Neos Backend 2FA

Extend the Neos backend login to support second factors. At the moment we only support TOTP tokens.

Support for WebAuthn is planed!

What this package does

Screen.Recording.2022-02-08.at.17.07.59.mov

This package allows all users to register their personal TOTP token (Authenticator App). As an Administrator you are able to delete those token for the users again, in case they locked them self out.

Settings

Enforce 2FA

To enforce the setup and usage of 2FA you can add the following to your Settings.yaml.

Sandstorm:
    NeosTwoFactorAuthentication:
        # enforce 2FA for all users
        enforceTwoFactorAuthentication: true

With this setting, no user can login into the CMS without setting up a second factor first.

Issuer Naming

To override the default sitename as issuer label, you can define one via the configuration settings:

Sandstorm:
    NeosTwoFactorAuthentication:
        # (optional) if set this will be used as a naming convention for the TOTP. If empty the Site name will be used
        issuerName: ''

Tested 2FA apps

Thx to @Sebobo @Benjamin-K for creating a list of supported and testet apps!

iOS:

• Google Authenticator (used for development) ✅
• Authy ✅
• Microsoft Authenticator ✅
• 1Password ✅

Android:

• Google Authenticator ✅
• Microsoft Authenticator ✅
• Authy ✅

How we did it

• We introduced a new middleware SecondFactorMiddleware which handles 2FA on a Neos Session basis.
  • This is an overview of the checks the SecondFactorMiddleware does for any request:

                            ┌─────────────────────────────┐
                            │           Request           │
                            └─────────────────────────────┘
                                           ▼
                                ... middleware chain ...
                                           ▼
                            ┌─────────────────────────────┐
                            │  SecurityEndpointMiddleware │
                            └─────────────────────────────┘
                                           ▼
            ┌───────────────────────────────────────────────────────────────────┐
            │                     SecondFactorMiddleware                        │
            │                                                                   │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 1. Skip, if no authentication tokens are present, because   │  │
            │  │    we're not on a secured route.                            │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 2. Skip, if 'Neos.Backend:Backend' authentication token not │  │
            │  │    present, because we only support second factors for Neos │  │
            │  │    backend.                                                 │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 3. Skip, if 'Neos.Backend:Backend' authentication token is  │  │
            │  │    not authenticated, because we need to be authenticated   │  │
            │  │    with the authentication provider of                      │  │
            │  │    'Neos.Backend:Backend' first.                            │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 4. Skip, if second factor is not set up for account and not │  │
            │  │    enforced via settings.                                   │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 5. Skip, if second factor is already authenticated.         │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 6. Redirect to 2FA login, if second factor is set up for    │  │
            │  │    account but not authenticated.                           │  │
            │  │    Skip, if already on 2FA login route.                     │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ 7. Redirect to 2FA setup, if second factor is not set up for│  │
            │  │    account but is enforced by system.                       │  │
            │  │    Skip, if already on 2FA setup route.                     │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            │  ┌─────────────────────────────────────────────────────────────┐  │
            │  │ X. Throw an error, because any check before should have     │  │
            │  │    succeeded.                                               │  │
            │  └─────────────────────────────────────────────────────────────┘  │
            └───────────────────────────────────────────────────────────────────┘
                                              ▼
                                     ... middlewares ...
     
    

When updating Neos, those part will likely crash:

• the login screen for the second factor is a hard copy of the login screen from the Neos.Neos package
  • just replaced the username/password form with the form for the second factor
  • maybe has to be replaced when neos gets updated
• hopefully the rest of this package is solid enough to survive the next mayor Neos versions ;)

Why not ...?

Enhance the UsernamePassword authentication token

This actually has been the approach up until version 1.0.5.

One issue with this is the fact, that we want the user to be logged in with that token via the PersistedUsernamePasswordProvider, but at the same time to not be logged in with that token as long as 2FA is not authenticated as well. We found it hard to find a secure way to model the 2FA setup solution when 2FA is enforced, but the user does not have a second factor enabled, yet.

The middleware approach makes a clear distinction between "Logging in" and "Second Factor Authentication", while still being session based and unable to bypass.

Set the authenticationStrategy to allTokens

The AuthenticationProviderManager requires to authorize all tokens at the same time otherwise, it will throw an Exception (see AuthenticationProviderManager Line 181

if ($this->authenticationStrategy === Context::AUTHENTICATE_ALL_TOKENS) {
    throw new AuthenticationRequiredException('Could not authenticate all tokens, but authenticationStrategy was set to "all".', 1222203912);
}

)

This leads to an error where the AuthenticationProviderManager throws exceptions before the user is able to enter any credentials. The SecurityEntryPointMiddleware catches those exceptions and redirects to the Neos Backend Login, which causes the same exception again. We get caught in an endless redirect.

The Neos Flow Security Documentation suggests how to implement a multi-factor-authentication, but this method seems like it was never tested. At the moment of writing it seems like the authenticationStrategy: allTokens flag is broken and not usable.