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Wednesday, December 6, 2023

Securing the CLI with OAuth2 Gadget Authorization

Most corporations have sturdy exterior safety, e.g. blocking all entry to manufacturing belongings utilizing a firewall, and requiring a VPN to get “inside” entry to manufacturing environments. Nevertheless, as soon as you might be linked to the VPN, the inner programs are normally very poorly protected, and there’s little to no authentication and authorization for inner instruments and providers.

Two frequent threats to inner safety are compromised worker laptops and provide chain assaults. In these eventualities, the attacker operates behind the firewall, usually with unrestricted community entry.

Companies with an online ui may be secured utilizing an software load balancer, e.g. an AWS ALB with OIDC, however how do you defend entry to command line interface (CLI) based mostly instruments? Requiring a username and password for each CLI invocation makes it painful to make use of and storing the credentials on the system leaves them broad open in case the pc they reside on is compromised.

The Command Line

Most inner instruments have a CLI to handle the providers which can be used inside the firm and lots of are poorly protected. What’s one of the best ways to authorize CLIs? And how will you tie authorization into the corporate’s SSO?

One possibility is to deploy Hashicorp Vault, however that’s a whole lot of setup and upkeep, so except you have got a staff to function it, Vault may not be a very good match.

An alternative choice is the OAuth2 system authorization grant (RFC8628), which is what this weblog publish will present you how one can use.

The OAuth 2.0 system authorization grant is designed for Web-connected gadgets that both lack a browser to carry out a user-agent-based authorization or are enter constrained to the extent that requiring the person to enter textual content with the intention to authenticate through the authorization move is impractical. It allows OAuth purchasers on such gadgets (like good TVs, media consoles, digital image frames, and printers) to acquire person authorization to entry protected assets by utilizing a person agent on a separate system.

In case you ever used the AWS CLI with Single SignOn, that is what it does.

OAuth2 Gadget Movement

The Gadget Authorization Movement accommodates two completely different paths; one happens on the system requesting authorization (the CLI) and the opposite happens in a browser. The browser move path, whereby a tool code is sure to the session within the browser, happens as a parallel path half within the system move path.


Implementing the OAuth Gadget Movement

Now we’ll take a look at what the above sequence diagram seems like when it’s applied.

The inner CLI instrument at Rockset is known as rsctl and is written in go. Step one is to provoke the system move to get a JWT entry token.

$ rsctl login
Trying to robotically open the SSO authorization web page in your default browser.
If the browser doesn't open otherwise you want to use a unique system to authorize this request, open the next URL:


Then enter the code:

Efficiently logged in!

In case you are utilizing the CLI after logging in to a different laptop, e.g. ssh:ing to a Linux server, and you employ macOS, you’ll be able to configure iTerm to robotically open the hyperlink utilizing a “Run command” set off.

The web page that the hyperlink takes you to seems like this:

Device Confirmation

After getting confirmed that the “person code” is appropriate (matches with what the CLI exhibits), and also you click on “Affirm”, it’s going to take you thru the traditional OAuth2 login process (which in our case requires a username, password and {hardware} token).

As soon as the authentication is accomplished, you may be redirected and offered with a dialog just like the one under, and you’ll shut the browser window.

Device Confirmation

The CLI has now acquired a jwt entry token which is legitimate for a variety of hours and is used to authenticate by way of inner providers. The token may be cached on disk and reused between CLI invocations during its lifetime.

Whenever you situation a brand new rsctl command, it’s going to learn the cached Entry Token from disk, and use it to authenticate with the inner APIs.

Underneath the Hood

We’ve got applied and open sourced a go module to carry out the system authorization move (github.com/rockset/device-authorization). It helps each Auth0 and Okta as OAuth suppliers.

Pattern Code

The next code is accessible within the instance listing within the git repository.

Embedded content material: https://gist.github.com/pmenglund/5ed2708cdb88b6a6982258aed59a0899

We now have a JWT token, which can be utilized to authenticate REST calls by setting the Authorization header to Bearer: <jwt entry token>

Embedded content material: https://gist.github.com/pmenglund/b2ac7bb15ce25755a69573f5a063cb14

It’s now as much as the receiving finish to validate the bearer token, which may be accomplished utilizing an AWS ALB with OIDC authentication or a supplier particular API from the API server.

Offline Validation

An alternative choice for entry token validation is “offline validation”. In offline validation, the API server will get the general public key used to signal the JWT token from the supplier (and caches the general public key) and performs the validation within the API server, as an alternative of creating a validation request to the supplier.

Residual Danger

One factor this doesn’t defend towards is an attacker with a foothold on the pc that executes the CLI. They will simply wait till the person has accomplished the authentication, and they’re going to then be capable of act because the person during the entry token.

To mitigate this threat, you’ll be able to require a one time password (OTP), e.g. a Yubikey, each time the person performs a privileged motion.

$ rsctl delete useful resource foobar
please enter yubikey OTP: ccccccvfbbcddjtuehgnfrbtublkuufbgeebklrubkhf
useful resource foobar deleted

Closing Ideas

On this weblog, now we have proven how we constructed and open-sourced a go module to safe the Command Line Interface (CLI) utilizing an OAuth2 system authorization move that helps each Auth0 and Okta SSO suppliers. You possibly can add this go module to your inner instruments and cut back inner safety threats.

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