docs: cite clean build 28d31e4 for F-02 bench-verification

F-02/P-17 SSH host certs re-verified on the rebuilt 28d31e4 image (not the
hand-fixed host): the auto-derived FQDN principal is baked, so by-FQDN no-TOFU
admin login survives a reboot with zero manual steps. Cite the digest in the
design-doc status + bench-outcome, SSP v0.4 status line + R-16 row, and Annex A
2.4 row + R-16 register row.

docs/ssp.md

@@ -18,7 +18,7 @@
 | Version | 0.4 (DRAFT — pre-assessment) |
 | Date | 2026-07-11 |
 | Author / maintainer | System Owner (delegate) |
-| Status | Lab / pre-production. STIG hardening applied + bench-verified; **UEFI Secure Boot signing verified enforcing on real hardware** (VM HTTP + EliteBook 820 PXE); secure path (802.1X/MACsec) not yet bench-verified. **v0.3 adds the fleet-management plane** (on-host `fleet-agent` telemetry over TPM-mTLS — bench-verified on hardware 2026-07-10; server-side manager with **WebAuthn-passkey** admin MFA + TPM enrolment broker) and July hardening changes (three local SELinux modules; fapolicyd overlay exec-guard fix). **v0.4** adds two host-identity/time hardening features (both implemented 2026-07-11): broker-mediated **SSH host certificates** (F-02/P-17 — **bench-verified 2026-07-11** on `comet-beacon-54`) and **NTS authenticated time** (F-03/P-18 — bench-verify pending). |
+| Status | Lab / pre-production. STIG hardening applied + bench-verified; **UEFI Secure Boot signing verified enforcing on real hardware** (VM HTTP + EliteBook 820 PXE); secure path (802.1X/MACsec) not yet bench-verified. **v0.3 adds the fleet-management plane** (on-host `fleet-agent` telemetry over TPM-mTLS — bench-verified on hardware 2026-07-10; server-side manager with **WebAuthn-passkey** admin MFA + TPM enrolment broker) and July hardening changes (three local SELinux modules; fapolicyd overlay exec-guard fix). **v0.4** adds two host-identity/time hardening features (both implemented 2026-07-11): broker-mediated **SSH host certificates** (F-02/P-17 — **bench-verified 2026-07-11** on `comet-beacon-54`, clean build `28d31e4`) and **NTS authenticated time** (F-03/P-18 — bench-verify pending). |
 | Companion documents | [Annex A — ISM control cross-reference & residual risk](ssp-annex-a-ism-residual-risk.md); [Architecture design v2](diskless-fleet-design-v2.pdf); [Design errata](design-v2-errata.md); [Fleet-management design](fleet-management-design.md); [TPM enrolment design](tpm-enrolment-design.md); [STIG deviation register](stig-deviations.md); [Backlog / POA&M source](TODO.md) |
 
 > **Currency caveat (read before relying on control numbers).** This SSP and its
@@ -410,7 +410,7 @@ production ATO:
 | R-13 | **Boot-chain signing not yet the standing default.** Signing + Secure Boot enforcement **verified end-to-end on hardware** (VM HTTP UKI 2026-06-20; 820 PXE signed iPXE→UKI 2026-06-22), but unsigned/SB-OFF lab builds are still possible (CI signs only when `SB_KEY`/`SB_CERT` are set) and not all hosts have `db` enrolled. | **Low** | Treat — make signed + Secure-Boot-on the default for all production builds/hosts (set CI secrets; enrol `db` fleet-wide). |
 | R-14 | **Management/enrolment plane is a connected system, built but not yet separately authorised.** The host now trusts + streams to the fleet-manager and enrols via the broker/**step-ca fleet CA** (a new trust anchor + key material) whose one **unauthenticated pre-auth CSR endpoint** is a new server-side surface. Host-side exposure is limited (outbound-only mTLS, read-only telemetry, commands logged-not-applied in v1). | **Medium** | Treat — separate SSP/authorisation for the management plane (CA key protection, broker endpoint hardening, InfluxDB token/data, admin-plane exposure). |
 | R-15 | **Deferred agent reconcile actuators.** v1 receives `DesiredState`/`Command` but only logs them; when actuation (apply kiosk_url / reboot / drain) is built, the agent becomes a **remote host-mutation channel** needing re-assessment. | **Low** (v1) | Treat at build time — assess the command/authZ path before enabling actuators. |
-| R-16 | Per-boot SSH host keys made admin SSH perpetual **TOFU** (LAN MITM client-undetectable). **Remediated 2026-07-11**: broker-mediated **SSH host certificates** (`enable_ssh_hostcert=true`) — per-boot key signed by the fleet SSH CA via the enrol-broker host plane (TPM-mTLS); admins trust one `@cert-authority` line. **Bench-verified 2026-07-11** (comet-beacon-54: FQDN login, no TOFU; per-boot re-sign across reboot; SELinux clean). | **Low** | Treat — roll the `@cert-authority` anchor to admins; broker-side principal validation is a defence-in-depth TODO (F-02/P-17). |
+| R-16 | Per-boot SSH host keys made admin SSH perpetual **TOFU** (LAN MITM client-undetectable). **Remediated 2026-07-11**: broker-mediated **SSH host certificates** (`enable_ssh_hostcert=true`) — per-boot key signed by the fleet SSH CA via the enrol-broker host plane (TPM-mTLS); admins trust one `@cert-authority` line. **Bench-verified 2026-07-11 on clean build `28d31e4`** (comet-beacon-54: FQDN login by name, no TOFU, **survives reboot unattended**; SELinux clean). | **Low** | Treat — roll the `@cert-authority` anchor to admins; broker-side principal validation is a defence-in-depth TODO (F-02/P-17). |
 | R-17 | Time source was **unauthenticated** (DHCP-handed NTP) — the clock feeds every certificate-validity decision. **Remediated 2026-07-11**: **NTS** (RFC 8915, `secure_ntp=true`) — fleet-CA-signed NTS-KE cert verified against `radius-ca.pem`; server name derived from the DHCP domain (no baked FQDN); a spoofer can only DoS. **Bench-verify pending.** | **Low** (once verified) | Treat — bench-verify `chronyc authdata` cookies + tcp/4460 + cold-clock + STIG chrony; issue the per-env NTS cert (F-03/P-18). |
 
 Each is detailed, ISM-cross-referenced, rated and assigned a treatment in Annex A.