Week2 Day 4: K8s security — AppArmor

Thu, 21 May 2026 00:00:00 -0700

AppArmor as the path-based complement to seccomp’s syscall-based filtering — and a hands-on lesson in why that complement is harder to deploy. This post covers how K8s wraps AppArmor (securityContext.appArmorProfile, symmetric with seccomp’s three types), why an AppArmor profile is heavier than a seccomp one (it must be pre-loaded into the node’s kernel via apparmor_parser, not just dropped as a file), why deny /data/** w blocks every syscall that writes there (closing the hole where touch bypassed yesterday’s mkdir block), and the day’s most valuable lesson: the experiment couldn’t run at all because a Mac/Docker-Desktop kind node has no AppArmor LSM in its kernel — a firsthand encounter with the fail-open trap and the portability problem of AppArmor-based mitigations.

Day 5: AppArmor + layered sandbox design

Sat, 16 May 2026 00:00:00 -0700

How AppArmor actually attaches to a process (via the bprm_check_security LSM hook at execve time, keyed on binary path), why bash script.sh silently runs unconfined while ./script.sh does not, the six exec modifiers (ix/Px/Cx/Ux and their setuid-preserving uppercase forms), the hardlink and bind-mount tricks that bypass path-based MAC, and why a production sandbox layers namespace + capability + seccomp + AppArmor + cgroup — with the argument that, if you can only afford two, seccomp + AppArmor is the highest-ROI pair.

Lsm on Ethan-ZYF

Week2 Day 4: K8s security — AppArmor

Day 5: AppArmor + layered sandbox design