PHP vulnerability exploitation techniques commonly used by hackers

PHP vulnerability exploitation techniques commonly used by hackers

With the popularity and development of the Internet, network security issues have also become a global problem. As the "enemy" of network security, hackers' methods are constantly innovating and evolving. In hacker attacks, PHP-based websites often become one of the main targets. PHP is a powerful and widely used programming language, but due to its open source nature and ease of learning and use, it also provides hackers with many opportunities to exploit vulnerabilities. This article will introduce several PHP vulnerability exploitation techniques commonly used by hackers and provide corresponding code examples.

1. SQL injection
   SQL injection is a common network attack technique. Hackers insert malicious SQL code into forms submitted by users to perform unexpected database operations. The following is a simple example:

<?php
$id = $_GET['id'];

// 拼接 SQL 查询语句
$sql = "SELECT * FROM users WHERE id = " . $id;

// 执行查询
$result = mysqli_query($conn, $sql);

// 处理查询结果
// ...
?>

In the above code, the id entered by the user is directly spliced ​​into the SQL query statement and the query is executed. If the hacker passes id=1 OR 1=1 in the URL, a query equivalent to SELECT * FROM users WHERE id = 1 OR 1=1 will be executed, thus Authentication bypassed.

Defense method: Use prepared statements or escape user input to solve SQL injection problems.

2. File inclusion vulnerability
   File inclusion vulnerability refers to the presence of unfiltered user input in the website's code, allowing an attacker to load arbitrary files and execute the PHP code in them. The following is a simple example:

<?php
$page = $_GET['page'];

// 拼接文件路径并包含文件
include("pages/" . $page . ".php");
?>

In the above code, the page entered by the user is directly spliced ​​into the file path and includes the file. Hackers can load sensitive files such as database configuration files by passing page=../config.

Defense method: Strictly filter and check user input to ensure that the included file paths are safe.

3. File upload vulnerability
   File upload vulnerability means that an attacker can execute arbitrary code or gain system permissions by uploading malicious files. The following is a simple example:

<?php
$targetDir = "uploads/";
$targetFile = $targetDir . basename($_FILES["fileToUpload"]["name"]);

// 检查文件类型
$fileType = strtolower(pathinfo($targetFile, PATHINFO_EXTENSION));
if($fileType != "jpg" && $fileType != "png" && $fileType != "jpeg" && $fileType != "gif") {
    exit("只允许上传图片文件！");
}

// 上传文件
if(move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $targetFile)) {
    echo "文件上传成功！";
} else {
    echo "文件上传失败！";
}
?>

In the above code, there is a problem with the code that checks the file type. Hackers can upload malicious executable files by changing the file extension, thereby executing arbitrary code.

Defense method: Perform strict type and content verification on uploaded files, and save uploaded files in a non-web-accessible directory.

Summary:
As a widely used programming language, PHP provides hackers with many opportunities to exploit vulnerabilities. When developing and maintaining PHP websites, we must keep security in mind and use some defensive measures to reduce hacker attacks. This article introduces several PHP vulnerability exploitation techniques commonly used by hackers and provides some simple code examples. However, this is just the tip of the iceberg. Defense of code vulnerabilities needs to be carried out by combining security awareness and technical means throughout the entire development process. Only by continuously improving security awareness and learning the latest vulnerability defense technology can we ensure the security of PHP websites.

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