Security Testing for Web Developers

Matthew Hughes

Who am I?Pen testerCoderBloggerAll around nice guy.

Who am I?Ethical Hacking for Computer Security BSc

2009 - 2011Internship at Mad Security 2010-2011Internship at St Noble/MMV – 2011Developer at CIC 2011-2012Unemployed “Entrepreneur” – Current

What is this all about then? Most web applications are insecure. Secure coding is hard. Developers generally don’t know how to test

their own sites. Insecure web applications are generally bad.

Why should you care?Security breaches are very expensive. Security breaches make you look like a

moron. It’s fairly easy to mitigate against them. Hacking is fun. Security consultants are fucking expensive.

What will this talk cover?This talk is not exhaustive. It will only cover a

fraction of the basics. It will discuss various kinds of attack you can

expect your application to endure. It will give you an understanding of how to

test for security vulnerabilities in your application.

What will this talk cover?Detection

Reflected XSSStored XSSXSRFSQLi

MitigationVulnerability disclosure

What will this talk cover?This talk is an introduction. It won’t cover

everything. Web application security is a HUGE domain.

A bit of history…1995 – Most websites tended to be static

pages coded in pure HTML. 1999 – Perl and PHP gain popularity, and

their relative ease of use allow for beginners to make web apps.

And it sorta goes downhill from there…

So, what happened next?Nobody really understood the risks involved

with dynamic websites. More and more companies began to rely on

web apps. More and more companies experienced

security breaches…Which for the most part has been fun to

watch…

Notable examplesSony PSN Hack

77 million pieces of personally information were leaked via SQLi.

Biggest leak in history.Outage lasted for 24 days. Total costs were $171 Million USD

TJX Hack45 million pieces of credit card information

were leaked. Attacker used SQLi and sniffed traffic. Breach cost $200 million

Notable Examples

Notable ExamplesSamy worm

Samy Kamkar used an XSS vulnerability in MySpace to get anyone who viewed his profile to friend request him, and add “and most of all, Samy is my hero” and the exploit code to their profiles.

Within 20 hours, over 1,000,000 had their pages compromised.

What conclusions can we draw?Security breaches can happen to large

corporations with huge amounts of resources. Security breaches are expensive. Really

expensive. They can also be pretty funny.

Cross Site Scripting (XSS)XSS happens when an input isn’t correctly

sanitized and is either reflected in the page (reflected XSS) or stored within the application and rendered for each subsequent user (stored XSS).

Whilst XSS attacks may seem harmless, they can be the precursor to social engineering attacks, XSRF attacks and can be used to steal cookies.

Cross Site Scripting (XSS)<script>alert(‘xss’)</script>Some sites in order to mitigate against XSS

attacks forbid the usage of ‘alert’… This doesn’t really mitigate against XSS. Just use ‘prompt’. As we will see in the next slide…

Tags with attribute values can be mitigated by crafting your attack string with “> at the front.

“><script>alert(‘xss’);</script>

Cross Site Scripting (XSS)

Cross Site Scripting (XSS)

SQL InjectionGenerally, most dynamic websites contain a

data store. These are generally interacted with using

SQL. SQL is standardized, meaning that the attack

syntax generally works an all DBMS’ORM and NoSQL databases are vulnerable to

injection attacks. Just not SQL attacks.

SQL InjectionConsider the following SQL query“Select * from users where username =

@param;”What would happen if we were to put in the

following parameter. “dave’ or ‘1’ = 1”Since one does equal one, it will return all

values.With union queries, one can add data into

other tables, creating the potential to create new accounts.

SQL InjectionSQL Injection can also be used to bypass

authentication.Consider the following SQL query“Select * from users where username =

@params and passworld = @params”. What would happen if you were to pass it the

followingAdmin ‘ ---You can now authenticate against any

account without knowing the password…

Cross Site Request Forgery (XSRF)Consider the following URL:http://bankofliverpool.com/transfer?acount=p

urpleaki&amount=9001&for=JenniferEllisonIf the user is authenticated and the site is

vulnerable to XSRF, then Jennifer Ellison is about to get over nine thousand pounds from Purple Aki

“But surely this is just a browser/local user issue?”

Cross Site Request Forgery (XSRF)Well, yes and no…The user has to be authenticated on their

local machine and have a valid cookie. But… consider the following code. <img href=http://

bankofliverpool.com/transfer?acount=purpleaki&amount=9001&for=JenniferEllison>

Now, this isn’t a valid image… But the browser will still call that URL.

Going on from here…This is going to be the last I’m going to talk

about when it comes to vulnerability discovery…

It’s a huge field.Web Application Hackers Handbook is a good

place to start… DVWA is a great sandboxed environment

where you can use offensive security testing techniques.

A lot of testing can be automated and there are various firefox/Chrome plugins which do a lot of the legwork.

Going on from hereOWASP is a group dedicated to web app

security. They meet fairly often in these parts and

entrance is free. Read the OWASP Top 10. Just do it.

Another valid point…It’s generally frowned upon to test systems

that don’t belong to you. Don’t do it, unless you have permission, or

you like prison food.

MitigationA good offense is generally the best

defence…Your best is often not good enough, especially

against a really motivated hacker. Web Application firewalls are a solid line of

defence against many attacks. Trustwave’s ModSecurity is very, very good.

MitigationThere’s no point reinforcing a door if you’re

going to leave the windows open. Ensure that the underlying infrastructure is

regularly patched, you have an IDS (Snort is free and very, very good) and you reduce the surface of attack by turning off services you don’t need and running a firewall.

Responsible vulnerability disclosure…We’re all geeks. We’re curious. I know some

of you will discard my valid point I made earlier.

Full Disclosure is bad. Very bad. Responsible disclosure is good. Very good. Upsploit.com is a good resource for handling

vulnerability disclosure.

Keep in touch?Twitter.com/matthewhughesme@matthewhughes.co.ukFacebook.com/matthewjhughesMatthewhughes.co.uk

Thank you!Any questions?