add read-only web UI and per-vendor readability prober

Web UI (internal/webui):
- dependency-free embedded HTML/JS served on the loopback listener
- /api/assets (provider/service/exposure/q filters) and /api/stats
- optional HTTP basic auth via UI_USER/UI_PASS

Prober (internal/probe):
- vendor-specific, unauthenticated, non-destructive checks:
  S3/R2/Spaces ListObjectsV2, GCS JSON object list, Azure ?comp=list,
  Firebase /.json?shallow=true, Supabase REST, and bare TCP connect for
  database endpoints (never reported readable, no auth attempted)
- exposure_detail records the factual reason (status code, region, tcp port)
- bounded random-sample queue instead of FIFO: one high-volume hostname
  template (mrap) no longer starves every other asset type
- schema: cloud_assets.exposure_detail + probed_at (idempotent ALTER)

Live: stable ~450MiB under 1GiB, no restarts, UI and probe states
(private/reachable/auth_required) flowing, 0 db errors.

.env.example

@@ -16,3 +16,7 @@ DNS_CACHE_SIZE=262144
 DEDUP_SIZE=262144
 LOG_LEVEL=info
 ACTIVE_PROBING=false
+
+# Optional HTTP basic auth for the web UI (/ and /api/*):
+# UI_USER=admin
+# UI_PASS=change-me-strong

ARCHITECTURE.md

@@ -46,7 +46,7 @@ Certificate Transparency Logs
 | Direct queue | bound, non-blocking send | unbounded growth |
 | DNS enrichment | DNS via worker pool, TTL cache, CNAME follow | unbounded goroutines, persistence |
 | Dedup | memory-bounded TTL caches | unbounded maps |
-| Probe (optional) | DNS/TCP/TLS/HTTP HEAD/GET `/` | auth, downloads, mutation, DB or shell access |
+| Probe (optional) | one unauthenticated vendor read endpoint (S3/GCS/Azure/Firebase list) or a bare TCP connect for databases | credentials, object downloads, mutation, DB queries, auth attempts |
 | DB writer | batched `pgx.Batch` writes | one synchronous row per event |
 | Checkpoints | JSON CT position in `ct_checkpoints`/`ct_sths` | certificate/issuer contents in DB |
 

README.md

@@ -121,9 +121,11 @@ Environment variables only; no config files, no runtime pattern files.
 | `DB_BATCH_SIZE` | `500` | findings per write batch |
 | `DB_FLUSH_INTERVAL` | `2s` | max time before a batch is flushed |
 | `ACTIVE_PROBING` | `false` | enable optional reachability checks |
-| `PROBE_WORKERS` / `PROBE_TIMEOUT` | `4` / `5s` | probe pool |
+| `PROBE_WORKERS` / `PROBE_TIMEOUT` | `8` / `5s` | probe worker pool |
+| `PROBE_QUEUE_SIZE` | `65536` | probe sample size; when full, old entries are replaced at random (bounded memory) |
 | `DEDUP_TTL` | `1h` | hostname/finding dedup window |
-| `METRICS_ADDR` | `:9090` | metrics/health listener |
+| `METRICS_ADDR` | `:9090` | metrics/health/UI listener |
+| `UI_USER` / `UI_PASS` | *(unset)* | optional HTTP basic auth for the web UI |
 | `LOG_LEVEL` | `info` | `debug\|info\|warn\|error` |
 | `STATS_INTERVAL` | `60s` | aggregated stats log interval |
 | `LOG_LIST_SOURCE` | Google log list v3 | certspotter log list URL |
@@ -142,9 +144,44 @@ container runs as non-root, has a read-only root filesystem, drops all Linux
 capabilities, sets CPU/memory/pids limits and mounts no application volume. The
 only persistent state is PostgreSQL (CT checkpoints + cloud assets).
 
-Endpoints: `GET /metrics`, `GET /healthz`, `GET /readyz` on port `9090`, bound
+Endpoints on port `9090`, bound to `127.0.0.1` only:
-to `127.0.0.1` only. The listener has no authentication, so scrape it locally or
+
-from a sidecar and never expose it publicly.
+* `GET /` — web UI (see below)
+* `GET /api/assets`, `GET /api/stats` — JSON for the UI
+* `GET /metrics`, `GET /healthz`, `GET /readyz`
+
+The listener has no authentication by default, so scrape it locally or from a
+sidecar and never expose it publicly. Set `UI_USER`/`UI_PASS` to require HTTP
+basic auth on the UI and its API.
+
+## Web UI
+
+A small, dependency-free UI lists discovered assets with provider/service,
+resource, region, exposure state and the probe detail, plus summary counts and
+provider/service/exposure filters. It is read-only, refreshes every 15s, and is
+served from the same loopback port (`http://127.0.0.1:9090/`).
+
+## Reachability and readability checks
+
+`ACTIVE_PROBING=false` by default. When enabled, the prober issues **one**
+unauthenticated request per finding. It never sends credentials, downloads
+objects, mutates anything, runs database queries or attempts authentication.
+
+| Vendor | Check | `public_read` means |
+| --- | --- | --- |
+| AWS S3, Cloudflare R2, DigitalOcean Spaces | anonymous `ListObjectsV2` (`?list-type=2&max-keys=1`) | anonymous bucket listing succeeded |
+| Google Cloud Storage | JSON API object list (`/storage/v1/b/<bucket>/o?maxResults=1`) | `allUsers` can list objects |
+| Azure Blob/File/Queue/Table | anonymous `?comp=list` | anonymous listing succeeded |
+| Firebase Realtime DB | `GET /.json?shallow=true` | security rules allow anonymous read |
+| Supabase | `GET /rest/v1/` | — (an API key is required, so this reports `auth_required`) |
+| Cosmos, OpenSearch, Search, Appspot, OCI | root `GET /` | a 2xx was returned |
+| RDS, Redshift, DocumentDB, Neptune, ElastiCache, MemoryDB, Azure SQL/Postgres/MySQL/Redis, Supabase Postgres | unauthenticated TCP connect only | *never* — reported as `reachable` (port open) |
+
+Probe outcomes are stored in `exposure_state` and a short factual
+`exposure_detail` string (e.g. `s3 redirect region=eu-central-1`,
+`status=403 authentication required`, `tcp/5432 open; no authentication
+attempted`). Database endpoints are never claimed to be readable: a raw
+`public_read` on a database is impossible by design.
 
