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|
package CGI::Application::Plugin::ProtectCSRF;
=pod
=head1 NAME
CGI::Application::Plugin::ProtectCSRF - generate and verify anti-CSRF tickets
=head1 VERSION
1.01
=head1 SYNPSIS
use Your::App;
use base qw(CGI::Application);
use CGI::Application::Plugin::Session; # mandatory !!
use CGI::Application::Plugin::ProtectCSRF;
sub input_form : PublishCSRFID {
my $self = shift;
do_something();
}
sub finish : ProtectCSRF {
my $self = shift;
$self->clear_csrf_id;
do_something();
}
=head1 DESCRIPTION
CGI::Application::Plugin::ProtectCSRF provides tools to protect forms in
L<CGI::Application> web applications from CSRF attacks. Run mode handlers
may be declared with the C<PublishCSFRID> or C<ProtectCSFR> attributes.
The former should usually be applied to a run mode, whose HTML includes
a C<form> tag. In this case a ticket is generated and stored in the session
during a prerun callback and a C<hidden> control field, publishing the
ticket, is added to the form during a postrun callback. Conversely the
C<ProtectCSRF> attribute should normally be applied to the corresponding
run modes that process data from a submitted form. A prerun callback checks
for the hidden field and checks that it matches the ticket saved
in the session. If the check fails the page is redirected to a
customizable error page. On success the form processing run mode should
use the C<clear_csrf_id> method, so that subsequent calls to forms from that
session will generate fresh tickets.
=cut
use strict;
use base qw(Exporter);
use Carp;
use HTML::TokeParser;
use Digest::SHA1 qw(sha1_hex);
use Attribute::Handlers;
our(
@EXPORT,
$CSRF_ERROR_MODE,
$CSRF_ERROR_STATUS,
$CSRF_ERROR_TMPL,
$CSRF_ID,
$CSRF_ID_LENGTH,
$CSRF_POST_ONLY,
$VERSION
);
@EXPORT = qw(
clear_csrf_id
csrf_id
protect_csrf_config
);
$CSRF_ERROR_MODE = "_csrf_error";
$CSRF_ERROR_STATUS = 200;
$CSRF_ERROR_TMPL = \qq{<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html>
<head><title>CSRF ERROR</title></head>
<body>
<h1>CSRF ERROR</h1>
<p>Access denied. Please contact the website administrator.</p>
</body>
</html>
};
$CSRF_ID = "_csrf_id";
$CSRF_POST_ONLY = 0;
$VERSION = 1.01;
my(%publish_csrf_id_runmodes, %protect_csrf_runmodes);
sub import {
my $pkg = caller;
# C::A::P::Session method check
croak("CGI::Aplication::Plugin::Session module is not loaded in your app") if !$pkg->can("session");
$pkg->add_callback("prerun", \&_publish_csrf_id);
$pkg->add_callback("prerun", \&_csrf_forbidden);
$pkg->add_callback("postrun", \&_add_csrf_id);
goto &Exporter::import;
}
=pod
=head1 ACTION
=head2 PublishCSRFID
Run modes declared with the C<PublishCSRFID> attribute, take the following
actions:
=over
=item - generate CSRF ticket and store it in the session;
=item - generate the form as per the module code;
=item - add a hidden element to the form publishing the CSRF ticket.
=back
# publish CSRF ticket
sub input_form : PublishCSRFID {
my $self = shift;
return <<HTML;
<form action="foo" method="post">
<input type="text" name="name">
<input type="submit" value="submit!">
<input type="hidden" name="rm" value="finish">
</form>
HTML
}
# display html source
<form action="foo" method="post">
<input type="hidden" name="_csrf_id" value="random string" /> <- insert hidden field
<input type="text" name="name">
<input type="submit" value="submit!">
<input type="hidden" name="rm" value="finish">
</form>
=head2 ProtectCSRF
Run modes declared with the C<ProtectCSRF> attribute, take the following
actions:
=over
=item - verify that the submitted CSRF ticket matches the ticket saved in the
session. If there is any sort of issue with the ticket the page is
redirected to a customizable error page;
=item - the form is processed as per the module code;
=item - the form should call the C<clear_csfr_id> method so that subsequent forms
generate fresh tickets. The code does not do this because if the form validation
fails it might be best to retain the same ticket.
