NAME
    Apache::AuthCookie - Perl Authentication and Authorization via cookies

SYNOPSIS
    Make sure your mod_perl is at least 1.24, with StackedHandlers,
    MethodHandlers, Authen, and Authz compiled in.

     # In httpd.conf or .htaccess:
     PerlModule Sample::AuthCookieHandler
     PerlSetVar WhatEverPath /
     PerlSetVar WhatEverLoginScript /login.pl

     # use to alter how "require" directives are matched. Can be "Any" or "All".
     # If its "Any", then you must only match Any of the "require" directives. If
     # its "All", then you must match All of the require directives. 
     #
     # Default: Any
     PerlSetVar WhatEverSatisfy Any
 
     # The following line is optional - it allows you to set the domain
     # scope of your cookie.  Default is the current domain.
     PerlSetVar WhatEverDomain .yourdomain.com

     # Use this to only send over a secure connection
     PerlSetVar WhatEverSecure 1

     # Usually documents are uncached - turn off here
     PerlSetVar WhatEverCache 1

     # Use this to make your cookies persistent (+2 hours here)
     PerlSetVar WhatEverExpires +2h

     # Use to make AuthCookie send a P3P header with the cookie
     # see http://www.w3.org/P3P/ for details about what the value 
     # of this should be
     PerlSetVar WhatEverP3P "CP=\"...\""

     # These documents require user to be logged in.
     <Location /protected>
      AuthType Sample::AuthCookieHandler
      AuthName WhatEver
      PerlAuthenHandler Sample::AuthCookieHandler->authenticate
      PerlAuthzHandler Sample::AuthCookieHandler->authorize
      require valid-user
     </Location>

     # These documents don't require logging in, but allow it.
     <FilesMatch "\.ok$">
      AuthType Sample::AuthCookieHandler
      AuthName WhatEver
      PerlFixupHandler Sample::AuthCookieHandler->recognize_user
     </FilesMatch>

     # This is the action of the login.pl script above.
     <Files LOGIN>
      AuthType Sample::AuthCookieHandler
      AuthName WhatEver
      SetHandler perl-script
      PerlHandler Sample::AuthCookieHandler->login
     </Files>

DESCRIPTION
    Apache::AuthCookie allows you to intercept a user's first unauthenticated
    access to a protected document. The user will be presented with a custom
    form where they can enter authentication credentials. The credentials are
    posted to the server where AuthCookie verifies them and returns a session
    key.

    The session key is returned to the user's browser as a cookie. As a cookie,
    the browser will pass the session key on every subsequent accesses.
    AuthCookie will verify the session key and re-authenticate the user.

    All you have to do is write a custom module that inherits from AuthCookie.
    Your module is a class which implements two methods:

    "authen_cred()"
        Verify the user-supplied credentials and return a session key. The
        session key can be any string - often you'll use some string containing
        username, timeout info, and any other information you need to determine
        access to documents, and append a one-way hash of those values together
        with some secret key.

    "authen_ses_key()"
        Verify the session key (previously generated by "authen_cred()",
        possibly during a previous request) and return the user ID. This user ID
        will be fed to "$r->connection->user()" to set Apache's idea of who's
        logged in.

    By using AuthCookie versus Apache's built-in AuthBasic you can design your
    own authentication system. There are several benefits.

    1.  The client doesn't *have* to pass the user credentials on every
        subsequent access. If you're using passwords, this means that the
        password can be sent on the first request only, and subsequent requests
        don't need to send this (potentially sensitive) information. This is
        known as "ticket-based" authentication.

    2.  When you determine that the client should stop using the
        credentials/session key, the server can tell the client to delete the
        cookie. Letting users "log out" is a notoriously impossible-to-solve
        problem of AuthBasic.

    3.  AuthBasic dialog boxes are ugly. You can design your own HTML login
        forms when you use AuthCookie.

    4.  You can specify the domain of a cookie using PerlSetVar commands. For
        instance, if your AuthName is "WhatEver", you can put the command

         PerlSetVar WhatEverDomain .yourhost.com

        into your server setup file and your access cookies will span all hosts
        ending in ".yourhost.com".

    This is the flow of the authentication handler, less the details of the
    redirects. Two REDIRECT's are used to keep the client from displaying the
    user's credentials in the Location field. They don't really change
    AuthCookie's model, but they do add another round-trip request to the
    client.

