Fix TypeError for non-array static_classes in Security policy

changelog/static-classes-none-typeerror.md

@@ -0,0 +1 @@
+- Fixed a `TypeError` on PHP 8 when `Security::$static_classes` was set to a non-array value (e.g. the string `'none'`) to disable static class access; any non-array value now cleanly denies access. Use `Security::$static_classes = null` to disable access to all static classes.

src/Security.php

@@ -52,7 +52,7 @@ class Security {
 	/**
 	 * This is an array of trusted static classes.
 	 * If empty access to all static classes is allowed.
-	 * If set to 'none' none is allowed.
+	 * To disable access to all static classes set $static_classes = null.
 	 *
 	 * @var array
 	 */
@@ -206,7 +206,11 @@ public function __construct(Smarty $smarty) {
 	 * @return boolean                 true if class is trusted
 	 */
 	public function isTrustedStaticClass($class_name, $compiler) {
-		if (isset($this->static_classes)
+		// Only an array enables access: an empty array allows all classes, a
+		// populated array is an allowlist. Any other value (null, or the
+		// documented "none") denies all. Using is_array() rather than isset()
+		// also avoids a PHP 8 TypeError from passing a non-array to in_array().
+		if (is_array($this->static_classes)
 			&& (empty($this->static_classes) || in_array($class_name, $this->static_classes))
 		) {
 			return true;

tests/UnitTests/SecurityTests/SecurityTest.php

@@ -243,6 +243,39 @@ public function testNotTrustedStaticClassSmartyVar()
 		$this->smarty->fetch('string:{$smarty.template_object::square(5)}');
 	}
 
+	/**
+	 * The default (empty array) allows access to all static classes. Documents
+	 * the backwards-compatible behaviour.
+	 */
+	public function testStaticClassAllowedByDefault()
+	{
+		$this->smarty->security_policy->static_classes = array();
+		$this->assertEquals('25', $this->smarty->fetch('string:{mysecuritystaticclass::square(5)}'));
+	}
+
+	/**
+	 * Setting static_classes to null disables access to all static classes.
+	 */
+	public function testStaticClassDeniedWhenNull()
+	{
+		$this->expectException(\Smarty\Exception::class);
+		$this->expectExceptionMessage("access to static class 'mysecuritystaticclass' not allowed by security setting");
+		$this->smarty->security_policy->static_classes = null;
+		$this->smarty->fetch('string:{mysecuritystaticclass::square(5)}');
+	}
+
+	/**
+	 * Regression: a non-array value such as the string 'none' must deny access
+	 * cleanly instead of raising a PHP 8 TypeError from in_array().
+	 */
+	public function testStaticClassDeniedWhenNonArray()
+	{
+		$this->expectException(\Smarty\Exception::class);
+		$this->expectExceptionMessage("access to static class 'mysecuritystaticclass' not allowed by security setting");
+		$this->smarty->security_policy->static_classes = 'none';
+		$this->smarty->fetch('string:{mysecuritystaticclass::square(5)}');
+	}
+
 	public function testChangedTrustedDirectory()
 	{
 		$this->smarty->security_policy->secure_dir = array(