From 31abee0341cb9d19f0234da7b42dddbabfcd1d4a Mon Sep 17 00:00:00 2001 From: Andrew White Date: Fri, 16 Feb 2018 13:21:48 +0000 Subject: [PATCH] Add support for automatic nonce generation for Rails UJS Because the UJS library creates a script tag to process responses it normally requires the script-src attribute of the content security policy to include 'unsafe-inline'. To work around this we generate a per-request nonce value that is embedded in a meta tag in a similar fashion to how CSRF protection embeds its token in a meta tag. The UJS library can then read the nonce value and set it on the dynamically generated script tag to enable it to execute without needing 'unsafe-inline' enabled. Nonce generation isn't 100% safe - if your script tag is including user generated content in someway then it may be possible to exploit an XSS vulnerability which can take advantage of the nonce. It is however an improvement on a blanket permission for inline scripts. It is also possible to use the nonce within your own script tags by using `nonce: true` to set the nonce value on the tag, e.g <%= javascript_tag nonce: true do %> alert('Hello, World!'); <% end %> Fixes #31689. --- actionpack/CHANGELOG.md | 28 +++++++ .../metal/content_security_policy.rb | 18 +++++ .../http/content_security_policy.rb | 32 ++++++++ .../dispatch/content_security_policy_test.rb | 16 ++++ .../javascripts/rails-ujs/utils/ajax.coffee | 4 +- .../javascripts/rails-ujs/utils/csp.coffee | 4 + actionview/lib/action_view/helpers.rb | 2 + .../lib/action_view/helpers/csp_helper.rb | 24 ++++++ .../action_view/helpers/javascript_helper.rb | 11 +++ actionview/test/ujs/public/test/call-ajax.js | 3 +- actionview/test/ujs/server.rb | 26 +++++-- .../ujs/views/layouts/application.html.erb | 7 +- railties/lib/rails/application.rb | 3 +- .../lib/rails/application/configuration.rb | 75 ++++++++++--------- .../app/views/layouts/application.html.erb.tt | 1 + .../content_security_policy.rb.tt | 5 +- 16 files changed, 207 insertions(+), 52 deletions(-) create mode 100644 actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee create mode 100644 actionview/lib/action_view/helpers/csp_helper.rb diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md index cd419b68f7..98bf9c944b 100644 --- a/actionpack/CHANGELOG.md +++ b/actionpack/CHANGELOG.md @@ -1,5 +1,33 @@ ## Rails 6.0.0.alpha (Unreleased) ## +* Add support for automatic nonce generation for Rails UJS + + Because the UJS library creates a script tag to process responses it + normally requires the script-src attribute of the content security + policy to include 'unsafe-inline'. + + To work around this we generate a per-request nonce value that is + embedded in a meta tag in a similar fashion to how CSRF protection + embeds its token in a meta tag. The UJS library can then read the + nonce value and set it on the dynamically generated script tag to + enable it to execute without needing 'unsafe-inline' enabled. + + Nonce generation isn't 100% safe - if your script tag is including + user generated content in someway then it may be possible to exploit + an XSS vulnerability which can take advantage of the nonce. It is + however an improvement on a blanket permission for inline scripts. + + It is also possible to use the nonce within your own script tags by + using `nonce: true` to set the nonce value on the tag, e.g + + <%= javascript_tag nonce: true do %> + alert('Hello, World!'); + <% end %> + + Fixes #31689. + + *Andrew White* + * Rails 6 requires Ruby 2.4.1 or newer. *Jeremy Daer* diff --git a/actionpack/lib/action_controller/metal/content_security_policy.rb b/actionpack/lib/action_controller/metal/content_security_policy.rb index 48a7109bea..95f2f3242d 100644 --- a/actionpack/lib/action_controller/metal/content_security_policy.rb +++ b/actionpack/lib/action_controller/metal/content_security_policy.rb @@ -5,6 +5,14 @@ module ActionController #:nodoc: # TODO: Documentation extend ActiveSupport::Concern + include AbstractController::Helpers + include AbstractController::Callbacks + + included do + helper_method :content_security_policy? + helper_method :content_security_policy_nonce + end + module ClassMethods def content_security_policy(**options, &block) before_action(options) do @@ -22,5 +30,15 @@ module ActionController #:nodoc: end end end + + private + + def content_security_policy? + request.content_security_policy + end + + def content_security_policy_nonce + request.content_security_policy_nonce + end end end diff --git a/actionpack/lib/action_dispatch/http/content_security_policy.rb b/actionpack/lib/action_dispatch/http/content_security_policy.rb index ffac3b8d99..a3407c9698 100644 --- a/actionpack/lib/action_dispatch/http/content_security_policy.rb +++ b/actionpack/lib/action_dispatch/http/content_security_policy.rb @@ -21,6 +21,12 @@ module ActionDispatch #:nodoc: return response if policy_present?