multi_factor_auth.diviner

@title User Guide: Multi-Factor Authentication
@group userguide

Explains how multi-factor authentication works in Phabricator.

Overview
========

Multi-factor authentication allows you to add additional credentials to your
account to make it more secure.

Once multi-factor authentication is configured on your account, you'll usually
use your mobile phone to provide an authorization code or an extra confirmation
when you try to log in to a new session or take certain actions (like changing
your password).

Requiring you to prove you're really you by asking for something you know (your
password) //and// something you have (your mobile phone) makes it much harder
for attackers to access your account. The phone is an additional "factor" which
protects your account from attacks.


How Multi-Factor Authentication Works
=====================================

If you've configured multi-factor authentication and try to log in to your
account or take certain sensitive actions (like changing your password),
you'll be stopped and asked to enter additional credentials.

Usually, this means you'll receive an SMS with a authorization code on your
phone, or you'll open an app on your phone which will show you a authorization
code or ask you to confirm the action. If you're given a authorization code,
you'll enter it into Phabricator.

If you're logging in, Phabricator will log you in after you enter the code.

If you're taking a sensitive action, Phabricator will sometimes put your
account in "high security" mode for a few minutes. In this mode, you can take
sensitive actions like changing passwords or SSH keys freely, without
entering any more credentials.

You can explicitly leave high security once you're done performing account
management, or your account will naturally return to normal security after a
short period of time.

While your account is in high security, you'll see a notification on screen
with instructions for returning to normal security.


Configuring Multi-Factor Authentication
=======================================

To manage authentication factors for your account, go to
{nav Settings > Multi-Factor Auth}. You can use this control panel to add
or remove authentication factors from your account.

You can also rename a factor by clicking the name. This can help you identify
factors if you have several similar factors attached to your account.

For a description of the available factors, see the next few sections.


Factor: Mobile Phone App (TOTP)
===============================

TOTP stands for "Time-based One-Time Password". This factor operates by having
you enter authorization codes from your mobile phone into Phabricator. The codes
change every 30 seconds, so you will need to have your phone with you in order
to enter them.

To use this factor, you'll download an application onto your smartphone which
can compute these codes. Two applications which work well are **Authy** and
**Google Authenticator**. These applications are free, and you can find and
download them from the appropriate store on your device.

Your company may have a preferred application, or may use some other
application, so check any in-house documentation for details. In general, any
TOTP application should work properly.

After you've downloaded the application onto your phone, use the Phabricator
settings panel to add a factor to your account. You'll be prompted to scan a
QR code, and then read an authorization code from your phone and type it into
Phabricator.

Later, when you need to authenticate, you'll follow this same process: launch
the application, read the authorization code, and type it into Phabricator.
This will prove you have your phone.

Don't lose your phone! You'll need it to log into Phabricator in the future.


Factor: SMS
===========

This factor operates by texting you a short authorization code when you try to
log in or perform a sensitive action.

To use SMS, first add your phone number in {nav Settings > Contact Numbers}.
Once a primary contact number is configured on your account, you'll be able
to add an SMS factor.

To enroll in SMS, you'll be sent a confirmation code to make sure your contact
number is correct and SMS is being delivered properly. Enter it when prompted.

When you're asked to confirm your identity in the future, you'll be texted
an authorization code to enter into the prompt.

(WARNING) SMS is a very weak factor and can be compromised or intercepted. For
details, see: <https://phurl.io/u/sms>.


Factor: Duo
===========

This factor supports integration with [[ https://duo.com/ | Duo Security ]], a
third-party authentication service popular with enterprises that have a lot of
policies to enforce.

To use Duo, you'll install the Duo application on your phone. When you try
to take a sensitive action, you'll be asked to confirm it in the application.


Administration: Configuration
=============================

New Phabricator installs start without any multi-factor providers enabled.
Users won't be able to add new factors until you set up multi-factor
authentication by configuring at least one provider.

Configure new providers in {nav Auth > Multi-Factor}.

Providers may be in these states:

  - **Active**: Users may add new factors. Users will be prompted to respond
    to challenges from these providers when they take a sensitive action.
  - **Deprecated**: Users may not add new factors, but they will still be
    asked to respond to challenges from exising factors.
  - **Disabled**: Users may not add new factors, and existing factors will
    not be used. If MFA is required and a user only has disabled factors,
    they will be forced to add a new factor.

If you want to change factor types for your organization, the process will
normally look something like this:

  - Configure and test a new provider.
  - Deprecate the old provider.
  - Notify users that the old provider is deprecated and that they should move
    to the new provider at their convenience, but before some upcoming
    deadline.
  - Once the deadline arrives, disable the old provider.


Administration: Requiring MFA
=============================

As an administrator, you can require all users to add MFA to their accounts by
setting the `security.require-multi-factor-auth` option in Config.


Administration: Recovering from Lost Factors
============================================

If a user has lost a factor associated with their account (for example, their
phone has been lost or damaged), an administrator with host access can strip
the factor off their account so that they can log in without it.

IMPORTANT: Before stripping factors from a user account, be absolutely certain
that the user is who they claim to be!

It is important to verify the user is who they claim they are before stripping
factors because an attacker might pretend to be a user who has lost their phone
in order to bypass multi-factor authentication. It is much easier for a typical
attacker to spoof an email with a sad story in it than it is for a typical
attacker to gain access to a mobile phone.

A good way to verify user identity is to meet them in person and have them
solemnly swear an oath that they lost their phone and are very sorry and
definitely won't do it again. You can also work out a secret handshake in
advance and require them to perform it. But no matter what you do, be certain
the user (not an attacker //pretending// to be the user) is really the one
making the request before stripping factors.

After verifying identity, administrators with host access can strip
authentication factors from user accounts using the `bin/auth strip` command.
For example, to strip all factors from the account of a user who has lost
their phone, run this command:

```lang=console
# Strip all factors from a given user account.
phabricator/ $ ./bin/auth strip --user <username> --all-types
```

You can run `bin/auth help strip` for more detail and all available flags and
arguments.

This command can selectively strip factors by factor type. You can use
`bin/auth list-factors` to get a list of available factor types.

```lang=console
# Show supported factor types.
phabricator/ $ ./bin/auth list-factors
```

Once you've identified the factor types you want to strip, you can strip
matching factors by using the `--type` flag to specify one or more factor
types:

```lang=console
# Strip all SMS and TOTP factors for a user.
phabricator/ $ ./bin/auth strip --user <username> --type sms --type totp
```

The `bin/auth strip` command can also selectively strip factors for certain
providers. This is more granular than stripping all factors of a given type.
You can use `bin/auth list-mfa-providers` to get a list of providers.

Once you have a provider PHID, use `--provider` to select factors to strip:

```lang=console
# Strip all factors for a particular provider.
phabricator/ $ ./bin/auth strip --user <username> --provider <providerPHID>
```