Secure Rest-Service before user authentification

Question

I have a web application that provides several rest services (Jersey). Most of the endpoints are secured by BASIC authentification. Further more I use SSL for transport and demand POSTs for every call. The clients/consumers are android apps.

So far so good. The only service that seems to be vulnerable is the registration. It's the 'first' service to call and a user does not exist yet. So I cannot use OAuth, etc. I also have to keep the endpoint easy accessible to enable the user to regster.

How do I secure this service, so it's not spammed by a bot flooding my database?

Answer 1

How about these?

1. Use a registration link with a token in the request parameter. Ensure that the tokens expire after sometime. You could create a token endpoint url as well for a client to get a valid token.
2. Use a custom header or a dynamic custom header in your request. Additionally, you could check for a dynamic custom header to validate the request's authenticity.
3. Use registration confirmation workflows, such as an email / text verification as soon the registration is done. Run a process every day to delete any user accounts, which are not validated in say x days.

I do not think you can really secure the registration URL in a HTTP way. IMHO, anyone who has the registration url can be a right guy trying to register. So if you ask me, option 3 is better than others.