The auth endpoint for Docker returns the wrong JSON configuration when using the API key. This results in not being able to properly authenticate v1 repositories.
NOTE: IT IS possible to use the API key for docker authentication for V1. Use the workaround described below.
1. Create a Docker v1 repository (and the reverse proxy to access it)
2. Create an API key for a user
3. Use the username/API key on the URL /v1/auth (use the reverse proxy's address)
4. Copy the JSON into ~/.docker/config.json
5. Try to push an image and observe the failure to authenticate.
You can create the correct auth key using this formula:
username:api-key -> Base64Encode
A site like https://www.base64encode.org/ will produce the correct output.