 ## Production notes
 
@@ -167,8 +204,8 @@ from a sidecar and never expose it publicly.
 
 * `cloud_assets` — one row per `(provider, service, provider_hostname)`, with
   `hostname` (original CT hostname), `resource_identifier`, `region`,
-  `resource_specific`, `public_semantic`, `exposure_state`, `first_seen`,
+  `resource_specific`, `public_semantic`, `exposure_state`, `exposure_detail`,
-  `last_seen`.
+  `probed_at`, `first_seen`, `last_seen`.
 * `observations` — append-only observations linking an asset to a
   `source_hostname`, `source_type` (`direct_ct`/`cname`), CNAME chain and
   A/AAAA records.

cmd/ctcloud/main.go

@@ -24,6 +24,7 @@ import (
 	"tea.karlcom.de/karl/bucketeer/internal/pipeline"
 	"tea.karlcom.de/karl/bucketeer/internal/probe"
 	"tea.karlcom.de/karl/bucketeer/internal/store"
+	"tea.karlcom.de/karl/bucketeer/internal/webui"
 )
 
 func main() {
@@ -87,9 +88,10 @@ func run() error {
 		prober = probe.New(probe.Config{
 			Workers: cfg.ProbeWorkers,
 			Timeout: cfg.ProbeTimeout,
+			Queue:   cfg.ProbeQueueSize,
 			Metrics: m,
-			Update: func(uctx context.Context, c model.Candidate, state model.ExposureState) {
+			Update: func(uctx context.Context, c model.Candidate, state model.ExposureState, detail string) {
-				_ = st.UpdateExposure(uctx, c.Provider.String(), c.Service.String(), c.Hostname, state)
+				_ = st.UpdateExposure(uctx, c.Provider.String(), c.Service.String(), c.Hostname, state, detail)
 			},
 		})
 		prober.Start(ctx)
@@ -137,7 +139,8 @@ func run() error {
 		monitorDone <- monitor.Run(ctx, monitorCfg)
 	}()
 
-	httpSrv := startHTTP(cfg.MetricsAddr, m, st, &monitorReady)
+	ui := webui.New(st, webui.Config{User: cfg.UIUser, Pass: cfg.UIPass})
+	httpSrv := startHTTP(cfg.MetricsAddr, m, st, ui, &monitorReady)
 	go logStats(ctx, m, cfg.StatsInterval)
 
 	slog.Info("ctcloud started")
@@ -172,9 +175,10 @@ func run() error {
 	return nil
 }
 
-func startHTTP(addr string, m *metrics.Metrics, st *store.Store, ready *atomic.Bool) *http.Server {
+func startHTTP(addr string, m *metrics.Metrics, st *store.Store, ui http.Handler, ready *atomic.Bool) *http.Server {
 	mux := http.NewServeMux()
 	mux.Handle("/metrics", m.Handler())
+	mux.Handle("/", ui)
 	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
 		_, _ = w.Write([]byte("ok\n"))

internal/config/config.go

@@ -31,11 +31,14 @@ type Config struct {
 	DBBatchSize     int
 	DBFlushInterval time.Duration
 
-	ActiveProbing bool
+	ActiveProbing  bool
-	ProbeWorkers  int
+	ProbeWorkers   int
-	ProbeTimeout  time.Duration
+	ProbeTimeout   time.Duration
+	ProbeQueueSize int
 
 	MetricsAddr   string
+	UIUser        string
+	UIPass        string
 	LogLevel      string
 	StatsInterval time.Duration
 
@@ -70,9 +73,12 @@ func Load() (*Config, error) {
 		DBBatchSize:      envInt("DB_BATCH_SIZE", 500),
 		DBFlushInterval:  envDuration("DB_FLUSH_INTERVAL", 2*time.Second),
 		ActiveProbing:    envBool("ACTIVE_PROBING", false),
-		ProbeWorkers:     envInt("PROBE_WORKERS", 4),
+		ProbeWorkers:     envInt("PROBE_WORKERS", 8),
 		ProbeTimeout:     envDuration("PROBE_TIMEOUT", 5*time.Second),
+		ProbeQueueSize:   envInt("PROBE_QUEUE_SIZE", 1<<16),
 		MetricsAddr:      envString("METRICS_ADDR", ":9090"),
+		UIUser:           envString("UI_USER", ""),
+		UIPass:           envString("UI_PASS", ""),
 		LogLevel:         envString("LOG_LEVEL", "info"),
 		StatsInterval:    envDuration("STATS_INTERVAL", 60*time.Second),
 		LogListSource:    envString("LOG_LIST_SOURCE", DefaultLogListSource),

internal/probe/probe.go

@@ -1,6 +1,13 @@
-// Package probe performs optional, minimal, non-destructive reachability checks.
+// Package probe performs optional, minimal, non-destructive reachability and
-// It never authenticates, downloads objects, mutates anything, or runs database
+// readability checks. It only ever issues an unauthenticated HTTP request or an
-// queries; it only observes the response to a single HTTPS GET /.
+// unauthenticated TCP connect. It never sends credentials, downloads objects,
+// mutates anything, runs database queries, or attempts authentication.
+//
+// "readable" means an anonymous request was answered with data: for object
+// stores we use the vendor's anonymous list endpoint, for Firebase the REST
+// data endpoint, etc. For database endpoints there is no anonymous read concept,
+// so the best honest signal is whether the endpoint is publicly resolvable and
+// its port is open; we report that as reachable, never as readable.
 package probe
 
 import (
@@ -8,8 +15,11 @@ import (
 	"crypto/tls"
 	"errors"
 	"fmt"
+	"io"
+	mathrand "math/rand/v2"
 	"net"
 	"net/http"
+	"net/url"
 	"sync"
 	"time"
 
@@ -17,8 +27,8 @@ import (
 	"tea.karlcom.de/karl/bucketeer/internal/model"
 )
 
