From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F09A7C433FE for ; Fri, 4 Dec 2020 15:01:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C470922B47 for ; Fri, 4 Dec 2020 15:01:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388358AbgLDPBK (ORCPT ); Fri, 4 Dec 2020 10:01:10 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:35798 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730406AbgLDPBJ (ORCPT ); Fri, 4 Dec 2020 10:01:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607093983; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=OTBOnyE1n+B2er0y+QuZYiU0VZBSiLUvAG5osfhcmQc=; b=gPWG0q4t20Ry4+O/ui8q22rrjqbd99D4pGBAxMWTThYGZo6S51VSvDbd9+UwRrSyzYyVCh 10zuCQbXp9rIojvimcRxEyWvqGuxFEQ52/c3IjIs3FQ88ixBQpMtDgN7CO92UFo/J1ih35 XoHx06vb+U3Q/VIK5s0O9Amtxo/TWzQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-52-PzPPozy8PUqmAMwzJKEjCw-1; Fri, 04 Dec 2020 09:59:41 -0500 X-MC-Unique: PzPPozy8PUqmAMwzJKEjCw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2FE30107ACE3; Fri, 4 Dec 2020 14:59:39 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-116-67.rdu2.redhat.com [10.10.116.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id B307A18AD4; Fri, 4 Dec 2020 14:59:36 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <2F96670A-58DC-43A6-A20E-696803F0BFBA@oracle.com> References: <2F96670A-58DC-43A6-A20E-696803F0BFBA@oracle.com> <160518586534.2277919.14475638653680231924.stgit@warthog.procyon.org.uk> To: Chuck Lever , Bruce Fields Cc: dhowells@redhat.com, CIFS , Linux NFS Mailing List , Herbert Xu , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Trond Myklebust , linux-crypto@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org Subject: Why the auxiliary cipher in gss_krb5_crypto.c? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <118875.1607093975.1@warthog.procyon.org.uk> Date: Fri, 04 Dec 2020 14:59:35 +0000 Message-ID: <118876.1607093975@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chuck, Bruce, Why is gss_krb5_crypto.c using an auxiliary cipher? For reference, the gss_krb5_aes_encrypt() code looks like the attached. >From what I can tell, in AES mode, the difference between the main cipher and the auxiliary cipher is that the latter is "cbc(aes)" whereas the former is "cts(cbc(aes))" - but they have the same key. Reading up on CTS, I'm guessing the reason it's like this is that CTS is the same as the non-CTS, except for the last two blocks, but the non-CTS one is more efficient. David --- nbytes = buf->len - offset - GSS_KRB5_TOK_HDR_LEN; nblocks = (nbytes + blocksize - 1) / blocksize; cbcbytes = 0; if (nblocks > 2) cbcbytes = (nblocks - 2) * blocksize; memset(desc.iv, 0, sizeof(desc.iv)); if (cbcbytes) { SYNC_SKCIPHER_REQUEST_ON_STACK(req, aux_cipher); desc.pos = offset + GSS_KRB5_TOK_HDR_LEN; desc.fragno = 0; desc.fraglen = 0; desc.pages = pages; desc.outbuf = buf; desc.req = req; skcipher_request_set_sync_tfm(req, aux_cipher); skcipher_request_set_callback(req, 0, NULL, NULL); sg_init_table(desc.infrags, 4); sg_init_table(desc.outfrags, 4); err = xdr_process_buf(buf, offset + GSS_KRB5_TOK_HDR_LEN, cbcbytes, encryptor, &desc); skcipher_request_zero(req); if (err) goto out_err; } /* Make sure IV carries forward from any CBC results. */ err = gss_krb5_cts_crypt(cipher, buf, offset + GSS_KRB5_TOK_HDR_LEN + cbcbytes, desc.iv, pages, 1); if (err) { err = GSS_S_FAILURE; goto out_err; }