Support for bearer authentication

[tobixen]

Depended on by tobixen/calendar-cli#81

[azmeuk]

I confirm that Bearer authentication is not supported yet, and that it would be a nice thing to have.

I let this traceback here so people can google it.

  File "/usr/lib/python3.10/site-packages/caldav/davclient.py", line 362, in principal
    self._principal = Principal(client=self, *largs, **kwargs)
  File "/usr/lib/python3.10/site-packages/caldav/objects.py", line 404, in __init__
    cup = self.get_property(dav.CurrentUserPrincipal())
  File "/usr/lib/python3.10/site-packages/caldav/objects.py", line 175, in get_property
    foo = self.get_properties([prop], **passthrough)
  File "/usr/lib/python3.10/site-packages/caldav/objects.py", line 198, in get_properties
    response = self._query_properties(props, depth)
  File "/usr/lib/python3.10/site-packages/caldav/objects.py", line 142, in _query_properties
    return self._query(root, depth)
  File "/usr/lib/python3.10/site-packages/caldav/objects.py", line 160, in _query
    ret = getattr(self.client, query_method)(
  File "/usr/lib/python3.10/site-packages/caldav/davclient.py", line 410, in propfind
    return self.request(url or self.url, "PROPFIND", props,
  File "/usr/lib/python3.10/site-packages/caldav/davclient.py", line 557, in request
    raise NotImplementedError("Auth method %s not supported yet" % auth_type)
NotImplementedError: Auth method bearer not supported yet

[azmeuk]

I suppose implementing would result in:

• storing a token parameter in DAVClient (alongside with username and password). I think this can be expected that users retrieve the token by their own, and that it is not in the scope of python-caldav
• check wether the server supports the bearer authentication method
• if so, and a token has been provided to the library, add a Authorization header which value is Bearer <TOKEN> where <TOKEN> is the token content.

[tobixen]

Yes - it shouldn't be too difficult, if only having a server to test with. Well, there is always the Google servers :-)

[tobixen]

This won't go into v0.10 I'm afraid.

[azmeuk]

This is fixed by #260

[devmount]

Is connecting to a Google CalDAV calendar with OAuth2 already possible? If yes, is there documentation / an example of how to do so? I would like to use this lib for Google calendars as well. Thanks for the great work so far 🙏🏻

[tobixen]

In theory it should be possible, but there exists no documentation or examples on how to connect to Google (and I don't have time looking into it this week nor next, probably not even this month nor next), and pull request #260 also seem to lack documentation and test code.

https://developers.google.com/calendar/caldav/v2/guide seems to be a relevant resource if you want to give it a go.

[devmount]

I see, thank you for the quick reply anyway! I see if I can get it to work or if I need to use another lib for Google (which I would like to avoid).

[tobixen]

I just had a quick look into the documentation - we're still lacking documentation on how to connect to Google. Did anyone successfully connect to their Google calendar?

[seidnerj]

I just had a quick look into the documentation - we're still lacking documentation on how to connect to Google. Did anyone successfully connect to their Google calendar?

yep, here's an example code that does just that:

#!/usr/bin/env python3
import os

from flask import Flask, jsonify, Response
from google.oauth2.credentials import Credentials
from caldav import DAVClient
from caldav.requests import HTTPBearerAuth


app = Flask(__name__)

# Constants
CREDENTIALS_FILE = 'credentials.json'
TOKEN_FILE = 'token.json'
CALDAV_URL_TEMPLATE = 'https://apidata.googleusercontent.com/caldav/v2/{calendar_id}/user'

# Cache to store calendar summaries and IDs
CALENDAR_CACHE = {}


def get_google_credentials():
    """
    Load or refresh Google OAuth2 credentials.
    """

    if os.path.exists(TOKEN_FILE):
        creds = Credentials.from_authorized_user_file(TOKEN_FILE)
    else:
        from google_auth_oauthlib.flow import InstalledAppFlow
        flow = InstalledAppFlow.from_client_secrets_file(
            CREDENTIALS_FILE, scopes=['https://www.googleapis.com/auth/calendar'])
        creds = flow.run_local_server(port=0)

        # save credentials for future use
        with open(TOKEN_FILE, 'w') as token:
            token.write(creds.to_json())

    return creds


def get_calendar_list():
    """
    Fetch the list of calendars and store them in the cache.
    """

    creds = get_google_credentials()
    from googleapiclient.discovery import build
    service = build('calendar', 'v3', credentials=creds)

    calendars = service.calendarList().list().execute()
    for calendar in calendars.get('items', []):
        CALENDAR_CACHE[calendar['summary']] = calendar['id']


@app.route('/calendars', methods=['GET'])
def list_calendars():
    """
    Endpoint to list all available calendars.
    """
    if not CALENDAR_CACHE:
        get_calendar_list()

    return jsonify({'calendars': list(CALENDAR_CACHE.keys())})


@app.route('/calendar/<calendar_name>.ics', methods=['GET'])
def serve_calendar_ics(calendar_name):
    """
    Endpoint to serve .ics data for a specific calendar.
    """
    if calendar_name not in CALENDAR_CACHE:
        return jsonify({'error': 'Calendar not found'}), 404

    calendar_id = CALENDAR_CACHE[calendar_name]
    creds = get_google_credentials()
    access_token = creds.token

    try:
        calendar_url = CALDAV_URL_TEMPLATE.format(calendar_id=calendar_id)

        # connect to the calendar using CalDAV
        client = DAVClient(
            url=calendar_url,
            auth=HTTPBearerAuth(access_token)
        )
        principal = client.principal()
        calendars = principal.calendars()

        # fetch events from the first calendar (usually the only one)
        calendar = calendars[0]
        ics_data = ''
        for event in calendar.events():
            ics_data += event.data

        # serve the calendar as an ICS file
        return Response(ics_data, mimetype='text/calendar')
    except Exception as ex:
        return jsonify({'error': str(ex)}), 500


# requirements: flask, caldav, google-auth, google-auth-oauthlib, google-api-python-client
if __name__ == '__main__':

    # preload calendar list on server start
    get_calendar_list()
    app.run(host='0.0.0.0', port=5000)