add config validate

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

image/config.go

@@ -15,6 +15,8 @@
 package image
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"bytes"
 	"encoding/json"
 	"fmt"
@@ -64,19 +66,23 @@ func findConfig(w walker, d *descriptor) (*config, error) {
 	}
 }
 
-func (c *config) validate(w walk) error {
+func (c *config) validate(w walker) error {
 
 	// check if the rootfs type is 'layers'
 	if c.RootFS.Type != "layers" {
-		return errors.New("%q is an unknown rootfs type, MUST be 'layers'", c.RootFS.Type)
+		return errors.New("RootFs is an unknown rootfs type, MUST be 'layers'")
 	}
 
-	for _, d = range c.RootFs.DiffIDs {
+	for _, d := range c.RootFS.DiffIDs {
 		h := sha256.New()
 		DiffIds := "sha256" + hex.EncodeToString(h.Sum(nil))
 
 		if DiffIds != d {
 			return errors.New("DiffIDs mismatch")
+		}
+	}
+
+	return nil
 }
 
 func (c *config) runtimeSpec(rootfs string) (*specs.Spec, error) {

image/image.go

@@ -190,6 +190,10 @@ func createRuntimeBundle(w walker, dest, refName, rootfs string) error {
 		return err
 	}
 
+	if err := c.validate(w); err != nil {
+		return err
+	}
+
 	err = m.unpack(w, filepath.Join(dest, rootfs))
 	if err != nil {
 		return err