Refuse [::], 0.0.0.0, IPv6 multicast and documentation space (closes #341)

On Linux a connection to the unspecified address [::] or 0.0.0.0
reaches the host's own loopback, and the SSRF guard let [::] through.
Both unspecified addresses now sit in alwaysBlockedNetworks, so an
allowlist reaches loopback only through an entry that covers a
loopback address, never through one that covers only 0.0.0.0 or ::;
::/128 joins the default blocklist beside 0.0.0.0/8. IPv6 multicast
(ff00::/8) and documentation space (2001:db8::/32) are refused by
default. Every default blocklist entry gets a one-line comment, and the
README, the rules above each list, the two pinning tests and the
allowlist refusal test follow.

Model: opus-5-5

README.md

@@ -248,8 +248,11 @@ Two things this setting cannot do:
 
   The unspecified addresses `0.0.0.0` and `::` hand out nothing
   themselves, but no host can have either, and on Linux a connection to
-  one reaches this host's own loopback. They are listed so that the only
-  way to open loopback is to name it, as `127.0.0.0/8` or `::1`.
+  one reaches this host's own loopback. They are listed so that an
+  allowlist reaches loopback only through an entry that covers a loopback
+  address, such as `127.0.0.0/8`, `::1` or `0.0.0.0/0`, never through one
+  that covers only `0.0.0.0` or `::`; `0.0.0.0/8`, for example, does not
+  open loopback.
 
   The six ULA entries, all inside `fd00::/8`, are why this matters in
   practice: `fd00::/8` is an ordinary block to allowlist for your own

TODO.md

@@ -40,12 +40,6 @@ duplicate. That is deliberate — the alternative is a silent lost
 delivery — and the README says so under Rationale. It is not a defect
 to re-file.
 
-One caveat on reading a green check: a docs-only commit deliberately
-replays from the layer cache
-(https://git.eeqj.de/sneak/webhooker/issues/119), so a green status on
-such a commit evidences a replay rather than an executed run. A code
-commit invalidates the `COPY` layer and genuinely executes.
-
 # Next Step
 
 Clear the rest of the open 1.0.0 milestone

internal/delivery/engine.go

@@ -14,6 +14,7 @@ import (
 	"go.uber.org/fx"
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/globals"
 	"sneak.berlin/go/webhooker/internal/lifecycle"
 	"sneak.berlin/go/webhooker/internal/logger"
 	"sneak.berlin/go/webhooker/internal/metrics"
@@ -146,6 +147,7 @@ type EngineParams struct {
 
 	DB        *database.Database
 	DBManager *database.WebhookDBManager
+	Globals   *globals.Globals
 	Logger    *logger.Logger
 	SSRFGuard *Guard
 	Metrics   *metrics.Set
@@ -168,6 +170,10 @@ type Engine struct {
 	retryCh    chan Task
 	workers    int
 
+	// version is the running build's version, the one the web UI
+	// footer shows. userAgent puts it on every outbound request.
+	version string
+
 	// mtr is the delivery metric set. Production wires the one
 	// registered on the registry /metrics serves; a test can
 	// substitute a set registered on a registry it holds, so it can
@@ -205,6 +211,7 @@ func New(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    defaultWorkers,
+		version:    params.Globals.Version,
 		mtr:        params.Metrics,
 	}
 
@@ -301,6 +308,13 @@ func (e *Engine) ScheduleRetry(
 	})
 }
 
+// userAgent is the User-Agent header of every http and slack
+// delivery request: the program name and the running build's
+// version.
+func (e *Engine) userAgent() string {
+	return "webhooker/" + e.version
+}
+
 // registerHooks wires the engine's start and stop into the fx
 // lifecycle. The start hook's context is deliberately ignored
 // (see start for why the worker pool must not inherit it); the

internal/delivery/engine_test.go

@@ -1247,11 +1247,6 @@ func TestDoHTTPRequest_ForwardsHeaders(t *testing.T) {
 		testContentType,
 		receivedHeaders.Get("Content-Type"),
 	)
-
-	assert.Equal(t,
-		"webhooker/1.0",
-		receivedHeaders.Get("User-Agent"),
-	)
 }
 
