關於 PHP 程式碼安全性您應該了解的內容

在 Web 開發方面，PHP 是一種廣泛使用的腳本語言。隨著 PHP 的流行，了解與 PHP 相關的潛在安全風險以及緩解這些風險的措施至關重要。無論您使用 WordPress 部署 CMS 應用程式還是使用 Laravel PHP 框架建立企業應用程序，PHP 安全性的重要性以及一些值得注意的 PHP 解釋器漏洞的業務影響對於開發人員來說至關重要。

為什麼防範 PHP 安全漏洞很重要？由於 PHP 的流行和廣泛使用，PHP 經常成為駭客和惡意實體的目標。由於各種原因，例如不良的編碼實踐、缺乏對使用者輸入的清理以及過時的版本，安全漏洞可能會蔓延。

例如，讓我們考慮在 SQL 查詢中使用未經淨化的使用者輸入的場景。這可能會導致 SQL 注入，這是一個常見的漏洞。

$id = $_GET['id'];
$sql = "SELECT * FROM users WHERE id = $id";

在給定的程式碼中，惡意使用者可以操縱URL中的id參數來執行SQL注入。為了防止這種情況，清理使用者輸入至關重要，例如使用 mysqli_real_escape_string 或準備好的語句：

$id = mysqli_real_escape_string($conn, $_GET['id']);
$sql = "SELECT * FROM users WHERE id = $id";

PHP 應用程式中的安全漏洞可能會對您的業務產生深遠的影響。它們可能會導致資料洩露，進而可能因不遵守 GDPR 和 CCPA 等資料保護法規而導致巨額​​罰款。違規行為也會削弱客戶的信任，導致業務損失。此外，修復漏洞的補救成本可能很高，特別是如果它們是在開發生命週期的後期發現的，這就是為什麼從專案一開始就將安全性作為優先事項至關重要的原因。

相關常見問題

如何保護我的 PHP 應用程式免受漏洞影響？

始終驗證和清理使用者輸入。使用具有參數化查詢的預先準備語句來防止 SQL 注入。使用最新版本的 PHP 及其框架，因為它們附帶針對已知漏洞的安全性修補程式。定期使用 Snyk 等工具掃描程式碼和應用程式依賴項以及雲端基礎架構配置是否存在漏洞。遵循安全編碼實踐。

為什麼 PHP 安全很重要？

PHP 安全性至關重要，因為易受攻擊的 PHP 應用程式可能會導致資料外洩、失去客戶信任和監管罰款。由於 PHP 經常用於開發 Web 應用程序，因此它經常成為攻擊者的攻擊目標。確保您的 PHP 程式碼安全有助於保護您的使用者資料和您的業務。

什麼是 PHP 漏洞掃描器？

PHP 漏洞掃描器是一種自動掃描 PHP 程式碼中已知安全漏洞的工具。例如 Snyk 和 Composer 的內建安全檢查器。這些工具可以幫助您識別並修復 PHP 應用程式中的安全性問題。

什麼是 PHP 安全建議？

PHP 安全公告是關於 PHP 元件中的安全漏洞的公開公告。它提供了有關該漏洞、其潛在影響以及修復方法的詳細資訊。 PHP.net 和其他 PHP 相關網站經常發布這些建議。 Snyk 也維護一個基於 Composer 套件管理器的 PHP 安全建議資料庫。

常見的 PHP 安全漏洞

讓我們來探索一些常見的 PHP 安全漏洞，並了解有用的開發人員安全資源來緩解這些漏洞。

Cookie 和會話管理

Cookie 和會話是 Web 開發的基本面，使我們能夠在請求之間維護狀態。然而，如果管理不當，它們可能會帶來嚴重的安全缺陷。

在 PHP 中，尤其是在使用像 Laravel 這樣的 Web 框架時，在管理驗證時保護 cookie 和會話資料非常重要。這裡有一些提示：

• 總是使用安全的、僅限 HTTP 的 cookie。
• 優先將 SameSite 屬性設為 Lax 或 Strict，以防止跨站請求偽造 (CSRF) 攻擊。
• 登入或變更密碼後重新產生會話 ID，以避免會話固定攻擊。

在 Laravel 中，您可以在 config/session.php 檔案中設定這些設定：

'cookie' => env(
    'SESSION_COOKIE',
    Str::slug(env('APP_NAME', 'laravel'), '_').'_session'
),
'cookie_secure' => env('SESSION_SECURE_COOKIE', null),
'cookie_same_site' => 'lax',

請參閱更多有關保護 Laravel 應用程式的 Web 安全指南，以協助防範 PHP 安全漏洞。

SQL注入

SQL 注入是一種程式碼注入技術，攻擊者利用該技術來利用 Web 應用程式的資料庫查詢中的漏洞。它可能導致未經授權存取敏感資料以及潛在的資料操縱或刪除。

考慮以下易受攻擊的 PHP 程式碼：

$id = $_GET['id'];
$result = mysqli_query($con, "SELECT * FROM users WHERE id = $id");

An attacker can manipulate the id parameter in the URL to alter the SQL query. To prevent this, use prepared statements:

$stmt = $conn->prepare("SELECT * FROM users WHERE id = ?");
$stmt->bind_param("s", $_GET['id']);
$stmt->execute();

For more on SQL injection and PHP security, check out this free PHP security education.

