Bound the access log line against client-chosen text (closes #146)

The access log wrote one INFO line per request carrying
r.URL.String(). Registered with Use, it runs ahead of the route
limiter, so a client flooding the unauthenticated receiver with
invented paths wrote attacker-chosen text of attacker-chosen length
into the operator's log, one line per request.

3xx and 4xx responses now log the chi route pattern in place of the
concrete URL, and the fixed literal "(unmatched)" when routing matched
nothing at all. One line per request is retained, so real traffic
stays observable and rate accounting still works, but the line's
content is now bounded by the service's own route table. The pattern
is only populated after routing, so it is read in the deferred part of
the handler rather than before next.ServeHTTP.

The route pattern alone does not close the hole, because it leaves two
other ways for a request to choose the size of the line it writes.

The query string is one: /.well-known/healthcheck and /s/* answer 200
to anyone with no rate limiter in front of them, and /pages/login
behind only the login limiter, so appending 8 KB after the '?' bought
the same amplification as an invented 404 path. The branches that keep
the concrete URL now log the path only, with the query replaced by the
fixed marker "?(redacted)". Nothing debuggable is lost: `page`, on the
authenticated pagination links, is the only query parameter this
service reads.

The headers are the other: useragent and referer are logged on every
line, including the correctly redacted ones, so an 8 KB User-Agent
plus an 8 KB Referer produced a 24 KB line whose url field read
"(unmatched)". Each field a client supplies is now truncated rather
than dropped -- a truncated User-Agent is still worth reading -- to
512 bytes for url, useragent and referer, 128 for request_id (chi
passes an inbound X-Request-Id header straight through), and 32 for
method, which Go accepts as any token up to the header size limit.
Truncation also drops invalid UTF-8, which a JSON encoder would
otherwise expand six-fold past the budget.

A complete line is now at most 2,560 bytes, which the tests assert
against a request carrying 8 KB in the query and 8 KB in each of three
headers, and which the README states so an operator can size log
storage against it.

README.md

@@ -914,14 +914,34 @@ no route at all — in place of the concrete URL. Those are the outcomes
 an unauthenticated client can drive for free: 404 and 429 on any
 invented receiver path, a login redirect on any invented profile path.
 Logging the URL there would let a flood write text of its own choosing,
-at a length of its own choosing, into the log. The pattern comes from
-the service's own route table, so an operator sizing log storage can
-multiply a fixed per-line cost by the request rate the rate limits
-allow. 2xx and 5xx responses keep the full URL, query string included:
-a success resolved against a static route or against the operator's own
-data (on the receiver, against a stored entrypoint UUID), and a 5xx is
-a bug in this service, where the exact URL is the evidence and no
-client can provoke one at will.
+at a length of its own choosing, into the log. 2xx and 5xx responses
+keep the concrete path — a success resolved against a static route or
+against the operator's own data (on the receiver, against a stored
+entrypoint UUID), and a 5xx is a bug in this service, where the exact
+path is the evidence and no client can provoke one at will.
+
+The query string is never logged; it is replaced by the fixed marker
+`?(redacted)`. It is client-chosen on every route, and
+`/.well-known/healthcheck` and `/s/*` answer 200 to anyone with no rate
+limiter in front of them, so a query on a fixed 200 URL would otherwise
+buy the same amplification as an invented path. Nothing debuggable is
+lost: `page`, on the authenticated pagination links, is the only query
+parameter this service reads.
+
+The remaining client-supplied fields are truncated rather than dropped,
+each to a fixed budget: 512 bytes for `url`, `useragent` and `referer`,
+128 for `request_id` (chi passes an inbound `X-Request-Id` header
+through), and 32 for `method`. A truncated `User-Agent` is still worth
+reading; an absent one is not. A cut value ends in `[truncated]`.
+
+Net: **one `INFO` line per request, of at most 2,560 bytes** —
+`internal/middleware/accesslog_test.go` asserts that ceiling against a
+request carrying an 8 KB query, an 8 KB `User-Agent`, an 8 KB `Referer`
+and an 8 KB `X-Request-Id`, which together produce a 1,460-byte line.
+Multiply that ceiling by the request rate to size log storage. Note
+that the rate is not bounded by the limits above on every route:
+`/.well-known/healthcheck` and `/s/*` sit behind no limiter, so there
+the multiplier is whatever the deployment will serve.
 
 Every limiter here — receiver, login, and password change — identifies
 the client the same way, through one shared key function: the

internal/delivery/target_config_view.go

@@ -106,6 +106,12 @@ func slackConfigFields(configJSON string) []ConfigField {
 // and its retry settings. Header values are not shown — they
 // routinely carry authorization tokens — only how many are
 // configured.
+//
+// The destination is masked to scheme and host by the same
+// rule the Slack target uses. An HTTP target's destination is
+// commonly a Slack, Discord or Teams incoming-webhook endpoint
+// whose path segments are the credential, and the field takes
+// an arbitrary URL, so no segment can be assumed non-secret.
 func httpConfigFields(t *database.Target) []ConfigField {
 	cfg, err := parseHTTPConfig(t.Config)
 	if err != nil {
@@ -114,7 +120,7 @@ func httpConfigFields(t *database.Target) []ConfigField {
 
 	fields := []ConfigField{{
 		Label: "Destination URL",
-		Value: cfg.URL,
+		Value: MaskURL(cfg.URL),
 	}}
 
