diff options
Diffstat (limited to 'opendc-web/opendc-web-api/opendc/auth.py')
| -rw-r--r-- | opendc-web/opendc-web-api/opendc/auth.py | 240 |
1 files changed, 240 insertions, 0 deletions
diff --git a/opendc-web/opendc-web-api/opendc/auth.py b/opendc-web/opendc-web-api/opendc/auth.py new file mode 100644 index 00000000..1870f01c --- /dev/null +++ b/opendc-web/opendc-web-api/opendc/auth.py @@ -0,0 +1,240 @@ +# Copyright (c) 2021 AtLarge Research +# +# Permission is hereby granted, free of charge, to any person obtaining a copy +# of this software and associated documentation files (the "Software"), to deal +# in the Software without restriction, including without limitation the rights +# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +# copies of the Software, and to permit persons to whom the Software is +# furnished to do so, subject to the following conditions: +# +# The above copyright notice and this permission notice shall be included in all +# copies or substantial portions of the Software. +# +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +# SOFTWARE. + +import json +import time + +import urllib3 +from flask import request +from jose import jwt, JWTError + + +def get_token(): + """ + Obtain the Access Token from the Authorization Header + """ + auth = request.headers.get("Authorization", None) + if not auth: + raise AuthError({ + "code": "authorization_header_missing", + "description": "Authorization header is expected" + }, 401) + + parts = auth.split() + + if parts[0].lower() != "bearer": + raise AuthError({ + "code": "invalid_header", + "description": "Authorization header must start with" + " Bearer" + }, 401) + if len(parts) == 1: + raise AuthError({"code": "invalid_header", "description": "Token not found"}, 401) + if len(parts) > 2: + raise AuthError({"code": "invalid_header", "description": "Authorization header must be" " Bearer token"}, 401) + + token = parts[1] + return token + + +class AuthError(Exception): + """ + This error is thrown when the request failed to authorize. + """ + def __init__(self, error, status_code): + Exception.__init__(self, error) + self.error = error + self.status_code = status_code + + +class AuthContext: + """ + This class handles the authorization of requests. + """ + def __init__(self, alg, issuer, audience): + self._alg = alg + self._issuer = issuer + self._audience = audience + + def validate(self, token): + """ + Validate the specified JWT token. + :param token: The authorization token specified by the user. + :return: The token payload on success, otherwise `AuthError`. + """ + try: + header = jwt.get_unverified_header(token) + except JWTError as e: + raise AuthError({"code": "invalid_token", "message": str(e)}, 401) + + alg = header.get('alg', None) + if alg != self._alg.algorithm: + raise AuthError( + { + "code": + "invalid_header", + "message": + f"Signature algorithm of {alg} is not supported. Expected the ID token " + f"to be signed with {self._alg.algorithm}" + }, 401) + + kid = header.get('kid', None) + try: + secret_or_certificate = self._alg.get_key(key_id=kid) + except TokenValidationError as e: + raise AuthError({"code": "invalid_header", "message": str(e)}, 401) + try: + payload = jwt.decode(token, + key=secret_or_certificate, + algorithms=[self._alg.algorithm], + audience=self._audience, + issuer=self._issuer) + return payload + except jwt.ExpiredSignatureError: + raise AuthError({"code": "token_expired", "message": "Token is expired"}, 401) + except jwt.JWTClaimsError: + raise AuthError( + { + "code": "invalid_claims", + "message": "Incorrect claims, please check the audience and issuer" + }, 401) + except Exception as e: + print(e) + raise AuthError({"code": "invalid_header", "message": "Unable to parse authentication token."}, 401) + + +class SymmetricJwtAlgorithm: + """Verifier for HMAC signatures, which rely on shared secrets. + Args: + shared_secret (str): The shared secret used to decode the token. + algorithm (str, optional): The expected signing algorithm. Defaults to "HS256". + """ + def __init__(self, shared_secret, algorithm="HS256"): + self.algorithm = algorithm + self._shared_secret = shared_secret + + # pylint: disable=W0613 + def get_key(self, key_id=None): + """ + Obtain the key for this algorithm. + :param key_id: The identifier of the key. + :return: The JWK key. + """ + return self._shared_secret + + +class AsymmetricJwtAlgorithm: + """Verifier for RSA signatures, which rely on public key certificates. + Args: + jwks_url (str): The url where the JWK set is located. + algorithm (str, optional): The expected signing algorithm. Defaults to "RS256". + """ + def __init__(self, jwks_url, algorithm="RS256"): + self.algorithm = algorithm + self._fetcher = JwksFetcher(jwks_url) + + def get_key(self, key_id=None): + """ + Obtain the key for this algorithm. + :param key_id: The identifier of the key. + :return: The JWK key. + """ + return self._fetcher.get_key(key_id) + + +class TokenValidationError(Exception): + """ + Error thrown when the token cannot be validated + """ + + +class JwksFetcher: + """Class that fetches and holds a JSON web key set. + This class makes use of an in-memory cache. For it to work properly, define this instance once and re-use it. + Args: + jwks_url (str): The url where the JWK set is located. + cache_ttl (str, optional): The lifetime of the JWK set cache in seconds. Defaults to 600 seconds. + """ + CACHE_TTL = 600 # 10 min cache lifetime + + def __init__(self, jwks_url, cache_ttl=CACHE_TTL): + self._jwks_url = jwks_url + self._http = urllib3.PoolManager() + self._cache_value = {} + self._cache_date = 0 + self._cache_ttl = cache_ttl + self._cache_is_fresh = False + + def _fetch_jwks(self, force=False): + """Attempts to obtain the JWK set from the cache, as long as it's still valid. + When not, it will perform a network request to the jwks_url to obtain a fresh result + and update the cache value with it. + Args: + force (bool, optional): whether to ignore the cache and force a network request or not. Defaults to False. + """ + has_expired = self._cache_date + self._cache_ttl < time.time() + + if not force and not has_expired: + # Return from cache + self._cache_is_fresh = False + return self._cache_value + + # Invalidate cache and fetch fresh data + self._cache_value = {} + response = self._http.request('GET', self._jwks_url) + + if response.status == 200: + # Update cache + jwks = json.loads(response.data.decode('utf-8')) + self._cache_value = self._parse_jwks(jwks) + self._cache_is_fresh = True + self._cache_date = time.time() + return self._cache_value + + @staticmethod + def _parse_jwks(jwks): + """Converts a JWK string representation into a binary certificate in PEM format. + """ + keys = {} + + for key in jwks['keys']: + keys[key["kid"]] = key + return keys + + def get_key(self, key_id): + """Obtains the JWK associated with the given key id. + Args: + key_id (str): The id of the key to fetch. + Returns: + the JWK associated with the given key id. + + Raises: + TokenValidationError: when a key with that id cannot be found + """ + keys = self._fetch_jwks() + + if keys and key_id in keys: + return keys[key_id] + + if not self._cache_is_fresh: + keys = self._fetch_jwks(force=True) + if keys and key_id in keys: + return keys[key_id] + raise TokenValidationError(f"RSA Public Key with ID {key_id} was not found.") |