Follow up of #25602

Since keys are truncated, ruby 2.4 doesn't accept keys greater than their lenghts.
keys of same value but different lenght and greater than key size of cipher, produce the same results
as reproduced at https://gist.github.com/rhenium/b81355fe816dcfae459cc5eadfc4f6f9
Since our default cipher is 'aes-256-cbc', key length for which is 32 bytes, limit the length of key being passed to Encryptor to 32 bytes.
This continues to support backwards compat with any existing signed data, already encrupted and signed with 32+ byte keys.
Also fixes the passing of this value in multiple tests.

3 files changed, 41 insertions, 15 deletions

diff --git a/actionpack/lib/action_dispatch/middleware/cookies.rb b/actionpack/lib/action_dispatch/middleware/cookies.rb
index ff83c4beca..8d7884b3b5 100644
--- a/actionpack/lib/action_dispatch/middleware/cookies.rb
+++ b/actionpack/lib/action_dispatch/middleware/cookies.rb
@@ -567,17 +567,19 @@ module ActionDispatch
 
     class EncryptedCookieJar < AbstractCookieJar # :nodoc:
       include SerializedCookieJars
+      DEFAULT_CIPHER = 'aes-256-cbc'
 
-      def initialize(parent_jar)
-        super
+      def initialize(parent_jar, cipher: DEFAULT_CIPHER)
+        super(parent_jar)
 
         if ActiveSupport::LegacyKeyGenerator === key_generator
           raise "You didn't set secrets.secret_key_base, which is required for this cookie jar. " +
             "Read the upgrade documentation to learn more about this new config option."
         end
 
-        secret = key_generator.generate_key(request.encrypted_cookie_salt || "")
-        sign_secret = key_generator.generate_key(request.encrypted_signed_cookie_salt || "")
+        key_len = OpenSSL::Cipher.new(cipher).key_len
+        secret = key_generator.generate_key(request.encrypted_cookie_salt || '')[0, key_len]
+        sign_secret = key_generator.generate_key(request.encrypted_signed_cookie_salt || '')
         @encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
       end
 
diff --git a/actionpack/test/dispatch/cookies_test.rb b/actionpack/test/dispatch/cookies_test.rb
index 4d3d83f45a..2bee6c75bb 100644
--- a/actionpack/test/dispatch/cookies_test.rb
+++ b/actionpack/test/dispatch/cookies_test.rb
@@ -603,7 +603,7 @@ class CookiesTest < ActionController::TestCase
     secret = key_generator.generate_key(encrypted_cookie_salt)
     sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
 
-    marshal_value = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: Marshal).encrypt_and_sign("bar")
+    marshal_value = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret, serializer: Marshal).encrypt_and_sign("bar")
     @request.headers["Cookie"] = "foo=#{marshal_value}"
 
     get :get_encrypted_cookie
@@ -612,7 +612,7 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: JSON)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret, serializer: JSON)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
@@ -624,7 +624,7 @@ class CookiesTest < ActionController::TestCase
     encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
     secret = key_generator.generate_key(encrypted_cookie_salt)
     sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
-    json_value = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: JSON).encrypt_and_sign("bar")
+    json_value = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret, serializer: JSON).encrypt_and_sign("bar")
     @request.headers["Cookie"] = "foo=#{json_value}"
 
     get :get_encrypted_cookie
@@ -636,6 +636,20 @@ class CookiesTest < ActionController::TestCase
     assert_nil @response.cookies["foo"]
   end
 
+
+  def test_compat_encrypted_cookie_using_64_byte_key
+    # Cookie generated with 64 bytes secret
+    message = ["566d4e75536d686e633246564e6b493062557079626c566d51574d30515430394c53315665564a694e4563786555744f57537454576b396a5a31566a626e52525054303d2d2d34663234333330623130623261306163363562316266323335396164666364613564643134623131"].pack('H*')
+    @request.headers["Cookie"] = "foo=#{message}"
+
+    get :get_encrypted_cookie
+
+    cookies = @controller.send :cookies
+    assert_not_equal "bar", cookies[:foo]
+    assert_equal "bar", cookies.encrypted[:foo]
+    assert_nil @response.cookies["foo"]
+  end
+
   def test_accessing_nonexistent_encrypted_cookie_should_not_raise_invalid_message
     get :set_encrypted_cookie
     assert_nil @controller.send(:cookies).encrypted[:non_existent_attribute]
@@ -799,8 +813,8 @@ class CookiesTest < ActionController::TestCase
     key_generator = @request.env["action_dispatch.key_generator"]
     secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
     sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret)
-    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+    encryptor = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret)
+    assert_equal 'bar', encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_json_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
@@ -838,8 +852,8 @@ class CookiesTest < ActionController::TestCase
     key_generator = @request.env["action_dispatch.key_generator"]
     secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
     sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: JSON)
-    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+    encryptor = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret, serializer: JSON)
+    assert_equal 'bar', encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_json_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_hybrid_jar_if_both_secret_token_and_secret_key_base_are_set
@@ -877,8 +891,8 @@ class CookiesTest < ActionController::TestCase
     key_generator = @request.env["action_dispatch.key_generator"]
     secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
     sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: JSON)
-    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+    encryptor = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret, serializer: JSON)
+    assert_equal 'bar', encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_marshal_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_hybrid_jar_if_both_secret_token_and_secret_key_base_are_set
@@ -916,8 +930,8 @@ class CookiesTest < ActionController::TestCase
     key_generator = @request.env["action_dispatch.key_generator"]
     secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_cookie_salt"])
     sign_secret = key_generator.generate_key(@request.env["action_dispatch.encrypted_signed_cookie_salt"])
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: JSON)
-    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+    encryptor = ActiveSupport::MessageEncryptor.new(secret[0..31], sign_secret, serializer: JSON)
+    assert_equal 'bar', encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_signed_cookie_is_treated_as_nil_by_signed_cookie_jar_if_tampered
diff --git a/activesupport/test/message_encryptor_test.rb b/activesupport/test/message_encryptor_test.rb
index fb0b1e377d..fc17fdf3ee 100644
--- a/activesupport/test/message_encryptor_test.rb
+++ b/activesupport/test/message_encryptor_test.rb
@@ -48,6 +48,16 @@ class MessageEncryptorTest < ActiveSupport::TestCase
     assert_equal @data, @encryptor.decrypt_and_verify(message)
   end
 
+  def test_backwards_compat_for_64_bytes_key
+    # 64 bit key
+    secret = ["3942b1bf81e622559ed509e3ff274a780784fe9e75b065866bd270438c74da822219de3156473cc27df1fd590e4baf68c95eeb537b6e4d4c5a10f41635b5597e"].pack('H*')
+    # Encryptor with 32 bit key, 64 bit secret for verifier
+    encryptor = ActiveSupport::MessageEncryptor.new(secret[0..31], secret)
+    # Message generated with 64 bit key
+    message = "eHdGeExnZEwvMSt3U3dKaFl1WFo0TjVvYzA0eGpjbm5WSkt5MXlsNzhpZ0ZnbWhBWFlQZTRwaXE1bVJCS2oxMDZhYVp2dVN3V0lNZUlWQ3c2eVhQbnhnVjFmeVVubmhRKzF3WnZyWHVNMDg9LS1HSisyakJVSFlPb05ISzRMaXRzcFdBPT0=--831a1d54a3cda8a0658dc668a03dedcbce13b5ca"
+    assert_equal 'data', encryptor.decrypt_and_verify(message)[:some]
+  end
+
   def test_alternative_serialization_method
     prev = ActiveSupport.use_standard_json_time_format
     ActiveSupport.use_standard_json_time_format = true