NAME

       Text::MicroMason::Safe - Compile all Templates in a Safe Compartment

SYNOPSIS

       Instead of using this class directly, pass its name to be mixed in:

         use Text::MicroMason;
         my $mason = Text::MicroMason->new( -Safe );

       Use the standard compile and execute methods to parse and evaluate templates:

         print $mason->compile( text=>$template )->( @%args );
         print $mason->execute( text=>$template, @args );

       Safe usage restricts templates from accessing your files or data:

         print $mason->execute( text=>"<% qx! cat /etc/passwd ! %>" ); # dies

         print $mason->execute( text=>"The time is <% time() %>." ); # dies

DESCRIPTION

       This package adds support for Safe compartments to MicroMason, allowing you to  restrict
       the operations that a template can perform.

       By default, these safe calls prevent the code in a template from performing any system
       activity or accessing any of your other Perl code.  Violations may result in either
       compile-time or run-time errors, so make sure you are using an eval block or the
       CatchErrors trait to catch exceptions.

         use Text::MicroMason;
         my $mason = Text::MicroMason->new( -Safe );

         $result = eval { $mason->execute( text => $template ) };

       Caution: Although this appears to provide a significant amount of security for untrusted
       templates, please take this with a grain of salt. A bug in either this module or in the
       core Safe module could allow a clever attacker to defeat the protection. At least one bug
       in the Safe module has been found and fixed in years past, and there could be others.

   Supported Attributes
       safe
           Optional reference to a Safe compartment. If you do not provide this, one is generated
           for you.

           To enable some operations or share variables or functions with the template code,
           create a Safe compartment and configure it before passing it in as the value of the
           "safe" attribute:

             $safe = Safe->new();
             $safe->permit('time');
             $safe->share('$foo');

             $mason = Text::MicroMason->new( -Safe, safe => $safe );

             $result = eval { $mason->execute( text => $template ) };

       safe_methods
           IMPORTANT NOTE: The "safe_methods" parameter is deprecated and will be removed in
           future versions of Text::MicroMason (unless a Safe and future-proof implementation can
           be found).  If you use this parameter, you will receive a warning via carp:

           "* WARNING: safe_methods is deprecated; please see the pod"

           This parameter works correctly with sufficiently old versions of the Safe module
           (prior to the release of perl 5.12.1), but modern versions of Safe make it impossible
           for a Safe compartment to run any code outside the compartment.  Even with the object
           shared within the Safe compartment, there is currently no known way to call methods on
           it without defining the whole class within the compartment (which isn't safe).

           If anyone has an appropriately safe solution that will allow "safe_methods" to work,
           please submit a patch to the module maintainer.  Also see t/32-safe.t for tests
           related to "safe_methods" that are currently being skipped.

           The following pod is provided for legacy purposes only.  It is strongly recommended
           that you do not use this method.  It is no longer allowed to call methods from within
           a "Safe" template, because it isn't actually safe.

           A space-separated string of methods names to be supported by the Safe::Facade.

           To control which Mason methods are available within the template, pass a
           "safe_methods" argument to new() followed by the method names in a space-separated
           string.

           For example, to allow templates to include other templates, using $m->execute or the
           "<& file &>" include syntax, you would need to allow the execute method. We'll also
           load the TemplateDir mixin with strict_root on to prevent inclusion of templates from
           outside the current directory.

             # safe_methods is DEPRECATED, please see above
             $mason = Text::MicroMason->new( -Safe, safe_methods => 'execute',
                                             -TemplateDir, strict_root => 1 );

           If you're combining this with the Filters mixin, you'll also need to allow calls to
           the filter method; to allow multiple methods, join their names with spaces:

             # safe_methods is DEPRECATED, please see above
             $mason = Text::MicroMason->new( -Safe, safe_methods => 'execute filter',
                                             -TemplateDir, strict_root => 1,
                                             -Filters );

   Private Methods
       eval_sub()
           Instead of the eval() used by the base class, this calls reval() on a Safe
           compartment.

       safe_compartment()
           Returns the Safe compartment passed by the user or generates a new one.

       safe_facade()
           Generates an instance of the Safe::Facade equipped with only the methods listed in the
           safe_methods attribute.

   Private Safe::Facade class
       Code compiled in a Safe compartment only has access to a limited version of the template
       compiler in the $m variable, and can not make changes to the attributes of the real
       MicroMason object. This limited object is an instance of the
       Text::MicroMason::Safe::Facade class and can only perform certain pre-defined methods.

       new()
           Creates a new hash-based instance mapping method names to subroutine references.

       facade_method()
           Calls a named method by looking up the corresponding subroutine and calling it.

       AUTOLOAD()
           Generates wrapper methods that call the facade_method() for any lowercase method name.

SEE ALSO

       For an overview of this templating framework, see Text::MicroMason.

       This is a mixin class intended for use with Text::MicroMason::Base.

       For distribution, installation, support, copyright and license information, see
       Text::MicroMason::Docs::ReadMe.