Default Message Encryptor Cipher to AES-256-GCM From AES-256-CBC #29263

assain · 2017-05-29T09:05:06Z

@kaspth
Currently ActiveSupport::MessageEncryptor defaults to CBC encryption, but it could stand to benefit from defaulting to aes-256-gcm encryption for the same reasons as cookies.

kaspth · 2017-05-29T18:28:52Z

Gemfile.lock

@@ -433,4 +433,4 @@ DEPENDENCIES
  websocket-client-simple!

 BUNDLED WITH
-   1.14.6
+   1.15.0


Please remove these Gemfile.lock changes. See Eileen's contributing to Rails workshop around amending and rebasing for some help on how: https://youtu.be/7zoD6NZy6vY?t=1h25s

Thank you for the feedback @kaspth, I'll fix it and add another commit 👍

Don't add another commit. Just rebase/amend this one :)

kaspth · 2017-05-29T18:34:27Z

For some reason Travis didn't run your pull request. Try the rebase/amend then force push.

kaspth · 2017-06-03T18:23:21Z

activesupport/test/message_encryptor_test.rb

@@ -119,7 +119,7 @@ def assert_not_decrypted(value)
    end

    def assert_not_verified(value)
-      assert_raise(ActiveSupport::MessageVerifier::InvalidSignature) do
+      assert_raise(ActiveSupport::MessageEncryptor::InvalidMessage) do


Why is this change needed?

Previously the setup method used aes-256-cbc cipher while writing this test and had made use of Message Verifier. However, after playing around with the tests, I realized this test was failing because ActiveSupport::MessageVerifier::InvalidSignature was raised by message verifier, and the new default cipher - aes-256-gcm used NullVerifier.

kaspth · 2017-06-03T18:28:17Z

Okay, now we'll need a similar setting to what the AEAD cookies has here: https://github.com/rails/rails/pull/28132/files#diff-7f4141d796a8aad409136b2b6dc774b0R15

E.g. that there's a new 5.2 config to default the encryptor to gcm:

# Other configs in new_framework_defaults_5_2.rb…

# Default encrypted messages to use AES-256-GCM encryption.
# Rails.application.active_support.message_encryptor.use_authenticated_encryption = true

Then auto default that to true in load_defaults under "5.2".

If we don't have that config, we break backwardscompatibility — that's what the test failures show.

kaspth · 2017-06-06T18:35:25Z

...ib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt

@@ -13,3 +13,6 @@
 # Use AES 256 GCM authenticated encryption for encrypted cookies.
 # Existing cookies will be converted on read then written with the new scheme.
 # Rails.application.config.action_dispatch.use_authenticated_cookie_encryption = true
+
+# Use AES 256 GCM authenticated encryption as default for encrypting messages.
+# Rails.application.config.active_support.message_encryptor.use_authenticated_cookie_encryption = true


Shouldn't say use_authenticated_cookie_encryption but just use_authenticated_encryption 😊

I had corrected that mistake, don't know how it crept in again. Apologies! :)

kaspth · 2017-06-06T18:36:20Z

...ib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt

@@ -13,3 +13,6 @@
 # Use AES 256 GCM authenticated encryption for encrypted cookies.
 # Existing cookies will be converted on read then written with the new scheme.
 # Rails.application.config.action_dispatch.use_authenticated_cookie_encryption = true


Ideally, we should be able to remove this config and use the below one to infer it. But that's for another time.

cc @mikeycgto

kaspth · 2017-06-11T13:55:19Z

activesupport/lib/active_support/message_encryptor.rb

    # bits. If you are using a user-entered secret, you can generate a suitable
    # key by using <tt>ActiveSupport::KeyGenerator</tt> or a similar key
-    # derivation function.
+    # derivation function


Keep the period.