 	if cfg.Timeout > 0 {

internal/delivery/target_config_view_test.go

@@ -19,6 +19,7 @@ const (
 
 	viewExampleOrigin = "https://example.com"
 	viewExampleHook   = viewExampleOrigin + "/hook"
+	viewMaskedOrigin  = viewExampleOrigin + "/..."
 	viewUnavailable   = "(unavailable)"
 	viewExpiryNever   = "never"
 )
@@ -162,7 +163,7 @@ func TestNewTargetViews_HTTP(t *testing.T) {
 	assert.Equal(
 		t,
 		map[string]string{
-			"Destination URL": viewExampleHook,
+			"Destination URL": viewMaskedOrigin,
 			"Timeout":         "30s",
 			"Headers":         "1 configured",
 			"Max Retries":     "5",
@@ -188,13 +189,41 @@ func TestNewTargetViews_HTTPFireAndForget(t *testing.T) {
 	assert.Equal(
 		t,
 		map[string]string{
-			"Destination URL": viewExampleHook,
+			"Destination URL": viewMaskedOrigin,
 			"Max Retries":     "0 (fire-and-forget)",
 		},
 		fieldMap(view.Config),
 	)
 }
 
+// TestNewTargetViews_HTTPMasksDestinationURL proves the rule
+// holds for the http target too: an http destination is
+// routinely an incoming-webhook endpoint whose path segments
+// are the credential, so none of them is shown.
+func TestNewTargetViews_HTTPMasksDestinationURL(t *testing.T) {
+	t.Parallel()
+
+	view := viewFor(t, database.Target{
+		Type:   database.TargetTypeHTTP,
+		Config: `{"url":"` + slackWebhookURL + `"}`,
+	})
+
+	fields := fieldMap(view.Config)
+
+	assert.Equal(
+		t,
+		"https://hooks.slack.com/...",
+		fields["Destination URL"],
+	)
+
+	for _, v := range fields {
+		assert.NotContains(t, v, slackSecretPath)
+		assert.NotContains(t, v, "T00000000")
+		assert.NotContains(t, v, "B00000000")
+		assert.NotContains(t, v, "XXXXXXXXXXXXXXXXXXXXXXXX")
+	}
+}
+
 func TestNewTargetViews_Database(t *testing.T) {
 	t.Parallel()
 

internal/handlers/event_log_view.go

@@ -0,0 +1,120 @@
+package handlers
+
+import (
+	"time"
+	"unicode/utf8"
+)
+
+// maxRenderedBodyBytes caps how many bytes of a stored event
+// body reach the event log page. Bodies come from the
+// unauthenticated receiver under the 1 MB ingest cap and
+// renderTemplate buffers a whole page before writing it, so
+// an uncapped page of paginationPerPage events is tens of
+// megabytes of resident memory per concurrent viewer.
+const maxRenderedBodyBytes = 8192
+
+// eventLogColumns is the event log's projection. The casts to
+// blob are load-bearing: they make substr and length count
+// bytes rather than characters, so the cap bounds the page in
+// bytes whatever the payload's encoding. Cutting in SQLite
+// rather than in Go is the point of the projection — an
+// oversized body never becomes a Go string at all.
+const eventLogColumns = "id, created_at, method, content_type, " +
+	"substr(cast(body as blob), 1, ?) AS body, " +
+	"length(cast(body as blob)) AS body_bytes"
+
+// EventLogView is the display-safe projection of an event for
+// the event log page, alongside DeliveryView and TargetView.
+// It carries a capped body plus the true stored size, so the
+// page can mark a body as truncated without ever holding the
+// whole thing.
+type EventLogView struct {
+	ID          string
+	CreatedAt   time.Time
+	Method      string
+	ContentType string
+
+	// Body holds at most maxRenderedBodyBytes bytes of the
+	// stored body.
+	Body string
+
+	// BodyBytes is the true size of the stored body.
+	BodyBytes int64
+
+	// BodyTruncated reports that the stored body was larger
+	// than the cap, so the page owes the reader a marker.
+	BodyTruncated bool
+
+	Deliveries []DeliveryView
+}
+
+// BodyShownBytes is how many body bytes the page is actually
+// rendering, which the truncation marker reports beside the
+// true size.
+func (v EventLogView) BodyShownBytes() int {
+	return len(v.Body)
+}
+
+// eventLogRow is one row of the event log projection. Its
+// body column arrives already cut to the cap by SQLite, with
+// the true size beside it.
+type eventLogRow struct {
+	ID          string
+	CreatedAt   time.Time
+	Method      string
+	ContentType string
+	Body        []byte
+	BodyBytes   int64
+}
+
+// view projects a loaded row for rendering.
+func (r *eventLogRow) view() EventLogView {
+	body := r.Body
+	truncated := r.BodyBytes > int64(len(body))
+
+	// Only a cut body can have been left mid-sequence by
+	// this query. A whole body is passed through exactly as
+	// stored, however malformed.
+	if truncated {
+		body = trimPartialRune(body)
+	}
+
+	return EventLogView{
+		ID:            r.ID,
+		CreatedAt:     r.CreatedAt,
+		Method:        r.Method,
+		ContentType:   r.ContentType,
+		Body:          string(body),
+		BodyBytes:     r.BodyBytes,
+		BodyTruncated: truncated,
+	}
+}
+
+// trimPartialRune drops a trailing UTF-8 sequence that the
+// byte-wise cut left incomplete, so a multi-byte rune severed
+// at the cap does not surface as a mojibake tail.
+//
+// Bytes that are merely invalid UTF-8 are left exactly as
+// stored: this service receives binary payloads, and rewriting
+// them would misreport what was delivered. The distinction is
+// utf8.FullRune's — it reports a complete sequence for an
+// invalid encoding too, since that decodes to a width-1 error
+// rune, so only a valid prefix still waiting for its
+// continuation bytes is removed. A tail with no rune start in
+// its last utf8.UTFMax bytes cannot be an incomplete sequence
+// either, and is likewise left alone.
+func trimPartialRune(b []byte) []byte {
+	for i := len(b) - 1; i >= 0 && len(b)-i <= utf8.UTFMax; i-- {
+		if !utf8.RuneStart(b[i]) {
+			continue
+		}
+
+		if utf8.FullRune(b[i:]) {
+			return b
+		}
+
+		return b[:i]
+	}
+
+	return b
+}

