Merge pull request #8112 from rails/encrypted_cookies

Encrypted cookies

actionpack/lib/action_controller/metal/http_authentication.rb

@@ -249,9 +249,9 @@ module ActionController
       end
 
       def secret_token(request)
-        secret = request.env["action_dispatch.secret_token"]
-        raise "You must set config.secret_token in your app's config" if secret.blank?
-        secret
+        key_generator  = request.env["action_dispatch.key_generator"]
+        http_auth_salt = request.env["action_dispatch.http_auth_salt"]
+        key_generator.generate_key(http_auth_salt)
       end
 
       # Uses an MD5 digest based on time to generate a value to be used only once.

actionpack/lib/action_controller/metal/request_forgery_protection.rb

@@ -121,11 +121,11 @@ module ActionController #:nodoc:
 
         class NullCookieJar < ActionDispatch::Cookies::CookieJar #:nodoc:
           def self.build(request)
-            secret = request.env[ActionDispatch::Cookies::TOKEN_KEY]
-            host   = request.host
-            secure = request.ssl?
+            key_generator = request.env[ActionDispatch::Cookies::GENERATOR_KEY]
+            host          = request.host
+            secure        = request.ssl?
 
-            new(secret, host, secure)
+            new(key_generator, host, secure)
           end
 
           def write(*)

actionpack/lib/action_dispatch.rb

@@ -81,10 +81,11 @@ module ActionDispatch
   end
 
   module Session
-    autoload :AbstractStore, 'action_dispatch/middleware/session/abstract_store'
-    autoload :CookieStore,   'action_dispatch/middleware/session/cookie_store'
-    autoload :MemCacheStore, 'action_dispatch/middleware/session/mem_cache_store'
-    autoload :CacheStore,    'action_dispatch/middleware/session/cache_store'
+    autoload :AbstractStore,        'action_dispatch/middleware/session/abstract_store'
+    autoload :CookieStore,          'action_dispatch/middleware/session/cookie_store'
+    autoload :EncryptedCookieStore, 'action_dispatch/middleware/session/cookie_store'
+    autoload :MemCacheStore,        'action_dispatch/middleware/session/mem_cache_store'
+    autoload :CacheStore,           'action_dispatch/middleware/session/cache_store'
   end
 
   mattr_accessor :test_app

actionpack/lib/action_dispatch/middleware/cookies.rb

@@ -1,5 +1,6 @@
 require 'active_support/core_ext/hash/keys'
 require 'active_support/core_ext/module/attribute_accessors'
+require 'active_support/message_verifier'
 
 module ActionDispatch
   class Request < Rack::Request
@@ -27,7 +28,7 @@ module ActionDispatch
   #   cookies[:login] = { value: "XJ-122", expires: 1.hour.from_now }
   #
   #   # Sets a signed cookie, which prevents users from tampering with its value.
-  #   # The cookie is signed by your app's <tt>config.secret_token</tt> value.
+  #   # The cookie is signed by your app's <tt>config.secret_key_base</tt> value.
   #   # It can be read using the signed method <tt>cookies.signed[:key]</tt>
   #   cookies.signed[:user_id] = current_user.id
   #
@@ -79,8 +80,12 @@ module ActionDispatch
   # * <tt>:httponly</tt> - Whether this cookie is accessible via scripting or
   #   only HTTP. Defaults to +false+.
   class Cookies
-    HTTP_HEADER = "Set-Cookie".freeze
-    TOKEN_KEY   = "action_dispatch.secret_token".freeze
+    HTTP_HEADER   = "Set-Cookie".freeze
+    GENERATOR_KEY = "action_dispatch.key_generator".freeze
+    SIGNED_COOKIE_SALT = "action_dispatch.signed_cookie_salt".freeze
+    ENCRYPTED_COOKIE_SALT = "action_dispatch.encrypted_cookie_salt".freeze
+    ENCRYPTED_SIGNED_COOKIE_SALT = "action_dispatch.encrypted_signed_cookie_salt".freeze
+
 
     # Raised when storing more than 4K of session data.
     CookieOverflow = Class.new StandardError
@@ -103,21 +108,27 @@ module ActionDispatch
       DOMAIN_REGEXP = /[^.]*\.([^.]*|..\...|...\...)$/
 
       def self.build(request)
-        secret = request.env[TOKEN_KEY]
+        env = request.env
+        key_generator = env[GENERATOR_KEY]
+        options = { signed_cookie_salt: env[SIGNED_COOKIE_SALT],
+                    encrypted_cookie_salt: env[ENCRYPTED_COOKIE_SALT],
+                    encrypted_signed_cookie_salt: env[ENCRYPTED_SIGNED_COOKIE_SALT] }
+
         host = request.host
         secure = request.ssl?
 