kaspth · 2017-06-11T13:55:31Z

activesupport/lib/active_support/message_encryptor.rb

@@ -66,7 +77,7 @@ def initialize(secret, *signature_key_or_options)
      sign_secret = signature_key_or_options.first
      @secret = secret
      @sign_secret = sign_secret
-      @cipher = options[:cipher] || DEFAULT_CIPHER
+      @cipher = options[:cipher] || MessageEncryptor.default_cipher


self.class.default_cipher

kaspth · 2017-06-11T13:57:01Z

activesupport/lib/active_support/message_encryptor.rb

@@ -19,7 +19,18 @@ module ActiveSupport
  #   encrypted_data = crypt.encrypt_and_sign('my secret data')                  # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
  #   crypt.decrypt_and_verify(encrypted_data)                                   # => "my secret data"
  class MessageEncryptor
-    DEFAULT_CIPHER = "aes-256-cbc"
+    class << self
+      #use_authenticated_message_encryption is used to activate 'aes-256-gcm' as default cipher


This comment doesn't really add anything to me. Let's just document it elsewhere.

kaspth · 2017-06-11T13:57:48Z

...ib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt

@@ -13,3 +13,6 @@
 # Use AES 256 GCM authenticated encryption for encrypted cookies.
 # Existing cookies will be converted on read then written with the new scheme.
 # Rails.application.config.action_dispatch.use_authenticated_cookie_encryption = true
+
+# Use AES 256 GCM authenticated encryption as default for encrypting messages.


as default for -> when

kaspth · 2017-06-11T14:04:14Z

activesupport/lib/active_support/railtie.rb

+      ActiveSupport::MessageEncryptor.use_authenticated_message_encryption = true
+    else
+      ActiveSupport::MessageEncryptor.use_authenticated_message_encryption = false
+    end


This all needs to be wrapped in an initializer (with a descriptive name) so it's run when the app boots and not when this file is parsed.

This Railtie subclass is marked as # :nodoc meaning it won't show up in documentation, so just skip the comments here.

I'd rewrite to this within the initializer:

if config.active_support.respond_to?(:use_authenticated_message_encryption) ActiveSupport::MessageEncryptor.use_authenticated_message_encryption = config.active_support.use_authenticated_message_encryption end

We have to use respond_to? because config.active_support, an instance of ActiveSupport::OrderedOptions, raises if the key is unassigned.

kaspth · 2017-06-11T14:08:32Z

Woah, hey you got the tests to pass! 👏 — make sure you look at Code Climate too, there's one thing missing there. 😊

Now we just need to test that the default change works. Let's just go with setting use_authenticated_message_encryption in the Message Encryptor test and inspecting default_cipher for now.

Also: default_cipher should be marked as def default_cipher # :nodoc:, don't think that should be public API for people.

assain · 2017-06-11T16:42:18Z

activesupport/lib/active_support/railtie.rb

@@ -7,6 +7,13 @@ class Railtie < Rails::Railtie # :nodoc:

    config.eager_load_namespaces << ActiveSupport

+    initializer "active_support.set_authenticated_message_encryption_as_default" do |app|


@kaspth
Whenever, I make this change, Travis CI fails, because of sessions_test.rb which outputs:

Failure:
ApplicationTests::MiddlewareSessionTest#test_session_upgrading_from_AES-CBC-HMAC_encryption_to_AES-GCM_encryption [test/application/middleware/session_test.rb:351]:
Expected: "1"
Actual: ""

Yep, see the other comment about why 😊

Let's just clip "_as_default" from the initializer title while we're here.

kaspth

So close now!

kaspth · 2017-06-11T18:07:33Z

railties/test/application/middleware/session_test.rb

@@ -339,6 +339,9 @@ def read_raw_cookie

        # Enable AEAD cookies
        config.action_dispatch.use_authenticated_cookie_encryption = true
+
+        # Enable Authenticated Message Encryption.
+        config.active_support.use_authenticated_message_encryption = true


This will be true by default, so there's no need to set this.

