Merge remote-tracking branch 'upstream/master'

IPython/html/services/security/__init__.py

@@ -0,0 +1,4 b''
+# URI for the CSP Report. Included here to prevent a cyclic dependency.
+# csp_report_uri is needed both by the BaseHandler (for setting the report-uri)
+# and by the CSPReportHandler (which depends on the BaseHandler).
+csp_report_uri = r"/api/security/csp-report"

IPython/html/services/security/handlers.py

@@ -0,0 +1,23 b''
+"""Tornado handlers for security logging."""
+
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+from tornado import gen, web
+
+from ...base.handlers import IPythonHandler, json_errors
+from . import csp_report_uri
+
+class CSPReportHandler(IPythonHandler):
+    '''Accepts a content security policy violation report'''
+    @web.authenticated
+    @json_errors
+    def post(self):
+        '''Log a content security policy violation report'''
+        csp_report = self.get_json_body()
+        self.log.warn("Content security violation: %s",
+                      self.request.body.decode('utf8', 'replace'))
+
+default_handlers = [
+    (csp_report_uri, CSPReportHandler)
+]

IPython/config/application.py

@@ -6,6 +6,7 b''
 
 from __future__ import print_function
 
+import json
 import logging
 import os
 import re
@@ -535,8 +536,17 b' class Application(SingletonConfigurable):'
     def load_config_file(self, filename, path=None):
         """Load config files by filename and path."""
         filename, ext = os.path.splitext(filename)
+        loaded = []
         for config in self._load_config_files(filename, path=path, log=self.log):
+            loaded.append(config)
             self.update_config(config)
+        if len(loaded) > 1:
+            collisions = loaded[0].collisions(loaded[1])
+            if collisions:
+                self.log.warn("Collisions detected in {0}.py and {0}.json config files."
+                              " {0}.json has higher priority: {1}".format(
+                              filename, json.dumps(collisions, indent=2),
+                ))
 
 
     def generate_config_file(self):

IPython/config/loader.py

@@ -193,7 +193,27 b' class Config(dict):'
                     to_update[k] = copy.deepcopy(v)
 
         self.update(to_update)
-
+    
+    def collisions(self, other):
+        """Check for collisions between two config objects.
+        
+        Returns a dict of the form {"Class": {"trait": "collision message"}}`,
+        indicating which values have been ignored.
+        
+        An empty dict indicates no collisions.
+        """
+        collisions = {}
+        for section in self:
+            if section not in other:
+                continue
+            mine = self[section]
+            theirs = other[section]
+            for key in mine:
+                if key in theirs and mine[key] != theirs[key]:
+                    collisions.setdefault(section, {})
+                    collisions[section][key] = "%r ignored, using %r" % (mine[key], theirs[key])
+        return collisions
+    
     def __contains__(self, key):
         # allow nested contains of the form `"Section.key" in config`
         if '.' in key:
@@ -565,7 +585,7 b' class KeyValueConfigLoader(CommandLineConfigLoader):'
 
 
     def _decode_argv(self, argv, enc=None):
-        """decode argv if bytes, using stin.encoding, falling back on default enc"""
+        """decode argv if bytes, using stdin.encoding, falling back on default enc"""
         uargv = []
         if enc is None:
             enc = DEFAULT_ENCODING

IPython/config/tests/test_loader.py

@@ -1,28 +1,12 b''
 # encoding: utf-8
-"""
-Tests for IPython.config.loader
-
-Authors:
-
-* Brian Granger
-* Fernando Perez (design help)
-"""
+"""Tests for IPython.config.loader"""
 
-#-----------------------------------------------------------------------------
-#  Copyright (C) 2008 The IPython Development Team
-#
-#  Distributed under the terms of the BSD License.  The full license is in
-#  the file COPYING, distributed as part of this software.
-#-----------------------------------------------------------------------------
-
-#-----------------------------------------------------------------------------
-# Imports
-#-----------------------------------------------------------------------------
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
 
 import os
 import pickle
 import sys
-import json
 
 from tempfile import mkstemp
 from unittest import TestCase
@@ -43,10 +27,6 b' from IPython.config.loader import ('
     ConfigError,
 )
 
