Suggest a CSP that's compatible with Turbo + import map (rails#43227)

* Suggest a CSP that's compatible with Turbo + import map

Need to have session-based nonces for that.

* Update railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt

Co-authored-by: Ryuta Kamizono <[email protected]>

* Update content_security_policy.rb.tt

Co-authored-by: Ryuta Kamizono <[email protected]>

Author: David Heinemeier Hansson

railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt

@@ -4,24 +4,23 @@
 # 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|
-#   policy.default_src :self, :https
-#   policy.font_src    :self, :https, :data
-#   policy.img_src     :self, :https, :data
-#   policy.object_src  :none
-#   policy.script_src  :self, :https
-#   policy.style_src   :self, :https
-#   # Specify URI for violation reports
-#   # policy.report_uri "/csp-violation-report-endpoint"
+# Rails.application.configure do
+#   config.content_security_policy do |policy|
+#     policy.default_src :self, :https
+#     policy.font_src    :self, :https, :data
+#     policy.img_src     :self, :https, :data
+#     policy.object_src  :none
+#     policy.script_src  :self, :https
+#     policy.style_src   :self, :https
+#     # Specify URI for violation reports
+#     # policy.report_uri "/csp-violation-report-endpoint"
+#   end
+#
+#   # Generate session nonces for permitted importmap and inline scripts
+#   config.content_security_policy_nonce_generator = ->(request) { request.session.id.to_s }
+#   config.content_security_policy_nonce_directives = %w(script-src)
+#
+#   # Report CSP violations to a specified URI. See:
+#   # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only
+#   # config.content_security_policy_report_only = true
 # end
-
-# If you are using UJS then enable automatic nonce generation
-# Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
-
-# Set the nonce only to specific directives
-# 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:
-# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only
-# Rails.application.config.content_security_policy_report_only = true