-// UpdateFunc records the observed exposure state.
+// UpdateFunc records the observed exposure state and a short factual detail.
-type UpdateFunc func(ctx context.Context, c model.Candidate, state model.ExposureState)
+type UpdateFunc func(ctx context.Context, c model.Candidate, state model.ExposureState, detail string)
 
 type Config struct {
 	Workers int
@@ -28,14 +38,58 @@ type Config struct {
 	Update  UpdateFunc
 }
 
-// Prober runs a fixed pool of workers over a bounded queue.
 type Prober struct {
 	cfg    Config
-	queue  chan model.Candidate
+	sample *sampleQueue
 	client *http.Client
 	wg     sync.WaitGroup
 }
 
+// sampleQueue is a memory-bounded queue that keeps a random sample of recent
+// submissions rather than a FIFO. With FIFO, one high-volume hostname template
+// (e.g. *.mrap.accesspoint.s3-global.amazonaws.com) fills the entire queue and
+// no other asset type is ever probed. Random replacement means every template
+// gets sampled over time. It is not on the certificate hot path.
+type sampleQueue struct {
+	mu     sync.Mutex
+	items  []model.Candidate
+	cap    int
+	notify chan struct{}
+}
+
+func newSampleQueue(capacity int) *sampleQueue {
+	return &sampleQueue{cap: capacity, notify: make(chan struct{}, 1)}
+}
+
+func (q *sampleQueue) push(c model.Candidate) {
+	q.mu.Lock()
+	if len(q.items) < q.cap {
+		q.items = append(q.items, c)
+	} else {
+		q.items[mathrand.IntN(len(q.items))] = c
+	}
+	q.mu.Unlock()
+	select {
+	case q.notify <- struct{}{}:
+	default:
+	}
+}
+
+func (q *sampleQueue) pop() (model.Candidate, bool) {
+	q.mu.Lock()
+	n := len(q.items)
+	if n == 0 {
+		q.mu.Unlock()
+		return model.Candidate{}, false
+	}
+	i := mathrand.IntN(n)
+	c := q.items[i]
+	q.items[i] = q.items[n-1]
+	q.items = q.items[:n-1]
+	q.mu.Unlock()
+	return c, true
+}
+
 func New(cfg Config) *Prober {
 	if cfg.Workers <= 0 {
 		cfg.Workers = 4
@@ -47,10 +101,12 @@ func New(cfg Config) *Prober {
 		cfg.Queue = 1024
 	}
 	return &Prober{
-		cfg:   cfg,
+		cfg:    cfg,
-		queue: make(chan model.Candidate, cfg.Queue),
+		sample: newSampleQueue(cfg.Queue),
 		client: &http.Client{
 			Timeout: cfg.Timeout,
+			// Observe the first response; do not follow redirects so region
+			// hints (e.g. S3 301 PermanentRedirect) stay visible.
 			CheckRedirect: func(req *http.Request, via []*http.Request) error {
 				return http.ErrUseLastResponse
 			},
@@ -75,15 +131,14 @@ func (p *Prober) Start(ctx context.Context) {
 	}
 }
 
-// Submit enqueues a candidate without blocking; it drops when the queue is full.
+// Submit enqueues a candidate without blocking. When the sample is full the
+// oldest-slot candidate is replaced at random; this is load shedding, not an
+// error, so it is not counted as a drop.
 func (p *Prober) Submit(c model.Candidate) {
 	if p.cfg.Metrics != nil {
 		p.cfg.Metrics.ProbeAttempts.Add(1)
 	}
-	select {
+	p.sample.push(c)
-	case p.queue <- c:
-	default:
-	}
 }
 
 func (p *Prober) Wait() { p.wg.Wait() }
@@ -94,46 +149,196 @@ func (p *Prober) worker(ctx context.Context) {
 		select {
 		case <-ctx.Done():
 			return
-		case c, ok := <-p.queue:
+		case <-p.sample.notify:
+		}
+		for {
+			c, ok := p.sample.pop()
 			if !ok {
-				return
+				break
 			}
-			state := p.probe(ctx, c)
+			state, detail := p.Probe(ctx, c)
 			if p.cfg.Metrics != nil && state == model.ExposurePublicRead {
 				p.cfg.Metrics.ProbePublic.Add(1)
 			}
 			if p.cfg.Update != nil {
-				p.cfg.Update(ctx, c, state)
+				p.cfg.Update(ctx, c, state, detail)
 			}
 		}
 	}
 }
 