(headers) if policy = request.content_security_policy + if policy.directives["script-src"] + if nonce = request.content_security_policy_nonce + policy.directives["script-src"] << "'nonce-#{nonce}'" + end + end + headers[header_name(request)] = policy.build(request.controller_instance) end @@ -51,6 +57,8 @@ module ActionDispatch #:nodoc: module Request POLICY = "action_dispatch.content_security_policy".freeze POLICY_REPORT_ONLY = "action_dispatch.content_security_policy_report_only".freeze + NONCE_GENERATOR = "action_dispatch.content_security_policy_nonce_generator".freeze + NONCE = "action_dispatch.content_security_policy_nonce".freeze def content_security_policy get_header(POLICY) @@ -67,6 +75,30 @@ module ActionDispatch #:nodoc: def content_security_policy_report_only=(value) set_header(POLICY_REPORT_ONLY, value) end + + def content_security_policy_nonce_generator + get_header(NONCE_GENERATOR) + end + + def content_security_policy_nonce_generator=(generator) + set_header(NONCE_GENERATOR, generator) + end + + def content_security_policy_nonce + if content_security_policy_nonce_generator + if nonce = get_header(NONCE) + nonce + else + set_header(NONCE, generate_content_security_policy_nonce) + end + end + end + + private + + def generate_content_security_policy_nonce + content_security_policy_nonce_generator.call(self) + end end MAPPINGS = { diff --git a/actionpack/test/dispatch/content_security_policy_test.rb b/actionpack/test/dispatch/content_security_policy_test.rb index 5184e4f960..b88f90190a 100644 --- a/actionpack/test/dispatch/content_security_policy_test.rb +++ b/actionpack/test/dispatch/content_security_policy_test.rb @@ -253,6 +253,11 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest p.report_uri "/violations" end + content_security_policy only: :script_src do |p| + p.default_src false + p.script_src :self + end + content_security_policy_report_only only: :report_only def index @@ -271,6 +276,10 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest head :ok end + def script_src + head :ok + end + private def condition? params[:condition] == "true" @@ -284,6 +293,7 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest get "/inline", to: "policy#inline" get "/conditional", to: "policy#conditional" get "/report-only", to: "policy#report_only" + get "/script-src", to: "policy#script_src" end end @@ -298,6 +308,7 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest def call(env) env["action_dispatch.content_security_policy"] = POLICY + env["action_dispatch.content_security_policy_nonce_generator"] = proc { "iyhD0Yc0W+c=" } env["action_dispatch.content_security_policy_report_only"] = false env["action_dispatch.show_exceptions"] = false @@ -337,6 +348,11 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest assert_policy "default-src 'self'; report-uri /violations", report_only: true end + def test_adds_nonce_to_script_src_content_security_policy + get "/script-src" + assert_policy "script-src 'self' 'nonce-iyhD0Yc0W+c='" + end + private def env_config diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee index cc0e037428..2a8f5659e3 100644 --- a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee +++ b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee @@ -1,7 +1,8 @@ +#= require ./csp #= require ./csrf #= require ./event -{ CSRFProtection, fire } = Rails +{ cspNonce, CSRFProtection, fire } = Rails AcceptHeaders = '*': '*/*' @@ -65,6 +66,7 @@ processResponse = (response, type) -> try response = JSON.parse(response) else if type.match(/\b(?:java|ecma)script\b/) script = document.createElement('script') + script.nonce = cspNonce() script.text = response document.head.appendChild(script).parentNode.removeChild(script) else if type.match(/\b(xml|html|svg)\b/) diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee new file mode 100644 index 0000000000..8d2d6ce447 --- /dev/null +++ b/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee @@ -0,0 +1,4 @@ +# Content-Security-Policy nonce for inline scripts +cspNonce = Rails.cspNonce = -> + meta = document.querySelector('meta[name=csp-nonce]') + meta and meta.content diff --git a/actionview/lib/action_view/helpers.rb b/actionview/lib/action_view/helpers.rb index 46f20c4277..8cc8013718 100644 --- a/actionview/lib/action_view/helpers.rb +++ b/actionview/lib/action_view/helpers.rb @@ -13,6 +13,7 @@ module ActionView #:nodoc: autoload :CacheHelper autoload :CaptureHelper autoload :ControllerHelper + autoload :CspHelper autoload :CsrfHelper autoload :DateHelper autoload :DebugHelper @@ -46,6 +47,7 @@ module ActionView #:nodoc: include CacheHelper include CaptureHelper include ControllerHelper + include CspHelper include CsrfHelper include DateHelper include DebugHelper diff --git a/actionview/lib/action_view/helpers/csp_helper.rb b/actionview/lib/action_view/helpers/csp_helper.rb new file mode 100644 index 0000000000..e2e065c218 --- /dev/null +++ b/actionview/lib/action_view/helpers/csp_helper.rb @@ -0,0 +1,24 @@ +# frozen_string_literal: true + +module ActionView + # = Action View CSP Helper + module Helpers #:nodoc: + module CspHelper + # Returns a meta tag "csp-nonce" with the per-session nonce value + # for allowing inline ).html_safe + capture do + names.each do |name| + concat(javascript_include_tag(name)) + end + end end end @@ -56,7 +68,7 @@ class TestsController < ActionController::Base elsif params[:iframe] payload = JSON.generate(data).gsub("<", "<").gsub(">", ">") html = <<-HTML - diff --git a/actionview/test/ujs/views/layouts/application.html.erb b/actionview/test/ujs/views/layouts/application.html.erb