Rework methods for pulling artefacts

oci/artefact.go

@@ -52,49 +52,80 @@ type ArtefactInfo struct {
 	Annotations map[string]string
 }
 
-func (c *Client) GetArtefact(ctx context.Context, ref string) (*ArtefactInfo, error) {
-	artefacts, err := c.GetArtefacts(ctx, ref)
+func (c *Client) SelectArtefacts(ctx context.Context, ref string, mediaTypes ...string) ([]*ArtefactInfo, error) {
+	image, layers, err := c.getArtefactLayers(ctx, ref)
 	if err != nil {
 		return nil, err
 	}
-	if len(artefacts) != 1 {
+
+	numMediaTypes := len(mediaTypes)
+	selectAll := numMediaTypes == 0
+
+	selector := make(map[string]struct{}, numMediaTypes)
+	for _, mediaType := range mediaTypes {
+		selector[mediaType] = struct{}{}
+	}
+
+	artefacts := []*ArtefactInfo{}
+	for _, layerDecriptor := range layers {
+		if !selectAll {
+			if _, ok := selector[string(layerDecriptor.MediaType)]; !ok {
+				continue
+			}
+		}
+		info, err := newArtifcatInfoFromLayerDescriptor(image, layerDecriptor)
+		if err != nil {
+			return nil, err
+		}
+		artefacts = append(artefacts, info)
+	}
+	if !selectAll && len(artefacts) == 0 {
+		return nil, fmt.Errorf("no artefacts found in image %q matching media types %q", ref, mediaTypes)
+	}
+	return artefacts, nil
+}
+
+func (c *Client) GetSingleArtefact(ctx context.Context, ref string) (*ArtefactInfo, error) {
+	image, layers, err := c.getArtefactLayers(ctx, ref)
+	if err != nil {
+		return nil, err
+	}
+	if len(layers) != 1 {
 		return nil, fmt.Errorf("multiple layers found in image %q", ref)
 	}
-	return artefacts[0], nil
+	return newArtifcatInfoFromLayerDescriptor(image, layers[0])
 }
 
-func (c *Client) GetArtefacts(ctx context.Context, ref string) ([]*ArtefactInfo, error) {
+func newArtifcatInfoFromLayerDescriptor(image v1.Image, layerDecriptor v1.Descriptor) (*ArtefactInfo, error) {
+	layer, err := image.LayerByDigest(layerDecriptor.Digest)
+	if err != nil {
+		return nil, fmt.Errorf("fetching artefact image failed: %w", err)
+	}
+	blob, err := layer.Uncompressed()
+	if err != nil {
+		return nil, fmt.Errorf("extracting uncompressed aretefact image failed: %w", err)
+	}
+	info := &ArtefactInfo{
+		ReadCloser:  blob,
+		MediaType:   layerDecriptor.MediaType,
+		Annotations: layerDecriptor.Annotations,
+	}
+	return info, nil
+}
+
+func (c *Client) getArtefactLayers(ctx context.Context, ref string) (v1.Image, []v1.Descriptor, error) {
 	image, err := c.Pull(ctx, ref)
 	if err != nil {
-		return nil, fmt.Errorf("failed to pull %q: %w", ref, err)
+		return nil, nil, fmt.Errorf("failed to pull %q: %w", ref, err)
 	}
 	manifest, err := image.Manifest()
 	if err != nil {
-		return nil, fmt.Errorf("failed to get manifest of %q: %w", ref, err)
+		return nil, nil, fmt.Errorf("failed to get manifest of %q: %w", ref, err)
 	}
 	if len(manifest.Layers) < 1 {
-		return nil, fmt.Errorf("no layers found in image %q", ref)
-	}
-	artefacts := []*ArtefactInfo{}
-	for _, layerDecriptor := range manifest.Layers {
-		layer, err := image.LayerByDigest(layerDecriptor.Digest)
-		if err != nil {
-			return nil, fmt.Errorf("fetching aretefact image failed: %w", err)
-		}
-
-		blob, err := layer.Uncompressed()
-		if err != nil {
-			return nil, fmt.Errorf("extracting uncompressed aretefact image failed: %w", err)
-		}
-
-		info := &ArtefactInfo{
-			ReadCloser:  blob,
-			MediaType:   layerDecriptor.MediaType,
-			Annotations: layerDecriptor.Annotations,
-		}
-		artefacts = append(artefacts, info)
+		return nil, nil, fmt.Errorf("no layers found in image %q", ref)
 	}
-	return artefacts, nil
+	return image, manifest.Layers, nil
 }
 
 // based on https://github.com/fluxcd/pkg/blob/2a323d771e17af02dee2ccbbb9b445b78ab048e5/oci/client/push.go

oci/oci.go

@@ -76,10 +76,6 @@ func (c *Client) Index(ctx context.Context, ref string) (*v1.IndexManifest, erro
 	return v1.ParseIndexManifest(bytes.NewReader(data))
 }
 
-func (c *Client) PullArtefact(ctx context.Context, ref, dir string) (*Metadata, error) {
-	return c.Client.Pull(ctx, ref, dir)
-}
-
 func (c *Client) Pull(ctx context.Context, ref string) (v1.Image, error) {
 	return crane.Pull(ref, c.withContext(ctx)...)
 }

tape/app/images.go

@@ -168,16 +168,12 @@ func (c *TapeImagesCommand) CollectInfo(ctx context.Context, images *types.Image
 			}
 
 			ref := image.OriginalName + "@" + digest
-			artefacts, err := client.GetArtefacts(ctx, ref)
+			artefacts, err := client.SelectArtefacts(ctx, ref, "application/vnd.in-toto+json")
 			if err != nil {
 				return fmt.Errorf("failed to fetch inline attestation: %w", err)
 			}
 
 			for _, artefact := range artefacts {
-				if artefact.MediaType != "application/vnd.in-toto+json" {
-					return fmt.Errorf("unexpected media type of attestation in %q: %s", ref, artefact.MediaType)
-				}
-
 				doc := document{
 					MediaType: string(artefact.MediaType),
 					Object:    &in_toto.Statement{},
@@ -225,7 +221,7 @@ func (c *TapeImagesCommand) CollectInfo(ctx context.Context, images *types.Image
 				ref := relatedImage.Ref(true)
 				switch {
 				case strings.HasSuffix(relatedImage.OriginalTag, ".att"):
-					artefact, err := client.GetArtefact(ctx, ref)
+					artefact, err := client.GetSingleArtefact(ctx, ref)
 					if err != nil {
 						return nil, fmt.Errorf("failed to fetch external attestation: %w", err)
 					}
@@ -245,7 +241,7 @@ func (c *TapeImagesCommand) CollectInfo(ctx context.Context, images *types.Image
 
 					info.ExternalAttestations[ref] = doc
 				case strings.HasSuffix(relatedImage.OriginalTag, ".sbom"):
-					artefact, err := client.GetArtefact(ctx, ref)
+					artefact, err := client.GetSingleArtefact(ctx, ref)
 					if err != nil {
 						return nil, fmt.Errorf("failed to fetch external attestation: %w", err)
 					}
@@ -272,7 +268,7 @@ func (c *TapeImagesCommand) CollectInfo(ctx context.Context, images *types.Image
 
 					info.ExternalSBOMs[ref] = doc
 				case strings.HasSuffix(relatedImage.OriginalTag, ".sig"):
-					artefact, err := client.GetArtefact(ctx, ref)
+					artefact, err := client.GetSingleArtefact(ctx, ref)
 					if err != nil {
 						return nil, fmt.Errorf("failed to fetch external signature: %w", err)
 					}