Generalise fetcher function, incorporate raw manifests

manifest/imageresolver/imageresolver.go

@@ -98,7 +98,7 @@ func (c *RegistryResolver) FindRelatedFromIndecies(ctx context.Context, images *
 	manifests := types.NewImageList(images.Dir())
 	for i := range images.Items() {
 		image := images.Items()[i]
-		imageIndex, indexManifest, _, err := c.IndexOrImage(ctx, image.Ref(true))
+		imageIndex, indexManifest, _, err := c.GetIndexOrImage(ctx, image.Ref(true))
 		if err != nil {
 			return nil, nil, err
 		}

oci/artefact.go

@@ -6,6 +6,7 @@ import (
 	"compress/gzip"
 	"context"
 	"encoding/hex"
+	"encoding/json"
 	"fmt"
 	"io"
 	"maps"
@@ -42,25 +43,27 @@ const (
 	// TODO: content interpreter invocation with an image
 
 	regularFileMode = 0o640
+
+	OCIManifestSchema1 = typesv1.OCIManifestSchema1
 )
 
-type ArtefactInfo struct {
+type ImageInfo struct {
 	io.ReadCloser
 
 	MediaType   MediaType
 	Annotations map[string]string
 	Digest      string
 }
 
-func (c *Client) SelectArtefacts(ctx context.Context, ref string, mediaTypes ...MediaType) ([]*ArtefactInfo, error) {
-	imageIndex, indexManifest, image, err := c.IndexOrImage(ctx, ref)
+func (c *Client) Fetch(ctx context.Context, ref string, mediaTypes ...MediaType) ([]*ImageInfo, error) {
+	imageIndex, indexManifest, image, err := c.GetIndexOrImage(ctx, ref)
 	if err != nil {
 		return nil, err
 	}
-	return c.SelectArtefactsFromIndexOrImage(ctx, imageIndex, indexManifest, image, mediaTypes...)
+	return c.FetchFromIndexOrImage(ctx, imageIndex, indexManifest, image, mediaTypes...)
 }
 
-func (c *Client) SelectArtefactsFromIndexOrImage(ctx context.Context, imageIndex v1.ImageIndex, indexManifest *v1.IndexManifest, image v1.Image, mediaTypes ...MediaType) ([]*ArtefactInfo, error) {
+func (c *Client) FetchFromIndexOrImage(ctx context.Context, imageIndex v1.ImageIndex, indexManifest *v1.IndexManifest, image v1.Image, mediaTypes ...MediaType) ([]*ImageInfo, error) {
 	numMediaTypes := len(mediaTypes)
 
 	selector := make(map[MediaType]struct{}, numMediaTypes)
@@ -77,7 +80,7 @@ func (c *Client) SelectArtefactsFromIndexOrImage(ctx context.Context, imageIndex
 		return false
 	}
 
-	artefacts := []*ArtefactInfo{}
+	artefacts := []*ImageInfo{}
 
 	if indexManifest == nil {
 		manifest, err := image.Manifest()
@@ -112,6 +115,8 @@ func (c *Client) SelectArtefactsFromIndexOrImage(ctx context.Context, imageIndex
 			return nil, err
 		}
 
+		artefacts = append(artefacts, newManifestDataReader(manifest, manifestDescriptor.Digest))
+
 		for j := range manifest.Layers {
 			layerDescriptor := manifest.Layers[j]
 
@@ -130,7 +135,27 @@ func (c *Client) SelectArtefactsFromIndexOrImage(ctx context.Context, imageIndex
 	return artefacts, nil
 }
 
