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lib/Catalyst/Plugin/SecureCookies.pm  view on Meta::CPAN

package Catalyst::Plugin::SecureCookies;
use strict;

use CGI::Cookie;
use Symbol;
use Class::Accessor::Fast;
use Digest::SHA1;
use Crypt::CBC;
use MIME::Base64;

our $VERSION = 0.01;
our $CIPHER;

=head1 NAME

Catalyst::Plugin::SecureCookies - Tamper-resistant, encrypted HTTP Cookies

=head1 SYNOPSIS

 use Catalyst qw/SecureCookies/;
 MyApp->config->{SecureCookies} = {
     key       => $blowfish_key,
     ssl       => 1       # send the checksum over ssl
 };
 MyApp->setup;

 # later, in another part of MyApp...

 $c->request->exp_secure_cookies( $expiration );
 $c->request->set_secure_cookie( 'my_cookie_name', $value );
 my $secure_data = $c->request->get_secure_cookie('my_cookie_name');

=head1 DESCRIPTION

=head2 Overview

When HTTP cookies are used to store a user's state or identity it's
important that your application is able to distinguish legitimate
cookies from those that have been edited or created by a malicious
user.

This module creates a pair of cookies which encrypt a form so the
user cannot modify cookie contents.

=head2 Implementation

SecureCookies is implemented using Crypt::CBC and MIME::Base64
to encrypt and encode a urlencoded string representing a perl
hash.  The encoded string is then hashed using Digest::SHA1 to
prepare a sort of "checksum" or hash to make sure the user did
not modify the cookie.

=head1 CONFIGURATION

=over 4

=item key

 MyApp->config->{SecureCookies}->{key} = $secret_key;

This parameter is B<required>, and sets the secret key that is used to
encrypt the cookies with Crypt::CBC Blowfish.  This needs to be a
16 hex character string.


=item ssl

 MyApp->config->{SecureCookies}->{ssl} = 0;
   # or
 MyApp->config->{SecureCookies}->{ssl} = 1;

This parameter is optional, and will default to C<1> if not set.

If C<1>, the checksum or hash cookie will be sent over SSL for
added security.  This will prevent replay attacks from being
used against the server.

If C<0>, the checksum will be sent as a normal, non-secure cookie.

=back

=head1 DIAGNOSTICS

=over 4

=back

=cut

=head1 METHODS

=head2 Catalyst Request Object Methods

=over 4

=cut

*{Symbol::qualify_to_ref('SecureCookies', 'Catalyst::Request')} =
  Class::Accessor::Fast::make_accessor('Catalyst::Request', 'SecureCookies');


=item C<< $c->request->get_secure_cookie($cookie_name) >>

If a cookie was successfully authenticated then this method will
return the value of the cookie.

=cut

*{Symbol::qualify_to_ref('get_secure_cookie', 'Catalyst::Request')} = sub {
    my $self = shift;
    my $name = shift;

    return $self->SecureCookies->{$name};
};

# add a secure cookie to the output
*{Symbol::qualify_to_ref('set_secure_cookie', 'Catalyst::Response')} = sub {
    my $self  = shift;
    my $name  = shift;
    my $value = shift;
    $self->{SecureCookies}->{$name} = $value;
};


## set the cookie exp time
*{Symbol::qualify_to_ref('exp_secure_cookies', 'Catalyst::Response')} =
  Class::Accessor::Fast::make_accessor('Catalyst::Request', 'exp_secure_cookies');

sub setup {
    my $self = shift;

    $self->config->{SecureCookies}->{ssl} ||= 1;


    return $self->NEXT::setup(@_);
}

# remove and check hash in Cookie Values
sub prepare_cookies {
    my $c = shift;
    $c->NEXT::prepare_cookies(@_);

    ## pull out our secure dudes
    $c->request->{SecureCookies} = {};
    my $rJ = $c->request->cookie( 'rJ' );
    my $rC = $c->request->cookie( 'rC' );

    ## decrypt them
    if( $rJ && $rC ) {
	## decode it
	my $secret_form = &_decrypt( $c,
				     $rJ->value,   # encoded cookie
				     $rC->value ); # it's checksum
	if( $secret_form ) {
	    foreach my $key (keys %$secret_form) {
		$c->request->{SecureCookies}->{$key} = $secret_form->{$key};
	    }
	}
    }
    
    return $c;
}

# alter all Cookie Values to include a hash
sub finalize_cookies {
    my $c = shift;

    my $sc = $c->response->{SecureCookies};

    if( $sc ) {
	## pull in the existing secure cookies
	my $sco = $c->req->SecureCookies;
	if( $sco ) {
	    foreach my $key (keys %$sco) {
		if( ! defined($sc->{$key}) ) {
		    $sc->{$key} = $sco->{$key};
		}
	    }
	}

	## first encode the form
	my ($encoded, $csum) = &_encrypt( $c, $sc );

	## ssl, yes or no?
	my $ssl = $c->config->{SecureCookies}->{ssl};
	my $ssl_val = $ssl ? 1 : 0;

	## expiration?
	my $exp = $c->response->exp_secure_cookies();

	## make the two cookies
	$c->response->cookies->{rJ} = { value => $encoded,
				        expires => $exp };
	$c->response->cookies->{rC} = { value => $csum,
				        expires => $exp };

	my $domain = $c->config->{SecureCookies}->{cookie_domain};
	if( $domain ) {
		$c->response->cookies->{rJ}->{domain} = ".$domain";
		$c->response->cookies->{rJ}->{path} = '/';
		$c->response->cookies->{rC}->{domain} = ".$domain";
		$c->response->cookies->{rC}->{path} = '/';
	}
    }

    $c->NEXT::finalize_cookies(@_);
    return $c;
}

=item B<_encrypt>

Description:
  Takes a hashref representing web form elements, encrypts the components, creates a base64 safe url string

Args:
  $form_hasref - hashref of vars

Return:
  $encoded     - the encoded form
  $csum        - the checksum

=cut

sub _encrypt {
    my ( $c, $form_hashref ) = @_;

    my $cipher = &_get_cipher( $c->config->{SecureCookies}->{key} );

    ## first url encode it
    my $encoded = &_url_encode_hashref( $form_hashref );

    ## now we encrypt and mime encode it
    my $encrypted = $cipher->encrypt( $encoded );
#    $encrypted =~ s/^RandomIV//;
    my $mimed = &_base64_encode_url( $encrypted );

    ## checksum it
    my $ctx = new Digest::SHA1;
    $ctx->add( $mimed );
    my $csum = substr( &_base64_encode_url( $ctx->digest ), 3, 4 );

    ## give em what they want
    return ($mimed, $csum);
}

=item B<_decrypt>

Description:
  Takes a base64 safe url string representing form elements, decrypts the components, creates a hashref