/
default.go
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/
default.go
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/*
Copyright The containerd Authors.
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 converter
import (
"bytes"
"context"
"encoding/json"
"fmt"
"strings"
"sync"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/platforms"
"github.com/opencontainers/go-digest"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/sirupsen/logrus"
"golang.org/x/sync/errgroup"
)
// ConvertFunc returns a converted content descriptor.
// When the content was not converted, ConvertFunc returns nil.
type ConvertFunc func(ctx context.Context, cs content.Store, desc ocispec.Descriptor) (*ocispec.Descriptor, error)
// DefaultIndexConvertFunc is the default convert func used by Convert.
func DefaultIndexConvertFunc(layerConvertFunc ConvertFunc, docker2oci bool, platformMC platforms.MatchComparer) ConvertFunc {
c := &defaultConverter{
layerConvertFunc: layerConvertFunc,
docker2oci: docker2oci,
platformMC: platformMC,
diffIDMap: make(map[digest.Digest]digest.Digest),
}
return c.convert
}
// ConvertHookFunc is a callback function called during conversion of a blob.
// orgDesc is the target descriptor to convert. newDesc is passed if conversion happens.
type ConvertHookFunc func(ctx context.Context, cs content.Store, orgDesc ocispec.Descriptor, newDesc *ocispec.Descriptor) (*ocispec.Descriptor, error)
// ConvertHooks is a configuration for hook callbacks called during blob conversion.
type ConvertHooks struct {
// PostConvertHook is a callback function called for each blob after conversion is done.
PostConvertHook ConvertHookFunc
}
// IndexConvertFuncWithHook is the convert func used by Convert with hook functions support.
func IndexConvertFuncWithHook(layerConvertFunc ConvertFunc, docker2oci bool, platformMC platforms.MatchComparer, hooks ConvertHooks) ConvertFunc {
c := &defaultConverter{
layerConvertFunc: layerConvertFunc,
docker2oci: docker2oci,
platformMC: platformMC,
diffIDMap: make(map[digest.Digest]digest.Digest),
hooks: hooks,
}
return c.convert
}
type defaultConverter struct {
layerConvertFunc ConvertFunc
docker2oci bool
platformMC platforms.MatchComparer
diffIDMap map[digest.Digest]digest.Digest // key: old diffID, value: new diffID
diffIDMapMu sync.RWMutex
hooks ConvertHooks
}
// convert dispatches desc.MediaType and calls c.convert{Layer,Manifest,Index,Config}.
//
// Also converts media type if c.docker2oci is set.
func (c *defaultConverter) convert(ctx context.Context, cs content.Store, desc ocispec.Descriptor) (*ocispec.Descriptor, error) {
var (
newDesc *ocispec.Descriptor
err error
)
if images.IsLayerType(desc.MediaType) {
newDesc, err = c.convertLayer(ctx, cs, desc)
} else if images.IsManifestType(desc.MediaType) {
newDesc, err = c.convertManifest(ctx, cs, desc)
} else if images.IsIndexType(desc.MediaType) {
newDesc, err = c.convertIndex(ctx, cs, desc)
} else if images.IsConfigType(desc.MediaType) {
newDesc, err = c.convertConfig(ctx, cs, desc)
}
if err != nil {
return nil, err
}
if c.hooks.PostConvertHook != nil {
if newDescPost, err := c.hooks.PostConvertHook(ctx, cs, desc, newDesc); err != nil {
return nil, err
} else if newDescPost != nil {
newDesc = newDescPost
}
}
if images.IsDockerType(desc.MediaType) {
if c.docker2oci {
if newDesc == nil {
newDesc = copyDesc(desc)
}
newDesc.MediaType = ConvertDockerMediaTypeToOCI(newDesc.MediaType)
} else if (newDesc == nil && len(desc.Annotations) != 0) || (newDesc != nil && len(newDesc.Annotations) != 0) {
// Annotations is supported only on OCI manifest.
// We need to remove annotations for Docker media types.
if newDesc == nil {
newDesc = copyDesc(desc)
}
newDesc.Annotations = nil
}
}
logrus.WithField("old", desc).WithField("new", newDesc).Debugf("converted")
return newDesc, nil
}
func copyDesc(desc ocispec.Descriptor) *ocispec.Descriptor {
descCopy := desc
return &descCopy
}
// convertLayer converts image layers if c.layerConvertFunc is set.
//
// c.layerConvertFunc can be nil, e.g., for converting Docker media types to OCI ones.
func (c *defaultConverter) convertLayer(ctx context.Context, cs content.Store, desc ocispec.Descriptor) (*ocispec.Descriptor, error) {
if c.layerConvertFunc != nil {
return c.layerConvertFunc(ctx, cs, desc)
}
return nil, nil
}
// convertManifest converts image manifests.