 // The event's stored inbound headers carry the same Content-Type the
@@ -1320,6 +1315,7 @@ func TestApplyRequestHeaders_SendsOneContentType(t *testing.T) {
 					ContentType: tc.event,
 				},
 				cfg,
+				"webhooker/dev",
 			)
 
 			assert.Equal(t,

internal/delivery/export_test.go

@@ -83,8 +83,9 @@ func ExportApplyRequestHeaders(
 	req *http.Request,
 	event *database.Event,
 	cfg *HTTPTargetConfig,
+	userAgent string,
 ) []string {
-	return applyRequestHeaders(req, event, cfg)
+	return applyRequestHeaders(req, event, cfg, userAgent)
 }
 
 // ExportTruncate exposes truncate for testing.

internal/delivery/redirect_test.go

@@ -375,6 +375,7 @@ func TestApplyRequestHeaders_ReportsOriginScopedNames(t *testing.T) {
 				"Content-Type":  testContentType,
 			},
 		},
+		"webhooker/dev",
 	)
 
 	assert.Equal(t,

internal/delivery/ssrf.go

@@ -116,9 +116,12 @@ var blockedPublicNetworks []*net.IPNet
 //
 // The unspecified addresses 0.0.0.0 and :: fail (2) and are here
 // anyway. No host can have either, and on Linux a connection to
-// one reaches this host's own loopback, so an allowlist opens
-// loopback only by naming it (127.0.0.0/8, ::1/128). Nothing else
-// lives at either address, so refusing them costs nothing.
+// one reaches this host's own loopback. Listing them means an
+// allowlist reaches loopback only through an entry that covers a
+// loopback address (127.0.0.0/8, ::1/128, 0.0.0.0/0), never
+// through one that covers only 0.0.0.0 or :: (0.0.0.0/8, for
+// example). Nothing else lives at either address, so refusing
+// them costs nothing.
 //
 // Every entry is either already in blockedNetworks — this list is
 // what makes it unconditional — or an alternate encoding of

internal/delivery/ssrf_allowlist_test.go

@@ -168,12 +168,13 @@ func TestGuardAllowlist_UnlistedPrivateStillRefused(t *testing.T) {
 
 // TestGuardAllowlist_MetadataAlwaysRefused is the load-bearing
 // case: cloud instance metadata endpoints are credential theft
-// rather than delivery to an internal service, so no allowlist
-// reaches one. Every guard below names a CIDR that covers its
-// target — including 0.0.0.0/0, ::/0, and the ordinary ULA and
-// CGNAT blocks an operator would really list — and the address
-// must stay refused anyway, on both the validation and the
-// delivery path.
+// rather than delivery to an internal service, and the
+// unspecified addresses 0.0.0.0 and :: reach this host's loopback
+// on Linux, so no allowlist reaches any of them. Every guard
+// below names a CIDR that covers its target — including
+// 0.0.0.0/0, ::/0, and the ordinary ULA and CGNAT blocks an
+// operator would really list — and the address must stay
+// refused anyway, on both the validation and the delivery path.
 func TestGuardAllowlist_MetadataAlwaysRefused(t *testing.T) {
 	t.Parallel()
 
@@ -219,15 +220,17 @@ type metadataAlwaysRefusedCase struct {
 }
 
 // metadataAlwaysRefusedCases enumerates every unconditionally
-// blocked address together with an allowlist entry that would
-// otherwise reach it. Split by family of address only to stay
-// under the function-length limit.
+// blocked address (link-local, the cloud metadata endpoints and
+// the unspecified addresses) together with an allowlist entry
+// that would otherwise reach it. Split by family of address only
+// to stay under the function-length limit.
 func metadataAlwaysRefusedCases() []metadataAlwaysRefusedCase {
 	cases := linkLocalRefusedCases()
 	cases = append(cases, ulaMetadataRefusedCases()...)
 	cases = append(cases, ipv4MetadataRefusedCases()...)
+	cases = append(cases, encodedMetadataRefusedCases()...)
 
