue)}, {connectionClosedEvent}, {loop}')
		self.messageQueue = messageQueue
		self.connectionClosedEvent = connectionClosedEvent
		self.loop = loop
		self.config = config
		self.buffer = b''
		self.connected = False
		self.channels = channels # Currently joined/supposed-to-be-joined channels; set(str)
		self.unconfirmedMessages = []
		self.pongReceivedEvent = asyncio.Event()

	def connection_made(self, transport):
		logging.info('Connected')
		self.transport = transport
		self.connected = True
		nickb = self.config['irc']['nick'].encode('utf-8')
		self.send(b'NICK ' + nickb)
		self.send(b'USER ' + nickb + b' ' + nickb + b' ' + nickb + b' :' + self.config['irc']['real'].encode('utf-8'))

	def update_channels(self, channels: set):
		channelsToPart = self.channels - channels
		channelsToJoin = channels - self.channels
		self.channels = channels

		if self.connected:
			if channelsToPart:
				#TODO: Split if too long
				self.send(b'PART ' + ','.join(channelsToPart).encode('utf-8'))
			if channelsToJoin:
				self.send(b'JOIN ' + ','.join(channelsToJoin).encode('utf-8'))

	def send(self, data):
		logging.info(f'Send: {data!r}')
		self.transport.write(data + b'\r\n')

	async def _get_message(self):
		logging.debug(f'Message queue {id(self.messageQueue)} length: {self.messageQueue.qsize()}')
		messageFuture = asyncio.create_task(self.messageQueue.get())
		done, pending = await asyncio.wait((messageFuture, self.connectionClosedEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
		if self.connectionClosedEvent.is_set():
			if messageFuture in pending:
				logging.debug('Cancelling messageFuture')
				messageFuture.cancel()
				try:
					await messageFuture
				except asyncio.CancelledError:
					logging.debug('Cancelled messageFuture')
					pass
			else:
				# messageFuture is already done but we're stopping, so put the result back onto the queue
				self.messageQueue.putleft_nowait(messageFuture.result())
			return None, None
		assert messageFuture in done, 'Invalid state: messageFuture not in done futures'
		return messageFuture.result()

	async def send_messages(self):
		while self.connected:
			logging.debug(f'{id(self)}: trying to get a message')
			channel, message = await self._get_message()
			logging.debug(f'{id(self)}: got message: {message!r}')
			if message is None:
				break
			#TODO Split if the message is too long.
			self.unconfirmedMessages.append((channel, message))
			self.send(b'PRIVMSG ' + channel.encode('utf-8') + b' :' + message.encode('utf-8'))
			await asyncio.sleep(1) # Rate limit

	async def confirm_messages(self):
		while self.connected:
			await asyncio.wait((asyncio.sleep(60), self.connectionClosedEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)  # Confirm once per minute
			if not self.connected: # Disconnected while sleeping, can't confirm unconfirmed messages, requeue them directly
				self.messageQueue.putleft_nowait(*self.unconfirmedMessages)
				self.unconfirmedMessages = []
				break
			if not self.unconfirmedMessages:
				logging.debug(f'{id(self)}: no messages to confirm')
				continue
			logging.debug(f'{id(self)}: trying to confirm message delivery')
			self.pongReceivedEvent.clear()
			self.send(b'PING :42')
			await asyncio.wait((asyncio.sleep(5), self.pongReceivedEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
			logging.debug(f'{id(self)}: message delivery success: {self.pongReceivedEvent.is_set()}')
			if not self.pongReceivedEvent.is_set():
				# No PONG received in five seconds, assume connection's dead
				self.messageQueue.putleft_nowait(*self.unconfirmedMessages)
				self.transport.close()
			self.unconfirmedMessages = []