-#-----------------------------------------------------------------------------
-# Actual tests
-#-----------------------------------------------------------------------------
-
 
 pyfile = """
 c = get_config()
@@ -117,6 +97,34 b' class TestFileCL(TestCase):'
         cl = JSONFileConfigLoader(fname, log=log)
         config = cl.load_config()
         self._check_conf(config)
+    
+    def test_collision(self):
+        a = Config()
+        b = Config()
+        self.assertEqual(a.collisions(b), {})
+        a.A.trait1 = 1
+        b.A.trait2 = 2
+        self.assertEqual(a.collisions(b), {})
+        b.A.trait1 = 1
+        self.assertEqual(a.collisions(b), {})
+        b.A.trait1 = 0
+        self.assertEqual(a.collisions(b), {
+            'A': {
+                'trait1': "1 ignored, using 0",
+            }
+        })
+        self.assertEqual(b.collisions(a), {
+            'A': {
+                'trait1': "0 ignored, using 1",
+            }
+        })
+        a.A.trait2 = 3
+        self.assertEqual(b.collisions(a), {
+            'A': {
+                'trait1': "0 ignored, using 1",
+                'trait2': "2 ignored, using 3",
+            }
+        })
 
     def test_v2raise(self):
         fd, fname = mkstemp('.json')

IPython/html/base/handlers.py

@@ -32,6 +32,8 b' from IPython.utils.path import filefind'
 from IPython.utils.py3compat import string_types
 from IPython.html.utils import is_hidden, url_path_join, url_escape
 
+from IPython.html.services.security import csp_report_uri
+
 #-----------------------------------------------------------------------------
 # Top-level handlers
 #-----------------------------------------------------------------------------
@@ -45,17 +47,22 b' class AuthenticatedHandler(web.RequestHandler):'
     def set_default_headers(self):
         headers = self.settings.get('headers', {})
 
-        if "X-Frame-Options" not in headers:
-            headers["X-Frame-Options"] = "SAMEORIGIN"
+        if "Content-Security-Policy" not in headers:
+            headers["Content-Security-Policy"] = (
+                    "frame-ancestors 'self'; "
+                    # Make sure the report-uri is relative to the base_url
+                    "report-uri " + url_path_join(self.base_url, csp_report_uri) + ";"
+            )
 
+        # Allow for overriding headers
         for header_name,value in headers.items() :
             try:
                 self.set_header(header_name, value)
-            except Exception:
+            except Exception as e:
                 # tornado raise Exception (not a subclass)
                 # if method is unsupported (websocket and Access-Control-Allow-Origin
                 # for example, so just ignore)
-                pass
+                self.log.debug(e)
     
     def clear_login_cookie(self):
         self.clear_cookie(self.cookie_name)

IPython/html/notebookapp.py

@@ -225,7 +225,7 b' class NotebookWebApplication(web.Application):'
         handlers.extend(load_handlers('services.sessions.handlers'))
         handlers.extend(load_handlers('services.nbconvert.handlers'))
         handlers.extend(load_handlers('services.kernelspecs.handlers'))
-        
+        handlers.extend(load_handlers('services.security.handlers'))
         handlers.append(
             (r"/nbextensions/(.*)", FileFindHandler, {
                 'path': settings['nbextensions_path'],

IPython/html/services/config/__init__.py

@@ -0,0 +1,1 b''
+from .manager import ConfigManager

IPython/html/services/kernels/tests/test_kernels_api.py

@@ -65,7 +65,10 b' class KernelAPITest(NotebookTestBase):'
         self.assertEqual(r.status_code, 201)
         self.assertIsInstance(kern1, dict)
 
-        self.assertEqual(r.headers['x-frame-options'], "SAMEORIGIN")
+        self.assertEqual(r.headers['Content-Security-Policy'], (
+                            "frame-ancestors 'self'; "
+                            "report-uri /api/security/csp-report;"
+        ))
 
     def test_main_kernel_handler(self):
         # POST request
@@ -75,7 +78,10 b' class KernelAPITest(NotebookTestBase):'
         self.assertEqual(r.status_code, 201)
         self.assertIsInstance(kern1, dict)
 
-        self.assertEqual(r.headers['x-frame-options'], "SAMEORIGIN")
+        self.assertEqual(r.headers['Content-Security-Policy'], (
+                            "frame-ancestors 'self'; "
+                            "report-uri /api/security/csp-report;"
+        ))
 
