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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2604C4332F for ; Tue, 8 Feb 2022 11:30:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229975AbiBHL3r (ORCPT ); Tue, 8 Feb 2022 06:29:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355553AbiBHJps (ORCPT ); Tue, 8 Feb 2022 04:45:48 -0500 Received: from out30-45.freemail.mail.aliyun.com (out30-45.freemail.mail.aliyun.com [115.124.30.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83BD7C03FEC0; Tue, 8 Feb 2022 01:45:46 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R371e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=tianjia.zhang@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0V3vxzfq_1644313541; Received: from 30.240.99.213(mailfrom:tianjia.zhang@linux.alibaba.com fp:SMTPD_---0V3vxzfq_1644313541) by smtp.aliyun-inc.com(127.0.0.1); Tue, 08 Feb 2022 17:45:42 +0800 Message-ID: <8ca7c447-3fd6-612b-f903-3111eaddf6e6@linux.alibaba.com> Date: Tue, 8 Feb 2022 17:45:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH] KEYS: asymmetric: enforce SM2 signature use pkey algo Content-Language: en-US To: Eric Biggers Cc: Mimi Zohar , Vitaly Chikunov , Stefan Berger , Jarkko Sakkinen , Gilad Ben-Yossef , David Howells , Herbert Xu , "David S. Miller" , keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org References: <20220201003414.55380-1-ebiggers@kernel.org> <20220207114327.7929-1-tianjia.zhang@linux.alibaba.com> From: Tianjia Zhang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org Hi Eric, On 2/8/22 1:35 PM, Eric Biggers wrote: > On Mon, Feb 07, 2022 at 07:43:27PM +0800, Tianjia Zhang wrote: >> The signature verification of SM2 needs to add the Za value and >> recalculate sig->digest, which requires the detection of the pkey_algo >> in public_key_verify_signature(). As Eric Biggers said, the pkey_algo >> field in sig is attacker-controlled and should be use pkey->pkey_algo >> instead of sig->pkey_algo, and secondly, if sig->pkey_algo is NULL, it >> will also cause signature verification failure. >> >> The software_key_determine_akcipher() already forces the algorithms >> are matched, so the SM3 algorithm is enforced in the SM2 signature, >> although this has been checked, we still avoid using any algorithm >> information in the signature as input. >> >> Reported-by: Eric Biggers >> Signed-off-by: Tianjia Zhang > > Can you add a Fixes tag? > Thanks, the v2 patch with Fixes tag added has been appended to your v2 series. >> --- >> crypto/asymmetric_keys/public_key.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c >> index a603ee8afdb8..ea9a5501f87e 100644 >> --- a/crypto/asymmetric_keys/public_key.c >> +++ b/crypto/asymmetric_keys/public_key.c >> @@ -309,7 +309,8 @@ static int cert_sig_digest_update(const struct public_key_signature *sig, >> if (ret) >> return ret; >> >> - tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); >> + /* SM2 signatures always use the SM3 hash algorithm */ >> + tfm = crypto_alloc_shash("sm3", 0, 0); >> if (IS_ERR(tfm)) >> return PTR_ERR(tfm); >> >> @@ -414,8 +415,7 @@ int public_key_verify_signature(const struct public_key *pkey, >> if (ret) >> goto error_free_key; >> >> - if (sig->pkey_algo && strcmp(sig->pkey_algo, "sm2") == 0 && >> - sig->data_size) { >> + if (strcmp(pkey->pkey_algo, "sm2") == 0 && sig->data_size) { >> ret = cert_sig_digest_update(sig, tfm); >> if (ret) >> goto error_free_key; >> -- > > This is an improvement, but do you also have a plan to address the problem where > the code allows the "Za" hash step to be skipped? The definitions of SM2 that I > could find require that step. So, it is unclear that the algorithm with that > step skipped is still SM2, and how its security relates to that of the SM2 > algorithm as actually defined. > > - Eric The design of this Za has indeed brought us a lot of trouble, which makes the two separate steps of calculating the hash and signature forced to be coupled together. At present, it is a better way to design skipping Za as an option. I will try to do this, which of course also includes application layer libraries, like openssl. Best regards, Tianjia