Using Django as a centralised auth server?

[Stodge]

I have several Django websites and I want to create a centralized auth provider. The auth provider site would contain the user accounts and be the only repository for user details and passwords. Users would log into the auth provider site and when they visit each satellite website for the first time, an account is created on that site. Subsequent visits to the satellite site would result in them being sent to the auth provider site to login first. On returning they are automatically logged in to the satellite site. My only difficulty is that the auth provider site would be on the internet and the satellite sites are in DMZs on private networks with access to the internet. So the satellite sites cannot establish any outgoing connections to the auth provider.

Is oauth2 the right solution? I just found the cas-provider so I'll read up on that. Are there any better or more appropriate alternatives?

Thanks