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new.go
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package imgutil
import (
"crypto/sha256"
"encoding/hex"
"fmt"
"io"
"os"
"time"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/empty"
"github.com/google/go-containerregistry/pkg/v1/mutate"
"github.com/google/go-containerregistry/pkg/v1/types"
"github.com/buildpacks/imgutil/layer"
)
func NewCNBImage(options ImageOptions) (*CNBImageCore, error) {
image := &CNBImageCore{
Image: options.BaseImage, // the working image
createdAt: getCreatedAt(options),
preferredMediaTypes: GetPreferredMediaTypes(options),
preserveHistory: options.PreserveHistory,
previousImage: options.PreviousImage,
}
// ensure base image
var err error
if image.Image == nil {
image.Image, err = emptyV1(options.Platform, image.preferredMediaTypes)
if err != nil {
return nil, err
}
}
// ensure windows
if err = prepareNewWindowsImageIfNeeded(image); err != nil {
return nil, err
}
// set config if requested
if options.Config != nil {
if err = image.MutateConfigFile(func(c *v1.ConfigFile) {
c.Config = *options.Config
}); err != nil {
return nil, err
}
}
return image, nil
}
func getCreatedAt(options ImageOptions) time.Time {
if !options.CreatedAt.IsZero() {
return options.CreatedAt
}
return NormalizedDateTime
}
var NormalizedDateTime = time.Date(1980, time.January, 1, 0, 0, 1, 0, time.UTC)
func GetPreferredMediaTypes(options ImageOptions) MediaTypes {
if options.MediaTypes != MissingTypes {
return options.MediaTypes
}
if options.MediaTypes == MissingTypes &&
options.BaseImage == nil {
return OCITypes
}
return DefaultTypes
}
type MediaTypes int
const (
MissingTypes MediaTypes = iota
DefaultTypes
OCITypes
DockerTypes
)
func (t MediaTypes) ManifestType() types.MediaType {
switch t {
case OCITypes:
return types.OCIManifestSchema1
case DockerTypes:
return types.DockerManifestSchema2
default:
return ""
}
}
func (t MediaTypes) ConfigType() types.MediaType {
switch t {
case OCITypes:
return types.OCIConfigJSON
case DockerTypes:
return types.DockerConfigJSON
default:
return ""
}
}
func (t MediaTypes) LayerType() types.MediaType {
switch t {
case OCITypes:
return types.OCILayer
case DockerTypes:
return types.DockerLayer
default:
return ""
}
}
func emptyV1(withPlatform Platform, withMediaTypes MediaTypes) (v1.Image, error) {
configFile := &v1.ConfigFile{
Architecture: withPlatform.Architecture,
History: []v1.History{},
OS: withPlatform.OS,
OSVersion: withPlatform.OSVersion,
Variant: withPlatform.Variant,
RootFS: v1.RootFS{
Type: "layers",
DiffIDs: []v1.Hash{},
},
}
image, err := mutate.ConfigFile(empty.Image, configFile)
if err != nil {
return nil, err
}
image, _, err = EnsureMediaTypesAndLayers(image, withMediaTypes, PreserveLayers)
return image, err
}
func PreserveLayers(_ int, layer v1.Layer) (v1.Layer, error) {
return layer, nil
}
// EnsureMediaTypesAndLayers replaces the provided image with a new image that has the desired media types.
// It does this by constructing a manifest and config from the provided image,
// and adding the layers from the provided image to the new image with the right media type.
// If requested types are missing or default, it does nothing.
// While adding the layers, each layer can be additionally mutated by providing a "mutate layer" function.
