Sandbox: explore how to support direct helper process to renderer communication

[bpasero]

Allow direct communication between a helper process and the renderer.

Some raw ideas

• what if Electron would provide an API similar to BrowserWindow.loadUrl but UtilityProcess.loadUrl to create such a child process
• Electron should delegate this to Chrome and reuse the ability Chrome has to spawn utility processes like GPU and Network
• Utility process has node.js integration enabled and direct communication support to a renderer (either via electron IPC or message ports)

[Tyriar]

@deepak1556 any update on this? Do we have an upstream issue we can link?

[deepak1556]

Prototype demonstrating communication between Node integration enabled chromium service process and sandbox renderer is complete.

Link: https://streamable.com/tqozwr

Current state of API:

// Main Process
interface ProcessOptions {
 displayName?: string | undefined;
 execArgv?: string[] | undefined;
 env?: NodeJS.ProcessEnv | undefined;
}

interface MessageEvent {
  data: any;
}

class UtilityProcess extends NodeJS.EventEmitter {

 constructor(modulePath: string, args?: string[] | undefined, options?: ProcessOptions);

 readonly pid?: number | undefined;

 /*
  * Pending Implementation
 postMessage(channel: string, message: any, transfer?: Electron.MessagePortMain[]): void;
  */

 kill(signal: number): boolean;

 /*
  * Pending Implementation
 on(event: 'message', listener: (event: MessageEvent) => void): this;
  */
 
 on(event: 'exit', listener: (code: number) => void): this;

 on(event: 'spawn', listener: (void) => void): this;
}

// Service Process
interface MessageEvent {
 data: any;
 ports: MessagePortMain[];
}

interface Process extends NodeJS.EventEmitter {

 on(channel: string, listener: (event: MessageEvent) => void): this;

 /*
  * Pending Implementation
 send(message: any);
  */
}

[deepak1556]

Next Steps in order:

• Create custom builds with the new API
• Implement extension host with the above API (refs vscode#135268) and iron out edge cases if any
• Send RFC PR to https://github.com/electron/governance/tree/main/wg-api/spec-documents
• Upstream implementation PR to https://github.com/electron/electron

[safasofuoglu]

Will this work enable shareable non-copy buffers, rather than one-way ownership transfer?

[deepak1556]

Exploration is complete and extension host has adopted this behind a setting. Next steps continued in #154007