Add a Content Security Policy

.github/workflows/ci.yml

@@ -70,6 +70,7 @@ jobs:
           cp config/secrets.yml.ci config/secrets.yml
           cp config/docker.yml.erb.ci config/docker.yml.erb
           cp config/mnemosyne.yml.ci config/mnemosyne.yml
+          cp config/content_security_policy.yml.ci config/content_security_policy.yml
 
       - name: Create database
         env:

.gitignore

@@ -4,6 +4,7 @@
 /config/mnemosyne.yml
 /config/secrets.yml
 /config/docker.yml.erb
+/config/content_security_policy.yml
 /coverage
 /log/*.*
 /public/assets

app/views/exercises/feedback.html.slim

@@ -36,4 +36,5 @@ h1 = link_to_if(policy(@exercise).show?, @exercise, exercise_path(@exercise))
 
   = render('shared/pagination', collection: @feedbacks)
 
-  script type="text/javascript" $(function () { $('[data-bs-toggle="tooltip"]').tooltip() });
+  = javascript_tag nonce: true do
+    | $(function () { $('[data-bs-toggle="tooltip"]').tooltip() });

app/views/layouts/application.html.slim

@@ -15,8 +15,8 @@ html lang="#{I18n.locale || I18n.default_locale}"
     = javascript_include_tag('application', 'data-turbolinks-track': true)
     = yield(:head)
     = csrf_meta_tags
-    = timeago_script_tag
+    = timeago_script_tag nonce: true
-    script type="text/javascript"
+    = javascript_tag nonce: true do
       | I18n.defaultLocale = "#{I18n.default_locale}";
       | I18n.locale = "#{I18n.locale}";
       - if SentryJavascript.active?

app/views/request_for_comments/show.html.slim

@@ -79,7 +79,7 @@
 
 = render('shared/modal', id: 'comment-modal', title: t('exercises.implement.comment.dialogtitle'), template: 'exercises/_comment_dialogcontent')
 
-javascript:
+javascript [nonce=content_security_policy_nonce]:
 
   $('.modal-content').draggable({
     handle: '.modal-header'

config/content_security_policy.yml.ci

@@ -0,0 +1,18 @@
+default: &default
+  default_src: []
+
+
+development:
+  <<: *default
+  # Allow the webpack-dev-server in development
+  connect_src:
+    - http://localhost:3035
+    - ws://localhost:3035
+
+
+production:
+  <<: *default
+
+
+test:
+  <<: *default

config/content_security_policy.yml.example

@@ -0,0 +1,29 @@
+# This file allows to further customize the Content Security Policy (CSP)
+# All settings will be applied **in addition** to the application CSP
+# Default directives are defined here: `initializers/content_security_policy.rb`
+
+default: &default
+  # Allow the S3 service hosted by the openHPI Cloud to be used for images
+  img_src:
+    - https://s3.xopic.de
+    - https://*.s3.xopic.de
+    - https://s3.openhpicloud.de
+    - https://*.s3.openhpicloud.de
+  # Optionally: Specify a custom, non-Sentry URL for reporting CSP violations
+  # report_uri: https://example.com/csp-report
+
+
+development:
+  <<: *default
+  # Allow the webpack-dev-server in development
+  connect_src:
+    - http://localhost:3035
+    - ws://localhost:3035
+
+
+production:
+  <<: *default
+
+
+test:
+  <<: *default

config/initializers/content_security_policy.rb

@@ -6,28 +6,57 @@
 # For further information see the following documentation
 # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
 
-# Rails.application.config.content_security_policy do |policy|
+require_relative 'sentry_csp'
-#   # If you are using webpack-dev-server then specify webpack-dev-server host
+require_relative 'sentry_javascript'
-#   policy.connect_src :self, :https, "http://localhost:3035", "ws://localhost:3035" if Rails.env.development?
 
-#   policy.default_src :self, :https
+def self.apply_yml_settings_for(policy)
-#   policy.font_src    :self, :https, :data
+  csp_settings = CodeOcean::Config.new(:content_security_policy)
-#   policy.img_src     :self, :https, :data
-#   policy.object_src  :none
-#   policy.script_src  :self, :https
-#   policy.style_src   :self, :https
-#   # If you are using webpack-dev-server then specify webpack-dev-server host
-#   policy.connect_src :self, :https, "http://localhost:3035", "ws://localhost:3035" if Rails.env.development?
 
