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Leave your VPN and cURL secure APIs with Cloudflare Access

by Sam Rhea.

We built Access to solve a problem here at Cloudflare: our VPN. Our team members hated the slowness and inconvenience of VPN but, that wasn’t the issue we needed to solve. The security risks posed by a VPN required a better solution.

VPNs punch holes in the network perimeter. Once inside, individuals can access everything. This can include  critically sensitive content like private keys, cryptographic salts, and log files. Cloudflare is a security company; this situation was unacceptable. We need a better method that gives every application control over precisely who is allowed to  reach it.

Access meets that need. We started by moving our browser-based applications behind Access. Team members could connect to applications faster, from anywhere, while we improved the security of the entire organization. However, we weren’t yet ready to turn off our VPN as some tasks are better done through a command line. We cannot #EndTheVPN without replacing all of its use cases. Reaching a server from the command line required us to fall back to our VPN.

Today, we’re releasing a beta command line tool to help your team, and ours. Before we started using this feature at Cloudflare, curling a server required me to stop, find my VPN client and credentials, login, and run my curl command. With Cloudflare’s command line tool, cloudflared, and Access, I can run $ cloudflared access curl https://example.com/api and Cloudflare authenticates my request to the server. I save time and the security team at Cloudflare can control who reaches that endpoint (and monitor the logs).

Protect your API with Cloudflare Access

To protect an API with Access, you’ll follow the same steps that you use to protect a browser-based application. Start by adding the hostname where your API is deployed to your Cloudflare account.

Just like web applications behind Access, you can create granular policies for different paths of your HTTP API. Cloudflare Access will evaluate every request to the API for permission based on settings you configure. Placing your API behind Access means requests from any operation, CLI or other, will continue to be gated by Cloudflare. You can continue to use your API keys, if needed, as a second layer of security.

Reach a protected API

Cloudflare Access protects your application by checking for a valid JSON Web Token (JWT), whether the request comes through a browser or from the command line. We issue and sign that JWT when you successfully login with your identity provider. That token contains claims about your identity and session. The Cloudflare network looks at the claims in that token to determine if the request should proceed to the target application.

When you use a browser with Access, we redirect you to your identity provider, you login, and we store that token in a cookie. Authenticating from the command line requires a different flow, but relies on the same principles. When you need to reach an application behind Access from your command line, the Cloudflare CLI tool, cloudflared, launches a browser window so that you can login with your identity provider. Once you login, Access will generate a JWT for your session, scoped to your user identity.

Rather than placing that JWT in a cookie, Cloudflare transfers the token in a cryptographically secure handoff to your machine. The client stores the token for you so that you don’t need to re-authenticate each time. The token is valid for the session duration as configured in Access.

When you make requests from your command line, Access will look for an HTTP header, cf-access-token, instead of a cookie. We’ll evaluate the token in that header and on every request.  If you use cURL, we can help you move even faster. cloudflared includes a subcommand that wraps cURL and injects the JWT into the header for you.

Why use cloudflared to reach your application?

With cloudflared and its cURL wrapper, you can perform any cURL operation against an API protected by Cloudflare Access.

  • Control endpoint access for specific users
    Cloudflare Access can be configured to protect specific endpoints. For example, you can create a rule that only a small group within your team can reach a particular URL path. You can apply that granular protection to sensitive endpoints so that you control who can reach those, while making other parts of the tool available to the full team.
  • Download sensitive data
    Placing applications with sensitive data behind Access lets you control who can reach that information. If a particular file is stored at a known location, you can save time by downloading it to your machine from the command line instead of walking through the UI flow.

What's next?

CLI authentication is available today to all Access customers through the cloudflared tool. Just add the API hostname to your Cloudflare account and enable Access to start building policies that control who can reach that API. If you do not have an Access subscription yet, you can read more about the plans here and sign up.

Once you’re ready to continue ditching your VPN, follow this link to install cloudflared today. The tool is in beta and does not yet support automated scripting or service-to-service connections. Full instructions and known limitations can be found here. If you are interested in providing feedback, you can post your comments in this thread.

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