引言
SQL注入是一种常见的网络安全漏洞，攻击者可以通过在SQL查询中注入恶意代码，从而获取数据库的控制权，甚至上传恶意文件（如Shell）。本文将深入探讨在DVWA（Damn Vulnerable Web Application）环境中进行SQL注入攻击以写Shell的实战技巧，并分析相应的风险防范措施。
DVWA环境介绍
DVWA是一款用于安全学习和测试的PHP/MySQL应用程序，其设计初衷是为了演示各种安全漏洞。在DVWA中，我们可以通过调整难度级别来模拟不同级别的SQL注入攻击。
SQL注入写Shell的实战技巧
1. 确定注入点
首先，我们需要在DVWA中找到一个SQL注入点。通常，这可以通过以下步骤实现：
- 测试表单输入字段，观察是否可以修改SQL查询。
- 使用’or 1=1’等技巧来测试是否存在SQL注入。
2. 查询数据库结构
一旦确定了注入点，下一步是查询数据库结构。以下是一些常用的SQL注入技巧：
- 使用
UNION SELECT来获取数据库中的数据。 - 使用
information_schema或sys.tables等系统表来获取数据库结构信息。
3. 写入Shell
以下是一个示例代码，展示如何通过SQL注入写入一个简单的Shell：
”`sql – 假设我们已经确定了注入点，并且可以执行以下SQL语句 UNION SELECT NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, 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