//
// - converts `.mediaType` if the target format is OCI
// - records diff ID changes in c.diffIDMap
func (c *defaultConverter) convertManifest(ctx context.Context, cs content.Store, desc ocispec.Descriptor) (*ocispec.Descriptor, error) {
var (
manifest ocispec.Manifest
modified bool
)
labels, err := readJSON(ctx, cs, &manifest, desc)
if err != nil {
return nil, err
}
if labels == nil {
labels = make(map[string]string)
}
if images.IsDockerType(manifest.MediaType) && c.docker2oci {
manifest.MediaType = ConvertDockerMediaTypeToOCI(manifest.MediaType)
modified = true
}
var mu sync.Mutex
eg, ctx2 := errgroup.WithContext(ctx)
for i, l := range manifest.Layers {
i := i
l := l
oldDiffID, err := images.GetDiffID(ctx, cs, l)
if err != nil {
return nil, err
}
eg.Go(func() error {
newL, err := c.convert(ctx2, cs, l)
if err != nil {
return err
}
if newL != nil {
mu.Lock()
// update GC labels
ClearGCLabels(labels, l.Digest)
labelKey := fmt.Sprintf("containerd.io/gc.ref.content.l.%d", i)
labels[labelKey] = newL.Digest.String()
manifest.Layers[i] = *newL
modified = true
mu.Unlock()
// diffID changes if the tar entries were modified.
// diffID stays same if only the compression type was changed.
// When diffID changed, add a map entry so that we can update image config.
newDiffID, err := images.GetDiffID(ctx, cs, *newL)
if err != nil {
return err
}
if newDiffID != oldDiffID {
c.diffIDMapMu.Lock()
c.diffIDMap[oldDiffID] = newDiffID
c.diffIDMapMu.Unlock()
}
}
return nil
})
}
if err := eg.Wait(); err != nil {
return nil, err
}
newConfig, err := c.convert(ctx, cs, manifest.Config)
if err != nil {
return nil, err
}
if newConfig != nil {
ClearGCLabels(labels, manifest.Config.Digest)
labels["containerd.io/gc.ref.content.config"] = newConfig.Digest.String()
manifest.Config = *newConfig
modified = true
}
if modified {
return writeJSON(ctx, cs, &manifest, desc, labels)
}
return nil, nil
}
// convertIndex converts image index.
//
// - converts `.mediaType` if the target format is OCI
// - clears manifest entries that do not match c.platformMC
func (c *defaultConverter) convertIndex(ctx context.Context, cs content.Store, desc ocispec.Descriptor) (*ocispec.Descriptor, error) {
var (
index ocispec.Index
modified bool
)
labels, err := readJSON(ctx, cs, &index, desc)
if err != nil {
return nil, err
}
if labels == nil {
labels = make(map[string]string)
}
if images.IsDockerType(index.MediaType) && c.docker2oci {
index.MediaType = ConvertDockerMediaTypeToOCI(index.MediaType)
modified = true
}
newManifests := make([]ocispec.Descriptor, len(index.Manifests))
newManifestsToBeRemoved := make(map[int]struct{}) // slice index
var mu sync.Mutex
eg, ctx2 := errgroup.WithContext(ctx)
for i, mani := range index.Manifests {
i := i
mani := mani
labelKey := fmt.Sprintf("containerd.io/gc.ref.content.m.%d", i)
eg.Go(func() error {
if mani.Platform != nil && !c.platformMC.Match(*mani.Platform) {
mu.Lock()
ClearGCLabels(labels, mani.Digest)
newManifestsToBeRemoved[i] = struct{}{}
modified = true
mu.Unlock()
return nil
}
newMani, err := c.convert(ctx2, cs, mani)
if err != nil {
return err
}
mu.Lock()
if newMani != nil {
ClearGCLabels(labels, mani.Digest)
labels[labelKey] = newMani.Digest.String()
// NOTE: for keeping manifest order, we specify `i` index explicitly
newManifests[i] = *newMani
modified = true
} else {
newManifests[i] = mani
}
mu.Unlock()
return nil
})
}
if err := eg.Wait(); err != nil {
return nil, err
}
if modified {
var newManifestsClean []ocispec.Descriptor
for i, m := range newManifests {
if _, ok := newManifestsToBeRemoved[i]; !ok {
newManifestsClean = append(newManifestsClean, m)
}
}
index.Manifests = newManifestsClean
return writeJSON(ctx, cs, &index, desc, labels)
}
return nil, nil
}
// convertConfig converts image config contents.
//
// - updates `.rootfs.diff_ids` using c.diffIDMap .