-	return append(cases, encodedMetadataRefusedCases()...)
+	return append(cases, unspecifiedRefusedCases()...)
 }
 
 // linkLocalRefusedCases covers the link-local blocks, including
@@ -367,6 +370,23 @@ func encodedMetadataRefusedCases() []metadataAlwaysRefusedCase {
 	}
 }
 
+// unspecifiedRefusedCases covers the unspecified addresses, each
+// of which reaches this host's loopback on Linux.
+func unspecifiedRefusedCases() []metadataAlwaysRefusedCase {
+	return []metadataAlwaysRefusedCase{
+		{
+			name:   "IPv4 unspecified address under 0.0.0.0/0",
+			allow:  allowAllIPv4,
+			target: "http://0.0.0.0:8080/hook",
+		},
+		{
+			name:   "IPv6 unspecified address under ::/0",
+			allow:  allowAllIPv6,
+			target: "http://[::]:8080/hook",
+		},
+	}
+}
+
 // TestGuardAllowlist_PublicUnaffected asserts the allowlist does
 // not narrow anything: public addresses were reachable before it
 // existed and stay reachable, whether or not a list is set.

internal/delivery/target_http.go

@@ -442,7 +442,9 @@ func (t *httpTarget) doHTTPRequest(
 		)
 	}
 
-	originScoped := applyRequestHeaders(req, event, cfg)
+	originScoped := applyRequestHeaders(
+		req, event, cfg, t.eng.userAgent(),
+	)
 
 	client := t.clientForRequest(cfg, originScoped)
 
@@ -562,10 +564,13 @@ func isForwardableHeader(name string) bool {
 // Content-Type goes out once: a Content-Type configured on the target
 // wins, otherwise the event's ContentType, otherwise none. The inbound
 // Content-Type in the event's headers is never forwarded.
+//
+// userAgent is set last, over any configured or inbound User-Agent.
 func applyRequestHeaders(
 	req *http.Request,
 	event *database.Event,
 	cfg *HTTPTargetConfig,
+	userAgent string,
 ) []string {
 	if event.ContentType != "" {
 		req.Header.Set(
@@ -580,7 +585,7 @@ func applyRequestHeaders(
 		originScoped[http.CanonicalHeaderKey(k)] = struct{}{}
 	}
 
-	req.Header.Set("User-Agent", "webhooker/1.0")
+	req.Header.Set("User-Agent", userAgent)
 
 	// A Content-Type configured on the target describes the body
 	// being sent rather than the sender. A 307/308 preserves the

internal/delivery/target_slack.go

@@ -136,7 +136,7 @@ func (t *slackTarget) attempt(
 	}
 
 	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("User-Agent", "webhooker/1.0")
+	req.Header.Set("User-Agent", t.eng.userAgent())
 
 	resp, doErr := executeHTTPRequest(t.client, req)
 	durationMs := time.Since(start).Milliseconds()

