Unrestricted File Upload in Laravel: Prevention & Insights

What Is an Unrestricted File Upload Vulnerability?

Unrestricted file upload occurs when a web application allows users to upload files without proper validation, leading to potential threats such as:

1. Uploading malicious scripts.

2. Executing remote code.

3. Overwriting existing server files.

A Laravel Example of Vulnerable File Upload Code

Here’s an example of insecure file upload code:

if ($request->hasFile('file')) {  

    $file = $request->file('file');  

    $file->move('uploads', $file->getClientOriginalName());  

}

The above code:

• Does not validate file type or size.

• Directly uploads files to the server.

• Risks executing malicious code, e.g., .php files disguised as images.

How to Secure File Uploads in Laravel

To prevent unrestricted file upload vulnerabilities:

1. Validate File Type

Always ensure that only specific file types are allowed.

$request->validate([  

    'file' => 'required|file|mimes:jpeg,png,pdf|max:2048',  

]);  

2. Rename Uploaded Files

Generate random names to prevent file overwriting.

$fileName = time() . '_' . $file->getClientOriginalName();  

$file->storeAs('uploads', $fileName);  

3. Store Files Outside the Public Directory

To prevent direct execution, store files in secure directories.

$filePath = $file->store('private/uploads');  

A Website Vulnerability Assessment Example

Here’s a real-life example of how our Free Website Security Checker Tool identified unrestricted file upload vulnerabilities in a client's website. The vulnerability allowed .php files to execute arbitrary code. The report highlighted the issue and provided actionable solutions to secure the website.