I'd like to see a formal container security grade that works like:
1) Curate a list of all known (container) exploits
2) Run each exploit in environments of increasing security like permissions-based, jail, Docker and emulator
3) The percentage of prevented exploits would be the score from 0-100%
Under this scheme, I'd expect naive attempts at containerization with permissions and jails to score around 0%, while Docker might be above 50% and Microsandbox could potentially reach 100%.This might satisfy some of our intuition around questions like "why not just use a jail?". Also the containers could run on a site on the open web as honeypots with cash or crypto prizes for pwning them to "prove" which containers achieve 100%.
We might also need to redefine what "secure" means, since exploits like Rowhammer and Spectre may make nearly all conventional and cloud computing insecure. Or maybe it's a moving target, like how 64 bit encryption might have once been considered secure but now we need 128 bit or higher.
Edit: the motivation behind this would be to find a container that's 100% secure without emulation, for performance and cost-savings benefits, as well as gaining insights into how to secure operating systems by containerizing their various services.
I think it's generally understood that any sort of kernel LPE can potentially (and therefore is generally considered to) lead to breaking all security boundaries on the local machine, since the kernel contains no internal security boundaries. That includes both containers, but also everything else such a user separation, hardware virtualization controlled by the local kernel, and kernel private secrets.