From 5883afb3ef1e121e8625c2e1f4e929f333a65dd5 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Fri, 28 Aug 2020 16:27:58 +0200
Subject: [PATCH] rpc: fix issue with null JSON-RPC messages (#21497)

---
 rpc/json.go                    | 13 ++++++++++---
 rpc/testdata/invalid-batch.js  |  3 +++
 rpc/testdata/invalid-nonobj.js |  3 +++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/rpc/json.go b/rpc/json.go
index 3be5d55f48..1daee3db82 100644
--- a/rpc/json.go
+++ b/rpc/json.go
@@ -202,15 +202,22 @@ func (c *jsonCodec) remoteAddr() string {
 	return c.remote
 }
 
-func (c *jsonCodec) readBatch() (msg []*jsonrpcMessage, batch bool, err error) {
+func (c *jsonCodec) readBatch() (messages []*jsonrpcMessage, batch bool, err error) {
 	// Decode the next JSON object in the input stream.
 	// This verifies basic syntax, etc.
 	var rawmsg json.RawMessage
 	if err := c.decode(&rawmsg); err != nil {
 		return nil, false, err
 	}
-	msg, batch = parseMessage(rawmsg)
-	return msg, batch, nil
+	messages, batch = parseMessage(rawmsg)
+	for i, msg := range messages {
+		if msg == nil {
+			// Message is JSON 'null'. Replace with zero value so it
+			// will be treated like any other invalid message.
+			messages[i] = new(jsonrpcMessage)
+		}
+	}
+	return messages, batch, nil
 }
 
 func (c *jsonCodec) writeJSON(ctx context.Context, v interface{}) error {
diff --git a/rpc/testdata/invalid-batch.js b/rpc/testdata/invalid-batch.js
index f470574fb5..768dbc837e 100644
--- a/rpc/testdata/invalid-batch.js
+++ b/rpc/testdata/invalid-batch.js
@@ -10,5 +10,8 @@
 --> [1,2,3]
 <-- [{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}},{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}},{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}}]
 
+--> [null]
+<-- [{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}}]
+
 --> [{"jsonrpc":"2.0","id":1,"method":"test_echo","params":["foo",1]},55,{"jsonrpc":"2.0","id":2,"method":"unknown_method"},{"foo":"bar"}]
 <-- [{"jsonrpc":"2.0","id":1,"result":{"String":"foo","Int":1,"Args":null}},{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}},{"jsonrpc":"2.0","id":2,"error":{"code":-32601,"message":"the method unknown_method does not exist/is not available"}},{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}}]
diff --git a/rpc/testdata/invalid-nonobj.js b/rpc/testdata/invalid-nonobj.js
index 4b9f4d994c..ffdd4a5b87 100644
--- a/rpc/testdata/invalid-nonobj.js
+++ b/rpc/testdata/invalid-nonobj.js
@@ -2,3 +2,6 @@
 
 --> 1
 <-- {"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}}
+
+--> null
+<-- {"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"invalid request"}}