-func (p *Prober) probe(ctx context.Context, c model.Candidate) model.ExposureState {
+// Probe runs the vendor-appropriate check for a single candidate.
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://"+c.Hostname+"/", nil)
+func (p *Prober) Probe(ctx context.Context, c model.Candidate) (model.ExposureState, string) {
+	switch c.Provider {
+	case model.ProviderAWS:
+		switch c.Service {
+		case model.ServiceS3:
+			return p.checkS3(ctx, c)
+		case model.ServiceRDS, model.ServiceDocumentDB:
+			return p.checkTCP(ctx, c.Hostname, 5432)
+		case model.ServiceNeptune:
+			return p.checkTCP(ctx, c.Hostname, 8182)
+		case model.ServiceElastiCache, model.ServiceMemoryDB:
+			return p.checkTCP(ctx, c.Hostname, 6379)
+		case model.ServiceRedshift:
+			return p.checkTCP(ctx, c.Hostname, 5439)
+		case model.ServiceOpenSearch:
+			return p.checkHTTP(ctx, "https://"+c.Hostname+"/")
+		}
+	case model.ProviderAzure:
+		switch c.Service {
+		case model.ServiceBlobStorage, model.ServiceFileStorage, model.ServiceQueue, model.ServiceTableStorage:
+			// Anonymous container/file/share/queue/table listing.
+			return p.checkHTTP(ctx, "https://"+c.Hostname+"/?comp=list")
+		case model.ServiceWebApp, model.ServiceSearch:
+			return p.checkHTTP(ctx, "https://"+c.Hostname+"/")
+		case model.ServiceCosmosDB:
+			return p.checkHTTP(ctx, "https://"+c.Hostname+"/")
+		case model.ServiceDatabase: // Azure SQL
+			return p.checkTCP(ctx, c.Hostname, 1433)
+		case model.ServicePostgres:
+			return p.checkTCP(ctx, c.Hostname, 5432)
+		case model.ServiceMySQL:
+			return p.checkTCP(ctx, c.Hostname, 3306)
+		case model.ServiceRedis:
+			return p.checkTCP(ctx, c.Hostname, 6380)
+		}
+	case model.ProviderGCP:
+		switch c.Service {
+		case model.ServiceObjectStorage:
+			return p.checkGCS(ctx, c)
+		case model.ServiceFirebaseDB:
+			return p.checkFirebase(ctx, c)
+		case model.ServiceWebApp:
+			return p.checkHTTP(ctx, "https://"+c.Hostname+"/")
+		}
+	case model.ProviderCloudflare:
+		return p.checkS3(ctx, c) // R2 is S3-compatible (and r2.dev serves objects)
+	case model.ProviderDigitalOcean:
+		if c.Service == model.ServiceObjectStorage {
+			return p.checkS3(ctx, c)
+		}
+		return p.checkTCP(ctx, c.Hostname, 5432)
+	case model.ProviderSupabase:
+		if c.Service == model.ServicePostgres {
+			return p.checkTCP(ctx, c.Hostname, 5432)
+		}
+		return p.checkHTTP(ctx, "https://"+c.Hostname+"/rest/v1/")
+	case model.ProviderOracle:
+		return p.checkHTTP(ctx, "https://"+c.Hostname+"/")
+	}
+	return p.checkHTTP(ctx, "https://"+c.Hostname+"/")
+}
+
+// checkS3 queries the S3 ListObjectsV2 anonymous endpoint. A 200 means the
+// bucket allows anonymous listing (public read); 403 means it exists but is not
+// public; 404 means no such bucket. 301/307 carries the real region.
+func (p *Prober) checkS3(ctx context.Context, c model.Candidate) (model.ExposureState, string) {
+	status, header, err := p.do(ctx, "https://"+c.Hostname+"/?list-type=2&max-keys=1")
 	if err != nil {
-		return model.ExposureUnknown
+		return classifyError(err)
+	}
+	if status == http.StatusMovedPermanently || status == http.StatusTemporaryRedirect || status == http.StatusPermanentRedirect {
+		if region := header.Get("x-amz-bucket-region"); region != "" {
+			return model.ExposureReachable, "s3 redirect region=" + region
+		}
+		return model.ExposureReachable, fmt.Sprintf("s3 redirect status=%d", status)
+	}
+	return classifyStatus(status, "s3")
+}
+
+// checkGCS uses the public JSON API to test object listing, which requires the
+// bucket to grant allUsers read access.
+func (p *Prober) checkGCS(ctx context.Context, c model.Candidate) (model.ExposureState, string) {
+	bucket := c.Resource
+	if bucket == "" {
+		bucket = c.Hostname
+	}
+	api := "https://storage.googleapis.com/storage/v1/b/" + url.PathEscape(bucket) + "/o?maxResults=1"
+	status, _, err := p.do(ctx, api)
+	if err != nil {
+		return classifyError(err)
+	}
+	return classifyStatus(status, "gcs")
+}
+
+// checkFirebase queries the Realtime Database REST endpoint with shallow=true so
+// only keys are returned. 200 means the security rules allow anonymous reads.
+func (p *Prober) checkFirebase(ctx context.Context, c model.Candidate) (model.ExposureState, string) {
+	status, _, err := p.do(ctx, "https://"+c.Hostname+"/.json?shallow=true")
+	if err != nil {
+		return classifyError(err)
+	}
+	return classifyStatus(status, "firebase")
+}
+
+func (p *Prober) checkHTTP(ctx context.Context, endpoint string) (model.ExposureState, string) {
+	status, _, err := p.do(ctx, endpoint)
+	if err != nil {
+		return classifyError(err)
+	}
+	return classifyStatus(status, "")
+}
+
+// checkTCP reports whether a database endpoint is publicly resolvable and its
+// port is open. It intentionally does not attempt any protocol handshake or
+// authentication, so it can never be reported as readable.
+func (p *Prober) checkTCP(ctx context.Context, host string, port int) (model.ExposureState, string) {
+	d := net.Dialer{Timeout: p.cfg.Timeout}
+	conn, err := d.DialContext(ctx, "tcp", net.JoinHostPort(host, fmt.Sprint(port)))
+	if err != nil {
+		return classifyError(err)
+	}
+	_ = conn.Close()
+	return model.ExposureReachable, fmt.Sprintf("tcp/%d open; no authentication attempted", port)
+}
+
+// do issues a single GET and reads at most a tiny prefix of the body before
+// closing it, so no object is ever downloaded.
+func (p *Prober) do(ctx context.Context, endpoint string) (int, http.Header, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+	if err != nil {
+		return 0, nil, err
 	}
 	resp, err := p.client.Do(req)
 	if err != nil {
-		var dnsErr *net.DNSError
+		return 0, nil, err
-		if errors.As(err, &dnsErr) {
-			return model.ExposurePrivate
-		}
-		return model.ExposureUnknown
 	}
 	defer resp.Body.Close()
+	_, _ = io.CopyN(io.Discard, resp.Body, 512)
+	return resp.StatusCode, resp.Header, nil
+}
 
-	switch {
+func classifyStatus(status int, tag string) (model.ExposureState, string) {
-	case resp.StatusCode >= 200 && resp.StatusCode < 300:
+	prefix := ""
-		return model.ExposurePublicRead
+	if tag != "" {
-	case resp.StatusCode == http.StatusForbidden || resp.StatusCode == http.StatusUnauthorized:
+		prefix = tag + " "
-		return model.ExposureAuthRequired
-	case resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusGone:
-		return model.ExposureNotFound
-	default:
-		return model.ExposureReachable
 	}
+	switch {
+	case status >= 200 && status < 300:
+		return model.ExposurePublicRead, fmt.Sprintf("%sstatus=%d anonymous listing allowed", prefix, status)
+	case status == http.StatusUnauthorized || status == http.StatusForbidden:
+		return model.ExposureAuthRequired, fmt.Sprintf("%sstatus=%d authentication required", prefix, status)
+	case status == http.StatusNotFound || status == http.StatusGone:
+		return model.ExposureNotFound, fmt.Sprintf("%sstatus=%d not found", prefix, status)
+	default:
+		return model.ExposureReachable, fmt.Sprintf("%sstatus=%d", prefix, status)
+	}
+}
+
+func classifyError(err error) (model.ExposureState, string) {
+	var dnsErr *net.DNSError
+	if errors.As(err, &dnsErr) {
+		if dnsErr.IsNotFound {
+			return model.ExposurePrivate, "dns: no public record"
+		}
+		return model.ExposureUnknown, "dns: " + dnsErr.Err
+	}
+	var netErr net.Error
+	if errors.As(err, &netErr) && netErr.Timeout() {
+		return model.ExposureUnknown, "timeout"
+	}
+	return model.ExposureUnknown, err.Error()
 }
 
