From patchwork Mon Mar 21 07:47:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Guozihua (Scott)" X-Patchwork-Id: 12786952 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 78A06C433EF for ; Mon, 21 Mar 2022 07:48:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345024AbiCUHtq (ORCPT ); Mon, 21 Mar 2022 03:49:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344050AbiCUHtl (ORCPT ); Mon, 21 Mar 2022 03:49:41 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBE7DD7F; Mon, 21 Mar 2022 00:48:15 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KMRYh3Djqz1GBxf; Mon, 21 Mar 2022 15:48:08 +0800 (CST) Received: from huawei.com (10.67.175.31) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 21 Mar 2022 15:48:13 +0800 From: GUO Zihua To: CC: , , , , , , Subject: [PATCH] ima: remove template "ima" as the compiled default Date: Mon, 21 Mar 2022 15:47:37 +0800 Message-ID: <20220321074737.138002-1-guozihua@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 X-Originating-IP: [10.67.175.31] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500024.china.huawei.com (7.185.36.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org Template "ima" is a legacy template which limits the hash algorithm to either sha1 or md5. None of them should be considered "strong" these days. Besides, allowing template "ima" as the compiled default would also cause the following issue: the cmdline option "ima_hash=" must be behind "ima_template=", otherwise "ima_hash=" might be rejected. The root cause of this issue is that during the processing of ima_hash, we would try to check whether the hash algorithm is compatible with the template. If the template is not set at the moment we do the check, we check the algorithm against the compiled default template. If the complied default template is "ima", then we reject any hash algorithm other than sha1 and md5. For example, if the compiled default template is "ima", and the default algorithm is sha1 (which is the current default). In the cmdline, we put in "ima_hash=sha256 ima_template=ima-ng". The expected behavior would be that ima starts with ima-ng as the template and sha256 as the hash algorithm. However, during the processing of "ima_hash=", "ima_template=" has not been processed yet, and hash_setup would check the configured hash algorithm against the compiled default: ima, and reject sha256. So at the end, the hash algorithm that is actually used will be sha1. With template "ima" removed from the compiled default, we ensure that the default tempalte would at least be "ima-ng" which allows for basically any hash algorithm. This change would not break the algorithm compatibility checking for IMA. Fixes: 4286587dccd43 ("ima: add Kconfig default measurement list template") Signed-off-by: GUO Zihua --- security/integrity/ima/Kconfig | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig index f3a9cc201c8c..9513df2ac19e 100644 --- a/security/integrity/ima/Kconfig +++ b/security/integrity/ima/Kconfig @@ -65,14 +65,11 @@ choice help Select the default IMA measurement template. - The original 'ima' measurement list template contains a - hash, defined as 20 bytes, and a null terminated pathname, - limited to 255 characters. The 'ima-ng' measurement list - template permits both larger hash digests and longer - pathnames. - - config IMA_TEMPLATE - bool "ima" + The 'ima-ng' measurement list template permits various hash + digests and long pathnames. The compiled default template + can be overwritten using the kernel command line + 'ima_template=' option. + config IMA_NG_TEMPLATE bool "ima-ng (default)" config IMA_SIG_TEMPLATE @@ -82,7 +79,6 @@ endchoice config IMA_DEFAULT_TEMPLATE string depends on IMA - default "ima" if IMA_TEMPLATE default "ima-ng" if IMA_NG_TEMPLATE default "ima-sig" if IMA_SIG_TEMPLATE