support HEAD for the rest of them

cmd/buildpack/main.go

@@ -118,12 +118,31 @@ func (s *server) serveBuildpackManifest(w http.ResponseWriter, r *http.Request)
 	}
 	ghOwner, ghRepo := parts[2], parts[3]
 	path := strings.Join(parts[4:len(parts)-2], "/")
-	revision := parts[len(parts)-1]
+	tagOrDigest := parts[len(parts)-1]
+
+	// If request is for image by digest, try to serve it from GCS.
+	if strings.HasPrefix(tagOrDigest, "sha256:") {
+		desc, err := s.storage.BlobExists(ctx, tagOrDigest)
+		if err != nil {
+			s.error.Printf("ERROR (storage.BlobExists): %s", err)
+			serve.Error(w, serve.ErrNotFound)
+			return
+		}
+		if r.Method == http.MethodHead {
+			w.Header().Set("Docker-Content-Digest", tagOrDigest)
+			w.Header().Set("Content-Type", string(desc.MediaType))
+			w.Header().Set("Content-Length", fmt.Sprintf("%d", desc.Size))
+			return
+		}
+		serve.Blob(w, r, tagOrDigest)
+		return
+	}
 
 	// If the image tag looks like a commit SHA, see if we already have a
 	// manifest cached for that revision and serve it directly.  Otherwise,
 	// resolve the branch/tag/whatever to a SHA and redirect to that SHA
 	// image tag.
+	revision := tagOrDigest
 	if commitRE.MatchString(revision) {
 		ck := cacheKey(path, revision)
 		if _, err := s.storage.BlobExists(ctx, ck); err == nil {

cmd/kaniko/main.go

@@ -111,12 +111,31 @@ func (s *server) serveKanikoManifest(w http.ResponseWriter, r *http.Request) {
 	}
 	ghOwner, ghRepo := parts[2], parts[3]
 	path := strings.Join(parts[4:len(parts)-2], "/")
-	revision := parts[len(parts)-1]
+	tagOrDigest := parts[len(parts)-1]
+
+	// If request is for image by digest, try to serve it from GCS.
+	if strings.HasPrefix(tagOrDigest, "sha256:") {
+		desc, err := s.storage.BlobExists(ctx, tagOrDigest)
+		if err != nil {
+			s.error.Printf("ERROR (storage.BlobExists): %s", err)
+			serve.Error(w, serve.ErrNotFound)
+			return
+		}
+		if r.Method == http.MethodHead {
+			w.Header().Set("Docker-Content-Digest", tagOrDigest)
+			w.Header().Set("Content-Type", string(desc.MediaType))
+			w.Header().Set("Content-Length", fmt.Sprintf("%d", desc.Size))
+			return
+		}
+		serve.Blob(w, r, tagOrDigest)
+		return
+	}
 
 	// If the image tag looks like a commit SHA, see if we already have a
 	// manifest cached for that revision and serve it directly.  Otherwise,
 	// resolve the branch/tag/whatever to a SHA and redirect to that SHA
 	// image tag.
+	revision := tagOrDigest
 	if commitRE.MatchString(revision) {
 		ck := cacheKey(path, revision)
 		if _, err := s.storage.BlobExists(ctx, ck); err == nil {

cmd/ko/main.go

@@ -82,8 +82,25 @@ func (s *server) serveKoManifest(w http.ResponseWriter, r *http.Request) {
 	ip := strings.Join(parts[:len(parts)-2], "/")
 
 	// "go get" the package
-	tag := parts[len(parts)-1]
-	s.info.Printf("requested image tag :%s", tag)
+	tagOrDigest := parts[len(parts)-1]
+
+	// If request is for image by digest, try to serve it from GCS.
+	if strings.HasPrefix(tagOrDigest, "sha256:") {
+		desc, err := s.storage.BlobExists(ctx, tagOrDigest)
+		if err != nil {
+			s.error.Printf("ERROR (storage.BlobExists): %s", err)
+			serve.Error(w, serve.ErrNotFound)
+			return
+		}
+		if r.Method == http.MethodHead {
+			w.Header().Set("Docker-Content-Digest", tagOrDigest)
+			w.Header().Set("Content-Type", string(desc.MediaType))
+			w.Header().Set("Content-Length", fmt.Sprintf("%d", desc.Size))
+			return
+		}
+		serve.Blob(w, r, tagOrDigest)
+		return
+	}
 
