# Two-Factor Authentication

Two-factor Authentication (2FA) provides an additional level of security to your
GitLab account. Once enabled, in addition to supplying your username and
password to login, you'll be prompted for a code generated by an application on
your phone.

By enabling 2FA, the only way someone other than you can log into your account
is to know your username and password *and* have access to your phone.

## Overview

> **Note:**
When you enable 2FA, don't forget to back up your recovery codes.

In addition to a phone application, GitLab supports U2F (universal 2nd factor) devices as
the second factor of authentication. Once enabled, in addition to supplying your username and
password to login, you'll be prompted to activate your U2F device (usually by pressing
a button on it), and it will perform secure authentication on your behalf.

The U2F workflow is only supported by Google Chrome at this point, so we _strongly_ recommend
that you set up both methods of two-factor authentication, so you can still access your account
from other browsers.

## Enabling 2FA

There are two ways to enable two-factor authentication: via a mobile application
or a U2F device.

### Enable 2FA via mobile application

**In GitLab:**

1. Log in to your GitLab account.
1. Go to your **Profile Settings**.
1. Go to **Account**.
1. Click **Enable Two-factor Authentication**.

![Two-factor setup](img/2fa.png)

**On your phone:**

1. Install a compatible application. We recommend [Google Authenticator]
\(proprietary\) or [FreeOTP] \(open source\).
1. In the application, add a new entry in one of two ways:
    * Scan the code with your phone's camera to add the entry automatically.
    * Enter the details provided to add the entry manually.

**In GitLab:**

1. Enter the six-digit pin number from the entry on your phone into the **Pin
   code** field.
1. Click **Submit**.

If the pin you entered was correct, you'll see a message indicating that
Two-Factor Authentication has been enabled, and you'll be presented with a list
of recovery codes.

### Enable 2FA via U2F device

> **Notes:**
- GitLab officially only supports [Yubikey] U2F devices.
- Support for U2F devices was added in GitLab 8.8.

**In GitLab:**

1. Log in to your GitLab account.
1. Go to your **Profile Settings**.
1. Go to **Account**.
1. Click **Enable Two-Factor Authentication**.
1. Plug in your U2F device.
1. Click on **Setup New U2F Device**.
1. A light will start blinking on your device. Activate it by pressing its button.

You will see a message indicating that your device was successfully set up.
Click on **Register U2F Device** to complete the process.

![Two-Factor U2F Setup](img/2fa_u2f_register.png)

## Recovery Codes

> **Note:**
Recovery codes are not generated for U2F devices.

Should you ever lose access to your phone, you can use one of the ten provided
backup codes to login to your account. We suggest copying or printing them for
storage in a safe place. **Each code can be used only once** to log in to your
account.

If you lose the recovery codes or just want to generate new ones, you can do so
from the **Profile settings ➔ Account** page where you first enabled 2FA.

## Logging in with 2FA Enabled

Logging in with 2FA enabled is only slightly different than a normal login.
Enter your username and password credentials as you normally would, and you'll
be presented with a second prompt, depending on which type of 2FA you've enabled.

### Log in via mobile application

Enter the pin from your phone's application or a recovery code to log in.

![Two-Factor Authentication on sign in via OTP](img/2fa_auth.png)

### Log in via U2F device

1. Click **Login via U2F Device**
1. A light will start blinking on your device. Activate it by pressing its button.

You will see a message indicating that your device responded to the authentication request.
Click on **Authenticate via U2F Device** to complete the process.

![Two-Factor Authentication on sign in via U2F device](img/2fa_u2f_authenticate.png)

## Disabling 2FA

1. Log in to your GitLab account.
1. Go to your **Profile Settings**.
1. Go to **Account**.
1. Click **Disable**, under **Two-Factor Authentication**.

This will clear all your two-factor authentication registrations, including mobile
applications and U2F devices.

