cordis/client/webapp/socket-verifier.ts

import * as crypto from 'crypto';
import * as socketio from 'socket.io-client';
import { EventEmitter } from 'tsee';

import DedupAwaiter from "./dedup-awaiter";
import Util from './util';

// Automatically re-verifies the socket when connected
export default class SocketVerifier extends EventEmitter<{ 'verified': () => void }> {
	public isVerified = false;
	private memberId: string | null = null;
	private verifyDedup = new DedupAwaiter(async () => { return await this.doVerify(); });

	constructor(
		private socket: socketio.Socket,
		private publicKey: crypto.KeyObject,
		private privateKey: crypto.KeyObject
	) {
		super();
		socket.on('connect', async () => {
			await this.verify();
		});
		socket.on('disconnect', () => {
			this.isVerified = false;
		});
	}

	/** Verifies this client with the server. This function must be called before the server will send messages or give results */
	private async doVerify(): Promise<string> {
		if (this.socket.disconnected) throw new Error('socket is disconnected');
		if (this.memberId) return this.memberId;
		return await new Promise<string>(async (resolve, reject) => {
			// Solve the server's challenge
			let publicKeyBuff = this.publicKey.export({ type: 'spki', format: 'der' });
			Util.socketEmitTimeout(this.socket, 5000, 'challenge', publicKeyBuff, (errMsg: string, algo: string, type: crypto.BinaryToTextEncoding, challenge: Buffer) => {
				if (errMsg) {
					reject(new Error('challenge request failed: ' + errMsg));
					return;
				}
				const sign = crypto.createSign(algo);
				sign.write(challenge);
				sign.end();
		
				let signature = sign.sign(this.privateKey, type);
				Util.socketEmitTimeout(this.socket, 5000, 'verify', signature, (errMsg: string, memberId: string) => {
					if (errMsg) {
						reject(new Error('verification request failed: ' + errMsg));
						return;
					}
					this.memberId = null;
					resolve(memberId);
					this.emit('verified');
				});
			});
		});
	}

	// returns the memberId
	public async verify(): Promise<string> {
		return await this.verifyDedup.call();
	}

	// TODO: ensureVerified for send/update requests that may need to be in-order?
	public async ensureVerified() {
		if (this.isVerified) return;
		await this.verify();
	}
}