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 to users to register this kind of software to increase authentication level.

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

Or from CPAN repository :

cpanm Convert::Base32


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

  • TOTP ⇒ Activation: set it to “on”
  • TOTP ⇒ Self registration: set it to “on” if users are authorized to generate themselves a TOTP secret
  • TOTP ⇒ 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 to users enrolled
  • TOTP ⇒ Issuer: default to portal hostname
  • TOTP ⇒ Interval: interval for TOTP algorithm (default: 30)
  • TOTP ⇒ Range: number of additional intervals to test (default: 1)
  • TOTP ⇒ Digits: number of digit by codes (default: 6)
  • TOTP ⇒ Display existing secret: display an already registered secret (default: disabled)
  • TOTP ⇒ Change existing secret: authorize a user to change its previoulsy registered TOTP secret
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”.


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


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 :

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"}, ...]