Nicholas Bamber > CGI-Application-Plugin-Authentication-0.20 > CGI::Application::Plugin::Authentication

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NAME ^

CGI::Application::Plugin::Authentication - Authentication framework for CGI::Application

VERSION ^

This document describes CGI::Application::Plugin::Authentication version 0.20

SYNOPSIS ^

 package MyCGIApp;

 use base qw(CGI::Application); # make sure this occurs before you load the plugin

 use CGI::Application::Plugin::Authentication;

 MyCGIApp->authen->config(
       DRIVER => [ 'Generic', { user1 => '123' } ],
 );
 MyCGIApp->authen->protected_runmodes('myrunmode');

 sub myrunmode {
    my $self = shift;

    # The user should be logged in if we got here
    my $username = $self->authen->username;

 }

DESCRIPTION ^

CGI::Application::Plugin::Authentication adds the ability to authenticate users in your CGI::Application modules. It imports one method called 'authen' into your CGI::Application module. Through the authen method you can call all the methods of the CGI::Application::Plugin::Authentication plugin.

There are two main decisions that you need to make when using this module. How will the usernames and password be verified (i.e. from a database, LDAP, etc...), and how can we keep the knowledge that a user has already logged in persistent, so that they will not have to enter their credentials again on the next request (i.e. how do we 'Store' the authentication information across requests).

Choosing a Driver

There are three drivers that are included with the distribution. Also, there is built in support for all of the Authen::Simple modules (search CPAN for Authen::Simple for more information). This should be enough to cover everyone's needs.

If you need to authenticate against a source that is not provided, you can use the Generic driver which will accept either a hash of username/password pairs, or an array of arrays of credentials, or a subroutine reference that can verify the credentials. So through the Generic driver you should be able to write your own verification system. There is also a Dummy driver, which blindly accepts any credentials (useful for testing). See the CGI::Application::Plugin::Authentication::Driver::Generic, CGI::Application::Plugin::Authentication::Driver::DBI and, CGI::Application::Plugin::Authentication::Driver::Dummy docs for more information on how to use these drivers. And see the Authen::Simple suite of modules for information on those drivers.

Choosing a Store

The Store modules keep information about the authentication status of the user persistent across multiple requests. The information that is stored in the store include the username, and the expiry time of the login. There are two Store modules included with this distribution. A Session based store, and a Cookie based store. If your application is already using Sessions (through the CGI::Application::Plugin::Session module), then I would recommend that you use the Session store for authentication. If you are not using the Session plugin, then you can use the Cookie store. The Cookie store keeps all the authentication in a cookie, which contains a checksum to ensure that users can not change the information.

If you do not specify which Store module you wish to use, the plugin will try to determine the best one for you.

Login page

The Authentication plugin comes with a default login page that can be used if you do not want to create a custom login page. This login form will automatically be used if you do not provide either a LOGIN_URL or LOGIN_RUNMODE parameter in the configuration. If you plan to create your own login page, I would recommend that you start with the HTML code for the default login page, so that your login page will contain the correct form fields and hidden fields.

Ticket based authentication

This Authentication plugin can handle ticket based authentication systems as well. All that is required of you is to write a Store module that can understand the contents of the ticket. The Authentication plugin will require at least the 'username' to be retrieved from the ticket. A Ticket based authentication scheme will not need a Driver module at all, since the actual verification of credentials is done by an external authentication system, possibly even on a different host. You will need to specify the location of the login page using the LOGIN_URL configuration variable, and unauthenticated users will automatically be redirected to your ticket authentication login page.

EXPORTED METHODS ^

authen

This is the only method exported from this module. Everything is controlled through this method call, which will return a CGI::Application::Plugin::Authentication object, or just the class name if called as a class method. When using the plugin, you will always first call $self->authen or __PACKAGE__->authen and then the method you wish to invoke. For example:

  __PACKAGE__->authen->config(
        LOGIN_RUNMODE => 'login',
  );

- or -

  $self->authen->protected_runmodes(qw(one two));

METHODS ^

config

This method is used to configure the CGI::Application::Plugin::Authentication module. It can be called as an object method, or as a class method. Calling this function, will not itself generate cookies or session ids.