-        new(secret, host, secure).tap do |hash|
+        new(key_generator, host, secure, options).tap do |hash|
           hash.update(request.cookies)
         end
       end
 
-      def initialize(secret = nil, host = nil, secure = false)
-        @secret = secret
+      def initialize(key_generator, host = nil, secure = false, options = {})
+        @key_generator = key_generator
         @set_cookies = {}
         @delete_cookies = {}
         @host = host
         @secure = secure
+        @options = options
         @cookies = {}
       end
 
@@ -220,7 +231,7 @@ module ActionDispatch
       #   cookies.permanent.signed[:remember_me] = current_user.id
       #   # => Set-Cookie: remember_me=BAhU--848956038e692d7046deab32b7131856ab20e14e; path=/; expires=Sun, 16-Dec-2029 03:24:16 GMT
       def permanent
-        @permanent ||= PermanentCookieJar.new(self, @secret)
+        @permanent ||= PermanentCookieJar.new(self, @key_generator, @options)
       end
 
       # Returns a jar that'll automatically generate a signed representation of cookie value and verify it when reading from
@@ -228,7 +239,7 @@ module ActionDispatch
       # cookie was tampered with by the user (or a 3rd party), an ActiveSupport::MessageVerifier::InvalidSignature exception will
       # be raised.
       #
-      # This jar requires that you set a suitable secret for the verification on your app's +config.secret_token+.
+      # This jar requires that you set a suitable secret for the verification on your app's +config.secret_key_base+.
       #
       # Example:
       #
@@ -237,7 +248,23 @@ module ActionDispatch
       #
       #   cookies.signed[:discount] # => 45
       def signed
-        @signed ||= SignedCookieJar.new(self, @secret)
+        @signed ||= SignedCookieJar.new(self, @key_generator, @options)
+      end
+
+      # Returns a jar that'll automatically encrypt cookie values before sending them to the client and will decrypt them for read.
+      # If the cookie was tampered with by the user (or a 3rd party), an ActiveSupport::MessageVerifier::InvalidSignature exception
+      # will be raised.
+      #
+      # This jar requires that you set a suitable secret for the verification on your app's +config.secret_key_base+.
+      #
+      # Example:
+      #
+      #   cookies.encrypted[:discount] = 45
+      #   # => Set-Cookie: discount=ZS9ZZ1R4cG1pcUJ1bm80anhQang3dz09LS1mbDZDSU5scGdOT3ltQ2dTdlhSdWpRPT0%3D--ab54663c9f4e3bc340c790d6d2b71e92f5b60315; path=/
+      #
+      #   cookies.encrypted[:discount] # => 45
+      def encrypted
+        @encrypted ||= EncryptedCookieJar.new(self, @key_generator, @options)
       end
 
       def write(headers)
@@ -261,8 +288,10 @@ module ActionDispatch
     end
 
     class PermanentCookieJar < CookieJar #:nodoc:
-      def initialize(parent_jar, secret)
-        @parent_jar, @secret = parent_jar, secret
+      def initialize(parent_jar, key_generator, options = {})
+        @parent_jar = parent_jar
+        @key_generator = key_generator
+        @options = options
       end
 
       def []=(key, options)
@@ -283,11 +312,11 @@ module ActionDispatch
 
     class SignedCookieJar < CookieJar #:nodoc:
       MAX_COOKIE_SIZE = 4096 # Cookies can typically store 4096 bytes.
-      SECRET_MIN_LENGTH = 30 # Characters
 
-      def initialize(parent_jar, secret)
-        ensure_secret_secure(secret)
+      def initialize(parent_jar, key_generator, options = {})
         @parent_jar = parent_jar
+        @options = options
+        secret = key_generator.generate_key(@options[:signed_cookie_salt])
         @verifier   = ActiveSupport::MessageVerifier.new(secret)
       end
 
@@ -314,26 +343,41 @@ module ActionDispatch
       def method_missing(method, *arguments, &block)
         @parent_jar.send(method, *arguments, &block)
       end
+    end
 
-    protected
-
-      # To prevent users from using something insecure like "Password" we make sure that the
-      # secret they've provided is at least 30 characters in length.
-      def ensure_secret_secure(secret)
-        if secret.blank?
-          raise ArgumentError, "A secret is required to generate an " +
-            "integrity hash for cookie session data. Use " +
-            "config.secret_token = \"some secret phrase of at " +
-            "least #{SECRET_MIN_LENGTH} characters\"" +
-            "in config/initializers/secret_token.rb"
+    class EncryptedCookieJar < SignedCookieJar #:nodoc:
+      def initialize(parent_jar, key_generator, options = {})
+        if ActiveSupport::DummyKeyGenerator === key_generator
+          raise "Encrypted Cookies must be used in conjunction with config.secret_key_base." +
+                "Set config.secret_key_base in config/initializers/secret_token.rb"
         end
 
