Second bench defect after removing the distro 20-chrony-dhcp clobberer
(secure-ntp-5a3eaed, comet-beacon-54): the dispatcher wrote the correct
`server ntp.fleet.lab iburst nts` line, but chrony loaded ZERO sources --
`chronyc reload sources` returned 200 OK yet authdata/sources stayed empty.
Root cause (AVC): chronyd_t was DENIED read on the .sources files because they and
/run/chrony-dhcp itself were labeled generic var_run_t; chronyd_t may only read its
own chronyd_var_run_t. The dispatcher's `mkdir -p` creates the dir as var_run_t and
files inherit it. The distro 20-chrony-dhcp we removed had been restorecon-ing them
to the readable label, so removing it exposed a latent labelling gap.
Stock RHEL policy already maps /run/chrony-dhcp -> chronyd_var_run_t (a restorecon
relabels it and chrony immediately reaches NTS Cook 8). Fix: ship
/etc/tmpfiles.d/chrony-dhcp.conf so systemd-tmpfiles pre-creates the dir with that
fcontext at sysinit, before any NM event -- the dispatcher's files then inherit
chronyd_var_run_t and chronyd can read them. No SELinux allow rules needed
(bench-verified: after the fix a real NM event wrote the source as chronyd_var_run_t,
no AVC, authdata -> NTS Cook 8). Applies in both secure_ntp modes.
Also: the dispatcher now skips `lo` -- it was writing a spurious lo.sources
duplicate of the same server (the distro script had skipped loopback).
BENCH-VERIFY on the next clean build: a normal boot leaves the source file labeled
chronyd_var_run_t (ls -Z), no lo.sources, and authdata reaches NTS/cookies>0 with no
manual step.
NTS was inactive on the clean-build deploy (secure-ntp-d1621e9, comet-beacon-54):
chronyc authdata showed a plain IP source in Mode '-', Cook 0, with no NTS-KE
attempt at all -- chrony was on plain NTP.
Root cause: NetworkManager runs dispatcher scripts from BOTH
/etc/NetworkManager/dispatcher.d and /usr/lib/NetworkManager/dispatcher.d, merged
and sorted by filename. The chrony RPM ships
/usr/lib/NetworkManager/dispatcher.d/20-chrony-dhcp, which writes the DHCP
option-42 server to the SAME /run/chrony-dhcp/<iface>.sources file our
10-chrony-dhcp-ntp uses. Sorting after 10-, it ran last and overwrote our
`server ntp.fleet.lab iburst nts` line with `server 192.168.50.10 iburst`, then
reloaded chrony -- last writer wins on the shared filename, silently defeating
authenticated time.
Isolation proof: removing the distro script + hand-writing the NTS source brought
NTS up immediately (ntp.fleet.lab NTS, Cook 8, zero NAKs), confirming the host
image, the fleet-signed NTS-KE cert, DNS, and tcp/4460 were all already correct --
the collision was the sole defect.
Fix: the provisioner removes /usr/lib/NetworkManager/dispatcher.d/20-chrony-dhcp
at build (our dispatcher supersedes it in both modes); 20-chrony-onoffline is left
in place (harmless). Documents the finding in the dispatcher header,
docs/secure-ntp-design.md, and the CLAUDE.md secure_ntp note. BENCH-VERIFY on the
next clean build: a normal boot reaches NTS/cookies>0 with no manual step.
NTS proven end-to-end on comet-beacon-54 (chronyc authdata cookies > 0); these
close the gaps the bench found so a clean build/serving run reaches that state
without manual patching:
- dispatcher (10-chrony-dhcp-ntp): fall back to resolv.conf search/domain when NM
doesn't export DHCP4_DOMAIN_NAME on the firing event, so the NTS source is
written reliably at boot (tonight it needed a manual dispatcher run).
- STIG vs secure_ntp (P2, security): STIG's chronyd_specify_remote_server re-injects
an UNAUTHENTICATED 'server 0.us.pool.ntp.mil maxpoll 16' AFTER the secure_ntp
chrony step commented servers out -> a silent fallback that defeats NTS's
DoS-only guarantee (host not fail-closed). Unselect chronyd_specify_remote_server
+ chronyd_or_ntpd_set_maxpoll in diskless-tailoring.xml, and re-strip any
server/pool in 2c-STIG-postfix when secure_ntp=true. Documented: stig-deviations #17.
- nts-cert.sh (P3): the container's chrony user (non-root) can't read a 0640
host-owned key -> NTS-KE TLS aborts ('non-properly terminated'). chown the key to
the ntp container's chrony uid + keep 0640 (0644 works but chrony warns
world-readable); 0644 fallback if the uid can't be found.
Bench-verified 2026-07-11; docs updated in docs/ssh-host-certificate-design.md's
sibling secure-ntp-design.md flow. F-03/P-18 stays open until a clean build shows
chrony.conf has no plain server and authdata cookies>0 as the only source.
Audiobuzz