fix(selfbot): smooth VNC capture via keepalive + stop ffmpeg leak on stream end
The Go-Live broadcast looked badly choppy: video and scrolling stuttered while the cursor stayed smooth. Root cause is TigerVNC: it only refreshes its framebuffer while a VNC client is attached, but the broadcast reads that framebuffer with x11grab (not as a VNC client). With no viewer attached the captured screen idled at ~1.5 fps (measured 3/30 distinct frames); the cursor looked smooth only because x11grab overlays the live cursor on every frame. - Add a headless RFB keepalive (vnc-keepalive.ts) that stays connected for the life of the stream and requests incremental framebuffer updates at the stream framerate. SelfbotStreamer starts it on broadcast start and tears it down on stop/self-end. Measured 3/30 -> 57/60 distinct frames at 60 fps. Fail-open; authenticates with VNC_PASSWORD or the ~/.config/tigervnc/passwd file. - Fix a resource leak: when the Go-Live ended on its own, only the active flag was cleared, leaving the x11grab->nvenc ffmpeg running forever (pinning a CPU core while no media was transmitted, with only the gateway TCP left and no UDP media). The self-end path now tears down capture, keepalive and voice like stop() does. - Tests for both paths (self-end teardown; keepalive DES auth, port mapping, password resolution). Add @types/bun so bun:test typechecks; document the keepalive and recommended Chrome flags in README and .env.example. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
javis-bot
203
bot/src/stream/vnc-keepalive.ts
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203
bot/src/stream/vnc-keepalive.ts
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/**
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* Headless RFB (VNC) keepalive client.
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*
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* TigerVNC's Xvnc only flushes pending rendering into the readable framebuffer
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* while a VNC client is actively pulling updates. The Discord broadcast reads
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* that framebuffer with x11grab (it is NOT a VNC client), so with no viewer
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* attached Xvnc idles and the captured screen updates at ~1.5 fps - the stream
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* looks badly choppy even though Chrome renders at 60 fps. (Measured: 3/30
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* distinct frames without a client, 30/30 with one.)
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*
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* This client stays connected to the VNC server and continuously requests
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* incremental framebuffer updates, keeping the framebuffer fresh for the whole
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* duration of a broadcast. It is intentionally fail-open: any connection/auth
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* problem is logged and retried, never thrown, so it can never break the stream.
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*/
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import net from "node:net";
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import crypto from "node:crypto";
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import { readFileSync } from "node:fs";
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import { homedir } from "node:os";
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// VNC's DES variant uses each key byte with its bits mirrored.
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function revByte(b: number): number {
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let r = 0;
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for (let i = 0; i < 8; i++) r = (r << 1) | ((b >> i) & 1);
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return r & 0xff;
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}
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function vncKey(buf: Buffer): Buffer {
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return Buffer.from([...buf.subarray(0, 8)].map(revByte));
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}
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function desEcb(key: Buffer, data: Buffer, decrypt = false): Buffer {
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const c = decrypt
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? crypto.createDecipheriv("des-ecb", key, null)
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: crypto.createCipheriv("des-ecb", key, null);
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c.setAutoPadding(false);
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return Buffer.concat([c.update(data), c.final()]);
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}
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// The fixed key TigerVNC/RealVNC use to obfuscate the stored password file.
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const FIXED_KEY = Buffer.from([23, 82, 107, 6, 35, 78, 88, 7]);
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/** Decode an 8-byte obfuscated VNC password file payload to plaintext. */
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export function decodeVncPassword(obf: Buffer): Buffer {
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const pt = desEcb(vncKey(FIXED_KEY), obf.subarray(0, 8), true);
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const z = pt.indexOf(0);
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return pt.subarray(0, z < 0 ? 8 : z);
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}
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/** Compute the 16-byte VncAuth response for a server challenge. */
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export function vncChallengeResponse(password: Buffer, challenge: Buffer): Buffer {
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const key = Buffer.alloc(8);
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password.subarray(0, 8).copy(key);
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return desEcb(vncKey(key), challenge.subarray(0, 16));
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}
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/** Map an X display like ":1" to its TigerVNC RFB port (5900 + n). */
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export function vncPortForDisplay(display: string): number {
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const n = parseInt(String(display).replace(/^:/, ""), 10);
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return 5900 + (Number.isFinite(n) ? n : 0);
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}
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/**
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* Resolve the VNC password: VNC_PASSWORD (plaintext) wins, otherwise decode the
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* obfuscated passwd file (VNC_PASSWD_FILE, default ~/.config/tigervnc/passwd).
