=head1 APACHE 2.4 PORTING NOTES

=head2 VERY IMPORTANT!!!

Apache 2.4 has a B<VERY> different authentication API from previous versions.
You will not be able to simply ugrade apache and upgrade AuthCookie in order to
migrate to Apache 2.4.  You will also need to port your AuthCookie subclass
over to the Apache 2.4 API, and update your Apache configuration for Apache
2.4.

This document attempts to help you understand the changes required and
how to port your module over to Apache 2.4.  If your subclass stopped working
when you migrated to Apache 2.4, please make sure you have read and understand
everything in this document before filing a bug report.

=head2 Changes Required to Run Under Apache 2.4

=over 4

=item Mod Perl

You need at least C<mod_perl> version 2.0.9, which is the first official
release to support Apache 2.4.

=item Apache::Test

You need Apache::Test version 1.39 or later.  Previous versions do not define
the constant C<APACHE2_4> which is needed for the test suite.

=item Your AuthCookie Subclass

=over 4

=item *

Your module must inherit from C<Apache2_4::AuthCookie> instead of C<Apache2::AuthCookie>

=item *

You must change every method that was called as a C<PerlAuthzHandler> under
previous versions to return one of the following values:

=over 4

=item Apache2::Const::AUTHZ_DENIED_NO_USER

return this constant if C<< $r->user >> is empty/undefined and you do not wish
to allow anonymous access.

=item Apache2::Const::AUTHZ_DENIED

return this constant if C<< $r->user >> is not authorized for the current request.

=item Apache2::Const::AUTHZ_GRANTED

return this constant if C<< $r->user >> is authorized for the current request

=item Apache2::Const::AUTHZ_GENERAL_ERROR

return this constant to indicate an error processing authz requirements.

=item Apache2::Const::AUTHZ_NEUTRAL

return this constant to indicate a neutral response.  It is assumed that
another authz provider will be checked in a parent/sibling scope that will
return granted or denied.

=back

=back

=item httpd.conf

=over 4

=item *

Remove all C<PerlAuthzHandler> entries.  C<PerlAuthzHandler> does not exist in Apache 2.4.

=item *

Depending on what your C<Require> directives say, you may need to add one or
more top level C<PerlAddAuthzProvider> entires and implement a handler for each
one.

If your C<Require> directives are simply C<valid-user> or C<user ...> then you
do not need to do this.  Apache already provides an authz provider that handles
C<user> and C<valid-user> requirements for you in C<mod_authz_user>.

C<AuthCookie> does provide a C<authz_handler> for these requirements for
backwards compatibility with previous versions, but the one provided by Apache
is preferred.

=item *

If you are C<Require>'ing anything other than C<valid-user> or C<user ...> then
you will need to write your own Authz Provider method and register it with Apache.

Authz Providers are the Apache 2.4 equivalent of a C<PerlAuthzHandler> method.
Each one implements a specific requirement. E.g.:

 PerlAddAuthzProvider species My::AuthCookieHandler->authz_species

Will be called to handle a 

 Require species klingon

Directive.

It is important to know that Authz Providers are called B<twice> for
a request.  First, the authz provider is called before authentication has been
processed to check for anonymous access.  In this method call, C<< $r->user >>
is not set.  You are expected to return one of:

=over 4

=item AUTHZ_GRANTED

Access is granted and no further authn/authz processing will occur for this
request.

=item AUTHZ_DENIED

=item AUTHZ_NEUTRAL

The response is C<HTTP_FORBIDDEN> (unless neutral is overridden by another
provider)

=item AUTHZ_DENIED_NO_USER

Authentication is processed, C<< $r->user >> will be set with the current
username and your authz provider will be called again.

=back

The second time the authz provider is called, C<< $r->user >> is set and you
are expected to return one of:

=over 4

=item AUTHZ_GRANTED

The request is allowed

=item AUTHZ_DENIED

The request is forbidden

=item AUTHZ_NEUTRAL

The request is forbidden, unless another authz provider returns
C<AUTHZ_GRANTED>.  Consult the apache documentation about authorization merging
for more info.

=back

You could also return C<AUTHZ_GENERAL_ERROR> from any of these to indicate an
error processing authz directives and halt processing immediately.

One way to think about these response codes what kind of Require satisfies is
in effect:

=over 4

=item RequireAll/RequireNone

In this case the priority of responses is:

=over 4

=item AUTHZ_GENERAL_ERROR

Processing stops immediately

=item AUTHZ_DENIED

Processing stops immediately, no siblings are processed. Request is denied.

=item AUTHZ_DENIED_NO_USER

Process Authentication and try again

=item AUTHZ_GRANTED

Continue processing siblings.

=item AUTZ_NEUTRAL

Continue processing siblings.

=back

=item RequireAny

In this case the priority of responses is:

=over 4

=item AUTHZ_GENERAL_ERROR

Processing stops immediately

=item AUTHZ_GRANTED

Processing stops immediately, no siblings are processed.  Request is allowed.

=item AUTHZ_DENIED_NO_USER

Process Authentication and try again

=item AUTHZ_DENIED

Continue processing siblings.

=item AUTZ_NEUTRAL

Continue processing siblings.

=back

=back

=back

=back

=head2 Important Internal API Changes for Apache 2.4

=over 4

=item authorize() has been removed

You need to use a C<PerlAddAuthzProvider> and write an appropriate handler as
described above instead.  Note that you do not need a C<PerlAddAuthzProvider>
for C<user> or C<valid-user> requirements.  Apache already handles those
internally.

=item ${auth_name}Satisfy

Satisfy support is removed as it is no longer needed with Apache 2.4.

You are expected to use C<RequireAll> or C<RequireAny> instead.

e.g.:

    PerlAddAuthzProvider species Your::AuthCookieHandler->authz_species_handler

    <RequireAll>
      Require valid-user
      Require species klingon
    </RequireAll>

see: L<https://httpd.apache.org/docs/2.4/howto/auth.html#reqaccessctrl>

=item Unauthorized User HTTP Response Code

In Apache 2.4, in C<mod_authz_core>, if no authz handlers return C<AUTHZ_GRANTED>,
then C<HTTP_UNAUTHORIZED> is returned.  In previous versions of Apache,
C<HTTP_FORBIDDEN> was returned.  You can get the old behaviour if you want it
with:

    AuthzSendForbiddenOnFailure On

=back

=head1 FREQUENTLY ASKED QUESTIONS

=over 4

=item *

Why is my authz method called twice per request?

This is normal behaviour under Apache 2.4.  This is to accomodate 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 *

My log shows an entry like:

 authorization result of Require ...: denied (no + # authenticated user yet)

These are normal.  This happens because the authz provider returned
C<AUTHZ_DENIED_NO_USER> and the authz provider will be called again after
authentication happens.

=back
