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Viewing / Editing File: captcha_dos_detect.py

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import ipaddress
import logging
import time
from collections import defaultdict
from typing import Union

from humanize import naturaldelta

from defence360agent.contracts import plugins
from defence360agent.contracts.messages import MessageType
from defence360agent.model.simplification import run_in_executor
from im360.contracts.config import CaptchaDOS as Config
from im360.model.firewall import IPList

logger = logging.getLogger(__name__)


class CaptchaDosDetect(plugins.MessageSink, plugins.MessageSource):
    def __init__(self):
        self._events = defaultdict(list)
        self._init_config()

    async def create_sink(self, loop):
        self._loop = loop

    async def create_source(self, loop, sink):
        self._loop = loop
        self._sink = sink

    def _init_config(self):
        self._enabled = Config.ENABLED
        self._time_frame = Config.TIME_FRAME
        self._timeout = Config.TIMEOUT
        self._max_count = Config.MAX_COUNT

    @plugins.expect(MessageType.ConfigUpdate)
    async def update_config(self, _):
        self._init_config()

    @plugins.expect(
        MessageType.CaptchaEvent, event=MessageType.CaptchaEvent.REQUESTED
    )
    async def process_captcha_event(self, message):
        if message.get('is_ajax') or not self._enabled:
            return

        ip = message['attackers_ip']
        ip_events = self._events[ip]
        ip_events.append(message['timestamp'])

        t0 = message['timestamp'] - self._time_frame
        timeframe_hits = [ts for ts in ip_events if t0 <= ts]
        retries = len(timeframe_hits)

        if retries > self._max_count:
            ttl = self._timeout
            expiration = \
                await self.get_expiration(ip, ttl)

            captcha_dos_alert = MessageType.CaptchaDosAlert(
                attackers_ip=ip,
                expiration=expiration,
                ttl=ttl,
                retries=retries,
                timestamp=time.time(),
                message=(
                    "Blacklisted for {} after {} captcha requests"
                ).format(
                    naturaldelta(expiration - int(time.time())),
                    retries
                )
            )

            await self._sink.process_message(captcha_dos_alert)
            del self._events[ip]

        else:
            # make sure to keep only interesting items
            self._events[ip] = timeframe_hits

        self._cleanup_expired(t0)

    def _cleanup_expired(self, ts):
        """
        Remove IP addresses that have latest event older then ts
        """
        expired_ips = [ip for ip, timestamps in self._events.items()
                       if timestamps[-1] < ts]
        for ip in expired_ips:
            del self._events[ip]

    async def get_expiration(
            self,
            ip: Union[ipaddress.IPv4Network, ipaddress.IPv6Network],
            ttl: int):
        """
        Generate new graylist expiration based on calculated dos expiration

        :param ip_network ip:
        :param int ttl: default time to block for
        :return: int expiration: new expiration for ip items in gray list
        """
        dos_expiration = int(time.time()) + ttl
        subnet = await run_in_executor(
            self._loop,
            lambda: IPList.find_closest_ip_nets(
                ip, listname=[IPList.GRAY], limit=1)
        )
        if not subnet:
            return dos_expiration
        else:
            return max(dos_expiration, subnet[0].expiration)
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