tunnelterm 0.1.7

Web-based terminal: run any shell command in a PTY, accessed through the browser over WebSocket.

tunnelterm

A web-based terminal: spawn any shell command in a real PTY and interact with it from the browser over WebSocket.

• Password-protected (per-IP rate limited)
• HttpOnly + SameSite=Strict session cookie — JS never sees the token
• Single-active-session per token
• Fail-closed Origin allow-list required on non-loopback binds
• Token TTL + LRU eviction
• Sticky PTY sessions: page refresh keeps your shell alive
• Themes, fonts, search, web-links, WebGL renderer
• Persistent UI preferences in the browser

Install

uv tool install tunnelterm
# or
uv pip install tunnelterm

Run

--command is required. Examples:

TUNNELTERM_PASSWORD=hunter2 tunnelterm --command bash
TUNNELTERM_PASSWORD=hunter2 tunnelterm --command "zsh -l"
TUNNELTERM_PASSWORD=hunter2 tunnelterm --command htop --port 4242

Open http://127.0.0.1:4200 and log in with the password.

CLI options

Option	Description	Default
--command	Command to run in the PTY. Required.	—
--host	Host to bind to	127.0.0.1
--port	Port to bind to	4200
--password-env	Env var name to read the password from	TUNNELTERM_PASSWORD
--config	Path to TOML config file	~/.config/tunnelterm/config.toml
--allowed-origin	Allowed Origin value (repeat). Required on non-loopback binds.	—
--allow-any-origin	Disable Origin allow-list (unsafe; explicit escape hatch)	off
--cookie-insecure	Omit Secure flag on cookies (only needed for plain-HTTP non-loopback)	auto (Secure on, off on loopback)
--enable-hsts	Emit Strict-Transport-Security (HTTPS-only deployments)	off
--session-idle-timeout	Seconds to keep an unattached PTY alive before reaping	18000 (5h)
--log-level	Log level: DEBUG, INFO, WARNING, ERROR	INFO
--version	Print version and exit	—

Environment variables

Variable	Description
TUNNELTERM_PASSWORD	Password for authentication (REQUIRED)
TUNNELTERM_HOST	Bind host
TUNNELTERM_PORT	Bind port
TUNNELTERM_COMMAND	PTY command (if --command not given)
TUNNELTERM_ALLOWED_ORIGINS	Comma-separated Origin allow-list
TUNNELTERM_SESSION_IDLE_TIMEOUT	Idle timeout in seconds
LOG_LEVEL	Log level fallback

Config file

~/.config/tunnelterm/config.toml:

password = "hunter2"
command = "bash"
host = "127.0.0.1"
port = 4200
allowed_origins = ["https://terminal.example.com"]
session_idle_timeout = 18000
enable_hsts = true

chmod 600 is recommended — tunnelterm logs a warning if the file is group- or world-readable.

Behind nginx with HTTPS (recommended for any non-loopback deployment)

Plaintext ws:// is fine for 127.0.0.1 only. For any other deployment, terminate TLS at a reverse proxy. Minimal nginx example:

server {
    listen 443 ssl http2;
    server_name terminal.example.com;

    ssl_certificate     /etc/letsencrypt/live/terminal.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/terminal.example.com/privkey.pem;

    location / {
        proxy_pass http://127.0.0.1:4200;
        proxy_http_version 1.1;
        proxy_set_header Host              $host;
        proxy_set_header X-Real-IP         $remote_addr;
        proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Upgrade           $http_upgrade;
        proxy_set_header Connection        "upgrade";
        proxy_read_timeout 1h;
    }
}

Then run tunnelterm with:

tunnelterm \
  --command bash \
  --allowed-origin https://terminal.example.com \
  --enable-hsts

Cookies will automatically get Secure set because the bind is loopback while the public scheme is HTTPS.

Systemd

sudo cp systemd/tunnelterm.service /etc/systemd/system/
# Edit User=, WorkingDirectory=, and ExecStart=.
sudo mkdir -p /etc/tunnelterm
sudo cp systemd/env.example /etc/tunnelterm/env
sudo chmod 600 /etc/tunnelterm/env
sudo $EDITOR /etc/tunnelterm/env  # set TUNNELTERM_PASSWORD

sudo systemctl daemon-reload
sudo systemctl enable --now tunnelterm
sudo journalctl -u tunnelterm -f

Session persistence

tunnelterm keeps your shell alive between connections so a page refresh, a brief network drop, or closing and reopening a tab does not throw you back into a fresh shell.

• Each session token has one PTY bound to it on the server. Reconnecting with the same token attaches you to the existing shell.
• On reattach the server replays the last 1 MB of PTY output, so the screen redraws to match what you were looking at.
• "Keep me signed in" on the login page makes the cookie persistent (Max-Age = token TTL, default 24h). Unchecked, it's a session cookie that dies when the browser closes.
• Sessions are reaped after --session-idle-timeout seconds of having no client attached (default 5h). The PTY is SIGKILLed.
• Explicit logout (settings drawer → Logout) revokes the token, kills the PTY, and clears the cookie immediately.

Security model

Token storage

• The session token is stored in an HttpOnly; Secure; SameSite=Strict cookie. JavaScript cannot read or exfiltrate it, even via XSS.
• The browser carries the cookie automatically on /api/* POSTs and the /ws WebSocket upgrade.

CSRF / CSWSH

• SameSite=Strict blocks the cookie on cross-site requests.
• An additional Origin allow-list is enforced on every POST and WebSocket handshake. The server refuses to start on a non-loopback bind unless --allowed-origin is given (or --allow-any-origin explicitly opted into).

Brute force / abuse

• 5 failed /api/auth attempts from one IP within 15 min → 5 min lockout.
• /api/verify is rate-limited at 60 hits/IP/min.
• WebSocket text frames are capped at 1 MiB to prevent memory exhaustion.

Lifecycle

• Tokens expire after 24 h by default; LRU-evicted at 64 outstanding.
• Each token may only be active in one WebSocket connection at a time.
• Log lines include a SHA-256 fingerprint of the token, never the token itself.

HTTP hardening

• CSP: default-src 'self'; script-src 'self'; connect-src 'self' etc. No wildcard ws/wss, no inline scripts.
• X-Content-Type-Options: nosniff, X-Frame-Options: DENY, Referrer-Policy: no-referrer, Permissions-Policy locking down hardware APIs.
• Optional Strict-Transport-Security via --enable-hsts.
• xterm assets are vendored locally with SRI hashes; no third-party CDN trust.

Development

uv sync
uv run pytest
uv run ruff check
uv run pyright