fuzzing: improve archive fuzzer

Signed-off-by: AdamKorcz <adam@adalogics.com>

contrib/fuzz/archive_fuzzer.go

@@ -17,9 +17,12 @@
 package fuzz
 
 import (
+	"archive/tar"
 	"bytes"
 	"context"
+	"io"
 	"os"
+	"path"
 
 	fuzz "github.com/AdaLogics/go-fuzz-headers"
 	"github.com/sirupsen/logrus"
@@ -28,6 +31,7 @@ import (
 	"github.com/containerd/containerd/content/local"
 	imageArchive "github.com/containerd/containerd/images/archive"
 	"github.com/containerd/containerd/log"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 // FuzzApply implements a fuzzer that applies
@@ -73,6 +77,31 @@ func FuzzImportIndex(data []byte) int {
 	}
 	ctx := context.Background()
 	r := bytes.NewReader(tarBytes)
+	shouldRequireLayoutOrManifest, err := f.GetBool()
+	if err != nil {
+		return 0
+	}
+	if shouldRequireLayoutOrManifest {
+		tr := tar.NewReader(r)
+		for {
+			hdr, err := tr.Next()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				return 0
+			}
+			hdrName := path.Clean(hdr.Name)
+			switch hdrName {
+			case ocispec.ImageLayoutFile:
+				break
+			case "manifest.json":
+				break
+			default:
+				return 0
+			}
+		}
+	}
 	tmpdir, err := os.MkdirTemp("", "fuzzing-")
 	if err != nil {
 		return 0