-        if secret.length < SECRET_MIN_LENGTH
-          raise ArgumentError, "Secret should be something secure, " +
-            "like \"#{SecureRandom.hex(16)}\". The value you " +
-            "provided, \"#{secret}\", is shorter than the minimum length " +
-            "of #{SECRET_MIN_LENGTH} characters"
+        @parent_jar = parent_jar
+        @options = options
+        secret = key_generator.generate_key(@options[:encrypted_cookie_salt])
+        sign_secret = key_generator.generate_key(@options[:encrypted_signed_cookie_salt])
+        @encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret)
+      end
+
+      def [](name)
+        if encrypted_message = @parent_jar[name]
+          @encryptor.decrypt_and_verify(encrypted_message)
         end
+      rescue ActiveSupport::MessageVerifier::InvalidSignature,
+             ActiveSupport::MessageVerifier::InvalidMessage
+        nil
+      end
+
+      def []=(key, options)
+        if options.is_a?(Hash)
+          options.symbolize_keys!
+        else
+          options = { :value => options }
+        end
+        options[:value] = @encryptor.encrypt_and_sign(options[:value])
+
+        raise CookieOverflow if options[:value].size > MAX_COOKIE_SIZE
+        @parent_jar[key] = options
       end
     end
 

actionpack/lib/action_dispatch/middleware/session/cookie_store.rb

@@ -57,8 +57,7 @@ module ActionDispatch
       def unpacked_cookie_data(env)
         env["action_dispatch.request.unsigned_session_cookie"] ||= begin
           stale_session_check! do
-            request = ActionDispatch::Request.new(env)
-            if data = request.cookie_jar.signed[@key]
+            if data = cookie_jar(env)[@key]
               data.stringify_keys!
             end
             data || {}
@@ -72,8 +71,26 @@ module ActionDispatch
       end
 
       def set_cookie(env, session_id, cookie)
+        cookie_jar(env)[@key] = cookie
+      end
+
+      def get_cookie
+        cookie_jar(env)[@key]
+      end
+
+      def cookie_jar(env)
         request = ActionDispatch::Request.new(env)
-        request.cookie_jar.signed[@key] = cookie
+        request.cookie_jar.signed
+      end
+    end
+
+    class EncryptedCookieStore < CookieStore
+
+      private
+
+      def cookie_jar(env)
+        request = ActionDispatch::Request.new(env)
+        request.cookie_jar.encrypted
       end
     end
   end

actionpack/lib/action_dispatch/railtie.rb

@@ -13,6 +13,10 @@ module ActionDispatch
     config.action_dispatch.rescue_responses = { }
     config.action_dispatch.default_charset = nil
     config.action_dispatch.rack_cache = false
+    config.action_dispatch.http_auth_salt = 'http authentication'
+    config.action_dispatch.signed_cookie_salt = 'signed cookie'
+    config.action_dispatch.encrypted_cookie_salt = 'encrypted cookie'
+    config.action_dispatch.encrypted_signed_cookie_salt = 'signed encrypted cookie'
 
     config.action_dispatch.default_headers = {
       'X-Frame-Options' => 'SAMEORIGIN',

actionpack/test/controller/flash_test.rb

@@ -1,4 +1,6 @@
 require 'abstract_unit'
+# FIXME remove DummyKeyGenerator and this require in 4.1
+require 'active_support/key_generator'
 
 class FlashTest < ActionController::TestCase
   class TestController < ActionController::Base
@@ -217,7 +219,7 @@ end
 
 class FlashIntegrationTest < ActionDispatch::IntegrationTest
   SessionKey = '_myapp_session'
-  SessionSecret = 'b3c631c314c0bbca50c1b2843150fe33'
+  Generator  =  ActiveSupport::DummyKeyGenerator.new('b3c631c314c0bbca50c1b2843150fe33')
 
   class TestController < ActionController::Base
     add_flash_types :bar
@@ -291,7 +293,7 @@ class FlashIntegrationTest < ActionDispatch::IntegrationTest
 
