How to configure a CentOS system to protect web applications from SQL injection attacks

How to configure CentOS system to protect web applications from SQL injection attacks

Introduction:
With the development of the Internet, the use of web applications is becoming more and more widespread, but it also brings Web application security issues. Among them, SQL injection attack is the most common attack method. In order to protect our web applications, we need to perform a series of configurations and optimizations on the CentOS system. This article will describe how to configure a CentOS system to protect web applications from SQL injection attacks.

1. Installing and Configuring Web Server
   First, we need to install and configure a reliable web server to host our web application. Here, we choose the commonly used Apache server as an example. The following is an example of the command to install the Apache server on CentOS:

   sudo yum install httpd

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   After completing the installation, we need to perform some security configurations on Apache. First, we will disable directory browsing on the server to prevent attackers from obtaining sensitive information on the server. The following is an example of disabling directory browsing by modifying the httpd.conf file:

   sudo vi /etc/httpd/conf/httpd.conf

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   Find this line in the file:

   Options Indexes FollowSymLinks

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   Modify to:

   Options -Indexes FollowSymLinks

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   Save and exit the file . Then, we will restart the Apache server to make it take effect:

   sudo systemctl restart httpd

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2. Configuring the Database Server
   Web applications often require the use of a database to store and manage data. Here, we choose MySQL as the database server to store our data. The following is an example of the command to install the MySQL server on CentOS:

   sudo yum install mysql-server

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   After completing the installation, we need to perform some security configurations on MySQL. First, we will disable remote access and only allow local access to the database. The following is an example of disabling remote access by modifying the my.cnf file:

   sudo vi /etc/my.cnf

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   Find the following line:

   bind-address = 127.0.0.1

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   Add the comment symbol "#" before the line to make it a comment line:

   #bind-address = 127.0.0.1

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   Save and exit the file. We will then restart the MySQL server for the configuration to take effect:

   sudo systemctl restart mysqld

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3. Writing Secure Web Application Code
   When writing web application code, we need to take some security measures to prevent SQL injection attack. The following is sample code for some defensive measures:

4. Use parameterized query statements: When executing SQL queries, we should use parameterized query statements instead of concatenating strings. This prevents attackers from injecting additional SQL code using malicious input. The following is an example of using parameterized query statements:

   import pymysql
   
   conn = pymysql.connect(host='localhost', user='username', password='password', database='dbname')
   cursor = conn.cursor()
   
   sql = "SELECT * FROM users WHERE username = %s"
   username = 'admin'
   cursor.execute(sql, (username,))
   
   result = cursor.fetchall()
   
   for row in result:
    print(row)
   
   conn.close()

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• Filter and validate input: When receiving user input, we should filter and validate the input Validate to ensure the input conforms to the expected format and type. Here is an example of input filtering and validation:

  username = input("请输入用户名：")
  
  # 过滤非法字符
  for char in username:
    if char not in ('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_'):
        username = username.replace(char, '')
  
  # 验证用户名长度
  if len(username) > 20:
    username = username[:20]
  
  print("处理后的用户名为：", username)

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• Use safe database libraries: When using database libraries, we should choose reliable libraries like pymysql or psycopg2 and avoid using known existing libraries Library for security vulnerabilities. These libraries usually provide some built-in defense measures, such as automatically escaping special characters, etc.

Conclusion:
With the above configuration and code optimization, we can effectively protect our web application from SQL injection attacks. Of course, this is only part of the protection measures. We also need to pay attention to other security issues and update and maintain the system in a timely manner. By combining various security measures, we can more effectively protect the security of our web applications and data.

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