-func (c *Client) GetSingleArtefact(ctx context.Context, ref string) (*ArtefactInfo, error) {
+func newManifestDataReader(manifest *v1.Manifest, digest v1.Hash) *ImageInfo {
+	return &ImageInfo{
+		ReadCloser: io.NopCloser((*manifestDataReader)(manifest)),
+		MediaType:  OCIManifestSchema1,
+		Digest:     digest.String(),
+	}
+}
+
+type manifestDataReader v1.Manifest
+
+func (m *manifestDataReader) Read(p []byte) (int, error) {
+	if m == nil {
+		return 0, io.EOF
+	}
+	if err := json.NewEncoder(bytes.NewBuffer(p)).Encode(m); err != nil {
+		return 0, err
+	}
+	return len(p), nil
+}
+
+func (c *Client) GetSingleArtefact(ctx context.Context, ref string) (*ImageInfo, error) {
 	image, layers, err := c.getFlatArtefactLayers(ctx, ref)
 	if err != nil {
 		return nil, err
@@ -141,7 +166,7 @@ func (c *Client) GetSingleArtefact(ctx context.Context, ref string) (*ArtefactIn
 	return newArtifcatInfoFromLayerDescriptor(image, layers[0])
 }
 
-func newArtifcatInfoFromLayerDescriptor(image v1.Image, layerDecriptor v1.Descriptor) (*ArtefactInfo, error) {
+func newArtifcatInfoFromLayerDescriptor(image v1.Image, layerDecriptor v1.Descriptor) (*ImageInfo, error) {
 	layer, err := image.LayerByDigest(layerDecriptor.Digest)
 	if err != nil {
 		return nil, fmt.Errorf("fetching artefact image failed: %w", err)
@@ -151,7 +176,7 @@ func newArtifcatInfoFromLayerDescriptor(image v1.Image, layerDecriptor v1.Descri
 	if err != nil {
 		return nil, fmt.Errorf("extracting compressed aretefact image failed: %w", err)
 	}
-	info := &ArtefactInfo{
+	info := &ImageInfo{
 		ReadCloser:  blob,
 		MediaType:   layerDecriptor.MediaType,
 		Annotations: layerDecriptor.Annotations,
@@ -161,7 +186,7 @@ func newArtifcatInfoFromLayerDescriptor(image v1.Image, layerDecriptor v1.Descri
 }
 
 func (c *Client) getFlatArtefactLayers(ctx context.Context, ref string) (v1.Image, []v1.Descriptor, error) {
-	imageIndex, indexManifest, image, err := c.IndexOrImage(ctx, ref)
+	imageIndex, indexManifest, image, err := c.GetIndexOrImage(ctx, ref)
 	if err != nil {
 		return nil, nil, err
 	}

oci/oci.go

@@ -90,7 +90,7 @@ func (c *Client) Copy(ctx context.Context, srcRef, dstRef, digest string) error
 	return nil
 }
 
-func (c *Client) IndexOrImage(ctx context.Context, ref string) (v1.ImageIndex, *v1.IndexManifest, v1.Image, error) {
+func (c *Client) GetIndexOrImage(ctx context.Context, ref string) (v1.ImageIndex, *v1.IndexManifest, v1.Image, error) {
 	parsedRef, err := name.ParseReference(ref)
 	if err != nil {
 		return nil, nil, nil, fmt.Errorf("invalid URL %q: %w", ref, err)

tape/app/images.go

@@ -166,7 +166,7 @@ func (c *TapeImagesCommand) CollectInfo(ctx context.Context, images *types.Image
 			})
 		}
 
-		artefacts, err := client.SelectArtefactsFromIndexOrImage(ctx, imageIndex, indexManifest, nil, "application/vnd.in-toto+json")
+		artefacts, err := client.FetchFromIndexOrImage(ctx, imageIndex, indexManifest, nil, "application/vnd.in-toto+json")
 		if err != nil {
 			return fmt.Errorf("failed to fetch inline attestation: %w", err)
 		}

tape/app/pull.go

@@ -34,7 +34,7 @@ func (c *TapePullCommand) Execute(args []string) error {
 
 	client := oci.NewClient(nil)
 
-	artefacts, err := client.SelectArtefacts(ctx, c.Image, oci.ContentMediaType, oci.AttestMediaType)
+	artefacts, err := client.Fetch(ctx, c.Image, oci.ContentMediaType, oci.AttestMediaType)
 	if err != nil {
 		return err
 	}