     # Overwrite get to send SessionSecret in env hash
     def get(path, parameters = nil, env = {})
-      env["action_dispatch.secret_token"] ||= SessionSecret
+      env["action_dispatch.key_generator"] ||= Generator
       super
     end
 

actionpack/test/controller/http_digest_authentication_test.rb

@@ -1,4 +1,6 @@
 require 'abstract_unit'
+# FIXME remove DummyKeyGenerator and this require in 4.1
+require 'active_support/key_generator'
 
 class HttpDigestAuthenticationTest < ActionController::TestCase
   class DummyDigestController < ActionController::Base
@@ -40,8 +42,8 @@ class HttpDigestAuthenticationTest < ActionController::TestCase
 
   setup do
     # Used as secret in generating nonce to prevent tampering of timestamp
-    @secret = "session_options_secret"
-    @request.env["action_dispatch.secret_token"] = @secret
+    @secret = "4fb45da9e4ab4ddeb7580d6a35503d99"
+    @request.env["action_dispatch.key_generator"] = ActiveSupport::DummyKeyGenerator.new(@secret)
   end
 
   teardown do

actionpack/test/dispatch/cookies_test.rb

@@ -1,4 +1,6 @@
 require 'abstract_unit'
+# FIXME remove DummyKeyGenerator and this require in 4.1
+require 'active_support/key_generator'
 
 class CookiesTest < ActionController::TestCase
   class TestController < ActionController::Base
@@ -65,6 +67,11 @@ class CookiesTest < ActionController::TestCase
       head :ok
     end
 
+    def set_encrypted_cookie
+      cookies.encrypted[:foo] = 'bar'
+      head :ok
+    end
+
     def raise_data_overflow
       cookies.signed[:foo] = 'bye!' * 1024
       head :ok
@@ -146,7 +153,10 @@ class CookiesTest < ActionController::TestCase
 
   def setup
     super
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
+    @request.env["action_dispatch.key_generator"] = ActiveSupport::KeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33")
+    @request.env["action_dispatch.signed_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
+    @request.env["action_dispatch.encrypted_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
+    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
     @request.host = "www.nextangle.com"
   end
 
@@ -296,6 +306,16 @@ class CookiesTest < ActionController::TestCase
     assert_equal 45, @controller.send(:cookies).signed[:user_id]
   end
 
+  def test_encrypted_cookie
+    get :set_encrypted_cookie
+    cookies = @controller.send :cookies
+    assert_not_equal 'bar', cookies[:foo]
+    assert_raises TypeError do
+      cookies.signed[:foo]
+    end
+    assert_equal 'bar', cookies.encrypted[:foo]
+  end
+
   def test_accessing_nonexistant_signed_cookie_should_not_raise_an_invalid_signature
     get :set_signed_cookie
     assert_nil @controller.send(:cookies).signed[:non_existant_attribute]
@@ -329,29 +349,29 @@ class CookiesTest < ActionController::TestCase
 
   def test_raises_argument_error_if_missing_secret
     assert_raise(ArgumentError, nil.inspect) {
-      @request.env["action_dispatch.secret_token"] = nil
+      @request.env["action_dispatch.key_generator"] = ActiveSupport::DummyKeyGenerator.new(nil)
       get :set_signed_cookie
     }
 
     assert_raise(ArgumentError, ''.inspect) {
-      @request.env["action_dispatch.secret_token"] = ""
+      @request.env["action_dispatch.key_generator"] = ActiveSupport::DummyKeyGenerator.new("")
       get :set_signed_cookie
     }
   end
 
   def test_raises_argument_error_if_secret_is_probably_insecure
     assert_raise(ArgumentError, "password".inspect) {
-      @request.env["action_dispatch.secret_token"] = "password"
+      @request.env["action_dispatch.key_generator"] = ActiveSupport::DummyKeyGenerator.new("password")
       get :set_signed_cookie
     }
 
     assert_raise(ArgumentError, "secret".inspect) {
-      @request.env["action_dispatch.secret_token"] = "secret"
+      @request.env["action_dispatch.key_generator"] = ActiveSupport::DummyKeyGenerator.new("secret")
       get :set_signed_cookie
     }
 
     assert_raise(ArgumentError, "12345678901234567890123456789".inspect) {
-      @request.env["action_dispatch.secret_token"] = "12345678901234567890123456789"
+      @request.env["action_dispatch.key_generator"] = ActiveSupport::DummyKeyGenerator.new("12345678901234567890123456789")
       get :set_signed_cookie
     }
   end

actionpack/test/dispatch/session/cookie_store_test.rb

@@ -1,9 +1,12 @@
 require 'abstract_unit'
 require 'stringio'
+# FIXME remove DummyKeyGenerator and this require in 4.1
+require 'active_support/key_generator'
 
 class CookieStoreTest < ActionDispatch::IntegrationTest
   SessionKey = '_myapp_session'
   SessionSecret = 'b3c631c314c0bbca50c1b2843150fe33'
+  Generator = ActiveSupport::DummyKeyGenerator.new(SessionSecret)
 
