We are not aware of any digital signage platforms that natively support webpage authentication. However, we do have customers doing this today and they usually use one of 4 approaches:

1. Have the website/service accept username/password passed through via the URL. It's a security concern for some but that depends on your content. 
2. Use a token authentication approach when a token is passed through
3. Whitelist the IP so authentication is not required from that IP address the player is on
4. Use a XOGO Windows player and join the domain and authenticate the device via domain services

Please let us know if you need more information and we'll be happy to discuss.