The following parameters are accepted:

DRIVER

Here you can choose which authentication module(s) you want to use to perform the authentication. For simplicity, you can leave off the CGI::Application::Plugin::Authentication::Driver:: part when specifying the DRIVER name If this module requires extra parameters, you can pass an array reference that contains as the first parameter the name of the module, and the rest of the values in the array will be considered options for the driver. You can provide multiple drivers which will be used, in order, to check the credentials until a valid response is received.

     DRIVER => 'Dummy' # let anyone in regardless of the password

  - or -

     DRIVER => [ 'DBI',
         DBH         => $self->dbh,
         TABLE       => 'user',
         CONSTRAINTS => {
             'user.name'         => '__CREDENTIAL_1__',
             'MD5:user.password' => '__CREDENTIAL_2__'
         },
     ],

  - or -

     DRIVER => [
         [ 'Generic', { user1 => '123' } ],
         [ 'Generic', sub { my ($u, $p) = @_; is_prime($p) ? 1 : 0 } ]
     ],

  - or -

     DRIVER => [ 'Authen::Simple::LDAP',
         host   => 'ldap.company.com',
         basedn => 'ou=People,dc=company,dc=net'
     ],
STORE

Here you can choose how we store the authenticated information after a user has successfully logged in. We need to store the username so that on the next request we can tell the user has already logged in, and we do not have to present them with another login form. If you do not provide the STORE option, then the plugin will look to see if you are using the CGI::Application::Plugin::Session module and based on that info use either the Session module, or fall back on the Cookie module. If the module requires extra parameters, you can pass an array reference that contains as the first parameter the name of the module, and the rest of the array should contain key value pairs of options for this module. These storage modules generally live under the CGI::Application::Plugin::Authentication::Store:: name-space, and this part of the package name can be left off when specifying the STORE parameter.

    STORE => 'Session'

  - or -

    STORE => ['Cookie',
        NAME   => 'MYAuthCookie',
        SECRET => 'FortyTwo',
        EXPIRY => '1d',
    ]
POST_LOGIN_RUNMODE

Here you can specify a runmode that the user will be redirected to if they successfully login.

  POST_LOGIN_RUNMODE => 'welcome'
POST_LOGIN_URL

Here you can specify a URL that the user will be redirected to if they successfully login. If both POST_LOGIN_URL and POST_LOGIN_RUNMODE are specified, then the latter will take precedence.

  POST_LOGIN_URL => 'http://example.com/start.cgi'
POST_LOGIN_CALLBACK

A code reference that is executed after login processing but before POST_LOGIN_RUNMODE or redirecting to POST_LOGIN_URL. This is normally a method in your CGI::Application application and as such the CGI::Application object is passed as a parameter.

  POST_LOGIN_CALLBACK => \&update_login_date

and later in your code:

  sub update_login_date {
    my $self = shift;

    return unless($self->authen->is_authenticated);

    ...
  }
LOGIN_RUNMODE

Here you can specify a runmode that the user will be redirected to if they need to login.

  LOGIN_RUNMODE => 'login'
LOGIN_URL

If your login page is external to this module, then you can use this option to specify a URL that the user will be redirected to when they need to login. If both LOGIN_URL and LOGIN_RUNMODE are specified, then the latter will take precedence.

  LOGIN_URL => 'http://example.com/login.cgi'
LOGOUT_RUNMODE

Here you can specify a runmode that the user will be redirected to if they ask to logout.

  LOGOUT_RUNMODE => 'logout'
LOGOUT_URL

If your logout page is external to this module, then you can use this option to specify a URL that the user will be redirected to when they ask to logout. If both LOGOUT_URL and LOGOUT_RUNMODE are specified, then the latter will take precedence.

  LOGIN_URL => 'http://example.com/logout.html'
DETAINT_URL_REGEXP

This is a regular expression used to detaint URLs used in the login form. By default it will be set to

  ^([\w\_\%\?\&\;\-\/\@\.\+\$\=\#\:\!\*\"\'\(\)\,]+)$

This regular expression is based upon the document http://www.w3.org/Addressing/URL/url-spec.txt. You could set it to a more specific regular expression to limit the domains to which users could be directed.

