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[209.132.180.67]) by mx.google.com with ESMTP id t191si2923471pgd.370.2019.07.20.08.25.22; Sat, 20 Jul 2019 08:25:42 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-crypto-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=2GwRSuZC; spf=pass (google.com: best guess record for domain of linux-crypto-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-crypto-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726535AbfGTG6J (ORCPT + 99 others); Sat, 20 Jul 2019 02:58:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:51836 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726533AbfGTG6J (ORCPT ); Sat, 20 Jul 2019 02:58:09 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BC18E21873; Sat, 20 Jul 2019 06:58:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563605889; bh=OFZAHQHXLV8GwXYrMSGu/SOmauNVVlNoeQquIaDV4sg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2GwRSuZC0c9rkYEqR9wXTttGef4p2LVlv9kQc/mhRUi6jC9Kdbzw58EUyS9cKb8xH aUEJWIQyPe8x70Kgu0U8Ql9DAn+hLv77YXg1Le91HwmYfDGa5iEBwechIsO2RsbHWr 2u/lUp7HMyk0KqUUG2/wVX+A9JoxKsG3BNu47G00= Date: Fri, 19 Jul 2019 23:58:07 -0700 From: Eric Biggers To: Milan Broz Cc: Pascal Van Leeuwen , Herbert Xu , Ard Biesheuvel , "dm-devel@redhat.com" , "linux-crypto@vger.kernel.org" , Horia Geanta Subject: Re: [dm-devel] xts fuzz testing and lack of ciphertext stealing support Message-ID: <20190720065807.GA711@sol.localdomain> Mail-Followup-To: Milan Broz , Pascal Van Leeuwen , Herbert Xu , Ard Biesheuvel , "dm-devel@redhat.com" , "linux-crypto@vger.kernel.org" , Horia Geanta References: <20190716221639.GA44406@gmail.com> <20190717172823.GA205944@gmail.com> <20190718065223.4xaefcwjoxvujntw@gondor.apana.org.au> <20190718072154.m2umem24x4grbf6w@gondor.apana.org.au> <36e78459-1594-6d19-0ab4-95b03a6de036@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Thu, Jul 18, 2019 at 01:19:41PM +0200, Milan Broz wrote: > > > From that perspective - to prevent people from doing cryptographically stupid things - > > IMHO it would be better to just pull the CTS into the XTS implementation i.e. make > > xts natively support blocks that are not a multiple of (but >=) the cipher blocksize ... > > I would definitely prefer adding CTS directly to XTS (as it is in gcrypt or OpenSSL now) > instead of some new compositions. > > Also, I would like to avoid another "just because it is nicer" module dependence (XTS->XEX->ECB). > Last time (when XTS was reimplemented using ECB) we have many reports with initramfs > missing ECB module preventing boot from AES-XTS encrypted root after kernel upgrade... > Just saying. (Despite the last time it was keyring what broke encrypted boot ;-) > Can't the "missing modules in initramfs" issue be solved by using a MODULE_SOFTDEP()? Actually, why isn't that being used for xts -> ecb already? (There was also a bug where CONFIG_CRYPTO_XTS didn't select CONFIG_CRYPTO_ECB, but that was simply a bug, which was fixed.) Or "xts" and "xex" could go in the same kernel module xts.ko, which would make this a non-issue. Anyway, I agree that the partial block support, if added, should just be made available under the name "xts", as people would expect. It doesn't need a new name. - Eric