 	// go get the package.
 	// TODO: Check image tag for version, resolve branches -> commits and redirect to img:<commit>

cmd/random/main.go

@@ -71,11 +71,30 @@ var randomTagRE = regexp.MustCompile("([0-9]{1,2})x([0-9]{1,8})")
 // random.kontain.me:3x10mb
 // random.kontain.me(:latest) -> 1x10mb
 func (s *server) serveRandomManifest(w http.ResponseWriter, r *http.Request) {
-	tag := strings.TrimPrefix(r.URL.Path, "/v2/manifests/")
+	ctx := r.Context()
+	tagOrDigest := strings.TrimPrefix(r.URL.Path, "/v2/manifests/")
 	var num, size int64 = 1, 10000000 // 10MB
 
+	// If request is for image by digest, try to serve it from GCS.
+	if strings.HasPrefix(tagOrDigest, "sha256:") {
+		desc, err := s.storage.BlobExists(ctx, tagOrDigest)
+		if err != nil {
+			s.error.Printf("ERROR (storage.BlobExists): %s", err)
+			serve.Error(w, serve.ErrNotFound)
+			return
+		}
+		if r.Method == http.MethodHead {
+			w.Header().Set("Docker-Content-Digest", tagOrDigest)
+			w.Header().Set("Content-Type", string(desc.MediaType))
+			w.Header().Set("Content-Length", fmt.Sprintf("%d", desc.Size))
+			return
+		}
+		serve.Blob(w, r, tagOrDigest)
+		return
+	}
+
 	// Captured requested num + size from tag.
-	all := randomTagRE.FindStringSubmatch(tag)
+	all := randomTagRE.FindStringSubmatch(tagOrDigest)
 	if len(all) >= 3 {
 		num, _ = strconv.ParseInt(all[1], 10, 64)
 		size, _ = strconv.ParseInt(all[2], 10, 64)

cmd/wait/main.go

@@ -84,6 +84,25 @@ func (s *server) serveWaitManifest(w http.ResponseWriter, r *http.Request) {
 	parts := strings.Split(path, "/")
 	name := strings.Join(parts[:len(parts)-2], "/")
 
+	// If request is for image by digest, try to serve it from GCS.
+	tagOrDigest := parts[len(parts)-1]
+	if strings.HasPrefix(tagOrDigest, "sha256:") {
+		desc, err := s.storage.BlobExists(ctx, tagOrDigest)
+		if err != nil {
+			s.error.Printf("ERROR (storage.BlobExists): %s", err)
+			serve.Error(w, serve.ErrNotFound)
+			return
+		}
+		if r.Method == http.MethodHead {
+			w.Header().Set("Docker-Content-Digest", tagOrDigest)
+			w.Header().Set("Content-Type", string(desc.MediaType))
+			w.Header().Set("Content-Length", fmt.Sprintf("%d", desc.Size))
+			return
+		}
+		serve.Blob(w, r, tagOrDigest)
+		return
+	}
+
 	// The image has already been built; serve it.
 	ck := cacheKey(name)
 	if _, err := s.storage.BlobExists(ctx, ck); err == nil {
@@ -102,7 +121,7 @@ func (s *server) serveWaitManifest(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// No cached image or placeholder exists; enqueue a new task.
-	tag := strings.TrimPrefix(r.URL.Path, fmt.Sprintf("/v2/%s/manifests/", name))
+	tag := tagOrDigest
 	if tag == "latest" {
 		tag = "10s"
 	}

pkg/serve/serve.go

@@ -151,6 +151,18 @@ func (s *Storage) ServeIndex(w http.ResponseWriter, r *http.Request, idx v1.Imag
 		return err
 	}
 
+	// If it's just a HEAD request, serve that.
+	if r.Method == http.MethodHead {
+		s, err := idx.Size()
+		if err != nil {
+			return err
+		}
+		w.Header().Set("Docker-Content-Digest", digest.String())
+		w.Header().Set("Content-Type", string(mt))
+		w.Header().Set("Content-Length", fmt.Sprintf("%d", s))
+		return nil
+	}
+
 	// Redirect to manifest blob.
 	Blob(w, r, digest.String())
 	return nil
@@ -238,6 +250,22 @@ func (s *Storage) ServeManifest(w http.ResponseWriter, r *http.Request, img v1.I
 		return err
 	}
 
+	// If it's just a HEAD request, serve that.
+	if r.Method == http.MethodHead {
+		mt, err := img.MediaType()
+		if err != nil {
+			return err
+		}
+		s, err := img.Size()
+		if err != nil {
+			return err
+		}
+		w.Header().Set("Docker-Content-Digest", digest.String())
+		w.Header().Set("Content-Type", string(mt))
+		w.Header().Set("Content-Length", fmt.Sprintf("%d", s))
+		return nil
+	}
+
 	// Redirect to manifest blob.
 	Blob(w, r, digest.String())
 	return nil