         # GET request
         r = self.kern_api.list()

IPython/html/static/services/kernels/kernel.js

@@ -286,16 +286,16 b' define(['
         });
     };
 
-    /**
-     * POST /api/kernels/[:kernel_id]/restart
-     *
-     * Restart the kernel.
-     *
-     * @function interrupt
-     * @param {function} [success] - function executed on ajax success
-     * @param {function} [error] - functon executed on ajax error
-     */
     Kernel.prototype.restart = function (success, error) {
+        /**
+         * POST /api/kernels/[:kernel_id]/restart
+         *
+         * Restart the kernel.
+         *
+         * @function interrupt
+         * @param {function} [success] - function executed on ajax success
+         * @param {function} [error] - functon executed on ajax error
+         */
         this.events.trigger('kernel_restarting.Kernel', {kernel: this});
         this.stop_channels();
 
@@ -327,14 +327,14 b' define(['
         });
     };
 
-    /**
-     * Reconnect to a disconnected kernel. This is not actually a
-     * standard HTTP request, but useful function nonetheless for
-     * reconnecting to the kernel if the connection is somehow lost.
-     *
-     * @function reconnect
-     */
     Kernel.prototype.reconnect = function () {
+        /**
+         * Reconnect to a disconnected kernel. This is not actually a
+         * standard HTTP request, but useful function nonetheless for
+         * reconnecting to the kernel if the connection is somehow lost.
+         *
+         * @function reconnect
+         */
         if (this.is_connected()) {
             return;
         }
@@ -346,15 +346,15 b' define(['
         this.start_channels();
     };
 
-    /**
-     * Handle a successful AJAX request by updating the kernel id and
-     * name from the response, and then optionally calling a provided
-     * callback.
-     *
-     * @function _on_success
-     * @param {function} success - callback
-     */
     Kernel.prototype._on_success = function (success) {
+        /**
+         * Handle a successful AJAX request by updating the kernel id and
+         * name from the response, and then optionally calling a provided
+         * callback.
+         *
+         * @function _on_success
+         * @param {function} success - callback
+         */
         var that = this;
         return function (data, status, xhr) {
             if (data) {
@@ -368,14 +368,14 b' define(['
         };
     };
 
-    /**
-     * Handle a failed AJAX request by logging the error message, and
-     * then optionally calling a provided callback.
-     *
-     * @function _on_error
-     * @param {function} error - callback
-     */
     Kernel.prototype._on_error = function (error) {
+        /**
+         * Handle a failed AJAX request by logging the error message, and
+         * then optionally calling a provided callback.
+         *
+         * @function _on_error
+         * @param {function} error - callback
+         */
         return function (xhr, status, err) {
             utils.log_ajax_error(xhr, status, err);
             if (error) {
@@ -384,27 +384,27 b' define(['
         };
     };
 
-    /**
-     * Perform necessary tasks once the kernel has been started,
-     * including actually connecting to the kernel.
-     *
-     * @function _kernel_created
-     * @param {Object} data - information about the kernel including id
-     */
     Kernel.prototype._kernel_created = function (data) {
+        /**
+         * Perform necessary tasks once the kernel has been started,
+         * including actually connecting to the kernel.
+         *
+         * @function _kernel_created
+         * @param {Object} data - information about the kernel including id
+         */
         this.id = data.id;
         this.kernel_url = utils.url_join_encode(this.kernel_service_url, this.id);
         this.start_channels();
     };
 
-    /**
-     * Perform necessary tasks once the connection to the kernel has
-     * been established. This includes requesting information about
-     * the kernel.
-     *
-     * @function _kernel_connected
-     */
     Kernel.prototype._kernel_connected = function () {
+        /**
+         * Perform necessary tasks once the connection to the kernel has
+         * been established. This includes requesting information about
+         * the kernel.
+         *
+         * @function _kernel_connected
+         */
         this.events.trigger('kernel_connected.Kernel', {kernel: this});
         this.events.trigger('kernel_starting.Kernel', {kernel: this});
         // get kernel info so we know what state the kernel is in
@@ -415,24 +415,24 b' define(['
         });
     };
 
