buildkit/util/imageutil/config.go

140 lines
3.5 KiB
Go

package imageutil
import (
"context"
"encoding/json"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/platforms"
"github.com/containerd/containerd/reference"
"github.com/containerd/containerd/remotes"
digest "github.com/opencontainers/go-digest"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
)
type IngesterProvider interface {
content.Ingester
content.Provider
}
func Config(ctx context.Context, str string, resolver remotes.Resolver, ingester IngesterProvider) (digest.Digest, []byte, error) {
ref, err := reference.Parse(str)
if err != nil {
return "", nil, errors.WithStack(err)
}
dgst := ref.Digest()
var desc *ocispec.Descriptor
if dgst != "" {
ra, err := ingester.ReaderAt(ctx, dgst)
if err == nil {
mt, err := DetectManifestMediaType(ra)
if err == nil {
desc = &ocispec.Descriptor{
Size: ra.Size(),
Digest: dgst,
MediaType: mt,
}
}
}
}
if desc == nil {
_, desc2, err := resolver.Resolve(ctx, ref.String())
if err != nil {
return "", nil, err
}
desc = &desc2
}
fetcher, err := resolver.Fetcher(ctx, ref.String())
if err != nil {
return "", nil, err
}
handlers := []images.Handler{
remotes.FetchHandler(ingester, fetcher),
childrenConfigHandler(ingester),
}
if err := images.Dispatch(ctx, images.Handlers(handlers...), *desc); err != nil {
return "", nil, err
}
config, err := images.Config(ctx, ingester, *desc, platforms.Default())
if err != nil {
return "", nil, err
}
dt, err := content.ReadBlob(ctx, ingester, config.Digest)
if err != nil {
return "", nil, err
}
return desc.Digest, dt, nil
}
func childrenConfigHandler(provider content.Provider) images.HandlerFunc {
return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
var descs []ocispec.Descriptor
switch desc.MediaType {
case images.MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
p, err := content.ReadBlob(ctx, provider, desc.Digest)
if err != nil {
return nil, err
}
// TODO(stevvooe): We just assume oci manifest, for now. There may be
// subtle differences from the docker version.
var manifest ocispec.Manifest
if err := json.Unmarshal(p, &manifest); err != nil {
return nil, err
}
descs = append(descs, manifest.Config)
case images.MediaTypeDockerSchema2ManifestList, ocispec.MediaTypeImageIndex:
p, err := content.ReadBlob(ctx, provider, desc.Digest)
if err != nil {
return nil, err
}
var index ocispec.Index
if err := json.Unmarshal(p, &index); err != nil {
return nil, err
}
descs = append(descs, index.Manifests...)
case images.MediaTypeDockerSchema2Config, ocispec.MediaTypeImageConfig:
// childless data types.
return nil, nil
default:
return nil, errors.Errorf("encountered unknown type %v; children may not be fetched", desc.MediaType)
}
return descs, nil
}
}
// ocispec.MediaTypeImageManifest, // TODO: detect schema1/manifest-list
func DetectManifestMediaType(ra content.ReaderAt) (string, error) {
// TODO: schema1
p := make([]byte, ra.Size())
if _, err := ra.ReadAt(p, 0); err != nil {
return "", err
}
var mfst struct {
Config json.RawMessage `json:"config"`
}
if err := json.Unmarshal(p, &mfst); err != nil {
return "", err
}
if mfst.Config != nil {
return images.MediaTypeDockerSchema2Manifest, nil
}
return images.MediaTypeDockerSchema2ManifestList, nil
}