> On Aug 23, 2021, at 11:35 AM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > > On Thu, 2021-08-19 at 09:10 -0400, Mimi Zohar wrote: >> On Thu, 2021-08-19 at 14:38 +0300, Jarkko Sakkinen wrote: >>> On Wed, 2021-08-18 at 20:20 -0400, Eric Snowberg wrote: >>>> Many UEFI Linux distributions boot using shim. The UEFI shim provides >>>> what is called Machine Owner Keys (MOK). Shim uses both the UEFI Secure >>>> Boot DB and MOK keys to validate the next step in the boot chain. The >>>> MOK facility can be used to import user generated keys. These keys can >>>> be used to sign an end-user development kernel build. When Linux boots, >>>> pre-boot keys (both UEFI Secure Boot DB and MOK keys) get loaded in the >>>> Linux .platform keyring. >>>> >>>> Currently, pre-boot keys are not trusted within the Linux trust boundary >>>> [1]. These platform keys can only be used for kexec. If an end-user >>>> wants to use their own key within the Linux trust boundary, they must >>>> either compile it into the kernel themselves or use the insert-sys-cert >>>> script. Both options present a problem. Many end-users do not want to >>>> compile their own kernels. With the insert-sys-cert option, there are >>>> missing upstream changes [2]. Also, with the insert-sys-cert option, >>>> the end-user must re-sign their kernel again with their own key, and >>>> then insert that key into the MOK db. Another problem with >>>> insert-sys-cert is that only a single key can be inserted into a >>>> compressed kernel. >>>> >>>> Having the ability to insert a key into the Linux trust boundary opens >>>> up various possibilities. The end-user can use a pre-built kernel and >>>> sign their own kernel modules. It also opens up the ability for an >>>> end-user to more easily use digital signature based IMA-appraisal. To >>>> get a key into the ima keyring, it must be signed by a key within the >>>> Linux trust boundary. >>> >>> As of today, I can use a prebuilt kernel, crate my own MOK key and sign >>> modules. What will be different? >> >> The UEFI db and MOK keys are being loaded onto the .platform keyring, >> which is suppose to be limited to verifying the kexec kernel image >> signature. With a downstream patch, kernel modules are being verified >> as well. >> >> Initially Patrick Uiterwijk's "[PATCH 0/3] Load keys from TPM2 NV Index >> on IMA keyring" patch set attempted to define a new root of trust based >> on a key stored in the TPM. This patch set is similarly attempting to >> define a new root of trust based on CA keys stored in the MOK db. >> >> The purpose of this patch set is to define a new, safe trust source >> parallel to the builtin keyring, without relying on a downstream patch. >> With the new root of trust, the end user could sign his own kernel >> modules, sign third party keys, and load keys onto the IMA keyring, >> which can be used for signing the IMA policy and other files. > > I can, as of today, generate my own mok key and sign my LKM's, and > kernel will verify my LKM's. > > What is different? Are you sure your kernel doesn’t contain some version of the rejected patch referenced in the cover letter [1]? https://lore.kernel.org/lkml/1556221605.24945.3.camel@xxxxxxxxxxxxxxxxxxxxx/
