From: Andy Lutomirski Subject: Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs Date: Wed, 14 Dec 2016 08:22:52 -0800 Message-ID: References: <627e948e37314c13a67c90917386c814c56b8e20.1481683609.git.luto@kernel.org> <18039.1481704679@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , USB list , keyrings@vger.kernel.org, Eric Biggers , linux-crypto@vger.kernel.org, Herbert Xu , Stephan Mueller To: David Howells Return-path: In-Reply-To: <18039.1481704679@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Wed, Dec 14, 2016 at 12:37 AM, David Howells wrote: > Andy Lutomirski wrote: > >> > - sg_set_buf(&sg_out[1], pad, sizeof pad); >> > + sg_set_buf(&sg_out[1], empty_zero_page, 16); >> >> My fix here is obviously bogus (I meant to use ZERO_PAGE(0)), but what >> exactly is the code trying to do? The old code makes no sense. It's >> setting the *output* buffer to zeroed padding. > > Padding goes into the encrypt function and is going to come out of the decrypt > function. Possibly derived_key_decrypt() should be checking that the padding > that comes out is actually a bunch of zeros. Maybe we don't actually need to > get the padding out, but I'm not sure whether the crypto layer will > malfunction if we don't give it a buffer for the padding. It was the memset that threw me for a loop. David, are these encrypted keys ever exported anywhere? If not, could the code use a mode that doesn't need padding? --Andy > > David -- Andy Lutomirski AMA Capital Management, LLC