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backends.py
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# Copyright (C) 2020-2021 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU Affero General Public License version 3, or any later version
# See top-level LICENSE file for more information
from datetime import datetime
import hashlib
from typing import Any, Dict, Optional
from django.core.cache import cache
from django.http import HttpRequest
from django.utils import timezone
from rest_framework.authentication import BaseAuthentication
from rest_framework.exceptions import AuthenticationFailed, ValidationError
import sentry_sdk
from swh.auth.django.models import OIDCUser
from swh.auth.django.utils import (
keycloak_oidc_client,
oidc_profile_cache_key,
oidc_user_from_decoded_token,
oidc_user_from_profile,
)
from swh.auth.keycloak import (
ExpiredSignatureError,
KeycloakError,
KeycloakOpenIDConnect,
keycloak_error_message,
)
def _update_cached_oidc_profile(
oidc_client: KeycloakOpenIDConnect, oidc_profile: Dict[str, Any], user: OIDCUser
) -> None:
"""
Update cached OIDC profile associated to a user if needed: when the profile
is not stored in cache or when the authentication tokens have changed.
Args:
oidc_client: KeycloakOpenID wrapper
oidc_profile: OIDC profile used to authenticate a user
user: django model representing the authenticated user
"""
# put OIDC profile in cache or update it after token renewal
cache_key = oidc_profile_cache_key(oidc_client, user.id)
if (
cache.get(cache_key) is None
or user.access_token != oidc_profile["access_token"]
):
# set cache key TTL as refresh token expiration time
assert user.refresh_expires_at
ttl = int(user.refresh_expires_at.timestamp() - timezone.now().timestamp())
# save oidc_profile in cache
cache.set(cache_key, user.oidc_profile, timeout=max(0, ttl))
class OIDCAuthorizationCodePKCEBackend:
"""
Django authentication backend using Keycloak OpenID Connect authorization
code flow with PKCE ("Proof Key for Code Exchange").
To use that backend globally in your django application, proceed as follow:
* add ``"swh.auth.django.backends.OIDCAuthorizationCodePKCEBackend"``
to the ``AUTHENTICATION_BACKENDS`` django setting
* configure Keycloak URL, realm and client by adding
``SWH_AUTH_SERVER_URL``, ``SWH_AUTH_REALM_NAME`` and ``SWH_AUTH_CLIENT_ID``
in django settings
* add ``swh.auth.django.views.urlpatterns`` to your django application URLs
* add an HTML link targeting the ``"oidc-login"`` django view in your
application views
* once a user is logged in, add an HTML link targeting the ``"oidc-logout"``
django view in your application views (a ``next_path`` query parameter
can be used to redirect to a view of choice once the user is logged out)
"""
def authenticate(
self, request: HttpRequest, code: str, code_verifier: str, redirect_uri: str
) -> Optional[OIDCUser]:
user = None
try:
oidc_client = keycloak_oidc_client()
# try to authenticate user with OIDC PKCE authorization code flow
oidc_profile = oidc_client.authorization_code(
code, redirect_uri, code_verifier=code_verifier
)
# create Django user
user = oidc_user_from_profile(oidc_client, oidc_profile)
# update cached oidc profile if needed
_update_cached_oidc_profile(oidc_client, oidc_profile, user)
except Exception as e:
sentry_sdk.capture_exception(e)
return user
def get_user(self, user_id: int) -> Optional[OIDCUser]:
# get oidc profile from cache
oidc_client = keycloak_oidc_client()
oidc_profile = cache.get(oidc_profile_cache_key(oidc_client, user_id))
if oidc_profile:
try:
user = oidc_user_from_profile(oidc_client, oidc_profile)
# update cached oidc profile if needed
_update_cached_oidc_profile(oidc_client, oidc_profile, user)
# restore auth backend
setattr(user, "backend", f"{__name__}.{self.__class__.__name__}")
return user
except Exception as e:
sentry_sdk.capture_exception(e)
return None
else:
return None
class OIDCBearerTokenAuthentication(BaseAuthentication):
"""
Django REST Framework authentication backend using bearer tokens for
Keycloak OpenID Connect.
It enables to authenticate a Web API user by sending a long-lived
OpenID Connect refresh token in HTTP Authorization headers.
Long lived refresh tokens can be generated by opening an OpenID Connect
session with the following scope: ``openid offline_access``.
To use that backend globally in your DRF application, proceed as follow:
* add ``"swh.auth.django.backends.OIDCBearerTokenAuthentication"``
to the ``REST_FRAMEWORK["DEFAULT_AUTHENTICATION_CLASSES"]``
django setting.
* configure Keycloak URL, realm and client by adding
``SWH_AUTH_SERVER_URL``, ``SWH_AUTH_REALM_NAME`` and ``SWH_AUTH_CLIENT_ID``
in django settings
Users will then be able to perform authenticated Web API calls by sending
their refresh token in HTTP Authorization headers, for instance:
``curl -H "Authorization: Bearer ${TOKEN}" https://...``.
"""
def authenticate(self, request):
auth_header = request.META.get("HTTP_AUTHORIZATION")
if auth_header is None:
return None
try:
auth_type, refresh_token = auth_header.split(" ", 1)
except ValueError:
raise AuthenticationFailed("Invalid HTTP authorization header format")
if auth_type != "Bearer":
raise AuthenticationFailed(
(f"Invalid or unsupported HTTP authorization" f" type ({auth_type}).")
)
try:
oidc_client = keycloak_oidc_client()
# compute a cache key from the token that does not exceed
# memcached key size limit
hasher = hashlib.sha1()
hasher.update(refresh_token.encode("ascii"))
cache_key = f"api_token_{hasher.hexdigest()}"
# check if an access token is cached
access_token = cache.get(cache_key)
if access_token is not None:
# attempt to decode access token
try:
decoded_token = oidc_client.decode_token(access_token)
# access token has expired
except ExpiredSignatureError:
decoded_token = None
if access_token is None or decoded_token is None:
# get a new access token from authentication provider
access_token = oidc_client.refresh_token(refresh_token)["access_token"]
# decode access token
decoded_token = oidc_client.decode_token(access_token)
# compute access token expiration
exp = datetime.fromtimestamp(decoded_token["exp"])
ttl = int(exp.timestamp() - timezone.now().timestamp())
# save access token in cache while it is valid
cache.set(cache_key, access_token, timeout=max(0, ttl))
# create Django user
user = oidc_user_from_decoded_token(decoded_token, oidc_client.client_id)
except UnicodeEncodeError as e:
sentry_sdk.capture_exception(e)
raise ValidationError("Invalid bearer token")
except KeycloakError as ke:
error_msg = keycloak_error_message(ke)
if error_msg == "invalid_grant: Offline user session not found":
error_msg = (
"Bearer token expired after a long period of inactivity; "
"please generate a new one."
)
sentry_sdk.capture_exception(ke)
raise AuthenticationFailed(error_msg)
except Exception as e:
sentry_sdk.capture_exception(e)
raise AuthenticationFailed(str(e))
return user, None

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