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lib/Apache2_4/AuthCookie.pm  view on Meta::CPAN

 # 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=\"...\""

 # optional: enable decoding of intercepted GET/POST params:
 PerlSetVar WhatEverEncoding UTF-8

 # optional: enable decoding of httpd.conf "Requires" directives
 PerlSetVar WhatEverRequiresEncoding UTF-8

 # These documents require user to be logged in.
 <Location /protected>
  AuthType Sample::Apache2::AuthCookieHandler
  AuthName WhatEver
  PerlAuthenHandler Sample::Apache2::AuthCookieHandler->authenticate
  Require valid-user
 </Location>

 # How to handle a custom requirement (non-user).
 PerlAddAuthzProvider species Sample::Apache2::AuthCookieHandler->authz_species
 <Location /protected/species>
   Require species klingon
 </Location>

 # These documents don't require logging in, but allow it.
 <FilesMatch "\.ok$">
  AuthType Sample::Apache2::AuthCookieHandler
  AuthName WhatEver
  PerlFixupHandler Sample::Apache2::AuthCookieHandler->recognize_user
 </FilesMatch>

 # This is the action of the login.pl script above.
 <Files LOGIN>
  AuthType Sample::Apache2::AuthCookieHandler
  AuthName WhatEver
  SetHandler perl-script
  PerlResponseHandler Sample::Apache2::AuthCookieHandler->login
 </Files>

=head1 DESCRIPTION

This module is for C<mod_perl> version 2 for C<Apache> version 2.4.x.  If you
are running mod_perl version 1, you need B<Apache::AuthCookie> instead.  If you
are running C<Apache> 2.0.0-2.2.x, you need B<Apache2::AuthCookie> instead.

B<Apache2_4::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:

=over 4

=item C<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.

=item C<authen_ses_key()>

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

=back

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

=over 4

=item 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.

=item 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.

=item 3.

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

=item 4.

You can specify the domain of a cookie using C<PerlSetVar> commands.  For
instance, if your AuthName is C<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 C<.yourhost.com>.

=item 5.

You can optionally specify the name of your cookie using the C<CookieName>
directive.  For instance, if your AuthName is C<WhatEver>, you can put the
command

lib/Apache2_4/AuthCookie.pm  view on Meta::CPAN

your C<authen_cred()> method.

=item 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 C<$r-E<gt>prev-E<gt>uri>.  See the login.pl script in t/eg/.

=back

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, B<AuthCookie> will set
C<$r-E<gt>subprocess_env('AuthCookieReason')> to one of the following values.

=over 4

=item I<no_cookie>

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

=item I<bad_cookie>

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

=item I<bad_credentials>

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

=back

You can examine this value in your login form by examining
C<$r-E<gt>prev-E<gt>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 C<authen_ses_key()> method can set
arbitrary entries in C<$r-E<gt>subprocess_env>.

=head1 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/htdocs/docs/logout.pl.  Logout scripts may want to take advantage of
AuthCookie's C<logout()> method, which will set the proper cookie headers in
order to clear the user's cookie.  This usually looks like
C<$r-E<gt>auth_type-E<gt>logout($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.

=head1 ABOUT SESSION KEYS

Unlike the sample AuthCookieHandler, you have you verify the user's login and
password in C<authen_cred()>, then you do something like:

    my $date = localtime;
    my $ses_key = Digest::SHA::sha256_hex(join(';', $date, $PID, $PAC));

save C<$ses_key> along with the user's login, and return C<$ses_key>.

Now C<authen_ses_key()> looks up the C<$ses_key> passed to it and returns the
saved login.  I use a database to store the session key and retrieve it later.

=head1 FREQUENTLY ASKED QUESTIONS

=over 4

=item *

I upgraded to Apache 2.4 and now AuthCookie doesn't work!

Apache 2.4 radically changed the authentication and authorization API.  You will
need to port your AuthCookie subclass over to the Apache 2.4 API.  See the POD
documentation in L<README.apache-2.4> for more information, but the quick
rundown is you need to:

=over 4

=item *

Inherit from C<Apache2_4::AuthCookie>

=item *

Remove all C<PerlAuthzHandler> configuration entries.

=item *

Write Authz Provider methods for any C<Requires> directives that you are using
that Apache does not provide for already (e.g. Apache already handles C<user>
and C<valid-user>) and register them with something like.

 PerlAddAuthzProvier species Sample::AuthCookieHandler->authz_species

=item *

Replace instances of C<${AuthName}Satistfy> with either C<RequireAll> or
C<RequireAny> blocks.

=back

=item *

Why is my authz method called twice per request?

This is normal behaviour under Apache 2.4.  This is to accommodate for
authorization of anonymous access. You are expected to return
C<Apache2::Const::AUTHZ_DENIED_NO_USER> IF C<< $r->user >> has not yet been set
if you want authentication to proceed.  Your authz handler will be called a
second time after the user has been authenticated.

=item *