http over https port on private registry

[ThePhilderbeast]

when check if running on a private registry it is failing to fetch the digest due to sending a plain http request on a https port even with 443 specified as the port

[xtremerui]

Could you provide simple steps to reproducte it?

From the code here it will try the ping with both http and https https://github.com/concourse/docker-image-resource/blob/770ff365918ed0d2d0f838b2e4b2bed40cc86d80/cmd/check/main.go#L208

if any attemp works the registry URL will be set to the working schema that the private registry accepts i.e. the private registry might redirect http to https. So running a check with http while specifying 443 port is not neccessary wrong.