-    /**
-     * Perform necessary tasks after the kernel has died. This closing
-     * communication channels to the kernel if they are still somehow
-     * open.
-     *
-     * @function _kernel_dead
-     */
     Kernel.prototype._kernel_dead = function () {
+        /**
+         * Perform necessary tasks after the kernel has died. This closing
+         * communication channels to the kernel if they are still somehow
+         * open.
+         *
+         * @function _kernel_dead
+         */
         this.stop_channels();
     };
 
-    /**
-     * Start the `shell`and `iopub` channels.
-     * Will stop and restart them if they already exist.
-     *
-     * @function start_channels
-     */
     Kernel.prototype.start_channels = function () {
+        /**
+         * Start the `shell`and `iopub` channels.
+         * Will stop and restart them if they already exist.
+         *
+         * @function start_channels
+         */
         var that = this;
         this.stop_channels();
         var ws_host_url = this.ws_url + this.kernel_url;
@@ -506,29 +506,29 b' define(['
         this.channels.stdin.onmessage = $.proxy(this._handle_input_request, this);
     };
 
-    /**
-     * Handle a websocket entering the open state,
-     * signaling that the kernel is connected when all channels are open.
-     *
-     * @function _ws_opened
-     */
     Kernel.prototype._ws_opened = function (evt) {
+        /**
+         * Handle a websocket entering the open state,
+         * signaling that the kernel is connected when all channels are open.
+         *
+         * @function _ws_opened
+         */
         if (this.is_connected()) {
             // all events ready, trigger started event.
             this._kernel_connected();
         }
     };
 
-    /**
-     * Handle a websocket entering the closed state. This closes the
-     * other communication channels if they are open. If the websocket
-     * was not closed due to an error, try to reconnect to the kernel.
-     *
-     * @function _ws_closed
-     * @param {string} ws_url - the websocket url
-     * @param {bool} error - whether the connection was closed due to an error
-     */
     Kernel.prototype._ws_closed = function(ws_url, error) {
+        /**
+         * Handle a websocket entering the closed state. This closes the
+         * other communication channels if they are open. If the websocket
+         * was not closed due to an error, try to reconnect to the kernel.
+         *
+         * @function _ws_closed
+         * @param {string} ws_url - the websocket url
+         * @param {bool} error - whether the connection was closed due to an error
+         */
         this.stop_channels();
 
         this.events.trigger('kernel_disconnected.Kernel', {kernel: this});
@@ -555,13 +555,13 b' define(['
         }
     };
     
-    /**
-     * Close the websocket channels. After successful close, the value
-     * in `this.channels[channel_name]` will be null.
-     *
-     * @function stop_channels
-     */
     Kernel.prototype.stop_channels = function () {
+        /**
+         * Close the websocket channels. After successful close, the value
+         * in `this.channels[channel_name]` will be null.
+         *
+         * @function stop_channels
+         */
         var that = this;
         var close = function (c) {
             return function () {
@@ -582,15 +582,15 b' define(['
         }
     };
 
-    /**
-     * Check whether there is a connection to the kernel. This
-     * function only returns true if all channel objects have been
-     * created and have a state of WebSocket.OPEN.
-     *
-     * @function is_connected
-     * @returns {bool} - whether there is a connection
-     */
     Kernel.prototype.is_connected = function () {
+        /**
+         * Check whether there is a connection to the kernel. This
+         * function only returns true if all channel objects have been
+         * created and have a state of WebSocket.OPEN.
+         *
+         * @function is_connected
+         * @returns {bool} - whether there is a connection
+         */
         for (var c in this.channels) {
             // if any channel is not ready, then we're not connected
             if (this.channels[c] === null) {
@@ -603,15 +603,15 b' define(['
         return true;
     };
 
-    /**
-     * Check whether the connection to the kernel has been completely
-     * severed. This function only returns true if all channel objects
-     * are null.
-     *
-     * @function is_fully_disconnected
-     * @returns {bool} - whether the kernel is fully disconnected
-     */
     Kernel.prototype.is_fully_disconnected = function () {
+        /**
+         * Check whether the connection to the kernel has been completely
+         * severed. This function only returns true if all channel objects
+         * are null.
+         *
+         * @function is_fully_disconnected
+         * @returns {bool} - whether the kernel is fully disconnected
+         */
         for (var c in this.channels) {
             if (this.channels[c] === null) {
                 return true;
@@ -620,12 +620,12 b' define(['
         return false;
     };
     
