Limit the size of HTTP requests.

Adds a new RequestBodySizeLimiter middleware to guard against
really large HTTP requests. The default max request size is 112k
although this limit is configurable via the 'max_request_body_size'
config parameter.

Fixes LP Bug #1099025.

Change-Id: Id51be3d9a0d829d63d55a92dca61a39a17629785

etc/keystone.conf.sample

@@ -186,6 +186,9 @@ paste.filter_factory = keystone.contrib.s3:S3Extension.factory
 [filter:url_normalize]
 paste.filter_factory = keystone.middleware:NormalizingFilter.factory
 
+[filter:sizelimit]
+paste.filter_factory = keystone.middleware:RequestBodySizeLimiter.factory
+
 [filter:stats_monitoring]
 paste.filter_factory = keystone.contrib.stats:StatsMiddleware.factory
 
@@ -202,13 +205,13 @@ paste.app_factory = keystone.service:v3_app_factory
 paste.app_factory = keystone.service:admin_app_factory
 
 [pipeline:public_api]
-pipeline = stats_monitoring url_normalize token_auth admin_token_auth xml_body json_body debug ec2_extension user_crud_extension public_service
+pipeline = sizelimit stats_monitoring url_normalize token_auth admin_token_auth xml_body json_body debug ec2_extension user_crud_extension public_service
 
 [pipeline:admin_api]
-pipeline = stats_monitoring url_normalize token_auth admin_token_auth xml_body json_body debug stats_reporting ec2_extension s3_extension crud_extension admin_service
+pipeline = sizelimit stats_monitoring url_normalize token_auth admin_token_auth xml_body json_body debug stats_reporting ec2_extension s3_extension crud_extension admin_service
 
 [pipeline:api_v3]
-pipeline = stats_monitoring url_normalize token_auth admin_token_auth xml_body json_body debug stats_reporting ec2_extension s3_extension service_v3
+pipeline = sizelimit stats_monitoring url_normalize token_auth admin_token_auth xml_body json_body debug stats_reporting ec2_extension s3_extension service_v3
 
 [app:public_version_service]
 paste.app_factory = keystone.service:public_version_app_factory
@@ -217,10 +220,10 @@ paste.app_factory = keystone.service:public_version_app_factory
 paste.app_factory = keystone.service:admin_version_app_factory
 
 [pipeline:public_version_api]
-pipeline = stats_monitoring url_normalize xml_body public_version_service
+pipeline = sizelimit stats_monitoring url_normalize xml_body public_version_service
 
 [pipeline:admin_version_api]
-pipeline = stats_monitoring url_normalize xml_body admin_version_service
+pipeline = sizelimit stats_monitoring url_normalize xml_body admin_version_service
 
 [composite:main]
 use = egg:Paste#urlmap

keystone/common/utils.py

@@ -311,3 +311,37 @@ def setup_remote_pydev_debug():
         except:
             LOG.exception(_(error_msg))
             raise
+
+
+class LimitingReader(object):
+    """Reader to limit the size of an incoming request."""
+    def __init__(self, data, limit):
+        """
+        :param data: Underlying data object
+        :param limit: maximum number of bytes the reader should allow
+        """
+        self.data = data
+        self.limit = limit
+        self.bytes_read = 0
+
+    def __iter__(self):
+        for chunk in self.data:
+            self.bytes_read += len(chunk)
+            if self.bytes_read > self.limit:
+                raise exception.RequestTooLarge()
+            else:
+                yield chunk
+
+    def read(self, i):
+        result = self.data.read(i)
+        self.bytes_read += len(result)
+        if self.bytes_read > self.limit:
+            raise exception.RequestTooLarge()
+        return result
+
+    def read(self):
+        result = self.data.read()
+        self.bytes_read += len(result)
+        if self.bytes_read > self.limit:
+            raise exception.RequestTooLarge()
+        return result

keystone/config.py

@@ -137,6 +137,8 @@ register_str('onready')
 register_str('auth_admin_prefix', default='')
 register_str('policy_file', default='policy.json')
 register_str('policy_default_rule', default=None)
+#default max request size is 112k
+register_int('max_request_body_size', default=114688)
 
 #ssl options
 register_bool('enable', group='ssl', default=False)

keystone/exception.py

@@ -173,6 +173,12 @@ class Conflict(Error):
     title = 'Conflict'
 
 
+class RequestTooLarge(Error):
+    """Request is too large."""
+    code = 413
+    title = 'Request is too large.'
+
+
 class UnexpectedError(Error):
     """An unexpected error prevented the server from fulfilling your request.
 

keystone/middleware/core.py

@@ -14,7 +14,10 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import webob.dec
+
 from keystone.common import serializer
+from keystone.common import utils
 from keystone.common import wsgi
 from keystone import config
 from keystone import exception
@@ -164,3 +167,21 @@ class NormalizingFilter(wsgi.Middleware):
         # Rewrites path to root if no path is given.
         elif not request.environ['PATH_INFO']:
             request.environ['PATH_INFO'] = '/'
+
+
+class RequestBodySizeLimiter(wsgi.Middleware):
+    """Limit the size of an incoming request."""
+
+    def __init__(self, *args, **kwargs):
+        super(RequestBodySizeLimiter, self).__init__(*args, **kwargs)
+
+    @webob.dec.wsgify(RequestClass=wsgi.Request)
+    def __call__(self, req):
+
+        if req.content_length > CONF.max_request_body_size:
+            raise exception.RequestTooLarge()
+        if req.content_length is None and req.is_body_readable:
+            limiter = utils.LimitingReader(req.body_file,
+                                           CONF.max_request_body_size)
+            req.body_file = limiter
+        return self.application

tests/test_sizelimit.py

@@ -0,0 +1,56 @@
+# Copyright (c) 2013 OpenStack, LLC
+#
+#    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.
+
+import webob
+
+from keystone import config
+from keystone import exception
+from keystone import middleware
+from keystone import test
+
+CONF = config.CONF
+MAX_REQUEST_BODY_SIZE = CONF.max_request_body_size
+
+
+class TestRequestBodySizeLimiter(test.TestCase):
+
+    def setUp(self):
+        super(TestRequestBodySizeLimiter, self).setUp()
+
+        @webob.dec.wsgify()
+        def fake_app(req):
+            return webob.Response(req.body)
+
+        self.middleware = middleware.RequestBodySizeLimiter(fake_app)
+        self.request = webob.Request.blank('/', method='POST')
+
+    def test_content_length_acceptable(self):
+        self.request.headers['Content-Length'] = MAX_REQUEST_BODY_SIZE
+        self.request.body = "0" * MAX_REQUEST_BODY_SIZE
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(response.status_int, 200)
+
+    def test_content_length_too_large(self):
+        self.request.headers['Content-Length'] = MAX_REQUEST_BODY_SIZE + 1
+        self.request.body = "0" * (MAX_REQUEST_BODY_SIZE + 1)
+        self.assertRaises(exception.RequestTooLarge,
+                          self.request.get_response,
+                          self.middleware)
+
+    def test_request_too_large_no_content_length(self):
+        self.request.body = "0" * (MAX_REQUEST_BODY_SIZE + 1)
+        self.request.headers['Content-Length'] = None
+        self.assertRaises(exception.RequestTooLarge,
+                          self.request.get_response,
+                          self.middleware)