Internet exposure checks and response rate limiting

Jarl works out which views are reachable from the internet (match-clients
ending in a catch-all, not private-looking addresses: an internal view of a
global IPv6 prefix is still yours; a server without views: open allow-query
and a non-private listen address), with a per-view override (schema 9), and
checks public ones: rate limiting, open resolver, minimal-any, cache
snooping, open NOTIFY and transfers, version and host name, management
interfaces. Fixes are staged like any change, including rate limiting from
ISC's example in log-only mode with the secondaries exempt, then enforcing.
named logs what rate limiting limits (or would, in log-only mode, where its
counters don't move) as query-errors; Jarl routes those lines to its log
and counts them (rrl breakdown, ratelimited top lists, Prometheus
jarl_ratelimit_logged_total), shown on the new Exposure page.

A change that newly opens a public view up must be confirmed (accept_risk,
--accept-risk, a checkbox on the Changes page; 409 confirm_risk
otherwise). Findings can be acknowledged with a reason and stay visible as
info. GET /exposure, POST /exposure/fix|ack|unack, jarl exposure,
docs/exposure.md.

Also fixes query statistics skipping TSIG-signed queries ("IP#port/key
NAME" in named's log).

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

internal/server/h_exposure.go

@@ -0,0 +1,146 @@
+package server
+
+import (
+	"net/http"
+	"time"
+
+	"jarl/internal/auth"
+	"jarl/internal/engine"
+	"jarl/internal/model"
+	"jarl/internal/stats"
+	"jarl/internal/validate"
+)
+
+// exposureFinding is an exposure problem with the fix Jarl can stage for
+// it ("" when there is none).
+type exposureFinding struct {
+	validate.Problem
+	Fix string `json:"fix,omitempty"`
+}
+
+type exposureScope struct {
+	validate.Exposure
+	RateLimit string            `json:"rate_limit"` // off, log-only or enforcing
+	Findings  []exposureFinding `json:"findings"`
+}
+
+type exposureReport struct {
+	Scopes []exposureScope `json:"scopes"`
+	// Server holds server-wide findings (version, host name, management
+	// interfaces).
+	Server []exposureFinding `json:"server"`
+	// RateLimiting is what rate limiting limited, or would have, in the
+	// last 24 hours (with query statistics on).
+	RateLimiting *rateLimitActivity `json:"rate_limiting,omitempty"`
+}
+
+type rateLimitActivity struct {
+	Since    string        `json:"since"`
+	Counts   []stats.Entry `json:"counts"`   // drop, slip, would-drop, would-slip
+	Networks []stats.Entry `json:"networks"` // client networks, most limited first
+	Names    []stats.Entry `json:"names"`    // "name TYPE"
+}
+
+// exposure: GET /exposure reports which views are reachable from the
+// internet and what the exposure checks found (docs/exposure.md).
+func (s *Server) exposure(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	if err := require(p, auth.Action{Resource: auth.ResOptions}); err != nil {
+		return err
+	}
+	st, err := s.store.LoadState(r.Context())
+	if err != nil {
+		return err
+	}
+	problems := s.eng.Validate(st)
+	out := exposureReport{Scopes: []exposureScope{}, Server: []exposureFinding{}}
+	finding := func(pr validate.Problem, viewID int64) exposureFinding {
+		_, desc := engine.ExposureFix(st, viewID, pr.Code)
+		return exposureFinding{Problem: pr, Fix: desc}
+	}
+	scopes := map[string]int{}
+	for _, x := range s.eng.Exposures(st) {
+		sc := exposureScope{Exposure: x, RateLimit: "off", Findings: []exposureFinding{}}
+		v := st.Views[x.ViewID]
+		o := st.FindOption(model.ScopeOptions, 0, "rate-limit")
+		if v != nil {
+			if vo := st.FindOption(model.ScopeView, v.ID, "rate-limit"); vo != nil {
+				o = vo
+			}
+		}
+		if o != nil {
+			sc.RateLimit = "enforcing"
+			if validate.LogOnly(o) {
+				sc.RateLimit = "log-only"
+			}
+		}
+		scopes[x.View] = len(out.Scopes)
+		out.Scopes = append(out.Scopes, sc)
+	}
+	for _, pr := range problems {
+		if !validate.Ackable(pr.Code) {
+			continue
+		}
+		if pr.ObjectType == "view" || pr.ObjectType == "zone" {
+			if i, ok := scopes[pr.View]; ok {
+				out.Scopes[i].Findings = append(out.Scopes[i].Findings, finding(pr, out.Scopes[i].ViewID))
+				continue
+			}
+		}
+		out.Server = append(out.Server, finding(pr, 0))
+	}
+	if s.statsQ != nil && p.Can(auth.Action{Resource: auth.ResStats}) {
+		ctx, since := r.Context(), 24*time.Hour
+		a := &rateLimitActivity{Since: "24h"}
+		a.Counts, _ = s.statsQ.Breakdown(ctx, "rrl", since)
+		a.Networks, _ = s.statsQ.Top(ctx, stats.KindRateLimited, since, 10)
+		a.Names, _ = s.statsQ.Top(ctx, stats.KindRateLimitedName, since, 10)
+		out.RateLimiting = a
+	}
+	writeJSON(w, http.StatusOK, out)
+	return nil
+}
+
+// exposureFix: POST /exposure/fix {"view_id": 3, "code": "..."} stages (or
+// applies) the fix for a finding, like any other change.
+func (s *Server) exposureFix(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	var in struct {
+		ViewID int64  `json:"view_id"`
+		View   string `json:"view"`
+		Code   string `json:"code"`
+	}
+	if err := decodeJSON(r, &in); err != nil {
+		return err
+	}
+	st, err := s.store.LoadState(r.Context())
+	if err != nil {
+		return err
+	}
+	if in.View != "" {
+		v := st.ViewByName(in.View)
+		if v == nil {
+			return notFound("no view %s", in.View)
+		}
+		in.ViewID = v.ID
+	}
+	reqs, desc := engine.ExposureFix(st, in.ViewID, in.Code)
+	if reqs == nil {
+		return badRequest("there is no automatic fix for %s: what to allow is yours to decide; change the option yourself, or acknowledge the finding", in.Code)
+	}
+	return s.mutate(w, r, p, desc, reqs, nil)
+}
+
+// exposureAck: POST /exposure/ack {"view": "external", "code": "...",
+// "reason": "..."} accepts a finding (unack takes it back).
+func (s *Server) exposureAck(ack bool) handler {
+	return func(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+		var in engine.AckInput
+		if err := decodeJSON(r, &in); err != nil {
+			return err
+		}
+		op := engine.OpExposureUnack
+		if ack {
+			op = engine.OpExposureAck
+		}
+		return s.mutate(w, r, p, "", []engine.Request{engine.NewRequest(op, 0, in)}, nil)
+	}
+}