app/webhooks/__init__.py

   1 """
   2 This is the webhook server that interfaces with Google's WebSub (formerly
   3 pubsubhubbub) server. This can be run either as a module on the main frontend,
   4 or as its own server, so it can live on a different host than the frontend.
   5 """
   6
   7 import time
   8 import sqlite3
   9 from flask import Flask, Blueprint, request
  10 from urllib.parse import parse_qs, urlparse
  11
  12 from ..common.common import *
  13 from ..common.anticsrf import no_csrf_protection
  14
  15 frontend = Blueprint('webhooks', __name__)
  16
  17 def app():
  18     app = Flask(__name__)
  19     app.register_blueprint(frontend)
  20     return app
  21
  22 @frontend.route('/websub')
  23 def index():
  24     return '', 204 # No Content
  25
  26 @frontend.route('/websub/v1/<int:timestamp>/<nonce>/<subject>/<sig>', methods=["GET"])
  27 def websub(timestamp, nonce, subject, sig):
  28     hmackey = cf['websub']['hmac_key']
  29     mode = request.args.get('hub.mode', '')
  30     topic = request.args.get('hub.topic', '')
  31     challenge = request.args.get('hub.challenge', '')
  32     until = int(request.args.get('hub.lease_seconds', '0'))
  33
  34     if sig != websub_url_hmac(hmackey, subject, timestamp, nonce):
  35         return '', 400
  36
  37     if time.time() - timestamp > int(cf['websub']['lease']):
  38         return '', 400
  39
  40     if mode != "subscribe":
  41         return '', 200
  42         # Note: channels are not purged from the websub dbtable.
  43
  44     with sqlite3.connect(cf['global']['database']) as conn:
  45         c = conn.cursor()
  46         c.execute("""
  47                 INSERT OR REPLACE INTO websub (channel_id, subscribed_until)
  48                            VALUES (?, datetime(?, 'unixepoch'))
  49         """, (subject, time.time()+until))
  50     return challenge, 200
  51
  52 @frontend.route('/websub/v1/<int:timestamp>/<nonce>/<subject>/<sig>', methods=["POST"])
  53 @no_csrf_protection
  54 def websub_post(timestamp, nonce, subject, sig):
  55     lease = cf['websub']['lease']
  56     hmackey = cf['websub']['hmac_key']
  57     hub_signature = request.headers.get('X-Hub-Signature').replace("sha1=", "")
  58
  59     if sig != websub_url_hmac(hmackey, subject, timestamp, nonce):
  60         return '', 400
  61     if hub_signature != websub_body_hmac(hmackey, request.data):
  62         return '', 400
  63
  64     with sqlite3.connect(cf['global']['database']) as conn:
  65         c = conn.cursor()
  66         try:
  67             update_channel(conn, request.data, from_webhook=True)
  68         except Exception as e:
  69             with open('/tmp/websub-subscriptions.err', 'ab') as f:
  70                 f.write(f"<!-- {time.ctime()} ({int(time.time())}) -->\n".encode('ascii'))
  71                 f.write(request.data + b"\n")
  72             raise e
  73     return '', 200
  74
  75 if __name__ == '__main__':
  76     app().run(debug=True)