The Principles of Secure Development

David Rook

The Principles of Secure Development

OWASP Ireland Conference, Dublin

Friday, 18 September 2009

if (slide == introduction)
System.out.println("I’m David Rook");

• Security Analyst, Realex Payments, Ireland
CISSP, CISA, GCIH and many other acronyms

• Security Ninja (www.securityninja.co.uk)

• Speaker at security events (national and international)

• IIA Web Development Working Group

• Facebook hacker and published security author (insecure
magazine, bloginfosec etc)


Agenda

• It is broken so lets fix it

• The current approach

• The Principles of Secure Development

• An example of a real world implementation


It is broken so lets fix it

• Cross Site Scripting, 10 years old?

• SQL Injection, 11 years old?

33% of all vulnerabilities in 2008 and 2009 (so far) are
XSS or SQL Injection (Based on CVE numbers)

CVE statistics: http://web.nvd.nist.gov/view/vuln/statistics


CVE's
Total
SQLi
XSS



7000

6000

5000 CVE's
Total
SQLi
4000 XSS

3000

2000

1000

0
2009 2008 2007 2006 2005 2004 2003 2002 2001 2000


SQLi & XSS = 32.24%
7000

6000

5000 CVE's
Total
SQLi
4000 XSS

3000

2000

1000

0
2009 2008 2007 2006 2005 2004 2003 2002 2001 2000

Philosophical Application Security

Give a man a fish and you feed him for a day, teach
him to fish and you feed him for a lifetime.


Philosophical Application Security

Give a man a fish and you feed him for a day, teach
him to fish and you feed him for a lifetime.

I want to apply this to secure application development:

Teach a developer about a vulnerability and he will
prevent it, teach him how to develop securely and
he will prevent many vulnerabilities.


The current approach
(And why I think it fails to deliver secure applications)

• The cart before the horse

• Security guys tell developers about specific vulnerabilities
• We hope they figure out how to prevent them
• Inevitably security flaws end up in live code
• Security guys complain when data gets stolen



• What if we taught drivers in the same way?

• Instructor tells driver about the different ways to crash
• We hope the driver figures out how not to crash
• Inevitably the driver will crash
• People complain when they get crashed into



• Many lists of vulnerabilities

• OWASP Top 10
• White Hat Sec Top 10
• SANS Top 25
• Others??

• != Secure development guidance



• Many lists of vulnerabilities

• OWASP Top 10
• White Hat Sec Top 10
• SANS Top 25
• Others??

• != Secure development guidance

• 45 vulnerabilities, 42 unique names

• 8 secure coding principles to prevent them

What we need to do

• Put the application security horse before the cart

• Security guys tell developers how to write secure code
• Developer doesn’t need to guess anymore
• Common vulnerabilities prevented in applications
• Realistic or just a caffeine fueled dream?


Lets make secure development easier

• Keep It Short and Simple (KISS)

• The principles must be clearly defined
• Language/Platform/Framework independent
• Should cover more than just the common vulnerabilities
• More secure software and greater ROI on security training?



Input Validation

Output Validation

Error Handling

Authentication and Authorisation

Session Management

Secure Communications

Secure Storage

Secure Resource Access



• Input Validation

• Identify and define the data your application must accept




• Create regex’s to validate each data type (content and size)
• For example, a credit card number data type: d{12,16}$




• Use whitelisting for validation where possible




• Use whitelisting for validation where possible
• Blacklisting approach harder and potentially less secure
• Blacklist example, replacing single quotes:
s.replaceAll(Pattern.quote(" ' "),
Matcher.quoteReplacement(" " "))



• Output Validation

• Identify and define the data your application must output




• Understand where (i.e. in a URL) your data should end up
• Choose the correct output encoding for the data's destination




• Understand where (i.e. in a URL) your data should end up
• Choose the correct output encoding for the data's destination
• Proper encoding means this attack:
www.examplesite.com/home.html?day=<script>alert(document.cookie)</script>

Becomes:
day=%3Cscript%3Ealert%28document.cookie%29%3C/script%3E



• Error Handling

• Even the best apps will crash at some point, be prepared!



