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Fri, 14 May 2021 18:26:26 +0000 (GMT) Received: from demeter.local (unknown [9.160.6.19]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTPS; Fri, 14 May 2021 18:26:26 +0000 (GMT) Subject: Re: Security Working Group - Wednesday May 12 - results To: Patrick Williams References: <35156c27-e195-c238-1bb9-d20a30db3c63@linux.ibm.com> <8febdc9d-08bb-4094-9cad-7e6035c5bd71@linux.ibm.com> From: Joseph Reynolds Message-ID: Date: Fri, 14 May 2021 13:26:25 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-GUID: hHrr0VrieOduZ-iqonV4-a9ThhDE-wgY X-Proofpoint-ORIG-GUID: hHrr0VrieOduZ-iqonV4-a9ThhDE-wgY Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-05-14_08:2021-05-12, 2021-05-14 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 suspectscore=0 spamscore=0 lowpriorityscore=0 malwarescore=0 adultscore=0 impostorscore=0 mlxlogscore=999 mlxscore=0 priorityscore=1501 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105140142 X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: openbmc@lists.ozlabs.org Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" On 5/12/21 3:40 PM, Patrick Williams wrote: > On Wed, May 12, 2021 at 01:18:48PM -0500, Joseph Reynolds wrote: >> On 5/11/21 8:59 PM, Joseph Reynolds wrote: > [ Copying some stuff from the Google Doc. ] > >> Security impacts: >> - Can be used to defeat secureboot. >> - Can this function be disabled?  Via kernel config.  Default? >> - Can restrict which images kexec can load? >> - Recommend?  Validate the kernel signature before kexec’ing it.  But that doesn't stop an attacker who uses wget to get a malicious image which they pass to kexec. >> - Why would an attacker want to use kexec?  Opportunity to modify BMC code, load device drivers, create trojan horse(?) or back doors. >> - How can we force kexec to perform the same signature validation as uboot?  (each part and the whole: kernel, device tree, file system, …) > Some of this is a concern only because the arm32 support for kexec is > far behind the other architectures. Can someone investigate what, if > anything, is going on upstream to get arm caught up? > > On most other architectures there is a new set of system calls, enabled > by KEXEC_FILE, which moves some of the handling done by the kexec > executable into the kernel and has signature verification done there. > arm32 is one of the few architectures that do not currently support this > KConfig. > > See: > - https://man7.org/linux/man-pages/man8/kexec.8.html (kexec-syscall-auto). > - http://people.redhat.com/vgoyal/papers-presentations/linux-plumbers-2013/vivek-linux-plumbers-conference-2013-presentation-kexec-secureboot.pdf > Patrick, Thanks for the info!  (I'm learning as I go.)  I'll ask my people to look into this (with no promises). - Joseph