DETAINT_USERNAME_REGEXP

This is a regular expression used to detaint the username parameter used in the login form. By default it will be set to

  ^([\w\_]+)$
CREDENTIALS

Set this to the list of form fields where the user will type in their username and password. By default this is set to ['authen_username', 'authen_password']. The form field names should be set to a value that you are not likely to use in any other forms. This is important because this plugin will automatically look for query parameters that match these values on every request to see if a user is trying to log in. So if you use the same parameter names on a user management page, you may inadvertently perform a login when that was not intended. Most of the Driver modules will return the first CREDENTIAL as the username, so make sure that you list the username field first. This option can be ignored if you use the built in login box

  CREDENTIALS => 'authen_password'

  - or -

  CREDENTIALS => [ 'authen_username', 'authen_domain', 'authen_password' ]
LOGIN_SESSION_TIMEOUT

This option can be used to tell the system when to force the user to re-authenticate. There are a few different possibilities that can all be used concurrently:

IDLE_FOR

If this value is set, a re-authentication will be forced if the user was idle for more then x amount of time.

EVERY

If this value is set, a re-authentication will be forced every x amount of time.

CUSTOM

This value can be set to a subroutine reference that returns true if the session should be timed out, and false if it is still active. This can allow you to be very selective about how the timeout system works. The authen object will be passed in as the only parameter.

Time values are specified in seconds. You can also specify the time by using a number with the following suffixes (m h d w), which represent minutes, hours, days and weeks. The default is 0 which means the login will never timeout.

Note that the login is also dependent on the type of STORE that is used. If the Session store is used, and the session expires, then the login will also automatically expire. The same goes for the Cookie store.

For backwards compatibility, if you set LOGIN_SESSION_TIMEOUT to a time value instead of a hashref, it will be treated as an IDLE_FOR time out.

  # force re-authentication if idle for more than 15 minutes
  LOGIN_SESSION_TIMEOUT => '15m'

  # Everyone must re-authentication if idle for more than 30 minutes
  # also, everyone must re-authentication at least once a day
  # and root must re-authentication if idle for more than 5 minutes
  LOGIN_SESSION_TIMEOUT => {
        IDLE_FOR => '30m',
        EVERY    => '1d',
        CUSTOM   => sub {
          my $authen = shift;
          return ($authen->username eq 'root' && (time() - $authen->last_access) > 300) ? 1 : 0;
        }
  }
RENDER_LOGIN

This value can be set to a subroutine reference that returns the HTML of a login form. The subroutine reference overrides the default call to login_box. The subroutine is normally a method in your CGI::Application application and as such the CGI::Application object is passed as the first parameter.

  RENDER_LOGIN => \&login_form

and later in your code:

  sub login_form {
    my $self = shift;

    ...
    return $html
  }
LOGIN_FORM

You can set this option to customize the login form that is created when a user needs to be authenticated. If you wish to replace the entire login form with a completely custom version, then just set LOGIN_RUNMODE to point to your custom runmode.

All of the parameters listed below are optional, and a reasonable default will be used if left blank:

DISPLAY_CLASS (default: Classic)

the class used to display the login form. The alternative is Basic which aims for XHTML compliance and leaving style to CSS. See CGI::Application::Plugin::Authentication::Display for more details.

TITLE (default: Sign In)

the heading at the top of the login box

USERNAME_LABEL (default: User Name)

the label for the user name input

PASSWORD_LABEL (default: Password)

the label for the password input

SUBMIT_LABEL (default: Sign In)

the label for the submit button

COMMENT (default: Please enter your username and password in the fields below.)

a message provided on the first login attempt

REMEMBERUSER_OPTION (default: 1)

provide a checkbox to offer to remember the users name in a cookie so that their user name will be pre-filled the next time they log in

REMEMBERUSER_LABEL (default: Remember User Name)

the label for the remember user name checkbox

REMEMBERUSER_COOKIENAME (default: CAPAUTHTOKEN)

the name of the cookie where the user name will be saved

REGISTER_URL (default: <none>)

the URL for the register new account link

REGISTER_LABEL (default: Register Now!)

