Merge pull request #382 from twitter/nonce-sniffing

unconditionally send nonces and unsafe-inline when working with nonces

Author: oreoshake

docs/upgrading-to-6-0.md

@@ -42,3 +42,9 @@ Prior to 6.0.0 SecureHeaders pre-built and cached the headers that corresponded
 ## Configuration the default configuration more than once will result in an Exception
 
 Prior to 6.0.0 you could conceivably, though unlikely, have `Configure#default` called more than once. Because configurations are dynamic, configuring more than once could result in unexpected behavior. So, as of 6.0.0 we raise `AlreadyConfiguredError` if the default configuration is setup more than once.
+
+## Nonce behavior and console warnings
+
+Since the first commit, reducing browser console messages was a goal. It led to overly complicated and error-prone UA sniffing. Nowadays, consoles warn on completely legitimate use of features meant to be backwards compatible. So the goal is impossible and the impact is negative, so eliminating code using sniffing is a goal.
+
+The first example: we will now send `'unsafe-inline'` along with nonce source expressions. This will generate warnings in some consoles but is 100% valid use and was a design goal of CSP in the early days. The concept of versioning CSP lost out and so we're left with backward compatibility as our only option.

lib/secure_headers/headers/content_security_policy.rb

@@ -213,11 +213,7 @@ def populate_nonces(directive, source_list)
     # unsafe-inline, this is more concise.
     def append_nonce(source_list, nonce)
       if nonce
-        if nonces_supported?
-          source_list << "'nonce-#{nonce}'"
-        else
-          source_list << UNSAFE_INLINE
-        end
+        source_list.push("'nonce-#{nonce}'", UNSAFE_INLINE)
       end
 
       source_list
@@ -257,10 +253,6 @@ def supported_directives
       end
     end
 
-    def nonces_supported?
-      @nonces_supported ||= self.class.nonces_supported?(@parsed_ua)
-    end
-
     def symbol_to_hyphen_case(sym)
       sym.to_s.tr("_", "-")
     end

lib/secure_headers/headers/policy_management.rb

@@ -5,7 +5,6 @@ def self.included(base)
       base.extend(ClassMethods)
     end
 
-    MODERN_BROWSERS = %w(Chrome Opera Firefox)
     DEFAULT_CONFIG = {
       default_src: %w(https:),
       img_src: %w(https: data: 'self'),
@@ -238,15 +237,6 @@ def validate_config!(config)
         end
       end
 
-      # Public: check if a user agent supports CSP nonces
-      #
-      # user_agent - a String or a UserAgent object
-      def nonces_supported?(user_agent)
-        user_agent = UserAgent.parse(user_agent) if user_agent.is_a?(String)
-        MODERN_BROWSERS.include?(user_agent.browser) ||
-          user_agent.browser == "Safari" && (user_agent.version || CSP::FALLBACK_VERSION) >= CSP::VERSION_10
-      end
-
       # Public: combine the values from two different configs.
       #
       # original - the main config

spec/lib/secure_headers/headers/content_security_policy_spec.rb

@@ -124,7 +124,7 @@ module SecureHeaders
 
       it "supports strict-dynamic" do
         csp = ContentSecurityPolicy.new({default_src: %w('self'), script_src: [ContentSecurityPolicy::STRICT_DYNAMIC], script_nonce: 123456}, USER_AGENTS[:chrome])
-        expect(csp.value).to eq("default-src 'self'; script-src 'strict-dynamic' 'nonce-123456'")
+        expect(csp.value).to eq("default-src 'self'; script-src 'strict-dynamic' 'nonce-123456' 'unsafe-inline'")
       end
 
       context "browser sniffing" do
@@ -143,44 +143,44 @@ module SecureHeaders
 
         it "does not filter any directives for Chrome" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:chrome])
-          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; block-all-mixed-content; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; plugin-types application/pdf; sandbox allow-forms; script-src script-src.com 'nonce-123456'; style-src style-src.com; upgrade-insecure-requests; worker-src worker-src.com; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; block-all-mixed-content; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; plugin-types application/pdf; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; upgrade-insecure-requests; worker-src worker-src.com; report-uri report-uri.com")
         end
 
         it "does not filter any directives for Opera" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:opera])
-          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; block-all-mixed-content; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; plugin-types application/pdf; sandbox allow-forms; script-src script-src.com 'nonce-123456'; style-src style-src.com; upgrade-insecure-requests; worker-src worker-src.com; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; block-all-mixed-content; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; plugin-types application/pdf; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; upgrade-insecure-requests; worker-src worker-src.com; report-uri report-uri.com")
         end
 
         it "filters blocked-all-mixed-content, child-src, and plugin-types for firefox" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:firefox])
-          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; frame-src child-src.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456'; style-src style-src.com; upgrade-insecure-requests; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; frame-src child-src.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; upgrade-insecure-requests; report-uri report-uri.com")
         end
 
         it "filters blocked-all-mixed-content, frame-src, and plugin-types for firefox 46 and higher" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:firefox46])
-          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456'; style-src style-src.com; upgrade-insecure-requests; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; upgrade-insecure-requests; report-uri report-uri.com")
         end
 