Code injection

Code injection is another common vulnerability where an attacker can inject and execute arbitrary code within your application. In PHP, this often occurs when user input is passed into the eval() function or system calls without proper validation or sanitization.

Let's consider the following use case in the context of a PHP Laravel project, where a developer faced a challenge while attempting to dynamically generate an image URL within a Blade template. The goal was to display an image whose path was constructed using variable content and Laravel's URL helper function. To achieve this, the developer used PHP's eval() function as follows:

php
  eval("\$image_url = \"{{ url('public/uploads/trust/".$value.".jpg') }}\";");
?

![]({{ $image_url }})

The developer's intention was to create a flexible way to generate image URLs based on the $value variable. However, the use of eval() raises significant security concerns, such as:

• Code injection: If an attacker can influence the content of the string passed to eval(), they may execute arbitrary PHP code on the server. This could lead to unauthorized access, data breaches, and a range of other security issues.
• Complex debugging and maintenance: Code executed via eval() is often harder to debug and maintain, as it can obscure the logic and flow of the application. This complexity can inadvertently introduce additional security flaws or bugs.

The developer could have used a more secure and maintainable approach by using Laravel's Blade templating engine to generate the image URL:

![]({{ url('public/uploads/trust/'.$value.'.jpg') }})

This method avoids the use of eval() altogether, leveraging Laravel's built-in functionalities to securely generate dynamic content. Make sure you read about more ways to prevent PHP code injection.

Testing PHP Composer dependencies for security vulnerabilities

One often overlooked area of application security is third-party dependencies. In PHP, we use Composer to manage these dependencies. It's crucial to regularly check your dependencies for known security vulnerabilities.

You can use tools like Snyk to automatically scan your Composer dependencies for known vulnerabilities. Here's how you can install and use Snyk:

npm install -g snyk
snyk test

When running the snyk test command in the root directory to test your Composer dependencies for security vulnerabilities, you might see output like this:

Testing /path/to/your/laravel-project/composer.lock...

✗ High severity vulnerability found in symfony/http-foundation
  Description: Arbitrary Code Execution
  Info: https://snyk.io/vuln/SNYK-PHP-SYMFONY-174006
  Introduced through: symfony/http-foundation@5.4.0
  From: symfony/http-foundation@5.4.0
  From: symfony/http-foundation@5.4.0 > symfony/http-foundation@5.4.0
  From: symfony/http-foundation@5.4.0 > symfony/http-foundation@5.4.0 > symfony/http-foundation@5.4.0
  From: symfony/http-foundation@5.4.0 > symfony/http-foundation@5.4.0 > symfony/http-foundation@5.4.0 > symfony/http-foundation@5.4.0
  Fix: Upgrade to symfony/http-foundation@5.4.1

Tested 123 dependencies for known vulnerabilities, found 1 vulnerabilities, 122 vulnerable paths.

I highly recommend reading more on testing your PHP Composer dependencies for security vulnerabilities with Snyk.

Security vulnerabilities in the PHP interpreter

Even if you follow secure coding practices, vulnerabilities in the PHP interpreter itself can expose your applications to risks. For instance, multiple vulnerabilities were reported in the Debian PHP8.2 package, which you can view in the Snyk database.

Some of the notable PHP interpreter vulnerabilities include:

• CVE-2023-0568: Allocation of Resources Without Limits or Throttling.
• CVE-2023-3823: XML External Entity (XXE) Injection.
• CVE-2023-0662: Resource Exhaustion.

These vulnerabilities could allow an attacker to execute arbitrary code or cause a DoS (Denial of Service). So, it is essential to keep your PHP version updated and frequently check for any reported vulnerabilities in the PHP interpreter you are using.

How does Snyk help in PHP security?

Snyk is a powerful developer-first security platform that helps developers identify and fix security vulnerabilities in their PHP applications. It provides an extensive database of known vulnerabilities and can automatically scan your project for these issues. Snyk also offers automated fix PRs, which can save developers significant time in fixing identified vulnerabilities.

What are the most common PHP vulnerabilities?

There are several common PHP vulnerabilities that developers should be aware of. These include:

What’s next for PHP security?

One way to stay updated on PHP interpreter vulnerabilities is to connect your Git repositories to Snyk, which will automatically monitor your dependencies for vulnerabilities and notify you of any new vulnerabilities that are reported. Specifically, you might be deploying your PHP applications using Docker and other containerization technology, and it's crucial to monitor your container images for vulnerabilities because these Docker container images bundle the PHP interpreter and other dependencies that could be vulnerable.

If you're using Docker, you can use Snyk to scan your Docker container images for known vulnerabilities by running the following:

snyk container test your-docker-image

Make sure to follow James Walker's best practices for building a production-ready Dockerfile for PHP applications and Neema Muganga's Securing PHP Containers guide to secure your PHP container images.

Protecting against PHP security vulnerabilities should not be an afterthought but an integral part of your development process. It involves secure coding practices, regular updates, and vigilance for any reported vulnerabilities in the PHP ecosystem.

How can I learn more about PHP security?

To learn more about PHP security, you can follow online tutorials on the Snyk blog and take free online byte-sized lessons on Snyk Learn. Websites like OWASP also provide extensive resources on web application security, including PHP.

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