Allow to expose a subset of unsafe RPCs (#5233)

* sc-cli: Use type-safe constructors for RPC/Prometheus interfaces

* service: Simplify rpc handler creation

Could probably be further simplifies once [this][commit] lands.

[commit]: https://github.com/paritytech/jsonrpc/commit/20485387ed06a48f1a70bf4d609a7cde6cf0accf

* service: Streamline some HTTP & WS server start logic

* client: Introduce a simple RPC policy mechanism

* rpc/system: Check unsafe RPCs

* rpc/offchain: Check unsafe RPCs

* rpc/author: Check unsafe RPCs

substrate/client/rpc/src/offchain/mod.rs

@@ -21,6 +21,7 @@ mod tests;
 
 /// Re-export the API for backward compatibility.
 pub use sc_rpc_api::offchain::*;
+use sc_rpc_api::DenyUnsafe;
 use self::error::{Error, Result};
 use sp_core::{
 	Bytes,
@@ -34,13 +35,15 @@ use std::sync::Arc;
 pub struct Offchain<T: OffchainStorage> {
 	/// Offchain storage
 	storage: Arc<RwLock<T>>,
+	deny_unsafe: DenyUnsafe,
 }
 
 impl<T: OffchainStorage> Offchain<T> {
 	/// Create new instance of Offchain API.
-	pub fn new(storage: T) -> Self {
+	pub fn new(storage: T, deny_unsafe: DenyUnsafe) -> Self {
 		Offchain {
 			storage: Arc::new(RwLock::new(storage)),
+			deny_unsafe,
 		}
 	}
 }
@@ -48,6 +51,8 @@ impl<T: OffchainStorage> Offchain<T> {
 impl<T: OffchainStorage + 'static> OffchainApi for Offchain<T> {
 	/// Set offchain local storage under given key and prefix.
 	fn set_local_storage(&self, kind: StorageKind, key: Bytes, value: Bytes) -> Result<()> {
+		self.deny_unsafe.check_if_safe()?;
+
 		let prefix = match kind {
 			StorageKind::PERSISTENT => sp_offchain::STORAGE_PREFIX,
 			StorageKind::LOCAL => return Err(Error::UnavailableStorageKind),
@@ -58,6 +63,8 @@ impl<T: OffchainStorage + 'static> OffchainApi for Offchain<T> {
 
 	/// Get offchain local storage under given key and prefix.
 	fn get_local_storage(&self, kind: StorageKind, key: Bytes) -> Result<Option<Bytes>> {
+		self.deny_unsafe.check_if_safe()?;
+
 		let prefix = match kind {
 			StorageKind::PERSISTENT => sp_offchain::STORAGE_PREFIX,
 			StorageKind::LOCAL => return Err(Error::UnavailableStorageKind),

substrate/client/rpc/src/offchain/tests.rs

@@ -21,7 +21,7 @@ use sp_core::{Bytes, offchain::storage::InMemOffchainStorage};
 #[test]
 fn local_storage_should_work() {
 	let storage = InMemOffchainStorage::default();
-	let offchain = Offchain::new(storage);
+	let offchain = Offchain::new(storage, DenyUnsafe::No);
 	let key = Bytes(b"offchain_storage".to_vec());
 	let value = Bytes(b"offchain_value".to_vec());
 
@@ -34,3 +34,20 @@ fn local_storage_should_work() {
 		Ok(Some(ref v)) if *v == value
 	);
 }
+
+#[test]
+fn offchain_calls_considered_unsafe() {
+	let storage = InMemOffchainStorage::default();
+	let offchain = Offchain::new(storage, DenyUnsafe::Yes);
+	let key = Bytes(b"offchain_storage".to_vec());
+	let value = Bytes(b"offchain_value".to_vec());
+
+	assert_matches!(
+		offchain.set_local_storage(StorageKind::PERSISTENT, key.clone(), value.clone()),
+		Err(Error::UnsafeRpcCalled(_))
+	);
+	assert_matches!(
+		offchain.get_local_storage(StorageKind::PERSISTENT, key),
+		Err(Error::UnsafeRpcCalled(_))
+	);
+}