	def data_received(self, data):
		logging.debug(f'Data received: {data!r}')
		# Split received data on CRLF. If there's any data left in the buffer, prepend it to the first message and process that.
		# Then, process all messages except the last one (since data might not end on a CRLF) and keep the remainder in the buffer.
		# If data does end with CRLF, all messages will have been processed and the buffer will be empty again.
		messages = data.split(b'\r\n')
		if self.buffer:
			self.message_received(self.buffer + messages[0])
			messages = messages[1:]
		for message in messages[:-1]:
			self.message_received(message)
		self.buffer = messages[-1]

	def message_received(self, message):
		logging.info(f'Message received: {message!r}')
		if message.startswith(b':'):
			# Prefixed message, extract command + parameters (the prefix cannot contain a space)
			message = message.split(b' ', 1)[1]
		if message.startswith(b'PING '):
			self.send(b'PONG ' + message[5:])
		elif message.startswith(b'PONG '):
			self.pongReceivedEvent.set()
		elif message.startswith(b'001 '):
			# Connection registered
			self.send(b'JOIN ' + ','.join(self.channels).encode('utf-8')) #TODO: Split if too long
			asyncio.create_task(self.send_messages())
			asyncio.create_task(self.confirm_messages())

	def connection_lost(self, exc):
		logging.info('The server closed the connection')
		self.connected = False
		self.connectionClosedEvent.set()


class IRCClient:
	def __init__(self, messageQueue, config):
		self.messageQueue = messageQueue
		self.config = config
		self.channels = {map_['ircchannel'] for map_ in config['maps'].values()}

		self._transport = None
		self._protocol = None

	def update_config(self, config):
		needReconnect = self.config['irc'] != config['irc']
		self.config = config
		if self._transport: # if currently connected:
			if needReconnect:
				self._transport.close()
			else:
				self.channels = {map_['ircchannel'] for map_ in config['maps'].values()}
				self._protocol.update_channels(self.channels)

	def _get_ssl_context(self):
		ctx = SSL_CONTEXTS[self.config['irc']['ssl']]
		if self.config['irc']['certfile'] and self.config['irc']['certkeyfile']:
			if ctx is True:
				ctx = ssl.create_default_context()
			if isinstance(ctx, ssl.SSLContext):
				ctx.load_cert_chain(self.config['irc']['certfile'], keyfile = self.config['irc']['certkeyfile'])
		return ctx

	async def run(self, loop, sigintEvent):
		connectionClosedEvent = asyncio.Event()
		while True:
			connectionClosedEvent.clear()
			try:
				self._transport, self._protocol = await loop.create_connection(lambda: IRCClientProtocol(self.messageQueue, connectionClosedEvent, loop, self.config, self.channels), self.config['irc']['host'], self.config['irc']['port'], ssl = self._get_ssl_context())
				try:
					await asyncio.wait((connectionClosedEvent.wait(), sigintEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
				finally:
					self._transport.close() #TODO BaseTransport.close is asynchronous and then triggers the protocol's connection_lost callback; need to wait for connectionClosedEvent again perhaps to correctly handle ^C?
			except (ConnectionRefusedError, asyncio.TimeoutError) as e:
				logging.error(str(e))
			await asyncio.wait((asyncio.sleep(5), sigintEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
			if sigintEvent.is_set():
				break


class WebServer:
	def __init__(self, messageQueue, config):
		self.messageQueue = messageQueue
		self.config = config

		self._paths = {} # '/path' => ('#channel', auth, module)  where auth is either False (no authentication) or the HTTP header value for basic auth

		self._app = aiohttp.web.Application()
		self._app.add_routes([aiohttp.web.post('/{path:.+}', self.post)])

		self.update_config(config)
		self._configChanged = asyncio.Event()

	def update_config(self, config):
		self._paths = {map_['webpath']: (map_['ircchannel'], f'Basic {base64.b64encode(map_["auth"].encode("utf-8")).decode("utf-8")}' if map_['auth'] else False, map_['module']) for map_ in config['maps'].values()}
		needRebind = self.config['web'] != config['web']
		self.config = config
		if needRebind:
			self._configChanged.set()

