SecureHeaders as a rack middleware

README.md

@@ -415,6 +415,35 @@ def before_load
 end
 ```
 
+### Using in rack middleware
+
+The `SecureHeaders::header_hash` generates a hash of all header values, which is useful for merging with rack middleware values.
+
+```ruby
+class MySecureHeaders
+  include SecureHeaders
+  def initialize(app)
+  @app = app
+ end
+
+ def call(env)
+   status, headers, response = @app.call(env)
+   security_headers = if override?
+     SecureHeaders::header_hash(:csp => false) # uses global config, but overrides CSP config
+   else
+     SecureHeaders::header_hash # uses global config
+   end
+   [status, headers.merge(security_headers), [response.body]]
+ end
+end
+
+module Testapp
+  class Application < Rails::Application
+    config.middleware.use MySecureHeaders
+  end
+end
+```
+
 ## Similar libraries
 
 * Rack [rack-secure_headers](https://github.com/harmoni/rack-secure_headers)

lib/secure_headers.rb

@@ -1,7 +1,32 @@
+require "secure_headers/version"
+require "secure_headers/header"
+require "secure_headers/headers/public_key_pins"
+require "secure_headers/headers/content_security_policy"
+require "secure_headers/headers/x_frame_options"
+require "secure_headers/headers/strict_transport_security"
+require "secure_headers/headers/x_xss_protection"
+require "secure_headers/headers/x_content_type_options"
+require "secure_headers/headers/x_download_options"
+require "secure_headers/headers/x_permitted_cross_domain_policies"
+require "secure_headers/railtie"
+require "secure_headers/hash_helper"
+require "secure_headers/view_helper"
+
 module SecureHeaders
   SCRIPT_HASH_CONFIG_FILE = 'config/script_hashes.yml'
   HASHES_ENV_KEY = 'secure_headers.script_hashes'
 
+  ALL_HEADER_CLASSES = [
+    SecureHeaders::ContentSecurityPolicy,
+    SecureHeaders::StrictTransportSecurity,
+    SecureHeaders::PublicKeyPins,
+    SecureHeaders::XContentTypeOptions,
+    SecureHeaders::XDownloadOptions,
+    SecureHeaders::XFrameOptions,
+    SecureHeaders::XPermittedCrossDomainPolicies,
+    SecureHeaders::XXssProtection
+  ]
+
   module Configuration
     class << self
       attr_accessor :hsts, :x_frame_options, :x_content_type_options,
@@ -24,6 +49,27 @@ def append_features(base)
         include InstanceMethods
       end
     end
+
+    def header_hash(options = nil)
+      ALL_HEADER_CLASSES.inject({}) do |memo, klass|
+        config = if options.is_a?(Hash) && options[klass::Constants::CONFIG_KEY]
+          options[klass::Constants::CONFIG_KEY]
+        else
+          ::SecureHeaders::Configuration.send(klass::Constants::CONFIG_KEY)
+        end
+
+        unless klass == SecureHeaders::PublicKeyPins && !config.is_a?(Hash)
+          header = get_a_header(klass::Constants::CONFIG_KEY, klass, config)
+          memo[header.name] = header.value
+        end
+        memo
+      end
+    end
+
+    def get_a_header(name, klass, options)
+      return if options == false
+      klass.new(options)
+    end
   end
 
   module ClassMethods
@@ -161,13 +207,10 @@ def secure_header_options_for(type, options)
       options.nil? ? ::SecureHeaders::Configuration.send(type) : options
     end
 
-
     def set_a_header(name, klass, options=nil)
-      options = secure_header_options_for name, options
+      options = secure_header_options_for(name, options)
       return if options == false
-
-      header = klass.new(options)
-      set_header(header)
+      set_header(SecureHeaders::get_a_header(name, klass, options))
     end
 
     def set_header(name_or_header, value=nil)
@@ -180,18 +223,3 @@ def set_header(name_or_header, value=nil)
     end
   end
 end
-
-
-require "secure_headers/version"
-require "secure_headers/header"
-require "secure_headers/headers/public_key_pins"
-require "secure_headers/headers/content_security_policy"
-require "secure_headers/headers/x_frame_options"
-require "secure_headers/headers/strict_transport_security"
-require "secure_headers/headers/x_xss_protection"
-require "secure_headers/headers/x_content_type_options"
-require "secure_headers/headers/x_download_options"
-require "secure_headers/headers/x_permitted_cross_domain_policies"
-require "secure_headers/railtie"
-require "secure_headers/hash_helper"
-require "secure_headers/view_helper"

lib/secure_headers/headers/content_security_policy.rb

@@ -40,7 +40,9 @@ module Constants
       SOURCE_DIRECTIVES = DIRECTIVES + NON_DEFAULT_SOURCES
 
       ALL_DIRECTIVES = DIRECTIVES + NON_DEFAULT_SOURCES + OTHER
+      CONFIG_KEY = :csp
     end
+
     include Constants
 
     attr_reader :disable_fill_missing, :ssl_request

lib/secure_headers/headers/public_key_pins.rb

@@ -6,6 +6,7 @@ module Constants
       ENV_KEY = 'secure_headers.public_key_pins'
       HASH_ALGORITHMS = [:sha256]
       DIRECTIVES = [:max_age]
+      CONFIG_KEY = :hpkp
     end
     class << self
       def symbol_to_hyphen_case sym

lib/secure_headers/headers/strict_transport_security.rb

@@ -8,6 +8,7 @@ module Constants
       DEFAULT_VALUE = "max-age=" + HSTS_MAX_AGE
       VALID_STS_HEADER = /\Amax-age=\d+(; includeSubdomains)?(; preload)?\z/i
       MESSAGE = "The config value supplied for the HSTS header was invalid."
