Refuse to migrate from top into non-top documents (#42)

packages/core/src/element.mjs

@@ -53,4 +53,8 @@ export const distraction = invoker(creator({
     'top': '-10px', 'right': '-10px', 'position': 'fixed',
     // font-size smaller than 1px fails to be a distraction on Firefox
     'font-size': '1px',
-}, () => 'span', all));
+}, () => 'span', all));
+
+export const loadable = invoker(creator({
+    'display': 'none',
+}, () => 'iframe'));

packages/core/src/lavadome.mjs

@@ -9,11 +9,13 @@ import {
     appendChild,
     replaceChildren,
     textContentSet,
+    addEventListener,
+    ownerDocument,
     navigation,
     url, destination, includes,
     preventDefault, stopPropagation,
 } from './native.mjs';
-import {distraction, hardened} from './element.mjs';
+import {distraction, loadable, hardened} from './element.mjs';
 import {getShadow} from './shadow.mjs';
 
 // text-fragments links can be abused to leak shadow internals - block in-app redirection to them
@@ -37,6 +39,18 @@ export function LavaDome(host, opts) {
     const shadow = getShadow(host, opts);
     replaceChildren(shadow);
 
+    // fire every time instance is reloaded and abort loading for non-top documents
+    const iframe = loadable();
+    addEventListener(iframe, 'load', () => {
+        const ownerDoc = ownerDocument(iframe);
+        if (ownerDoc !== document) {
+            replaceChildren(shadow);
+            throw new Error(`LavaDomeCore: ` +
+                `The document to which LavaDome was originally introduced ` +
+                `must be the same as the one this instance is inserted to`);
+        }
+    });
+
     // child of the shadow, where the secret is set, must be hardened
     const child = hardened();
     appendChild(shadow, child);
@@ -54,6 +68,9 @@ export function LavaDome(host, opts) {
             return textContentSet(child, text);
         }
 
+        // attach loadable only once per instance to avoid excessive load firing
+        appendChild(shadow, iframe);
+
         // place each char of the secret in its own LavaDome protection instance
         map(from(text), char => {
             const span = createElement(document, 'span');
@@ -66,4 +83,4 @@ export function LavaDome(host, opts) {
         // add a distraction against side channel leaks attack attempts
         appendChild(child, distraction());
     }
-}
+}

packages/core/src/native.mjs

@@ -20,6 +20,8 @@ const { stringify } = JSON;
 const n = (obj, prop, accessor) =>
     obj && Function.prototype.call.bind(getOwnPropertyDescriptor(obj, prop)[accessor]);
 
+export const ownerDocument = n(globalThis?.Node?.prototype, 'ownerDocument', 'get');
+export const addEventListener = n(globalThis?.EventTarget?.prototype, 'addEventListener', 'value');
 export const replaceChildren = n(globalThis?.DocumentFragment?.prototype, 'replaceChildren', 'value');
 export const attachShadow = n(globalThis?.Element?.prototype, 'attachShadow', 'value');
 export const createElement = n(globalThis?.Document?.prototype, 'createElement', 'value');