Root cause of the blank chrony fields (found on comet-beacon-54): chrony 4.x
(RHEL 9) defaults its command interface to the UNIX socket only
(/run/chrony/chronyd.sock), usable by root or the chrony group with a writable
/run/chrony. The fleet-agent unit is hardened — DynamicUser (group tss, not
chrony) + ProtectSystem=strict (/run read-only) — so it cannot open the unix
socket nor create chronyc's reply socket. Bench proof: normal-user 'chronyc
tracking' -> 506 Cannot talk to daemon; only sudo worked; 'chronyc -h 127.0.0.1'
failed and ss showed no UDP :323. So the probe always failed and every chrony_*
field stayed empty. SELinux permissive did NOT help — it was never (only) an
SELinux problem; the nnp_transition module (prev commit) is still needed for the
enforcing exec transition.
Fix: bind chronyd's command socket on 127.0.0.1 (bindcmdaddress in chrony.conf,
idempotent in the 2c provisioner) and point the probe at it (chronyc -n -h
127.0.0.1 tracking). UDP needs no fs write or group and rides the unit's
already-allowed AF_INET. Loopback + monitoring-only (state changes still need the
root unix socket), so exposure is minimal. Rejected the unix-socket route (chrony
group + ReadWritePaths=/run/chrony) because /run/chrony is 0750 (group has no
write). Documented in docs/stig-deviations.md #17; .te bench note updated for the
enforcing UDP path. Needs a workstation image rebuild + reboot.
fleet-agent reports clock health via 'chronyc -n tracking', but the hardened
unit runs with NoNewPrivileges (explicit + forced by DynamicUser/SystemCallFilter/
MemoryDenyWriteExecute). SELinux transitions the exec'd chronyc into chronyc_t,
and NNP forbids that domain change without process2:nnp_transition — which the
base policy doesn't grant for unconfined_service_t -> chronyc_t. Under enforcing
the exec is denied (avc: denied { nnp_transition } comm=fleet-agent, seen on
comet-beacon-54), so chronyc never runs and every chrony_* health field stays
empty (Monitor chrony row shows '—'). uptime/cpu/mem are unaffected (no exec).
Ship a minimal local module (files/stig/fleet-agent-chronyc.te) granting only
that one nnp_transition to the MORE-confined chronyc_t domain — the safe
direction the permission exists to gate — loosening nothing else in the agent
sandbox. Built + semodule -i'd in 2c-STIG alongside the existing
chrony_dhcp_dispatcher / fapolicyd_tmpfs modules. Justified in
docs/stig-deviations.md #16. Needs a workstation image rebuild + reboot; same
policy-store-rebuild reproducibility re-check as #14/#15.
Audiobuzz