# TOTP 2nd Factor Authentication

Time based One Time Password (TOTP) is an algorithm that computes a one-time password from a shared secret key and the current time. This is currently use by Google Authenticator or FreeOTP.

LLNG can propose users to register this kind of software to increase authentication level.

Tip

Note that it’s a second factor, not an authentication module. Users are authenticated both by login form and TOTP.

## Prerequisites and dependencies

This feature uses libconvert-base32-perl. Before enable it, on Debian you must install libconvert-base32-perl by :

    apt update
    apt install libconvert-base32-perl
    apt install libdigest-hmac-perl

Or from CPAN repository :

    cpanm Convert::Base32

## Configuration

In the manager (advanced parameters), you just have to enable it:

- Activation: set it to “on”

- Self registration: set it to “on” if users are authorized to generate themselves a TOTP secret

- Allow users to remove TOTP: If enabled, users can unregister TOTP

- Issuer name (Optional): default to portal hostname

- Interval: interval for TOTP algorithm (default: 30)

Warning

Many mobile applications only support the default value

- Range of attempts: number of additional intervals to test (default: 1). Use this settings if your server and phone clocks are not perfectly in sync, at the cost of weaker security.

Note

Range is tested backward and forward to prevent positive or negative clock drift.

- Number of digits: number of digit by codes (default: 6)

Warning

Many mobile applications only support the default value

- Authentication level: you can overwrite here auth level for TOTP registered users. Leave it blank keeps auth level provided by first authentication module (default: 2 for user/password based modules). It is recommended to set an higher value here if you want to give access to some apps only for enrolled users

- Label (Optional): label that should be displayed to the user on the choice screen

- Logo (Optional): logo file (in static/<skin> directory)

- Lifetime (Optional): Unlimited by default. Set a Time To Live in seconds. TTL is checked at each login process if set. If TTL is expired, relative TOTP is removed.

- Encrypt TOTP secrets: By default, the TOTP secret key is stored in the persistent session database in cleartext. Set this option to encrypt all newly-generated secrets. More details below

- Logo (Optional): logo file (in static/<skin> directory)

- Label (Optional): label that should be displayed to the user on the choice screen

Attention

If you want to use a custom rule for “activation” and want to keep self-registration, you must add the following condition to the custom activation rule:

    and has2f('TOTP')

Without this condition, TOTP will be asked even for users who didn’t register one. This is automatically done when “activation” is simply set to “on”.

## Enrollment

If you’ve enabled self registration, users can register their keys by using https://portal/2fregisters

## Assistance

If a user loses its key, you can remove it from manager Second Factor module.// // To enable manager Second Factor Administration Module, set `enabledModules` key in your `lemonldap-ng.ini` file :// //

    [portal]
    enabledModules = conf, sessions, notifications, 2ndFA

## Encryption of TOTP secrets

During registration of a TOTP device, a secret key is exchanged between the mobile device and the server, generally through the use of a QR-Code. Once the exchange is done, secret keys must never leave the device or the server.

Administrators may want to protect TOTP secrets by encrypting them in the persistent session database, in order to prevent them from leaking through backups or unauthorized database access.

Setting the Encrypt TOTP secrets option will automatically encrypt newly generated secrets.

The Encrypt TOTP secrets options only affects NEW secrets, meaning that:

- A cleartext TOTP secret will be accepted even if the option is on

- An already encrypted TOTP secret will be accepted even if the option if off

The `encryptTotpSecrets` script can be used to encrypt previously registered TOTP secrets so that they can be protected as well.

### Encryption key

By default, the key used for encryption is the global one, set in

General Parameters » Advanced Parameters » Security » Key

However, if you store your configuration and persistent sessions in the same database, this defeats the point of encryption entirely.

It is recommended to set the TOTP encryption key in `/etc/lemonldap-ng/lemonldap-ng.ini` instead:

    [all]
    totp2fKey=changeme

## Developer corner

If you have another TOTP registration interface, you have to set these keys in Second Factor Devices array (JSON) in your user-database. Then map it to the _2fDevices attribute (see exported variables):

    [{"name" : "MyTOTP" , "type" : "TOTP" , "_secret" : "########" , "epoch":"1524078936"}, ...]