internal/handlers/event_log_view_test.go

@@ -0,0 +1,258 @@
+package handlers_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+	"unicode/utf8"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm/clause"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/handlers"
+	"sneak.berlin/go/webhooker/internal/session"
+)
+
+// bodyCap is the number of body bytes the event log page is
+// allowed to render for one event.
+const bodyCap = handlers.MaxRenderedBodyBytesForTest
+
+// snowman is a three-byte rune, so a body of them straddles the
+// byte-wise cut: bodyCap is not a multiple of three.
+const snowman = "☃"
+
+// seedEventWithBody records one event with the given body in the
+// webhook's own database.
+func seedEventWithBody(
+	t *testing.T,
+	dbMgr *database.WebhookDBManager,
+	webhookID string,
+	body string,
+) {
+	t.Helper()
+
+	webhookDB, err := dbMgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	event := &database.Event{
+		WebhookID:   webhookID,
+		Method:      http.MethodPost,
+		Body:        body,
+		ContentType: "application/octet-stream",
+	}
+
+	require.NoError(t, webhookDB.Omit(
+		clause.Associations,
+	).Create(event).Error)
+}
+
+// seedAndProject stores one body and returns the projection the
+// event log page would be handed for it.
+func seedAndProject(
+	t *testing.T,
+	body string,
+) handlers.EventLogView {
+	t.Helper()
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	seedEventWithBody(t, dbMgr, wh.ID, body)
+
+	views := h.LoadEventLogViewsForTest(
+		httptest.NewRecorder(), *wh, 1,
+	)
+	require.Len(t, views, 1)
+
+	return views[0]
+}
+
+// TestHandleSourceLogs_BoundsOversizeBody proves the rendered
+// page is bounded by the cap rather than by the stored payload:
+// the body here is 64 times the cap, and the ingest path would
+// accept twice as much again.
+func TestHandleSourceLogs_BoundsOversizeBody(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	const (
+		sentinel    = "TAIL-SENTINEL-1f4a9c"
+		storedBytes = 512 * 1024
+	)
+
+	wh := seedWebhook(t, db)
+	seedEventWithBody(
+		t, dbMgr, wh.ID,
+		strings.Repeat("A", storedBytes-len(sentinel))+sentinel,
+	)
+
+	page := renderSourceLogsPage(t, h, sess, wh.ID)
+
+	// Nothing past the cap reaches the page, and the whole page
+	// stays far below the stored body it is reporting on.
+	assert.NotContains(t, page, sentinel)
+	assert.Less(t, len(page), 4*bodyCap)
+
+	// The marker states the true stored size, not the cut one.
+	assert.Contains(
+		t, page,
+		"showing "+strconv.Itoa(bodyCap)+
+			" of "+strconv.Itoa(storedBytes)+" bytes",
+	)
+}
+
+// TestHandleSourceLogs_SmallBodyRendersWhole guards the other
+// side of the cap: a body under it is shown in full and carries
+// no truncation marker.
+func TestHandleSourceLogs_SmallBodyRendersWhole(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	seedEventWithBody(t, dbMgr, wh.ID, `{"kept":"whole"}`)
+
+	page := renderSourceLogsPage(t, h, sess, wh.ID)
+
+	assert.Contains(t, page, ""kept"")
+	assert.NotContains(t, page, "Body truncated for display")
+}
+
+// TestEventLogView_CutMidRune proves a multi-byte rune severed
+// by the byte-wise cut is dropped rather than surfaced as a
+// mojibake tail.
+func TestEventLogView_CutMidRune(t *testing.T) {
+	t.Parallel()
+
+	body := strings.Repeat(snowman, 4096)
+	view := seedAndProject(t, body)
+
+	// bodyCap bytes hold bodyCap/3 whole snowmen and two bytes
+	// of the next one; those two are dropped.
+	whole := bodyCap / len(snowman)
+
+	assert.True(t, view.BodyTruncated)
+	assert.Equal(t, int64(len(body)), view.BodyBytes)
+	assert.Equal(t, strings.Repeat(snowman, whole), view.Body)
+	assert.True(t, utf8.ValidString(view.Body))
+	assert.LessOrEqual(t, len(view.Body), bodyCap)
+}
+
+// TestEventLogView_BinaryBodyLeftAsStored proves a binary
+// payload is passed through byte for byte. Its tail is invalid
+// UTF-8 however the cut falls, so repairing it would misreport
+// what the sender delivered.
+func TestEventLogView_BinaryBodyLeftAsStored(t *testing.T) {
+	t.Parallel()
+
+	raw := make([]byte, bodyCap+808)
+	for i := range raw {
+		// 0x80..0xBF: continuation bytes, never a rune start.
+		raw[i] = 0x80 | byte(i%0x40)
+	}
+
+	view := seedAndProject(t, string(raw))
+
+	assert.True(t, view.BodyTruncated)
+	assert.Equal(t, int64(len(raw)), view.BodyBytes)
+	assert.Equal(t, string(raw[:bodyCap]), view.Body)
+	assert.False(t, utf8.ValidString(view.Body))
+}
+
+// TestTrimPartialRune covers the distinction the cut repair
+// turns on: an incomplete but valid sequence is dropped, while
+// bytes that are merely invalid UTF-8 are left alone.
+func TestTrimPartialRune(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name string
+		in   []byte
+		want []byte
+	}{{
+		name: "complete ascii",
+		in:   []byte("abc"),
+		want: []byte("abc"),
+	}, {
+		name: "complete multibyte",
+		in:   []byte("ab" + snowman),
+		want: []byte("ab" + snowman),
+	}, {
+		name: "two byte rune cut",
+		in:   []byte{'a', 0xC3},
+		want: []byte{'a'},
+	}, {
+		name: "three byte rune cut after one",
+		in:   []byte{'a', 0xE2},
+		want: []byte{'a'},
+	}, {
+		name: "three byte rune cut after two",
+		in:   []byte{'a', 0xE2, 0x98},
+		want: []byte{'a'},
+	}, {
+		name: "four byte rune cut",
+		in:   []byte{'a', 0xF0, 0x9F, 0x92}, // U+1F4A9 cut
+		want: []byte{'a'},
+	}, {
+		name: "invalid start byte kept",
+		in:   []byte{'a', 0xFF},
+		want: []byte{'a', 0xFF},
+	}, {
+		name: "orphan continuation bytes kept",
+		in:   []byte{0x80, 0x81, 0x82, 0x83, 0x84},
+		want: []byte{0x80, 0x81, 0x82, 0x83, 0x84},
+	}, {
+		name: "truncated sequence followed by junk kept",
+		in:   []byte{0xE2, 0x98, 0xFF},
+		want: []byte{0xE2, 0x98, 0xFF},
+	}, {
+		name: "empty",
+		in:   []byte{},
+		want: []byte{},
+	}}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			assert.Equal(
+				t, tc.want,
+				handlers.TrimPartialRuneForTest(tc.in),
+			)
+		})
+	}
+}

