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descriptor.go
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descriptor.go
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// Copyright 2018 Google LLC All Rights Reserved.
//
// 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 remote
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"strings"
"github.com/google/go-containerregistry/pkg/logs"
"github.com/google/go-containerregistry/pkg/name"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/partial"
"github.com/google/go-containerregistry/pkg/v1/remote/transport"
"github.com/google/go-containerregistry/pkg/v1/types"
"github.com/google/go-containerregistry/pkg/v1/v1util"
)
var defaultPlatform = v1.Platform{
Architecture: "amd64",
OS: "linux",
}
// ErrSchema1 indicates that we received a schema1 manifest from the registry.
// This library doesn't have plans to support this legacy image format:
// https://github.com/google/go-containerregistry/issues/377
type ErrSchema1 struct {
schema string
}
// newErrSchema1 returns an ErrSchema1 with the unexpected MediaType.
func newErrSchema1(schema types.MediaType) error {
return &ErrSchema1{
schema: string(schema),
}
}
// Error implements error.
func (e *ErrSchema1) Error() string {
return fmt.Sprintf("unsupported MediaType: %q, see https://github.com/google/go-containerregistry/issues/377", e.schema)
}
// Descriptor provides access to metadata about remote artifact and accessors
// for efficiently converting it into a v1.Image or v1.ImageIndex.
type Descriptor struct {
fetcher
v1.Descriptor
Manifest []byte
// So we can share this implementation with Image..
platform v1.Platform
}
// RawManifest exists to satisfy the Taggable interface.
func (d *Descriptor) RawManifest() ([]byte, error) {
return d.Manifest, nil
}
// Get returns a remote.Descriptor for the given reference. The response from
// the registry is left un-interpreted, for the most part. This is useful for
// querying what kind of artifact a reference represents.
func Get(ref name.Reference, options ...Option) (*Descriptor, error) {
acceptable := []types.MediaType{
// Just to look at them.
types.DockerManifestSchema1,
types.DockerManifestSchema1Signed,
}
acceptable = append(acceptable, acceptableImageMediaTypes...)
acceptable = append(acceptable, acceptableIndexMediaTypes...)
return get(ref, acceptable, options...)
}
// Handle options and fetch the manifest with the acceptable MediaTypes in the
// Accept header.
func get(ref name.Reference, acceptable []types.MediaType, options ...Option) (*Descriptor, error) {
o, err := makeOptions(ref.Context(), options...)
if err != nil {
return nil, err
}
f, err := makeFetcher(ref, o)
if err != nil {
return nil, err
}
b, desc, err := f.fetchManifest(ref, acceptable)
if err != nil {
return nil, err
}
return &Descriptor{
fetcher: *f,
Manifest: b,
Descriptor: *desc,
platform: o.platform,
}, nil
}
// Image converts the Descriptor into a v1.Image.
//
// If the fetched artifact is already an image, it will just return it.
//
// If the fetched artifact is an index, it will attempt to resolve the index to
// a child image with the appropriate platform.
//
// See WithPlatform to set the desired platform.
func (d *Descriptor) Image() (v1.Image, error) {
switch d.MediaType {
case types.DockerManifestSchema1, types.DockerManifestSchema1Signed:
// We don't care to support schema 1 images:
// https://github.com/google/go-containerregistry/issues/377
return nil, newErrSchema1(d.MediaType)
case types.OCIImageIndex, types.DockerManifestList:
// We want an image but the registry has an index, resolve it to an image.
return d.remoteIndex().imageByPlatform(d.platform)
case types.OCIManifestSchema1, types.DockerManifestSchema2:
// These are expected. Enumerated here to allow a default case.
default:
// We could just return an error here, but some registries (e.g. static
// registries) don't set the Content-Type headers correctly, so instead...
logs.Warn.Printf("Unexpected media type for Image(): %s", d.MediaType)
}
// Wrap the v1.Layers returned by this v1.Image in a hint for downstream
// remote.Write calls to facilitate cross-repo "mounting".
imgCore, err := partial.CompressedToImage(d.remoteImage())
if err != nil {
return nil, err
}
return &mountableImage{
Image: imgCore,
Reference: d.Ref,
}, nil
}
// ImageIndex converts the Descriptor into a v1.ImageIndex.
func (d *Descriptor) ImageIndex() (v1.ImageIndex, error) {
switch d.MediaType {
case types.DockerManifestSchema1, types.DockerManifestSchema1Signed:
// We don't care to support schema 1 images:
// https://github.com/google/go-containerregistry/issues/377
return nil, newErrSchema1(d.MediaType)
case types.OCIManifestSchema1, types.DockerManifestSchema2:
// We want an index but the registry has an image, nothing we can do.
