Data plane verification (#4639)

* Add signature to blob

* Change Signable trait to support returning references to signable data

* Add signing to broadcast

* Verify signatures in window_service

* Add testing for signatures to erasure

* Add RPC for getting current slot, consume RPC call in test_repairman_catchup for more deterministic results

core/src/rpc.rs

@@ -96,6 +96,10 @@ impl JsonRpcRequestProcessor {
         self.bank().get_signature_confirmation_status(&signature)
     }
 
+    fn get_slot(&self) -> Result<u64> {
+        Ok(self.bank().slot())
+    }
+
     fn get_transaction_count(&self) -> Result<u64> {
         Ok(self.bank().transaction_count() as u64)
     }
@@ -218,6 +222,9 @@ pub trait RpcSol {
         _: String,
     ) -> Result<Option<transaction::Result<()>>>;
 
+    #[rpc(meta, name = "getSlot")]
+    fn get_slot(&self, _: Self::Metadata) -> Result<u64>;
+
     #[rpc(meta, name = "getTransactionCount")]
     fn get_transaction_count(&self, _: Self::Metadata) -> Result<u64>;
 
@@ -334,6 +341,10 @@ impl RpcSol for RpcSolImpl {
             .map(|res| res.map(|x| x.1))
     }
 
+    fn get_slot(&self, meta: Self::Metadata) -> Result<u64> {
+        meta.request_processor.read().unwrap().get_slot()
+    }
+
     fn get_num_blocks_since_signature_confirmation(
         &self,
         meta: Self::Metadata,