Initial commit

app/services/encryption_service.rb

@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+class EncryptionService
+  # Example: 202040
+  # Week number starts from 0
+  def self.current_salt
+    Time.now.strftime('%Y%W')
+  end
+
+  def self.pack(salt, value)
+    [salt, value].join('.')
+  end
+
+  def self.unpack(str)
+    raise "Invalid encrypted value: #{str}" unless str =~ (/(\w*)\.(.*)/)
+    [$1, $2]
+  end
+
+  def self.encrypt(value)
+    # Get current salt
+    salt = current_salt
+    # Get or generate new master key from salt
+    current_key = get_master_key(salt)
+    # Encrypt attribute value
+    encrypted_key = encryptor(current_key).encrypt_and_sign(value)
+    # Add salt before encrypted value
+    pack(salt, encrypted_key)
+  end
+
+  def self.decrypt(value)
+    # Unpack salt and encrypted_key
+    salt, encrypted_key = unpack(value)
+    # Get master key from salt
+    master_key = get_master_key(salt)
+    # Decrypt encrypted value for attribute
+    encryptor(master_key).decrypt_and_verify(encrypted_key)
+  end
+
+  private
+
+  def self.encryptor(key)
+    ActiveSupport::MessageEncryptor.new(key)
+  end
+
+  def self.get_master_key(salt)
+    @cache ||= {}
+    # Delete keys with expired date
+    delete_expired_keys
+
+    unless @cache[salt]
+      # Initialize hash for specific salt
+      @cache[salt] = {}
+
+      # Put key value from key generator
+      @cache[salt]['key'] = ActiveSupport::KeyGenerator.new(
+        ENV.fetch('SECRET_KEY_BASE')
+      ).generate_key(salt, ActiveSupport::MessageEncryptor.key_len)
+
+      # Put expire date for specific key
+      @cache[salt]['expire_date'] = 1.week.from_now
+    end
+
+    @cache[salt]['key']
+  end
+
+  def self.delete_expired_keys
+    return unless @cache.is_a?(Hash)
+
+    # Iterate through all @cache values
+    @cache.each do |salt, values|
+      # Delete key if expire date expired
+      @cache.delete(salt) if values['expire_date'].present? && values['expire_date'] < Time.now
+    end
+  end
+end