return nil, fmt.Errorf("unexpected media type for ImageIndex(): %s; call Image() instead", d.MediaType)
case types.OCIImageIndex, types.DockerManifestList:
// These are expected.
default:
// We could just return an error here, but some registries (e.g. static
// registries) don't set the Content-Type headers correctly, so instead...
logs.Warn.Printf("Unexpected media type for ImageIndex(): %s", d.MediaType)
}
return d.remoteIndex(), nil
}
func (d *Descriptor) remoteImage() *remoteImage {
return &remoteImage{
fetcher: fetcher{
Ref: d.Ref,
Client: d.Client,
},
manifest: d.Manifest,
mediaType: d.MediaType,
descriptor: &d.Descriptor,
}
}
func (d *Descriptor) remoteIndex() *remoteIndex {
return &remoteIndex{
fetcher: fetcher{
Ref: d.Ref,
Client: d.Client,
},
manifest: d.Manifest,
mediaType: d.MediaType,
descriptor: &d.Descriptor,
}
}
// fetcher implements methods for reading from a registry.
type fetcher struct {
Ref name.Reference
Client *http.Client
}
func makeFetcher(ref name.Reference, o *options) (*fetcher, error) {
tr, err := transport.New(ref.Context().Registry, o.auth, o.transport, []string{ref.Scope(transport.PullScope)})
if err != nil {
return nil, err
}
return &fetcher{
Ref: ref,
Client: &http.Client{Transport: tr},
}, nil
}
// url returns a url.Url for the specified path in the context of this remote image reference.
func (f *fetcher) url(resource, identifier string) url.URL {
return url.URL{
Scheme: f.Ref.Context().Registry.Scheme(),
Host: f.Ref.Context().RegistryStr(),
Path: fmt.Sprintf("/v2/%s/%s/%s", f.Ref.Context().RepositoryStr(), resource, identifier),
}
}
func (f *fetcher) fetchManifest(ref name.Reference, acceptable []types.MediaType) ([]byte, *v1.Descriptor, error) {
u := f.url("manifests", ref.Identifier())
req, err := http.NewRequest(http.MethodGet, u.String(), nil)
if err != nil {
return nil, nil, err
}
accept := []string{}
for _, mt := range acceptable {
accept = append(accept, string(mt))
}
req.Header.Set("Accept", strings.Join(accept, ","))
resp, err := f.Client.Do(req)
if err != nil {
return nil, nil, err
}
defer resp.Body.Close()
if err := transport.CheckError(resp, http.StatusOK); err != nil {
return nil, nil, err
}
manifest, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, nil, err
}
digest, size, err := v1.SHA256(bytes.NewReader(manifest))
if err != nil {
return nil, nil, err
}
mediaType := types.MediaType(resp.Header.Get("Content-Type"))
contentDigest, err := v1.NewHash(resp.Header.Get("Docker-Content-Digest"))
if err == nil && mediaType == types.DockerManifestSchema1Signed {
// If we can parse the digest from the header, and it's a signed schema 1
// manifest, let's use that for the digest to appease older registries.
digest = contentDigest
}
// Validate the digest matches what we asked for, if pulling by digest.
if dgst, ok := ref.(name.Digest); ok {
if digest.String() != dgst.DigestStr() {
return nil, nil, fmt.Errorf("manifest digest: %q does not match requested digest: %q for %q", digest, dgst.DigestStr(), f.Ref)
}
}
// Do nothing for tags; I give up.
//
// We'd like to validate that the "Docker-Content-Digest" header matches what is returned by the registry,
// but so many registries implement this incorrectly that it's not worth checking.
//
// For reference:
// https://github.com/GoogleContainerTools/kaniko/issues/298
// Return all this info since we have to calculate it anyway.
desc := v1.Descriptor{
Digest: digest,
Size: size,
MediaType: mediaType,
}
return manifest, &desc, nil
}
func (f *fetcher) fetchBlob(h v1.Hash) (io.ReadCloser, error) {
u := f.url("blobs", h.String())
resp, err := f.Client.Get(u.String())
if err != nil {
return nil, err
}
if err := transport.CheckError(resp, http.StatusOK); err != nil {
resp.Body.Close()
return nil, err
}
return v1util.VerifyReadCloser(resp.Body, h)
}
func (f *fetcher) headBlob(h v1.Hash) (*http.Response, error) {
u := f.url("blobs", h.String())
resp, err := f.Client.Head(u.String())
if err != nil {
return nil, err
}
if err := transport.CheckError(resp, http.StatusOK); err != nil {
resp.Body.Close()
return nil, err
}
return resp, nil
}