=back
sub finish : ProtectCSRF {
my $self = shift;
# required! Unless forms and their processing are tightly
# coupled by clearing the ticket between invocations,
# the meaning of the ticket is lost.
$self->clear_csrf_id;
# The processing that you want to perform (DB processing etc)
do_something();
}
=cut
sub CGI::Application::PublishCSRFID : ATTR(BEGIN) {
my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
$publish_csrf_id_runmodes{$referent} = 1;
#$publish_csrf_id_runmodes{*{$symbol}{NAME}} = 1;
}
sub CGI::Application::ProtectCSRF : ATTR(BEGIN) {
my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
$protect_csrf_runmodes{$referent} = 1;
}
=pod
=head1 METHOD
=head2 csrf_id
This method returns the CSRF ticket saved in the session.
Example:
sub input_form : PublishCSRFID {
my $self = shift;
my $csrf_id = $self->csrf_id;
do_something();
}
=cut
sub csrf_id {
my $self = shift;
return $self->session->param($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id});
}
=head2 protect_csrf_config
This method initializes the ProtectCSRF state using any configuration options
that were passed to it. The available options are:
=over
=item B<csrf_error_status> - The HTTP status code that would be set on the
CSRF error page if a CSRF attack is identified. It defaults to 200.
=item B<csrf_error_mode> - The L<CGI::Application> runmode name. This defaults to C<_csrf_error>.
=for comment
The Debian maintainer is unclear why this option is useful. Surely an
anonymous run mode would be cleaner here.
=end comment
=item B<csrf_error_tmpl> - The HTML displayed in the event of a CSRF attack being
detected in the form of a scalarref or filepath or filehandle. One may
consider L<HTML::Template> for inspiration on thse formats. The default is
C<$CSRF_ERROR_TMPL> which is a scalarref.
=item B<csrf_error_tmpl_param> - A hashref of parameters to be placed in the
above template. See L<HTML::Template>.
=for comment
The Debian maintainer thinks other templating systems should work but is
unlikely to experiment with this in the near future.
=end comment
=item B<csrf_id> - The name of the session parameter used to store the CSRF ticket.This defaults to C<_csrf_id>.
=item B<csrf_post_only> - If set non-POST requests to a run mode which is protected
by this module would be rejected. By default this is 0.
=back
Example:
sub cgiapp_init {
my $self = shift;
$self->tmpl_path("/path/to/template");
$self->protect_csrf_config(
csrf_error_status => 403, # change forbidden
csrf_error_tmpl => "csrf_error.tmpl",
csrf_error_tmpl_param => { TITLE => "CSRF ERROR", MESSAGE => "your access is csrf!"},
csrf_id => "ticket_id",
csrf_post_only => 1
);
}
# csrf_error.tmpl
<html><head><title><TMPL_VAR NAME=TITLE ESCAPE=HTML></title></head>
<body>
<h1>CSRF Error</h1>
<span style="color: red"><TMPL_VAR NAME=MESSAGE ESCAPE=HTML></span>
</body>
</html>
=cut
sub protect_csrf_config {
my($self, %args) = @_;
if(ref($self->{__CAP_PROTECT_CSRF_CONFIG}) ne "HASH"){
$self->{__CAP_PROTECT_CSRF_CONFIG} = {};
}
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_status} = exists $args{csrf_error_status} ? $args{csrf_error_status} : $CSRF_ERROR_STATUS;
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_mode} = exists $args{csrf_error_mode} ? $args{csrf_error_mode} : $CSRF_ERROR_MODE;
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_tmpl} = exists $args{csrf_error_tmpl} ? $args{csrf_error_tmpl} : $CSRF_ERROR_TMPL;
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_tmpl_param} = {};
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id} = exists $args{csrf_id} ? $args{csrf_id} : $CSRF_ID;
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_post_only} = exists $args{csrf_post_only} ? $args{csrf_post_only} : $CSRF_POST_ONLY;
if(ref($args{csrf_error_tmpl_param}) eq "HASH" && keys %{$args{csrf_error_tmpl_param}}){
$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_tmpl_param} = $args{csrf_error_tmpl_param};
}
}
=pod
=head2 clear_csrf_id
This method clears the CSFR ticket. This should be done during the processing
of a form request.
Example :
sub cgiapp_init {
my $self = shift;
$self->protect_csrf_config;
}
sub input {
my $self = shift;
do_something(). # input form display..
}
sub confirm : PublishCSRFID {
my $self = shift;
do_something(). # publish csrf_id and input check and confirm display..
}
sub complete : ProtectCSRF {
my $self = shift;
$self->clear_csrf_id(1); # clear csrf_id for CSRF protect
do_something(); # DB insert etc..