 // Describe is a helper for logs/tests.

internal/probe/probe_test.go

@@ -1,7 +1,9 @@
 package probe
 
 import (
-	"crypto/tls"
+	"context"
+	"errors"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -11,20 +13,18 @@ import (
 	"tea.karlcom.de/karl/bucketeer/internal/model"
 )
 
-func newProber(t *testing.T, status int) (*Prober, string) {
+func serverHost(t *testing.T, h http.Handler) string {
 	t.Helper()
-	srv := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	srv := httptest.NewTLSServer(h)
-		w.WriteHeader(status)
-	}))
 	t.Cleanup(srv.Close)
-	p := New(Config{Workers: 1, Timeout: time.Second})
+	return strings.TrimPrefix(srv.URL, "https://")
-	// httptest uses a self-signed cert; the prober already skips verification.
-	_ = tls.Config{}
-	host := strings.TrimPrefix(srv.URL, "https://")
-	return p, host
 }
 
-func TestProbeClassification(t *testing.T) {
+func statusHandler(status int) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(status) })
+}
+
+func TestProbeStorageStatuses(t *testing.T) {
 	cases := []struct {
 		status int
 		want   model.ExposureState
@@ -35,11 +35,97 @@ func TestProbeClassification(t *testing.T) {
 		{http.StatusNotFound, model.ExposureNotFound},
 		{http.StatusInternalServerError, model.ExposureReachable},
 	}
-	for _, c := range cases {
+	for _, tc := range cases {
-		p, host := newProber(t, c.status)
+		p := New(Config{Workers: 1, Timeout: time.Second})
-		got := p.probe(t.Context(), model.Candidate{Hostname: host})
+		host := serverHost(t, statusHandler(tc.status))
-		if got != c.want {
+		got, detail := p.Probe(context.Background(), model.Candidate{
-			t.Errorf("status %d: got %s, want %s", c.status, got, c.want)
+			Hostname: host, Provider: model.ProviderAWS, Service: model.ServiceS3,
+		})
+		if got != tc.want {
+			t.Errorf("status %d: got %s (%s), want %s", tc.status, got, detail, tc.want)
 		}
 	}
 }
+
+func TestProbeS3RegionRedirect(t *testing.T) {
+	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("x-amz-bucket-region", "eu-central-1")
+		w.WriteHeader(http.StatusMovedPermanently)
+	})
+	p := New(Config{Workers: 1, Timeout: time.Second})
+	host := serverHost(t, h)
+	got, detail := p.Probe(context.Background(), model.Candidate{
+		Hostname: host, Provider: model.ProviderAWS, Service: model.ServiceS3,
+	})
+	if got != model.ExposureReachable || !strings.Contains(detail, "eu-central-1") {
+		t.Fatalf("got %s (%s), want reachable with region", got, detail)
+	}
+}
+
+func TestProbeFirebase(t *testing.T) {
+	p := New(Config{Workers: 1, Timeout: time.Second})
+	host := serverHost(t, statusHandler(http.StatusUnauthorized))
+	got, _ := p.Probe(context.Background(), model.Candidate{
+		Hostname: host, Provider: model.ProviderGCP, Service: model.ServiceFirebaseDB,
+	})
+	if got != model.ExposureAuthRequired {
+		t.Fatalf("got %s, want auth_required", got)
+	}
+	host2 := serverHost(t, statusHandler(http.StatusOK))
+	got, _ = p.Probe(context.Background(), model.Candidate{
+		Hostname: host2, Provider: model.ProviderGCP, Service: model.ServiceFirebaseDB,
+	})
+	if got != model.ExposurePublicRead {
+		t.Fatalf("got %s, want public_read", got)
+	}
+}
+
+func TestProbeDatabaseTCP(t *testing.T) {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			conn.Close()
+		}
+	}()
+	host, port, _ := net.SplitHostPort(ln.Addr().String())
+	p := New(Config{Workers: 1, Timeout: time.Second})
+	state, detail := p.checkTCP(context.Background(), host, mustAtoi(port))
+	if state != model.ExposureReachable {
+		t.Fatalf("got %s (%s), want reachable", state, detail)
+	}
+	if !strings.Contains(detail, "no authentication attempted") {
+		t.Fatalf("detail should be explicit about no auth: %q", detail)
+	}
+
+	// A closed port yields unknown, never readable.
+	state, _ = p.checkTCP(context.Background(), "127.0.0.1", 1)
+	if state == model.ExposurePublicRead {
+		t.Fatal("closed port must never be public_read")
+	}
+}
+
+func TestClassifyErrorNXDOMAIN(t *testing.T) {
+	state, detail := classifyError(&net.DNSError{Err: "no such host", IsNotFound: true})
+	if state != model.ExposurePrivate || !strings.Contains(detail, "no public record") {
+		t.Fatalf("got %s (%s)", state, detail)
+	}
+	if state, _ := classifyError(errors.New("boom")); state != model.ExposureUnknown {
+		t.Fatalf("got %s, want unknown", state)
+	}
+}
+
+func mustAtoi(s string) int {
+	n := 0
+	for _, c := range s {
+		n = n*10 + int(c-'0')
+	}
+	return n
+}

