Give every view a TSIG key that selects it

Each view's match-clients starts with "key jarl-view-NAME" (after
"!key" for the views listed after it), so a query signed with a view's
key lands in that view from any address. The secrets are derived from a
random seed in Jarl's database. The delegation check signs its queries
to this server's own addresses with the key of the zone's view: before,
they got whichever view matched the server's address, usually internal.
jarl view key / GET /views/{id}/key show a key for dig -k (tsig:write,
audited). jarl-view- key names are reserved; the importer drops view
keys from a configuration Jarl wrote.

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

internal/server/h_config.go

@@ -14,6 +14,7 @@ import (
 	"jarl/internal/dnsname"
 	"jarl/internal/engine"
 	"jarl/internal/model"
+	"jarl/internal/render"
 	"jarl/internal/rr"
 )
 
@@ -92,6 +93,31 @@ func (s *Server) getView(w http.ResponseWriter, r *http.Request, p *auth.Princip
 	return nil
 }
 
+// viewKey: GET /views/{id}/key is the TSIG key that selects the view
+// (render/viewkeys.go), with its secret: like revealing a TSIG key's, it
+// needs tsig:write and is audited.
+func (s *Server) viewKey(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	st, err := s.state(r)
+	if err != nil {
+		return err
+	}
+	v, err := s.viewByPath(r, st, p)
+	if err != nil {
+		return err
+	}
+	if err := require(p, auth.Action{Resource: auth.ResTSIG, Write: true}); err != nil {
+		return forbidden("showing a view's key needs tsig:write")
+	}
+	seed, err := engine.ViewKeySeed(r.Context(), s.store)
+	if err != nil {
+		return err
+	}
+	name := render.ViewKeyName(v.Name)
+	s.eng.Audit(r.Context(), p, "tsig.reveal", "view", v.ID, v.Name, "success", "view key "+name+" shown")
+	writeJSON(w, http.StatusOK, map[string]string{"name": name, "algorithm": render.ViewKeyAlgorithm, "secret": render.ViewKeySecret(seed, v.ID)})
+	return nil
+}
+
 func (s *Server) viewObject(r *http.Request) func(st *model.State, id int64) any {
 	return func(st *model.State, id int64) any {
 		if v := st.Views[id]; v != nil {

internal/server/h_nscheck.go

@@ -160,6 +160,9 @@ func (s *Server) zoneDelegation(w http.ResponseWriter, r *http.Request, p *auth.
 		return badRequest("the delegation check compares the parent's delegation with the zone's NS records, so it needs a primary zone (this is a %s zone; check it where its primary is)", z.Type)
 	}
 	c := s.checker()
+	// This server's own addresses are asked too: sign those queries with
+	// the key of the zone's view, so they get that view's answer.
+	c.LocalKey = s.eng.ViewKey(r.Context(), st, z)
 	if v := r.URL.Query().Get("resolver"); v != "" {
 		// An address only, always port 53: this is a DNS resolver.
 		a, err := netip.ParseAddr(v)

internal/server/routes.go

@@ -52,6 +52,7 @@ func (s *Server) routes() {
 	m.HandleFunc("POST "+p+"/views", s.authed(s.createView))
 	m.HandleFunc("POST "+p+"/views/order", s.authed(s.reorderViews))
 	m.HandleFunc("GET "+p+"/views/{id}", s.authed(s.getView))
+	m.HandleFunc("GET "+p+"/views/{id}/key", s.authed(s.viewKey))
 	m.HandleFunc("PATCH "+p+"/views/{id}", s.authed(s.updateView))
 	m.HandleFunc("DELETE "+p+"/views/{id}", s.authed(s.deleteView))
 	m.HandleFunc("PUT "+p+"/views/{id}/color", s.authed(s.setViewColor))