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How to write an Authentication Backend ?

:!: The authentication backends developed as described on this page would only work at DokuWiki releases 2012-10-13 “Adora Belle” and older.

See Auth Plugins for development documentation about the new authentications plugins

Please UPDATE or REWRITE old backend to the new Auth Plugins (the old Auth Backends are not supported anymore)

DokuWiki's authentication system is highly modular and can, generally speaking, authenticate using anything that is accessible from PHP.

If none of the provided auth backends does what you want, you can simply create your own. Backends are:

  • stored in the inc/auth/ folder
  • need to be named <backend>.class.php where <backend> is the name of your authentication backend.
  • specify a class named auth_<backend>.
  • Your class should either extend one of the existing backends or the auth_basic class defined in inc/auth/basic.class.php.

In your class you need to override a few methods and set some public fields from the base class. Some descriptions follow, but for the doing the implementation you need to have a look at base class' comments!

If you write a new backend be sure to share your code with the community!

Fields to set

  • $success
    This simple boolean needs to be set to true in your constructor if your auth module was correctly initialized. Use this to notify the frontend if anything went wrong by setting it to false.
  • $cando
    The $cando field is an associative array of booleans. You need to set the array fields to true for all functions your backend provides. Here is a list of keys in $cando and their meaning:
addUser can Users be created?
delUser can Users be deleted?
modLogin can login names be changed?
modPass can passwords be changed?
modName can real names be changed?
modMail can emails be changed?
modGroups can groups be changed?
getUsers can a (filtered) list of users be retrieved?
getUserCount can the number of users be retrieved?
getGroups can a list of available groups be retrieved?
external does the module do external auth checking?
logoff has the module some special logoff method?

Required Methods

Only a few functions need to be implemented. But the more you do the more the frontend will be able to do.

See inc/auth/basic.class.php for the methods' arguments and return values.

  • __construct()
    Well your class should have a constructor of course :-) Set the fields $success and $cando mentioned above here.
  • checkPass($user, $pass)
    This function need to check if the given userid $user exists and the given plaintext password $pass is correct.
  • getUserData($user)
    Used to return user information like email address and real name, for the requested userid $user
    Return false or an array with at least the keys
        'name' => string,
        'mail' => string,
        'grps' => array()

Optional Methods

All these methods are optional and will only be called if the appropriate $cando fields are set

  • trustExternal() (replaces DokuWiki authentication functions)
    If $cando['external'] is true, this function is used to authenticate a user – all other DokuWiki internals will not be used for authenticating. The function can be used to authenticate against third party cookies or Apache auth mechanisms and replaces the auth_login() function from inc/auth.php.

    If this function is implemented you may omit all other functions from your module. You only really needs a constructor and this trustExternal() function, and it strong recommended to have getUserData() so DokuWiki can display your users nicely and logoff() to permit DokuWiki to communicate the logoff to your backend. The other functions are only needed when you like that some internals of DokuWiki interact with your backend. Search the source code or browse on to check out the connections.

    Have a look at the punbb backend for an example usage of this function. According to the example method in the parent auth_basic class the trustExternal() function has to set the global variables: $USERINFO, $SERVER and _SESSION[DOKU_COOKIE] for the indicated fields.

    The implementation depends very much on your backend, here are some often used parts indicated as example. Look also for other implementations, when it doesn't fit your requirements.
    function trustExternal($user, $pass, $sticky=false) {
        global $USERINFO;
        // someone used the login form
            //situation: there are user credentials, lets check them
            if( ...try to authenticate again your backend...)
                // here you can handle additional post login actions 
                // for your backend
                //invalid credentials - log off
                auth_logoff(); // needs implementation of logOff() method
                return false;
        //situation: no login form used or logged in successful 
        // check where if there is a logged in user e.g from session,
        // $_SERVER or what your auth backend supplies...
        if( ...check here if there is a logged in user...) {
            $USERINFO['name'] = string
            $USERINFO['mail'] = string
            $USERINFO['grps'] = array()
            $_SERVER['REMOTE_USER']                = $user; //userid
            $_SESSION[DOKU_COOKIE]['auth']['user'] = $user; //userid
            $_SESSION[DOKU_COOKIE]['auth']['info'] = $USERINFO;
            return true;
            //when needed, logoff explicitly.

    For a description of the $USERINFO variables see the documentation of the getUserData() function. Do not forget to add global $USERINFO to the start of this function, to make the variable accessible.

    Another thing to keep in mind if you're implementing Single Sign On based on a cookie, is that if you want to be able to use DokuWiki's login form when SSO cookie is not present, you need to set that cookie once you verify the credentials, so on next page load you can authenticate based on that SSO cookie as $user and $pass variables will be empty since login form is not submitted. In punbb this is done with pun_setcookie() function call.

    Dokuwiki will not show any message if the login failed, therefore this method shall show some information using msg().

    See also this working example of trustExternal().

    Some backends using this function are: punbb, cas, cosign, plaincas, django, extdjango, gforge, http version of ggauth, keeyaiwp, mod_auth_tkt, ssp

  • logOff() (only when required/possible)
    Run in addition to the usual logoff. Useful with trustExternal() to initiate actions for the external backend e.g. use it to clear cookies or similar actions.
  • isCaseSensitive() (optional)
    When your backend is caseinsensitive, override it with a method that returns false.
  • cleanUser($user) (optional)
    Applied when username is given to and return from backend. Enforce here also username restrictions.
  • cleanGroup($group) (optional)
    Applied when groupname is given to and return from backend. Enforce here also groupname restrictions. Groupnames are to be passed without a leading '@' here.
  • useSessionCache($user) (only when required)
    DokuWiki caches user info for a timespan. This function check expiration of this caching.


  • The authentication backend does currently not use method visibility (available since PHP 5), therefore all methods are expected to be public
  • doku.php throws E_NOTICE errors due to undefined $_REQUEST-variables. Avoid setting the error reporting to E_ALL in the authenticiation backend or the classes used by the backend.
  • Your authentication backend may be called from different working directories (e.g. dokuwiki root or /inc/auth). Keep this in mind if your backend includes or loades other files.
  • Dokuwiki starts a session prior to using the authentication backend. If your framework uses specific session settings (e.g. another session path) use session_destroy() in the backend constructor and start your own session then (Note: not fully tested for side effects, yet!).
  • Your backend (or its framework) cannot use __autoload to include further classes, those classes must be loaded manually via require()
devel/authentication_backends.txt · Last modified: 2021-09-09 12:52 by Klap-in

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