Open Source Monorail

appengine/monorail/framework/jsonfeed.py

+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is govered by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+"""This file defines a subclass of Servlet for JSON feeds.
+
+A "feed" is a servlet that is accessed by another part of our system and that
+responds with a JSON value rather than HTML to display in a browser.
+"""
+
+import httplib
+import json
+import logging
+
+from google.appengine.api import app_identity
+
+import settings
+
+from framework import framework_constants
+from framework import permissions
+from framework import servlet
+from framework import xsrf
+
+# This causes a JS error for a hacker trying to do a cross-site inclusion.
+XSSI_PREFIX = ")]}'\n"
+
+
+class JsonFeed(servlet.Servlet):
+  """A convenient base class for JSON feeds."""
+
+  # By default, JSON output is compact.  Subclasses can set this to
+  # an integer, like 4, for pretty-printed output.
+  JSON_INDENT = None
+
+  # Some JSON handlers can only be accessed from our own app.
+  CHECK_SAME_APP = False
+
+  def HandleRequest(self, _mr):
+    """Override this method to implement handling of the request.
+
+    Args:
+      mr: common information parsed from the HTTP request.
+
+    Returns:
+      A dictionary of json data.
+    """
+    raise servlet.MethodNotSupportedError()
+
+  def _DoRequestHandling(self, request, mr):
+    """Do permission checking, page processing, and response formatting."""
+    try:
+      if self.CHECK_SECURITY_TOKEN and mr.auth.user_id:
+        # Validate the XSRF token with the specific request path for this
+        # servlet.  But, not every XHR request has a distinct token, so just
+        # use 'xhr' for ones that don't.
+        # TODO(jrobbins): make specific tokens for:
+        # user and project stars, issue options, check names.
+        try:
+          logging.info('request in jsonfeed is %r', request)
+          xsrf.ValidateToken(mr.token, mr.auth.user_id, request.path)
+        except xsrf.TokenIncorrect:
+          logging.info('using token path "xhr"')
+          xsrf.ValidateToken(mr.token, mr.auth.user_id, xsrf.XHR_SERVLET_PATH)
+
+      if self.CHECK_SAME_APP and not settings.dev_mode:
+        calling_app_id = request.headers.get('X-Appengine-Inbound-Appid')
+        if calling_app_id != app_identity.get_application_id():
+          self.response.status = httplib.FORBIDDEN
+          return
+
+      self._CheckForMovedProject(mr, request)
+      self.AssertBasePermission(mr)
+
+      json_data = self.HandleRequest(mr)
+
+      self._RenderJsonResponse(json_data)
+      raise servlet.AlreadySentResponseException()
+
+    except permissions.PermissionException as e:
+      logging.info('Trapped PermissionException %s', e)
+      self.response.status = httplib.FORBIDDEN
+
+  # pylint: disable=unused-argument
+  # pylint: disable=arguments-differ
+  def get(self, project_name=None, viewed_username=None):
+    """Collect page-specific and generic info, then render the page.
+
+    Args:
+      project_name: string project name parsed from the URL by webapp2,
+        but we also parse it out in our code.
+      viewed_username: string user email parsed from the URL by webapp2,
+        but we also parse it out in our code.
+    """
+    self._DoRequestHandling(self.mr.request, self.mr)
+
+  # pylint: disable=unused-argument
+  # pylint: disable=arguments-differ
+  def post(self, project_name=None, viewed_username=None):
+    """Parse the request, check base perms, and call form-specific code."""
+    self._DoRequestHandling(self.mr.request, self.mr)
+
+  def _RenderJsonResponse(self, json_data):
+    """Serialize the data as JSON so that it can be sent to the browser."""
+    json_str = json.dumps(json_data, indent=self.JSON_INDENT)
+    logging.debug(
+      'Sending JSON response: %r length: %r',
+      json_str[:framework_constants.LOGGING_MAX_LENGTH], len(json_str))
+    self.response.content_type = framework_constants.CONTENT_TYPE_JSON
+    self.response.write(XSSI_PREFIX)
+    self.response.write(json_str)
+
+
+class InternalTask(JsonFeed):
+  """Internal tasks are JSON feeds that can only be reached by our own code."""
+
+  CHECK_SECURITY_TOKEN = False