PHP Manual: Runkit Sandbox Class -- PHP Virtual Machine

Description

Instantiating the Runkit_Sandbox class creates a new thread with its own scope and program stack. Using a set of options passed to the constructor, this environment may be restricted to a subset of what the primary interpreter can do and provide a safer environment for executing user supplied code.

Note: Sandbox support (required for runkit_lint, runkit_lint_file, and the Runkit_Sandbox class) is only available as of PHP 5.1.0 or specially patched versions of PHP 5.0, and requires that thread safety be enabled. See the README file included in the runkit package for more information.

Constructor

void Runkit_Sandbox::__construct ([ array $options ] )

options is an associative array containing any combination of the special ini options listed below.

safe_mode: If the outer script which is instantiating the Runkit_Sandbox class is configured with safe_mode = off, then safe_mode may be turned on for the sandbox environment. This setting can not be used to disable safe_mode when it's already enabled in the outer script.
safe_mode_gid: If the outer script which is instantiating the Runkit_Sandbox class is configured with safe_mode_gid = on, then safe_mode_gid may be turned off for the sandbox environment. This setting can not be used to enable safe_mode_gid when it's already disabled in the outer script.
safe_mode_include_dir: If the outer script which is instantiating the Runkit_Sandbox class is configured with a safe_mode_include_dir, then a new safe_mode_include_dir may be set for sandbox environments below the currently defined value. safe_mode_include_dir may also be cleared to indicate that the bypass feature is disabled. If safe_mode_include_dir was blank in the outer script, but safe_mode was not enabled, then any arbitrary safe_mode_include_dir may be set while turning safe_mode on.
open_basedir: open_basedir may be set to any path below the current setting of open_basedir. If open_basedir is not set within the global scope, then it is assumed to be the root directory and may be set to any location.
allow_url_fopen: Like safe_mode, this setting can only be made more restrictive, in this case by setting it to FALSE when it is previously set to TRUE
disable_functions: Comma separated list of functions to disable within the sandbox sub-interpreter. This list need not contain the names of the currently disabled functions, they will remain disabled whether listed here or not.
disable_classes: Comma separated list of classes to disable within the sandbox sub-interpreter. This list need not contain the names of the currently disabled classes, they will remain disabled whether listed here or not.
runkit.superglobal: Comma separated list of variables to be treated as superglobals within the sandbox sub-interpreter. These variables will be used in addition to any variables defined internally or through the global runkit.superglobal setting.
runkit.internal_override: Ini option runkit.internal_override may be disabled (but not re-enabled) within sandboxes.

Example #1 Instantiating a restricted sandbox


<?php
$options = array(
  'safe_mode'=>true,
  'open_basedir'=>'/var/www/users/jdoe/',
  'allow_url_fopen'=>'false',
  'disable_functions'=>'exec,shell_exec,passthru,system',
  'disable_classes'=>'myAppClass');
$sandbox = new Runkit_Sandbox($options);
/* Non-protected ini settings may set normally */
$sandbox->ini_set('html_errors',true);
?>

Accessing Variables

All variables in the global scope of the sandbox environment are accessible as properties of the sandbox object. The first thing to note is that because of the way memory between these two threads is managed, object and resource variables can not currently be exchanged between interpreters. Additionally, all arrays are deep copied and any references will be lost. This also means that references between interpreters are not possible.

Example #2 Working with variables in a sandbox


<?php
$sandbox = new Runkit_Sandbox();

$sandbox->foo = 'bar';
$sandbox->eval('echo "$foo\n"; $bar = $foo . "baz";');
echo "{$sandbox->bar}\n";
if (isset($sandbox->foo)) unset($sandbox->foo);
$sandbox->eval('var_dump(isset($foo));');
?>

The above example will output:

bar
barbaz
bool(false)

Calling PHP Functions

Any function defined within the sandbox may be called as a method on the sandbox object. This also includes a few pseudo-function language constructs: eval, include, include_once, require, require_once, echo, print, die, and exit.

Example #3 Calling sandbox functions


<?php
$sandbox = new Runkit_Sandbox();

echo $sandbox->str_replace('a','f','abc');
?>

The above example will output:

fbc

When passing arguments to a sandbox function, the arguments are taken from the outer instance of PHP. If you wish to pass arguments from the sandbox's scope, be sure to access them as properties of the sandbox object as illustrated above.

Example #4 Passing arguments to sandbox functions


<?php
$sandbox = new Runkit_Sandbox();

$foo = 'bar';
$sandbox->foo = 'baz';
echo $sandbox->str_replace('a',$foo,'a');
echo $sandbox->str_replace('a',$sandbox->foo,'a');
?>

The above example will output:

bar
baz

Changing Sandbox Settings

As of runkit version 0.5, certain Sandbox settings may be modified on the fly using ArrayAccess syntax. Some settings, such as active are read-only and meant to provide status information. Other settings, such as output_handler may be set and read much like a normal array offset. Future settings may be write-only, however no such settings currently exist.

**Sandbox Settings / Status Indicators**
Setting	Type	Purpose	Default
active	Boolean (Read Only)	`TRUE` if the Sandbox is still in a usable state, `FALSE` if the request is in bailout due to a call to die(), exit(), or because of a fatal error condition.	`TRUE` (Initial)
output_handler	Callback	When set to a valid callback, all output generated by the Sandbox instance will be processed through the named function. Sandbox output handlers follow the same calling conventions as the system-wide output handler.	None
parent_access	Boolean	May the sandbox use instances of the Runkit_Sandbox_Parent class? Must be enabled for other Runkit_Sandbox_Parent related settings to work.	`FALSE`
parent_read	Boolean	May the sandbox read variables in its parent's context?	`FALSE`
parent_write	Boolean	May the sandbox modify variables in its parent's context?	`FALSE`
parent_eval	Boolean	May the sandbox evaluate arbitrary code in its parent's context? DANGEROUS	`FALSE`
parent_include	Boolean	May the sandbox include php code files in its parent's context? DANGEROUS	`FALSE`
parent_echo	Boolean	May the sandbox echo data in its parent's context effectively bypassing its own output_handler?	`FALSE`
parent_call	Boolean	May the sandbox call functions in its parent's context?	`FALSE`
parent_die	Boolean	May the sandbox kill its own parent? (And thus itself)	`FALSE`
parent_scope	Integer	What scope will parental property access look at? 0 == Global scope, 1 == Calling scope, 2 == Scope preceding calling scope, 3 == The scope before that, etc..., etc...	0 (Global)
parent_scope	String	When parent_scope is set to a string value, it refers to a named array variable in the global scope. If the named variable does not exist at the time of access it will be created as an empty array. If the variable exists but it not an array, a dummy array will be created containing a reference to the named global variable.