test: add symlink-escape tests for go.sum and npm-shrinkwrap.json

extractor/filesystem/language/golang/gomod/gosum_test.go

@@ -0,0 +1,70 @@
+package gomod
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/google/osv-scalibr/extractor/filesystem"
+	"github.com/google/osv-scalibr/fs"
+)
+
+func TestGoSumSymlinkEscape(t *testing.T) {
+	tmpDir := t.TempDir()
+	scanRoot := filepath.Join(tmpDir, "scan-root")
+	if err := os.MkdirAll(scanRoot, 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	// File rahasia di luar root (format go.sum valid)
+	secretFile := filepath.Join(tmpDir, "secret.gosum")
+	secretContent := "github.com/example/fake v1.0.0\n"
+	if err := os.WriteFile(secretFile, []byte(secretContent), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Symlink di dalam root bernama go.sum
+	symlinkPath := filepath.Join(scanRoot, "go.sum")
+	if err := os.Symlink(secretFile, symlinkPath); err != nil {
+		t.Fatal(err)
+	}
+
+	// File go.mod minimal sebagai pemicu extractor
+	goModPath := filepath.Join(scanRoot, "go.mod")
+	if err := os.WriteFile(goModPath, []byte("module example.com\n"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	extractor := &Extractor{}
+	input := &filesystem.ScanInput{
+		Path: goModPath,
+		FS:   fs.DirFS(scanRoot),
+		Info: mustStat(t, goModPath),
+	}
+
+	inv, err := extractor.Extract(context.Background(), input)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verifikasi package dari symlink terbaca
+	found := false
+	for _, pkg := range inv.Packages {
+		if pkg.Name == "github.com/example/fake" && pkg.Version == "v1.0.0" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Errorf("expected package from symlinked go.sum to appear, got %+v", inv.Packages)
+	}
+}
+
+func mustStat(t *testing.T, path string) os.FileInfo {
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return info
+}