Merge pull request #2701 from alphagov/jwt-nightmare

Catch uncaught JWT exceptions

app/authentication/auth.py

@@ -1,7 +1,7 @@
 from flask import request, _request_ctx_stack, current_app, g
 from notifications_python_client.authentication import decode_jwt_token, get_token_issuer
 from notifications_python_client.errors import (
-    TokenDecodeError, TokenExpiredError, TokenIssuerError, TokenAlgorithmError
+    TokenDecodeError, TokenExpiredError, TokenIssuerError, TokenAlgorithmError, TokenError
 )
 from notifications_utils import request_helper
 from sqlalchemy.exc import DataError
@@ -10,6 +10,9 @@ from sqlalchemy.orm.exc import NoResultFound
 from app.dao.services_dao import dao_fetch_service_by_id_with_api_keys
 
 
+GENERAL_TOKEN_ERROR_MESSAGE = 'Invalid token: make sure your API token matches the example at https://docs.notifications.service.gov.uk/rest-api.html#authorisation-header'  # noqa
+
+
 class AuthError(Exception):
     def __init__(self, message, code, service_id=None, api_key_id=None):
         self.message = {"token": [message]}
@@ -36,12 +39,12 @@ class AuthError(Exception):
 def get_auth_token(req):
     auth_header = req.headers.get('Authorization', None)
     if not auth_header:
-        raise AuthError('Unauthorized, authentication token must be provided', 401)
+        raise AuthError('Unauthorized: authentication token must be provided', 401)
 
     auth_scheme = auth_header[:7].title()
 
     if auth_scheme != 'Bearer ':
-        raise AuthError('Unauthorized, authentication bearer scheme must be used', 401)
+        raise AuthError('Unauthorized: authentication bearer scheme must be used', 401)
 
     return auth_header[7:]
 
@@ -60,17 +63,17 @@ def requires_admin_auth():
         g.service_id = current_app.config.get('ADMIN_CLIENT_USER_NAME')
         return handle_admin_key(auth_token, current_app.config.get('ADMIN_CLIENT_SECRET'))
     else:
-        raise AuthError('Unauthorized, admin authentication token required', 401)
+        raise AuthError('Unauthorized: admin authentication token required', 401)
 
 
 def requires_auth():
     request_helper.check_proxy_header_before_request()
 
     auth_token = get_auth_token(request)
-    client = __get_token_issuer(auth_token)
+    issuer = __get_token_issuer(auth_token)  # ie the `iss` claim which should be a service ID
 
     try:
-        service = dao_fetch_service_by_id_with_api_keys(client)
+        service = dao_fetch_service_by_id_with_api_keys(issuer)
     except DataError:
         raise AuthError("Invalid token: service id is not the right data type", 403)
     except NoResultFound:
@@ -92,7 +95,15 @@ def requires_auth():
             err_msg = "Invalid token: algorithm used is not HS256"
             raise AuthError(err_msg, 403, service_id=service.id, api_key_id=api_key.id)
         except TokenDecodeError:
+            # we attempted to validate the token but it failed meaning it was not signed using this api key.
+            # Let's try the next one
+            # TODO: Change this so it doesn't also catch `TokenIssuerError` or `TokenIssuedAtError` exceptions (which
+            # are children of `TokenDecodeError`) as these should cause an auth error immediately rather than
+            # continue on to check the next API key
             continue
+        except TokenError:
+            # General error when trying to decode and validate the token
+            raise AuthError(GENERAL_TOKEN_ERROR_MESSAGE, 403, service_id=service.id, api_key_id=api_key.id)
 
         if api_key.expiry_date:
             raise AuthError("Invalid token: API key revoked", 403, service_id=service.id, api_key_id=api_key.id)
@@ -100,7 +111,7 @@ def requires_auth():
         g.service_id = api_key.service_id
         _request_ctx_stack.top.authenticated_service = service
         _request_ctx_stack.top.api_user = api_key
-        current_app.logger.info('API authorised for service {} with api key {}, using client {}'.format(
+        current_app.logger.info('API authorised for service {} with api key {}, using issuer {}'.format(
             service.id,
             api_key.id,
             request.headers.get('User-Agent')
@@ -108,17 +119,17 @@ def requires_auth():
         return
     else:
         # service has API keys, but none matching the one the user provided
-        raise AuthError("Invalid token: signature, api token not found", 403, service_id=service.id)
+        raise AuthError("Invalid token: API key not found", 403, service_id=service.id)
 
