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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 083BDC433DF for ; Wed, 3 Jun 2020 09:57:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C3FA72074B for ; Wed, 3 Jun 2020 09:57:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VSnmAG4p" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726315AbgFCJ5H (ORCPT ); Wed, 3 Jun 2020 05:57:07 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:34300 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725854AbgFCJ5G (ORCPT ); Wed, 3 Jun 2020 05:57:06 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591178225; 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=4MA6Azc4ArSFQSxrgXC2tTu2QvV0djuoR5kPx8BJBBc=; b=VSnmAG4ps6GmRV093OTucHQpKFptaMzORGAwMh/1B1osBNFmbA6PFSNVspCNsqScDjpS0q rbDgdnqe5K256T3SL16DgL43E99znGphtQXPsks/EkFsMNLOeqlf0EflUTkTvqp+jBOLMc pvkctVC5lIFT8bxX1O3OpK+rPbwRCDE= 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-232-DjnYCkpwPTyZ2R-wCsIHVQ-1; Wed, 03 Jun 2020 05:57:01 -0400 X-MC-Unique: DjnYCkpwPTyZ2R-wCsIHVQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E67491009600; Wed, 3 Jun 2020 09:56:58 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-13-100.pek2.redhat.com [10.72.13.100]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1AB0D60BE1; Wed, 3 Jun 2020 09:56:53 +0000 (UTC) Date: Wed, 3 Jun 2020 17:56:50 +0800 From: Dave Young To: Lianbo Jiang Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, akpm@linux-foundation.org, ebiederm@xmission.com, jbohac@suse.cz, jmorris@namei.org, mjg59@google.com, bhe@redhat.com Subject: Re: [PATCH v2] kexec: Do not verify the signature without the lockdown or mandatory signature Message-ID: <20200603095650.GA4078@dhcp-128-65.nay.redhat.com> References: <20200602045952.27487-1-lijiang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200602045952.27487-1-lijiang@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/02/20 at 12:59pm, Lianbo Jiang wrote: > Signature verification is an important security feature, to protect > system from being attacked with a kernel of unknown origin. Kexec > rebooting is a way to replace the running kernel, hence need be > secured carefully. > > In the current code of handling signature verification of kexec kernel, > the logic is very twisted. It mixes signature verification, IMA signature > appraising and kexec lockdown. > > If there is no KEXEC_SIG_FORCE, kexec kernel image doesn't have one of > signature, the supported crypto, and key, we don't think this is wrong, > Unless kexec lockdown is executed. IMA is considered as another kind of > signature appraising method. > > If kexec kernel image has signature/crypto/key, it has to go through the > signature verification and pass. Otherwise it's seen as verification > failure, and won't be loaded. > > Seems kexec kernel image with an unqualified signature is even worse than > those w/o signature at all, this sounds very unreasonable. E.g. If people > get a unsigned kernel to load, or a kernel signed with expired key, which > one is more dangerous? > > So, here, let's simplify the logic to improve code readability. If the > KEXEC_SIG_FORCE enabled or kexec lockdown enabled, signature verification > is mandated. Otherwise, we lift the bar for any kernel image. > > Signed-off-by: Lianbo Jiang > --- > Changes since v1: > [1] Modify the log level(suggested by Jiri Bohac) > > kernel/kexec_file.c | 34 ++++++---------------------------- > 1 file changed, 6 insertions(+), 28 deletions(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index faa74d5f6941..fae496958a68 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -181,34 +181,19 @@ void kimage_file_post_load_cleanup(struct kimage *image) > static int > kimage_validate_signature(struct kimage *image) > { > - const char *reason; > int ret; > > ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf, > image->kernel_buf_len); > - switch (ret) { > - case 0: > - break; > + if (ret) { > > - /* Certain verification errors are non-fatal if we're not > - * checking errors, provided we aren't mandating that there > - * must be a valid signature. > - */ > - case -ENODATA: > - reason = "kexec of unsigned image"; > - goto decide; > - case -ENOPKG: > - reason = "kexec of image with unsupported crypto"; > - goto decide; > - case -ENOKEY: > - reason = "kexec of image with unavailable key"; > - decide: > if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) { > - pr_notice("%s rejected\n", reason); > + pr_notice("Enforced kernel signature verification failed (%d).