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Date: Fri, 3 Aug 2018 08:11:29 -0500 From: Seth Forshee <seth.forshee@...onical.com> To: Eric Richter <erichte@...ux.vnet.ibm.com> Cc: linux-integrity <linux-integrity@...r.kernel.org>, linux-security-module <linux-security-module@...r.kernel.org>, linux-efi <linux-efi@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, David Howells <dhowells@...hat.com>, Justin Forbes <jforbes@...hat.com> Subject: Re: [PATCH 3/4] ima: add support for KEXEC_ORIG_KERNEL_CHECK On Wed, Jul 25, 2018 at 06:31:59PM -0500, Eric Richter wrote: > IMA can verify the signature of kernel images loaded with kexec_file_load, > but can not verify images loaded with the regular kexec_load syscall. > Therefore, the appraisal will automatically fail during kexec_load when an > appraise policy rule is set for func=KEXEC_KERNEL_CHECK. This can be used > to effectively disable the kexec_load syscall, while still allowing the > kexec_file_load to operate so long as the target kernel image is signed. > > However, this conflicts with CONFIG_KEXEC_VERIFY_SIG. If that option is > enabled and there is an appraise rule set, then the target kernel would > have to be verifiable by both IMA and the architecture specific kernel > verification procedure. > > This patch adds a new func= for IMA appraisal specifically for the original > kexec_load syscall. Therefore, the kexec_load syscall can be effectively > disabled via IMA policy, leaving the kexec_file_load syscall able to do its > own signature verification, and not require it to be signed via IMA. To > retain compatibility, the existing func=KEXEC_KERNEL_CHECK flag is > unchanged, and thus enables appraisal for both kexec syscalls. This seems like a roundabout way to disallow the kexec_load syscall. Wouldn't it make more sense to simply disallow kexec_load any time CONFIG_KEXEC_VERIFY_SIG is enabled, since it effectively renders that option impotent? Or has that idea already been rejected? Thanks, Seth
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