the label for the register new account link

FORGOTPASSWORD_URL (default: <none>)

the URL for the forgot password link

FORGOTPASSWORD_LABEL (default: Forgot Password?)

the label for the forgot password link

INVALIDPASSWORD_MESSAGE (default: Invalid username or password<br />(login attempt %d)

a message given when a login failed

INCLUDE_STYLESHEET (default: 1)

use this to disable the built in style-sheet for the login box so you can provide your own custom styles

FORM_SUBMIT_METHOD (default: post)

use this to get the form to submit using 'get' instead of 'post'

FOCUS_FORM_ONLOAD (default: 1)

use this to automatically focus the login form when the page loads so a user can start typing right away.

BASE_COLOUR (default: #445588)

This is the base colour that will be used in the included login box. All other colours are automatically calculated based on this colour (unless you hardcode the colour values). In order to calculate other colours, you will need the Color::Calc module. If you do not have the Color::Calc module, then you will need to use fixed values for all of the colour options. All colour values besides the BASE_COLOUR can be simple percentage values (including the % sign). For example if you set the LIGHTER_COLOUR option to 80%, then the calculated colour will be 80% lighter than the BASE_COLOUR.

LIGHT_COLOUR (default: 50% or #a2aac4)

A colour that is lighter than the base colour.

LIGHTER_COLOUR (default: 75% or #d0d5e1)

A colour that is another step lighter than the light colour.

DARK_COLOUR (default: 30% or #303c5f)

A colour that is darker than the base colour.

DARKER_COLOUR (default: 60% or #1b2236)

A colour that is another step darker than the dark colour.

GREY_COLOUR (default: #565656)

A grey colour that is calculated by desaturating the base colour.

protected_runmodes

This method takes a list of runmodes that are to be protected by authentication. If a user tries to access one of these runmodes, then they will be redirected to a login page unless they are properly logged in. The runmode names can be a list of simple strings, regular expressions, or special directives that start with a colon. This method is cumulative, so if it is called multiple times, the new values are added to existing entries. It returns a list of all entries that have been saved so far. Calling this function, will not itself generate cookies or session ids.

:all - All runmodes in this module will require authentication
  # match all runmodes
  __PACKAGE__->authen->protected_runmodes(':all');

  # only protect runmodes one two and three
  __PACKAGE__->authen->protected_runmodes(qw(one two three));

  # protect only runmodes that start with auth_
  __PACKAGE__->authen->protected_runmodes(qr/^auth_/);

  # protect all runmodes that *do not* start with public_
  __PACKAGE__->authen->protected_runmodes(qr/^(?!public_)/);

is_protected_runmode

This method accepts the name of a runmode, and will tell you if that runmode is a protected runmode (i.e. does a user need to be authenticated to access this runmode). Calling this function, will not itself generate cookies or session ids.

redirect_after_login

This method is be called during the prerun stage to redirect the user to the page that has been configured as the destination after a successful login. The location is determined as follows:

POST_LOGIN_RUNMODE

If the POST_LOGIN_RUNMODE config parameter is set, that run mode will be the chosen location.

POST_LOGIN_URL

If the above fails and the POST_LOGIN_URL config parameter is set, then there will be a 302 redirection to that location.

destination

If the above fails and there is a destination query parameter, which must a taint check against the DETAINT_URL_REGEXP config parameter, then there will be a 302 redirection to that location.

original destination

If all the above fail then there the originally requested page will be delivered.

redirect_to_login

This method is be called during the prerun stage if the current user is not logged in, and they are trying to access a protected runmode. It will redirect to the page that has been configured as the login page, based on the value of LOGIN_RUNMODE or LOGIN_URL If nothing is configured a simple login page will be automatically provided.

redirect_to_logout

This method is called during the prerun stage if the user has requested to be logged out. It will redirect to the page that has been configured as the logout page, based on the value of LOGOUT_RUNMODE or LOGOUT_URL If nothing is configured, the page will redirect to the website homepage.

setup_runmodes

This method is called during the prerun stage to register some custom runmodes that the Authentication plugin requires in order to function. Calling this function, will not itself generate cookies or session ids.

last_login

This will return return the time of the last login for this user

  my $last_login = $self->authen->last_login;

