This is again a feature that very few people will even notice exist, but a lot of time, effort and thinking went into building. How should RavenDB handle a case when a user make a request that it is not authorize to make. In particular, we need to consider the case of a user pointing the browser to a server or database that they aren’t authorized to see or without having the x509 certificate properly registered.
To understand the problem we need to figure out what the default experience will be like, and if we require a client certificate to connect to RavenDB, and the client does not provide it, by default the response is some variation of just closing the TCP connection. That result in the client getting an error that looks like this:
TCP connection closed unexpectedly
That is not conductive for a good error experience and will typically cause a user to spend a lot of time trying to figure out what the network problem is, while everything is working just fine, the server just doesn’t want to talk to the user.
The problem is that at the TLS level, there isn’t really a good way to give back some meaningful error. We are too low level, all we can do is just terminate the connection.
Instead of doing that, RavenDB will accept the connection, regardless of whatever it has a valid certificate (or even any certificate) and pass the connection to one level up in the chain. At that point, we can check whatever the certificate is valid and if it isn’t (or if it doesn’t have the permissions to do what we want it to do we can use the protocol’s own mechanism to report errors.
With HTTP, that means we can return a 403 error to the user, including an explanation on why we rejected the connection (no certificate, expired certificate, certificate doesn’t have the right permissions, etc). This make things much easier when you need to troubleshoot permissions issues.