Encode as bytes

Author: FrederikBolding

packages/snaps-controllers/src/services/webview/WebViewMessageStream.ts

@@ -2,7 +2,7 @@ import type { PostMessageEvent } from '@metamask/post-message-stream';
 import { BasePostMessageStream } from '@metamask/post-message-stream';
 import { isValidStreamMessage } from '@metamask/post-message-stream/dist/utils';
 import { logError } from '@metamask/snaps-utils';
-import { assert } from '@metamask/utils';
+import { assert, stringToBytes } from '@metamask/utils';
 
 export type WebViewInterface = {
   injectJavaScript(js: string): void;
@@ -65,7 +65,9 @@ export class WebViewMessageStream extends BasePostMessageStream {
       data,
     });
 
-    this.#webView.injectJavaScript(`window.postMessage('${json}')`);
+    const bytes = new Uint8Array(stringToBytes(json));
+
+    this.#webView.injectJavaScript(`window.postMessage([${bytes.toString()}])`);
   }
 
   private _onMessage(event: PostMessageEvent): void {

packages/snaps-execution-environments/src/webview/WebViewExecutorStream.ts

@@ -1,6 +1,7 @@
 import type { PostMessageEvent } from '@metamask/post-message-stream';
 import { BasePostMessageStream } from '@metamask/post-message-stream';
 import { isValidStreamMessage } from '@metamask/post-message-stream/dist/utils';
+import { bytesToString } from '@metamask/utils';
 
 type WebViewExecutorStreamArgs = {
   name: string;
@@ -61,11 +62,12 @@ export class WebViewExecutorStream extends BasePostMessageStream {
   }
 
   private _onMessage(event: PostMessageEvent): void {
-    if (typeof event.data !== 'string') {
+    if (!Array.isArray(event.data)) {
       return;
     }
 
-    const message = JSON.parse(event.data);
+    const json = bytesToString(new Uint8Array(event.data as number[]));
+    const message = JSON.parse(json);
 
     // Notice that we don't check targetWindow or targetOrigin here.
     // This doesn't seem possible to do in RN.