We should assign the cbc cipher: to the legacy encryptor in cookies middleware. Then the test passes.

kaspth · 2017-06-11T18:08:54Z

activesupport/lib/active_support/railtie.rb

@@ -7,6 +7,13 @@ class Railtie < Rails::Railtie # :nodoc:

    config.eager_load_namespaces << ActiveSupport

+    initializer "active_support.set_authenticated_message_encryption_as_default" do |app|


Yep, see the other comment about why 😊

Let's just clip "_as_default" from the initializer title while we're here.

kaspth · 2017-06-11T18:09:33Z

activesupport/lib/active_support/message_encryptor.rb

+    class << self
+      attr_accessor :use_authenticated_message_encryption
+
+      def default_cipher


Needs a # :nodoc same for the use_authenticated_message_encryption accessor.

kaspth · 2017-06-11T18:49:51Z

railties/test/application/middleware/session_test.rb

@@ -290,7 +290,7 @@ def read_raw_cookie
      get "/foo/read_encrypted_cookie"
      assert_equal "2", last_response.body

-      cipher = "aes-256-gcm"
+        


This shouldn't be changed.

Oops! My bad!

kaspth · 2017-06-11T18:49:57Z

railties/test/application/middleware/session_test.rb

@@ -339,7 +339,8 @@ def read_raw_cookie

        # Enable AEAD cookies
        config.action_dispatch.use_authenticated_cookie_encryption = true
-      RUBY
+
+        RUBY


This neither.

kaspth · 2017-06-11T18:50:14Z

actionpack/lib/action_dispatch/middleware/cookies.rb

@@ -630,7 +630,7 @@ def initialize(parent_jar)
        secret = key_generator.generate_key(request.encrypted_cookie_salt || "")[0, ActiveSupport::MessageEncryptor.key_len]
        sign_secret = key_generator.generate_key(request.encrypted_signed_cookie_salt || "")

-        @legacy_encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
+        @legacy_encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: 'aes-256-cbc', digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)


Use double quoted strings.

- Introduce a method to select default cipher, and maintain backward compatibility

Follow up of rails#29263

rails-bot assigned rafaelfranca May 29, 2017

kaspth assigned kaspth and unassigned rafaelfranca May 29, 2017

kaspth reviewed May 29, 2017

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maclover7 added activesupport needs work labels May 30, 2017

kaspth reviewed Jun 3, 2017

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kaspth reviewed Jun 6, 2017

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kaspth reviewed Jun 11, 2017

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assain commented Jun 11, 2017

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kaspth reviewed Jun 11, 2017

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set message_encryptor default cipher to aes-256-gcm

7440bf4

- Introduce a method to select default cipher, and maintain backward compatibility

kaspth approved these changes Jun 11, 2017

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kaspth merged commit 6d402c6 into rails:master Jun 11, 2017

y-yagi added a commit to y-yagi/rails that referenced this pull request Jun 11, 2017

Fix Message::Encryptor default cipher [ci skip]

9231d2a

Follow up of rails#29263

y-yagi mentioned this pull request Jun 11, 2017

Fix Message::Encryptor default cipher [ci skip] #29422

Merged

eugeneius mentioned this pull request Dec 22, 2017

Allow use_authenticated_message_encryption to be set in new_framework_defaults_5_2.rb #31547

Merged

nalabjp mentioned this pull request Dec 18, 2018

ActiveSupport::MessageEncryptor' cipher option alpaca-tc/active_record_encryption#13

Closed

ryanvall mentioned this pull request Feb 16, 2022

Rails 5.2 Upgrade Compatibility jaredonline/google-authenticator#62

Closed

alpaca-tc mentioned this pull request Jul 25, 2024

how to update historical unencrypted data alpaca-tc/active_record_encryption#33

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Default Message Encryptor Cipher to AES-256-GCM From AES-256-CBC #29263

Default Message Encryptor Cipher to AES-256-GCM From AES-256-CBC #29263

assain commented May 29, 2017

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		@@ -7,6 +7,13 @@ class Railtie < Rails::Railtie # :nodoc:

		config.eager_load_namespaces << ActiveSupport

		initializer "active_support.set_authenticated_message_encryption_as_default" do \|app\|

Default Message Encryptor Cipher to AES-256-GCM From AES-256-CBC #29263

Default Message Encryptor Cipher to AES-256-GCM From AES-256-CBC #29263

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