reverse tunnel

client.js

const net = require("net");
const http = require("http");
const https = require("https");
const http2 = require("http2");

const req = https.request({
    method: "CONNECT",
    host: "server",
    port: 443,
    path: "magic.string"
});
req.end();
req.on("connect", (res, socket) => {
    if (res.statusCode === 200) {
        createServer(socket);
    }
});

function createServer(socket) {
    socket.ref();

    const server = http2.createServer((req, res) => {
        const [host, port = "80"] = req.headers.host.split(":");
        const req2 = http.request({
            host: host,
            port: parseInt(port, 10),
            path: req.url,
            headers: req.headers,
        });
        req2.on("response", (res2) => {
            delete res2.headers["connection"];
            delete res2.headers["keep-alive"];
            delete res2.headers["transfer-encoding"];
            delete res2.headers["upgrade"];

            res.writeHead(res.statusCode, res2.headers);
            res2.pipe(res);
        });
        req.pipe(req2);
    });
    server.on("connect", (req, res) => {
        const [host, port = "80"] = req.url.split(":");
        const connection = net.connect(parseInt(port, 10), host, () => {
            res.writeHead(200);

            req.pipe(connection);
            connection.pipe(req);
        });
    });
    server.emit("connection", socket);
}

server.js

const http = require("http");
const https = require("https");
const http2 = require("http2");

const server = https.createServer({
    // TODO: add certificates
}, (req, res) => {
    if (client) {
        delete req.headers["transfer-encoding"];
        const { host, ...headers } = req.headers;

        const stream = client.request({
            ":method": req.method,
            ":scheme": "http",
            ":authority": host,
            ":path": req.url,
            ...headers,
        });
        stream.on("response", (headers) => {
            const statusCode = headers[http2.constants.HTTP2_HEADER_STATUS];
            delete headers[http2.constants.HTTP2_HEADER_STATUS];

            res.writeHead(statusCode, http.STATUS_CODES[statusCode], headers);

            req.pipe(stream);
            stream.pipe(req);
        });
    }
});
let client;
server.on("connect", (req, socket, head) => {
    if (req.url === "magic.string") {
        socket.write("HTTP/1.1 200 OK\r\n\r\n");

        client = http2.connect("client", {
            protocol: "http",
            createConnection() {
                return socket;
            }
        });
    } else if (client) {
        delete req.headers["Host"];
        const stream = client.request({
            ":method": "CONNECT",
            ":authority": req.url,
            ...req.headers,
        });
        stream.on("response", (headers) => {
            const statusCode = headers[http2.constants.HTTP2_HEADER_STATUS];
            socket.write(`HTTP/1.1 ${statusCode} ${http.STATUS_CODES[statusCode]}\r\n`);

            delete headers[http2.constants.HTTP2_HEADER_STATUS];
            for (const [key, value] of Object.entries(headers)) {
                socket.write(`${key}: ${value}\r\n`);
            }

            socket.write("\r\n");

            stream.write(head);
            socket.pipe(stream);

            stream.pipe(socket);
        });
    }
});
server.listen(443);