secure-ntp: label /run/chrony-dhcp so chronyd can read the NTS source under SELinux

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.

CLAUDE.md

@@ -282,7 +282,14 @@ instead of working around it.
   line in the shared `/run/chrony-dhcp/<iface>.sources` with the plain option-42
   server — silently defeating NTS (authdata Mode `-`, Cook 0). The provisioner now
   `rm`s it (NTS then reached Cook 8 on the bench). Don't re-add a competing writer to
-  that file. **Toggle:** `secure_ntp=false` reverts the dispatcher to the legacy
+  that file. **Second bench finding (2026-07-12, FIXED):** removing that distro script
+  also removed the `restorecon` that had been labelling the sources — the dispatcher's
+  `mkdir -p` leaves `/run/chrony-dhcp` + files as generic `var_run_t`, which
+  `chronyd_t` is SELinux-DENIED reading (loads 0 sources, `authdata` empty). Fixed by
+  `/etc/tmpfiles.d/chrony-dhcp.conf` pre-creating the dir with the stock
+  `chronyd_var_run_t` fcontext at sysinit, so the dispatcher's files inherit a readable
+  label (no allow rules). The dispatcher also now skips `lo` (was writing a spurious
+  duplicate). **Toggle:** `secure_ntp=false` reverts the dispatcher to the legacy
   unauthenticated **DHCP option 42** path (plain `server <ip> iburst`).
 - `fleet` Plymouth theme: confirm (a) the script plugin package actually
   installed (`/usr/lib64/plymouth/script.so` — else the build fell back to

diskless.pkr.hcl

@@ -457,6 +457,16 @@ build {
       # dispatcher supersedes it in BOTH modes, so drop it unconditionally. Leave
       # 20-chrony-onoffline (only marks sources online/offline — harmless).
       "rm -f /usr/lib/NetworkManager/dispatcher.d/20-chrony-dhcp",
+      # ...but the distro script was ALSO (accidentally) labelling /run/chrony-dhcp so
+      # chronyd could read the sources. Removing it exposed that gap: our dispatcher's
+      # `mkdir -p` makes the dir generic var_run_t and the source files inherit it, and
+      # chronyd_t (which only reads chronyd_var_run_t) is SELinux-DENIED reading them →
+      # NTS silently loads 0 sources (bench 2026-07-12, comet-beacon-54). This tmpfiles.d
+      # entry pre-creates /run/chrony-dhcp at sysinit with the stock chronyd_var_run_t
+      # fcontext (before any NM event), so the dispatcher's files inherit a readable
+      # label — no SELinux allow rules needed. Applies in BOTH modes.
+      "install -D -m0644 /tmp/etc-stage/tmpfiles.d/chrony-dhcp.conf /etc/tmpfiles.d/chrony-dhcp.conf",
+      "restorecon /etc/tmpfiles.d/chrony-dhcp.conf",
       "sed -i -E 's/^[[:space:]]*(pool|server)[[:space:]]/#&/' /etc/chrony.conf",
       "grep -q '^sourcedir /run/chrony-dhcp' /etc/chrony.conf || echo 'sourcedir /run/chrony-dhcp' >> /etc/chrony.conf",
       "if [ \"${var.secure_ntp}\" = \"true\" ]; then echo '==> secure NTP: NTS via <${var.ntp_prefix}>.<dhcp-domain> (fleet-CA-authenticated)'; { printf '\\n# Secure NTP (NTS, RFC 8915) — verify the server against the fleet CA. docs/secure-ntp-design.md\\n'; printf 'ntstrustedcerts /etc/dot1x/radius-ca.pem\\n'; printf 'nocerttimecheck 1\\n'; } >> /etc/chrony.conf; else echo '==> legacy NTP: unauthenticated DHCP option-42'; fi",

