rpc: check that "version" is "2.0" in request objects (ethereum#25570)

The JSON-RPC spec requires the "version" field to be exactly "2.0",
so we should verify that. This change is not backwards-compatible with
sloppy client implementations, but I decided to go ahead with it anyway
because the failure will be caught via the returned error.

rpc/json.go

@@ -58,21 +58,25 @@ type jsonrpcMessage struct {
 }
 
 func (msg *jsonrpcMessage) isNotification() bool {
-	return msg.ID == nil && msg.Method != ""
+	return msg.hasValidVersion() && msg.ID == nil && msg.Method != ""
 }
 
 func (msg *jsonrpcMessage) isCall() bool {
-	return msg.hasValidID() && msg.Method != ""
+	return msg.hasValidVersion() && msg.hasValidID() && msg.Method != ""
 }
 
 func (msg *jsonrpcMessage) isResponse() bool {
-	return msg.hasValidID() && msg.Method == "" && msg.Params == nil && (msg.Result != nil || msg.Error != nil)
+	return msg.hasValidVersion() && msg.hasValidID() && msg.Method == "" && msg.Params == nil && (msg.Result != nil || msg.Error != nil)
 }
 
 func (msg *jsonrpcMessage) hasValidID() bool {
 	return len(msg.ID) > 0 && msg.ID[0] != '{' && msg.ID[0] != '['
 }
 
+func (msg *jsonrpcMessage) hasValidVersion() bool {
+	return msg.Version == vsn
+}
+
 func (msg *jsonrpcMessage) isSubscribe() bool {
 	return strings.HasSuffix(msg.Method, subscribeMethodSuffix)
 }

rpc/subscription_test.go

@@ -79,7 +79,7 @@ func TestSubscriptions(t *testing.T) {
 		request := map[string]interface{}{
 			"id":      i,
 			"method":  fmt.Sprintf("%s_subscribe", namespace),
-			"version": "2.0",
+			"jsonrpc": "2.0",
 			"params":  []interface{}{"someSubscription", notificationCount, i},
 		}
 		if err := out.Encode(&request); err != nil {

rpc/testdata/invalid-badversion.js

@@ -0,0 +1,19 @@
+// This test checks processing of messages with invalid Version.
+
+--> {"jsonrpc":"2.0","id":1,"method":"test_echo","params":["x", 3]}
+<-- {"jsonrpc":"2.0","id":1,"result":{"String":"x","Int":3,"Args":null}}
+
+--> {"jsonrpc":"2.1","id":1,"method":"test_echo","params":["x", 3]}
+<-- {"jsonrpc":"2.0","id":1,"error":{"code":-32600,"message":"invalid request"}}
+
+--> {"jsonrpc":"go-ethereum","id":1,"method":"test_echo","params":["x", 3]}
+<-- {"jsonrpc":"2.0","id":1,"error":{"code":-32600,"message":"invalid request"}}
+
+--> {"jsonrpc":1,"id":1,"method":"test_echo","params":["x", 3]}
+<-- {"jsonrpc":"2.0","id":1,"error":{"code":-32600,"message":"invalid request"}}
+
+--> {"jsonrpc":2.0,"id":1,"method":"test_echo","params":["x", 3]}
+<-- {"jsonrpc":"2.0","id":1,"error":{"code":-32600,"message":"invalid request"}}
+
+--> {"id":1,"method":"test_echo","params":["x", 3]}
+<-- {"jsonrpc":"2.0","id":1,"error":{"code":-32600,"message":"invalid request"}}