internal/store/store.go

@@ -138,9 +138,120 @@ func nonNil(s []string) []string {
 }
 
 // UpdateExposure records the outcome of an optional reachability probe.
-func (s *Store) UpdateExposure(ctx context.Context, provider, service, providerHostname string, state model.ExposureState) error {
+func (s *Store) UpdateExposure(ctx context.Context, provider, service, providerHostname string, state model.ExposureState, detail string) error {
-	_, err := s.pool.Exec(ctx,
+	_, err := s.pool.Exec(ctx, `
-		`UPDATE cloud_assets SET exposure_state = $4 WHERE provider = $1 AND service = $2 AND provider_hostname = $3`,
+		UPDATE cloud_assets
-		provider, service, providerHostname, state.String())
+		SET exposure_state = $4, exposure_detail = $5, probed_at = now()
+		WHERE provider = $1 AND service = $2 AND provider_hostname = $3`,
+		provider, service, providerHostname, state.String(), detail)
 	return err
 }
+
+// Asset is a row of the cloud_assets table for the read-only UI.
+type Asset struct {
+	ID             int64      `json:"id"`
+	Provider       string     `json:"provider"`
+	Service        string     `json:"service"`
+	Hostname       string     `json:"hostname"`
+	ProviderHost   string     `json:"provider_hostname"`
+	Resource       string     `json:"resource_identifier"`
+	Region         string     `json:"region"`
+	PublicSemantic string     `json:"public_semantic"`
+	Exposure       string     `json:"exposure_state"`
+	ExposureDetail string     `json:"exposure_detail"`
+	FirstSeen      time.Time  `json:"first_seen"`
+	LastSeen       time.Time  `json:"last_seen"`
+	ProbedAt       *time.Time `json:"probed_at"`
+}
+
+// AssetFilter selects assets for the UI. Empty fields are ignored.
+type AssetFilter struct {
+	Provider string
+	Service  string
+	Exposure string
+	Query    string
+	Limit    int
+	Offset   int
+}
+
+// ListAssets returns assets matching the filter, newest first.
+func (s *Store) ListAssets(ctx context.Context, f AssetFilter) ([]Asset, error) {
+	if f.Limit <= 0 || f.Limit > 500 {
+		f.Limit = 100
+	}
+	rows, err := s.pool.Query(ctx, `
+		SELECT id, provider, service, hostname, provider_hostname, resource_identifier,
+		       region, public_semantic, exposure_state, exposure_detail, first_seen, last_seen, probed_at
+		FROM cloud_assets
+		WHERE ($1 = '' OR provider = $1)
+		  AND ($2 = '' OR service = $2)
+		  AND ($3 = '' OR exposure_state = $3)
+		  AND ($4 = '' OR provider_hostname ILIKE '%' || $4 || '%' OR hostname ILIKE '%' || $4 || '%' OR resource_identifier ILIKE '%' || $4 || '%')
+		ORDER BY last_seen DESC
+		LIMIT $5 OFFSET $6`,
+		f.Provider, f.Service, f.Exposure, f.Query, f.Limit, f.Offset)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := []Asset{}
+	for rows.Next() {
+		var a Asset
+		if err := rows.Scan(&a.ID, &a.Provider, &a.Service, &a.Hostname, &a.ProviderHost,
+			&a.Resource, &a.Region, &a.PublicSemantic, &a.Exposure, &a.ExposureDetail,
+			&a.FirstSeen, &a.LastSeen, &a.ProbedAt); err != nil {
+			return nil, err
+		}
+		out = append(out, a)
+	}
+	return out, rows.Err()
+}
+
+// Count is a (label, count) pair for the UI summary.
+type Count struct {
+	Label string `json:"label"`
+	Count int64  `json:"count"`
+}
+
+// Stats summarizes the assets table.
+type Stats struct {
+	Total      int64   `json:"total"`
+	Readable   int64   `json:"readable"`
+	ByProvider []Count `json:"by_provider"`
+	ByService  []Count `json:"by_service"`
+	ByExposure []Count `json:"by_exposure"`
+}
+
+func (s *Store) Stats(ctx context.Context) (Stats, error) {
+	var st Stats
+	if err := s.pool.QueryRow(ctx, `SELECT count(*), count(*) FILTER (WHERE exposure_state = 'public_read') FROM cloud_assets`).Scan(&st.Total, &st.Readable); err != nil {
+		return st, err
+	}
+	group := func(column string) ([]Count, error) {
+		rows, err := s.pool.Query(ctx, `SELECT `+column+`, count(*) FROM cloud_assets GROUP BY 1 ORDER BY 2 DESC`)
+		if err != nil {
+			return nil, err
+		}
+		defer rows.Close()
+		var counts []Count
+		for rows.Next() {
+			var c Count
+			if err := rows.Scan(&c.Label, &c.Count); err != nil {
+				return nil, err
+			}
+			counts = append(counts, c)
+		}
+		return counts, rows.Err()
+	}
+	var err error
+	if st.ByProvider, err = group("provider"); err != nil {
+		return st, err
+	}
+	if st.ByService, err = group("service"); err != nil {
+		return st, err
+	}
+	if st.ByExposure, err = group("exposure_state"); err != nil {
+		return st, err
+	}
+	return st, nil
+}

internal/store/store_test.go

@@ -60,7 +60,13 @@ func TestIntegration(t *testing.T) {
 	if err := s.WriteFindings(ctx, []pipeline.Finding{f}); err != nil {
 		t.Fatal(err)
 	}
-	if err := s.UpdateExposure(ctx, model.ProviderAWS.String(), model.ServiceS3.String(), f.Hostname, model.ExposureReachable); err != nil {
+	if err := s.UpdateExposure(ctx, model.ProviderAWS.String(), model.ServiceS3.String(), f.Hostname, model.ExposureReachable, "test"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.ListAssets(ctx, AssetFilter{Provider: "aws", Limit: 10}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.Stats(ctx); err != nil {
 		t.Fatal(err)
 	}
 }