   Verifier = ActiveSupport::MessageVerifier.new(SessionSecret, :digest => 'SHA1')
   SignedBar = Verifier.generate(:foo => "bar", :session_id => SecureRandom.hex(16))
@@ -330,7 +333,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
     # Overwrite get to send SessionSecret in env hash
     def get(path, parameters = nil, env = {})
-      env["action_dispatch.secret_token"] ||= SessionSecret
+      env["action_dispatch.key_generator"] ||= Generator
       super
     end
 

activesupport/lib/active_support/key_generator.rb

@@ -1,3 +1,4 @@
+require 'mutex_m'
 require 'openssl'
 
 module ActiveSupport
@@ -20,4 +21,51 @@ module ActiveSupport
       OpenSSL::PKCS5.pbkdf2_hmac_sha1(@secret, salt, @iterations, key_size)
     end
   end
+
+  class CachingKeyGenerator
+    def initialize(key_generator)
+      @key_generator = key_generator
+      @cache_keys = {}.extend(Mutex_m)
+    end
+
+    def generate_key(salt, key_size=64)
+      @cache_keys.synchronize do
+        @cache_keys["#{salt}#{key_size}"] ||= @key_generator.generate_key(salt, key_size)
+      end
+    end
+  end
+
+  class DummyKeyGenerator
+    SECRET_MIN_LENGTH = 30 # Characters
+
+    def initialize(secret)
+      ensure_secret_secure(secret)
+      @secret = secret
+    end
+
+    def generate_key(salt)
+      @secret
+    end
+
+    private
+
+    # To prevent users from using something insecure like "Password" we make sure that the
+    # secret they've provided is at least 30 characters in length.
+    def ensure_secret_secure(secret)
+      if secret.blank?
+        raise ArgumentError, "A secret is required to generate an " +
+          "integrity hash for cookie session data. Use " +
+          "config.secret_key_base = \"some secret phrase of at " +
+          "least #{SECRET_MIN_LENGTH} characters\"" +
+          "in config/initializers/secret_token.rb"
+      end
+
+      if secret.length < SECRET_MIN_LENGTH
+        raise ArgumentError, "Secret should be something secure, " +
+          "like \"#{SecureRandom.hex(16)}\". The value you " +
+          "provided, \"#{secret}\", is shorter than the minimum length " +
+          "of #{SECRET_MIN_LENGTH} characters"
+      end
+    end
+  end
 end

activesupport/lib/active_support/message_encryptor.rb

@@ -39,10 +39,13 @@ module ActiveSupport
     # * <tt>:cipher</tt>     - Cipher to use. Can be any cipher returned by
     #   <tt>OpenSSL::Cipher.ciphers</tt>. Default is 'aes-256-cbc'.
     # * <tt>:serializer</tt> - Object serializer to use. Default is +Marshal+.
-    def initialize(secret, options = {})
+    def initialize(secret, *signature_key_or_options)
+      options = signature_key_or_options.extract_options!
+      sign_secret = signature_key_or_options.first
       @secret = secret
+      @sign_secret = sign_secret
       @cipher = options[:cipher] || 'aes-256-cbc'
-      @verifier = MessageVerifier.new(@secret, :serializer => NullSerializer)
+      @verifier = MessageVerifier.new(@sign_secret || @secret, :serializer => NullSerializer)
       @serializer = options[:serializer] || Marshal
     end
 

activesupport/test/message_encryptor_test.rb

@@ -56,7 +56,7 @@ class MessageEncryptorTest < ActiveSupport::TestCase
   end
 
   def test_alternative_serialization_method
-    encryptor = ActiveSupport::MessageEncryptor.new(SecureRandom.hex(64), :serializer => JSONSerializer.new)
+    encryptor = ActiveSupport::MessageEncryptor.new(SecureRandom.hex(64), SecureRandom.hex(64), :serializer => JSONSerializer.new)
     message = encryptor.encrypt_and_sign({ :foo => 123, 'bar' => Time.utc(2010) })
     assert_equal encryptor.decrypt_and_verify(message), { "foo" => 123, "bar" => "2010-01-01T00:00:00Z" }
   end

guides/code/getting_started/config/initializers/secret_token.rb

@@ -6,4 +6,4 @@
 # no regular words or you'll be exposed to dictionary attacks.
 # Make sure your secret key is kept private
 # if you're sharing your code publicly.
-Blog::Application.config.secret_token = '685a9bf865b728c6549a191c90851c1b5ec41ecb60b9e94ad79dd3f824749798aa7b5e94431901960bee57809db0947b481570f7f13376b7ca190fa28099c459'
+Blog::Application.config.secret_key_base = '685a9bf865b728c6549a191c90851c1b5ec41ecb60b9e94ad79dd3f824749798aa7b5e94431901960bee57809db0947b481570f7f13376b7ca190fa28099c459'

