From ce4cf85ba85e15f69130106e37321ee94da702d8 Mon Sep 17 00:00:00 2001
From: Ricardo Branco <rbranco@suse.de>
Date: Thu, 3 Nov 2022 20:47:07 +0100
Subject: [PATCH 1/2] Calculate digest if missing

---
 registry/digest.go | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/registry/digest.go b/registry/digest.go
index 361ae4748..7a635ddb4 100644
--- a/registry/digest.go
+++ b/registry/digest.go
@@ -2,6 +2,7 @@ package registry
 
 import (
 	"context"
+	_ "crypto/sha256"
 	"fmt"
 	"net/http"
 
@@ -36,5 +37,16 @@ func (r *Registry) Digest(ctx context.Context, image Image) (digest.Digest, erro
 		return "", fmt.Errorf("got status code: %d", resp.StatusCode)
 	}
 
-	return digest.Parse(resp.Header.Get("Docker-Content-Digest"))
+	d := resp.Header.Get("Docker-Content-Digest")
+	if d == "" {
+		// Get the v2 manifest.
+		m, err := r.Manifest(ctx, image.Path, image.Reference())
+		if err != nil {
+			return "", err
+		}
+		_, p, _ := m.Payload()
+		return digest.FromBytes(p), nil
+	}
+
+	return digest.Parse(d)
 }

From c30f09c61c753605d4285a9fb42909b980db0d99 Mon Sep 17 00:00:00 2001
From: Ricardo Branco <rbranco@suse.de>
Date: Wed, 9 Nov 2022 21:11:43 +0100
Subject: [PATCH 2/2] Some registries return a digest only with the HEAD method

---
 registry/digest.go | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/registry/digest.go b/registry/digest.go
index 7a635ddb4..b9f5da4a1 100644
--- a/registry/digest.go
+++ b/registry/digest.go
@@ -10,6 +10,8 @@ import (
 	digest "github.com/opencontainers/go-digest"
 )
 
+var useHead bool = true
+
 // Digest returns the digest for an image.
 func (r *Registry) Digest(ctx context.Context, image Image) (digest.Digest, error) {
 	if len(image.Digest) > 1 {
@@ -38,6 +40,28 @@ func (r *Registry) Digest(ctx context.Context, image Image) (digest.Digest, erro
 	}
 
 	d := resp.Header.Get("Docker-Content-Digest")
+	if d == "" {
+		req, err := http.NewRequest("HEAD", url, nil)
+		if err != nil {
+			return "", err
+		}
+
+		req.Header.Add("Accept", schema2.MediaTypeManifest)
+		resp, err := r.Client.Do(req.WithContext(ctx))
+		if err != nil {
+			return "", err
+		}
+		defer resp.Body.Close()
+
+		if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusNotFound {
+			return "", fmt.Errorf("got status code: %d", resp.StatusCode)
+		}
+
+		d = resp.Header.Get("Docker-Content-Digest")
+		if d == "" {
+			useHead = false
+		}
+	}
 	if d == "" {
 		// Get the v2 manifest.
 		m, err := r.Manifest(ctx, image.Path, image.Reference())