Host Header Injection in Laravel: Risks and Prevention

Detailed explanation and defense strategies of host header injection vulnerability in Laravel

This article will delve into Host Header Injection this serious web application vulnerability, including applications based on the Laravel framework. This vulnerability allows attackers to manipulate the host header in HTTP requests, resulting in security risks such as cache poisoning, password reset attacks, and open redirects. We will analyze its risks in detail, provide examples, and provide corresponding defense strategies.

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What is host header injection?

Host header injection occurs when a web application blindly trusts the host header provided in the HTTP request. This vulnerability could lead to the following malicious actions:

• Redirect users to malicious websites.
• Tampering with the password reset link.
• Control server behavior.

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Utilization of host header injection in Laravel

There is a security risk if a Laravel application relies on the host header in key decisions without validating it. Let's look at an example.

Vulnerable code examples:

<code>// routes/web.php

use Illuminate\Support\Facades\Mail;

Route::get('/send-reset-link', function () {
    $user = User::where('email', 'example@example.com')->first();

    if ($user) {
        $resetLink = 'http://' . $_SERVER['HTTP_HOST'] . '/reset-password?token=' . $user->reset_token;

        // 发送重置链接
        Mail::to($user->email)->send(new \App\Mail\ResetPassword($resetLink));

        return "密码重置链接已发送。";
    }

    return "用户未找到。";
});</code>

In this example, the application uses the host header directly to generate the password reset link. An attacker could exploit this vulnerability by crafting a malicious request:

<code>GET /send-reset-link HTTP/1.1
Host: malicious.com</code>

The generated reset link will point to malicious.com, potentially compromising user security.

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Defense against host header injection in Laravel

• Verify host header: Laravel provides a APP_URLenvironment variable that can be used to ensure the validity of the host header:

<code>// routes/web.php

Route::get('/send-reset-link', function () {
    $user = User::where('email', 'example@example.com')->first();

    if ($user) {
        $resetLink = config('app.url') . '/reset-password?token=' . $user->reset_token;

        // 发送重置链接
        Mail::to($user->email)->send(new \App\Mail\ResetPassword($resetLink));

        return "密码重置链接已发送。";
    }

    return "用户未找到。";
});</code>

• Restrict trusted hosts: Use Laravel's trustedproxies middleware to restrict requests to trusted hosts. Update your config/trustedproxy.php file:

<code>return [
    'proxies' => '*',
    'headers' => [
        Request::HEADER_X_FORWARDED_ALL,
        Request::HEADER_FORWARDED,
    ],
    'host' => ['example.com'], // 添加可信主机
];</code>

• Security configuration: Make sure the .env settings in your APP_URL file are correct:

<code>APP_URL=https://yourdomain.com</code>

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Test for vulnerabilities with free tools

You can use our free website security scanner to test for host header injection vulnerabilities.

Screenshot of the free tool webpage where you can access the security assessment tool

Additionally, after using our tool to conduct a vulnerability assessment to check for website vulnerabilities, you can generate a detailed report to understand the security status of your application.

A sample vulnerability assessment report generated using our free tool, providing insights into possible vulnerabilities

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Conclusion

Host header injection is a critical vulnerability that can compromise the security of Laravel applications. You can protect your application by validating input, limiting trusted hosts, and using the correct configuration.

Test your website today with our Website Security Checker and take the first step towards staying safe online.

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