-    /**
-     * Send a message on the Kernel's shell channel
-     *
-     * @function send_shell_message
-     */
     Kernel.prototype.send_shell_message = function (msg_type, content, callbacks, metadata, buffers) {
+        /**
+         * Send a message on the Kernel's shell channel
+         *
+         * @function send_shell_message
+         */
         if (!this.is_connected()) {
             throw new Error("kernel is not connected");
         }
@@ -635,17 +635,17 b' define(['
         return msg.header.msg_id;
     };
 
-    /**
-     * Get kernel info
-     *
-     * @function kernel_info
-     * @param callback {function}
-     *
-     * When calling this method, pass a callback function that expects one argument.
-     * The callback will be passed the complete `kernel_info_reply` message documented
-     * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#kernel-info)
-     */
     Kernel.prototype.kernel_info = function (callback) {
+        /**
+         * Get kernel info
+         *
+         * @function kernel_info
+         * @param callback {function}
+         *
+         * When calling this method, pass a callback function that expects one argument.
+         * The callback will be passed the complete `kernel_info_reply` message documented
+         * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#kernel-info)
+         */
         var callbacks;
         if (callback) {
             callbacks = { shell : { reply : callback } };
@@ -653,19 +653,19 b' define(['
         return this.send_shell_message("kernel_info_request", {}, callbacks);
     };
 
-    /**
-     * Get info on an object
-     *
-     * When calling this method, pass a callback function that expects one argument.
-     * The callback will be passed the complete `inspect_reply` message documented
-     * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#object-information)
-     *
-     * @function inspect
-     * @param code {string}
-     * @param cursor_pos {integer}
-     * @param callback {function}
-     */
     Kernel.prototype.inspect = function (code, cursor_pos, callback) {
+        /**
+         * Get info on an object
+         *
+         * When calling this method, pass a callback function that expects one argument.
+         * The callback will be passed the complete `inspect_reply` message documented
+         * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#object-information)
+         *
+         * @function inspect
+         * @param code {string}
+         * @param cursor_pos {integer}
+         * @param callback {function}
+         */
         var callbacks;
         if (callback) {
             callbacks = { shell : { reply : callback } };
@@ -679,56 +679,56 b' define(['
         return this.send_shell_message("inspect_request", content, callbacks);
     };
 
-    /**
-     * Execute given code into kernel, and pass result to callback.
-     *
-     * @async
-     * @function execute
-     * @param {string} code
-     * @param [callbacks] {Object} With the following keys (all optional)
-     *      @param callbacks.shell.reply {function}
-     *      @param callbacks.shell.payload.[payload_name] {function}
-     *      @param callbacks.iopub.output {function}
-     *      @param callbacks.iopub.clear_output {function}
-     *      @param callbacks.input {function}
-     * @param {object} [options]
-     *      @param [options.silent=false] {Boolean}
-     *      @param [options.user_expressions=empty_dict] {Dict}
-     *      @param [options.allow_stdin=false] {Boolean} true|false
-     *
-     * @example
-     *
-     * The options object should contain the options for the execute
-     * call. Its default values are:
-     *
-     *      options = {
-     *        silent : true,
-     *        user_expressions : {},
-     *        allow_stdin : false
-     *      }
-     *
-     * When calling this method pass a callbacks structure of the
-     * form:
-     *
-     *      callbacks = {
-     *       shell : {
-     *         reply : execute_reply_callback,
-     *         payload : {
-     *           set_next_input : set_next_input_callback,
-     *         }
-     *       },
-     *       iopub : {
-     *         output : output_callback,
-     *         clear_output : clear_output_callback,
-     *       },
-     *       input : raw_input_callback
-     *      }
-     *
-     * Each callback will be passed the entire message as a single
-     * arugment.  Payload handlers will be passed the corresponding
-     * payload and the execute_reply message.
-     */
     Kernel.prototype.execute = function (code, callbacks, options) {
+        /**
+         * Execute given code into kernel, and pass result to callback.
+         *
+         * @async
+         * @function execute
+         * @param {string} code
+         * @param [callbacks] {Object} With the following keys (all optional)
+         *      @param callbacks.shell.reply {function}
+         *      @param callbacks.shell.payload.[payload_name] {function}
+         *      @param callbacks.iopub.output {function}
+         *      @param callbacks.iopub.clear_output {function}
+         *      @param callbacks.input {function}
+         * @param {object} [options]
+         *      @param [options.silent=false] {Boolean}
+         *      @param [options.user_expressions=empty_dict] {Dict}
+         *      @param [options.allow_stdin=false] {Boolean} true|false
+         *
+         * @example
+         *
+         * The options object should contain the options for the execute
+         * call. Its default values are:
+         *
+         *      options = {
+         *        silent : true,
+         *        user_expressions : {},
+         *        allow_stdin : false
+         *      }
+         *
+         * When calling this method pass a callbacks structure of the
+         * form:
+         *
+         *      callbacks = {
+         *       shell : {
+         *         reply : execute_reply_callback,
+         *         payload : {
+         *           set_next_input : set_next_input_callback,
+         *         }
+         *       },
+         *       iopub : {
+         *         output : output_callback,
+         *         clear_output : clear_output_callback,
+         *       },
+         *       input : raw_input_callback
+         *      }
+         *
+         * Each callback will be passed the entire message as a single
+         * arugment.  Payload handlers will be passed the corresponding
+         * payload and the execute_reply message.
+         */
         var content = {
             code : code,
             silent : true,

