From 4f15ea102d15eb237b63464725508dc509e98819 Mon Sep 17 00:00:00 2001
From: Gregory Maxwell <greg@xiph.org>
Date: Sun, 2 Apr 2017 21:39:32 +0000
Subject: [PATCH] Check transaction count early in submitblock.

There is no point in even hashing a submitted block which doesn't have
 a coinbase transaction.

This also results in more useful error reporting on corrupted input.

Thanks to rawodb for the bug report.
---
 src/rpc/mining.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index b823c159d..cfa6edae1 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -744,6 +744,10 @@ UniValue submitblock(const JSONRPCRequest& request)
     if (!DecodeHexBlk(block, request.params[0].get_str()))
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
 
+    if (block.vtx.empty() || !block.vtx[0]->IsCoinBase()) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block does not start with a coinbase");
+    }
+
     uint256 hash = block.GetHash();
     bool fBlockPresent = false;
     {