Workstream E of the DNS hardening push. Two independent pfSense-side
changes to eliminate single-point DNS failures and the unauthenticated
RFC 2136 update vector.
Part 1 — Multi-IP DHCP option 6
- Before: clients on 10.0.10/24 got only 10.0.10.1; clients on 10.0.20/24
got only 10.0.20.1. Internal resolver outage == cluster-wide DNS dark.
- After:
- 10.0.10/24 -> [10.0.10.1, 94.140.14.14]
- 10.0.20/24 -> [10.0.20.1, 94.140.14.14]
- 192.168.1/24 deliberately untouched (served by TP-Link AP, not pfSense
Kea — pfSense WAN DHCP is disabled); already ships [192.168.1.2,
94.140.14.14] so the end state is consistent across all three subnets.
- Applied via PHP: set $cfg['dhcpd']['lan']['dnsserver'] and
$cfg['dhcpd']['opt1']['dnsserver'] as arrays. pfSense's
services_kea4_configure() implodes the array into "data: a, b" on the
"domain-name-servers" option-data entry (services.inc L1214).
- Verified:
- DevVM (10.0.10.10) resolv.conf shows "nameserver 10.0.10.1" +
"nameserver 94.140.14.14" after networkd renew.
- k8s-node1 (10.0.20.101) same after networkctl reload + systemd-resolved
restart.
- Fallback drill on k8s-node1: `ip route add blackhole 10.0.20.1/32`;
dig @10.0.20.1 google.com -> "no servers could be reached"; dig
@94.140.14.14 google.com -> 216.58.204.110; system resolver
(getent hosts) succeeds via the fallback IP. Blackhole route removed.
Part 2 — TSIG-signed Kea DHCP-DDNS
- Before: /usr/local/etc/kea/kea-dhcp-ddns.conf had `tsig-keys: []` and
Technitium's viktorbarzin.lan zone had update=Deny. Unauthenticated
update vector was latent (DDNS wiring in Kea DHCP4 is actually off
today — "DDNS: disabled" in dhcpd.log) but would activate as soon as
anyone turned on ddnsupdate on LAN/OPT1.
- Generated HMAC-SHA256 secret, base64-encoded 32 random bytes.
- Stored in Vault: secret/viktor/kea_ddns_tsig_secret (version 27).
- Created TSIG key "kea-ddns" on primary/secondary/tertiary Technitium
instances via /api/settings/set (tsigKeys[]).
- Updated kea-dhcp-ddns.conf on pfSense with
tsig-keys[]={name: "kea-ddns", algorithm: "HMAC-SHA256", secret: …}
and key-name: kea-ddns on each forward-ddns / reverse-ddns domain.
Pre-change backup at /usr/local/etc/kea/kea-dhcp-ddns.conf.2026-04-19-pre-tsig.
- Configured viktorbarzin.lan + 10.0.10.in-addr.arpa +
20.0.10.in-addr.arpa + 1.168.192.in-addr.arpa on Technitium primary:
- update = UseSpecifiedNetworkACL
- updateNetworkACL = [10.0.20.1, 10.0.10.1, 192.168.1.2]
- updateSecurityPolicies = [{tsigKeyName: kea-ddns,
domain: "*.<zone>", allowedTypes: [ANY]}]
Technitium requires BOTH a source-IP match AND a valid TSIG signature.
- Verified TSIG end-to-end:
- Signed A-record update from pfSense -> "successfully processed",
dig returns 10.99.99.99 (log: "TSIG KeyName: kea-ddns; TSIG Algo:
hmac-sha256; TSIG Error: NoError; RCODE: NoError").
- Signed PTR update same zone pattern -> dig -x returns tsig-test
FQDN.
- Unsigned update from pfSense IP (in ACL) -> "update failed:
REFUSED" (log: "refused a zone UPDATE request [...] due to Dynamic
Updates Security Policy").
- Test records cleaned up via signed nsupdate.
Safety
- pfSense config backup: /cf/conf/config.xml.2026-04-19-pre-kea-multi-ip
(145898 bytes, pre-change snapshot — keep 30d).
- DDNS config backup: /usr/local/etc/kea/kea-dhcp-ddns.conf.2026-04-19-pre-tsig.
- TSIG secret lives only in Vault + in config.xml/kea-dhcp-ddns.conf on
pfSense; not committed to git.
Docs
- architecture/dns.md: zone dynamic-updates section records the TSIG
policy; Incident History gets a WS E entry.
- architecture/networking.md: DHCP Coverage table now shows the DNS
option 6 values per subnet; pfSense block notes the TSIG-signed DDNS
and config backup path.
- runbooks/pfsense-unbound.md: new "Kea DHCP-DDNS TSIG" section covers
key rotation, emergency bypass, and enforcement-verification.
Closes: code-o6j
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Viktor Barzin