fix(chromium): bound the total scope matching time per conversion

pkg/modules/chromium/scopebudget_test.go

@@ -0,0 +1,122 @@
+package chromium
+
+import (
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/dlclark/regexp2"
+)
+
+func TestScopeMatchBudget(t *testing.T) {
+	t.Run("allows matching while credit remains", func(t *testing.T) {
+		b := newScopeMatchBudget(time.Second)
+		if !b.tryAcquire() {
+			t.Fatal("tryAcquire() = false on a fresh budget, want true")
+		}
+	})
+
+	t.Run("denies matching once exhausted", func(t *testing.T) {
+		b := newScopeMatchBudget(time.Second)
+		b.consume(time.Second)
+		if b.tryAcquire() {
+			t.Error("tryAcquire() = true after the budget was spent, want false")
+		}
+	})
+
+	t.Run("saturates at zero instead of wrapping into credit", func(t *testing.T) {
+		b := newScopeMatchBudget(time.Second)
+		b.consume(time.Hour)
+		if got := b.remaining.Load(); got != 0 {
+			t.Errorf("remaining = %d, want 0", got)
+		}
+		if b.tryAcquire() {
+			t.Error("tryAcquire() = true after an overlong match, want false")
+		}
+	})
+
+	t.Run("a spent budget stays spent", func(t *testing.T) {
+		b := newScopeMatchBudget(time.Second)
+		b.consume(time.Second)
+		b.consume(time.Millisecond)
+		if got := b.remaining.Load(); got != 0 {
+			t.Errorf("remaining = %d, want 0", got)
+		}
+	})
+
+	t.Run("is safe for concurrent use", func(t *testing.T) {
+		const goroutines = 64
+		// Each goroutine spends 1ms against a budget of half that many
+		// milliseconds, so the total spend overshoots it.
+		b := newScopeMatchBudget(time.Duration(goroutines/2) * time.Millisecond)
+
+		var wg sync.WaitGroup
+		for range goroutines {
+			wg.Go(func() {
+				b.tryAcquire()
+				b.consume(time.Millisecond)
+			})
+		}
+		wg.Wait()
+
+		if got := b.remaining.Load(); got != 0 {
+			t.Errorf("remaining = %d, want 0", got)
+		}
+	})
+}
+
+// TestScopeMatchBudget_BoundsCatastrophicBacktracking is the regression test for
+// the amplification: many scoped headers matched against a hostile URL must cost
+// the budget, not a multiple of it.
+// See https://github.com/gotenberg/gotenberg/issues/1588.
+func TestScopeMatchBudget_BoundsCatastrophicBacktracking(t *testing.T) {
+	const (
+		headers = 16
+		budget  = 200 * time.Millisecond
+	)
+
+	// Nested quantifier with no possible match: classic catastrophic
+	// backtracking.
+	pattern := compileScopePattern(t, `(a+)+b`)
+	url := "http://example.com/" + strings.Repeat("a", 40)
+
+	b := newScopeMatchBudget(budget)
+
+	start := time.Now()
+	var matched int
+	for range headers {
+		if !b.tryAcquire() {
+			break
+		}
+		matchStart := time.Now()
+		_, _ = pattern.MatchString(url)
+		b.consume(time.Since(matchStart))
+		matched++
+	}
+	elapsed := time.Since(start)
+
+	if matched == headers {
+		t.Errorf("all %d headers were matched, want the budget to stop matching early", headers)
+	}
+
+	// Each match is separately capped at extraHttpHeaderScopeMatchTimeout, so
+	// the worst case is the budget plus one final match that started with the
+	// last of the credit. Generous slack keeps this stable on a loaded CI box.
+	ceiling := budget + extraHttpHeaderScopeMatchTimeout + time.Second
+	if elapsed > ceiling {
+		t.Errorf("matching took %s, want at most %s", elapsed, ceiling)
+	}
+}
+
+func compileScopePattern(t *testing.T, pattern string) *regexp2.Regexp {
+	t.Helper()
+
+	p, err := regexp2.Compile(pattern, regexp2.None)
+	if err != nil {
+		t.Fatalf("compile %q: %v", pattern, err)
+	}
+	p.MatchTimeout = extraHttpHeaderScopeMatchTimeout
+
+	return p
+}