 
 def __get_token_issuer(auth_token):
     try:
-        client = get_token_issuer(auth_token)
+        issuer = get_token_issuer(auth_token)
     except TokenIssuerError:
         raise AuthError("Invalid token: iss field not provided", 403)
     except TokenDecodeError:
-        raise AuthError("Invalid token: signature, api token is not valid", 403)
+        raise AuthError(GENERAL_TOKEN_ERROR_MESSAGE, 403)
-    return client
+    return issuer
 
 
 def handle_admin_key(auth_token, secret):
@@ -127,4 +138,4 @@ def handle_admin_key(auth_token, secret):
     except TokenExpiredError:
         raise AuthError("Invalid token: expired, check that your system clock is accurate", 403)
     except TokenDecodeError:
-        raise AuthError("Invalid token: signature, api token is not valid", 403)
+        raise AuthError("Invalid token: could not decode your API token", 403)

app/errors.py

@@ -88,12 +88,12 @@ def register_errors(blueprint):
 
     @blueprint.errorhandler(401)
     def unauthorized(e):
-        error_message = "Unauthorized, authentication token must be provided"
+        error_message = "Unauthorized: authentication token must be provided"
         return jsonify(result='error', message=error_message), 401, [('WWW-Authenticate', 'Bearer')]
 
     @blueprint.errorhandler(403)
     def forbidden(e):
-        error_message = "Forbidden, invalid authentication token provided"
+        error_message = "Forbidden: invalid authentication token provided"
         return jsonify(result='error', message=error_message), 403
 
     @blueprint.errorhandler(429)

requirements.txt

@@ -36,13 +36,13 @@ alembic==1.4.0
 amqp==1.4.9
 anyjson==0.3.3
 attrs==19.3.0
-awscli==1.17.16
+awscli==1.17.17
 bcrypt==3.1.7
 billiard==3.3.0.23
 bleach==3.1.0
 boto==2.49.0
 boto3==1.10.38
-botocore==1.14.16
+botocore==1.14.17
 certifi==2019.11.28
 chardet==3.0.4
 Click==7.0

tests/app/authentication/test_authentication.py

@@ -12,7 +12,7 @@ from notifications_python_client.authentication import create_jwt_token
 from app import api_user
 from app.dao.api_key_dao import get_unsigned_secrets, save_model_api_key, get_unsigned_secret, expire_api_key
 from app.models import ApiKey, KEY_TYPE_NORMAL
-from app.authentication.auth import AuthError, requires_admin_auth, requires_auth
+from app.authentication.auth import AuthError, requires_admin_auth, requires_auth, GENERAL_TOKEN_ERROR_MESSAGE
 
 from tests.conftest import set_config
 
@@ -22,7 +22,7 @@ def test_should_not_allow_request_with_no_token(client, auth_fn):
     request.headers = {}
     with pytest.raises(AuthError) as exc:
         auth_fn()
-    assert exc.value.short_message == 'Unauthorized, authentication token must be provided'
+    assert exc.value.short_message == 'Unauthorized: authentication token must be provided'
 
 
 @pytest.mark.parametrize('auth_fn', [requires_auth, requires_admin_auth])
@@ -30,7 +30,7 @@ def test_should_not_allow_request_with_incorrect_header(client, auth_fn):
     request.headers = {'Authorization': 'Basic 1234'}
     with pytest.raises(AuthError) as exc:
         auth_fn()
-    assert exc.value.short_message == 'Unauthorized, authentication bearer scheme must be used'
+    assert exc.value.short_message == 'Unauthorized: authentication bearer scheme must be used'
 
 
 @pytest.mark.parametrize('auth_fn', [requires_auth, requires_admin_auth])
@@ -38,7 +38,7 @@ def test_should_not_allow_request_with_incorrect_token(client, auth_fn):
     request.headers = {'Authorization': 'Bearer 1234'}
     with pytest.raises(AuthError) as exc:
         auth_fn()
-    assert exc.value.short_message == 'Invalid token: signature, api token is not valid'
+    assert exc.value.short_message == GENERAL_TOKEN_ERROR_MESSAGE
 
