引言
SQL注入是一种常见的网络安全漏洞，它允许攻击者通过在数据库查询中注入恶意SQL代码，从而获取、修改或删除数据库中的数据。手工SQL注入通常需要攻击者对SQL语言有深入的了解，本文将详细探讨手工SQL注入的技巧、风险以及如何防范此类攻击。
什么是SQL注入？
SQL注入（SQL Injection）是一种攻击手段，攻击者通过在输入框中输入恶意的SQL代码，使得原本安全的数据库查询执行了攻击者的恶意代码。这种攻击通常发生在应用程序没有对用户输入进行适当过滤的情况下。
手工SQL注入的技巧
1. 确定注入点
首先，攻击者需要确定哪些输入字段可能被用于注入。这通常通过尝试在输入框中输入单引号（’）或其他特殊字符来实现。如果数据库查询因输入而失败，那么可能存在注入点。
2. 确定数据库类型
攻击者需要知道目标数据库的类型，例如MySQL、SQL Server等，因为不同的数据库有不同的函数和语法。
3. 检查错误信息
数据库错误信息通常包含有关数据库结构的线索，攻击者可以利用这些信息来确定数据库的结构。
4. 构造注入payload
根据数据库类型和查询结构，攻击者可以构造不同的payload。以下是一些常见的payload示例：
联合查询（Union Query）：
' OR '1'='1这个payload尝试返回所有记录，因为它构造了一个总是为真的条件。
错误信息查询： “`sql 1’ 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, null, null, null, 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