61 lines
2.4 KiB
Bash
61 lines
2.4 KiB
Bash
#!/bin/bash
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# NetworkManager dispatcher: point chrony at the fleet NTP server, learned from
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# DHCP at runtime (no FQDN baked into the image). Two modes, baked at build time:
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#
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# nts (secure_ntp=true, default): AUTHENTICATED time. Derive the server NAME
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# from the DHCP-provided domain as <PREFIX>.<domain> and write
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# `server NAME iburst nts`. chrony verifies the NTS-KE TLS cert against the
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# fleet CA (chrony.conf: ntstrustedcerts). Because the domain comes from
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# DHCP, a domain change needs only a new DHCP domain + reissued NTS cert —
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# no image rebuild. A DHCP/NTP/DNS spoofer can only DoS (no fleet-CA-signed
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# cert for the name it redirects to => NTS fails => no sync); it cannot
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# shift the clock. See docs/secure-ntp-design.md (F-03/P-18).
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#
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# dhcp (secure_ntp=false): LEGACY, UNAUTHENTICATED. Write the DHCP option-42
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# server IPs as plain `server <ip> iburst`. Lab/interop only.
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#
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# We use NetworkManager's internal DHCP (the network-manager dracut port); NM
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# exports the lease's domain as $DHCP4_DOMAIN_NAME (option 15) / $DHCP4_DOMAIN_SEARCH
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# (option 119) and NTP servers as $DHCP4_NTP_SERVERS (option 42). chrony.conf
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# carries `sourcedir /run/chrony-dhcp`, so writing <iface>.sources there and
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# reloading makes chronyd use them. The baked public pool is stripped (provisioner).
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#
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# Installed 0755 root:root. Lenient on purpose: a hiccup here must never break
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# networking. @NTP_MODE@/@NTP_PREFIX@ are substituted at build time.
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MODE="@NTP_MODE@" # nts | dhcp
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PREFIX="@NTP_PREFIX@" # nts: server name = <PREFIX>.<dhcp-domain>
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interface="$1"
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action="$2"
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case "$action" in
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up|dhcp4-change|reapply) ;;
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*) exit 0 ;;
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esac
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dir=/run/chrony-dhcp
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file="$dir/${interface}.sources"
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mkdir -p "$dir"
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if [ "$MODE" = nts ]; then
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# Prefer option 15 (domain-name); fall back to the first option-119 search domain.
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domain="${DHCP4_DOMAIN_NAME:-}"
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[ -z "$domain" ] && domain="${DHCP4_DOMAIN_SEARCH%% *}"
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if [ -n "$domain" ]; then
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printf 'server %s.%s iburst nts\n' "$PREFIX" "$domain" > "$file"
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# Pick up the new source without restarting chronyd.
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chronyc reload sources >/dev/null 2>&1 || true
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fi
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else
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if [ -n "${DHCP4_NTP_SERVERS:-}" ]; then
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: > "$file"
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for s in $DHCP4_NTP_SERVERS; do
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printf 'server %s iburst\n' "$s" >> "$file"
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done
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chronyc reload sources >/dev/null 2>&1 || true
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fi
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fi
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exit 0
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