From 11e936d10902511ddbb8745c4ce19e249d91f407 Mon Sep 17 00:00:00 2001
From: stasatdaglabs <39559713+stasatdaglabs@users.noreply.github.com>
Date: Sun, 8 Dec 2019 14:05:56 +0200
Subject: [PATCH] [NOD-493] Make GetBlock return an appropriate error if the
 hash is known to be of an invalid block. (#520)

---
 blockdag/dag.go                | 12 ++++++++++++
 btcjson/jsonrpcerr.go          |  1 +
 server/rpc/handle_get_block.go |  8 ++++++++
 3 files changed, 21 insertions(+)

diff --git a/blockdag/dag.go b/blockdag/dag.go
index 9c7753cfc..a6606ad6e 100644
--- a/blockdag/dag.go
+++ b/blockdag/dag.go
@@ -192,6 +192,18 @@ func (dag *BlockDAG) IsKnownOrphan(hash *daghash.Hash) bool {
 	return exists
 }
 
+// IsKnownInvalid returns whether the passed hash is known to be an invalid block.
+// Note that if the block is not found this method will return false.
+//
+// This function is safe for concurrent access.
+func (dag *BlockDAG) IsKnownInvalid(hash *daghash.Hash) bool {
+	node := dag.index.LookupNode(hash)
+	if node == nil {
+		return false
+	}
+	return dag.index.NodeStatus(node).KnownInvalid()
+}
+
 // GetOrphanMissingAncestorHashes returns all of the missing parents in the orphan's sub-DAG
 //
 // This function is safe for concurrent access.
diff --git a/btcjson/jsonrpcerr.go b/btcjson/jsonrpcerr.go
index 6e83c4b1a..862b01335 100644
--- a/btcjson/jsonrpcerr.go
+++ b/btcjson/jsonrpcerr.go
@@ -66,6 +66,7 @@ const (
 	ErrRPCRawTxString        RPCErrorCode = -32602
 	ErrRPCDecodeHexString    RPCErrorCode = -22
 	ErrRPCOrphanBlock        RPCErrorCode = -6
+	ErrRPCBlockInvalid       RPCErrorCode = -5
 )
 
 // Errors that are specific to btcd.
diff --git a/server/rpc/handle_get_block.go b/server/rpc/handle_get_block.go
index ae6644735..96eb55382 100644
--- a/server/rpc/handle_get_block.go
+++ b/server/rpc/handle_get_block.go
@@ -23,6 +23,14 @@ func handleGetBlock(s *Server, cmd interface{}, closeChan <-chan struct{}) (inte
 		return nil, rpcDecodeHexError(c.Hash)
 	}
 
+	// Return an appropriate error if the block is known to be invalid
+	if s.cfg.DAG.IsKnownInvalid(hash) {
+		return nil, &btcjson.RPCError{
+			Code:    btcjson.ErrRPCBlockInvalid,
+			Message: "Block is known to be invalid",
+		}
+	}
+
 	// Return an appropriate error if the block is an orphan
 	if s.cfg.DAG.IsKnownOrphan(hash) {
 		return nil, &btcjson.RPCError{