I have a single URL accessible through a servlet that I have locked down using Spring Security's DaoAuthenticationProvider. I now have the requirement that certain incoming IP addresses must be whitelisted and so are not requested to authenticate.
I can hack around this easily enough by overriding DaoAuthenticationProvider's authenticate method and bypassing the superclasses's implementation if the IP address matches a known IP address but this then only works when the sender of the request supplies a username and password (even if it's nonsense). Otherwise the provider doesn't get called.
What would be the best way to do this? Should I be using a filter to bypass the authentication procedure if a known IP address is incoming?
I think the idiomatic Spring Security way to do it is to implement a pre-authentication filter that would populate security context with a valid Authentication object when client is in the whitelist. You can implement such a filter from scratch (for example, as here) or use AbstractPreAuthenticatedProcessingFilter (though it seems to be overcomplicated for your task).