Advanced file upload bypass techniques
This lab demonstrates advanced file upload bypass techniques used to circumvent modern security filters and protections. These techniques include obfuscation, encoding, alternative execution methods, and sophisticated bypass methods.
Objective: Use advanced techniques to bypass sophisticated security filters and upload malicious files.
// Vulnerable: Advanced filters that can be bypassed
function process_advanced_file_upload($file) {
$allowed_extensions = ['jpg', 'jpeg', 'png', 'gif', 'txt', 'pdf'];
$allowed_mime_types = ['image/jpeg', 'image/png', 'image/gif', 'text/plain'];
$max_file_size = 5 * 1024 * 1024; // 5MB
$dangerous_patterns = [' $max_file_size) {
return false;
}
// Check extension
$file_extension = strtolower(pathinfo($file['name'], PATHINFO_EXTENSION));
if (!in_array($file_extension, $allowed_extensions)) {
return false;
}
// Check MIME type
if (!in_array($file['type'], $allowed_mime_types)) {
return false;
}
// Check file content for dangerous patterns
$file_content = file_get_contents($file['tmp_name']);
foreach ($dangerous_patterns as $pattern) {
if (stripos($file_content, $pattern) !== false) {
return false;
}
}
// Still vulnerable to advanced bypass techniques
return move_uploaded_file($file['tmp_name'], $file_path);
}
The following are filtered:
Try these advanced bypass methods:
webshell.php.jpg - Double extensionwebshell.php%00.jpg - Null byte injectionwebshell.php;.jpg - Semicolon bypasswebshell.PHP.JPG - Case variationNo files uploaded yet.
Use these advanced techniques to bypass sophisticated security filters: