host_agent.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from __future__ import unicode_literals
__author__ = "Nash Kaminski"
__license__ = "Dual License: GPLv2 and Commercial License"

import ipaddress
import json
import logging
import netifaces
import os
import redis
import subprocess
import requests
from tenacity import (
    Retrying,
    RetryError,
    stop_after_attempt,
    wait_fixed,
)


REDIS_ARGS = dict(host="127.0.0.1", port=6379, db=0)
# Name of redis channel to listen to
CHANNEL_NAME = b'hostcmd'
SUPPORTED_INTERFACES = (
    'wlan',
    'eth',
    'wlp',
    'enp',
)


def get_ip_addresses():
    return [
        ip['addr']
        for interface in netifaces.interfaces()
        if interface.startswith(SUPPORTED_INTERFACES)
        for ip in (
            netifaces.ifaddresses(interface).get(netifaces.AF_INET, []) +
            netifaces.ifaddresses(interface).get(netifaces.AF_INET6, [])
        )
        if not ipaddress.ip_address(ip['addr']).is_link_local
    ]


def set_ip_addresses():
    rdb = redis.Redis(**REDIS_ARGS)

    rdb.set('ip_addresses_ready', 'false')

    try:
        for attempt in Retrying(
            stop=stop_after_attempt(10),
            wait=wait_fixed(1),
        ):
            with attempt:
                response = requests.get('https://1.1.1.1')
                response.raise_for_status()
    except RetryError:
        logging.warning(
            'Unable to connect to the Internet. '
            'Proceeding with the current IP addresses available.'
        )

    rdb.set('ip_addresses_ready', 'true')

    ip_addresses = get_ip_addresses()
    rdb.set('ip_addresses', json.dumps(ip_addresses))


# Explicit command whitelist for security reasons, keys as bytes objects
CMD_TO_ARGV = {
    b'reboot': ['/usr/bin/sudo', '-n', '/usr/bin/systemctl', 'reboot'],
    b'shutdown': ['/usr/bin/sudo', '-n', '/usr/bin/systemctl', 'poweroff'],
    b'set_ip_addresses': set_ip_addresses
}


def execute_host_command(cmd_name):
    cmd = CMD_TO_ARGV.get(cmd_name, None)
    if cmd is None:
        logging.warning(
            "Unable to perform host command %s: no such command!", cmd_name)
    elif os.getenv('TESTING'):
        logging.warning(
            "Would have executed %s but not doing so as TESTING is defined",
            cmd,
        )
    elif cmd_name in [b'reboot', b'shutdown']:
        logging.info("Executing host command %s", cmd_name)
        phandle = subprocess.run(cmd)
        logging.info(
            "Host command %s (%s) returned %s",
            cmd_name,
            cmd,
            phandle.returncode,
        )
    else:
        logging.info('Calling function %s', cmd)
        cmd()


def process_message(message):
    if (
        message.get('type', '') == 'message'
        and message.get('channel', b'') == CHANNEL_NAME
    ):
        execute_host_command(message.get('data', b''))
    else:
        logging.info("Received unsolicited message: %s", message)


def subscriber_loop():
    # Connect to redis on localhost and wait for messages
    logging.info("Connecting to redis...")
    rdb = redis.Redis(**REDIS_ARGS)
    pubsub = rdb.pubsub(ignore_subscribe_messages=True)
    pubsub.subscribe(CHANNEL_NAME)
    rdb.set('host_agent_ready', 'true')
    logging.info(
        "Subscribed to channel %s, ready to process messages", CHANNEL_NAME)
    for message in pubsub.listen():
        process_message(message)


if __name__ == '__main__':
    # Init logging
    logging.basicConfig()
    logging.getLogger().setLevel(logging.INFO)

    # Loop forever processing messages
    subscriber_loop()