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# Copyright 2016 Google Inc. 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.
"""Sample showing how to validate the Identity-Aware Proxy (IAP) JWT.
This code should be used by applications in Google Compute Engine-based
environments (such as Google App Engine flexible environment, Google
Compute Engine, or Google Container Engine) to provide an extra layer
of assurance that a request was authorized by IAP.
For applications running in the App Engine standard environment, use
App Engine's Users API instead.
"""
# [START iap_validate_jwt]
import jwt
import requests
def validate_iap_jwt(base_url, iap_jwt):
"""Validate a JWT passed to your application by Identity-Aware Proxy.
Args:
base_url: The URL from the incoming request, minus any path, query, etc.
For instance: "https://example.com:8443" or
"https://example.appspot.com" .
iap_jwt: The contents of the X-Goog-Authenticated-User-JWT header.
Returns:
(user_id, user_email, error_str).
"""
try:
key_id = jwt.get_unverified_header(iap_jwt).get('kid')
if not key_id:
return (None, None, '**ERROR: no key ID**')
key = get_iap_key(key_id)
decoded_jwt = jwt.decode(
iap_jwt, key,
algorithms=['ES256'],
audience=base_url)
return (decoded_jwt['sub'], decoded_jwt['email'], '')
except (jwt.exceptions.InvalidTokenError,
requests.exceptions.RequestException) as e:
return (None, None, '**ERROR: JWT validation error {}**'.format(e))
def get_iap_key(key_id):
"""Retrieves a public key from the list published by Identity-Aware Proxy,
re-fetching the key file if necessary.
"""
key_cache = get_iap_key.key_cache
key = key_cache.get(key_id)
if not key:
# Re-fetch the key file.
resp = requests.get(
'https://www.gstatic.com/iap/verify/public_key')
if resp.status_code != 200:
raise Exception(
'Unable to fetch IAP keys: {} / {} / {}'.format(
resp.status_code, resp.headers, resp.text))
key_cache = resp.json()
get_iap_key.key_cache = key_cache
key = key_cache.get(key_id)
if not key:
raise Exception('Key {!r} not found'.format(key_id))
return key
# Used to cache the Identity-Aware Proxy public keys. This code only
# refetches the file when a JWT is signed with a key not present in
# this cache.
get_iap_key.key_cache = {}
# [END iap_validate_jwt]