Copy fuzzers from github.com/cncf/cncf-fuzzing

This commit copies the fuzzers from the repository except for
containerd_import_structured_fuzzer.go.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

contrib/fuzz/diff_fuzzer.go

@@ -0,0 +1,108 @@
+// Copyright 2021 ADA Logics Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package fuzz
+
+import (
+	"context"
+	_ "crypto/sha256" // required by go-digest
+	"os"
+
+	fuzz "github.com/AdaLogics/go-fuzz-headers"
+	"github.com/containerd/containerd/content/local"
+	"github.com/containerd/containerd/diff/apply"
+	"github.com/containerd/containerd/diff/walking"
+	"github.com/containerd/containerd/mount"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+func FuzzDiffApply(data []byte) int {
+	f := fuzz.NewConsumer(data)
+
+	mountsQty, err := f.GetInt()
+	if err != nil {
+		return 0
+	}
+	mounts := make([]mount.Mount, 0)
+	for i := 0; i < mountsQty%30; i++ {
+		m := mount.Mount{}
+		err = f.GenerateStruct(&m)
+		if err != nil {
+			return 0
+		}
+		mounts = append(mounts, m)
+	}
+	desc := ocispec.Descriptor{}
+	err = f.GenerateStruct(&desc)
+	if err != nil {
+		return 0
+	}
+	tmpdir, err := os.MkdirTemp("", "fuzzing-")
+	if err != nil {
+		return 0
+	}
+	cs, err := local.NewStore(tmpdir)
+	if err != nil {
+		return 0
+	}
+	fsa := apply.NewFileSystemApplier(cs)
+	_, _ = fsa.Apply(context.Background(), desc, mounts)
+	return 1
+}
+
+func FuzzDiffCompare(data []byte) int {
+	f := fuzz.NewConsumer(data)
+
+	lowerQty, err := f.GetInt()
+	if err != nil {
+		return 0
+	}
+	lower := make([]mount.Mount, 0)
+	for i := 0; i < lowerQty%30; i++ {
+		m := mount.Mount{}
+		err = f.GenerateStruct(&m)
+		if err != nil {
+			return 0
+		}
+		lower = append(lower, m)
+	}
+
+	upperQty, err := f.GetInt()
+	if err != nil {
+		return 0
+	}
+	upper := make([]mount.Mount, 0)
+	for i := 0; i < upperQty%30; i++ {
+		m := mount.Mount{}
+		err = f.GenerateStruct(&m)
+		if err != nil {
+			return 0
+		}
+		upper = append(upper, m)
+	}
+
+	ctx := context.Background()
+	tmpdir, err := os.MkdirTemp("", "fuzzing-")
+	if err != nil {
+		return 0
+	}
+	cs, err := local.NewStore(tmpdir)
+	if err != nil {
+		return 0
+	}
+	walker := walking.NewWalkingDiff(cs)
+	_, _ = walker.Compare(ctx, lower, upper)
+	return 1
+}