From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tadeusz Struk Subject: Re: Intel GCM: __driver-gcm-aes-aesni setkey missing Date: Sat, 17 Jan 2015 17:37:06 -0800 Message-ID: <54BB0E42.9070209@intel.com> References: <1976848.LqsUs5V3zD@tachyon.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Cc: linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, 'LKML' To: Stephan Mueller , aidan.o.mahony@intel.com, gabriele.paoloni@intel.com, adrian.hoban@intel.com Return-path: Received: from mga03.intel.com ([134.134.136.65]:52615 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751225AbbARBka (ORCPT ); Sat, 17 Jan 2015 20:40:30 -0500 In-Reply-To: <1976848.LqsUs5V3zD@tachyon.chronox.de> Sender: linux-crypto-owner@vger.kernel.org List-ID: Hi Stephan, On 01/17/2015 10:23 AM, Stephan Mueller wrote: > during testing of my algif_aead patch with the different GCM implementations I > am able to trigger a kernel crash from user space using __driver-gcm-aes- > aesni. > > As I hope that algif_aead is going to be included, unprivileged userspace > would then reliably crash the kernel -- with the current kernel code, > userspace has no interface to trigger the issue. Yes, that's a problem. > > As I am not sure what the purpose of __driver-gcm-aes-aesni is (only a backend > for RFC4106 GCM or a regular cipher), I did not yet create a patch. IMHO there > are two solutions: > > - either create a valid setkey callback so that a key is set > > - or create a noop setkey that returns -EOPNOTSUPP which effectively disables > that cipher for regular consumption. __driver-gcm-aes-aesni is only a helper for rfc4106-gcm-aesni and it never supposed to be used on it's own. I think implementing a setkey function that only returns an error would be a good solution for this. Another question is what if someone will ignore the error or skip the setsockopt(ALG_SET_KEY) altogether and still call the sendmsg() and read() to trigger encrypt()? > Note, if it is only a backend for the RFC4106 implementation, may I ask why > __driver-gcm-aes-aesni is implemented as a separate cipher that is registered > with the kernel crypto API? This is because we need to have one instance of the helper tfm with its context per each of the rfc4106-gcm-aesni tfm instance and that was one convenient way to do this. Tadeusz