From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 23 Feb 2013 20:07:40 +0000 (+0000)
Subject: docs: wip
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=cgi-auth-flexible.git;a=commitdiff_plain;h=361099f1a596c854f9ae49973bdec7bda31223e9;ds=sidebyside

docs: wip
---

diff --git a/cgi-auth-flexible.pm b/cgi-auth-flexible.pm
index d4f248e..ae53ca3 100644
--- a/cgi-auth-flexible.pm
+++ b/cgi-auth-flexible.pm
@@ -1322,26 +1322,185 @@ __END__
 
 CGI::Auth::Flexible - web authentication optionally using cookies
 
-=head1 SYNOPSYS - STARTUP
+=head1 SYNOPSYS
 
  my $verifier = CGI::Auth::Flexible->new_verifier(setting => value,...);
- my $authreq = $verifier->new_request($cgi_request_object);
-
-=head1 SYNOPSYS - SIMPLE APPLICATIONS
+ my $authreq = $verifier->new_request($cgi_query_object);
 
+ # simple applications
  $authreq->check_ok() or return;
- ...
- $authreq->check_mutate();
- ...
-
-=head1 SYNOPSIS - SOPHISTICATED APPLICATIONS
 
+ # sophisticated applications
  my $divert_kind = $authreq->check_divert();
  if ($divert_kind) { ... print diversion page and quit ... }
- ...
+
+ # while handling the request
+ $user = $authreq->get_username();
  $authreq->check_mutate();
- ...
 
 =head1 DESCRIPTION
 
-CGI::Auth::Flexible is a
+CGI::Auth::Flexible is a library which you can use to add a
+forms/cookie-based login facility to a Perl web application.
+
+CGI::Auth::Flexible doesn't interfere with your application's URL path
+namespace and just needs a few (configurable) form parameter and
+cookie name(s) for its own use.  It tries to avoid making assumptions
+about the implementation structure of your application.
+
+Because CGI::Auth::Flexible is licenced under the AGPLv3, you will
+probably need to provide a facility to allow users (even ones not
+logged in) to download the source code for your web app.  Conveniently
+by default CGI::Auth::Flexible provides (for pure Perl webapps) a
+mechanism for users to get the source.
+
+CGI::Auth::Flexible is designed to try to stop you accidentally
+granting access by misunderstanding the API.  (Also it, of course,
+guards against cross-site scripting.)  You do need to make sure to
+call CGI::Auth::Flexible before answering AJAX requests as well as
+before generating HTML pages, of course, and to call it in every
+entrypoint to your system.
+
+=head1 INITIALISATION
+
+Your application should, on startup (eg, when it is loaded by
+mod_perl) do
+C<< $verifier = CGI::Auth::Flexible->new_verifier(settings...) >>.
+This call can be expensive and is best amortised.
+
+The resulting verifier object can be used to process individual
+requests, in each case with
+C<< $authreq = CGI::Auth::Flexible->new_request($cgi_query) >>.
+
+=head1 SIMPLE APPLICATIONS
+
+The simplist usage is to call C<< $request->check_ok() >> which will
+check the user's authentication.  If the user is not logged in it will
+generate a login form (or redirection or other appropriate page) and
+return false; your application should not then processing that request
+any further.  If the user is logged in it will return true.
+
+After calling C<check_ok> you can use C<< $request->get_username >>
+to find out which user the request came from.
+
+=head1 SOPHISTICATED APPLICATIONS
+
+If you want to handle the flow control and to generate login forms,
+redirections, etc., yourself, you can say
+C<< $divert = $request->check_divert >>.  This returns undef if
+the user is logged in, or I<divert spec> if some kind of login
+page or diversion should be generated.
+
+=head1 MUTATING OPERATIONS AND EXTERNAL LINKS INTO YOUR SITE
+
+By default CGI::Auth::Flexible does not permit external links into
+your site.  All GET requests give a "click to continue" page which
+submits a form.
+
+This is because the alternative (for complicated reasons relating to
+the web security architecture) is to require your application to make
+a special and different check when the incoming request is going to do
+some kind of action (such as modifying the user's setup, purchasing
+goods, or whatever) rather than just display HTML pages.
+
+To support external links, pass C<< promise_check_mutate => 1 >> in
+I<settings>, and then call C<< $authreq->check_mutate() >> before
+taking any actions.  If the incoming request is not suitable then
+C<< $authreq->check_mutate() >> will call C<die>.  If you do this you
+must make sure that you have no mutating C<GET> requests in your
+application - but you shouldn't have any of those anyway.
+
+=head1 SOURCE CODE DOWNLOAD
+
+By default, CGI::Auth::Flexible provides a facility for users to
+download the source code for the running version of your web
+application.
+
+This facility makes a number of important assumptions which you need
+to check.  Note that if the provided facility is not sufficient
+because your application is more sophisticated than it copes with (or
+if you disable the builtin facility), you may need to implement a
+functioning alternative to avoid violating the AGPLv3 licence.
+
+Here are the most important (default) assumptions:
+
+=over
+
+=item *
+
+Your app's source code is available by looking at @INC, $0 and
+S<$ENV{'SCRIPT_FILENAME'}> (the B<source items>).  See
+C<srcdump_listitems>.  Where these point to files or directories under
+revision control, the source item is the whole containing vcs tree.
+
+=item *
+
+Specifically, there are no compiled or autogenerated Perl
+files, Javascript resources, etc., which are not contained in one of
+the source item directories.  (Files which came with your operating
+system install don't need to be shipped as they fall under the system
+library exceptio.)
+
+=item *
+
+You have not installed any modified versions of system
+libraries (including system-supplied) Perl modules in C</usr> outside
+C</usr/local>.  See C<srcdump_system_dir>.
+
+=item *
+
+For each source item in a dvcs, the entire dvcs history does
+not contain anything confidential (or libellous).  Also, all files which
+contain secrets are in the dvcs's C<.ignore> file.  See
+C<srcdump_vcsscript_git> et al.
+
+=item *
+
+For each source item NOT in a dvcs, there are no confidential
+files with the world-readable bit set (being in a world-inaccessible
+directory is not sufficient).  See C<srcdump_excludes>.
+
+=item *
+
+You have none of your app's source code in C</etc>.
+
+=item *
+
+You don't regard pathnames on your server as secret.
+
+=item *
+
+You don't intentionally load Perl code by virtule of C<.>
+being in C<@INC> by default.  (See C<srcdump_filter_cwd>.)
+
+=back
+
+=head1 FUNCTIONS AND METHODS
+
+=over
+
+=item C<< CGI::Auth::Flexible::new_verifier(setting => value, ...) >>
+
+Initialises an instance and returns a verifier object.
+The arguments are setting pairs like a hash initialiser.
+See L</SETTINGS> below.
+
+=item C<< $verifier->new_request($cgi_query) >>
+
+Prepares to process a request.  C<$cgi_query> should normally
+be the query object from L<CGI(3perl)>.  Most of the default
+hook methods assume that it is; however if you replace enough of
+the hook methods then you can pass any value you like and it
+will be passed to your hooks.
+
+The return value is the authentication request object (C<$authreq>)
+which is used to check the incoming request and will contain
+information about its credentials.
+
+=item C<< $authreq->check_divert() >>
+
+Checks whether the user is logged in.  Returns undef if the user is
+logged in and we should service the request.  Otherwise returns a
+divert spec (see L</DIVERT SPEC>) saying what should happen instead.
+
+=back