From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751856AbdJZHm6 (ORCPT ); Thu, 26 Oct 2017 03:42:58 -0400 Received: from smtp.nue.novell.com ([195.135.221.5]:49158 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751001AbdJZHmz (ORCPT ); Thu, 26 Oct 2017 03:42:55 -0400 Date: Thu, 26 Oct 2017 15:42:43 +0800 From: joeyli To: Mimi Zohar Cc: David Howells , linux-security-module@vger.kernel.org, gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org, matthew.garrett@nebula.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, jforbes@redhat.com Subject: Re: [PATCH 07/27] kexec_file: Disable at runtime if securelevel has been set Message-ID: <20171026074243.GM8550@linux-l9pv.suse> References: <150842463163.7923.11081723749106843698.stgit@warthog.procyon.org.uk> <150842468754.7923.10037578333644594134.stgit@warthog.procyon.org.uk> <1508774083.3639.124.camel@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1508774083.3639.124.camel@linux.vnet.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mimi, Thank you for reviewing. On Mon, Oct 23, 2017 at 11:54:43AM -0400, Mimi Zohar wrote: > On Thu, 2017-10-19 at 15:51 +0100, David Howells wrote: > > From: Chun-Yi Lee > > > > When KEXEC_VERIFY_SIG is not enabled, kernel should not loads image > > through kexec_file systemcall if securelevel has been set. > > The patch title and description needs to be updated to refer to > lockdown, not securelevel. > > As previously mentioned the last time these patches were posted, this > leaves out testing to see if the integrity subsystem is enabled. > > Commit 503ceaef8e2e "ima: define a set of appraisal rules requiring > file signatures" was upstreamed.  An additional patch could force > these rules to be added to the custom policy, if lockdown is enabled. >  This and other patches in this series could then check to see if > is_ima_appraise_enabled() is true. > > Mimi > I have updated the patch title and description, and I also added is_ima_appraise_enabled() as the following. Is it good to you? On the other hand, I am not good on IMA. I have traced the code path in kimage_file_prepare_segments(). Looks that the READING_KEXEC_IMAGE doesn't show in selinux_kernel_read_file(). Where is the exact code in IMA for checking the signature when loading crash kernel file? Thanks a lot! Joey Lee --- >>From 274a2125132ba5aff49e4ccd167f52982732361f Mon Sep 17 00:00:00 2001 From: "Lee, Chun-Yi" Date: Thu, 26 Oct 2017 15:24:50 +0800 Subject: [PATCH] kexec_file: The integrity must be checked when the kernel is locked down When KEXEC_VERIFY_SIG and IMA appraise are not enabled, kernel should not allow that the image to be loaded by kexec_file systemcall when the kernel is locked down. The original code was showed in Matthew's patch but not in the later patch set: https://lkml.org/lkml/2015/3/13/778 Signed-off-by: "Lee, Chun-Yi" --- kernel/kexec_file.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 9f48f44..b6dc218 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -255,6 +255,14 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; + /* Don't permit images to be loaded into trusted kernels if we're not + * going to check the integrity on them + */ + if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) && + !is_ima_appraise_enabled() && + kernel_is_locked_down("kexec of unsigned images")) + return -EPERM; + /* Make sure we have a legal set of flags */ if (flags != (flags & KEXEC_FILE_FLAGS)) return -EINVAL; -- 2.6.2