## Personal access tokens

When 2FA is enabled, you can no longer use your normal account password to
authenticate with Git over HTTPS on the command line or when using
[GitLab's API][api], you must use a [personal access token][pat] instead.

## Recovery options

To disable two-factor authentication on your account (for example, if you
have lost your code generation device) you can:

* [Use a saved recovery code](#use-a-saved-recovery-code)
* [Generate new recovery codes using SSH](#generate-new-recovery-codes-using-ssh)
* [Ask a GitLab administrator to disable two-factor authentication on your account](#ask-a-gitlab-administrator-to-disable-two-factor-authentication-on-your-account)

### Use a saved recovery code

Enabling two-factor authentication for your account generated several recovery
codes. If you saved these codes, you can use one of them to sign in.

To use a recovery code, enter your username/email and password on the GitLab
sign-in page. When prompted for a two-factor code, enter the recovery code.

>**Note:**
Once you use a recovery code, you cannot re-use it. You can still use the other
recovery codes you saved.

### Generate new recovery codes using SSH

Users often forget to save their recovery codes when enabling two-factor
authentication. If an SSH key is added to your GitLab account, you can generate
a new set of recovery codes with SSH.

1. Run `ssh git@gitlab.example.com 2fa_recovery_codes`.
2. You are prompted to confirm that you want to generate new codes. Continuing this process invalidates previously saved codes.
    ```
    bash
    $ ssh git@gitlab.example.com 2fa_recovery_codes
    Are you sure you want to generate new two-factor recovery codes?
    Any existing recovery codes you saved will be invalidated. (yes/no)

    yes

    Your two-factor authentication recovery codes are:

    119135e5a3ebce8e
    11f6v2a498810dcd
    3924c7ab2089c902
    e79a3398bfe4f224
    34bd7b74adbc8861
    f061691d5107df1a
    169bf32a18e63e7f
    b510e7422e81c947
    20dbed24c5e74663
    df9d3b9403b9c9f0

    During sign in, use one of the codes above when prompted for your
    two-factor code. Then, visit your Profile Settings and add a new device
    so you do not lose access to your account again.
    ```

3. Go to the GitLab sign-in page and enter your username/email and password.
   When prompted for a two-factor code, enter one of the recovery codes obtained
   from the command-line output.

>**Note:**
After signing in, visit your **Profile settings > Account**  immediately to set
up two-factor authentication with a new device.

### Ask a GitLab administrator to disable two-factor authentication on your account

If you cannot use a saved recovery code or generate new recovery codes, ask a
GitLab global administrator to disable two-factor authentication for your
account. This will temporarily leave your account in a less secure state.
Sign in and re-enable two-factor authentication as soon as possible.

## Note to GitLab administrators

- You need to take special care to that 2FA keeps working after
  [restoring a GitLab backup](../../../raketasks/backup_restore.md).
- To ensure 2FA authorizes correctly with TOTP server, you may want to ensure
  your GitLab server's time is synchronized via a service like NTP.  Otherwise,
  you may have cases where authorization always fails because of time differences.
- The GitLab U2F implementation does _not_ work when the GitLab instance is accessed from
  multiple hostnames, or FQDNs. Each U2F registration is linked to the _current hostname_ at
  the time of registration, and cannot be used for other hostnames/FQDNs.

    For example, if a user is trying to access a GitLab instance from `first.host.xyz` and `second.host.xyz`:

    - The user logs in via `first.host.xyz` and registers their U2F key.
    - The user logs out and attempts to log in via `first.host.xyz` - U2F authentication suceeds.
    - The user logs out and attempts to log in via `second.host.xyz` - U2F authentication fails, because
    the U2F key has only been registered on `first.host.xyz`.

[Google Authenticator]: https://support.google.com/accounts/answer/1066447?hl=en
[FreeOTP]: https://freeotp.github.io/
[YubiKey]: https://www.yubico.com/products/yubikey-hardware/
[api]: ../../../api/README.md
[pat]: ../personal_access_tokens.md
