first commit

apps/browser/page-clipboard-guard.cjs

@@ -0,0 +1,55 @@
+'use strict';
+// This capability stays in the main process. Neither pages nor agents receive CDP access.
+const owners=new WeakMap();
+function protectClipboardPrimitives(){
+  const prototype=Document.prototype,existing=Object.getOwnPropertyDescriptor(prototype,'execCommand');
+  if(existing?.value?._managedClipboardGuard===true&&!existing.configurable)return;
+  const original=prototype.execCommand,apply=Reflect.apply,test=RegExp.prototype.test.bind(/^(copy|cut|paste)/i);
+  function managedClipboardCommand(command,...args){
+    if(typeof command!=='string'||test(command))return false;
+    return apply(original,this,[command,...args]);
+  }
+  Object.defineProperty(managedClipboardCommand,'_managedClipboardGuard',{value:true});
+  Object.defineProperty(prototype,'execCommand',{value:managedClipboardCommand,writable:false,configurable:false});
+  const SecurityException=DOMException;
+  const denyReplacement=()=>{throw new SecurityException('Managed document replacement is disabled','SecurityError');};
+  for(const name of ['open','write','writeln'])Object.defineProperty(prototype,name,{value:denyReplacement,writable:false,configurable:false});
+  const deny=event=>{event.preventDefault();event.stopImmediatePropagation();};
+  for(const name of ['copy','cut','paste','dragstart','dragover','drop'])window.addEventListener(name,deny,true);
+  const transferred=RegExp.prototype.test.bind(/^(insertFromPaste|insertFromDrop|deleteByCut)/);
+  window.addEventListener('beforeinput',event=>{if(transferred(event.inputType||''))deny(event);},true);
+}
+const source=`(${protectClipboardPrimitives.toString()})();`;
+function deadline(operation){let timer;return Promise.race([operation,new Promise((_,reject)=>{timer=setTimeout(()=>reject(Error('Page security initialization timed out')),5000);})]).finally(()=>clearTimeout(timer));}
+async function attachPageClipboardGuard(contents,onFailure){
+  const api=contents.debugger;
+  if(!api||api.isAttached()||owners.has(contents))throw Error('Page security initialization unavailable');
+  const owner={api,healthy:false};
+  const detached=()=>{owners.delete(contents);owner.healthy=false;if(!contents.isDestroyed())onFailure();};
+  owner.detached=detached;
+  api.on('detach',detached);
+  try{
+    api.attach('1.3');
+    await deadline(api.sendCommand('Page.enable',{}));
+    const registration=await deadline(api.sendCommand('Page.addScriptToEvaluateOnNewDocument',{source}));
+    if(typeof registration?.identifier!=='string'||!registration.identifier||!api.isAttached())throw Error('Page security initialization failed');
+    owner.healthy=true;owners.set(contents,owner);
+  }catch{
+    api.removeListener('detach',detached);
+    if(api.isAttached())api.detach();
+    throw Error('Page security initialization failed');
+  }
+}
+function guardedScreenshot(contents,parameters){
+  const owner=owners.get(contents);
+  if(!owner)return null;
+  if(!owner.healthy||owner.api!==contents.debugger||!owner.api.isAttached())throw Error('Page security connection unavailable');
+  // Only the fixed screenshot command is shared. There is no general command dispatcher.
+  return owner.api.sendCommand('Page.captureScreenshot',parameters);
+}
+function disposePageClipboardGuard(contents){
+  const owner=owners.get(contents);if(!owner)return;
+  owners.delete(contents);owner.healthy=false;owner.api.removeListener('detach',owner.detached);
+  if(owner.api.isAttached())owner.api.detach();
+}
+module.exports={attachPageClipboardGuard,guardedScreenshot,disposePageClipboardGuard};