This function will initiate a session or cookie if one has not been created already.

last_access

This will return return the time of the last access for this user

  my $last_access = $self->authen->last_access;

This function will initiate a session or cookie if one has not been created already.

is_login_timeout

This will return true or false depending on whether the users login status just timed out

  $self->add_message('login session timed out') if $self->authen->is_login_timeout;

This function will initiate a session or cookie if one has not been created already.

is_authenticated

This will return true or false depending on the login status of this user

  assert($self->authen->is_authenticated); # The user should be logged in if we got here

This function will initiate a session or cookie if one has not been created already.

login_attempts

This method will return the number of failed login attempts have been made by this user since the last successful login. This is not a number that can be trusted, as it is dependent on the underlying store to be able to return the correct value for this user. For example, if the store uses a cookie based session, the user trying to login could delete their cookies, and hence get a new session which will not have any login attempts listed. The number will be cleared upon a successful login. This function will initiate a session or cookie if one has not been created already.

username

This will return the username of the currently logged in user, or undef if no user is currently logged in.

  my $username = $self->authen->username;

This function will initiate a session or cookie if one has not been created already.

is_new_login

This will return true or false depending on if this is a fresh login

  $self->log->info("New Login") if $self->authen->is_new_login;

This function will initiate a session or cookie if one has not been created already.

credentials

This method will return the names of the form parameters that will be looked for during a login. By default they are authen_username and authen_password, but these values can be changed by supplying the CREDENTIALS parameters in the configuration. Calling this function, will not itself generate cookies or session ids.

logout

This will attempt to logout the user. If during a request the Authentication module sees a parameter called 'authen_logout', it will automatically call this method to log out the user.

  $self->authen->logout();

This function will initiate a session or cookie if one has not been created already.

drivers

This method will return a list of driver objects that are used for verifying the login credentials. Calling this function, will not itself generate cookies or session ids.

store

This method will return a store object that is used to store information about the status of the authentication across multiple requests. This function will initiate a session or cookie if one has not been created already.

initialize

This does most of the heavy lifting for the Authentication plugin. It will check to see if the user is currently attempting to login by looking for the credential form fields in the query object. It will load the required driver objects and authenticate the user. It is OK to call this method multiple times as it checks to see if it has already been executed and will just return without doing anything if called multiple times. This allows us to call initialize as late as possible in the request so that no unnecessary work is done.

The user will be logged out by calling the logout() method if the login session has been idle for too long, if it has been too long since the last login, or if the login has timed out. If you need to know if a user was logged out because of a time out, you can call the is_login_timeout method.

If all goes well, a true value will be returned, although it is usually not necessary to check.

This function will initiate a session or cookie if one has not been created already.

display

This method will return the CGI::Application::Plugin::Authentication::Display object, creating and caching it if necessary.

login_box

This method will return the HTML for a login box that can be embedded into another page. This is the same login box that is used in the default authen_login runmode that the plugin provides.

This function will initiate a session or cookie if one has not been created already.

new

This method creates a new CGI::Application::Plugin::Authentication object. It requires as it's only parameter a CGI::Application object. This method should never be called directly, since the 'authen' method that is imported into the CGI::Application module will take care of creating the CGI::Application::Plugin::Authentication object when it is required. Calling this function, will not itself generate cookies or session ids.

instance

This method works the same way as 'new', except that it returns the same Authentication object for the duration of the request. This method should never be called directly, since the 'authen' method that is imported into the CGI::Application module will take care of creating the CGI::Application::Plugin::Authentication object when it is required. Calling this function, will not itself generate cookies or session ids.

CGI::Application CALLBACKS ^

prerun_callback

This method is a CGI::Application prerun callback that will be automatically registered for you if you are using CGI::Application 4.0 or greater. If you are using an older version of CGI::Application you will have to create your own cgiapp_prerun method and make sure you call this method from there.

 sub cgiapp_prerun {
    my $self = shift;

    $self->CGI::Application::Plugin::Authentication::prerun_callback();
 }

CGI::Application RUNMODES ^

authen_login_runmode

This runmode is provided if you do not want to create your own login runmode. It will display a simple login form for the user, which can be replaced by assigning RENDER_LOGIN a coderef that returns the HTML.

authen_dummy_redirect

This runmode is provided for convenience when an external redirect needs to be done. It just returns an empty string.

