More robust message checking in socket providers (#4051).

Author: ricmoo

src.ts/providers/provider-socket.ts

@@ -231,7 +231,7 @@ export class SocketProvider extends JsonRpcApiProvider {
     async _processMessage(message: string): Promise<void> {
         const result = <JsonRpcResult | JsonRpcError | JsonRpcSubscription>(JSON.parse(message));
 
-        if ("id" in result) {
+        if (result && typeof(result) === "object" && "id" in result) {
             const callback = this.#callbacks.get(result.id);
             if (callback == null) {
                 this.emit("error", makeError("received result for unknown id", "UNKNOWN_ERROR", {
@@ -244,7 +244,7 @@ export class SocketProvider extends JsonRpcApiProvider {
 
             callback.resolve(result);
 
-        } else if (result.method === "eth_subscription") {
+        } else if (result && result.method === "eth_subscription") {
             const filterId = result.params.subscription;
             const subscriber = this.#subs.get(filterId);
             if (subscriber) {
@@ -257,6 +257,13 @@ export class SocketProvider extends JsonRpcApiProvider {
                 }
                 pending.push(result.params.result);
             }
+
+        } else {
+            this.emit("error", makeError("received unexpected message", "UNKNOWN_ERROR", {
+                reasonCode: "UNEXPECTED_MESSAGE",
+                result
+            }));
+            return;
         }
     }