 
 @pytest.mark.parametrize('auth_fn', [requires_auth, requires_admin_auth])
@@ -80,7 +80,7 @@ def test_auth_should_not_allow_request_with_no_iat(client, sample_api_key):
     request.headers = {'Authorization': 'Bearer {}'.format(token)}
     with pytest.raises(AuthError) as exc:
         requires_auth()
-    assert exc.value.short_message == 'Invalid token: signature, api token not found'
+    assert exc.value.short_message == 'Invalid token: API key not found'
 
 
 def test_auth_should_not_allow_request_with_non_hs256_algorithm(client, sample_api_key):
@@ -123,7 +123,30 @@ def test_admin_auth_should_not_allow_request_with_no_iat(client, sample_api_key)
     request.headers = {'Authorization': 'Bearer {}'.format(token)}
     with pytest.raises(AuthError) as exc:
         requires_admin_auth()
-    assert exc.value.short_message == 'Invalid token: signature, api token is not valid'
+    assert exc.value.short_message == "Invalid token: could not decode your API token"
+
+
+def test_auth_should_not_allow_request_with_extra_claims(client, sample_api_key):
+    iss = str(sample_api_key.service_id)
+    key = get_unsigned_secrets(sample_api_key.service_id)[0]
+
+    headers = {
+        "typ": 'JWT',
+        "alg": 'HS256'
+    }
+
+    claims = {
+        'iss': iss,
+        'iat': int(time.time()),
+        'aud': 'notifications.service.gov.uk'  # extra claim that we don't support
+    }
+
+    token = jwt.encode(payload=claims, key=key, headers=headers).decode()
+
+    request.headers = {'Authorization': 'Bearer {}'.format(token)}
+    with pytest.raises(AuthError) as exc:
+        requires_auth()
+    assert exc.value.short_message == GENERAL_TOKEN_ERROR_MESSAGE
 
 
 def test_should_not_allow_invalid_secret(client, sample_api_key):
@@ -136,7 +159,7 @@ def test_should_not_allow_invalid_secret(client, sample_api_key):
     )
     assert response.status_code == 403
     data = json.loads(response.get_data())
-    assert data['message'] == {"token": ['Invalid token: signature, api token not found']}
+    assert data['message'] == {"token": ['Invalid token: API key not found']}
 
 
 @pytest.mark.parametrize('scheme', ['bearer', 'Bearer'])
@@ -253,7 +276,7 @@ def test_authentication_returns_error_when_admin_client_has_no_secrets(client):
             headers={'Authorization': 'Bearer {}'.format(token)})
     assert response.status_code == 403
     error_message = json.loads(response.get_data())
-    assert error_message['message'] == {"token": ["Invalid token: signature, api token is not valid"]}
+    assert error_message['message'] == {"token": ["Invalid token: could not decode your API token"]}
 
 
 def test_authentication_returns_error_when_admin_client_secret_is_invalid(client):
@@ -268,7 +291,7 @@ def test_authentication_returns_error_when_admin_client_secret_is_invalid(client
         headers={'Authorization': 'Bearer {}'.format(token)})
     assert response.status_code == 403
     error_message = json.loads(response.get_data())
-    assert error_message['message'] == {"token": ["Invalid token: signature, api token is not valid"]}
+    assert error_message['message'] == {"token": ["Invalid token: could not decode your API token"]}
     current_app.config['ADMIN_CLIENT_SECRET'] = api_secret
 
 

tests/app/v2/notifications/test_post_notifications.py

@@ -256,7 +256,7 @@ def test_post_notification_returns_401_and_well_formed_auth_error(client, sample
     error_resp = json.loads(response.get_data(as_text=True))
     assert error_resp['status_code'] == 401
     assert error_resp['errors'] == [{'error': "AuthError",
-                                     'message': 'Unauthorized, authentication token must be provided'}]
+                                     'message': 'Unauthorized: authentication token must be provided'}]
 
 
 @pytest.mark.parametrize("notification_type, key_send_to, send_to",