Add manifestlist validation

Signed-off-by: zhouhao <zhouhao@cn.fujitsu.com>

image/image.go

@@ -87,6 +87,16 @@ func validate(w walker, refs []string, out *log.Logger) error {
 		if err := m.validate(w); err != nil {
 			return err
 		}
+
+		ml, err := findManifestList(w, d)
+		if ml != nil {
+			if err := ml.validate(w); err != nil {
+				return err
+			}
+		} else if err != nil {
+			return err
+		}
+
 		if out != nil {
 			out.Printf("reference %q: OK", ref)
 		}

image/image_test.go

@@ -110,6 +110,23 @@ var (
     "mediaType": "application/vnd.oci.image.manifest.v1+json",
     "schemaVersion": 2
 }
+ `
+	manifestlistStr = `{
+    "schemaVersion": 2,
+    "mediaType": "application/vnd.oci.image.manifest.list.v1+json",
+    "manifests": [
+    {
+      "mediaType": "application/vnd.oci.image.manifest.v1+json",
+      "size": "<manifest_size>",
+      "digest": "<manifest_digest>",      
+      "platform": {
+          "architecture": "ppc64le",
+          "os": "linux"
+      }
+    },
+  ],
+  "annotations": null
+} 
  `
 )
 

image/manifest_list.go

@@ -0,0 +1,83 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 image
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/opencontainers/image-spec/schema"
+	"github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
+)
+
+type manifestlist struct {
+	Manifests []ManifestDescriptor `json:"manifests"`
+}
+type ManifestDescriptor struct {
+	Manifest descriptor
+}
+
+func findManifestList(w walker, d *descriptor) (*manifestlist, error) {
+	var ml manifestlist
+	mlpath := filepath.Join("blobs", d.algo(), d.hash())
+
+	switch err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
+		if info.IsDir() || filepath.Clean(path) != mlpath {
+			return nil
+		}
+
+		buf, err := ioutil.ReadAll(r)
+		if err != nil {
+			return errors.Wrapf(err, "%s: error reading manifestlist", path)
+		}
+
+		if err := schema.MediaTypeManifestList.Validate(bytes.NewReader(buf)); err != nil {
+			return errors.Wrapf(err, "%s: manifestlist validation failed", path)
+		}
+
+		if err := json.Unmarshal(buf, &ml); err != nil {
+			return err
+		}
+
+		if len(ml.Manifests) == 0 {
+			return fmt.Errorf("%s: no manifests found", path)
+		}
+
+		return errEOW
+	}); err {
+	case nil:
+		return nil, nil
+	case errEOW:
+		return &ml, nil
+	default:
+		return nil, err
+	}
+}
+
+func (ml *manifestlist) validate(w walker) error {
+	for _, d := range ml.Manifests {
+		if err := d.Manifest.validate(w, []string{v1.MediaTypeImageManifest}); err != nil {
+			return errors.Wrap(err, "Manifest validation failed")
+		}
+	}
+
+	return nil
+}