docker_auth - Authentication server for Docker Registry 2
The original Docker Registry server (v1) did not provide any support for authentication or authorization. Access control had to be performed externally, typically by deploying Nginx in the reverse proxy mode with Basic or other type of authentication. While performing simple user authentication is pretty straightforward, performing more fine-grained access control was cumbersome. Docker Registry 2.0 introduced a new, token-based authentication and authorization protocol, but the server to generate them was not released. Thus, most guides found on the internet still describe a set up with a reverse proxy performing access control.