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// 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 (
"crypto/sha256"
"encoding/hex"
"encoding/json"
"fmt"
"io"
"os"
"path/filepath"
"strings"
"github.com/pkg/errors"
)
type descriptor struct {
MediaType string `json:"mediaType"`
Digest string `json:"digest"`
Size int64 `json:"size"`
}
func (d *descriptor) algo() string {
pts := strings.SplitN(d.Digest, ":", 2)
if len(pts) != 2 {
return ""
}
return pts[0]
}
func (d *descriptor) hash() string {
pts := strings.SplitN(d.Digest, ":", 2)
if len(pts) != 2 {
return ""
}
return pts[1]
}
func listReferences(w walker) (map[string]*descriptor, error) {
refs := make(map[string]*descriptor)
if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
if info.IsDir() || !strings.HasPrefix(path, "refs") {
return nil
}
var d descriptor
if err := json.NewDecoder(r).Decode(&d); err != nil {
return err
}
refs[info.Name()] = &d
return nil
}); err != nil {
return nil, err
}
return refs, nil
}
func findDescriptor(w walker, name string) (*descriptor, error) {
var d descriptor
dpath := filepath.Join("refs", name)
switch err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
if info.IsDir() || filepath.Clean(path) != dpath {
return nil
}
if err := json.NewDecoder(r).Decode(&d); err != nil {
return err
}
return errEOW
}); err {
case nil:
return nil, fmt.Errorf("%s: descriptor not found", dpath)
case errEOW:
return &d, nil
default:
return nil, err
}
}
func (d *descriptor) validate(w walker, mts []string) error {
var found bool
for _, mt := range mts {
if d.MediaType == mt {
found = true
break
}
}
if !found {
return fmt.Errorf("invalid descriptor MediaType %q", d.MediaType)
}
switch err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
if info.IsDir() {
return nil
}
filename, err := filepath.Rel(filepath.Join("blobs", d.algo()), filepath.Clean(path))
if err != nil || d.hash() != filename {
return nil
}
if err := d.validateContent(r); err != nil {
return err
}
return errEOW
}); err {
case nil:
return fmt.Errorf("%s: not found", d.Digest)
case errEOW:
return nil
default:
return errors.Wrapf(err, "%s: validation failed", d.Digest)
}
}
func (d *descriptor) validateContent(r io.Reader) error {
h := sha256.New()
n, err := io.Copy(h, r)
if err != nil {
return errors.Wrap(err, "error generating hash")
}
digest := "sha256:" + hex.EncodeToString(h.Sum(nil))
if digest != d.Digest {
return errors.New("digest mismatch")
}
if n != d.Size {
return errors.New("size mismatch")
}
return nil
}
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