EXAMPLE ^

In a CGI::Application module:

  use base qw(CGI::Application);
  use CGI::Application::Plugin::AutoRunmode;
  use CGI::Application::Plugin::Session;
  use CGI::Application::Plugin::Authentication;

  __PACKAGE__->authen->config(
        DRIVER         => [ 'Generic', { user1 => '123' } ],
        STORE          => 'Session',
        LOGOUT_RUNMODE => 'start',
  );
  __PACKAGE__->authen->protected_runmodes(qr/^auth_/, 'one');

  sub start : RunMode {
    my $self = shift;

  }

  sub one : RunMode {
    my $self = shift;

    # The user will only get here if they are logged in
  }

  sub auth_two : RunMode {
    my $self = shift;

    # This is also protected because of the
    # regexp call to protected_runmodes above
  }

COMPATIBILITY WITH CGI::Application::Plugin::ActionDispatch ^

The prerun callback has been modified so that it will check for the presence of a prerun mode. This is for compatibility with CGI::Application::Plugin::ActionDispatch. This change should be considered experimental. It is necessary to load the ActionDispatch module so that the two prerun callbacks will be called in the correct order.

RECOMMENDED USAGE ^

CSS

The best practice nowadays is generally considered to be to not have CSS embedded in HTML. Thus it should be best to set LOGIN_FORM -> DISPLAY_CLASS to 'Basic'.

Post login destination

Of the various means of selecting a post login destination the most secure would seem to be POST_LOGIN_URL. The destination parameter could potentially be hijacked by hackers. The POST_LOGIN_RUNMODE parameter requires a hidden parameter that could potentially be hijacked.

Taint mode

Do run your code under taint mode. It should help protect your application against a number of attacks.

URL and username checking

Please set the DETAINT_URL_REGEXP and DETAINT_USERNAME_REGEXP parameters as tightly as possible. In particular you should prevent the destination parameter being used to redirect authenticated users to external sites; unless of course that is what you want in which case that site should be the only possible external site.

The login form

The HTML currently generated does not seem to be standards compliant as per RT bug 58023. Also the default login form includes hidden forms which could conceivably be hijacked. Set LOGIN_FORM -> DISPLAY_CLASS to 'Basic' to fix this.

TODO ^

There are lots of things that can still be done to improve this plugin. If anyone else is interested in helping out feel free to dig right in. Many of these things don't need my input, but if you want to avoid duplicated efforts, send me a note, and I'll let you know of anyone else is working in the same area.

review the code for security bugs and report
complete the separation of presentation and logic
write a tutorial
build more Drivers (Class::DBI, LDAP, Radius, etc...)
Add support for method attributes to identify runmodes that require authentication
finish the test suite
provide more example code
clean up the documentation
build a DB driver that builds it's own table structure. This can be used by people that don't have their own user database to work with, and could include a simple user management application.

BUGS ^

This is alpha software and as such, the features and interface are subject to change. So please check the Changes file when upgrading.

Some of the test scripts appear to be incompatible with versions of Devel::Cover later than 0.65.

SEE ALSO ^

CGI::Application, perl(1)

AUTHOR ^

Author: Cees Hek <ceeshek@gmail.com>; Co-maintainer: Nicholas Bamber <nicholas@periapt.co.uk>.

CREDITS ^

Thanks to SiteSuite for funding the development of this plugin and for releasing it to the world.

Thanks to Christian Walde for suggesting changes to fix the incompatibility with CGI::Application::Plugin::ActionDispatch and for help with github.

Thanks to Alexandr Ciornii for pointing out some typos.

LICENCE AND COPYRIGHT ^

Copyright (c) 2005, SiteSuite. All rights reserved. Copyright (c) 2010, Nicholas Bamber. (Portions of the code).

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The background images in the default login forms are used courtesy of www.famfamfam.com. Those icons are issued under the Creative Commons Attribution 3.0 License. Those icons are copyrighted 2006 by Mark James <mjames at gmail dot com>

DISCLAIMER OF WARRANTY ^

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

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