RPC call returns ForbiddenHostCall

[skunert]

When performing an RPC call with method state_call, I get a "ForbiddenHostCall" error message for certain calls. I am not sure what that means or why the call is forbidden. Until now I have only observed this for state_call with method ParachainHost_availability_cores.

Error Message

ErrorObject { code: ServerError(-32000), message: "ForbiddenHostCall", data: None }

Reproduction

• Start network (chain spec was rococo-local in my case)
• Join network with smoldot light-client
• Send payload via websocket: {"id": "some_id", "method": "state_call", "params": ["ParachainHost_availability_cores", "0x"], "jsonrpc": "2.0"}
• I verified that this call works fine on the other relay chain nodes in the network

[tomaka]

This is semi-intended.

This ForbiddenHostCall means that the runtime has tried to modify the storage.

Since I was generally expecting the runtime calls made by the JSON-RPC layer to not modify the storage, I had decided at the time to forbid modifications to the storage.

I'll change that.