internal/webui/index.html

@@ -0,0 +1,123 @@
+<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width, initial-scale=1">
+<title>ctcloud · cloud assets</title>
+<style>
+  :root { --bg:#0f1115; --panel:#171a21; --line:#262b36; --fg:#e7e9ee; --mut:#9aa4b2; --accent:#5b9dff; }
+  * { box-sizing:border-box; }
+  body { margin:0; font:14px/1.45 ui-monospace,SFMono-Regular,Menlo,monospace; background:var(--bg); color:var(--fg); }
+  header { padding:16px 20px; border-bottom:1px solid var(--line); display:flex; align-items:baseline; gap:12px; flex-wrap:wrap; }
+  h1 { font-size:16px; margin:0; letter-spacing:.5px; }
+  header .mut { color:var(--mut); }
+  main { padding:20px; max-width:1400px; margin:0 auto; }
+  .cards { display:grid; grid-template-columns:repeat(auto-fit,minmax(140px,1fr)); gap:12px; margin-bottom:20px; }
+  .card { background:var(--panel); border:1px solid var(--line); border-radius:8px; padding:12px 14px; }
+  .card .n { font-size:22px; font-weight:600; }
+  .card .l { color:var(--mut); font-size:12px; text-transform:uppercase; letter-spacing:.5px; }
+  .filters { display:flex; gap:8px; flex-wrap:wrap; margin-bottom:14px; }
+  input,select,button { background:var(--panel); color:var(--fg); border:1px solid var(--line); border-radius:6px; padding:7px 10px; font:inherit; }
+  input { min-width:220px; }
+  button { cursor:pointer; }
+  button:hover { border-color:var(--accent); }
+  table { width:100%; border-collapse:collapse; font-size:13px; }
+  th,td { text-align:left; padding:7px 10px; border-bottom:1px solid var(--line); vertical-align:top; }
+  th { color:var(--mut); font-weight:500; position:sticky; top:0; background:var(--bg); }
+  tr:hover td { background:#141821; }
+  .pill { display:inline-block; padding:1px 7px; border-radius:999px; font-size:11px; border:1px solid var(--line); }
+  .public_read { color:#0b1; border-color:#0b1; }
+  .auth_required { color:#fd7; border-color:#fd7; }
+  .not_found, .private { color:#f77; border-color:#f77; }
+  .reachable { color:var(--accent); border-color:var(--accent); }
+  .unknown { color:var(--mut); }
+  .detail { color:var(--mut); font-size:11px; }
+  a { color:var(--accent); text-decoration:none; }
+  footer { color:var(--mut); padding:16px 20px; }
+</style>
+</head>
+<body>
+<header>
+  <h1>ctcloud</h1>
+  <span class="mut">cloud/database resources discovered in Certificate Transparency</span>
+  <span style="margin-left:auto" class="mut" id="updated">—</span>
+</header>
+<main>
+  <div class="cards" id="cards"></div>
+  <div class="filters">
+    <input id="q" placeholder="search hostname / resource">
+    <select id="provider" data-all="all providers"><option value="">all providers</option></select>
+    <select id="service" data-all="all services"><option value="">all services</option></select>
+    <select id="exposure" data-all="all exposure"><option value="">all exposure</option></select>
+    <button id="refresh">refresh</button>
+  </div>
+  <table>
+    <thead><tr>
+      <th>provider</th><th>service</th><th>resource</th><th>region</th>
+      <th>hostname</th><th>hostname (CT)</th><th>exposure</th><th>detail</th><th>last seen</th>
+    </tr></thead>
+    <tbody id="rows"></tbody>
+  </table>
+</main>
+<footer>
+  Detected endpoints are not automatically publicly accessible.
+  <span class="public_read">public_read</span> means an anonymous read succeeded at probe time.
+  <span class="reachable">reachable</span> on a database means the port was open; no authentication was attempted.
+</footer>
+<script>
+const $ = (id) => document.getElementById(id);
+const fill = (sel, values) => {
+  const cur = sel.value;
+  sel.innerHTML = '<option value="">' + sel.dataset.all + '</option>' +
+    values.map(v => `<option value="${v}">${v}</option>`).join('');
+  sel.value = cur;
+};
+function pill(v) { return `<span class="pill ${v}">${v || 'unknown'}</span>`; }
+function ago(ts) {
+  if (!ts) return '—';
+  const s = Math.max(0, (Date.now() - new Date(ts)) / 1000);
+  if (s < 60) return Math.floor(s) + 's ago';
+  if (s < 3600) return Math.floor(s/60) + 'm ago';
+  if (s < 86400) return Math.floor(s/3600) + 'h ago';
+  return Math.floor(s/86400) + 'd ago';
+}
+async function loadStats() {
+  const r = await fetch('api/stats'); if (!r.ok) return;
+  const s = await r.json();
+  $('cards').innerHTML = [
+    ['total assets', s.total], ['public read', s.readable],
+    ['providers', (s.by_provider||[]).length], ['services', (s.by_service||[]).length]
+  ].map(([l,n]) => `<div class="card"><div class="n">${n??0}</div><div class="l">${l}</div></div>`).join('');
+  if (!$('provider').dataset.filled) {
+    fill($('provider'), (s.by_provider||[]).map(x=>x.label));
+    fill($('service'), (s.by_service||[]).map(x=>x.label));
+    fill($('exposure'), (s.by_exposure||[]).map(x=>x.label));
+    ['provider','service','exposure'].forEach(id => $(id).dataset.filled = '1');
+  }
+}
+async function loadAssets() {
+  const p = new URLSearchParams({
+    q: $('q').value, provider: $('provider').value,
+    service: $('service').value, exposure: $('exposure').value, limit: 200
+  });
+  const r = await fetch('api/assets?' + p); if (!r.ok) return;
+  const rows = await r.json() || [];
+  $('rows').innerHTML = rows.length ? rows.map(a => `<tr>
+    <td>${a.provider}</td><td>${a.service}</td>
+    <td>${a.resource_identifier||''}</td><td>${a.region||''}</td>
+    <td>${a.provider_hostname}</td><td>${a.hostname}</td>
+    <td>${pill(a.exposure_state)}</td>
+    <td class="detail">${a.exposure_detail||''}</td>
+    <td class="detail">${ago(a.last_seen)}</td>
+  </tr>`).join('') : '<tr><td colspan="9" class="detail">no assets yet</td></tr>';
+  $('updated').textContent = 'updated ' + new Date().toLocaleTimeString();
+}
+async function refresh() { await Promise.all([loadStats(), loadAssets()]); }
+$('refresh').onclick = refresh;
+$('q').addEventListener('keydown', e => { if (e.key === 'Enter') loadAssets(); setTimeout(loadAssets, 0); });
+['provider','service','exposure'].forEach(id => $(id).addEventListener('change', loadAssets));
+refresh();
+setInterval(refresh, 15000);
+</script>
+</body>
+</html>

