Web Apps Security

© 2014 IBM Corporation2

●The code that we write is not safe !●Learn by exemplifying ●Introduce developer to security APIs


Interesting facts

● Myth: We are secure because we have a firewall– 75% of vulnerabilities are at web application layer Gartner Group (2002 report)

– Basically network layer protection just denies access to services

● Myth: I am safe because I’m connected via HTTPS/SSL

– HTTPS will just ensure that no one intercepts the information.

– A web page can include static resources or other content from the same host via a non secure channel


Interesting facts

● NASA counted 5,408 security breaches where some access was given or malicious software was installed. In 2011 alone they had 47 attacks they described as “advanced persistent threats,” serious attacks by well-funded “individuals or nations.” Of those, 13 succeeded, and one attack based in China gained complete access to Jet Propulsion Laboratory (JPL) systems — read, write, delete, add and delete users, modify logs, everything.

● Paul Marting ( NASA inspector general ) in a written testimony to US government

● Visa, MasterCard, AmericanExpress & Discover Financial Systems, were hit in March by a data-security breach when a third-party service provider ( Global Payments Inc.) discovered its systems were compromised

● www.reuters.com


Let’s start with OWASP Top 10


● Open web application security project ( www.owasp.org)

● not-for-profit worldwide charitable organization focused on improving the security of application software.

● Users and adopters of APIs and standards: US Federal Trade Commision,Citibank, PwC, HP, IBM Global Services, US Bureau of Alcohol Tobacco and Firearms,etc.

● OWASP Top Ten 2013 ( the 10 most common security flaws found in web applications in 2013 ):

● A1 : Injection● A2 : Broken Authentication and Session Management● A3 : Cross-Site Scripting (XSS)● A4 : Insecure Direct Object References● A5 : Security Misconfiguration● A6 : Sensitive Data Exposure● A7 : Insecure Cryptographic Storage● A8 : Cross-Site Request Forgery (CSRF)● A9 : Using component with known vulnerabilities● A10: Un-validated Redirects and Forwards

OWASP Top Ten


A1 Injection

● Various forms of injection● SQL Injection● Xpath injection● Command injection● Path based injection● LDAP injection● Etc.

© 2014 IBM Corporation

Select user_information from user_table where username='’' or 1=1 -– 'and password=’abc’

8 A1 Injection

Select user_information from user_table where username=’input username’ and password=’input password’

Web Server Application Server

User DatabaseUser

https

SQL injection

© 2014 IBM Corporation9 A1 Injection

Xpath injection

FindUserXPath becomes ://Employee[UserName/text()='blah' or 1=1 or 'a'='a' And Password/text()='blah']

FindUserXPath becomes ://Employee[UserName/text()='blah' or 1=1 or 'a'='a' And Password/text()='blah']


User DatabaseUser

https

FindUserXPath = "//Employee[UserName/text()='" + Request("Username") + "' And Password/text()='" + Request("Password") + "']";FindUserXPath = "//Employee[UserName/text()='" + Request("Username") + "' And Password/text()='" + Request("Password") + "']";

<?xml version="1.0" encoding="utf-8"?><Employees> <Employee ID="1"> <FirstName>Arnold</FirstName> <LastName>Baker</LastName> <UserName>ABaker</UserName> <Password>SoSecret</Password> <Type>Admin</Type> </Employee> <Employee ID="2"> <FirstName>Peter</FirstName> <LastName>Pan</LastName> <UserName>PPan</UserName> <Password>NotTelling</Password> <Type>User</Type> </Employee></Employees>

<?xml version="1.0" encoding="utf-8"?><Employees> <Employee ID="1"> <FirstName>Arnold</FirstName> <LastName>Baker</LastName> <UserName>ABaker</UserName> <Password>SoSecret</Password> <Type>Admin</Type> </Employee> <Employee ID="2"> <FirstName>Peter</FirstName> <LastName>Pan</LastName> <UserName>PPan</UserName> <Password>NotTelling</Password> <Type>User</Type> </Employee></Employees>

© 2014 IBM Corporation10 A1 Injection

Command injection


User DatabaseUser

https

$ ls -l .profile ; cat /etc/password$ ls -l .profile ; cat /etc/password

$ “ls -l” + request.getParameter(“file_name”)


Path based injection ( manipulation / traversal )

● Atacker gains access to system files by manipulating a 'path/to/file.txt' supplied as a parameter

● For plain files, one can browse through the file system with directory style paths ( ../../../../conf/tomcat-users.xml )

● demo

© 2014 IBM Corporation12 A3 Broken authentication and session management

A2 Broken Authentication and Session Management

Attacker uses leaks or flaws in the authentication or session management functions to impersonate users.

•e.g., exposed accounts, passwords, session IDs

© 2014 IBM Corporation13 A3 Broken authentication and session management

● Session ids should not be exposed in the URL ( http://example.com/sale/saleitems;jsessionid=2P0OC2JDPXM0OQSNDLPSKHCJUN2JV?dest=Hawaii )

● They will get recorded in logs of servers, proxies and routers can be easily distributed

● Session cookies must be manipulated only by http headers sent by the server (HttpOnly flag)

● Sessions should timeout in accordance to application risk rating

● All navigation within that domain should be secure (https) because an attacker can 'snif' the session id and steal the session.