//
// - clears legacy `.config.Image` and `.container_config.Image` fields if `.rootfs.diff_ids` was updated.
func (c *defaultConverter) convertConfig(ctx context.Context, cs content.Store, desc ocispec.Descriptor) (*ocispec.Descriptor, error) {
var (
cfg DualConfig
cfgAsOCI ocispec.Image // read only, used for parsing cfg
modified bool
)
labels, err := readJSON(ctx, cs, &cfg, desc)
if err != nil {
return nil, err
}
if labels == nil {
labels = make(map[string]string)
}
if _, err := readJSON(ctx, cs, &cfgAsOCI, desc); err != nil {
return nil, err
}
if rootfs := cfgAsOCI.RootFS; rootfs.Type == "layers" {
rootfsModified := false
c.diffIDMapMu.RLock()
for i, oldDiffID := range rootfs.DiffIDs {
if newDiffID, ok := c.diffIDMap[oldDiffID]; ok && newDiffID != oldDiffID {
rootfs.DiffIDs[i] = newDiffID
rootfsModified = true
}
}
c.diffIDMapMu.RUnlock()
if rootfsModified {
rootfsB, err := json.Marshal(rootfs)
if err != nil {
return nil, err
}
cfg["rootfs"] = (*json.RawMessage)(&rootfsB)
modified = true
}
}
if modified {
// cfg may have dummy value for legacy `.config.Image` and `.container_config.Image`
// We should clear the ID if we changed the diff IDs.
if _, err := clearDockerV1DummyID(cfg); err != nil {
return nil, err
}
return writeJSON(ctx, cs, &cfg, desc, labels)
}
return nil, nil
}
// clearDockerV1DummyID clears the dummy values for legacy `.config.Image` and `.container_config.Image`.
// Returns true if the cfg was modified.
func clearDockerV1DummyID(cfg DualConfig) (bool, error) {
var modified bool
f := func(k string) error {
if configX, ok := cfg[k]; ok && configX != nil {
var configField map[string]*json.RawMessage
if err := json.Unmarshal(*configX, &configField); err != nil {
return err
}
delete(configField, "Image")
b, err := json.Marshal(configField)
if err != nil {
return err
}
cfg[k] = (*json.RawMessage)(&b)
modified = true
}
return nil
}
if err := f("config"); err != nil {
return modified, err
}
if err := f("container_config"); err != nil {
return modified, err
}
return modified, nil
}
// DualConfig covers Docker config (v1.0, v1.1, v1.2) and OCI config.
// Unmarshalled as map[string]*json.RawMessage to retain unknown fields on remarshalling.
type DualConfig map[string]*json.RawMessage
func readJSON(ctx context.Context, cs content.Store, x interface{}, desc ocispec.Descriptor) (map[string]string, error) {
info, err := cs.Info(ctx, desc.Digest)
if err != nil {
return nil, err
}
labels := info.Labels
b, err := content.ReadBlob(ctx, cs, desc)
if err != nil {
return nil, err
}
if err := json.Unmarshal(b, x); err != nil {
return nil, err
}
return labels, nil
}
func writeJSON(ctx context.Context, cs content.Store, x interface{}, oldDesc ocispec.Descriptor, labels map[string]string) (*ocispec.Descriptor, error) {
b, err := json.Marshal(x)
if err != nil {
return nil, err
}
dgst := digest.SHA256.FromBytes(b)
ref := fmt.Sprintf("converter-write-json-%s", dgst.String())
w, err := content.OpenWriter(ctx, cs, content.WithRef(ref))
if err != nil {
return nil, err
}
if err := content.Copy(ctx, w, bytes.NewReader(b), int64(len(b)), dgst, content.WithLabels(labels)); err != nil {
w.Close()
return nil, err
}
if err := w.Close(); err != nil {
return nil, err
}
newDesc := oldDesc
newDesc.Size = int64(len(b))
newDesc.Digest = dgst
return &newDesc, nil
}
// ConvertDockerMediaTypeToOCI converts a media type string
func ConvertDockerMediaTypeToOCI(mt string) string {
switch mt {
case images.MediaTypeDockerSchema2ManifestList:
return ocispec.MediaTypeImageIndex
case images.MediaTypeDockerSchema2Manifest:
return ocispec.MediaTypeImageManifest
case images.MediaTypeDockerSchema2LayerGzip:
return ocispec.MediaTypeImageLayerGzip
case images.MediaTypeDockerSchema2LayerForeignGzip:
return ocispec.MediaTypeImageLayerNonDistributableGzip
case images.MediaTypeDockerSchema2Layer:
return ocispec.MediaTypeImageLayer
case images.MediaTypeDockerSchema2LayerForeign:
return ocispec.MediaTypeImageLayerNonDistributable
case images.MediaTypeDockerSchema2Config:
return ocispec.MediaTypeImageConfig
default:
return mt
}
}
// ClearGCLabels clears GC labels for the given digest.
func ClearGCLabels(labels map[string]string, dgst digest.Digest) {
for k, v := range labels {
if v == dgst.String() && strings.HasPrefix(k, "containerd.io/gc.ref.content") {
delete(labels, k)
}
}
}