We're currently working on upgrading a small information system for an enterprise. Currently, the system has a corporate network zone (CORP) where services for internal users are placed, and a data center network segment (DC) where a data access service and all databases reside. All applications are essentially deployed in web servers and communication between them is done over HTTPS.
We need to install a new network zone, the DMZ, where a few externally-available services will be placed. During our meetings, we've come across an issue which might be of importance.
Data requests arriving from the internet arrive at DMZ Data Access service. DMZ Data Access forwards the request to CORP External Request Handler (which is essentially a proxy that authenticates the request is coming from DMZ Service 1) which then forwards the request to the DC Data Access service.
The problem comes when you add access control checks. Due to the way the previous system is set-up, users, roles, and permissions can be retrieved only through the DC Data Access service. This means that if we build interceptors which check user permissions in DMZ Data Access, the flow of data will include:
User -> DMZ Data Access (permission check) -> CORP External Request Handler -> DC Data Access (permission ok) -> CORP External Request Handler -> DMZ Data Access (permission granted, request data) -> CORP External Request Handler -> DC Data Access -> CORP External Request Handler -> DMZ Data Access -> User
We might be able to move the access control checks to the DC Data Access layer in order to simplify the flow a bit, but we're still not sure what impact on the performance this would have, nor any idea how susceptible this is to a DDoS attack.
However, we're not sure if this is the correct approach. Is there any standard way to deal with this issue, should we merge our access control and data access checks into a single request, or are we simply doing premature optimization?
One thing to note is that we can't rely on active directory or some other authorization provider, as we need to integrate into the existing infrastructure.