docs/secure-ntp-design.md

@@ -146,10 +146,31 @@ 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 time (our dispatcher supersedes it in both modes); `20-chrony-onoffline`
-is left in place (harmless — it only marks sources online/offline). **BENCH-VERIFY
-on the next clean build:** with the distro script gone, a normal boot leaves
-`/run/chrony-dhcp/<iface>.sources` = the NTS line and `chronyc authdata` reaches
-`NTS`/cookies > 0 with no manual intervention.
+is left in place (harmless — it only marks sources online/offline).
+
+**2026-07-12 (comet-beacon-54, `secure-ntp-5a3eaed`) — SELinux label on the source
+files (FIXED).** With the clobberer gone the dispatcher wrote the correct
+`server ntp.fleet.lab iburst nts` line, but chrony still 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 the thing `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 -R` relabels it and chrony
+then reaches `NTS Cook 8`). Fix: ship `/etc/tmpfiles.d/chrony-dhcp.conf`
+(`d /run/chrony-dhcp …`) so systemd-tmpfiles pre-creates the dir with the correct
+fcontext at sysinit — files the dispatcher writes then **inherit** `chronyd_var_run_t`
+(bench-verified: after the fix a real NM event wrote `enp0s31f6.sources` as
+`chronyd_var_run_t`, no AVC, `authdata` → `NTS Cook 8`). No SELinux allow rules
+needed. Also fixed: the dispatcher now **skips `lo`** (it was writing a spurious
+`lo.sources` duplicate of the same server, which the distro script had skipped).
+
+**BENCH-VERIFY on the next clean build:** a normal boot leaves
+`/run/chrony-dhcp/<iface>.sources` = the NTS line **labeled `chronyd_var_run_t`**
+(`ls -Z`), no `lo.sources`, and `chronyc -N authdata` reaches `NTS`/cookies > 0 with
+**no manual intervention**.
 
 ## Toggle
 

files/etc/NetworkManager/dispatcher.d/10-chrony-dhcp-ntp

@@ -27,7 +27,11 @@
 # /usr/lib/NetworkManager/dispatcher.d/20-chrony-dhcp writing option-42 servers to
 # the SAME <iface>.sources. NM merges /etc + /usr/lib sorted by name, so it runs
 # AFTER us and would clobber the NTS line — the provisioner removes it (it defeated
-# NTS on the bench: chrony fell back to plain NTP). This script supersedes it.
+# NTS on the bench: chrony fell back to plain NTP). This script supersedes it. It
+# was ALSO (accidentally) labelling the sources chronyd_var_run_t so chronyd could
+# read them; we restore that via /etc/tmpfiles.d/chrony-dhcp.conf (see the dir note
+# below) — without it, under enforcing SELinux chronyd can't read the sources and
+# loads nothing (bench 2026-07-12).
 
 MODE="@NTP_MODE@"      # nts | dhcp
 PREFIX="@NTP_PREFIX@"  # nts: server name = <PREFIX>.<dhcp-domain>
@@ -40,6 +44,15 @@ case "$action" in
     *) exit 0 ;;
 esac
 
+# Loopback carries no DHCP NTP config; acting on it just writes a spurious
+# lo.sources duplicate of the same server (the distro 20-chrony-dhcp skipped lo —
+# we must too, or chrony sees two files for one server). Skip it.
+[ "$interface" = lo ] && exit 0
+
+# /run/chrony-dhcp is pre-created with the chronyd_var_run_t SELinux label by
+# /etc/tmpfiles.d/chrony-dhcp.conf at boot, so the files we write below inherit a
+# label chronyd_t can READ (else, under enforcing, chronyd is denied and loads no
+# sources — bench 2026-07-12). This mkdir is just a fallback if tmpfiles didn't run.
 dir=/run/chrony-dhcp
 file="$dir/${interface}.sources"
 mkdir -p "$dir"

files/etc/tmpfiles.d/chrony-dhcp.conf

@@ -0,0 +1,22 @@
+# Pre-create chrony's runtime NTP source directory with the CORRECT SELinux label
+# at boot, before any NetworkManager event fires. The NM dispatcher
+# (10-chrony-dhcp-ntp) writes <iface>.sources here for chronyd's
+# `sourcedir /run/chrony-dhcp`.
+#
+# Why this exists: the dispatcher's own `mkdir -p /run/chrony-dhcp` creates the dir
+# as generic `var_run_t`, and the source files inherit it — but `chronyd_t` is only
+# allowed to read `chronyd_var_run_t`, so under enforcing SELinux chronyd is DENIED
+# reading them and silently loads ZERO sources (bench 2026-07-12, comet-beacon-54:
+# NTS never activated — `chronyc authdata` empty; AVC `denied { read } … chronyd_t
+# … var_run_t`). The stock RHEL policy already maps /run/chrony-dhcp →
+# `chronyd_var_run_t`, and systemd-tmpfiles applies that fcontext when it creates
+# the dir here at sysinit (well before the dispatcher runs). Files the dispatcher
+# then creates inside inherit `chronyd_var_run_t`, so chronyd can read them — no
+# SELinux allow rules needed (verified on the bench).
+#
+# The distro chrony NM dispatcher (/usr/lib/.../20-chrony-dhcp) used to apply this
+# label via a per-file restorecon; we removed it because it clobbered our NTS source
+# (see diskless.pkr.hcl + the 10-chrony-dhcp-ntp header), so we restore the labelling
+# here instead. Needed in BOTH secure_ntp modes (chronyd must read the sourcedir
+# either way).
+d /run/chrony-dhcp 0755 root root - -