Support OCI

pkg/image/manifest.go

@@ -3,11 +3,23 @@ package image
 import "fmt"
 
 var (
-	// ManifestListMimeType is the mime type used to get the manifest list
+	// ManifestListMimeType is the mime type used to get the manifest list (Docker)
 	ManifestListMimeType = "application/vnd.docker.distribution.manifest.list.v2+json"
 
-	// ManifestMimeType is the mime type used to get the manifest
+	// ManifestMimeType is the mime type used to get the manifest (Docker)
 	ManifestMimeType = "application/vnd.docker.distribution.manifest.v2+json"
+
+	// OCIIndexMimeType is the mime type for OCI image indexes (multi-arch)
+	OCIIndexMimeType = "application/vnd.oci.image.index.v1+json"
+
+	// OCIManifestMimeType is the mime type for OCI image manifests
+	OCIManifestMimeType = "application/vnd.oci.image.manifest.v1+json"
+
+	// AcceptManifestList is the Accept header value for manifest list requests
+	AcceptManifestList = ManifestListMimeType + ", " + OCIIndexMimeType
+
+	// AcceptManifest is the Accept header value for manifest requests
+	AcceptManifest = ManifestMimeType + ", " + OCIManifestMimeType
 )
 
 // ManifestList represents the Docker Manifest List:

pkg/image/remote.go

@@ -86,7 +86,7 @@ func (r *Remote) WithPlatform(p *Platform) {
 func (r *Remote) ManifestList() (*ManifestList, error) {
 
 	// not having a manifest list is no error
-	res, err := r.request("GET", ManifestListMimeType, "manifests", r.url.Reference())
+	res, err := r.request("GET", AcceptManifestList, "manifests", r.url.Reference())
 	if err != nil {
 		return nil, nil
 	}
@@ -111,14 +111,15 @@ func (r *Remote) Manifest() (*Manifest, error) {
 	}
 
 	// it should almost certainly be fetchable at this point
-	res, err := r.request("GET", ManifestMimeType, "manifests", digest)
+	res, err := r.request("GET", AcceptManifest, "manifests", digest)
 	if err != nil {
 		return nil, fmt.Errorf("error requesting manifest@%s: %v", digest, err)
 	}
 
-	// if the server responds with a manifest list, our digest is not correct
-	if res.Header.Get("Content-Type") != ManifestMimeType {
-		return nil, fmt.Errorf("content type for %s cannot be %s", digest, res.Header.Get("Content-Type"))
+	// if the server responds with a manifest list/index, our digest is not correct
+	ct := res.Header.Get("Content-Type")
+	if ct != ManifestMimeType && ct != OCIManifestMimeType {
+		return nil, fmt.Errorf("content type for %s cannot be %s", digest, ct)
 	}
 
 	// we must also be able to parse it
@@ -152,7 +153,7 @@ func (r *Remote) Digest() (string, error) {
 	// if there's no list and no platform, fall back to whatever the server
 	// gives us through the docker-content-digest header
 	if r.platform == nil && (lst == nil || len(lst.Manifests) == 0) {
-		res, err := r.request("HEAD", ManifestMimeType, "manifests", r.url.Reference())
+		res, err := r.request("HEAD", AcceptManifest, "manifests", r.url.Reference())
 
 		if err != nil {
 			return "", fmt.Errorf("failed to fetch manifest: %v", err)

pkg/image/utils.go

@@ -26,7 +26,7 @@ func requireSupportedMimeTypes(client *http.Client, url URL) error {
 	ref := url.Endpoint("manifests", url.Reference())
 
 	req := mustNewRequest("HEAD", ref)
-	req.Header.Add("Accept", fmt.Sprintf("%s, */*", ManifestMimeType))
+	req.Header.Add("Accept", AcceptManifest+", "+AcceptManifestList+", */*")
 
 	res, err := client.Do(req)
 	if err != nil {
@@ -37,9 +37,17 @@ func requireSupportedMimeTypes(client *http.Client, url URL) error {
 	}
 
 	mime := res.Header.Get("Content-Type")
-	if mime != ManifestMimeType && mime != ManifestListMimeType {
-		return fmt.Errorf("no schema version 2 support by %s", url)
+	if !isSupportedMimeType(mime) {
+		return fmt.Errorf("unsupported manifest type %s from %s", mime, url)
 	}
 
 	return nil
 }
+
+func isSupportedMimeType(mime string) bool {
+	switch mime {
+	case ManifestMimeType, ManifestListMimeType, OCIManifestMimeType, OCIIndexMimeType:
+		return true
+	}
+	return false
+}