guides/source/action_controller_overview.md

@@ -219,7 +219,7 @@ Rails sets up (for the CookieStore) a secret key used for signing the session da
 # If you change this key, all old signed cookies will become invalid!
 # Make sure the secret is at least 30 characters and all random,
 # no regular words or you'll be exposed to dictionary attacks.
-YourApp::Application.config.secret_token = '49d3f3de9ed86c74b94ad6bd0...'
+YourApp::Application.config.secret_key_base = '49d3f3de9ed86c74b94ad6bd0...'
 ```
 
 NOTE: Changing the secret when using the `CookieStore` will invalidate all existing sessions.

guides/source/configuring.md

@@ -113,7 +113,7 @@ These configuration methods are to be called on a `Rails::Railtie` object, such
 
 * `config.reload_classes_only_on_change` enables or disables reloading of classes only when tracked files change. By default tracks everything on autoload paths and is set to true. If `config.cache_classes` is true, this option is ignored.
 
-* `config.secret_token` used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get `config.secret_token` initialized to a random key in `config/initializers/secret_token.rb`.
+* `config.secret_key_base` used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get `config.secret_key_base` initialized to a random key in `config/initializers/secret_token.rb`.
 
 * `config.serve_static_assets` configures Rails itself to serve static assets. Defaults to true, but in the production environment is turned off as the server software (e.g. Nginx or Apache) used to run the application should serve static assets instead. Unlike the default setting set this to true when running (absolutely not recommended!) or testing your app in production mode using WEBrick. Otherwise you won´t be able use page caching and requests for files that exist regularly under the public directory will anyway hit your Rails app.
 

railties/lib/rails/application.rb

@@ -1,5 +1,7 @@
 require 'fileutils'
 require 'active_support/queueing'
+# FIXME remove DummyKeyGenerator and this require in 4.1
+require 'active_support/key_generator'
 require 'rails/engine'
 
 module Rails
@@ -106,32 +108,57 @@ module Rails
     def key_generator
       # number of iterations selected based on consultation with the google security
       # team. Details at https://github.com/rails/rails/pull/6952#issuecomment-7661220
-      @key_generator ||= ActiveSupport::KeyGenerator.new(config.secret_token, iterations: 1000)
+      @caching_key_generator ||= begin
+        if config.secret_key_base
+          key_generator = ActiveSupport::KeyGenerator.new(config.secret_key_base, iterations: 1000)
+          ActiveSupport::CachingKeyGenerator.new(key_generator)
+        else
+          ActiveSupport::DummyKeyGenerator.new(config.secret_token)
+        end
+      end
     end
 
     # Stores some of the Rails initial environment parameters which
     # will be used by middlewares and engines to configure themselves.
     # Currently stores:
     #
-    #   * "action_dispatch.parameter_filter"         => config.filter_parameters,
-    #   * "action_dispatch.secret_token"             => config.secret_token,
-    #   * "action_dispatch.show_exceptions"          => config.action_dispatch.show_exceptions,
-    #   * "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local,
-    #   * "action_dispatch.logger"                   => Rails.logger,
-    #   * "action_dispatch.backtrace_cleaner"        => Rails.backtrace_cleaner
+    #   * "action_dispatch.parameter_filter"             => config.filter_parameters
+    #   * "action_dispatch.show_exceptions"              => config.action_dispatch.show_exceptions
+    #   * "action_dispatch.show_detailed_exceptions"     => config.consider_all_requests_local
+    #   * "action_dispatch.logger"                       => Rails.logger
+    #   * "action_dispatch.backtrace_cleaner"            => Rails.backtrace_cleaner
+    #   * "action_dispatch.key_generator"                => key_generator
+    #   * "action_dispatch.http_auth_salt"               => config.action_dispatch.http_auth_salt
+    #   * "action_dispatch.signed_cookie_salt"           => config.action_dispatch.signed_cookie_salt
+    #   * "action_dispatch.encrypted_cookie_salt"        => config.action_dispatch.encrypted_cookie_salt
+    #   * "action_dispatch.encrypted_signed_cookie_salt" => config.action_dispatch.encrypted_signed_cookie_salt
     #
     # These parameters will be used by middlewares and engines to configure themselves
     #
     def env_config
-      @env_config ||= super.merge({
-        "action_dispatch.parameter_filter" => config.filter_parameters,
-        "action_dispatch.secret_token" => config.secret_token,
-        "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions,
-        "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local,