-        it "child-src value is copied to frame-src, adds 'unsafe-inline', filters base-uri, blocked-all-mixed-content, upgrade-insecure-requests, child-src, form-action, frame-ancestors, nonce sources, hash sources, and plugin-types for Edge" do
+        it "child-src value is copied to frame-src, adds 'unsafe-inline', filters base-uri, blocked-all-mixed-content, upgrade-insecure-requests, child-src, form-action, frame-ancestors, hash sources, and plugin-types for Edge" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:edge])
-          expect(policy.value).to eq("default-src default-src.com; connect-src connect-src.com; font-src font-src.com; frame-src child-src.com; img-src img-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'unsafe-inline'; style-src style-src.com; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; connect-src connect-src.com; font-src font-src.com; frame-src child-src.com; img-src img-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; report-uri report-uri.com")
         end
 
-        it "child-src value is copied to frame-src, adds 'unsafe-inline', filters base-uri, blocked-all-mixed-content, upgrade-insecure-requests, child-src, form-action, frame-ancestors, nonce sources, hash sources, and plugin-types for safari" do
+        it "child-src value is copied to frame-src, adds 'unsafe-inline', filters base-uri, blocked-all-mixed-content, upgrade-insecure-requests, child-src, form-action, frame-ancestors, hash sources, and plugin-types for safari" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:safari6])
-          expect(policy.value).to eq("default-src default-src.com; connect-src connect-src.com; font-src font-src.com; frame-src child-src.com; img-src img-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'unsafe-inline'; style-src style-src.com; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; connect-src connect-src.com; font-src font-src.com; frame-src child-src.com; img-src img-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; report-uri report-uri.com")
         end
 
-        it "adds 'unsafe-inline', filters  blocked-all-mixed-content, upgrade-insecure-requests, nonce sources, and hash sources for safari 10 and higher" do
+        it "adds 'unsafe-inline', filters  blocked-all-mixed-content, upgrade-insecure-requests, and hash sources for safari 10 and higher" do
           policy = ContentSecurityPolicy.new(complex_opts, USER_AGENTS[:safari10])
-          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; media-src media-src.com; object-src object-src.com; plugin-types application/pdf; sandbox allow-forms; script-src script-src.com 'nonce-123456'; style-src style-src.com; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; child-src child-src.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; img-src img-src.com; media-src media-src.com; object-src object-src.com; plugin-types application/pdf; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; report-uri report-uri.com")
         end
 
         it "falls back to standard Firefox defaults when the useragent version is not present" do
           ua = USER_AGENTS[:firefox].dup
           allow(ua).to receive(:version).and_return(nil)
           policy = ContentSecurityPolicy.new(complex_opts, ua)
-          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; frame-src child-src.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456'; style-src style-src.com; upgrade-insecure-requests; report-uri report-uri.com")
+          expect(policy.value).to eq("default-src default-src.com; base-uri base-uri.com; connect-src connect-src.com; font-src font-src.com; form-action form-action.com; frame-ancestors frame-ancestors.com; frame-src child-src.com; img-src img-src.com; manifest-src manifest-src.com; media-src media-src.com; object-src object-src.com; sandbox allow-forms; script-src script-src.com 'nonce-123456' 'unsafe-inline'; style-src style-src.com; upgrade-insecure-requests; report-uri report-uri.com")
         end
       end
     end

spec/lib/secure_headers_spec.rb

@@ -287,21 +287,6 @@ module SecureHeaders
           expect(hash[ContentSecurityPolicyConfig::HEADER_NAME]).to eq("default-src https:; img-src data:; script-src 'self'")
         end
 
-        it "does not append a nonce when the browser does not support it" do
-          Configuration.default do |config|
-            config.csp = {
-              default_src: %w('self'),
-              script_src: %w(mycdn.com 'unsafe-inline'),
-              style_src: %w('self')
-            }
-          end
-
-          safari_request = Rack::Request.new(request.env.merge("HTTP_USER_AGENT" => USER_AGENTS[:safari5]))
-          SecureHeaders.content_security_policy_script_nonce(safari_request)
-          hash = SecureHeaders.header_hash_for(safari_request)
-          expect(hash[ContentSecurityPolicyConfig::HEADER_NAME]).to eq("default-src 'self'; script-src mycdn.com 'unsafe-inline'; style-src 'self'")
-        end
-
         it "appends a nonce to the script-src when used" do
           Configuration.default do |config|
             config.csp = {
@@ -319,21 +304,7 @@ module SecureHeaders
           SecureHeaders.content_security_policy_script_nonce(chrome_request)
 
           hash = SecureHeaders.header_hash_for(chrome_request)
-          expect(hash["Content-Security-Policy"]).to eq("default-src 'self'; script-src mycdn.com 'nonce-#{nonce}'; style-src 'self'")
-        end
-
-        it "uses a nonce for safari 10+" do
-          Configuration.default do |config|
-            config.csp = {
-              default_src: %w('self'),
-              script_src: %w(mycdn.com)
-            }
-          end
-
-          safari_request = Rack::Request.new(request.env.merge("HTTP_USER_AGENT" => USER_AGENTS[:safari10]))
-          nonce = SecureHeaders.content_security_policy_script_nonce(safari_request)
-          hash = SecureHeaders.header_hash_for(safari_request)
-          expect(hash["Content-Security-Policy"]).to eq("default-src 'self'; script-src mycdn.com 'nonce-#{nonce}'")
+          expect(hash["Content-Security-Policy"]).to eq("default-src 'self'; script-src mycdn.com 'nonce-#{nonce}' 'unsafe-inline'; style-src 'self'")
         end
 
         it "does not support the deprecated `report_only: true` format" do