● Setting 'secure' flag on session cookies is a must. This way session cookie will not be sent on insecure channels ( e.g. including static resources or embedding remote html )

● Session ids should change after a login attempt

● This prevents session fixation attacks when an attacker obtains (by some other means) the value of the session id and if the target user has a valid logged-in session on a server, the attacker is able to join the session just by setting the session cookie

● demo

A2 Broken Authentication and Session Management

© 2014 IBM Corporation14 A2 Cross site scripting

A3 Cross site scripting

● Stored XSS● Reflected XSS


Stored XSS attacks

● An input field which is not properly validated will insert script tags besides the usual field value

● If the field is displayed literally in another part of the application, it will result in the code within the script tags being executed


User DatabaseUser

https


User DatabaseUser

https


Other flavors of XSS

● Reflected input

● Input from the user is echoed to the screen. (e.g. error messages like 'input X is invalid' – in this case X can contain XSS code and more then often can be sent to a different user via an URL)

● Pretty much all tags are vulnerable to XSS:

● All tags contain event functions (onmouseover,onkeyup, etc.) and they can be passed in as input somewhere

● HTML attributes are also vulnerable

● E.g <frame>, <iframe> and <img> can have the src attribute javascript injectable ( e.g <iframe src=”javascript:alert(1)”/> will be executed by most browsers )

● Even css style tags are vulnerable.

● demo


Other flavors of XSS● And XSS attack vector list goes on:

● <BODY BACKGROUND="javascript:alert('XSS')">

● <LINK REL="stylesheet" HREF="javascript:alert('XSS');">

● <STYLE>@import'http://ha.ckers.org/xss.css';</STYLE>

● <META HTTP-EQUIV="Link" Content="<http://ha.ckers.org/xss.css>; REL=stylesheet">

● <STYLE>.XSS{background-image:url("javascript:alert('XSS')");}</STYLE><A CLASS=XSS></A>

● Comprehensive list of vectors: https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet


Dangerous use of eval

● This is usually done when behavior of page needs to be controlled from the server.

● E.g show different alert() windows.

● eval() function is the most dangerous. Do not put dynamic content in the eval() function.

● The reason for this is that validation of input which goes between the brackets of the eval() is hard to validate. You can basically write js and have the browser interpret it using a simple set of characters.

● In some cases js code can NOT be escaped/commented ( OWASP directive ), so it is really hard to defend against this attack.

● demo

© 2014 IBM Corporation19 A4: Insecure Direct Object References & A5 Cross site request forgery

A4: Insecure Direct Object References & CSRF

●Cross site request forgery (CSRF)●Direct object references

© 2014 IBM Corporation20 A4: Insecure Direct Object References & A5 Cross site request forgery

Request forgery and weak access control

● Attacker will 'forge' request parameters based on 'similarities' between actions and navigation● Easiest to forge will be ids which are usually sequential integers

● Normally all actions within an application should rely on authenticated principal(user) and NOT on supplied parameters

● demo

© 2014 IBM Corporation21 A7 Insuficient cryptographic storage & A9: Insufficient Transport Layer Protection

A7 Insecure cryptographic storage & A9: Insufficient Transport Layer Protection


Insecure HTTP header authentication

● Http header authentication is nothing but a Base64 encoding of 'username:password‘

● Make sure all HTTP authenticated traffic is encrypted

GET /exchange/ HTTP/1.1Host: webmail.xxxx.xxConnection: keep-aliveCache-Control: max-age=0Authorization: Basic dTI5ODMyOTpteV9wYXNzd29yZA==User-Agent: Mozilla/5.0 (Windows NT 5.1) .....Accept:text/html,application/xhtml+xml,..........

dTI5ODMyOTpteV9wYXNzd29yZA==u298329:my_password


Encryption algorithm strengthNumar de caractere

Algoritm incriptare Nr chei / secunda Alfabet Timp

5 Raw MD5 8754 a-z, A-Z 44 seconds5 Raw MD 5 8754 a-z, A-Z, 0-9 1 minutes 46 seconds

5 Raw MD 5 8754 a-z, A-Z, 0-9, !@#$%^&*()_+= 4 minutes 53 seconds

5 Raw SHA-256 2600 a-z, A-Z 2 minutes 29 seconds5 Raw SHA-256 2600 a-z, A-Z, 0-9 5 minutes 58 seconds

5 Raw SHA-256 2600 a-z, A-Z, 0-9, !@#$%^&*()_+= 16 minutes 28 seconds

6 Raw MD5 8754 a-z, A-Z 38 minutes 22 seconds6 Raw MD 5 8754 a-z, A-Z, 0-9 1 hours 49 minutes 54 seconds

6 Raw MD 5 8754 a-z, A-Z, 0-9, !@#$%^&*()_+= 6 hours 11 minutes 46 seconds

6 Raw SHA-256 2600 a-z, A-Z 2 hours 9 minutes 13 seconds6 Raw SHA-256 2600 a-z, A-Z, 0-9 6 hours 10 minutes 4 seconds

6 Raw SHA-256 2600 a-z, A-Z, 0-9, !@#$%^&*()_+= 20 hours 51 minutes 43 seconds

8 Raw MD5 8754 a-z, A-Z 72 days 1 hours 37 minutes8 Raw MD 5 8754 a-z, A-Z, 0-9 293 days 9 hours 50 minutes

8 Raw MD 5 8754 a-z, A-Z, 0-9, !@#$%^&*()_+= 4 years 30 days 5 hours 57 minutes

8 Raw SHA-256 2600 a-z, A-Z 242 days 15 hours 29 minutes8 Raw SHA-256 2600 a-z, A-Z, 0-9 2 years 257 days 9 hours 43 minutes