	async def run(self, stopEvent):
		while True:
			runner = aiohttp.web.AppRunner(self._app)
			await runner.setup()
			site = aiohttp.web.TCPSite(runner, self.config['web']['host'], self.config['web']['port'])
			await site.start()
			await asyncio.wait((stopEvent.wait(), self._configChanged.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
			await runner.cleanup()
			if stopEvent.is_set():
				break
			self._configChanged.clear()

	async def post(self, request):
		logging.info(f'Received request for {request.path!r}')
		try:
			channel, auth, module = self._paths[request.path]
		except KeyError:
			logging.info(f'Bad request: no path {request.path!r}')
			raise aiohttp.web.HTTPNotFound()
		if auth:
			authHeader = request.headers.get('Authorization')
			if not authHeader or authHeader != auth:
				logging.info(f'Bad request: authentication failed: {authHeader!r} != {auth}')
				raise aiohttp.web.HTTPForbidden()
		if module is not None:
			try:
				message = await module.process(request)
			except aiohttp.web.HTTPException as e:
				raise e
			except Exception as e:
				logging.error(f'Bad request: exception in module process function: {e!s}')
				raise aiohttp.web.HTTPBadRequest()
			if '\r' in message or '\n' in message:
				logging.error(f'Bad request: module process function returned message with linebreaks: {message!r}')
				raise aiohttp.web.HTTPBadRequest()
		else:
			message = await self._default_process(request)
		logging.debug(f'Putting message {message!r} for {channel} into message queue')
		self.messageQueue.put_nowait((channel, message))
		raise aiohttp.web.HTTPOk()

	async def _default_process(self, request):
		try:
			message = await request.text()
		except Exception as e:
			logging.info(f'Bad request: exception while reading request data: {e!s}')
			raise aiohttp.web.HTTPBadRequest() # Yes, it's always the client's fault. :-)
		logging.debug(f'Request payload: {message!r}')
		# Strip optional [CR] LF at the end of the payload
		if message.endswith('\r\n'):
			message = message[:-2]
		elif message.endswith('\n'):
			message = message[:-1]
		if '\r' in message or '\n' in message:
			logging.info('Bad request: linebreaks in message')
			raise aiohttp.web.HTTPBadRequest()
		return message


def configure_logging(config):
	#TODO: Replace with logging.basicConfig(..., force = True) (Py 3.8+)
	root = logging.getLogger()
	root.setLevel(getattr(logging, config['logging']['level']))
	root.handlers = [] #FIXME: Undocumented attribute of logging.Logger
	formatter = logging.Formatter(config['logging']['format'], style = '{')
	stderrHandler = logging.StreamHandler()
	stderrHandler.setFormatter(formatter)
	root.addHandler(stderrHandler)


async def main():
	if len(sys.argv) != 2:
		print('Usage: http2irc.py CONFIGFILE', file = sys.stderr)
		sys.exit(1)
	configFile = sys.argv[1]
	config = Config(configFile)
	configure_logging(config)

	loop = asyncio.get_running_loop()

	messageQueue = MessageQueue()

	irc = IRCClient(messageQueue, config)
	webserver = WebServer(messageQueue, config)

	sigintEvent = asyncio.Event()
	def sigint_callback():
		logging.info('Got SIGINT')
		nonlocal sigintEvent
		sigintEvent.set()
	loop.add_signal_handler(signal.SIGINT, sigint_callback)

	def sigusr1_callback():
		logging.info('Got SIGUSR1, reloading config')
		nonlocal config, irc, webserver
		try:
			newConfig = config.reread()
		except InvalidConfig as e:
			logging.error(f'Config reload failed: {e!s}')
			return
		config = newConfig
		configure_logging(config)
		irc.update_config(config)
		webserver.update_config(config)
	loop.add_signal_handler(signal.SIGUSR1, sigusr1_callback)

	await asyncio.gather(irc.run(loop, sigintEvent), webserver.run(sigintEvent))


if __name__ == '__main__':
	asyncio.run(main())