IPython/html/static/widgets/js/manager.js

@@ -101,8 +101,7 b' define(['
                 var parameters = {model: model, options: options};
                 var view = new ViewType(parameters);
                 view.listenTo(model, 'destroy', view.remove);
-                view.render();
-                return view;
+                return Promise.resolve(view.render()).then(function() {return view;});
             }).catch(utils.reject("Couldn't create a view for model id '" + String(model.id) + "'", true));
         });
         return model.state_change;

docs/source/whatsnew/development.rst

@@ -180,16 +180,42 b' Backwards incompatible changes'
 
 .. DO NOT EDIT THIS LINE BEFORE RELEASE. INCOMPAT INSERTION POINT.
 
-IFrame embedding
-````````````````
+Content Security Policy
+```````````````````````
 
-The IPython Notebook and its APIs by default will only be allowed to be
-embedded in an iframe on the same origin.
+The Content Security Policy is a web standard for adding a layer of security to
+detect and mitigate certain classes of attacks, including Cross Site Scripting
+(XSS) and data injection attacks. This was introduced into the notebook to
+ensure that the IPython Notebook and its APIs (by default) can only be embedded
+in an iframe on the same origin.
 
-To override this, set ``headers[X-Frame-Options]`` to one of
+Override ``headers['Content-Security-Policy']`` within your notebook
+configuration to extend for alternate domains and security settings.::
 
-* DENY
-* SAMEORIGIN
-* ALLOW-FROM uri
+    c.NotebookApp.tornado_settings = {
+        'headers': {
+            'Content-Security-Policy': "frame-ancestors 'self'"
+        }
+    }
 
-See `Mozilla's guide to X-Frame-Options <https://developer.mozilla.org/en-US/docs/Web/HTTP/X-Frame-Options>`_ for more examples.
+Example policies::
+
+    Content-Security-Policy: default-src 'self' https://*.jupyter.org
+
+Matches embeddings on any subdomain of jupyter.org, so long as they are served
+over SSL.
+
+There is a `report-uri <https://developer.mozilla.org/en-US/docs/Web/Security/CSP/CSP_policy_directives#report-uri>`_ endpoint available for logging CSP violations, located at
+``/api/security/csp-report``. To use it, set ``report-uri`` as part of the CSP::
+
+    c.NotebookApp.tornado_settings = {
+        'headers': {
+            'Content-Security-Policy': "frame-ancestors 'self'; report-uri /api/security/csp-report"
+        }
+    }
+
+It simply provides the CSP report as a warning in IPython's logs. The default
+CSP sets this report-uri relative to the ``base_url`` (not shown above).
+
+For a more thorough and accurate guide on Content Security Policies, check out
+`MDN's Using Content Security Policy <https://developer.mozilla.org/en-US/docs/Web/Security/CSP/Using_Content_Security_Policy>`_ for more examples.