Respect delay_auth_decision when Keystone is unavailable

The delay_auth_decision option has two main uses:

  1. Allow a service to provide its own auth mechanism, separate from
     auth tokens (like Swift's tempurl middleware).
  2. Allow a service to integrate with multiple auth middlewares which
     may want to use the same X-Auth-Token header.

The first case works fine even when the service has trouble talking to
Keystone -- the client doesn't send an X-Auth-Token header, so we never
even attempt to contact Keystone.

The second case can be problematic, however. The client will provide
some token, and we don't know whether it's valid for Keystone, the other
auth system, or neither. We have to *try* contacting Keystone, but if
that was down we'd previously return a 503 without ever trying the other
auth system. As a result, a Keystone failure results in a total system
failure.

Now, when delay_auth_decision is True and we cannot determine whether a
token is valid or invalid, we'll instead declare the token invalid and
defer the rejection. As a result, Keystone failures only affect Keystone
users, and tokens issued by the other auth system may still be validated
and used.

Change-Id: Ie4b3319862ba7fbd329dc6883ce837e894d5270c

2 files changed, 71 insertions, 0 deletions

diff --git a/keystonemiddleware/auth_token/__init__.py b/keystonemiddleware/auth_token/__init__.py
index 4ac7388..003f14e 100644
--- a/keystonemiddleware/auth_token/__init__.py
+++ b/keystonemiddleware/auth_token/__init__.py
@@ -768,6 +768,11 @@ class AuthProtocol(BaseAuthProtocol):
                 ksm_exceptions.RevocationListError,
                 ksm_exceptions.ServiceError) as e:
             self.log.critical('Unable to validate token: %s', e)
+            if self._delay_auth_decision:
+                self.log.debug('Keystone unavailable; marking token as '
+                               'invalid and deferring auth decision.')
+                raise ksm_exceptions.InvalidToken(
+                    'Keystone unavailable: %s' % e)
             raise webob.exc.HTTPServiceUnavailable(
                 'The Keystone service is temporarily unavailable.')
         except ksm_exceptions.InvalidToken:
diff --git a/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py b/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py
index f9916cc..9051d71 100644
--- a/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py
+++ b/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py
@@ -2043,6 +2043,18 @@ class v3AuthTokenMiddlewareTest(BaseAuthTokenMiddlewareTest,
 
 class DelayedAuthTests(BaseAuthTokenMiddlewareTest):
 
+    def token_response(self, request, context):
+        auth_id = request.headers.get('X-Auth-Token')
+        self.assertEqual(auth_id, FAKE_ADMIN_TOKEN_ID)
+
+        if request.headers.get('X-Subject-Token') == ERROR_TOKEN:
+            msg = 'Network connection refused.'
+            raise ksc_exceptions.ConnectionRefused(msg)
+
+        # All others just fail
+        context.status_code = 404
+        return ''
+
     def test_header_in_401(self):
         body = uuid.uuid4().hex
         www_authenticate_uri = 'http://local.test'
@@ -2101,6 +2113,60 @@ class DelayedAuthTests(BaseAuthTokenMiddlewareTest):
         self.assertFalse(token_auth.has_service_token)
         self.assertIsNone(token_auth.service)
 
+    def test_auth_plugin_with_token(self):
+        self.requests_mock.get('%s/v3/auth/tokens' % BASE_URI,
+                               text=self.token_response,
+                               headers={'X-Subject-Token': uuid.uuid4().hex})
+
+        body = uuid.uuid4().hex
+        www_authenticate_uri = 'http://local.test'
+        conf = {
+            'delay_auth_decision': 'True',
+            'www_authenticate_uri': www_authenticate_uri,
+            'auth_type': 'admin_token',
+            'endpoint': '%s/v3' % BASE_URI,
+            'token': FAKE_ADMIN_TOKEN_ID,
+        }
+
+        middleware = self.create_simple_middleware(body=body, conf=conf)
+        resp = self.call(middleware, headers={
+            'X-Auth-Token': 'non-keystone-token'})
+        self.assertEqual(six.b(body), resp.body)
+
+        token_auth = resp.request.environ['keystone.token_auth']
+
+        self.assertFalse(token_auth.has_user_token)
+        self.assertIsNone(token_auth.user)
+        self.assertFalse(token_auth.has_service_token)
+        self.assertIsNone(token_auth.service)
+
+    def test_auth_plugin_with_token_keystone_down(self):
+        self.requests_mock.get('%s/v3/auth/tokens' % BASE_URI,
+                               text=self.token_response,
+                               headers={'X-Subject-Token': ERROR_TOKEN})
+
+        body = uuid.uuid4().hex
+        www_authenticate_uri = 'http://local.test'
+        conf = {
+            'delay_auth_decision': 'True',
+            'www_authenticate_uri': www_authenticate_uri,
+            'auth_type': 'admin_token',
+            'endpoint': '%s/v3' % BASE_URI,
+            'token': FAKE_ADMIN_TOKEN_ID,
+            'http_request_max_retries': '0'
+        }
+
+        middleware = self.create_simple_middleware(body=body, conf=conf)
+        resp = self.call(middleware, headers={'X-Auth-Token': ERROR_TOKEN})
+        self.assertEqual(six.b(body), resp.body)
+
+        token_auth = resp.request.environ['keystone.token_auth']
+
+        self.assertFalse(token_auth.has_user_token)
+        self.assertIsNone(token_auth.user)
+        self.assertFalse(token_auth.has_service_token)
+        self.assertIsNone(token_auth.service)
+
 
 class CommonCompositeAuthTests(object):
     """Test Composite authentication.