internal/handlers/export_test.go

@@ -3,8 +3,35 @@ package handlers
 import (
 	"html/template"
 	"net/http"
+
+	"sneak.berlin/go/webhooker/internal/database"
 )
 
+// MaxRenderedBodyBytesForTest exposes the event log's body cap
+// to the handlers_test package.
+const MaxRenderedBodyBytesForTest = maxRenderedBodyBytes
+
+// TrimPartialRuneForTest exposes trimPartialRune for use in the
+// handlers_test package.
+func TrimPartialRuneForTest(b []byte) []byte {
+	return trimPartialRune(b)
+}
+
+// LoadEventLogViewsForTest exposes loadEventsWithDeliveries for
+// use in the handlers_test package. Assertions on the projected
+// body need the bytes as loaded: html/template rewrites invalid
+// UTF-8 on the way out, so the rendered page cannot show whether
+// a binary body survived the projection intact.
+func (s *Handlers) LoadEventLogViewsForTest(
+	w http.ResponseWriter,
+	webhook database.Webhook,
+	page int,
+) []EventLogView {
+	views, _ := s.loadEventsWithDeliveries(w, webhook, nil, page)
+
+	return views
+}
+
 // AddTemplateForTest registers a template under a page name so that
 // the handlers_test package can drive the render path with a
 // template of its own.

internal/handlers/handlers.go

@@ -229,8 +229,10 @@ func (s *Handlers) renderTemplate(
 // the response only once rendering has fully succeeded. Executing
 // straight into the ResponseWriter commits a partial body and a 200
 // status before a mid-render error can be reported, leaving no way
-// to serve a 500. These pages are small, so holding one in memory is
-// the right trade.
+// to serve a 500. Buffering makes a page's rendered size resident
+// memory per concurrent viewer, so every page owes it a bound: the
+// event log caps each stored body at maxRenderedBodyBytes for exactly
+// this reason.
 func (s *Handlers) executeTemplate(
 	w http.ResponseWriter,
 	tmpl *template.Template,

internal/handlers/source_detail_test.go

@@ -131,6 +131,47 @@ func TestHandleSourceDetail_MasksSlackWebhookURL(t *testing.T) {
 	assert.Contains(t, body, "https://hooks.slack.com/...")
 }
 