-        "action_dispatch.logger" => Rails.logger,
-        "action_dispatch.backtrace_cleaner" => Rails.backtrace_cleaner,
-        "action_dispatch.key_generator" => key_generator
-      })
+      @env_config ||= begin
+        if config.secret_key_base.nil?
+          ActiveSupport::Deprecation.warn "You didn't set config.secret_key_base. " +
+            "This should be used instead of the old deprecated config.secret_token. " +
+            "Set config.secret_key_base instead of config.secret_token in config/initializers/secret_token.rb"
+          if config.secret_token.blank?
+            raise "You must set config.secret_key_base in your app's config"
+          end
+        end
+
+        super.merge({
+          "action_dispatch.parameter_filter" => config.filter_parameters,
+          "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions,
+          "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local,
+          "action_dispatch.logger" => Rails.logger,
+          "action_dispatch.backtrace_cleaner" => Rails.backtrace_cleaner,
+          "action_dispatch.key_generator" => key_generator,
+          "action_dispatch.http_auth_salt" => config.action_dispatch.http_auth_salt,
+          "action_dispatch.signed_cookie_salt" => config.action_dispatch.signed_cookie_salt,
+          "action_dispatch.encrypted_cookie_salt" => config.action_dispatch.encrypted_cookie_salt,
+          "action_dispatch.encrypted_signed_cookie_salt" => config.action_dispatch.encrypted_signed_cookie_salt
+        })
+      end
     end
 
     ## Rails internal API

railties/lib/rails/application/configuration.rb

@@ -10,7 +10,7 @@ module Rails
                     :cache_classes, :cache_store, :consider_all_requests_local, :console,
                     :eager_load, :exceptions_app, :file_watcher, :filter_parameters,
                     :force_ssl, :helpers_paths, :logger, :log_formatter, :log_tags,
-                    :railties_order, :relative_url_root, :secret_token,
+                    :railties_order, :relative_url_root, :secret_key_base, :secret_token,
                     :serve_static_assets, :ssl_options, :static_cache_control, :session_options,
                     :time_zone, :reload_classes_only_on_change,
                     :queue, :queue_consumer, :beginning_of_week
@@ -46,6 +46,8 @@ module Rails
         @queue                         = ActiveSupport::SynchronousQueue.new
         @queue_consumer                = nil
         @eager_load                    = nil
+        @secret_token                  = nil
+        @secret_key_base               = nil
 
         @assets = ActiveSupport::OrderedOptions.new
         @assets.enabled                  = false

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

@@ -7,6 +7,6 @@
 # no regular words or you'll be exposed to dictionary attacks.
 # You can use `rake secret` to generate a secure secret key.
 
-# Make sure your secret_token is kept private
+# Make sure your secret_key_base is kept private
 # if you're sharing your code publicly.
-<%= app_const %>.config.secret_token = '<%= app_secret %>'
+<%= app_const %>.config.secret_key_base = '<%= app_secret %>'

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

@@ -1,3 +1,3 @@
 # Be sure to restart your server when you modify this file.
 
-<%= app_const %>.config.session_store :cookie_store, key: <%= "'_#{app_name}_session'" %>
+<%= app_const %>.config.session_store :encrypted_cookie_store, key: <%= "'_#{app_name}_session'" %>

railties/test/abstract_unit.rb

@@ -14,5 +14,6 @@ require 'rails/all'
 module TestApp
   class Application < Rails::Application
     config.root = File.dirname(__FILE__)
+    config.secret_key_base = 'b3c631c314c0bbca50c1b2843150fe33'
   end
 end

railties/test/application/configuration_test.rb

@@ -225,21 +225,24 @@ module ApplicationTests
       assert_equal Pathname.new(app_path).join("somewhere"), Rails.public_path
     end
 
-    test "config.secret_token is sent in env" do
+    test "Use key_generator when secret_key_base is set" do
       make_basic_app do |app|
-        app.config.secret_token = 'b3c631c314c0bbca50c1b2843150fe33'
+        app.config.secret_key_base = 'b3c631c314c0bbca50c1b2843150fe33'
         app.config.session_store :disabled
       end
 
       class ::OmgController < ActionController::Base
         def index
           cookies.signed[:some_key] = "some_value"
-          render text: env["action_dispatch.secret_token"]
+          render text: cookies[:some_key]
         end
       end
 
       get "/"
-      assert_equal 'b3c631c314c0bbca50c1b2843150fe33', last_response.body
+
+      secret = app.key_generator.generate_key('signed cookie')
+      verifier = ActiveSupport::MessageVerifier.new(secret)
+      assert_equal 'some_value', verifier.verify(last_response.body)
     end
 
     test "protect from forgery is the default in a new app" do
