Add headers validator

app/controllers/api/functions.php

@@ -10,6 +10,7 @@ use Appwrite\Event\Usage;
 use Appwrite\Event\Validator\FunctionEvent;
 use Appwrite\Extend\Exception;
 use Appwrite\Extend\Exception as AppwriteException;
+use Appwrite\Functions\Validator\Headers;
 use Appwrite\Messaging\Adapter\Realtime;
 use Appwrite\Platform\Tasks\ScheduleExecutions;
 use Appwrite\Task\Validator\Cron;
@@ -1628,7 +1629,7 @@ App::post('/v1/functions/:functionId/executions')
         }
 
         // 'headers' validator
-        $validator = new Assoc();
+        $validator = new Headers();
         if (!$validator->isValid($headers)) {
             throw new Exception($validator->getDescription(), 400);
         }

src/Appwrite/Functions/Validator/Headers.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace Appwrite\Functions\Validator;
+
+use Utopia\Validator;
+
+/**
+ * Headers.
+ *
+ * Validates user provided headers
+ */
+class Headers extends Validator
+{
+    protected bool $allowEmpty;
+
+    public function __construct(bool $allowEmpty = true)
+    {
+        $this->allowEmpty = $allowEmpty;
+    }
+
+    /**
+     * Get Description.
+     *
+     * Returns validator description
+     *
+     * @return string
+     */
+    public function getDescription(): string
+    {
+        return 'Invalid header format. Header keys can only contain alphanumeric characters, underscores, and hyphens. Header keys cannot start with "x-appwrite-" prefix.';
+    }
+
+    /**
+     * Is valid.
+     *
+     * @param mixed $value
+     *
+     * @return bool
+     */
+    public function isValid($value): bool
+    {
+        if ($this->allowEmpty && empty($value)) {
+            return true;
+        }
+
+        if (\is_string($value)) {
+            $value = \json_decode($value, true);
+        }
+
+        if (\json_last_error() == JSON_ERROR_NONE) {
+            if (\is_array($value)) {
+                foreach ($value as $key => $val) {
+                    // Check for invalid characters in key and value
+                    if (!preg_match('/^[a-zA-Z0-9_-]+$/', $key)) {
+                        return false;
+                    }
+                    // Check for x-appwrite- prefix
+                    if (0 === strpos($key, 'x-appwrite-')) {
+                        return false;
+                    }
+                }
+            }
+        }
+        return \json_last_error() == JSON_ERROR_NONE;
+    }
+
+    /**
+     * Is array
+     *
+     * Function will return true if object is array.
+     *
+     * @return bool
+     */
+    public function isArray(): bool
+    {
+        return false;
+    }
+
+    /**
+     * Get Type
+     *
+     * Returns validator type.
+     *
+     * @return string
+     */
+    public function getType(): string
+    {
+        return self::TYPE_OBJECT;
+    }
+}