Extract class from CSP configuration/initialization (mastodon#26905)

app/lib/content_security_policy.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+class ContentSecurityPolicy
+  def base_host
+    Rails.configuration.x.web_domain
+  end
+
+  def assets_host
+    url_from_configured_asset_host || url_from_base_host
+  end
+
+  def media_host
+    cdn_host_value || assets_host
+  end
+
+  private
+
+  def url_from_configured_asset_host
+    Rails.configuration.action_controller.asset_host
+  end
+
+  def cdn_host_value
+    s3_alias_host || s3_cloudfront_host || azure_alias_host || s3_hostname_host
+  end
+
+  def url_from_base_host
+    host_to_url(base_host)
+  end
+
+  def host_to_url(host_string)
+    uri_from_configuration_and_string(host_string) if host_string.present?
+  end
+
+  def s3_alias_host
+    host_to_url ENV.fetch('S3_ALIAS_HOST', nil)
+  end
+
+  def s3_cloudfront_host
+    host_to_url ENV.fetch('S3_CLOUDFRONT_HOST', nil)
+  end
+
+  def azure_alias_host
+    host_to_url ENV.fetch('AZURE_ALIAS_HOST', nil)
+  end
+
+  def s3_hostname_host
+    host_to_url ENV.fetch('S3_HOSTNAME', nil)
+  end
+
+  def uri_from_configuration_and_string(host_string)
+    Addressable::URI.parse("#{host_protocol}://#{host_string}").tap do |uri|
+      uri.path += '/' unless uri.path.blank? || uri.path.end_with?('/')
+    end.to_s
+  end
+
+  def host_protocol
+    Rails.configuration.x.use_https ? 'https' : 'http'
+  end
+end

config/initializers/content_security_policy.rb

@@ -6,24 +6,11 @@
 # See the Securing Rails Applications Guide for more information:
 # https://guides.rubyonrails.org/security.html#content-security-policy-header
 
-def host_to_url(str)
-  return if str.blank?
+require_relative '../../app/lib/content_security_policy'
 
-  uri = Addressable::URI.parse("http#{Rails.configuration.x.use_https ? 's' : ''}://#{str}")
-  uri.path += '/' unless uri.path.blank? || uri.path.end_with?('/')
-  uri.to_s
-end
-
-base_host = Rails.configuration.x.web_domain
-
-assets_host   = Rails.configuration.action_controller.asset_host
-assets_host ||= host_to_url(base_host)
-
-media_host   = host_to_url(ENV['S3_ALIAS_HOST'])
-media_host ||= host_to_url(ENV['S3_CLOUDFRONT_HOST'])
-media_host ||= host_to_url(ENV['AZURE_ALIAS_HOST'])
-media_host ||= host_to_url(ENV['S3_HOSTNAME']) if ENV['S3_ENABLED'] == 'true'
-media_host ||= assets_host
+policy = ContentSecurityPolicy.new
+assets_host = policy.assets_host
+media_host = policy.media_host
 
 def sso_host
   return unless ENV['ONE_CLICK_SSO_LOGIN'] == 'true'

spec/lib/content_security_policy_spec.rb

@@ -0,0 +1,129 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ContentSecurityPolicy do
+  subject { described_class.new }
+
+  around do |example|
+    original_asset_host = Rails.configuration.action_controller.asset_host
+    original_web_domain = Rails.configuration.x.web_domain
+    original_use_https = Rails.configuration.x.use_https
+    example.run
+    Rails.configuration.action_controller.asset_host = original_asset_host
+    Rails.configuration.x.web_domain = original_web_domain
+    Rails.configuration.x.use_https = original_use_https
+  end
+
+  describe '#base_host' do
+    before { Rails.configuration.x.web_domain = 'host.example' }
+
+    it 'returns the configured value for the web domain' do
+      expect(subject.base_host).to eq 'host.example'
+    end
+  end
+
+  describe '#assets_host' do
+    context 'when asset_host is not configured' do
+      before { Rails.configuration.action_controller.asset_host = nil }
+
+      context 'with a configured web domain' do
+        before { Rails.configuration.x.web_domain = 'host.example' }
+
+        context 'when use_https is enabled' do
+          before { Rails.configuration.x.use_https = true }
+
+          it 'returns value from base host with https protocol' do
+            expect(subject.assets_host).to eq 'https://host.example'
+          end
+        end
+
+        context 'when use_https is disabled' do
+          before { Rails.configuration.x.use_https = false }
+
+          it 'returns value from base host with http protocol' do
+            expect(subject.assets_host).to eq 'http://host.example'
+          end
+        end
+      end
+    end
+
+    context 'when asset_host is configured' do
+      before do
+        Rails.configuration.action_controller.asset_host = 'https://assets.host.example'
+      end
+
+      it 'returns full value from configured host' do
+        expect(subject.assets_host).to eq 'https://assets.host.example'
+      end
+    end
+  end
+
+  describe '#media_host' do
+    context 'when there is no configured CDN' do
+      it 'defaults to using the assets_host value' do
+        expect(subject.media_host).to eq(subject.assets_host)
+      end
+    end
+
+    context 'when an S3 alias host is configured' do
+      around do |example|
+        ClimateControl.modify S3_ALIAS_HOST: 'asset-host.s3-alias.example' do
+          example.run
+        end
+      end
+
+      it 'uses the s3 alias host value' do
+        expect(subject.media_host).to eq 'https://asset-host.s3-alias.example'
+      end
+    end
+
+    context 'when an S3 alias host with a trailing path is configured' do
+      around do |example|
+        ClimateControl.modify S3_ALIAS_HOST: 'asset-host.s3-alias.example/pathname' do
+          example.run
+        end
+      end
+
+      it 'uses the s3 alias host value and preserves the path' do
+        expect(subject.media_host).to eq 'https://asset-host.s3-alias.example/pathname/'
+      end
+    end
+
+    context 'when an S3 cloudfront host is configured' do
+      around do |example|
+        ClimateControl.modify S3_CLOUDFRONT_HOST: 'asset-host.s3-cloudfront.example' do
+          example.run
+        end
+      end
+
+      it 'uses the s3 cloudfront host value' do
+        expect(subject.media_host).to eq 'https://asset-host.s3-cloudfront.example'
+      end
+    end
+
+    context 'when an azure alias host is configured' do
+      around do |example|
+        ClimateControl.modify AZURE_ALIAS_HOST: 'asset-host.azure-alias.example' do
+          example.run
+        end
+      end
+
+      it 'uses the azure alias host value' do
+        expect(subject.media_host).to eq 'https://asset-host.azure-alias.example'
+      end
+    end
+
+    context 'when s3_enabled is configured' do
+      around do |example|
+        ClimateControl.modify S3_ENABLED: 'true', S3_HOSTNAME: 'asset-host.s3.example' do
+          example.run
+        end
+      end
+
+      it 'uses the s3 hostname host value' do
+        expect(subject.media_host).to eq 'https://asset-host.s3.example'
+      end
+    end
+  end
+end