+// TestHandleSourceDetail_MasksHTTPDestinationURL is the
+// regression test for the same leak reached through the http
+// target: its destination is routinely an incoming-webhook
+// endpoint whose path segments are the credential, so the
+// rendered page must not contain them.
+func TestHandleSourceDetail_MasksHTTPDestinationURL(
+	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)
+	seedConfiguredTarget(
+		t, db, wh.ID,
+		database.TargetTypeHTTP,
+		`{"url":"`+slackWebhookURL+`"}`,
+	)
+
+	body := renderSourceDetailPage(t, h, sess, wh.ID)
+
+	assert.NotContains(t, body, slackSecretPath)
+	assert.NotContains(t, body, "T00000000")
+	assert.NotContains(t, body, "B00000000")
+	assert.NotContains(
+		t, body, "XXXXXXXXXXXXXXXXXXXXXXXX",
+	)
+
+	assert.Contains(t, body, "Destination URL")
+	assert.Contains(t, body, "https://hooks.slack.com/...")
+}
+
 // TestHandleSourceDetail_RendersNamedTargetFields proves the
 // other target types render labelled fields rather than the
 // stored blob.
@@ -172,7 +213,7 @@ func TestHandleSourceDetail_RendersNamedTargetFields(
 	body := renderSourceDetailPage(t, h, sess, wh.ID)
 
 	assert.Contains(t, body, "Destination URL")
-	assert.Contains(t, body, "https://example.com/hook")
+	assert.Contains(t, body, "https://example.com/...")
 	assert.Contains(t, body, "Timeout")
 	assert.Contains(t, body, "1 configured")
 	assert.NotContains(t, body, "sekrit")

internal/handlers/source_management.go

@@ -92,13 +92,6 @@ func parseRetentionDays(raw string, fallback int) (int, error) {
 	return v, nil
 }
 
-// EventWithDeliveries holds an event and its deliveries.
-type EventWithDeliveries struct {
-	database.Event
-
-	Deliveries []DeliveryView
-}
-
 // DeliveryView is the display-safe projection of a delivery
 // for the event log page. Its target is a TargetView, so the
 // stored configuration blob — which holds the target's
@@ -815,16 +808,18 @@ func (h *Handlers) parsePage(r *http.Request) int {
 }
 
 // loadEventsWithDeliveries loads paginated events and their
-// deliveries from the per-webhook database.
+// deliveries from the per-webhook database. Events come back
+// as capped projections rather than database.Event rows: see
+// eventLogColumns for why the cut happens in SQL.
 func (h *Handlers) loadEventsWithDeliveries(
 	w http.ResponseWriter,
 	webhook database.Webhook,
 	targetMap map[string]delivery.TargetView,
 	page int,
-) ([]EventWithDeliveries, int64) {
+) ([]EventLogView, int64) {
 	var totalEvents int64
 
-	var result []EventWithDeliveries
+	var result []EventLogView
 
 	if !h.dbMgr.DBExists(webhook.ID) {
 		return result, totalEvents
@@ -845,23 +840,25 @@ func (h *Handlers) loadEventsWithDeliveries(
 
 	offset := (page - 1) * paginationPerPage
 
-	var events []database.Event
+	var rows []eventLogRow
 
-	webhookDB.Where(
+	webhookDB.Model(&database.Event{}).Select(
+		eventLogColumns, maxRenderedBodyBytes,
+	).Where(
 		"webhook_id = ?", webhook.ID,
 	).Order("created_at DESC").Offset(offset).Limit(
 		paginationPerPage,
-	).Find(&events)
+	).Find(&rows)
 
-	result = make([]EventWithDeliveries, len(events))
+	result = make([]EventLogView, len(rows))
 
-	for i := range events {
-		result[i].Event = events[i]
+	for i := range rows {
+		result[i] = rows[i].view()
 
 		var deliveries []database.Delivery
 
 		webhookDB.Where(
-			"event_id = ?", events[i].ID,
+			"event_id = ?", rows[i].ID,
 		).Find(&deliveries)
 
 		result[i].Deliveries = newDeliveryViews(

internal/middleware/accesslog_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 
 	"github.com/go-chi/chi"
+	chimw "github.com/go-chi/chi/middleware"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"sneak.berlin/go/webhooker/internal/config"
@@ -25,15 +26,38 @@ const floodRequests = 64
 // line for a redirected or rejected request may contain it.
 const attackerMarker = "QQATTACKERTEXTQQ"
 
-// maxLineBytes bounds a single access log line. Well above what the
-// fixed fields need, well below the length of the oversized path the
-// amplification test sends.
+// maxLineBytes bounds a single access log line whose client-supplied
+// fields are of ordinary size. Well above what the fixed fields need,
+// well below the length of the oversized input the amplification tests
+// send.
 const maxLineBytes = 1024
 
+// maxCappedLineBytes bounds a single access log line when every
+// client-supplied field arrives oversized and is truncated to its
+// budget. This is the number the README quotes as the per-line cost an
+// operator sizes log storage against.
+const maxCappedLineBytes = 2560
+
 // oversizedSegmentBytes is the length of the single attacker-chosen
-// path segment used to show line size does not track input size.
+// path segment, query string or header used to show line size does not
+// track input size.
 const oversizedSegmentBytes = 8192
 