\n", ret); > return ret; > } > > - /* If IMA is guaranteed to appraise a signature on the kexec > + /* > + * If IMA is guaranteed to appraise a signature on the kexec > * image, permit it even if the kernel is otherwise locked > * down. > */ > @@ -216,17 +201,10 @@ kimage_validate_signature(struct kimage *image) > security_locked_down(LOCKDOWN_KEXEC)) > return -EPERM; > > - return 0; > - > - /* All other errors are fatal, including nomem, unparseable > - * signatures and signature check failures - even if signatures > - * aren't required. > - */ > - default: > - pr_notice("kernel signature verification failed (%d).\n", ret); > + pr_debug("kernel signature verification failed (%d).\n", ret); > } > > - return ret; > + return 0; > } > #endif > > -- > 2.17.1 > Acked-by: Dave Young Thanks Dave From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-1.mimecast.com ([205.139.110.61] helo=us-smtp-delivery-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgQ8w-00034m-25 for kexec@lists.infradead.org; Wed, 03 Jun 2020 09:57:08 +0000 Date: Wed, 3 Jun 2020 17:56:50 +0800 From: Dave Young Subject: Re: [PATCH v2] kexec: Do not verify the signature without the lockdown or mandatory signature Message-ID: <20200603095650.GA4078@dhcp-128-65.nay.redhat.com> References: <20200602045952.27487-1-lijiang@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200602045952.27487-1-lijiang@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Lianbo Jiang Cc: jbohac@suse.cz, bhe@redhat.com, kexec@lists.infradead.org, jmorris@namei.org, mjg59@google.com, linux-kernel@vger.kernel.org, ebiederm@xmission.com, akpm@linux-foundation.org On 06/02/20 at 12:59pm, Lianbo Jiang wrote: > Signature verification is an important security feature, to protect > system from being attacked with a kernel of unknown origin. Kexec > rebooting is a way to replace the running kernel, hence need be > secured carefully. > > In the current code of handling signature verification of kexec kernel, > the logic is very twisted. It mixes signature verification, IMA signature > appraising and kexec lockdown. > > If there is no KEXEC_SIG_FORCE, kexec kernel image doesn't have one of > signature, the supported crypto, and key, we don't think this is wrong, > Unless kexec lockdown is executed. IMA is considered as another kind of > signature appraising method. > > If kexec kernel image has signature/crypto/key, it has to go through the > signature verification and pass. Otherwise it's seen as verification > failure, and won't be loaded. > > Seems kexec kernel image with an unqualified signature is even worse than > those w/o signature at all, this sounds very unreasonable. E.g. If people > get a unsigned kernel to load, or a kernel signed with expired key, which > one is more dangerous? > > So, here, let's simplify the logic to improve code readability. If the > KEXEC_SIG_FORCE enabled or kexec lockdown enabled, signature verification > is mandated. Otherwise, we lift the bar for any kernel image. > > Signed-off-by: Lianbo Jiang > --- > Changes since v1: > [1] Modify the log level(suggested by Jiri Bohac) > > kernel/kexec_file.c | 34 ++++++---------------------------- > 1 file changed, 6 insertions(+), 28 deletions(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index faa74d5f6941..fae496958a68 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -181,34 +181,19 @@ void kimage_file_post_load_cleanup(struct kimage *image) > static int > kimage_validate_signature(struct kimage *image) > { > - const char *reason; > int ret; > > ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf, > image->kernel_buf_len); > - switch (ret) { > - case 0: > - break; > + if (ret) { > > - /* Certain verification errors are non-fatal if we're not > - * checking errors, provided we aren't mandating that there > - * must be a valid signature. > - */ > - case -ENODATA: > - reason = "kexec of unsigned image"; > - goto decide; > - case -ENOPKG: > - reason = "kexec of image with unsupported crypto"; > - goto decide; > - case -ENOKEY: > - reason = "kexec of image with unavailable key"; > - decide: > if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) { > - pr_notice("%s rejected\n", reason); > + pr_notice("Enforced kernel signature verification failed (%d).\n", ret); > return ret; > } > > - /* If IMA is guaranteed to appraise a signature on the kexec > + /* > + * If IMA is guaranteed to appraise a signature on the kexec > * image, permit it even if the kernel is otherwise locked > * down. > */ > @@ -216,17 +201,10 @@ kimage_validate_signature(struct kimage *image) > security_locked_down(LOCKDOWN_KEXEC)) > return -EPERM; > > - return 0; > - > - /* All other errors are fatal, including nomem, unparseable > - * signatures and signature check failures - even if signatures > - * aren't required. > - */ > - default: > - pr_notice("kernel signature verification failed (%d).\n", ret); > + pr_debug("kernel signature verification failed (%d).\n", ret); > } > > - return ret; > + return 0; > } > #endif > > -- > 2.17.1 > Acked-by: Dave Young Thanks Dave _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec