/
oci.go
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/
oci.go
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package manifest
import (
"encoding/json"
"fmt"
"strings"
"github.com/containers/image/v5/internal/manifest"
compressiontypes "github.com/containers/image/v5/pkg/compression/types"
"github.com/containers/image/v5/types"
ociencspec "github.com/containers/ocicrypt/spec"
"github.com/opencontainers/go-digest"
"github.com/opencontainers/image-spec/specs-go"
imgspecv1 "github.com/opencontainers/image-spec/specs-go/v1"
"golang.org/x/exp/slices"
)
// BlobInfoFromOCI1Descriptor returns a types.BlobInfo based on the input OCI1 descriptor.
func BlobInfoFromOCI1Descriptor(desc imgspecv1.Descriptor) types.BlobInfo {
return types.BlobInfo{
Digest: desc.Digest,
Size: desc.Size,
URLs: desc.URLs,
Annotations: desc.Annotations,
MediaType: desc.MediaType,
}
}
// OCI1 is a manifest.Manifest implementation for OCI images.
// The underlying data from imgspecv1.Manifest is also available.
type OCI1 struct {
imgspecv1.Manifest
}
// SupportedOCI1MediaType checks if the specified string is a supported OCI1
// media type.
//
// Deprecated: blindly rejecting unknown MIME types when the consumer does not
// need to process the input just reduces interoperability (and violates the
// standard) with no benefit, and that this function does not check that the
// media type is appropriate for any specific purpose, so it’s not all that
// useful for validation anyway.
func SupportedOCI1MediaType(m string) error {
switch m {
case imgspecv1.MediaTypeDescriptor, imgspecv1.MediaTypeImageConfig,
imgspecv1.MediaTypeImageLayer, imgspecv1.MediaTypeImageLayerGzip, imgspecv1.MediaTypeImageLayerZstd,
imgspecv1.MediaTypeImageLayerNonDistributable, imgspecv1.MediaTypeImageLayerNonDistributableGzip, imgspecv1.MediaTypeImageLayerNonDistributableZstd, //nolint:staticcheck // NonDistributable layers are deprecated, but we want to continue to support manipulating pre-existing images.
imgspecv1.MediaTypeImageManifest,
imgspecv1.MediaTypeLayoutHeader,
ociencspec.MediaTypeLayerEnc, ociencspec.MediaTypeLayerGzipEnc:
return nil
default:
return fmt.Errorf("unsupported OCIv1 media type: %q", m)
}
}
// OCI1FromManifest creates an OCI1 manifest instance from a manifest blob.
func OCI1FromManifest(manifestBlob []byte) (*OCI1, error) {
oci1 := OCI1{}
if err := json.Unmarshal(manifestBlob, &oci1); err != nil {
return nil, err
}
if err := manifest.ValidateUnambiguousManifestFormat(manifestBlob, imgspecv1.MediaTypeImageIndex,
manifest.AllowedFieldConfig|manifest.AllowedFieldLayers); err != nil {
return nil, err
}
return &oci1, nil
}
// OCI1FromComponents creates an OCI1 manifest instance from the supplied data.
func OCI1FromComponents(config imgspecv1.Descriptor, layers []imgspecv1.Descriptor) *OCI1 {
return &OCI1{
imgspecv1.Manifest{
Versioned: specs.Versioned{SchemaVersion: 2},
MediaType: imgspecv1.MediaTypeImageManifest,
Config: config,
Layers: layers,
},
}
}
// OCI1Clone creates a copy of the supplied OCI1 manifest.
func OCI1Clone(src *OCI1) *OCI1 {
return &OCI1{
Manifest: src.Manifest,
}
}
// ConfigInfo returns a complete BlobInfo for the separate config object, or a BlobInfo{Digest:""} if there isn't a separate object.
func (m *OCI1) ConfigInfo() types.BlobInfo {
return BlobInfoFromOCI1Descriptor(m.Config)
}
// LayerInfos returns a list of LayerInfos of layers referenced by this image, in order (the root layer first, and then successive layered layers).
// The Digest field is guaranteed to be provided; Size may be -1.
// WARNING: The list may contain duplicates, and they are semantically relevant.
func (m *OCI1) LayerInfos() []LayerInfo {
blobs := []LayerInfo{}
for _, layer := range m.Layers {
blobs = append(blobs, LayerInfo{
BlobInfo: BlobInfoFromOCI1Descriptor(layer),
EmptyLayer: false,
})
}
return blobs
}
var oci1CompressionMIMETypeSets = []compressionMIMETypeSet{
{
mtsUncompressed: imgspecv1.MediaTypeImageLayerNonDistributable, //nolint:staticcheck // NonDistributable layers are deprecated, but we want to continue to support manipulating pre-existing images.
compressiontypes.GzipAlgorithmName: imgspecv1.MediaTypeImageLayerNonDistributableGzip, //nolint:staticcheck // NonDistributable layers are deprecated, but we want to continue to support manipulating pre-existing images.
compressiontypes.ZstdAlgorithmName: imgspecv1.MediaTypeImageLayerNonDistributableZstd, //nolint:staticcheck // NonDistributable layers are deprecated, but we want to continue to support manipulating pre-existing images.
},
{
mtsUncompressed: imgspecv1.MediaTypeImageLayer,
compressiontypes.GzipAlgorithmName: imgspecv1.MediaTypeImageLayerGzip,
compressiontypes.ZstdAlgorithmName: imgspecv1.MediaTypeImageLayerZstd,
},
}
// UpdateLayerInfos replaces the original layers with the specified BlobInfos (size+digest+urls+mediatype), in order (the root layer first, and then successive layered layers)
// The returned error will be a manifest.ManifestLayerCompressionIncompatibilityError if any of the layerInfos includes a combination of CompressionOperation and
// CompressionAlgorithm that isn't supported by OCI.
//
// It’s generally the caller’s responsibility to determine whether a particular edit is acceptable, rather than relying on
// failures of this function, because the layer is typically created _before_ UpdateLayerInfos is called, because UpdateLayerInfos needs
// to know the final digest). See OCI1.CanChangeLayerCompression for some help in determining this; other aspects like compression
// algorithms that might not be supported by a format, or the limited set of MIME types accepted for encryption, are not currently
// handled — that logic should eventually also be provided as OCI1 methods, not hard-coded in callers.
func (m *OCI1) UpdateLayerInfos(layerInfos []types.BlobInfo) error {
if len(m.Layers) != len(layerInfos) {
return fmt.Errorf("Error preparing updated manifest: layer count changed from %d to %d", len(m.Layers), len(layerInfos))
}
original := m.Layers
m.Layers = make([]imgspecv1.Descriptor, len(layerInfos))
for i, info := range layerInfos {
mimeType := original[i].MediaType
if info.CryptoOperation == types.Decrypt {
decMimeType, err := getDecryptedMediaType(mimeType)
if err != nil {
return fmt.Errorf("error preparing updated manifest: decryption specified but original mediatype is not encrypted: %q", mimeType)
}
mimeType = decMimeType
}
mimeType, err := updatedMIMEType(oci1CompressionMIMETypeSets, mimeType, info)
if err != nil {
return fmt.Errorf("preparing updated manifest, layer %q: %w", info.Digest, err)
}
if info.CryptoOperation == types.Encrypt {
encMediaType, err := getEncryptedMediaType(mimeType)
if err != nil {
return fmt.Errorf("error preparing updated manifest: encryption specified but no counterpart for mediatype: %q", mimeType)
}
mimeType = encMediaType
}
m.Layers[i].MediaType = mimeType
m.Layers[i].Digest = info.Digest
m.Layers[i].Size = info.Size
m.Layers[i].Annotations = info.Annotations
m.Layers[i].URLs = info.URLs
}
return nil
}
// getEncryptedMediaType will return the mediatype to its encrypted counterpart and return
// an error if the mediatype does not support encryption
func getEncryptedMediaType(mediatype string) (string, error) {
if slices.Contains(strings.Split(mediatype, "+")[1:], "encrypted") {
return "", fmt.Errorf("unsupported mediaType: %v already encrypted", mediatype)
}
unsuffixedMediatype := strings.Split(mediatype, "+")[0]
switch unsuffixedMediatype {
case DockerV2Schema2LayerMediaType, imgspecv1.MediaTypeImageLayer,
imgspecv1.MediaTypeImageLayerNonDistributable: //nolint:staticcheck // NonDistributable layers are deprecated, but we want to continue to support manipulating pre-existing images.