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* Returns null when nothing is available (caller then skips the keepalive).
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*/
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export function resolveVncPassword(env: NodeJS.ProcessEnv = process.env): Buffer | null {
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if (env.VNC_PASSWORD) return Buffer.from(env.VNC_PASSWORD, "utf8").subarray(0, 8);
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const file = env.VNC_PASSWD_FILE || `${homedir()}/.config/tigervnc/passwd`;
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try {
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const obf = readFileSync(file);
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if (obf.length >= 8) return decodeVncPassword(obf);
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} catch {
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/* no file - fall through */
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}
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return null;
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}
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export class VncKeepalive {
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private sock: net.Socket | null = null;
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private timer: ReturnType<typeof setInterval> | null = null;
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private retry: ReturnType<typeof setTimeout> | null = null;
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private stopped = false;
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constructor(
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private opts: { host: string; port: number; password: Buffer; fps?: number },
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) {}
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start(): void {
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this.stopped = false;
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this.connect();
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}
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stop(): void {
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this.stopped = true;
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if (this.timer) clearInterval(this.timer);
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if (this.retry) clearTimeout(this.retry);
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this.timer = this.retry = null;
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try {
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this.sock?.destroy();
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} catch {
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/* ignore */
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}
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this.sock = null;
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}
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private scheduleReconnect(): void {
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if (this.stopped || this.retry) return;
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this.retry = setTimeout(() => {
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this.retry = null;
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if (!this.stopped) this.connect();
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}, 2000);
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}
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private connect(): void {
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const sock = net.connect(this.opts.port, this.opts.host);
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this.sock = sock;
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sock.setNoDelay(true);
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let buf = Buffer.alloc(0);
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const waiters: { n: number; res: (b: Buffer) => void }[] = [];
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const pump = () => {
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while (waiters.length && buf.length >= waiters[0].n) {
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const w = waiters.shift()!;
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const d = buf.subarray(0, w.n);
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buf = buf.subarray(w.n);
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w.res(d);
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}
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};
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const onData = (d: Buffer) => {
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buf = Buffer.concat([buf, d]);
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pump();
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};
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sock.on("data", onData);
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sock.on("error", () => {
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/* handled by close */
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});
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sock.on("close", () => {
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if (this.sock === sock) {
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this.sock = null;
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if (this.timer) {
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clearInterval(this.timer);
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this.timer = null;
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}
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this.scheduleReconnect();
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}
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});
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const read = (n: number) =>
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new Promise<Buffer>((res) => {
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waiters.push({ n, res });
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pump();
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});
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(async () => {
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try {
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await read(12); // ProtocolVersion
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sock.write("RFB 003.008\n");
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const nTypes = (await read(1))[0];
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const types = await read(nTypes);
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if (types.includes(2)) {
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sock.write(Buffer.from([2])); // VNC Auth
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const challenge = await read(16);
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sock.write(vncChallengeResponse(this.opts.password, challenge));
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if ((await read(4)).readUInt32BE(0) !== 0) return sock.destroy();
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} else if (types.includes(1)) {
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sock.write(Buffer.from([1])); // None
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if ((await read(4)).readUInt32BE(0) !== 0) return sock.destroy();
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} else {
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return sock.destroy();
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}
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sock.write(Buffer.from([1])); // ClientInit (shared)
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const si = await read(24);
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const w = si.readUInt16BE(0);
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const h = si.readUInt16BE(2);
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await read(si.readUInt32BE(20)); // desktop name
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sock.write(Buffer.from([2, 0, 0, 1, 0, 0, 0, 0])); // SetEncodings: Raw
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// Past the handshake: stop buffering and just drain whatever the server
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// sends so its send buffer never blocks (we never decode the pixels).
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sock.removeListener("data", onData);
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sock.on("data", () => {});
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buf = Buffer.alloc(0);
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const req = Buffer.from([3, 1, 0, 0, 0, 0, 0, 0, 0, 0]);
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req.writeUInt16BE(w, 6);
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req.writeUInt16BE(h, 8);
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const interval = Math.max(1, Math.round(1000 / (this.opts.fps ?? 60)));
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this.timer = setInterval(() => {
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try {
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if (this.sock === sock && sock.writable) sock.write(req);
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} catch {
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/* ignore */
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}
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}, interval);
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} catch {
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try {
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sock.destroy();
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} catch {
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/* ignore */
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}
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}
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})();
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}
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}
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