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# Copyright 2019 Google LLC All Rights Reserved.
#
# Licensed 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 "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# [START getting_started_auth_all]
import sys
from flask import Flask
app = Flask(__name__)
CERTS = None
AUDIENCE = None
# [START getting_started_auth_certs]
def certs():
"""Returns a dictionary of current Google public key certificates for
validating Google-signed JWTs. Since these change rarely, the result
is cached on first request for faster subsequent responses.
"""
import requests
global CERTS
if CERTS is None:
response = requests.get(
'https://www.gstatic.com/iap/verify/public_key'
)
CERTS = response.json()
return CERTS
# [END getting_started_auth_certs]
# [START getting_started_auth_metadata]
def get_metadata(item_name):
"""Returns a string with the project metadata value for the item_name.
See https://cloud.google.com/compute/docs/storing-retrieving-metadata for
possible item_name values.
"""
import requests
endpoint = 'http://metadata.google.internal'
path = '/computeMetadata/v1/project/'
path += item_name
response = requests.get(
'{}{}'.format(endpoint, path),
headers = {'Metadata-Flavor': 'Google'}
)
metadata = response.text
return metadata
# [END getting_started_auth_metadata]
# [START getting_started_auth_audience]
def audience():
"""Returns the audience value (the JWT 'aud' property) for the current
running instance. Since this involves a metadata lookup, the result is
cached when first requested for faster future responses.
"""
global AUDIENCE
if AUDIENCE is None:
project_number = get_metadata('numeric-project-id')
project_id = get_metadata('project-id')
AUDIENCE = '/projects/{}/apps/{}'.format(
project_number, project_id
)
return AUDIENCE
# [END getting_started_auth_audience]
# [START getting_started_auth_validate_assertion]
def validate_assertion(assertion):
"""Checks that the JWT assertion is valid (properly signed, for the
correct audience) and if so, returns strings for the requesting user's
email and a persistent user ID. If not valid, returns None for each field.
"""
from jose import jwt
try:
info = jwt.decode(
assertion,
certs(),
algorithms=['ES256'],
audience=audience()
)
return info['email'], info['sub']
except Exception as e:
print('Failed to validate assertion: {}'.format(e), file=sys.stderr)
return None, None
# [END getting_started_auth_validate_assertion]
# [START getting_started_auth_front_controller]
@app.route('/', methods=['GET'])
def say_hello():
from flask import request
assertion = request.headers.get('X-Goog-IAP-JWT-Assertion')
email, id = validate_assertion(assertion)
page = "<h1>Hello {}</h1>".format(email)
return page
# [END getting_started_auth_front_controller]
# [END getting_started_auth_all]