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 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