return mediatype + "+encrypted", nil
}
return "", fmt.Errorf("unsupported mediaType to encrypt: %v", mediatype)
}
// getEncryptedMediaType will return the mediatype to its encrypted counterpart and return
// an error if the mediatype does not support decryption
func getDecryptedMediaType(mediatype string) (string, error) {
if !strings.HasSuffix(mediatype, "+encrypted") {
return "", fmt.Errorf("unsupported mediaType to decrypt: %v", mediatype)
}
return strings.TrimSuffix(mediatype, "+encrypted"), nil
}
// Serialize returns the manifest in a blob format.
// NOTE: Serialize() does not in general reproduce the original blob if this object was loaded from one, even if no modifications were made!
func (m *OCI1) Serialize() ([]byte, error) {
return json.Marshal(*m)
}
// Inspect returns various information for (skopeo inspect) parsed from the manifest and configuration.
func (m *OCI1) Inspect(configGetter func(types.BlobInfo) ([]byte, error)) (*types.ImageInspectInfo, error) {
if m.Config.MediaType != imgspecv1.MediaTypeImageConfig {
// We could return at least the layers, but that’s already available in a better format via types.Image.LayerInfos.
// Most software calling this without human intervention is going to expect the values to be realistic and relevant,
// and is probably better served by failing; we can always re-visit that later if we fail now, but
// if we started returning some data for OCI artifacts now, we couldn’t start failing in this function later.
return nil, manifest.NewNonImageArtifactError(&m.Manifest)
}
config, err := configGetter(m.ConfigInfo())
if err != nil {
return nil, err
}
v1 := &imgspecv1.Image{}
if err := json.Unmarshal(config, v1); err != nil {
return nil, err
}
d1 := &Schema2V1Image{}
if err := json.Unmarshal(config, d1); err != nil {
return nil, err
}
layerInfos := m.LayerInfos()
i := &types.ImageInspectInfo{
Tag: "",
Created: v1.Created,
DockerVersion: d1.DockerVersion,
Labels: v1.Config.Labels,
Architecture: v1.Architecture,
Variant: v1.Variant,
Os: v1.OS,
Layers: layerInfosToStrings(layerInfos),
LayersData: imgInspectLayersFromLayerInfos(layerInfos),
Env: v1.Config.Env,
Author: v1.Author,
}
return i, nil
}
// ImageID computes an ID which can uniquely identify this image by its contents.
func (m *OCI1) ImageID(diffIDs []digest.Digest) (string, error) {
// The way m.Config.Digest “uniquely identifies” an image is
// by containing RootFS.DiffIDs, which identify the layers of the image.
// For non-image artifacts, the we can’t expect the config to change
// any time the other layers (semantically) change, so this approach of
// distinguishing objects only by m.Config.Digest doesn’t work in general.
//
// Any caller of this method presumably wants to disambiguate the same
// images with a different representation, but doesn’t want to disambiguate
// representations (by using a manifest digest). So, submitting a non-image
// artifact to such a caller indicates an expectation mismatch.
// So, we just fail here instead of inventing some other ID value (e.g.
// by combining the config and blob layer digests). That still
// gives us the option to not fail, and return some value, in the future,
// without committing to that approach now.
// (The only known caller of ImageID is storage/storageImageDestination.computeID,
// which can’t work with non-image artifacts.)
if m.Config.MediaType != imgspecv1.MediaTypeImageConfig {
return "", manifest.NewNonImageArtifactError(&m.Manifest)
}
if err := m.Config.Digest.Validate(); err != nil {
return "", err
}
return m.Config.Digest.Hex(), nil
}
// CanChangeLayerCompression returns true if we can compress/decompress layers with mimeType in the current image
// (and the code can handle that).
// NOTE: Even if this returns true, the relevant format might not accept all compression algorithms; the set of accepted
// algorithms depends not on the current format, but possibly on the target of a conversion.
func (m *OCI1) CanChangeLayerCompression(mimeType string) bool {
if m.Config.MediaType != imgspecv1.MediaTypeImageConfig {
return false
}
return compressionVariantsRecognizeMIMEType(oci1CompressionMIMETypeSets, mimeType)
}