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How to use WebAuthn MFA with gem CLI.

Multi-factor authentication (MFA) using WebAuthn works by using a removable hardware token or touch biometric / facial biometric capabilities built into your phone or computer. This is distinct from MFA based on typing or copying a code generated by an authentication app or password manager, called OTP. For OTP MFA see “Using OTP multi-factor authentication in command line”.

When you have enabled WebAuthn MFA, we will ask you to perform authentication on certain commands based on your authentication level.

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[snip of API key setup]

You have enabled multi-factor authentication.
Please visit http://localhost:3000/webauthn_verification/<random>?port=<port>
to authenticate via security device. If you can't verify using WebAuthn but
have OTP enabled, you can re-run the gem signin command with the `--otp [your_code]`

Depending on your terminal program, you may be able to click, command-click or control-click on the link to open it in your default browser. Otherwise you will need to copy and paste the link into a new tab.

A webpage titled “Authenticate with Security Device” appears. Click “Authenticate”. Your browser will show a popup asking you to use a Passkey or other authentication device (the exact popup will vary according to the browser).

Once you have authenticated using your WebAuthn device device, you will see a “Success” page. At this point you can close your browser tab and return to the command line, which will say:

You are verified with a security device. You may close the browser window.
Signed in with API key: <your API key name>