Encrypt application setting tokens

This is the plan to encrypt the plaintext tokens:

First release (this commit):
  1. Create new encrypted fields in the database.
  2. Start populating new encrypted fields, read the encrypted fields or
     fallback to the plaintext fields.
  3. Backfill the data removing the plaintext fields to the encrypted fields.

Second release:
  4. Remove the virtual attribute (created in step 2).
  5. Drop plaintext columns from the database (empty columns after step 3).

2 files changed, 102 insertions, 0 deletions

diff --git a/spec/migrations/encrypt_plaintext_attributes_on_application_settings_spec.rb b/spec/migrations/encrypt_plaintext_attributes_on_application_settings_spec.rb
new file mode 100644
index 00000000000..6435e43f38c
--- /dev/null
+++ b/spec/migrations/encrypt_plaintext_attributes_on_application_settings_spec.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'migrate', '20191120115530_encrypt_plaintext_attributes_on_application_settings.rb')
+
+describe EncryptPlaintextAttributesOnApplicationSettings, :migration do
+  let(:migration) { described_class.new }
+  let(:application_settings) { table(:application_settings) }
+  let(:plaintext) { 'secret-token' }
+
+  PLAINTEXT_ATTRIBUTES = %w[
+    akismet_api_key
+    elasticsearch_aws_secret_access_key
+    recaptcha_private_key
+    recaptcha_site_key
+    slack_app_secret
+    slack_app_verification_token
+  ].freeze
+
+  describe '#up' do
+    it 'encrypts token, saves it and removes plaintext token' do
+      application_setting = application_settings.create
+      application_setting.update_columns(
+        PLAINTEXT_ATTRIBUTES.each_with_object({}) do |plaintext_attribute, attributes|
+          attributes[plaintext_attribute] = plaintext
+        end
+      )
+
+      migration.up
+
+      application_setting.reload
+      PLAINTEXT_ATTRIBUTES.each do |plaintext_attribute|
+        expect(application_setting[plaintext_attribute]).to be_nil
+        expect(application_setting["encrypted_#{plaintext_attribute}"]).not_to be_nil
+        expect(application_setting["encrypted_#{plaintext_attribute}_iv"]).not_to be_nil
+      end
+    end
+  end
+
+  describe '#down' do
+    it 'decrypts encrypted token and saves it' do
+      application_setting = application_settings.create(
+        PLAINTEXT_ATTRIBUTES.each_with_object({}) do |plaintext_attribute, attributes|
+          attributes[plaintext_attribute] = plaintext
+        end
+      )
+
+      migration.down
+
+      application_setting.reload
+      PLAINTEXT_ATTRIBUTES.each do |plaintext_attribute|
+        expect(application_setting[plaintext_attribute]).to eq(plaintext)
+        expect(application_setting["encrypted_#{plaintext_attribute}"]).to be_nil
+        expect(application_setting["encrypted_#{plaintext_attribute}_iv"]).to be_nil
+      end
+    end
+  end
+end
diff --git a/spec/models/application_setting_spec.rb b/spec/models/application_setting_spec.rb
index ba3b99f4421..7b1ebe586cd 100644
--- a/spec/models/application_setting_spec.rb
+++ b/spec/models/application_setting_spec.rb
@@ -15,6 +15,50 @@ describe ApplicationSetting do
   it { expect(setting.uuid).to be_present }
   it { expect(setting).to have_db_column(:auto_devops_enabled) }
 
+  context "with existing plaintext attributes" do
+    before do
+      setting.update_columns(
+        akismet_api_key: "akismet_api_key",
+        elasticsearch_aws_secret_access_key: "elasticsearch_aws_secret_access_key",
+        recaptcha_private_key: "recaptcha_private_key",
+        recaptcha_site_key: "recaptcha_site_key",
+        slack_app_secret: "slack_app_secret",
+        slack_app_verification_token: "slack_app_verification_token"
+      )
+    end
+
+    it "returns the attributes" do
+      expect(setting.akismet_api_key).to eq("akismet_api_key")
+      expect(setting.elasticsearch_aws_secret_access_key).to eq("elasticsearch_aws_secret_access_key")
+      expect(setting.recaptcha_private_key).to eq("recaptcha_private_key")
+      expect(setting.recaptcha_site_key).to eq("recaptcha_site_key")
+      expect(setting.slack_app_secret).to eq("slack_app_secret")
+      expect(setting.slack_app_verification_token).to eq("slack_app_verification_token")
+    end
+  end
+
+  context "with encrypted attributes" do
+    before do
+      setting.update(
+        akismet_api_key: "akismet_api_key",
+        elasticsearch_aws_secret_access_key: "elasticsearch_aws_secret_access_key",
+        recaptcha_private_key: "recaptcha_private_key",
+        recaptcha_site_key: "recaptcha_site_key",
+        slack_app_secret: "slack_app_secret",
+        slack_app_verification_token: "slack_app_verification_token"
+      )
+    end
+
+    it "returns the attributes" do
+      expect(setting.akismet_api_key).to eq("akismet_api_key")
+      expect(setting.elasticsearch_aws_secret_access_key).to eq("elasticsearch_aws_secret_access_key")
+      expect(setting.recaptcha_private_key).to eq("recaptcha_private_key")
+      expect(setting.recaptcha_site_key).to eq("recaptcha_site_key")
+      expect(setting.slack_app_secret).to eq("slack_app_secret")
+      expect(setting.slack_app_verification_token).to eq("slack_app_verification_token")
+    end
+  end
+
   describe 'validations' do
     let(:http)  { 'http://example.com' }
     let(:https) { 'https://example.com' }