Owasp top 10

AVOIDING THE OWASP Top 10 security exploits

Friday, 2 November, 12

ME

Illustrator turned developer

Team Lead at FreshBooks

Lead developer of CakePHP

PHP developer for 7 years


SECURITY


SECURITY CONTINUUM

( )unusable unrestricted


OWASPOpen Web Application Security Project


OWASP TOP 10


SQL INJECTION‘ OR 1=1 ‘--1


RISKS

Permits query manipulation, and arbitrary SQL.

Bad guys can re-write your queries.


$username = $_POST[‘username’];$password = $_POST[‘password’];

$query = “SELECT * FROM userWHERE username = ‘$username’AND password = ‘$password’”;

$user = $db->query($query);

SQL INJECTION EXAMPLE


$username = “root”;$password = “‘ OR 1 = 1 --”;

USER INPUT


FINAL QUERY

$query = “SELECT * FROM userWHERE username = ‘root’AND password = ‘‘ OR 1 = 1 --’”;


FINAL QUERY

$query = “SELECT * FROM userWHERE username = ‘root’AND password = ‘‘ OR 1 = 1 --’”;


PREVENTION

Use an ORM or Database abstraction layer that provides escaping. Doctrine, Zend\Table, and CakePHP all do this.

Use PDO and prepared statements.

Never put user data into a query.

Never use regular expressions, magic quotes, or addslashes()


EXAMPLE (PDO)

$query = “SELECT * FROM userWHERE username = ?AND password = ?”;

$stmt = $db->prepare($query);$stmt->bindValue($username);$stmt->bindValue($password);$result = $db->execute();


2XSS<script>alert(‘cross site scripting’);</script>


RISKS

Allows bad guys to do things as the person viewing a page.

Steal identities, passwords, credit cards, hijack pages and more.


XSS EXAMPLE

<p><?php echo $user[‘bio’]; ?>

</p>


XSS EXAMPLE

<p><?php echo $user[‘bio’]; ?>

</p>


You may be thinking, I can use regular expressionsto fix this.


NOFriday, 2 November, 12

PREVENTION

Regular expressions and strip_tags leave you vulnerable.

The only solution is output encoding.


EXAMPLE

<p><?php echo htmlentities($user[‘bio’],ENT_QUOTES,‘UTF-8’

); ?></p>


DANGERS

Manually encoding is error prone, and you will make a mistake.

Using a template library like Twig that provides auto-escaping reduces the chances of screwing up.

Encoding is dependent on context.


3BROKEN AUTHENTICATION & SESSION MANAGEMENT

/index.php?PHPSESSID=pwned


RISKS

Identity theft.

Firesheep was an excellent example.


SESSION FIXATION EXAMPLE

<?phpsession_start();if (isset($_GET[‘sessionid’]) {session_id($_GET[‘sessionid’]);

}


SESSION FIXATION EXAMPLE

<?phpsession_start();if (isset($_GET[‘sessionid’]) {session_id($_GET[‘sessionid’]);

}


PREVENTION

Rotate session identifiers upon login/logout

Set the HttpOnly flag on session cookies.

Use well tested / mature libraries for authentication.

SSL is always a good idea.


4INSECURE DIRECT OBJECT REFERENCE


RISKS

Bad guys can access information they shouldn’t

Bad guys can modify data they shouldn’t.


BROKEN PASSWORD UPDATE

<form action=”/user/update” method=”post”><input type=”hidden” name=”userid” value=”4654” /><input type=”text” name=”new_password” /><button type=”submit”>Save</button>

</form>


PREVENTION

Remember hidden inputs are not really hidden, and can be changed by users.

Validate access to all things, don’t depend on things being hidden/invisible.

If you need to refer to the current user, use session data not form inputs.

Whitelist properties any form can update.


5CROSS SITE REQUEST FORGERY

(CSRF)


RISKS

Evil websites can perform actions for users logged into your site.

Side effects on GET can be performed via images or CSS files.

Remember the Gmail contact hack.


CSRF EXAMPLE

Your app

Evil site


CSRF EXAMPLE

Your app

Evil site

Login


CSRF EXAMPLE

Your app

Evil site

Login

Accidentally visit


CSRF EXAMPLE

Your app

Evil site

Login

Accidentally visit

Submit form for evil


PREVENTION

Add opaque expiring tokens to all forms.

Requests missing tokens or containing invalid tokens should be rejected.


SAMPLE CSRF VALIDATION

<?phpif (!$this->validCsrfToken($data, ‘csrf’)) {throw new ForbiddenException();

}


6SECURITY MISCONFIGURATION


RISKS

Default settings can be insecure, and intended for development not production.

Attackers can use misconfigured software to gain knowledge and access.


PREVENTION

Know the tools you use, and configure them correctly.

Keep up to date on vulnerabilities in the tools you use.

Remove/disable any services/features you aren’t using.


7INSECURE CRYPTOGRAPHIC STORAGEmd5(‘password’)


RISKS

Weak cryptographic storage can easily be cracked.

Keys can be exposed with encrypted data.

Backups can contain encrypted data & keys.

Compromised passwords can be used to obtain information on other sites.


BAD PASSWORD HASHING

$password;

md5($password);

sha1($password);


BAD PASSWORD HASHING

$password;

md5($password);

sha1($password);


USE BCRYPT FOR PASSWORDS

only you can prevent bad hashing


PREVENTION

Use strong hashing/encryption.

Use one way hashing for passwords. Never use symmetric encryption for passwords.

Don’t collect data if you don’t need it.

Keep keys separate from data.

If you’re using symmetric encryption, be able to rotate keys easily.


BCRYPT IN PHP

// password hashing (bcrypt)$hashed = crypt($pass,‘$2a$10$asdkbisloqi.fidsliz.df190.d9f40’);

// compare later$hashed = crypt($plaintext, $storedHash);

// check for match$hashed === $storedHash


BCRYPT IN PHP





BCRYPT IN PHP





BCRYPT IN PHP





USE MCRYPT

// encrypt (rijndael)$value = mcrypt_encrypt(‘rijndael-256’, $secretKey, $ccnumber,‘cbc’, $iv

);

// decrypt$value = mcrypt_decrypt(‘rijndael-256’, $secretKey, $encrypted,‘cbc’, $iv

);


8FAILURE TO RESTRICT URL ACCESS


RISK

Hidden things can easily be found.

Creative people will eventually find your hidden URLs

Security through obscurity is a terrible idea.


PREVENTION

Check access to all urls both when you generate links and more importantly when handling requests.

Don’t rely on things staying hidden.


9INSUFFICIENT TRANSPORT LAYER PROTECTION


SSL/TLSFriday, 2 November, 12

10UNVALIDATED REDIRECTS & FORWARDS


RISKS

Trusting user input for redirects opens phishing attacks.

Breach of trust with your users.


PREVENTION

Don’t trust user data when handling redirects.


QUESTIONS?


Technology

Owasp top 10