On Fri, Feb 28, 2025 at 9:09 AM Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote: > On Thu, 2025-02-27 at 17:22 -0500, Paul Moore wrote: > > > > I'd still also like to see some discussion about moving towards the > > addition of keyrings oriented towards usage instead of limiting > > ourselves to keyrings that are oriented on the source of the keys. > > Perhaps I'm missing some important detail which makes this > > impractical, but it seems like an obvious improvement to me and would > > go a long way towards solving some of the problems that we typically > > see with kernel keys. > > The proliferation of keyrings won't solve the key usage problem for IMA- > appraisal. IMA-appraisal can be used to verify the kexec image, kernel modules, > firwmare, etc, but it also verifies file signatures contained in userspace > packages. To be clear I don't think the usage oriented keyring idea will solve every keyring problem, but it seems like it solves a fair number of things that I've heard lately. > To support the latter case, keyrings would need to be application > specific. (This version of Clavis doesn't solve the latter key usage for IMA- > appraisal either.) Application specific keyrings are more-or-less what I've been trying to describe. > The keys baked into the kernel are trusted because the kernel itself was signed > and verified (secure boot). Anyone building a kernel can build a key into the > kernel image, which establishes a "root of trust". That key can then be used to > verify and load other keys onto the IMA keyring. Sure, I'm not saying that trust isn't important, and that there are varying levels of trust. My argument is that having additional, usage/application oriented keyrings which contain links back to keys imported and stored in the traditional trust oriented keyrings could neatly solve a number of keyring access control issues. > The problem is how to safely establish a root of trust without baking the key > into the kernel image and then limiting that trust to specific usages or > applications. My takeaway from Clavis was that it was more about establishing a set of access controls around keys already present in the keyrings and my comments about usage/spplication oriented keyrings have been in that context. While the access control policy, regardless of how it is implemented, should no doubt incorporate the trust placed in the individual keys, how that trust is established is a separate issue from access control as far as I'm concerned. -- paul-moore.com
