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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
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import logging
from importlib import import_module

from airflow.configuration import conf
from airflow.exceptions import AirflowConfigException, AirflowException

log = logging.getLogger(__name__)


def init_xframe_protection(app):
    """
    Add X-Frame-Options header. Use it to avoid click-jacking attacks, by ensuring that their content is not
    embedded into other sites.

    See also: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
    """
    x_frame_enabled = conf.getboolean('webserver', 'X_FRAME_ENABLED', fallback=True)
    if not x_frame_enabled:
        return

    def apply_caching(response):
        response.headers["X-Frame-Options"] = "DENY"
        return response

    app.after_request(apply_caching)


def init_api_experimental_auth(app):
    """Loads authentication backend"""
    auth_backend = 'airflow.api.auth.backend.default'
    try:
        auth_backend = conf.get("api", "auth_backend")
    except AirflowConfigException:
        pass

    try:
        app.api_auth = import_module(auth_backend)
        app.api_auth.init_app(app)
    except ImportError as err:
        log.critical("Cannot import %s for API authentication due to: %s", auth_backend, err)
        raise AirflowException(err)