func EnsureMediaTypesAndLayers(image v1.Image, requestedTypes MediaTypes, mutateLayer func(idx int, layer v1.Layer) (v1.Layer, error)) (v1.Image, bool, error) {
if requestedTypes == MissingTypes || requestedTypes == DefaultTypes {
return image, false, nil
}
// (1) get data from the original image
// manifest
beforeManifest, err := image.Manifest()
if err != nil {
return nil, false, fmt.Errorf("failed to get manifest: %w", err)
}
// config
beforeConfig, err := image.ConfigFile()
if err != nil {
return nil, false, fmt.Errorf("failed to get config: %w", err)
}
// layers
beforeLayers, err := image.Layers()
if err != nil {
return nil, false, fmt.Errorf("failed to get layers: %w", err)
}
var layersToAdd []v1.Layer
for idx, l := range beforeLayers {
layer, err := mutateLayer(idx, l)
if err != nil {
return nil, false, fmt.Errorf("failed to mutate layer: %w", err)
}
layersToAdd = append(layersToAdd, layer)
}
// (2) construct a new image manifest with the right media type
manifestType := requestedTypes.ManifestType()
if manifestType == "" {
manifestType = beforeManifest.MediaType
}
retImage := mutate.MediaType(empty.Image, manifestType)
// (3) set config with the right media type
configType := requestedTypes.ConfigType()
if configType == "" {
configType = beforeManifest.Config.MediaType
}
// zero out diff IDs and history, these will be added back when we append the layers
beforeHistory := beforeConfig.History
beforeConfig.History = []v1.History{}
beforeConfig.RootFS.DiffIDs = []v1.Hash{}
retImage, err = mutate.ConfigFile(retImage, beforeConfig)
if err != nil {
return nil, false, fmt.Errorf("failed to set config: %w", err)
}
retImage = mutate.ConfigMediaType(retImage, configType)
// (4) set layers with the right media type
additions := layersAddendum(layersToAdd, beforeHistory, requestedTypes.LayerType())
if err != nil {
return nil, false, err
}
retImage, err = mutate.Append(retImage, additions...)
if err != nil {
return nil, false, fmt.Errorf("failed to append layers: %w", err)
}
// (5) force compute
afterLayers, err := retImage.Layers()
if err != nil {
return nil, false, fmt.Errorf("failed to get layers: %w", err)
}
if len(afterLayers) != len(beforeLayers) {
return nil, false, fmt.Errorf("expected %d layers; got %d", len(beforeLayers), len(afterLayers))
}
return retImage, true, nil
}
// layersAddendum creates an Addendum array with the given layers
// and the desired media type
func layersAddendum(layers []v1.Layer, history []v1.History, requestedType types.MediaType) []mutate.Addendum {
addendums := make([]mutate.Addendum, 0)
history = NormalizedHistory(history, len(layers))
if len(history) != len(layers) {
history = make([]v1.History, len(layers))
}
var err error
for idx, l := range layers {
layerType := requestedType
if requestedType == "" {
// try to get a non-empty media type
if layerType, err = l.MediaType(); err != nil {
layerType = ""
}
}
addendums = append(addendums, mutate.Addendum{
Layer: l,
History: history[idx],
MediaType: layerType,
})
}
return addendums
}
func NormalizedHistory(history []v1.History, nLayers int) []v1.History {
if history == nil {
return make([]v1.History, nLayers)
}
// ensure we remove history for empty layers
var normalizedHistory []v1.History
for _, h := range history {
if !h.EmptyLayer {
normalizedHistory = append(normalizedHistory, h)
}
}
if len(normalizedHistory) == nLayers {
return normalizedHistory
}
return make([]v1.History, nLayers)
}
func prepareNewWindowsImageIfNeeded(image *CNBImageCore) error {
configFile, err := getConfigFile(image)
if err != nil {
return err
}
// only append base layer to empty image
if !(configFile.OS == "windows") || len(configFile.RootFS.DiffIDs) > 0 {
return nil
}
layerReader, err := layer.WindowsBaseLayer()
if err != nil {
return err
}
layerFile, err := os.CreateTemp("", "imgutil.local.image.windowsbaselayer")
if err != nil {
return fmt.Errorf("creating temp file: %w", err)
}
defer layerFile.Close()
hasher := sha256.New()
multiWriter := io.MultiWriter(layerFile, hasher)
if _, err := io.Copy(multiWriter, layerReader); err != nil {
return fmt.Errorf("copying base layer: %w", err)
}
diffID := "sha256:" + hex.EncodeToString(hasher.Sum(nil))
if err = image.AddLayerWithDiffIDAndHistory(layerFile.Name(), diffID, v1.History{}); err != nil {
return fmt.Errorf("adding base layer to image: %w", err)
}
return nil
}
func NewCNBIndex(repoName string, options IndexOptions) (*CNBIndex, error) {
if options.BaseIndex == nil {
switch options.MediaType {
case types.DockerManifestList:
options.BaseIndex = NewEmptyDockerIndex()
default:
options.BaseIndex = empty.Index
}
}
index := &CNBIndex{
RepoName: repoName,
ImageIndex: options.BaseIndex,
XdgPath: options.XdgPath,
KeyChain: options.Keychain,
}
return index, nil
}
func NewTaggableIndex(manifest *v1.IndexManifest) *TaggableIndex {
return &TaggableIndex{
IndexManifest: manifest,
}
}