+// tailMarker is placed at the END of an oversized header value, so its
+// absence from the log proves the value was truncated rather than
+// merely being short.
+const tailMarker = "QQTRUNCATEDTAILQQ"
+
+// These mirror the middleware's own budgets, which are unexported.
+// They are duplicated rather than exported so that widening a budget
+// in the middleware has to be restated here deliberately.
+const (
+	maxFieldBytes         = 512
+	maxRequestIDBytes     = 128
+	truncationSuffix      = "[truncated]"
+	unmatchedRouteLiteral = "(unmatched)"
+)
+
 // capturingMiddleware returns a Middleware whose logger writes JSON
 // lines into the returned buffer, so the access log can be asserted
 // on directly.
@@ -54,11 +78,23 @@ func capturingMiddleware(t *testing.T) (*middleware.Middleware, *bytes.Buffer) {
 // accessLogRouter mirrors the production route shapes that an
 // unauthenticated client can reach: the public receiver, the
 // authenticated profile route (which redirects to login rather than
-// rejecting outright), and a plain static route.
+// rejecting outright), the health check (which answers 200 to anyone,
+// behind no rate limiter at all), and a plain static route.
 func accessLogRouter(m *middleware.Middleware) *chi.Mux {
 	router := chi.NewRouter()
+	// Production registers RequestID ahead of Logging, and chi's
+	// RequestID passes an inbound X-Request-Id header straight
+	// through, so the request_id field is client-supplied too.
+	router.Use(chimw.RequestID)
 	router.Use(m.Logging())
 
+	router.Get(
+		"/.well-known/healthcheck",
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusOK)
+		},
+	)
+
 	router.HandleFunc(
 		"/webhook/{uuid}",
 		func(w http.ResponseWriter, r *http.Request) {
@@ -93,13 +129,25 @@ func accessLogRouter(m *middleware.Middleware) *chi.Mux {
 }
 
 // accessLogEntries decodes the captured buffer into one map per
-// logged line.
+// logged line, holding every line to maxLineBytes.
 func accessLogEntries(
 	t *testing.T,
 	buf *bytes.Buffer,
 ) []map[string]any {
 	t.Helper()
 
+	return accessLogEntriesWithin(t, buf, maxLineBytes)
+}
+
+// accessLogEntriesWithin decodes the captured buffer into one map per
+// logged line, holding every line to bound bytes.
+func accessLogEntriesWithin(
+	t *testing.T,
+	buf *bytes.Buffer,
+	bound int,
+) []map[string]any {
+	t.Helper()
+
 	var entries []map[string]any
 
 	for line := range strings.SplitSeq(
@@ -110,7 +158,7 @@ func accessLogEntries(
 		}
 
 		require.LessOrEqual(
-			t, len(line), maxLineBytes,
+			t, len(line), bound,
 			"access log line exceeded its bound",
 		)
 
@@ -128,9 +176,27 @@ func accessLogEntries(
 func get(t *testing.T, router *chi.Mux, target string) int {
 	t.Helper()
 
+	return getWithHeaders(t, router, target, nil)
+}
+
+// getWithHeaders drives one GET through the router with the supplied
+// request headers set.
+func getWithHeaders(
+	t *testing.T,
+	router *chi.Mux,
+	target string,
+	headers map[string]string,
+) int {
+	t.Helper()
+
 	req := httptest.NewRequestWithContext(
 		context.Background(), http.MethodGet, target, nil,
 	)
+
+	for name, value := range headers {
+		req.Header.Set(name, value)
+	}
+
 	w := httptest.NewRecorder()
 	router.ServeHTTP(w, req)
 
@@ -217,26 +283,134 @@ func TestAccessLog_UnroutablePathsLogFixedLiteral(t *testing.T) {
 	)
 }
 
+// TestAccessLog_LineSizeDoesNotTrackInputSize drives 8 KB of
+// client-chosen text at the access log through each part of the
+// request that reaches it, and holds the resulting line to a fixed
+// bound in every case.
 func TestAccessLog_LineSizeDoesNotTrackInputSize(t *testing.T) {
 	t.Parallel()
 
+	oversized := strings.Repeat("h", oversizedSegmentBytes) + tailMarker
+
+	tests := map[string]struct {
+		target     string
+		headers    map[string]string
+		wantStatus int
+		wantURL    string
+		bound      int
+	}{
+		"oversized path segment": {
+			target: "/webhook/" + attackerMarker +
+				strings.Repeat("x", oversizedSegmentBytes),
+			wantStatus: http.StatusNotFound,
+			wantURL:    "/webhook/{uuid}",
+			bound:      maxLineBytes,
+		},
+		// /.well-known/healthcheck answers 200 to anyone and has no
+		// rate limiter in front of it, so an oversized query appended
+		// to it would otherwise buy the same amplification as an
+		// invented 404 path, unauthenticated and unthrottled.
+		"oversized query on an unauthenticated 200": {
+			target: "/.well-known/healthcheck?q=" + attackerMarker +
+				strings.Repeat("x", oversizedSegmentBytes),
+			wantStatus: http.StatusOK,
+			wantURL:    "/.well-known/healthcheck?(redacted)",
+			bound:      maxLineBytes,
+		},
+		// These reach the line on every request, including one whose
+		// url field is correctly redacted.
+		"oversized headers": {
+			target: "/" + attackerMarker,
+			headers: map[string]string{
+				"User-Agent":   oversized,
+				"Referer":      oversized,
+				"X-Request-Id": oversized,
+			},
+			wantStatus: http.StatusNotFound,
+			wantURL:    unmatchedRouteLiteral,
+			bound:      maxCappedLineBytes,
+		},
+	}
+
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
 			m, buf := capturingMiddleware(t)
 			router := accessLogRouter(m)
 
