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sealos-tty-bridge

Kubernetes exec terminal gateway over WebSocket.

Browser (xterm.js) <-> this server (WS) <-> Kubernetes API Server (exec) <-> Pod PTY

What’s in this repo

  • Server: sealos-tty-bridge — a small HTTP + WebSocket gateway that turns Kubernetes pods/exec into a browser-friendly terminal stream.
  • Client: @labring/sealos-tty-client — a Web Streams API client (in packages/protocol-client) that handles WebSocket auth + stream wiring for you.

Server usage

Local (dev)

pnpm install
cp config.example.json config.json
pnpm run dev

Default: http://localhost:3000.

Production

# Using Docker Compose
docker compose up -d

# or use Docker CLI
# Build the image
docker build -t sealos-tty-bridge:latest .
# Spin up the container
docker run -d -p 3000:3000 -v $(pwd)/config.json:/app/config.json:ro sealos-tty-bridge:latest

Client usage

The recommended client is @labring/sealos-tty-client (Web Streams API), designed for browser terminals like xterm.js.

pnpm add @labring/sealos-tty-client

Minimal browser example (xterm-style wiring):

import { connectTerminalStreams } from '@labring/sealos-tty-client'

const { stdout, stdin, resize } = await connectTerminalStreams({
	client: { baseUrl: 'http://localhost:3000' },
	connect: {
		kubeconfig,
		target: { namespace: 'default', pod: 'mypod', container: 'c1' },
		initialSize: { cols: term.cols, rows: term.rows },
	},
})

const enc = new TextEncoder()
const writer = stdin.getWriter()
term.onData(d => void writer.write(enc.encode(d)))
term.onResize(({ cols, rows }) => resize(cols, rows))

void stdout
	.pipeThrough(new TextDecoderStream())
	.pipeTo(new WritableStream({ write: s => term.write(s) }))

Notes:

  • The server starts Kubernetes exec only after receiving the first resize.
  • By default the client offers kubeconfig in Sec-WebSocket-Protocol using a stable sealos-tty-v1 token plus a URL-encoded data-bearing token. Set connect.authInMessage = true to send kubeconfig in the first auth frame instead.
  • KUBE_API_SERVER overrides the current cluster server in user kubeconfigs. Set it to auto to derive https://$KUBERNETES_SERVICE_HOST:$KUBERNETES_SERVICE_PORT_HTTPS inside a Kubernetes pod.

Run

pnpm install
pnpm run dev

API

GET /exec (WebSocket)

  • Query parameters:
    • namespace=<namespace>
    • pod=<pod>
    • optional container=<container>
    • optional repeated command=<argv-part> entries
  • Authentication:
    • Preferred: offer sealos-tty-v1 plus a kubeconfig-bearing token in Sec-WebSocket-Protocol; the server validates kubeconfig and echoes only sealos-tty-v1.
    • Fallback: if kubeconfig is not offered in the handshake, the first non-ping JSON message must be { "type": "auth", "kubeconfig": "..." }.
  • After auth, the client must send the first resize:
    • { "type": "resize", "cols": 120, "rows": 30 }
    • The server starts Kubernetes exec only after receiving the first resize.

Binary frames:

  • Client -> Server: stdin bytes
  • Server -> Client: stdout/stderr bytes (TTY usually merged)

Security

kubeconfig is sensitive. Use HTTPS/WSS and restrict RBAC for pods/exec.