an example of a python fido2 webauthn client wrapping webauthn.io. fork of https://github.com/Yubico/python-fido2/blob/main/examples/credential.py

python-fido2-webauthn-client.py

#!/usr/bin/env python3

# Copyright (c) 2024 Yubico AB
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"""
Connects to the first FIDO device found (starts from USB, then looks into NFC),
creates a new credential for it, and authenticates the credential.
This works with both FIDO 2.0 devices as well as with U2F devices.
On Windows, the native WebAuthn API will be used.
"""

import string
import random

import requests
import logging
import sys

from fido2.hid import CtapHidDevice
from fido2.client import Fido2Client, WindowsClient, UserInteraction, ClientError
from fido2.webauthn import PublicKeyCredentialDescriptor
from fido2.utils import websafe_decode, websafe_encode
from getpass import getpass
import ctypes

# FIDO2

try:
    from fido2.pcsc import CtapPcscDevice
except ImportError:
    CtapPcscDevice = None

# Handle user interaction via CLI prompts
class CliInteraction(UserInteraction):
    def __init__(self):
        self._pin = None

    def prompt_up(self):
        logging.info('Touch your authenticator device now ...')

    def request_pin(self, permissions, rd_id):
        if not self._pin:
            self._pin = getpass("Enter PIN: ")
        return self._pin

    def request_uv(self, permissions, rd_id):
        logging.info('User Verification required.')
        return True

def enumerate_devices():
    for dev in CtapHidDevice.list_devices():
        yield dev
    if CtapPcscDevice:
        for dev in CtapPcscDevice.list_devices():
            yield dev

def get_client(**kwargs):
    """Locate a CTAP device suitable for use.

    If running on Windows as non-admin, the predicate check will be skipped and
    a webauthn.dll based client will be returned.

    Extra kwargs will be passed to the constructor of Fido2Client.
    """
    if WindowsClient.is_available() and not ctypes.windll.shell32.IsUserAnAdmin():
        # Use the Windows WebAuthn API if available, and we're not running as admin
        return WindowsClient("https://example.com")

    # Locate a device
    for device in enumerate_devices():
        # Set up a FIDO 2 client using the origin https://example.com
        client = Fido2Client(
            device=device,
            user_interaction=CliInteraction(),
            **kwargs,
        )
        # Check if it is suitable for use
        if client:
            return client
    raise ValueError("No suitable Authenticator found!")

# webauthn.io

def generate_random_string(length=32):
    characters = string.ascii_letters + string.digits
    return ''.join(random.choices(characters, k=length))

COOKIES = {
    'csrftoken': generate_random_string(32),
    'sessionid': generate_random_string(32),
}

session = requests.Session()

def response_hook(request, *args, **kwargs):
    try:
        request.raise_for_status()
    except:
        logging.error('Failed %s request to %s', request.request.method, request.request.url)
        logging.error('%s', request.text)
        raise

session.hooks = {'response': response_hook}

def get_options(username):
    data = {
        'username': username,
        'user_verification': 'required',
    }

    response = session.post('https://webauthn.io/authentication/options', cookies=COOKIES, json=data)
    return response.json()

def respond(username, result):
    data = {
        'username': username,
        'response': {
            'authenticatorAttachment': 'cross-platform',
            'clientExtensionResults': {},
            'id': websafe_encode(result['credentialId']),
            'rawId': websafe_encode(result['credentialId']),
            'type': 'public-key',
            'response': {
                'clientDataJSON': websafe_encode(result['clientDataJSON']),
                'authenticatorData': websafe_encode(result['authenticatorData']),
                'signature': websafe_encode(result['signature']),
                'userHandle': websafe_encode(result['userHandle']),
            },
        },
    }

    response = session.post('https://webauthn.io/authentication/verification', cookies=COOKIES, json=data)
    return response.json()

def main(username):
    client = get_client(origin='https://webauthn.io')
    logging.info('Getting options from webauthn.io')
    options = get_options(username)

    request_options = {
        'rpId': options['rpId'],
        'challenge': websafe_decode(options['challenge']),
        'timeout': 600000,
        'allowCredentials': [PublicKeyCredentialDescriptor(type=cred['type'], id=websafe_decode(cred['id']), transports=cred['transports']) for cred in options['allowCredentials']],
        'userVerification': options['userVerification'],
    }
    logging.debug('Requesting to sign challenge: %s with key(s): %s', options['challenge'], options['allowCredentials'])
    result = client.get_assertion(request_options)
    result = result.get_response(0)
    logging.info('Received credential from device')
    logging.debug('Credential result: %s', result)

    logging.info('Responding to webauthn.io')
    response = respond(username, result)
    logging.info('Received response: %s', response)
    assert response['verified'] == True


if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('username')
    parser.add_argument('-l', '--log', choices=('debug', 'info', 'warning', 'error', 'critical'), default='info', help="Logging level (default: %(default)s)")
    args = parser.parse_args()
    logging.basicConfig(level=getattr(logging, args.log.upper()), format='%(levelname)s\t%(message)s')
    try:
        sys.exit(main(args.username))
    except ClientError as e:
        logging.error('FIDO2 error: %s', e.cause)
        logging.debug(e, exc_info=True)
        sys.exit(1)
    except KeyboardInterrupt:
        pass