internal/delivery/user_agent_test.go

@@ -0,0 +1,91 @@
+package delivery_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/fx/fxtest"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+	"sneak.berlin/go/webhooker/internal/globals"
+	"sneak.berlin/go/webhooker/internal/logger"
+	"sneak.berlin/go/webhooker/internal/metrics"
+)
+
+// Both the http and the slack target send webhooker/ and the version
+// in Globals, the value the web UI footer shows. A User-Agent
+// configured on the target or carried in by the sender does not
+// replace it.
+func TestUserAgent_IsTheBuildVersion(t *testing.T) {
+	t.Parallel()
+
+	const want = "webhooker/1.2.3-test"
+
+	userAgents := make(chan string, 1)
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			userAgents <- r.Header.Get("User-Agent")
+
+			w.WriteHeader(http.StatusOK)
+		},
+	))
+	defer ts.Close()
+
+	g := &globals.Globals{Version: "1.2.3-test"}
+	lc := fxtest.NewLifecycle(t)
+
+	log, err := logger.New(lc, logger.LoggerParams{Globals: g})
+	require.NoError(t, err)
+
+	e := delivery.New(lc, delivery.EngineParams{
+		Globals: g,
+		Logger:  log,
+		// httptest listens on loopback, which the default guard
+		// refuses.
+		SSRFGuard: delivery.NewTestGuard(
+			netip.MustParsePrefix("127.0.0.0/8"),
+		),
+		Metrics: metrics.New(prometheus.NewRegistry()),
+	})
+
+	statusCode, _, _, err := e.ExportDoHTTPRequest(
+		context.Background(),
+		&delivery.HTTPTargetConfig{
+			URL:     ts.URL,
+			Headers: map[string]string{"User-Agent": "configured/1"},
+		},
+		&database.Event{Headers: `{"User-Agent":["curl/8"]}`},
+	)
+	require.NoError(t, err)
+	require.Equal(t, http.StatusOK, statusCode)
+	require.Len(t, userAgents, 1, "the http target sent no request")
+	assert.Equal(t, want, <-userAgents, "http target")
+
+	db := testWebhookDB(t)
+	targetID := uuid.New().String()
+
+	slackCfg, err := json.Marshal(
+		delivery.SlackTargetConfig{WebhookURL: ts.URL},
+	)
+	require.NoError(t, err)
+
+	event := seedEvent(t, db, `{"action":"test"}`)
+	dlv := seedDelivery(
+		t, db, event.ID, targetID, database.DeliveryStatusPending,
+	)
+
+	e.ExportDeliverSlack(context.Background(), db, buildSlackDelivery(
+		dlv, event, targetID, "test-slack", string(slackCfg),
+	))
+	require.Len(t, userAgents, 1, "the slack target sent no request")
+	assert.Equal(t, want, <-userAgents, "slack target")
+}

internal/handlers/source_detail_test.go

@@ -241,3 +241,37 @@ func TestHandleSourceDetail_RendersNamedTargetFields(
 	assert.Contains(t, body, "(unavailable)")
 	assert.NotContains(t, body, "beak")
 }
+
+// TestHandleSourceDetail_FitsWideAndNarrowWindows pins the webhook
+// page's maximum width at 108rem (1728 px), half again the 72rem of
+// max-w-6xl that the webhook list and the event log use, so an
+// entrypoint URL fits on one line in a 1920-pixel window; and the
+// wrapping of its title row, so the buttons beside the title do not
+// push a phone-width window into scrolling sideways.
+func TestHandleSourceDetail_FitsWideAndNarrowWindows(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h    *handlers.Handlers
+		sess *session.Session
+		db   *database.Database
+	)
+
+	app := newTestApp(t, &h, &sess, &db)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+
+	body := renderSourceDetailPage(t, h, sess, wh.ID)
+
+	assert.Contains(
+		t, body,
+		`<div class="mx-auto px-6 py-8" style="max-width: 108rem"`,
+	)
+	assert.Contains(
+		t, body,
+		`<div class="flex flex-wrap justify-between items-center gap-2 mt-2">`,
+	)
+}

templates/source_detail.html

@@ -3,10 +3,14 @@
 {{define "title"}}{{.Webhook.Name}} - Webhooker{{end}}
 
 {{define "content"}}
-<div class="max-w-6xl mx-auto px-6 py-8" x-data="{ showAddEntrypoint: false, showAddTarget: false }">
+<!-- 108rem, half again the 72rem (max-w-6xl) of the webhook list, the
+     event log, the navbar and the footer, so an entrypoint URL fits on
+     one line. An inline style, because the committed tailwind.css has
+     no class this wide. -->
+<div class="mx-auto px-6 py-8" style="max-width: 108rem" x-data="{ showAddEntrypoint: false, showAddTarget: false }">
     <div class="mb-6">
         <a href="/hooks" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to webhooks</a>
-        <div class="flex justify-between items-center mt-2">
+        <div class="flex flex-wrap justify-between items-center gap-2 mt-2">
             <div>
                 <h1 class="text-2xl font-medium text-gray-900">{{.Webhook.Name}}</h1>
                 {{if .Webhook.Description}}