-#   # Specify URI for violation reports
+  csp_settings.read.each do |directive, additional_settings|
-#   # policy.report_uri "/csp-violation-report-endpoint"
+    existing_settings = if directive == 'report_uri'
-# end
+                          ''
+                        else
+                          policy.public_send(directive) || []
+                        end
+    all_settings = existing_settings + additional_settings
+    policy.public_send(directive, *all_settings)
+  end
+end
+
+def self.apply_sentry_settings_for(policy)
+  sentry_domain = URI.parse SentryJavascript.dsn
+  additional_setting = "#{sentry_domain.scheme}://#{sentry_domain.host}"
+  existing_settings = policy.connect_src || []
+  all_settings = existing_settings + [additional_setting]
+  policy.connect_src(*all_settings)
+end
+
+Rails.application.config.content_security_policy do |policy|
+  policy.default_src          :none
+  policy.base_uri             :none
+  policy.font_src             :self
+  # Code executions might return a base64 encoded image as a :data URI
+  policy.img_src              :self, :data
+  policy.object_src           :none
+  policy.script_src           :self, :report_sample
+  # Our ACE editor unfortunately requires :unsafe_inline for the code highlighting
+  policy.style_src            :self, :unsafe_inline, :report_sample
+  policy.connect_src          :self
+  policy.form_action          :self
+  policy.frame_ancestors      :none
+
+  # Specify URI for violation reports
+  policy.report_uri           SentryCsp.report_url if SentryCsp.active?
+
+  apply_yml_settings_for      policy
+  apply_sentry_settings_for   policy if SentryJavascript.active?
+end
 
 # If you are using UJS then enable automatic nonce generation
-# Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
+Rails.application.config.content_security_policy_nonce_generator = ->(request) { request.session.id.to_s }
 
 # Set the nonce only to specific directives
-# Rails.application.config.content_security_policy_nonce_directives = %w(script-src)
+Rails.application.config.content_security_policy_nonce_directives = %w[script-src]
 
 # Report CSP violations to a specified URI
 # For further information see the following documentation:

config/initializers/sentry_csp.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require_relative 'sentry'
+
+class SentryCsp
+  def self.active?
+    dsn.present? && %w[development test].exclude?(environment)
+  end
+
+  def self.report_url
+    parsed_url = URI.parse dsn
+
+    # Add additional variables to the query string
+    query_params = CGI.parse(parsed_url.query || '')
+    query_params[:sentry_release] = release if release
+    query_params[:sentry_environment] = environment if environment
+
+    # Add the query string back to the URL
+    parsed_url.query = URI.encode_www_form(query_params)
+
+    # Return the full URL
+    parsed_url.to_s
+  end
+
+  class << self
+    private
+
+    def dsn
+      ENV.fetch('SENTRY_CSP_REPORT_URL', nil)
+    end
+
+    def release
+      Sentry.configuration.release
+    end
+
+    def environment
+      Sentry.configuration.environment
+    end
+  end
+end

config/initializers/sentry_javascript.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require_relative 'sentry'
+
 class SentryJavascript
   def self.active?
     dsn.present? && %w[development test].exclude?(environment)

docs/LOCAL_SETUP.md

@@ -194,7 +194,7 @@ source "$HOME/.profile"
 - Create all necessary config files:
 
   ```bash
-  for f in action_mailer.yml database.yml secrets.yml code_ocean.yml docker.yml.erb mnemosyne.yml
+  for f in action_mailer.yml database.yml secrets.yml code_ocean.yml docker.yml.erb mnemosyne.yml content_security_policy.yml
   do
     if [ ! -f config/$f ]
     then
@@ -303,7 +303,7 @@ source "$HOME/.profile"
   ```
 - Get a local copy of the config files and verify the settings:
   ```shell script
-  for f in action_mailer.yml database.yml secrets.yml code_ocean.yml docker.yml.erb mnemosyne.yml
+  for f in action_mailer.yml database.yml secrets.yml code_ocean.yml docker.yml.erb mnemosyne.yml content_security_policy.yml
   do
     if [ ! -f config/$f ]
     then

provision/provision.vagrant.sh

@@ -92,7 +92,7 @@ gem install bundler
 cd /home/vagrant/codeocean
 
 # config
-for f in action_mailer.yml database.yml secrets.yml docker.yml.erb mnemosyne.yml
+for f in action_mailer.yml database.yml secrets.yml docker.yml.erb mnemosyne.yml content_security_policy.yml
 do
   if [ ! -f config/$f ]
   then