From patchwork Sun Jan 24 14:03:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stephan Mueller X-Patchwork-Id: 12042395 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 A8128C433DB for ; Sun, 24 Jan 2021 14:10:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B96522D0A for ; Sun, 24 Jan 2021 14:10:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725910AbhAXOK0 (ORCPT ); Sun, 24 Jan 2021 09:10:26 -0500 Received: from mo4-p02-ob.smtp.rzone.de ([85.215.255.83]:21964 "EHLO mo4-p02-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725838AbhAXOJi (ORCPT ); Sun, 24 Jan 2021 09:09:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1611497205; s=strato-dkim-0002; d=chronox.de; h=References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:From: Subject:Sender; bh=Fyc0rzVotIOUtUm7++3lcJ+qWnVjlyTyBLMUYptLgRk=; b=R5qniK8GEUCy+q1km8pHfRA3ZfmLr+g/RtQOxgxGrUG31E+a94HlTLQqPa4PhbvdVO 8IMgkD+SnbP85DqsK8rVCbHQGfM/w94dkKzhFk4vS9qZPYFJr5EoUaJFgL9czZxAOtUN osKIQlZgsxcuRzuZoMdb/F1Tav/te7zODIapdp/9sJV0NhTaDRbqNAQF1poFrc0WbKqI l4jR88czOkLizwOT2XCKtSF4hjGPX65aEN3X3xTiM2dcgPL2HbqmVUSS4MABFKtXJQef WJYNluT5SXZsO2JRx8meWbgDBk7Q1XrcikwhafslEFpFJqm05wKiRtMEI+GHiusp+vnY d6ag== X-RZG-AUTH: ":P2ERcEykfu11Y98lp/T7+hdri+uKZK8TKWEqNyiHySGSa9k9xmwdNnzGHXPZI/ScIzb9" X-RZG-CLASS-ID: mo00 Received: from positron.chronox.de by smtp.strato.de (RZmta 47.12.1 DYNA|AUTH) with ESMTPSA id Z04c46x0OE6jeiX (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Sun, 24 Jan 2021 15:06:45 +0100 (CET) From: Stephan =?iso-8859-1?q?M=FCller?= To: herbert@gondor.apana.org.au Cc: ebiggers@kernel.org, Jarkko Sakkinen , mathew.j.martineau@linux.intel.com, dhowells@redhat.com, linux-crypto@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org, simo@redhat.com Subject: [PATCH v2 4/7] security: DH - remove dead code for zero padding Date: Sun, 24 Jan 2021 15:03:50 +0100 Message-ID: <2129848.iZASKD2KPV@positron.chronox.de> In-Reply-To: <1772794.tdWV9SEqCh@positron.chronox.de> References: <1772794.tdWV9SEqCh@positron.chronox.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org Remove the specific code that adds a zero padding that was intended to be invoked when the DH operation result was smaller than the modulus. However, this cannot occur any more these days because the function mpi_write_to_sgl is used in the code path that calculates the shared secret in dh_compute_value. This MPI service function guarantees that leading zeros are introduced as needed to ensure the resulting data is exactly as long as the modulus. This implies that the specific code to add zero padding is dead code which can be safely removed. Signed-off-by: Stephan Mueller --- security/keys/dh.c | 25 ++++--------------------- 1 file changed, 4 insertions(+), 21 deletions(-) diff --git a/security/keys/dh.c b/security/keys/dh.c index 1abfa70ed6e1..56e12dae4534 100644 --- a/security/keys/dh.c +++ b/security/keys/dh.c @@ -141,7 +141,7 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc) * 'dlen' must be a multiple of the digest size. */ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, - u8 *dst, unsigned int dlen, unsigned int zlen) + u8 *dst, unsigned int dlen) { struct shash_desc *desc = &sdesc->shash; unsigned int h = crypto_shash_digestsize(desc->tfm); @@ -158,22 +158,6 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, if (err) goto err; - if (zlen && h) { - u8 tmpbuffer[32]; - size_t chunk = min_t(size_t, zlen, sizeof(tmpbuffer)); - memset(tmpbuffer, 0, chunk); - - do { - err = crypto_shash_update(desc, tmpbuffer, - chunk); - if (err) - goto err; - - zlen -= chunk; - chunk = min_t(size_t, zlen, sizeof(tmpbuffer)); - } while (zlen); - } - if (src && slen) { err = crypto_shash_update(desc, src, slen); if (err) @@ -198,7 +182,7 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc, char __user *buffer, size_t buflen, - uint8_t *kbuf, size_t kbuflen, size_t lzero) + uint8_t *kbuf, size_t kbuflen) { uint8_t *outbuf = NULL; int ret; @@ -211,7 +195,7 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc, goto err; } - ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero); + ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len); if (ret) goto err; @@ -384,8 +368,7 @@ long __keyctl_dh_compute(struct keyctl_dh_params __user *params, } ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf, - req->dst_len + kdfcopy->otherinfolen, - outlen - req->dst_len); + req->dst_len + kdfcopy->otherinfolen); } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) { ret = req->dst_len; } else {