NAME
CGI::Application::Plugin::Authentication - Authentication framework for
CGI::Application
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 dependant 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 dependant 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.
login_styles
This method returns a style-sheet that can be used for the login box
that the plugin provides. The login box automatically includes these
default styles in the page unless you set the LOGIN_FORM =>
INCLUDE_STYLESHEET option to 0. The colours used in the returned styles
can be customized by providing colour options to LOGIN_FORM
configuration parameter.
Calling this function, will not itself generate cookies or session ids.
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 <
[email protected]>; Co-maintainer: Nicholas Bamber
<
[email protected]>.
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.