     (-----------------------)     +---------------------------------+
     ( Request a protected   )     | AuthCookie sets custom error    |
     ( page, but user hasn't )---->| document and returns            |
     ( authenticated (no     )     | FORBIDDEN. Apache abandons      |      
     ( session key cookie)   )     | current request and creates sub |      
     (-----------------------)     | request for the error document. |<-+
                                   | Error document is a script that |  |
                                   | generates a form where the user |  |
                     return        | enters authentication           |  |
              ^------------------->| credentials (login & password). |  |
             / \      False        +---------------------------------+  |
            /   \                                   |                   |
           /     \                                  |                   |
          /       \                                 V                   |
         /         \               +---------------------------------+  |
        /   Pass    \              | User's client submits this form |  |
       /   user's    \             | to the LOGIN URL, which calls   |  |
       | credentials |<------------| AuthCookie->login().            |  |
       \     to      /             +---------------------------------+  |
        \authen_cred/                                                   |
         \ function/                                                    |
          \       /                                                     |
           \     /                                                      |
            \   /            +------------------------------------+     |
             \ /   return    | Authen cred returns a session      |  +--+
              V------------->| key which is opaque to AuthCookie.*|  |
                    True     +------------------------------------+  |
                                                  |                  |
                   +--------------------+         |      +---------------+
                   |                    |         |      | If we had a   |
                   V                    |         V      | cookie, add   |
      +----------------------------+  r |         ^      | a Set-Cookie  |
      | If we didn't have a session|  e |T       / \     | header to     |
      | key cookie, add a          |  t |r      /   \    | override the  |
      | Set-Cookie header with this|  u |u     /     \   | invalid cookie|
      | session key. Client then   |  r |e    /       \  +---------------+
      | returns session key with   |  n |    /  pass   \               ^    
      | successive requests        |    |   /  session  \              |
      +----------------------------+    |  /   key to    \    return   |
                   |                    +-| authen_ses_key|------------+
                   V                       \             /     False
      +-----------------------------------+ \           /
      | Tell Apache to set Expires header,|  \         /
      | set user to user ID returned by   |   \       /
      | authen_ses_key, set authentication|    \     /
      | to our type (e.g. AuthCookie).    |     \   /
      +-----------------------------------+      \ /
                                                  V
             (---------------------)              ^
             ( Request a protected )              |
             ( page, user has a    )--------------+
             ( session key cookie  )
             (---------------------)

     *  The session key that the client gets can be anything you want.  For
        example, encrypted information about the user, a hash of the
        username and password (similar in function to Digest
        authentication), or the user name and password in plain text
        (similar in function to HTTP Basic authentication).

        The only requirement is that the authen_ses_key function that you
        create must be able to determine if this session_key is valid and
        map it back to the originally authenticated user ID.

METHODS
    "Apache::AuthCookie" has several methods you should know about. Here is the
    documentation for each. =)

    * authenticate()
        This method is one you'll use in a server config file (httpd.conf,
        .htaccess, ...) as a PerlAuthenHandler. If the user provided a session
        key in a cookie, the "authen_ses_key()" method will get called to check
        whether the key is valid. If not, or if there is no key provided, we
        redirect to the login form.

    * authorize()
        This will step through the "require" directives you've given for
        protected documents and make sure the user passes muster. The "require
        valid-user" and "require user joey-jojo" directives are handled for you.
        You can implement custom directives, such as "require species hamster",
        by defining a method called "species()" in your subclass, which will
        then be called. The method will be called as "$r->species($r, $args)",
        where "$args" is everything on your "require" line after the word
        "hamster". The method should return OK on success and FORBIDDEN on
        failure.

        Currently users must satisfy ALL of the "require" directives. I have
        heard that other Apache modules let the user satisfy ANY of the
        "require" directives. I don't know which is correct, I haven't found any
        Apache docs on the matter. If you need one behavior or the other, be
        careful. I may change it if I discover that ANY is correct.