8 Raw SHA-256 2600 a-z, A-Z, 0-9, !@#$%^&*()_+=13 years 272 days 15 hours 55 minutes


Password strength

Brute-forcing passwords

• '1234567890' can be cracked in 472 s• 'plainpw' can be cracked in 420 s• 'PlainPw' can be cracked in 1681 s• 'Pl4inPw' can be cracked in 126 days• 'P|4inPw' can be cracked in 21 years

© 2014 IBM Corporation25 A10 Unvalidated redirects and forwards

A10 Unvalidated redirects and forwards


Password strength

Be careful when using forward() and include()•It’s an internal mechanism which will bypass standard AS authorization

•request.getRequestDispatcher(“protectedUrl”)• forward()• include()

•demo


Mitigating security threats


● OWASP created the ESAPI in order to 'mitigate' the top 10 risks. The API is available in pretty much every language ( JEE,PHP, .NET,Python, Ruby, etc.)

● It is basically a collection of classes (API) that encapsulate the key security operations that an application needs

● It has been designed to make it easy for programmers to retrofit security into existing applications

● It is scalable at enterprise levels


● It addresses the following aspects:

– Authentication– Access control– Input validation– Output encoding/escaping– Cryptography– Error handling and logging– Communication security– HTTP security– Security configuration– And many more…

OWASP ESAPI

© 2014 IBM Corporation30 Input and output validation

Mitigating XSS and Injection attacks

• Canonicalize input • Convert encoded %3c%3e → <>• Convert encoded <> → <>

• Validate input (at least for these characters <>;:”'()'&)

• Best practice is to throw away potentially harmful content. Do not try to 'clean up' the content, because many cleanup algorithms can be circumvented ( OWASP )

• e.g. some_string.replaceAll(“<script>”,””); attacker can just pass in “<scr<script>ipt>” and the result will be <script>

• Attack vector can also be “< script >” • Can very well be “ < ScRiPt >”

• Use a whitelist of characters instead of blacklist ( permitted vs unpermitted ). The blacklist can never be comprehensive enough.

• Attacks can be extremely complex, so there is also a wide range of characters that can pose threats


Mitigating XSS and Injection attacks

• It is designed to throw meaningfull exception if an attack is suspected

●IntrusionException in case a potential attack is detected ( harmfull characters present)

● ValidationException in case an validation rules fail ( double encoding present and an attack is suspected)

–For Http parameters

●ESAPI.validator().assertValidHTTPParameters(...)

–For file path based parameters

●ESAPI.validator().getValidDirectoryPath(..)

●ESAPI.validator().getValidFileName(..)

–For plain HTML input

●ESAPI.validator().getValidInput(..)

Use ESAPI Validator


● Contextually encode output

– For HTML ( e.g ESAPI HTML encoder )● ESAPI.encoder().encodeForHTML(..)

– For tag attributes (e.g ESAPI HTML attribute encoder )

● ESAPI.encoder().encodeForHTMLAttribute(..)– For CSS ( e.g ESAPI CSS encoder )

● ESAPI.encoder().encodeForCSS(..)– For Javascript ( e.g. ESAPI Javascript encoder)

● ESAPI.encoder().encodeForJavascript(..)– For queries in LDAP Dbs:

– demo● ESAPI.encoder().encodeForDN(...)

Mitigating XSS and Injection attacksUse ESAPI encoder


Encoding of output example

● A developer can also encode output. Using the ESAPI.encoder() you can generate safe HTML, Js, CSS,...

● Below we are encoding this string → <>"'%&.()[]@#//-+

– Encoding for HTML :

– <>"'%&.()[]@#//-+

– Encoding for CSS :

– \3c \3e \22 \27 \25 \26 \2e \28 \29 \5b \5d \40 \23 \2f \2f \2d \2b

– Encoding for JS :

– \x3C\x3E\x22\x27\x25\x26.\x28\x29\x5B\x5D\x40\x23\x2F\x2F\x2D\x2B

– Encoding for html attribute :

– <>"'%&.()[]@#//-+


● Keep things simple

● Use mature APIs/frameworks

● Don’t give away info about the system

● 404 errors, exceptions, html comments

● Keep entire site under https

● Encode output contextually

● Validate input globally

● Keep sessionid safe ( httponly, secure )

● Change it after successful login

Checklist


Thank you !

by Victor Bucutea

Technology

Web Apps Security