In Spring Framework 5.0.2 ServerHttpRequest#getSslInfo() was added in order to expose a connection's TLS information to handlers. Currently, the ServerHttpRequest.Builder does not have a method allowing mutators of the request to mutate the TLS information. This prevents a WebFilter from intercepting the request and modifying this information.
The ServerHttpRequest.Builder should gain the functionality to mutate the TLS information for a request, preferably in an additive way, e.g. adding to rather than replacing the peer certificates.