feature #3025 Add the possibility to register classes/interface as being safe (fabpot)

This PR was squashed before being merged into the 2.x branch (closes #3025).

Discussion
----------

Add the possibility to register classes/interface as being safe

closes #2548

To avoid a too big performance impact on the escaper, we aggressively cache the safe classes, which means that changing the. configuration at runtime is not possible (and having different ones on 2 Twig instances is not possible either, this is really *globally* configured).

Commits
-------

fe6503fe -
b18733bc added the possibility to register classes/interfaces as being safe for the escaper

CHANGELOG

@@ -1,5 +1,6 @@
 * 2.11.0 (2019-XX-XX)
 
+ * added the possibility to register classes/interfaces as being safe for the escaper ("EscaperExtension::addSafeClass()")
  * deprecated CoreExtension::setEscaper() and CoreExtension::getEscapers() in favor of the same methods on EscaperExtension
  * macros are now auto-imported in the template they are defined (under the ``_self`` variable)
  * added support for macros on "is defined" tests

doc/api.rst

@@ -415,6 +415,24 @@ The escaping rules are implemented as follows:
         {% set text = "Twig<br />" %}
         {{ foo ? text|escape : "<br />Twig" }} {# the result of the expression won't be escaped #}
 
+* Objects with a ``__toString`` method are converted to strings and
+  escaped. You can mark some classes and/or interfaces as being safe for some
+  strategies via ``EscaperExtension::addSafeClass()``:
+
+  .. code-block:: twig
+
+        // mark object of class Foo as safe for the HTML strategy
+        $escaper->addSafeClass('Foo', ['html']);
+
+        // mark object of interface Foo as safe for the HTML strategy
+        $escaper->addSafeClass('FooInterface', ['html']);
+
+        // mark object of class Foo as safe for the HTML and JS strategies
+        $escaper->addSafeClass('Foo', ['html', 'js']);
+
+        // mark object of class Foo as safe for all strategies
+        $escaper->addSafeClass('Foo', ['all']);
+
 * Escaping is applied before printing, after any other filter is applied:
 
   .. code-block:: twig

src/Extension/EscaperExtension.php

@@ -20,6 +20,12 @@ final class EscaperExtension extends AbstractExtension
     private $defaultStrategy;
     private $escapers = [];
 
+    /** @internal */
+    public $safeClasses = [];
+
+    /** @internal */
+    public $safeLookup = [];
+
     /**
      * @param string|false|callable $defaultStrategy An escaping strategy
      *
@@ -104,6 +110,28 @@ final class EscaperExtension extends AbstractExtension
     {
         return $this->escapers;
     }
+
+    public function setSafeClasses(array $safeClasses = [])
+    {
+        $this->safeClasses = [];
+        $this->safeLookup = [];
+        foreach ($safeClasses as $class => $strategies) {
+            $this->addSafeClass($class, $strategies);
+        }
+    }
+
+    public function addSafeClass(string $class, array $strategies)
+    {
+        $class = ltrim($class, '\\');
+        if (!isset($this->safeClasses[$class])) {
+            $this->safeClasses[$class] = [];
+        }
+        $this->safeClasses[$class] = array_merge($this->safeClasses[$class], $strategies);
+
+        foreach ($strategies as $strategy) {
+            $this->safeLookup[$strategy][$class] = true;
+        }
+    }
 }
 
 class_alias('Twig\Extension\EscaperExtension', 'Twig_Extension_Escaper');
@@ -148,6 +176,25 @@ function twig_escape_filter(Environment $env, $string, $strategy = 'html', $char
 
     if (!\is_string($string)) {
         if (\is_object($string) && method_exists($string, '__toString')) {
+            if ($autoescape) {
+                $c = \get_class($string);
+                $ext = $env->getExtension(EscaperExtension::class);
+                if (!isset($ext->safeClasses[$c])) {
+                    $ext->safeClasses[$c] = [];
+                    foreach (class_parents($string) + class_implements($string) as $class) {
+                        if (isset($ext->safeClasses[$class])) {
+                            $ext->safeClasses[$c] = array_unique(array_merge($ext->safeClasses[$c], $ext->safeClasses[$class]));
+                            foreach ($ext->safeClasses[$class] as $s) {
+                                $ext->safeLookup[$s][$c] = true;
+                            }
+                        }
+                    }
+                }
+                if (isset($ext->safeLookup[$strategy][$c]) || isset($ext->safeLookup['all'][$c])) {
+                    return (string) $string;
+                }
+            }
+
             $string = (string) $string;
         } elseif (\in_array($strategy, ['html', 'js', 'css', 'html_attr', 'url'])) {
             return $string;

test/Twig/Tests/Extension/EscaperTest.php

@@ -362,9 +362,42 @@ class Twig_Tests_Extension_EscaperTest extends \PHPUnit\Framework\TestCase
     {
         twig_escape_filter(new Environment($this->getMockBuilder(LoaderInterface::class)->getMock()), 'foo', 'bar');
     }
+
+    /**
+     * @dataProvider provideObjectsForEscaping
+     */
+    public function testObjectEscaping(string $escapedHtml, string $escapedJs, array $safeClasses)
+    {
+        $obj = new Twig_Tests_Extension_TestClass();
+        $twig = new Environment($this->getMockBuilder('\Twig\Loader\LoaderInterface')->getMock());
+        $twig->getExtension('\Twig\Extension\EscaperExtension')->setSafeClasses($safeClasses);
+        $this->assertSame($escapedHtml, twig_escape_filter($twig, $obj, 'html', null, true));
+        $this->assertSame($escapedJs, twig_escape_filter($twig, $obj, 'js', null, true));
+    }
+
+    public function provideObjectsForEscaping()
+    {
+        return [
+            ['&lt;br /&gt;', '<br />', ['\Twig_Tests_Extension_TestClass' => ['js']]],
+            ['<br />', '\u003Cbr\u0020\/\u003E', ['\Twig_Tests_Extension_TestClass' => ['html']]],
+            ['&lt;br /&gt;', '<br />', ['\Twig_Tests_Extension_SafeHtmlInterface' => ['js']]],
+            ['<br />', '<br />', ['\Twig_Tests_Extension_SafeHtmlInterface' => ['all']]],
+        ];
+    }
 }
 
 function foo_escaper_for_test(Environment $twig, $string, $charset)
 {
     return $string.$charset;
 }
+
+interface Twig_Tests_Extension_SafeHtmlInterface
+{
+}
+class Twig_Tests_Extension_TestClass implements Twig_Tests_Extension_SafeHtmlInterface
+{
+    public function __toString()
+    {
+        return '<br />';
+    }
+}