-	target := "/webhook/" + attackerMarker +
-		strings.Repeat("x", oversizedSegmentBytes)
+			assert.Equal(
+				t,
+				tc.wantStatus,
+				getWithHeaders(t, router, tc.target, tc.headers),
+			)
 
-	assert.Equal(t, http.StatusNotFound, get(t, router, target))
-
-	// accessLogEntries enforces maxLineBytes, which is far smaller
-	// than the path just sent.
-	entries := accessLogEntries(t, buf)
+			// accessLogEntriesWithin enforces the bound, which is
+			// orders of magnitude smaller than the input just sent.
+			entries := accessLogEntriesWithin(t, buf, tc.bound)
 			require.Len(t, entries, 1)
-	assert.Equal(t, "/webhook/{uuid}", entries[0]["url"])
-	assert.NotContains(t, buf.String(), attackerMarker)
+			assert.Equal(t, tc.wantURL, entries[0]["url"])
+
+			// The markers sit at the far end of the client-chosen
+			// text, so their absence is what proves the redaction and
+			// the truncation actually ran.
+			assert.NotContains(
+				t, buf.String(), attackerMarker,
+				"access log carried attacker-chosen text",
+			)
+			assert.NotContains(
+				t, buf.String(), tailMarker,
+				"access log carried an untruncated client field",
+			)
+		})
+	}
 }
 
-func TestAccessLog_SuccessKeepsConcreteURL(t *testing.T) {
+// TestAccessLog_OversizedHeadersKeepATruncatedPrefix checks the other
+// half of the header cap: the fields are cut, not dropped, so a
+// truncated User-Agent is still worth reading.
+func TestAccessLog_OversizedHeadersKeepATruncatedPrefix(t *testing.T) {
+	t.Parallel()
+
+	m, buf := capturingMiddleware(t)
+	router := accessLogRouter(m)
+
+	oversized := strings.Repeat("h", oversizedSegmentBytes) + tailMarker
+
+	assert.Equal(
+		t,
+		http.StatusNotFound,
+		getWithHeaders(
+			t, router, "/nope",
+			map[string]string{
+				"User-Agent":   oversized,
+				"Referer":      oversized,
+				"X-Request-Id": oversized,
+			},
+		),
+	)
+
+	entries := accessLogEntriesWithin(t, buf, maxCappedLineBytes)
+	require.Len(t, entries, 1)
+
+	for key, budget := range map[string]int{
+		"useragent":  maxFieldBytes,
+		"referer":    maxFieldBytes,
+		"request_id": maxRequestIDBytes,
+	} {
+		value, ok := entries[0][key].(string)
+		require.True(t, ok, key)
+		assert.LessOrEqual(
+			t, len(value), budget+len(truncationSuffix), key,
+		)
+		assert.Contains(t, value, truncationSuffix, key)
+		assert.Contains(t, value, "hhhh", key)
+	}
+}
+
+func TestAccessLog_SuccessKeepsConcretePathAndRedactsQuery(
+	t *testing.T,
+) {
 	t.Parallel()
 
 	m, buf := capturingMiddleware(t)
@@ -246,9 +420,12 @@ func TestAccessLog_SuccessKeepsConcreteURL(t *testing.T) {
 		t, http.StatusOK, get(t, router, "/webhook/known?src=ci"),
 	)
 
+	// The path resolved against a stored entrypoint, so it stays. The
+	// query never does: see TestAccessLog_UnauthenticatedSuccess...
 	entries := accessLogEntries(t, buf)
 	require.Len(t, entries, 1)
-	assert.Equal(t, "/webhook/known?src=ci", entries[0]["url"])
+	assert.Equal(t, "/webhook/known?(redacted)", entries[0]["url"])
+	assert.NotContains(t, buf.String(), "src=ci")
 }
 
 func TestAccessLog_ServerErrorKeepsConcreteURL(t *testing.T) {

internal/middleware/middleware.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"net"
 	"net/http"
+	"strings"
 	"time"
 
 	basicauth "github.com/99designs/basicauth-go"
@@ -32,6 +33,35 @@ const (
 	// all. Every byte of such a path is client-chosen, so none of it
 	// is logged.
 	unmatchedRoute = "(unmatched)"
+
+	// redactedQuery stands in for the query string on the access log
+	// branches that keep the concrete URL. The query is client-chosen
+	// on every route, including the ones that answer an
+	// unauthenticated 200, so logging it verbatim would let a client
+	// pick the size of the line it writes.
+	redactedQuery = "?(redacted)"
+
+	// maxLogFieldBytes bounds each access log field whose value the
+	// client supplies outright: the URL, the User-Agent and the
+	// Referer. 512 bytes holds a real browser's User-Agent whole, so a
+	// truncated one is still worth having.
+	maxLogFieldBytes = 512
+
+	// maxLogRequestIDBytes bounds the request id, which is also
+	// client-supplied: chi's RequestID middleware passes an inbound
+	// X-Request-Id header through verbatim. Its generated form is an
+	// order of magnitude shorter than this.
+	maxLogRequestIDBytes = 128
+
+	// maxLogMethodBytes bounds the method. Go accepts any RFC 7230
+	// token there, bounded only by the header size limit, so it is
+	// client-chosen text like the rest. The longest registered method
+	// is half this.
+	maxLogMethodBytes = 32
+
+	// truncationMarker is appended to any field the access log cut, so
+	// a short value and a truncated one cannot be confused.
+	truncationMarker = "[truncated]"
 )
 
