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)

  • Range of attempts: number of additional intervals to test (default: 1)

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

  • 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.

Attention

If you want to use a custom rule for “activation” and want to keep self-registration, you must include this in your rule that $_2fDevices =~ /"type":\s*"TOTP"/s is set, else TOTP will be required even if users are not registered. This is automatically done when “activation” is simply set to “on”.

Danger

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

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

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"}, ...]