    * authen_cred()
        You must define this method yourself in your subclass of
        "Apache::AuthCookie". Its job is to create the session key that will be
        preserved in the user's cookie. The arguments passed to it are:

         sub authen_cred ($$\@) {
           my $self = shift;  # Package name (same as AuthName directive)
           my $r    = shift;  # Apache request object
           my @cred = @_;     # Credentials from login form

           ...blah blah blah, create a session key...
           return $session_key;
         }

        The only limitation on the session key is that you should be able to
        look at it later and determine the user's username. You are responsible
        for implementing your own session key format. A typical format is to
        make a string that contains the username, an expiration time, whatever
        else you need, and an MD5 hash of all that data together with a secret
        key. The hash will ensure that the user doesn't tamper with the session
        key. More info in the Eagle book.

    * authen_ses_key()
        You must define this method yourself in your subclass of
        Apache::AuthCookie. Its job is to look at a session key and determine
        whether it is valid. If so, it returns the username of the authenticated
        user.

         sub authen_ses_key ($$$) {
           my ($self, $r, $session_key) = @_;
           ...blah blah blah, check whether $session_key is valid...
           return $ok ? $username : undef;
         }

        Optionally, return an array of 2 or more items that will be passed to
        method custom_errors. It is the responsibility of this method to return
        the correct response to the main Apache module.

    * custom_errors($r,@_)
        Note: this interface is experimental.

        This method handles the server response when you wish to access the
        Apache custom_response method. Any suitable response can be used. this
        is particularly useful when implementing 'by directory' access control
        using the user authentication information. i.e.

                /restricted
                        /one            user is allowed access here
                        /two            not here
                        /three          AND here

        The authen_ses_key method would return a normal response when the user
        attempts to access 'one' or 'three' but return (NOT_FOUND, 'File not
        found') if an attempt was made to access subdirectory 'two'. Or, in the
        case of expired credentials, (AUTH_REQUIRED,'Your session has timed out,
        you must login again').

          example 'custom_errors'

          sub custom_errors {
            my ($self,$r,$CODE,$msg) = @_;
            # return custom message else use the server's standard message
            $r->custom_response($CODE, $msg) if $msg;
            return($CODE);
          }
          
          where CODE is a valid code from Apache::Constants

    * login()
        This method handles the submission of the login form. It will call the
        "authen_cred()" method, passing it "$r" and all the submitted data with
        names like ""credential_#"", where # is a number. These will be passed
        in a simple array, so the prototype is "$self->authen_cred($r,
        @credentials)". After calling "authen_cred()", we set the user's cookie
        and redirect to the URL contained in the ""destination"" submitted form
        field.

    * login_form()
        This method is responsible for displaying the login form. The default
        implementation will make an internal redirect and display the URL you
        specified with the "PerlSetVar WhatEverLoginForm" configuration
        directive. You can overwrite this method to provide your own mechanism.

    * logout()
        This is simply a convenience method that unsets the session key for you.
        You can call it in your logout scripts. Usually this looks like
        "$r->auth_type->logout($r);".

    * send_cookie($session_key)
        By default this method simply sends out the session key you give it. If
        you need to change the default behavior (perhaps to update a timestamp
        in the key) you can override this method.

    * recognize_user()
        If the user has provided a valid session key but the document isn't
        protected, this method will set "$r->connection->user" anyway. Use it as
        a PerlFixupHandler, unless you have a better idea.

    * key()
        This method will return the current session key, if any. This can be
        handy inside a method that implements a "require" directive check (like
        the "species" method discussed above) if you put any extra information
        like clearances or whatever into the session key.

UPGRADING FROM VERSION 1.4
    There are a few interface changes that you need to be aware of when
    migrating from version 1.x to 2.x. First, the authen() and authz() methods
    are now deprecated, replaced by the new authenticate() and authorize()
    methods. The old methods will go away in a couple versions, but are
    maintained intact in this version to ease the task of upgrading. The use of
    these methods is essentially the same, though.

    Second, when you change to the new method names (see previous paragraph),
    you must change the action of your login forms to the location /LOGIN (or
    whatever URL will call your module's login() method). You may also want to
    change their METHOD to POST instead of GET, since that's much safer and
    nicer to look at (but you can leave it as GET if you bloody well want to,
    for some god-unknown reason).

    Third, you must change your login forms (see the THE LOGIN SCRIPT entry
    elsewhere in this document below) to indicate how requests should be
    redirected after a successful login.

    Fourth, you might want to take advantage of the new "logout()" method,
    though you certainly don't have to.