@@ -568,7 +571,6 @@ module ApplicationTests
 
       assert_respond_to app, :env_config
       assert_equal      app.env_config['action_dispatch.parameter_filter'],  app.config.filter_parameters
-      assert_equal      app.env_config['action_dispatch.secret_token'],      app.config.secret_token
       assert_equal      app.env_config['action_dispatch.show_exceptions'],   app.config.action_dispatch.show_exceptions
       assert_equal      app.env_config['action_dispatch.logger'],            Rails.logger
       assert_equal      app.env_config['action_dispatch.backtrace_cleaner'], Rails.backtrace_cleaner

railties/test/application/middleware/remote_ip_test.rb

@@ -1,4 +1,6 @@
 require 'isolation/abstract_unit'
+# FIXME remove DummyKeyGenerator and this require in 4.1
+require 'active_support/key_generator'
 
 module ApplicationTests
   class RemoteIpTest < ActiveSupport::TestCase
@@ -8,7 +10,7 @@ module ApplicationTests
       remote_ip = nil
       env = Rack::MockRequest.env_for("/").merge(env).merge!(
         'action_dispatch.show_exceptions' => false,
-        'action_dispatch.secret_token' => 'b3c631c314c0bbca50c1b2843150fe33'
+        'action_dispatch.key_generator'   => ActiveSupport::DummyKeyGenerator.new('b3c631c314c0bbca50c1b2843150fe33')
       )
 
       endpoint = Proc.new do |e|

railties/test/application/middleware/session_test.rb

@@ -128,5 +128,56 @@ module ApplicationTests
       get '/foo/read_cookie'   # Cookie shouldn't be changed
       assert_equal '"1"', last_response.body
     end
+
+    test "session using encrypted cookie store" do
+      app_file 'config/routes.rb', <<-RUBY
+        AppTemplate::Application.routes.draw do
+          get ':controller(/:action)'
+        end
+      RUBY
+
+      controller :foo, <<-RUBY
+        class FooController < ActionController::Base
+          def write_session
+            session[:foo] = 1
+            render nothing: true
+          end
+
+          def read_session
+            render text: session[:foo]
+          end
+
+          def read_encrypted_cookie
+            render text: cookies.encrypted[:_myapp_session]['foo']
+          end
+
+          def read_raw_cookie
+            render text: cookies[:_myapp_session]
+          end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        config.session_store :encrypted_cookie_store, key: '_myapp_session'
+        config.action_dispatch.derive_signed_cookie_key = true
+      RUBY
+
+      require "#{app_path}/config/environment"
+
+      get '/foo/write_session'
+      get '/foo/write_session'
+      get '/foo/read_session'
+      assert_equal '1', last_response.body
+
+      get '/foo/read_encrypted_cookie'
+      assert_equal '1', last_response.body
+
+      secret = app.key_generator.generate_key('encrypted cookie')
+      sign_secret = app.key_generator.generate_key('signed encrypted cookie')
+      encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret)
+
+      get '/foo/read_raw_cookie'
+      assert_equal 1, encryptor.decrypt_and_verify(last_response.body)['foo']
+    end
   end
 end

railties/test/application/url_generation_test.rb

@@ -14,7 +14,7 @@ module ApplicationTests
       require "action_controller/railtie"
 
       class MyApp < Rails::Application
-        config.secret_token = "3b7cd727ee24e8444053437c36cc66c4"
+        config.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
         config.session_store :cookie_store, key: "_myapp_session"
         config.active_support.deprecation = :log
         config.eager_load = false

railties/test/generators/app_generator_test.rb

@@ -341,7 +341,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
   def test_new_hash_style
     run_generator [destination_root]
     assert_file "config/initializers/session_store.rb" do |file|
-      assert_match(/config.session_store :cookie_store, key: '_.+_session'/, file)
+      assert_match(/config.session_store :encrypted_cookie_store, key: '_.+_session'/, file)
     end
   end
 

railties/test/isolation/abstract_unit.rb

@@ -119,7 +119,7 @@ module TestHelpers
 
       add_to_config <<-RUBY
         config.eager_load = false
-        config.secret_token = "3b7cd727ee24e8444053437c36cc66c4"
+        config.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
         config.session_store :cookie_store, key: "_myapp_session"
         config.active_support.deprecation = :log
         config.action_controller.allow_forgery_protection = false
@@ -138,7 +138,7 @@ module TestHelpers
 
       app = Class.new(Rails::Application)
       app.config.eager_load = false
-      app.config.secret_token = "3b7cd727ee24e8444053437c36cc66c4"
+      app.config.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
       app.config.session_store :cookie_store, key: "_myapp_session"
       app.config.active_support.deprecation = :log