Hacktober 2020 CTF - Null and Void
Oct 17, 2020
Challenge Description
Using the Shallow Grave SQL dump, which field(s) in the users table accepts NULL values? Submit the field name followed by the single command used to show the information (separated by a comma). Submit the flag as flag{column-name, command}.
Example: flag{employee_id, SELECT}
Use the file from Address Book.
Solution
Within the same sql dbs, we can pull users table description with DESCRIBE Statement:
MariaDB [dbs]> DESCRIBE users;
+----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+----------------+
| user_id | int(11) | NO | PRI | NULL | auto_increment |
| username | varchar(52) | NO | UNI | NULL | |
| first | varchar(52) | NO | | NULL | |
| last | varchar(52) | NO | | NULL | |
| middle | varchar(24) | YES | | NULL | |
| email | varchar(52) | NO | UNI | NULL | |
| street | varchar(52) | NO | | NULL | |
| city | varchar(52) | NO | | NULL | |
| state_id | int(11) | NO | MUL | NULL | |
| zip | varchar(10) | NO | | NULL | |
| gender | varchar(8) | NO | | NULL | |
| dob | date | NO | | NULL | |
+----------+-------------+------+-----+---------+----------------+
12 rows in set (0.016 sec)
We see that the filed middle accept Null Values.
our flag is : flag{middle, DESCRIBE}