Update docker resolver to authorize redirects

Allows redirects to be authorized if authorization is provided
for the redirected to host. The authorization will always go
to the redirect and never to the referrer.

Signed-off-by: Derek McGowan <derek@mcg.dev>

remotes/docker/resolver.go

@@ -539,7 +539,21 @@ func (r *request) do(ctx context.Context) (*http.Response, error) {
 	if err := r.authorize(ctx, req); err != nil {
 		return nil, errors.Wrap(err, "failed to authorize")
 	}
-	resp, err := ctxhttp.Do(ctx, r.host.Client, req)
+
+	var client = &http.Client{}
+	if r.host.Client != nil {
+		*client = *r.host.Client
+	}
+	if client.CheckRedirect == nil {
+		client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+			if len(via) >= 10 {
+				return errors.New("stopped after 10 redirects")
+			}
+			return errors.Wrap(r.authorize(ctx, req), "failed to authorize redirect")
+		}
+	}
+
+	resp, err := ctxhttp.Do(ctx, client, req)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to do request")
 	}