index c787e77b84..8f6f6fc17f 100644 --- a/actionview/test/ujs/views/layouts/application.html.erb +++ b/actionview/test/ujs/views/layouts/application.html.erb @@ -2,9 +2,10 @@ <%= @title %> + <%= csp_meta_tag %> - - <%= script_tag "/rails-ujs.js" %> + <% end %> + <%= javascript_include_tag "/rails-ujs.js" %> diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb index a200a1005c..a9dee10981 100644 --- a/railties/lib/rails/application.rb +++ b/railties/lib/rails/application.rb @@ -268,7 +268,8 @@ module Rails "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest, "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations, "action_dispatch.content_security_policy" => config.content_security_policy, - "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only + "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only, + "action_dispatch.content_security_policy_nonce_generator" => config.content_security_policy_nonce_generator ) end end diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb index 1f765f302c..b42ffe50d8 100644 --- a/railties/lib/rails/application/configuration.rb +++ b/railties/lib/rails/application/configuration.rb @@ -17,48 +17,49 @@ module Rails :session_options, :time_zone, :reload_classes_only_on_change, :beginning_of_week, :filter_redirect, :x, :enable_dependency_loading, :read_encrypted_secrets, :log_level, :content_security_policy_report_only, - :require_master_key + :content_security_policy_nonce_generator, :require_master_key attr_reader :encoding, :api_only, :loaded_config_version def initialize(*) super - self.encoding = Encoding::UTF_8 - @allow_concurrency = nil - @consider_all_requests_local = false - @filter_parameters = [] - @filter_redirect = [] - @helpers_paths = [] - @public_file_server = ActiveSupport::OrderedOptions.new - @public_file_server.enabled = true - @public_file_server.index_name = "index" - @force_ssl = false - @ssl_options = {} - @session_store = nil - @time_zone = "UTC" - @beginning_of_week = :monday - @log_level = :debug - @generators = app_generators - @cache_store = [ :file_store, "#{root}/tmp/cache/" ] - @railties_order = [:all] - @relative_url_root = ENV["RAILS_RELATIVE_URL_ROOT"] - @reload_classes_only_on_change = true - @file_watcher = ActiveSupport::FileUpdateChecker - @exceptions_app = nil - @autoflush_log = true - @log_formatter = ActiveSupport::Logger::SimpleFormatter.new - @eager_load = nil - @secret_token = nil - @secret_key_base = nil - @api_only = false - @debug_exception_response_format = nil - @x = Custom.new - @enable_dependency_loading = false - @read_encrypted_secrets = false - @content_security_policy = nil - @content_security_policy_report_only = false - @require_master_key = false - @loaded_config_version = nil + self.encoding = Encoding::UTF_8 + @allow_concurrency = nil + @consider_all_requests_local = false + @filter_parameters = [] + @filter_redirect = [] + @helpers_paths = [] + @public_file_server = ActiveSupport::OrderedOptions.new + @public_file_server.enabled = true + @public_file_server.index_name = "index" + @force_ssl = false + @ssl_options = {} + @session_store = nil + @time_zone = "UTC" + @beginning_of_week = :monday + @log_level = :debug + @generators = app_generators + @cache_store = [ :file_store, "#{root}/tmp/cache/" ] + @railties_order = [:all] + @relative_url_root = ENV["RAILS_RELATIVE_URL_ROOT"] + @reload_classes_only_on_change = true + @file_watcher = ActiveSupport::FileUpdateChecker + @exceptions_app = nil + @autoflush_log = true + @log_formatter = ActiveSupport::Logger::SimpleFormatter.new + @eager_load = nil + @secret_token = nil + @secret_key_base = nil + @api_only = false + @debug_exception_response_format = nil + @x = Custom.new + @enable_dependency_loading = false + @read_encrypted_secrets = false + @content_security_policy = nil + @content_security_policy_report_only = false + @content_security_policy_nonce_generator = nil + @require_master_key = false + @loaded_config_version = nil end def load_defaults(target_version) diff --git a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt index 5460155b3e..ef715f1368 100644 --- a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt +++ b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt @@ -3,6 +3,7 @@ <%= camelized %> <%%= csrf_meta_tags %> + <%%= csp_meta_tag %> <%- if options[:skip_javascript] -%> <%%= stylesheet_link_tag 'application', media: 'all' %> diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt index edde7f42b8..38c658548d 100644 --- a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt +++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt @@ -10,12 +10,15 @@ # policy.img_src :self, :https, :data # policy.object_src :none # policy.script_src :self, :https -# policy.style_src :self, :https, :unsafe_inline +# policy.style_src :self, :https # # Specify URI for violation reports # # policy.report_uri "/csp-violation-report-endpoint" # end +# If you are using UJS then enable automatic nonce generation +# Rails.application.config.content_security_policy_nonce_generator = -> { SecureRandom.base64(16) } + # Report CSP violations to a specified URI # For further information see the following documentation: # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only