Attacking Data StoresBrad StancelCSCE 813 Presentation 11/12/2012

Sources Consulted• Stuttard, D. and Pinto, M., The Web

Application Hacker's Handbook: Finding and Exploiting Security Flaws 2nd Edition, 2011, Wiley Publishing

Importance of Data Stores• Almost every web app uses data stores

• Used to hold information vital to the application

• Often hold information crucial to the application logic (access control, etc.)

Important Notes about Data Stores• Application interacts with the data

store at a specified security level• Common data stores are databases

that use SQL (Structure Query Language) to interact & manipulate database• Other non-SQL type databases are

becoming more popular (i.e. NoSQL)• Some data stores specifically revolve

around access control (i.e. LDAP)

Interpreted vs. Compiled Languages• Injection Attacks can happen on either

type of language

• Interpreted languages make it easier for injection attacks (i.e. can type in code)

• Compiled language injection attacks generally use machine code

SQL Injection

• Type of code injection common in interpreted languages that use SQL data stores• A lot of similarities across databases

but each vendor database may be a bit different• Our focus today is on: MS-SQL, Oracle

and MySQL data stores

Fingerprinting the Database• Extract version string

o MySQL /*!32302 and 1=0*/• Look at Concatenation of Strings

o Oracle 'serv'||'ices'o MS-SQL 'serv'+'ices'o MySQL 'serv' 'ices'

• Look at how Numeric Data is handledo Oracle BITAND(1,1)-BITAND(1,1)o MS-SQL @@PACK_RECEIVED-

@@PACKRECEIVEDo MySQL CONNECTION_ID()-

CONNECTION_ID()

Testing for Injection BugsGeneral Algorithm:• Supply unexpected data and syntax• Identify any anomalies• Observe and examine any error messages• Systematically modify input to confirm or disprove

vulnerability existence• Construct proof-of-concept that causes safe command to

execute in a verifiable way to prove flaw exists• Exploit the vulnerability by leveraging functionality and

knowledge of target language and/or its components

Testing for SQL Injection BugsThree Main Methods:

• Injecting into String Data

• Injecting into Numeric Data

• Injecting into Query Structure

Injecting Into String Data• String data is encapsulated into single

quotation marks• Need to break out of these quotation

markso ex. Wiley' OR 'a'='a

• Preliminary Steps to Test:o Submit a single quotation mark to see if error

occurso Submit two quotation marks (escape

sequence) and look for error or odd behavioro Try SQL concatenation techniques discussed

earlier and if no behavior detected possible vulnerable

Injecting Into Numeric Data• Query may use numbers as strings so

try string data methods first• Remember to encode certain

characters• Steps to Test:

o Supply a mathematical expression equiv. to number (responds same way = possible vulnerable)

o Use more complicated expressions that use SQL keywords.

o Using ASCII commands to test are useful 67-ASCII('A') 51-ASCII(1)

Injecting Into Query Structure• Determine the Type of Statement

o SELECT Statements

o INSERT Statements

o UPDATE Statements

o DELETE Statements

o UNION Operator (more of a technique)

SELECT Statements• Frequently used when returning data

based on user's actions• Attack entry point is usually the

statement's WHERE clause• Correct Example:

o SELECT author,title,year FROM books WHERE publisher = 'Wiley'

• Malicious Example:o Input into web form: Wiley' OR 1=1--o SELECT author,title,year FROM books WHERE

publisher = 'Wiley' OR 1=1--

INSERT Statements• Used to create a new row of data in a

table• Example: Web app that allows users to

self register• Correct Example:

o INSERT INTO users (username, password, privs) VALUES ('daf','secret',1)

• Malicious Example:o Input into web form: foo','bar',0)--o INSERT INTO users (username, password,

privs) VALUES ('foo','bar',0)--o MUST contain correct number of data types!

UPDATE Statements• Used to modify one or more rows of

existing data in a table• Correct Example:

o UPDATE users SET password='newsecret' WHERE user='brad' and password='secret'

• Malicious Example:o Input into web form: admin'--o UPDATE users SET password='newsecret'

WHERE user='admin'--• This example bypasses the password

check & changes the admin password!

DELETE Statements• Used to delete one or more rows of

data in a table• Can corrupt the entire table or

database• Correct Example:

o DELETE from users WHERE uid='brad'• Malicious Example:

o Input into web form: ' OR ' '='o DELETE from users WHERE uid=' ' OR ' '=' '

• This example deletes all user ID's in the users table!

UNION Operator• Used to combine results of two or more

SELECT statements into a single result set• Supported by all major DBMS products• Fastest way to retrieve arbitrary

information when query results are returned• Point of attack is usually the WHERE

clause of a SELECT statement• Additional SELECT statement must

contain correct number of data types

UNION Operator cont.• Example SELECT statement before:

o SELECT author,title,year FROM books WHERE publisher ='Wiley' (Where Wiley was submitted)

• Input put into web form:o Wiley' UNION SELECT username,password,uid

FROM users--• Returns a dataset containing both the

authors,titles,year and username,password,uid in one table• This example only works if users table

has three columns

Advanced Techniques• Out-of-Band Communication

• Bypassing Filters

• Using Comments & Circumventing Validation

• Second Order SQL Injection

• Retrieving Data as Numbers

• Inference

Escalating Attacks• Most applications employ one account

for database access• Rely on application-layer controls to

enforce segregation of access• Already have the data, why escalate?

o Gain access to other hosted application datao Compromise the OS of the database servero Gain network access to access other systemso Establish network connection to own system

for faster data retrievalo Include own functions to enhance DB

capabilities

Some Tools Used in SQL Exploitation

• Absinthe - Automated Blind SQL Injection Tool

• SQLMap - Automatic SQL Injection Tool

Preventing SQL Injection• Validate input!

• Escape certain characters and words

• Use Stored Procedures to helpo This does not completely solve the problem

• Parameterized Querieso AKA: prepared statementso Application specifies query's structureo Application specifies contents of each

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Summary, Comments and Questions• Attacking Data Stores can be done in a

variety of ways• Protecting Data Stores is of utmost

importance• Understanding how these attacks take

place enables one to better protect against them• Questions and Comments.........