}
=cut
sub clear_csrf_id {
my($self, $fast) = @_;
$self->session->clear($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id});
$self->session->flush if $fast;
}
=pod
=head1 CALLBACK
=head2 _publish_csrf_id
prerun callback
=cut
sub _publish_csrf_id {
my($self, $rm) = @_;
return if !exists $publish_csrf_id_runmodes{$self->can($rm)};
if(ref($self->{__CAP_PROTECT_CSRF_CONFIG}) ne "HASH"){
$self->protect_csrf_config;
}
my @words = ('A'..'Z', 'a'..'z', 0..9, '/', '.');
my $salt = join "", @words[ map { sprintf( "%d", rand(scalar @words) ) } 1..2 ];
my $csrf_id = sha1_hex($salt . time . $$ . rand(10000));
$self->session->param($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id}, $csrf_id);
}
=pod
=head2 _csrf_forbidden
prerun callback
=cut
sub _csrf_forbidden {
my($self, $rm) = @_;
my $err_flg = 0;
return if !exists $protect_csrf_runmodes{$self->can($rm)};
if(ref($self->{__CAP_PROTECT_CSRF_CONFIG}) ne "HASH"){
$self->protect_csrf_config;
}
if($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_post_only} && $ENV{REQUEST_METHOD} ne "POST"){
$err_flg = 1;
} else {
if(
!$self->query->param($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id}) ||
!$self->csrf_id ||
$self->query->param($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id}) ne $self->csrf_id
){
$err_flg = 1;
}
}
if($err_flg){
$self->run_modes( $self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_mode} => sub {
my $self = shift;
$self->header_props( -type => "text/html", -status => $self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_status} );
my $tmpl_obj = $self->load_tmpl($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_tmpl}, die_on_bad_params => 0);
if(keys %{$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_tmpl_param}}){
$tmpl_obj->param(%{$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_tmpl_param}});
}
return $tmpl_obj->output;
});
$self->prerun_mode($self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_error_mode});
}
return 0;
}
=pod
=head2 _add_csrf_id
postrun callback
=cut
sub _add_csrf_id {
my($self, $scalarref) = @_;
my $rm = $self->get_current_runmode;
my $coderef = $self->can($rm);
return if !$coderef || !exists $publish_csrf_id_runmodes{$coderef};
if(ref($self->{__CAP_PROTECT_CSRF_CONFIG}) ne "HASH"){
$self->protect_csrf_config;
}
# my %header = $self->header_props;
# return if %header && $header{-type} ne "text/html";
my $body = "";
my $hidden = sprintf qq{<input type="hidden" name="%s" value="%s" />}, $self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id}, $self->csrf_id;
my $parser = HTML::TokeParser->new($scalarref);
while(my $token = $parser->get_token){
# start tag(<form> sniping)
if($token->[0] eq "S"){
if(lc($token->[1]) eq "form"){
$body .= $token->[4] . "\n" . $hidden;
# In the future...
#}elsif(lc($token->[1]) eq "a"){
#
# if(exists $token->[2]->{href} && defined $token->[2]->{href}){
# my $uri = URI->new($token->[2]->{href});
# my %query_form = $uri->query_form;
# $query_form{$self->{__CAP_PROTECT_CSRF_CONFIG}->{csrf_id}} = $self->csrf_id;
# $uri->query_form(%query_form);
# $token->[2]->{href} = $uri->path_query;
# my $prop = join " ", (map { $_ . "=\"" . $token->[2]->{$_} . "\"" } keys %{$token->[2]});
# $body .= "<" . lc($token->[1]) . " ". $prop . ">";
# }else{
# $body .= $token->[4];
# }
}else{
$body .= $token->[4];
}
# end tag, process instructions
}elsif($token->[0] =~ /^(E|PI)$/){
$body .= $token->[2];
# text, comment, declaration
}elsif($token->[0] =~ /^(T|C|D)$/){
$body .= $token->[1];
}
}
${$scalarref} = $body;
}
1;
__END__
=head1 CAUTION
This module should not be seen as a panacea for all web security issues.
The user should fully understand and act on all security threats his
application may face, including whether this module is an adequate and
useful tool.
=head1 SEE ALSO
L<Attribute::Handlers>,
L<Carp>,
L<CGI::Application>,
L<CGI::Application::Plugin::Session>,
L<Digest::SHA1>,
L<Exporter>,
L<HTML::TokeParser>,
L<HTML::Template>
=head1 AUTHOR
Akira Horimoto <kurt0027@gmail.com>
=head1 COPYRIGHT
Copyright (C) 2006 - 2008 Akira Horimoto
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
=cut
|
