Build Housecarl 0.1.0: the nftables firewall manager

Zones, address sets (IPv4 and IPv6 mixed, dynamic sets with timeouts) and
services, ordered rules in the early, input, forward and output chains,
port forwards with hairpin NAT and IPv6 pinholes, source NAT, redirects,
and switchable built-ins (loopback, conntrack, ICMPv6, antispoofing, MSS
clamping, DHCPv6 client, flowtable). Every change is validated, checked
with nft -c and applied in one transaction to Housecarl's own table,
inet housecarl; changes made over the network roll back unless
confirmed, and the confirmed ruleset is loaded at boot by
housecarl-ruleset.service. An empty configuration applies nothing.

Also: hit counters and the drop log (nflog), 'hc import' of an existing
nftables ruleset and 'hc takeover', the hc CLI, the REST API and the web
UI, users, scoped tokens (sets:write:NAME), the audit log, the web UI's
certificate through Jarl, Debian packages, docs, unit tests with real
nft 1.1.3, and an e2e test with real traffic (71 checks).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/h_cert.go

@@ -0,0 +1,94 @@
+package server
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"housecarl/internal/api"
+	"housecarl/internal/auth"
+	"housecarl/internal/certs"
+	"housecarl/internal/validate"
+)
+
+func (s *Server) certificate(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	if err := requireAdmin(p); err != nil {
+		return err
+	}
+	out := api.CertificateResponse{Source: "none"}
+	switch {
+	case s.cfg.ACME != nil:
+		st := s.cfg.ACME.Status()
+		out.Configured, out.Source, out.Status = true, "acme", &st
+	case s.cfg.TLSCertFile != "":
+		out.Source = "file"
+	}
+	writeJSON(w, http.StatusOK, out)
+	return nil
+}
+
+func (s *Server) acmeManager() (*certs.Manager, error) {
+	if s.cfg.ACME == nil {
+		return nil, conflict("housecarld doesn't obtain its certificate: set tls.acme and jarl in housecarl.yaml (docs/certificates.md)")
+	}
+	return s.cfg.ACME, nil
+}
+
+// certificateCheck: POST /certificate/check runs the preflight check now
+// (it takes up to a few minutes when the record is slow to appear).
+func (s *Server) certificateCheck(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	if err := requireAdmin(p); err != nil {
+		return err
+	}
+	m, err := s.acmeManager()
+	if err != nil {
+		return err
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 4*time.Minute)
+	defer cancel()
+	c := m.Preflight(ctx)
+	s.eng.Audit(r.Context(), p, "certificate.check", m.Status().Domain, map[bool]string{true: "success", false: "failure"}[c.OK], "")
+	writeJSON(w, http.StatusOK, c)
+	return nil
+}
+
+// certificateRenew: POST /certificate/renew gets a new certificate now, in
+// the background (GET /certificate follows it).
+func (s *Server) certificateRenew(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	if err := requireAdmin(p); err != nil {
+		return err
+	}
+	m, err := s.acmeManager()
+	if err != nil {
+		return err
+	}
+	m.Kick()
+	s.eng.Audit(r.Context(), p, "certificate.renew", m.Status().Domain, "success", "")
+	st := m.Status()
+	writeJSON(w, http.StatusAccepted, api.CertificateResponse{Configured: true, Source: "acme", Status: &st})
+	return nil
+}
+
+// certificateProblems are the certificate's problems for /status.
+func (s *Server) certificateProblems() []validate.Problem {
+	if s.cfg.ACME == nil {
+		return nil
+	}
+	st := s.cfg.ACME.Status()
+	obj := "certificate " + st.Domain
+	var out []validate.Problem
+	if st.LastError != "" {
+		out = append(out, validate.Problem{Severity: validate.Warning, Code: "certificate_failed", Object: obj,
+			Message: "getting the web UI's certificate failed: " + st.LastError})
+	}
+	if st.NotAfter != nil && time.Until(*st.NotAfter) < 14*24*time.Hour {
+		out = append(out, validate.Problem{Severity: validate.Warning, Code: "certificate_expiring", Object: obj,
+			Message: fmt.Sprintf("the certificate ends %s and hasn't been renewed", st.NotAfter.Local().Format("2006-01-02 15:04"))})
+	}
+	if st.State == "ok" && st.Staging {
+		out = append(out, validate.Problem{Severity: validate.Warning, Code: "certificate_staging", Object: obj,
+			Message: "the certificate is from Let's Encrypt's staging service, which browsers don't trust: once it works, set tls.acme.directory: letsencrypt and restart housecarld"})
+	}
+	return out
+}