+      CONFIG_KEY = :hsts
     end
     include Constants
 

lib/secure_headers/headers/x_content_type_options.rb

@@ -5,6 +5,7 @@ class XContentTypeOptions < Header
     module Constants
       X_CONTENT_TYPE_OPTIONS_HEADER_NAME = "X-Content-Type-Options"
       DEFAULT_VALUE = "nosniff"
+      CONFIG_KEY = :x_content_type_options
     end
     include Constants
 
@@ -37,4 +38,4 @@ def validate_config
       end
     end
   end
-end
+end

lib/secure_headers/headers/x_download_options.rb

@@ -4,6 +4,7 @@ class XDownloadOptions < Header
     module Constants
       XDO_HEADER_NAME = "X-Download-Options"
       DEFAULT_VALUE = 'noopen'
+      CONFIG_KEY = :x_download_options
     end
     include Constants
 

lib/secure_headers/headers/x_frame_options.rb

@@ -5,6 +5,7 @@ module Constants
       XFO_HEADER_NAME = "X-Frame-Options"
       DEFAULT_VALUE = 'SAMEORIGIN'
       VALID_XFO_HEADER = /\A(SAMEORIGIN\z|DENY\z|ALLOW-FROM[:\s])/i
+      CONFIG_KEY = :x_frame_options
     end
     include Constants
 

lib/secure_headers/headers/x_permitted_cross_domain_policies.rb

@@ -5,6 +5,7 @@ module Constants
       XPCDP_HEADER_NAME = "X-Permitted-Cross-Domain-Policies"
       DEFAULT_VALUE = 'none'
       VALID_POLICIES = %w(all none master-only by-content-type by-ftp-filename)
+      CONFIG_KEY = :x_permitted_cross_domain_policies
     end
     include Constants
 

lib/secure_headers/headers/x_xss_protection.rb

@@ -5,6 +5,7 @@ module Constants
       X_XSS_PROTECTION_HEADER_NAME = 'X-XSS-Protection'
       DEFAULT_VALUE = "1"
       VALID_X_XSS_HEADER = /\A[01](; mode=block)?(; report=.*)?\z/i
+      CONFIG_KEY = :x_xss_protection
     end
     include Constants
 

spec/lib/secure_headers_spec.rb

@@ -159,6 +159,56 @@ def set_security_headers(subject)
     end
   end
 
+  describe "SecureHeaders#header_hash" do
+    def expect_default_values(hash)
+      expect(hash[XFO_HEADER_NAME]).to eq(SecureHeaders::XFrameOptions::Constants::DEFAULT_VALUE)
+      expect(hash[XDO_HEADER_NAME]).to eq(SecureHeaders::XDownloadOptions::Constants::DEFAULT_VALUE)
+      expect(hash[HSTS_HEADER_NAME]).to eq(SecureHeaders::StrictTransportSecurity::Constants::DEFAULT_VALUE)
+      expect(hash[X_XSS_PROTECTION_HEADER_NAME]).to eq(SecureHeaders::XXssProtection::Constants::DEFAULT_VALUE)
+      expect(hash[X_CONTENT_TYPE_OPTIONS_HEADER_NAME]).to eq(SecureHeaders::XContentTypeOptions::Constants::DEFAULT_VALUE)
+      expect(hash[XPCDP_HEADER_NAME]).to eq(SecureHeaders::XPermittedCrossDomainPolicies::Constants::DEFAULT_VALUE)
+    end
+
+    it "produces a hash of headers given a hash as config" do
+      hash = SecureHeaders::header_hash(:csp => {:default_src => 'none', :img_src => "data:", :disable_fill_missing => true})
+      expect(hash['Content-Security-Policy-Report-Only']).to eq("default-src 'none'; img-src data:;")
+      expect_default_values(hash)
+    end
+
+    it "produces a hash with a mix of config values, override values, and default values" do
+      ::SecureHeaders::Configuration.configure do |config|
+        config.hsts = { :max_age => '123456'}
+        config.hpkp = {
+          :enforce => true,
+          :max_age => 1000000,
+          :include_subdomains => true,
+          :report_uri => '//example.com/uri-directive',
+          :pins => [
+            {:sha256 => 'abc'},
+            {:sha256 => '123'}
+          ]
+        }
+      end
+
+      hash = SecureHeaders::header_hash(:csp => {:default_src => 'none', :img_src => "data:", :disable_fill_missing => true})
+      ::SecureHeaders::Configuration.configure do |config|
+        config.hsts = nil
+        config.hpkp = nil
+      end
+
+      expect(hash['Content-Security-Policy-Report-Only']).to eq("default-src 'none'; img-src data:;")
+      expect(hash[XFO_HEADER_NAME]).to eq(SecureHeaders::XFrameOptions::Constants::DEFAULT_VALUE)
+      expect(hash[HSTS_HEADER_NAME]).to eq("max-age=123456")
+      expect(hash[HPKP_HEADER_NAME]).to eq(%{max-age=1000000; pin-sha256="abc"; pin-sha256="123"; report-uri="//example.com/uri-directive"; includeSubDomains})
+    end
+
+    it "produces a hash of headers with default config" do
+      hash = SecureHeaders::header_hash
+      expect(hash['Content-Security-Policy-Report-Only']).to eq(SecureHeaders::ContentSecurityPolicy::Constants::DEFAULT_CSP_HEADER)
+      expect_default_values(hash)
+    end
+  end
+
   describe "#set_x_frame_options_header" do
     it "sets the X-Frame-Options header" do
       should_assign_header(XFO_HEADER_NAME, SecureHeaders::XFrameOptions::Constants::DEFAULT_VALUE)