EXAMPLE
    For an example of how to use Apache::AuthCookie, you may want to check out
    the test suite, which runs AuthCookie through a few of its paces. The
    documents are located in t/eg/, and you may want to peruse t/real.t to see
    the generated httpd.conf file (at the bottom of real.t) and check out what
    requests it's making of the server (at the top of real.t).

THE LOGIN SCRIPT
    You will need to create a login script (called login.pl above) that
    generates an HTML form for the user to fill out. You might generate the page
    using an Apache::Registry script, or an HTML::Mason component, or perhaps
    even using a static HTML page. It's usually useful to generate it
    dynamically so that you can define the 'destination' field correctly (see
    below).

    The following fields must be present in the form:

    1.  The ACTION of the form must be /LOGIN (or whatever you defined in your
        server configuration as handled by the ->login() method - see example in
        the SYNOPSIS section).

    2.  The various user input fields (username, passwords, etc.) must be named
        'credential_0', 'credential_1', etc. on the form. These will get passed
        to your authen_cred() method.

    3.  You must define a form field called 'destination' that tells AuthCookie
        where to redirect the request after successfully logging in. Typically
        this value is obtained from "$r->prev->uri". See the login.pl script in
        t/eg/.

    In addition, you might want your login page to be able to tell why the user
    is being asked to log in. In other words, if the user sent bad credentials,
    then it might be useful to display an error message saying that the given
    username or password are invalid. Also, it might be useful to determine the
    difference between a user that sent an invalid auth cookie, and a user that
    sent no auth cookie at all. To cope with these situations, AuthCookie will
    set "$r->subprocess_env('AuthCookieReason')" to one of the following values.

    *no_cookie*
        The user presented no cookie at all. Typically this means the user is
        trying to log in for the first time.

    *bad_cookie*
        The cookie the user presented is invalid. Typically this means that the
        user is not allowed access to the given page.

    *bad_credentials*
        The user tried to log in, but the credentials that were passed are
        invalid.

    You can examine this value in your login form by examining
    "$r->prev->subprocess_env('AuthCookieReason')" (because it's a sub-request).

    Of course, if you want to give more specific information about why access
    failed when a cookie is present, your "authen_ses_key()" method can set
    arbitrary entries in "$r->subprocess_env".

THE LOGOUT SCRIPT
    If you want to let users log themselves out (something that can't be done
    using Basic Auth), you need to create a logout script. For an example, see
    t/eg/logout.pl. Logout scripts may want to take advantage of AuthCookie's
    "logout()" method, which will set the proper cookie headers in order to
    clear the user's cookie. This usually looks like
    "$r->auth_type->logout($r);".

    Note that if you don't necessarily trust your users, you can't count on
    cookie deletion for logging out. You'll have to expire some server-side
    login information too. AuthCookie doesn't do this for you, you have to
    handle it yourself.

ABOUT SESSION KEYS
    Unlike the sample AuthCookieHandler, you have you verify the user's login
    and password in "authen_cred()", then you do something like:

        my $date = localtime;
        my $ses_key = MD5->hexhash(join(';', $date, $PID, $PAC));

    save "$ses_key" along with the user's login, and return "$ses_key".

    Now "authen_ses_key()" looks up the "$ses_key" passed to it and returns the
    saved login. I use Oracle to store the session key and retrieve it later,
    see the ToDo section below for some other ideas.

KNOWN LIMITATIONS
    If the first unauthenticated request is a POST, it will be changed to a GET
    after the user fills out the login forms, and POSTed data will be lost.

  TO DO

    *   There ought to be a way to solve the POST problem in the LIMITATIONS
        section. It involves being able to re-insert the POSTed content into the
        request stream after the user authenticates.

        It might be nice if the logout method could accept some parameters that
        could make it easy to redirect the user to another URI, or whatever. I'd
        have to think about the options needed before I implement anything,
        though.

CVS REVISION
    $Id: AuthCookie.pm,v 2.39 2002/09/25 16:44:31 mschout Exp $

AUTHOR
    Michael Schout <mschout@gkg.net>

    Originally written by Eric Bartley <bartley@purdue.edu>

    versions 2.x were written by Ken Williams <ken@forum.swarthmore.edu>

COPYRIGHT
    Copyright (c) 2000 Ken Williams. All rights reserved.

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

SEE ALSO
    the perl(1) manpage, the mod_perl(1) manpage, the Apache(1) manpage.

