Authenticate with Docker registry API - api

Question

I am trying to auth with the Docker registry API at https://registry-1.docker.io/v1/
I am trying to do calls like
https://registry-1.docker.io/v1/repositories/_/ubuntu/tags
However I keep getting a reply as below:
401
{ server: 'gunicorn/18.0',
date: 'Sun, 01 Mar 2015 12:19:13 GMT',
connection: 'close',
expires: '-1',
'content-type': 'application/json',
'www-authenticate': 'Token',
pragma: 'no-cache',
'cache-control': 'no-cache',
'content-length': '35',
'x-docker-registry-version': '0.8.2',
'x-docker-registry-config': 'prod',
'strict-transport-security': 'max-age=31536000' }
{"error": "Requires authorization"}
I have read all available guidelines as in the docs and forums.
Following those guidelines I first auth towards the HUB and request a Token. This suceeds and I get the token and a cookie from the HUB. Then I supply all this towards the Registry API as follows:
{
'set-cookie': 'csrftoken=VfHe6...; Expires=Sun, 28 Feb 2016 12:19:13 GMT; Max-Age=31449600; Path=/; Secure',
'www-authenticate': 'Token signature=VfHe6...,repository="ubuntu",access=read',
'x-docker-token': 'Token signature=VfHe6...,repository="ubuntu",access=read',
Authenticate: 'Token signature=VfHe6...,repository="ubuntu",access=read',
Authorization: 'Token signature=VfHe6...,repository="ubuntu",access=read'
}

Answer 1

There is this single line in the docs you shared:
Token is only returned when the X-Docker-Token header is sent with request.
You need to send 'X-Docker-Token: true' when you authenticate on the hub, then you receive in the header a 'X-Docker-Token' back. Send this out as 'Authorization:' to the registry in 'X-Docker-Endpoints' and you're in.
Good luck! :)