Proposal to add an ability to restrict some JSON RPC API methods

[varasev]

In some cases we may need to close some API methods leaving others available. For example, for enabled eth namespace we could restrict eth_sendTransaction.

I'd propose to add

--jsonrpc-restricted-methods

CLI option (and a similar --ws-restricted-methods for WebSocket connections).

The method names are comma-separated, e.g.:

--jsonrpc-restricted-methods="eth_sendTransaction,eth_accounts"

Such an option would close access for the listed methods for all network interfaces and ports. I think we don't need to delimit them by ip/port.

If --ws-restricted-methods is not defined, its value would be implicitly taken from --jsonrpc-restricted-methods for the case when a user forgot to restrict the same methods for WebSockets (and vice versa).

[varasev]

UPD: probably, it's better to make an opposite behaviour like it's implemented in Nethermind in CallsFilterFilePath option which whitelists approved JSON RPC methods.