internal/webui/webui.go

@@ -0,0 +1,90 @@
+// Package webui serves a small read-only web UI over the discovered cloud
+// assets. It is intentionally dependency-free (stdlib + embedded HTML) and
+// exposes no mutation endpoints.
+package webui
+
+import (
+	"context"
+	_ "embed"
+	"encoding/json"
+	"net/http"
+	"strconv"
+	"strings"
+
+	"tea.karlcom.de/karl/bucketeer/internal/store"
+)
+
+//go:embed index.html
+var indexHTML []byte
+
+// Store is the read-only subset of the database the UI needs.
+type Store interface {
+	ListAssets(ctx context.Context, f store.AssetFilter) ([]store.Asset, error)
+	Stats(ctx context.Context) (store.Stats, error)
+}
+
+type Config struct {
+	User string // optional HTTP basic auth username
+	Pass string // optional HTTP basic auth password
+}
+
+// New returns the UI handler. If Config.User is set, all routes require basic auth.
+func New(s Store, cfg Config) http.Handler {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/" {
+			http.NotFound(w, r)
+			return
+		}
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		_, _ = w.Write(indexHTML)
+	})
+	mux.HandleFunc("/api/assets", func(w http.ResponseWriter, r *http.Request) {
+		q := r.URL.Query()
+		limit, _ := strconv.Atoi(q.Get("limit"))
+		offset, _ := strconv.Atoi(q.Get("offset"))
+		assets, err := s.ListAssets(r.Context(), store.AssetFilter{
+			Provider: strings.TrimSpace(q.Get("provider")),
+			Service:  strings.TrimSpace(q.Get("service")),
+			Exposure: strings.TrimSpace(q.Get("exposure")),
+			Query:    strings.TrimSpace(q.Get("q")),
+			Limit:    limit,
+			Offset:   offset,
+		})
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		writeJSON(w, assets)
+	})
+	mux.HandleFunc("/api/stats", func(w http.ResponseWriter, r *http.Request) {
+		st, err := s.Stats(r.Context())
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		writeJSON(w, st)
+	})
+
+	if cfg.User != "" {
+		return basicAuth(cfg.User, cfg.Pass, mux)
+	}
+	return mux
+}
+
+func writeJSON(w http.ResponseWriter, v any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	_ = json.NewEncoder(w).Encode(v)
+}
+
+func basicAuth(user, pass string, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		u, p, ok := r.BasicAuth()
+		if !ok || u != user || p != pass {
+			w.Header().Set("WWW-Authenticate", `Basic realm="ctcloud"`)
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}

internal/webui/webui_test.go

@@ -0,0 +1,94 @@
+package webui
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"tea.karlcom.de/karl/bucketeer/internal/store"
+)
+
+type fakeStore struct {
+	lastFilter store.AssetFilter
+}
+
+func (f *fakeStore) ListAssets(ctx context.Context, fl store.AssetFilter) ([]store.Asset, error) {
+	f.lastFilter = fl
+	return []store.Asset{{ID: 1, Provider: "aws", Service: "s3", ProviderHost: "b.s3.amazonaws.com", Exposure: "public_read"}}, nil
+}
+
+func (f *fakeStore) Stats(ctx context.Context) (store.Stats, error) {
+	return store.Stats{Total: 1, Readable: 1}, nil
+}
+
+func TestAPI(t *testing.T) {
+	fs := &fakeStore{}
+	srv := httptest.NewServer(New(fs, Config{}))
+	defer srv.Close()
+
+	resp, err := http.Get(srv.URL + "/api/assets?provider=aws&q=bucket&limit=5")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status = %d", resp.StatusCode)
+	}
+	var assets []store.Asset
+	if err := json.NewDecoder(resp.Body).Decode(&assets); err != nil {
+		t.Fatal(err)
+	}
+	if len(assets) != 1 || fs.lastFilter.Provider != "aws" || fs.lastFilter.Query != "bucket" || fs.lastFilter.Limit != 5 {
+		t.Fatalf("unexpected assets/filter: %+v %+v", assets, fs.lastFilter)
+	}
+
+	statsResp, err := http.Get(srv.URL + "/api/stats")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer statsResp.Body.Close()
+	var st store.Stats
+	if err := json.NewDecoder(statsResp.Body).Decode(&st); err != nil {
+		t.Fatal(err)
+	}
+	if st.Total != 1 {
+		t.Fatalf("stats = %+v", st)
+	}
+}
+
+func TestBasicAuth(t *testing.T) {
+	srv := httptest.NewServer(New(&fakeStore{}, Config{User: "u", Pass: "p"}))
+	defer srv.Close()
+
+	resp, _ := http.Get(srv.URL + "/api/stats")
+	if resp.StatusCode != http.StatusUnauthorized {
+		t.Fatalf("status = %d, want 401", resp.StatusCode)
+	}
+	resp.Body.Close()
+
+	req, _ := http.NewRequest(http.MethodGet, srv.URL+"/api/stats", nil)
+	req.SetBasicAuth("u", "p")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status = %d, want 200", resp.StatusCode)
+	}
+}
+
+func TestIndexServed(t *testing.T) {
+	srv := httptest.NewServer(New(&fakeStore{}, Config{}))
+	defer srv.Close()
+	resp, err := http.Get(srv.URL + "/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if ct := resp.Header.Get("Content-Type"); ct != "text/html; charset=utf-8" {
+		t.Fatalf("content-type = %q", ct)
+	}
+}

migrations/0001_schema.sql

@@ -19,6 +19,11 @@ CREATE TABLE IF NOT EXISTS cloud_assets (
 
 CREATE INDEX IF NOT EXISTS cloud_assets_last_seen_idx ON cloud_assets (last_seen);
 
+-- Reachability probe results (added after the initial schema; ALTER keeps this
+-- idempotent for existing databases).
+ALTER TABLE cloud_assets ADD COLUMN IF NOT EXISTS exposure_detail TEXT        NOT NULL DEFAULT '';
+ALTER TABLE cloud_assets ADD COLUMN IF NOT EXISTS probed_at       TIMESTAMPTZ;
+
 CREATE TABLE IF NOT EXISTS observations (
     id              BIGSERIAL PRIMARY KEY,
     asset_id        BIGINT      NOT NULL REFERENCES cloud_assets (id) ON DELETE CASCADE,