Terminal-Based OAuth 2.0 Authentication with Ncurses

The terminal waited. A blinking cursor. No clutter, no noise—just you, Ncurses, and the challenge of implementing OAuth 2.0 without a browser.

Ncurses is a C library for building advanced terminal UIs. It's fast, portable, and perfect for systems that run headless. OAuth 2.0 is the most common protocol for secure API authentication. Bringing them together is rare. Most OAuth flows assume a web interface. But if you need to authenticate a command-line app or a server tool running in pure terminal space, you have to work differently.

The solution starts with the OAuth 2.0 Device Authorization Grant. It was designed for input-constrained devices, but it also works cleanly with Ncurses-based clients. You prompt the user with a verification URL and a code inside your Ncurses UI. The user opens the URL in any browser, enters the code, and your app polls the authorization server until it receives tokens.

Key steps to build Ncurses OAuth 2.0 authentication:

1. Register your app with the OAuth provider and enable the device authorization grant.
2. Initialize Ncurses and draw the UI frame for instructions and code display.
3. Make the initial POST to the provider’s device authorization endpoint. Parse verification_uri, user_code, and device_code.
4. Display the verification_uri and user_code in Ncurses. Include a countdown timer based on expires_in.
5. Poll the token endpoint with the device_code at the interval returned. Handle authorization_pending and slow_down responses according to the spec.
6. Store and use access/refresh tokens securely for API calls. Refresh before expiration without prompting the user again.

Terminal-based OAuth 2.0 with Ncurses has concrete advantages. The workflow stays in your application without dropping to a less controlled environment. The visual control, keyboard navigation, and status feedback are tight and predictable. You can integrate loading bars, colored prompts, and even error logs directly in one screen.

Security remains critical. Always use HTTPS for the OAuth endpoints. Never log full tokens. Clear sensitive data from Ncurses buffers after use. If your Ncurses app has background processes, make sure token refresh and storage follow least-privilege principles.

This approach makes it possible to give a CLI tool or a headless environment full API access with a robust OAuth standard—without a full browser stack.

You can see Ncurses OAuth 2.0 in action without boilerplate. Launch a working example on hoop.dev and watch it happen in minutes.