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).

1 files changed, 93 insertions, 0 deletions

diff --git a/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb b/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb
new file mode 100644
index 00000000000..d7abb29fd75
--- /dev/null
+++ b/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb
@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+class EncryptPlaintextAttributesOnApplicationSettings < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  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
+
+  class ApplicationSetting < ActiveRecord::Base
+    self.table_name = 'application_settings'
+
+    def self.encryption_options_base_truncated_aes_256_gcm
+      {
+        mode: :per_attribute_iv,
+        key: Gitlab::Application.secrets.db_key_base[0..31],
+        algorithm: 'aes-256-gcm',
+        encode: true
+      }
+    end
+
+    attr_encrypted :akismet_api_key, encryption_options_base_truncated_aes_256_gcm
+    attr_encrypted :elasticsearch_aws_secret_access_key, encryption_options_base_truncated_aes_256_gcm
+    attr_encrypted :recaptcha_private_key, encryption_options_base_truncated_aes_256_gcm
+    attr_encrypted :recaptcha_site_key, encryption_options_base_truncated_aes_256_gcm
+    attr_encrypted :slack_app_secret, encryption_options_base_truncated_aes_256_gcm
+    attr_encrypted :slack_app_verification_token, encryption_options_base_truncated_aes_256_gcm
+
+    def akismet_api_key
+      decrypt(:akismet_api_key, self[:encrypted_akismet_api_key]) || self[:akismet_api_key]
+    end
+
+    def elasticsearch_aws_secret_access_key
+      decrypt(:elasticsearch_aws_secret_access_key, self[:encrypted_elasticsearch_aws_secret_access_key]) || self[:elasticsearch_aws_secret_access_key]
+    end
+
+    def recaptcha_private_key
+      decrypt(:recaptcha_private_key, self[:encrypted_recaptcha_private_key]) || self[:recaptcha_private_key]
+    end
+
+    def recaptcha_site_key
+      decrypt(:recaptcha_site_key, self[:encrypted_recaptcha_site_key]) || self[:recaptcha_site_key]
+    end
+
+    def slack_app_secret
+      decrypt(:slack_app_secret, self[:encrypted_slack_app_secret]) || self[:slack_app_secret]
+    end
+
+    def slack_app_verification_token
+      decrypt(:slack_app_verification_token, self[:encrypted_slack_app_verification_token]) || self[:slack_app_verification_token]
+    end
+  end
+
+  def up
+    ApplicationSetting.find_each do |application_setting|
+      # We are using the setter from attr_encrypted gem to encrypt the data.
+      # The gem updates the two columns needed to decrypt the value:
+      # - "encrypted_#{plaintext_attribute}"
+      # - "encrypted_#{plaintext_attribute}_iv"
+      application_setting.assign_attributes(
+        PLAINTEXT_ATTRIBUTES.each_with_object({}) do |plaintext_attribute, attributes|
+          attributes[plaintext_attribute] = application_setting.send(plaintext_attribute)
+        end
+      )
+      application_setting.save(validate: false)
+
+      application_setting.update_columns(
+        PLAINTEXT_ATTRIBUTES.each_with_object({}) do |plaintext_attribute, attributes|
+          attributes[plaintext_attribute] = nil
+        end
+      )
+    end
+  end
+
+  def down
+    ApplicationSetting.find_each do |application_setting|
+      application_setting.update_columns(
+        PLAINTEXT_ATTRIBUTES.each_with_object({}) do |plaintext_attribute, attributes|
+          attributes[plaintext_attribute] = application_setting.send(plaintext_attribute)
+          attributes["encrypted_#{plaintext_attribute}"] = nil
+          attributes["encrypted_#{plaintext_attribute}_iv"] = nil
+        end
+      )
+    end
+  end
+end