 //nolint:revive // MiddlewareParams is a standard fx naming convention.
@@ -101,13 +131,58 @@ func (lrw *loggingResponseWriter) WriteHeader(code int) {
 	lrw.ResponseWriter.WriteHeader(code)
 }
 
+// truncateLogField caps s at maxBytes, marking the value when it cuts.
+//
+// The result is always valid UTF-8: a byte-boundary cut can split a
+// multi-byte rune, and a header can carry bytes that were never valid
+// UTF-8 to begin with, either of which a JSON encoder expands to six
+// bytes apiece. Dropping them keeps the encoded field inside the same
+// budget as the raw one.
+func truncateLogField(s string, maxBytes int) string {
+	if len(s) <= maxBytes {
+		return strings.ToValidUTF8(s, "")
+	}
+
+	return strings.ToValidUTF8(s[:maxBytes], "") + truncationMarker
+}
+
+// concreteLogURL renders the request's own URL for the access log
+// branches that keep it, with the query string replaced by a fixed
+// marker.
+//
+// The path on those branches is bounded by the service's routes or by
+// the operator's data — a 2xx on the receiver means the UUID named a
+// stored entrypoint, a 2xx under /s means the file is in the embedded
+// tree. The query is not bounded by anything: /.well-known/healthcheck
+// and /s/* take no authentication and sit behind no rate limiter, and
+// /pages/login behind only the login limiter, so any of them will
+// answer 200 to a URL carrying an arbitrary number of arbitrary bytes
+// after the '?'. Keeping the path and dropping the query is what makes
+// this branch as bounded as the pattern branches below.
+//
+// Nothing debuggable is lost. One route in the service reads a query
+// parameter at all — `page`, on the authenticated pagination links in
+// internal/handlers/source_management.go — and the alternatives that
+// would preserve more (a key count, a key allowlist) all require
+// parsing an attacker-sized query on every request, which is work an
+// unauthenticated client would then be choosing for us.
+func concreteLogURL(r *http.Request) string {
+	path := r.URL.EscapedPath()
+
+	if r.URL.RawQuery == "" && !r.URL.ForceQuery {
+		return path
+	}
+
+	return path + redactedQuery
+}
+
 // accessLogURL returns the value for the access log's url field.
 //
-// 2xx and 5xx responses get the concrete URL. A success resolved
-// against a static route or against the operator's own data — on the
-// receiver, a 2xx means the UUID named a stored entrypoint — and a
-// server error is our own bug, where the exact URL is the primary
-// evidence and which no client can provoke at will.
+// 2xx and 5xx responses get the concrete path (see concreteLogURL). A
+// success resolved against a static route or against the operator's
+// own data — on the receiver, a 2xx means the UUID named a stored
+// entrypoint — and a server error is our own bug, where the exact URL
+// is the primary evidence and which no client can provoke at will.
 //
 // 3xx and 4xx responses get the chi route pattern instead. Those are
 // the outcomes an unauthenticated client drives for free: 404 or 429
@@ -123,7 +198,7 @@ func (lrw *loggingResponseWriter) WriteHeader(code int) {
 func accessLogURL(r *http.Request, status int) string {
 	if status < http.StatusMultipleChoices ||
 		status >= http.StatusInternalServerError {
-		return r.URL.String()
+		return concreteLogURL(r)
 	}
 
 	if rc := chi.RouteContext(r.Context()); rc != nil {
@@ -159,13 +234,27 @@ func (s *Middleware) Logging() func(http.Handler) http.Handler {
 					}
 				}
 
+				// Every field below that a client can influence is
+				// truncated to a fixed budget, so the size of this
+				// line does not track the size of the request.
 				s.log.Info("http request",
 					"request_start", start,
-					"method", r.Method,
-					"url", accessLogURL(r, lrw.statusCode),
-					"useragent", r.UserAgent(),
-					"request_id", requestID,
-					"referer", r.Referer(),
+					"method", truncateLogField(
+						r.Method, maxLogMethodBytes,
+					),
+					"url", truncateLogField(
+						accessLogURL(r, lrw.statusCode),
+						maxLogFieldBytes,
+					),
+					"useragent", truncateLogField(
+						r.UserAgent(), maxLogFieldBytes,
+					),
+					"request_id", truncateLogField(
+						requestID, maxLogRequestIDBytes,
+					),
+					"referer", truncateLogField(
+						r.Referer(), maxLogFieldBytes,
+					),
 					"proto", r.Proto,
 					"remoteIP", ipFromHostPort(r.RemoteAddr),
 					"status", lrw.statusCode,

templates/source_logs.html

@@ -37,6 +37,9 @@
 
                 <div x-show="open" x-cloak class="mt-3 p-3 bg-gray-50 rounded-md">
                     <pre class="text-xs text-gray-700 overflow-x-auto whitespace-pre-wrap break-all">{{.Body}}</pre>
+                    {{if .BodyTruncated}}
+                    <p class="mt-2 text-xs text-gray-500">Body truncated for display: showing {{.BodyShownBytes}} of {{.BodyBytes}} bytes. The stored body is unchanged.</p>
+                    {{end}}
                 </div>
             </div>
             {{else}}