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Initial commit. At least it works.

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Gonçalo Valério 2 years ago
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27ce46fa76
  1. 21
      LICENSE
  2. 8
      README.md
  3. 78
      agent.py
  4. 137
      worker.js

21
LICENSE

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MIT License
Copyright (c) 2020 Gonçalo Valério
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.

8
README.md

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# Worker DDNS
Workers as a proxy in a DDNS setup that uses the cloudflare API.
Both scripts, `worker.js` and `agent.py` don't require any extra dependencies,
so it is very simple to deploy/setup. Just copy the files and you're done.
More detailed documentation will be added soon.

78
agent.py

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#!/usr/bin/env python3
"""
Simple agent script that collects the public IP address of the machine it is
running on and then updates a Cloudflare Worker.
All requests are signed using a pre-shared key to ensure the integrity of the
message and authenticate the source.
"""
import os
import sys
import hmac
import json
import logging
import random
from datetime import datetime
from urllib import request, parse, error
logger = logging.getLogger(__name__)
IP_SOURCES = [
"https://api.ipify.org/",
"https://icanhazip.com/",
"https://ifconfig.me/",
]
# For some reason the default urllib User-Agent is blocked
FAKE_USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
def setup_logger() -> None:
form = logging.Formatter("%(asctime)s | %(levelname)s | %(message)s")
handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.INFO)
handler.setFormatter(form)
logger.setLevel(logging.INFO)
logger.addHandler(handler)
def get_ip_address() -> str:
url = random.choice(IP_SOURCES)
res = request.urlopen(url)
return res.read().decode("utf8").strip()
def sign_message(message: bytes, key: bytes) -> str:
message_hmac = hmac.new(key, message, digestmod="sha256")
return message_hmac.hexdigest()
def update_dns_record(url: str, key: str):
ip_addr = get_ip_address()
timestamp = int(datetime.now().timestamp())
payload = json.dumps({"addr": ip_addr, "timestamp": timestamp}).encode("utf8")
signature = sign_message(payload, key.encode("utf8"))
req = request.Request(f"https://{url}")
req.add_header("Content-Type", "application/json; charset=utf-8")
req.add_header("User-Agent", FAKE_USER_AGENT)
req.add_header("Authorization", signature)
req.add_header("Content-Length", len(payload))
request.urlopen(req, payload)
logger.info("DNS Record updated successfully")
if __name__ == "__main__":
setup_logger()
key = os.environ.get("SHARED_KEY")
url = os.environ.get("WORKER_URL")
if key and url:
try:
update_dns_record(url, key)
except (error.URLError, error.HTTPError) as err:
logger.exception("Failed to update DNS record")
else:
logger.error("Cannot find configs. Aborting DNS update")

137
worker.js

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/**
* This handled a request to update a given DNS record.
* The request should have the following format:
*
* { "addr": "<ipv4_addr>", "timestamp": <unix_timestamp> }
*
* The request must be made by the machine that the record will be pointed to
* and contain the HMAC (of the request body) in the "Authorization" header
*/
addEventListener("fetch", (event) => {
event.respondWith(handleRequest(event.request));
});
/**
* Handles the request and validates if changes should be made or not
* @param {Request} request
*/
async function handleRequest(request) {
if (request.method === "POST") {
let valid_request = await is_valid(request);
if (valid_request) {
const addr = request.headers.get("cf-connecting-ip");
await updateRecord(addr);
return new Response("Não há gente como a gente", { status: 200 });
}
}
return new Response("Por cima", { status: 401 });
}
/**
* Checks if it is a valid and authentic request
* @param {Request} request
*/
async function is_valid(request) {
const window = 300; // 5 minutes in seconds
const rawBody = await request.text();
let bodyContent = {};
try {
bodyContent = JSON.parse(rawBody);
} catch (e) {
return false;
}
const sourceAddr = request.headers.get("cf-connecting-ip");
const signature = request.headers.get("authorization");
if (!signature || !bodyContent.addr || sourceAddr != bodyContent.addr) {
return false;
}
const valid_hmac = await verifyHMAC(signature, rawBody);
if (!valid_hmac) {
return false;
}
const now = Math.floor(Date.now() / 1000);
if (now - bodyContent.timestamp > window) {
return false;
}
return true;
}
/**
* Verifies the provided HMAC matches the message
* @param {String} signature
* @param {String} message
*/
async function verifyHMAC(signature, message) {
let encoder = new TextEncoder();
let key = await crypto.subtle.importKey(
"raw",
encoder.encode(SHARED_KEY),
{ name: "HMAC", hash: { name: "SHA-256" } },
false,
["verify"]
);
result = await crypto.subtle.verify(
"HMAC",
key,
hexToArrayBuffer(signature),
encoder.encode(message)
);
return result;
}
/**
* Updates the DNS record with the provided IP
* @param {String} addr
*/
async function updateRecord(addr) {
const base = "https://api.cloudflare.com/client/v4/zones";
const init = { headers: { Authorization: `Bearer ${CF_API_TOKEN}` } };
let record;
let record_res = await fetch(
`${base}/${ZONE}/dns_records?name=${DNS_RECORD}`,
init
);
if (record_res.ok) {
record = (await record_res.json()).result[0];
} else {
console.log("Get record failed");
return;
}
if (record.content != addr) {
init.method = "PATCH";
init.body = JSON.stringify({ content: addr });
await fetch(`${base}/${ZONE}/dns_records/${record.id}`, init);
console.log("Updated record");
} else {
console.log("Record content is the same, skipping update");
}
}
/**
* Transforms an HEX string into an ArrayBuffer
* Original work of: https://github.com/LinusU/hex-to-array-buffer
* @param {String} hex
*/
function hexToArrayBuffer(hex) {
if (typeof hex !== "string") {
throw new TypeError("Expected input to be a string");
}
if (hex.length % 2 !== 0) {
throw new RangeError("Expected string to be an even number of characters");
}
var view = new Uint8Array(hex.length / 2);
for (var i = 0; i < hex.length; i += 2) {
view[i / 2] = parseInt(hex.substring(i, i + 2), 16);
}
return view.buffer;
}
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