From patchwork Thu Dec 9 09:03:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolai Stange X-Patchwork-Id: 12666141 X-Patchwork-Delegate: herbert@gondor.apana.org.au Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 538A7C433FE for ; Thu, 9 Dec 2021 09:04:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235970AbhLIJIR (ORCPT ); Thu, 9 Dec 2021 04:08:17 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:55054 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235856AbhLIJIK (ORCPT ); Thu, 9 Dec 2021 04:08:10 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id B8C70210FB; Thu, 9 Dec 2021 09:04:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1639040676; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6YCiKQTqTEzYZ4U5yX9xPy3LwehSL+ohGfws/puUkEI=; b=ryy2GNXwod8zc+BRyOl66smMq/EMaQKLaBdeDLMDqMXJBzeBrOj9yn/VVRJYxi3wXwhld2 saLcq4uXlKK9kxmeSdLDmhsCcGLpu58VgFeRZlXToDbslgVxTsLpeUTSYBAdAAI97moCFV YicKKFp8b+adwHXpvD5YQoGNojJIOgA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1639040676; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6YCiKQTqTEzYZ4U5yX9xPy3LwehSL+ohGfws/puUkEI=; b=BR+ms+WHneypz9Uz+ak03bG3mT99PqX7YxQzA7t8fjVilcVs53DDQzDLbBBgnnk/+B1MHT Gv8OUWhQWnColhDQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 9F87513A86; Thu, 9 Dec 2021 09:04:36 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id AisdJaTGsWHeaQAAMHmgww (envelope-from ); Thu, 09 Dec 2021 09:04:36 +0000 From: Nicolai Stange To: Herbert Xu , "David S. Miller" Cc: =?utf-8?q?Stephan_M=C3=BCller?= , Hannes Reinecke , Torsten Duwe , Zaibo Xu , Giovanni Cabiddu , David Howells , Jarkko Sakkinen , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, qat-linux@intel.com, keyrings@vger.kernel.org, Nicolai Stange Subject: [PATCH v2 16/18] crypto: dh - calculate Q from P for the full public key verification Date: Thu, 9 Dec 2021 10:03:56 +0100 Message-Id: <20211209090358.28231-17-nstange@suse.de> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20211209090358.28231-1-nstange@suse.de> References: <20211209090358.28231-1-nstange@suse.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org As the ->q in struct dh_ctx gets never set anywhere, the code in dh_is_pubkey_valid() for doing the full public key validation in accordance to SP800-56Arev3 is effectively dead. However, for safe-prime groups, Q = (P - 1)/2 by definition and this enables dh_is_pubkey_valid() to calculate Q on the fly for these groups. Implement this. With this change, the last code accessing struct dh_ctx's ->q is now gone. Remove this member from struct dh_ctx. Signed-off-by: Nicolai Stange Reviewed-by: Hannes Reinecke --- crypto/dh.c | 40 +++++++++++++++++++++++++++++----------- 1 file changed, 29 insertions(+), 11 deletions(-) diff --git a/crypto/dh.c b/crypto/dh.c index 38547c5301da..bd3ea51fbeb0 100644 --- a/crypto/dh.c +++ b/crypto/dh.c @@ -15,7 +15,6 @@ struct dh_ctx { enum dh_group_id group_id; MPI p; /* Value is guaranteed to be set. */ - MPI q; /* Value is optional. */ MPI g; /* Value is guaranteed to be set. */ MPI xa; /* Value is guaranteed to be set. */ }; @@ -23,7 +22,6 @@ struct dh_ctx { static void dh_clear_ctx(struct dh_ctx *ctx) { mpi_free(ctx->p); - mpi_free(ctx->q); mpi_free(ctx->g); mpi_free(ctx->xa); memset(ctx, 0, sizeof(*ctx)); @@ -114,11 +112,12 @@ static int dh_set_secret(struct crypto_kpp *tfm, const void *buf, /* * SP800-56A public key verification: * - * * If Q is provided as part of the domain paramenters, a full validation - * according to SP800-56A section 5.6.2.3.1 is performed. + * * For safe-prime groups, Q can be computed trivially from P and a + * full validation according to SP800-56A section 5.6.2.3.1 is + * performed. * - * * If Q is not provided, a partial validation according to SP800-56A section - * 5.6.2.3.2 is performed. + * * For all other sets of group parameters, only a partial validation + * according to SP800-56A section 5.6.2.3.2 is performed. */ static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y) { @@ -129,21 +128,40 @@ static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y) * Step 1: Verify that 2 <= y <= p - 2. * * The upper limit check is actually y < p instead of y < p - 1 - * as the mpi_sub_ui function is yet missing. + * in order to save one mpi_sub_ui() invocation here. Note that + * p - 1 is the non-trivial element of the subgroup of order 2 and + * thus, the check on y^q below would fail if y == p - 1. */ if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0) return -EINVAL; - /* Step 2: Verify that 1 = y^q mod p */ - if (ctx->q) { - MPI val = mpi_alloc(0); + /* + * Step 2: Verify that 1 = y^q mod p + * + * For the safe-prime groups q = (p - 1)/2. + */ + if (ctx->group_id != DH_GROUP_ID_UNKNOWN) { + MPI val, q; int ret; + val = mpi_alloc(0); if (!val) return -ENOMEM; - ret = mpi_powm(val, y, ctx->q, ctx->p); + q = mpi_alloc(mpi_get_nlimbs(ctx->p)); + if (!q) { + mpi_free(val); + return -ENOMEM; + } + + /* + * ->p is odd, so no need to explicitly subtract one + * from it before shifting to the right. + */ + mpi_rshift(q, ctx->p, 1); + ret = mpi_powm(val, y, q, ctx->p); + mpi_free(q); if (ret) { mpi_free(val); return ret;