Add cookie rotation for switching from SHA1 to SHA256

config/initializers/cookie_rotator.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+Rails.application.config.after_initialize do
+  Rails.application.config.action_dispatch.cookies_rotations.tap do |cookies|
+    salt = Rails.application.config.action_dispatch.authenticated_encrypted_cookie_salt
+    secret_key_base = Rails.application.secret_key_base
+
+    key_generator = ActiveSupport::KeyGenerator.new(
+      secret_key_base, iterations: 1000, hash_digest_class: OpenSSL::Digest::SHA1
+    )
+    key_len = ActiveSupport::MessageEncryptor.key_len
+    secret = key_generator.generate_key(salt, key_len)
+
+    cookies.rotate :encrypted, secret
+  end
+end