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>

content/local/content_local_fuzzer.go

@@ -0,0 +1,76 @@
+//go:build gofuzz
+// +build gofuzz
+
+/*
+   Copyright The containerd Authors.
+
+   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 local
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"io"
+	"testing"
+
+	"github.com/opencontainers/go-digest"
+
+	"github.com/containerd/containerd/content"
+)
+
+func FuzzContentStoreWriter(data []byte) int {
+	t := &testing.T{}
+	ctx := context.Background()
+	ctx, _, cs, cleanup := contentStoreEnv(t)
+	defer cleanup()
+
+	cw, err := cs.Writer(ctx, content.WithRef("myref"))
+	if err != nil {
+		return 0
+	}
+	if err := cw.Close(); err != nil {
+		return 0
+	}
+
+	// reopen, so we can test things
+	cw, err = cs.Writer(ctx, content.WithRef("myref"))
+	if err != nil {
+		return 0
+	}
+
+	err = checkCopyFuzz(int64(len(data)), cw, bufio.NewReader(io.NopCloser(bytes.NewReader(data))))
+	if err != nil {
+		return 0
+	}
+	expected := digest.FromBytes(data)
+
+	if err = cw.Commit(ctx, int64(len(data)), expected); err != nil {
+		return 0
+	}
+	return 1
+}
+
+func checkCopyFuzz(size int64, dst io.Writer, src io.Reader) error {
+	nn, err := io.Copy(dst, src)
+	if err != nil {
+		return err
+	}
+
+	if nn != size {
+		return err
+	}
+	return nil
+}