From 71fb6def5f07233e4fdf628e02981e4add5c6b8b Mon Sep 17 00:00:00 2001 From: Michael Coyne Date: Mon, 15 May 2017 08:45:14 +0000 Subject: [PATCH] Fix for AEAD auth_tag check in MessageEncryptor When MessageEncryptor tries to +decrypt_and_verify+ ciphertexts generated in a different mode (such CBC-HMAC), the +auth_tag+ may be +nil+ and must explicitly check for it. See the discussion here: https://github.com/rails/rails/pull/28132#discussion_r116388462 --- activesupport/lib/active_support/message_encryptor.rb | 2 +- activesupport/test/message_encryptor_test.rb | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb index 0671469788..9589dba3ca 100644 --- a/activesupport/lib/active_support/message_encryptor.rb +++ b/activesupport/lib/active_support/message_encryptor.rb @@ -110,7 +110,7 @@ module ActiveSupport # Currently the OpenSSL bindings do not raise an error if auth_tag is # truncated, which would allow an attacker to easily forge it. See # https://github.com/ruby/openssl/issues/63 - raise InvalidMessage if aead_mode? && auth_tag.bytes.length != 16 + raise InvalidMessage if aead_mode? && (auth_tag.nil? || auth_tag.bytes.length != 16) cipher.decrypt cipher.key = @secret diff --git a/activesupport/test/message_encryptor_test.rb b/activesupport/test/message_encryptor_test.rb index 56a436f751..c67ada5f20 100644 --- a/activesupport/test/message_encryptor_test.rb +++ b/activesupport/test/message_encryptor_test.rb @@ -86,6 +86,14 @@ class MessageEncryptorTest < ActiveSupport::TestCase assert_equal @data, encryptor.decrypt_and_verify(message) end + def test_aead_mode_with_hmac_cbc_cipher_text + encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm") + + assert_raise ActiveSupport::MessageEncryptor::InvalidMessage do + encryptor.decrypt_and_verify "eHdGeExnZEwvMSt3U3dKaFl1WFo0TjVvYzA0eGpjbm5WSkt5MXlsNzhpZ0ZnbWhBWFlQZTRwaXE1bVJCS2oxMDZhYVp2dVN3V0lNZUlWQ3c2eVhQbnhnVjFmeVVubmhRKzF3WnZyWHVNMDg9LS1HSisyakJVSFlPb05ISzRMaXRzcFdBPT0=--831a1d54a3cda8a0658dc668a03dedcbce13b5ca" + end + end + def test_messing_with_aead_values_causes_failures encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm") text, iv, auth_tag = encryptor.encrypt_and_sign(@data).split("--")