• Error Handling

• Crashes/errors can help an attacker if you don’t handle them



• Error Handling

• Handle error conditions securely, sanitise the message sent



• Error Handling

• Handle error conditions securely, sanitise the message sent
• No error handling = information leakage
Microsoft OLE DB Provider for ODBC
Drivers(0x80040E14)
[Microsoft][ODBC SQL Server Driver]
[SQL Server]Invalid column name

/examplesite/login.asp, line 10


• Authentication and Authorisation

• Even simple apps often have a need to authenticate users




• Often at least two levels of authorisation




• Need to prevent horizontal and vertical privilege escalation




• Implement strong passwords and management systems




• Ensure A+A is secure, not a false sense of security (CAPTCHA?)




• Ensure A+A is secure, not a false sense of security (CAPTCHA?)
• Don’t rely on fields that are easily spoofed (referrer field)



• Session Management

• Used to manage authenticated users, no need to re-auth




• You need to ensure that your sessionID’s have sufficient entropy




• SessionID’s must not be predictable or reusable




• Never build your own session management, it will fail




• Protect sessionID’s when in transit (i.e. SSL!)




• Protect sessionID’s when in transit (i.e. SSL!)
• Issue a new value for sensitive actions (i.e. funds transfer)



• Secure Communications

• Protect data (i.e. CC no, passwords, sessionID’s) in transit




• As with all crypto, don’t create your own




• Don’t use broken protection mechanisms (i.e. SSLv2)




• Don’t just use SSL/TLS for logon pages, protect the session!




• Don’t just use SSL/TLS for logon pages, protect the session!
• Try to avoid mixing secure and insecure traffic on a page



• Secure Storage

• Protect data (i.e. CC no, passwords, sessionID’s) when stored



• Secure Storage




• Secure Storage

• Don’t use broken protection mechanisms (i.e. DES)



• Secure Storage

• Don’t store data in places where you can’t confidently secure it



• Secure Storage

• Don’t store data in places where you can’t confidently secure it
• Strong protection mechanisms, how strong should it be?



• Secure Resource Access

• Obscurity != security, don’t try to hide sensitive resources




• Understand the users flow through an app, cover weak spots




• Understand the users flow through an app, cover weak spots
• T-Mobile didn’t do the above, Paris Hiltons account hacked


Lets redefine what secure development means

• Follow a small, repeatable set of principles

• Try not to focus on specific vulnerabilities

• Develop securely, not to prevent "hot vuln of the day"

• Build security into the code, don’t try to bolt it on at
the end


Evolution, not revolution

• Don’t make things more difficult than they need to be

• This isn’t a new wheel, its just a smoother, easier to use wheel
• Don’t treat security as something separate, integrate it
• By integrating security fully a security bug is just another bug
• Secure development doesn’t have to be hard, KISS it!


The new approach is working

• Private banking development company, Switzerland
• Application Security lead saw the secure development principles



• Re-designed secure development training for his company



• Security training costs down, quicker "spin up" of developers



• Security within their SDLC now based on the principles



• Security within their SDLC now based on the principles
• In his own words:

You released the "secure development principles" at a time I had issues with
my dev teams in how to teach them secure development. Your approach
convinced me to look in another direction, not trying to teach every
vulnerability but finding the basic principles that help prevent their
existence. At that time, this was genius for me: most of my training since
has been inspired by your secure development principles.



They modified the principles matrix to match their own terminology


Security Ninja new site launch!

• Security Ninja, brought you by Realex Payments

• Free application security and compliance resource site




• Blog and site managed and updated by myself




• Security presentations, whitepapers, videos and audio online




• Security presentations, whitepapers, videos and audio online
• Secure Development Principles whitepaper available here today


www.securityninja.co.uk
Twitter: @securityninja


QUESTIONS?
www.securityninja.co.uk
Twitter: @securityninja


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