From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3148351-1525383089-2-6160319295745698418 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-charsets: plain='UTF-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: linux@kroah.com X-Delivered-to: linux@kroah.com X-Mail-from: linux-security-module-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1525383088; b=gFMmgXL6geGlWC9i96JF6jOUeD0xPudI+CC4CPr5q2OIYU2Jrw 8xLWbrWxCPtIRDylUdJojb+hRxaUTblK/J4hGSrwGq4Q83B+djJuiYpTCfLJjHQW hPfc9/UQG9aUFLogNQsaBeIRAmh9g5fokzvoOEuxHwA4GHYwXbmy9phyfxpDCYw2 6TrE8+PqIi/nb7kctTPWzkYemv+RoKGjd+i6wX4MfjPgSUhTdXrwItFO6nq8askT IYOHJwFiChhLkNEO2w/yYMMPTwFofGkRc2lbLMRRhWNglkJ5wlh6iSEJ8JBP+RzJ sW/JWfBwiqKA5iOrjv/Am+gFqnEpOvJIA9AQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=subject:from:to:cc:date:in-reply-to :references:content-type:mime-version:content-transfer-encoding :message-id:sender:list-id; s=fm2; t=1525383088; bh=PmoBgKnGr7t2 kEvUK8d2S97BRZH3XgiCkgyRf3BdMBo=; b=UO7LR3Qct/MSu3vz1xlvUeJsFGST nXQ8dnnE0ZUnA49Y6P7lD9JoTLc31AtI5gWw2Z4rAT9ruQX7dzlYpk1EVzDaPLDX x85ieClVhQ5iC4CNqtuDAYNgdHryNikgixBAk12Qw9ldLctkt+X6VWTfW93nBbBk b/L+7us5UWiFqJgSXIm3bbyRRRAAhpp7WVZBV+I3/qyjOmxGdeUNEf7eOPXfRSBu ELsqMTG6zreDB5xm4rAOnjxoYy3e/HlZ8Ygy/E9+8xPNpa3x5AZ3e+iXqsiJg6K7 6NZ13z+Ui18iUdu+ZVoXoal3oXTgLjahVHdZuLWgSlPu6L29DKF7JB1DmQ== ARC-Authentication-Results: i=1; mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=linux.vnet.ibm.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-security-module-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linux.vnet.ibm.com header.result=pass header_org.domain=ibm.com header_org.result=pass header_is_org_domain=no; x-vs=clean score=-100 state=0 Authentication-Results: mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=linux.vnet.ibm.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-security-module-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linux.vnet.ibm.com header.result=pass header_org.domain=ibm.com header_org.result=pass header_is_org_domain=no; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfOdLsizidlJGgRvenH+e0HGsTGQTiuA51loK8grXnm06VuWBeA6nus6gBZQfZRb60tsMKuvvYiY1fTmRnlr46b6yPANiPnRXy10TXJBkZa93r/yjXBIw 88EiVQEveaY172QSTQjTMqZQm0+TQnKdBhKD5bnsdNLUK2+MPL+8SwIIlEJFunIqc39npQjh4H/LyjUonjEXdYtG2KsgzAvkNLOckdU0e8umimXs2zdJ0ygA oUjqsW3Z+EPAd4eB+gCFhg== X-CM-Analysis: v=2.3 cv=E8HjW5Vl c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=IkcTkHD0fZMA:10 a=VUJBJC2UJ8kA:10 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=bHLSQKsBI4kpnCWO79EA:9 a=GQnX5GE6Xc20WrQG:21 a=EkvNLplSnOF7QWIh:21 a=QEXdDO2ut3YA:10 a=x8gzFH9gYPwA:10 a=AjGcO6oz07-iQ99wixmX:22 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751186AbeECVbZ (ORCPT ); Thu, 3 May 2018 17:31:25 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36922 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751132AbeECVbY (ORCPT ); Thu, 3 May 2018 17:31:24 -0400 Subject: Re: [PATCH 0/3] kexec: limit kexec_load syscall From: Mimi Zohar To: "Eric W. Biederman" , Kees Cook Cc: David Howells , Matthew Garrett , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Date: Thu, 03 May 2018 17:31:15 -0400 In-Reply-To: <87r2mso5up.fsf@xmission.com> References: <1523572911-16363-1-git-send-email-zohar@linux.vnet.ibm.com> <87r2mso5up.fsf@xmission.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 18050321-0012-0000-0000-000005D1B510 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18050321-0013-0000-0000-0000194EDE66 Message-Id: <1525383075.3539.67.camel@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-03_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805030185 Sender: owner-linux-security-module@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: [Cc'ing Kees and kernel-hardening] On Thu, 2018-05-03 at 15:13 -0500, Eric W. Biederman wrote: > Mimi Zohar writes: > > > In environments that require the kexec kernel image to be signed, prevent > > using the kexec_load syscall. In order for LSMs and IMA to differentiate > > between kexec_load and kexec_file_load syscalls, this patch set adds a > > call to security_kernel_read_file() in kexec_load_check(). > > Having thought about it some more this justification for these changes > does not work. The functionality of kexec_load is already root-only. > So in environments that require the kernel image to be signed just don't > use kexec_load. Possibly even compile kexec_load out to save space > because you will never need it. You don't need a new security hook to > do any of that. Userspace is a very fine mechanism for being the > instrument of policy. True, for those building their own kernel, they can disable the old syscalls.  The concern is not for those building their own kernels, but for those using stock kernels.   By adding an LSM hook here in the kexec_load syscall, as opposed to an IMA specific hook, other LSMs can piggy back on top of it.  Currently, both load_pin and SELinux are gating the kernel module syscalls based on security_kernel_read_file. If there was a similar option for the kernel image, I'm pretty sure other LSMs would use it. >>From an IMA perspective, there needs to be some method for only allowing signed code to be loaded, executed, etc. - kernel modules, kernel image/initramfs, firmware, policies. > If you don't trust userspace that needs to be spelled out very clearly. > You need to talk about what your threat models are. > > If the only justification is so that that we can't boot windows if > someone hacks into userspace it has my nack because that is another kind > of complete non-sense. The usecase is the ability to gate the kexec_load usage in stock kernels. > > Given that you are not trusting userspace this changeset also probably > needs to have the kernel-hardening list cc'd. Because the only possible > justification I can imagine for something like this is kernel-hardening. Sure, Cc'ing linux-hardening and Kees. Mimi