Account entrapment

© Copyright 2014 Denim Group - All Rights Reserved

Account Entrapment

Forcing a Victim into an Attacker’s Account


Outline• What is Account Entrapment• What can an attacker do with Account Entrapment?• Cookie-based• How the attack works• Defenses

• Login Cross Site Request Forgery• How the attack works• Defenses


What is Account Entrapment?• We aren’t talking about an attacker gaining access

to a victim’s account. This is the opposite.• We are talking about logging the victim into the

attacker’s account.• Why?!• To get the victim to store their information in the

attacker’s account (paypal, tax site)• To get the victim to do work as the attacker (contests)• To frame the victim for hacking!


But Why?! (tell me your secrets)• Paypal or Amazon.com allows a user to store credit

card information and use it in the future.• If the victim stored their credit card information on

the attacker’s account, the attacker could use it.• Youtube got hit with this. The victim would get

logged in to the attacker’s account and browse around. Later, the attacker could view the history.• Imagine a tax preparation site or a password

storage site or any site where secrets are stored.• Dropbox.


But Why?! (do my homework)• If homework answers are submitted online, log in

the smartest person under your account.• For any kind of contest you could try to get

everyone logged in under your account(s). Then you’d be guaranteed to win!• fiverr.com is a site where people do tasks for five

dollars. Suppose they were doing tasks under your account. Cha-ching!• Log in the best online poker player to your online

poker account.• Online Bill Pay!


But Why?! (I was framed!)• It would be easy to frame someone for hacking into

your account this way.• For sites that are obvious when you’re not in your

own account (social media), this would work well for entrapment. Once you log them into your account, it’s hard not to look around.• While this might not lead to criminal action, it could

be used to get a boss or co-worker fired, or manipulate people in other ways.• Repudiation! “There were so many people logging

into my account, I can’t be held responsible.”


But Wouldn’t Someone Notice?!• Facebook? Amazon? City utilities bill pay site?• An attacker can usually craft an account that looks

identical to what the victim would expect.• Cookie Based Account Entrapment can swap a

victim into an attacker’s account for a single page.


Two Main Variants• Cookie Based Account Entrapment• Due to looser Same-Origin Policy restrictions on cookies,

the attack can:• originate from a sister domain (marketing.bank.com can affect

myaccount.bank.com)• and target a single action invisibly.

• State domians have special considerations: state.tx.us

• Login Cross Site Request Forgery• Force the victim to make a login request using the

attacker’s credentials. That system will set up a valid session for the victim under the attacker’s account.


A Little Background• The internet is nothing more than plain text

requests and responses.• The browser makes a request to the server.• The server processes the request and returns a

response (usually containing the HTML of the page).• The browser interprets that response and usually

shows a page.• The user interacts with the page and makes a new

request …


Response (to previous request)HTTP/1.1 200 OK

Content-Type: text/html; charset=utf-8

Set-Cookie: name1=value1; expires=Wed, 10-Aug-2016 21:28:26 GMT; domain=denimgroup.com; path=/; secure; httponly

Set-Cookie: name2=value2

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head> …


RequestGET /application-security-training.html HTTP/1.1

Host: www.denimgroup.com

User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.125 Safari/537.36

Referer: http://www.denimgroup.com/

Cookie: name1=value1; name2=value2


How Cookies WorkGROOT

.us .com.gov

google.comusa.gov

irs.gov

.tx.us.co.us.ny.us

.state.tx.us.state.co.us.state.ny.us

.sos.state.co.us .cpw.state.co.us .doc.state.co.us

smokey.cpw.state.co.us admin.doc.state.co.us

beta1.google.com

mail.google.com

yahoo.com


How Cookies Work (examples)• http://a.b.c.com can set cookies with:• domain=b.c.com or domain=c.com, cookies set with

domain=c.com will get sent by the browser to d.c.com• path isn’t validated at all• names don’t have to be unique: overwriting/overloading• Secure flag can be set from HTTP and cookies with

Secure flag can be overwritten, overloaded, or expired.

• http://a.b.c.com can’t set cookies with:• domain=.com or domain=.tx.us (browser specific lists)• domain=d.c.com, but cookies set to c.com will be sent


Traditional Security Scope

Common Domain Setup (private)

.good.com

.app1.good.com .marketing.good.com

.secure.app1.good.com .insecure.marketing.good.com


Traditional Security Scope

Common Domain Setup (state)

.state.co.us

.cpw.state.co.us .doc.state.co.us

smokey.cpw.state.co.us admin.doc.state.co.us

cookie domain can be set up to .state.co.us


Cookie-based Account Entrapment• The attacker uses a sister domain with an XSS or

header injection vulnerability.• They trick the victim to go there, which stores a

logged-in session cookie on the victim’s browser.• When the victim uses the actual site, they’re using

it in the attacker’s account.• But wouldn’t they notice?!• On Facebook they would, but what about amazon.com?• If the path is set to a specific area, the victim could log

into their own account and not notice the transition.• The attacker could make the accounts appear similar.


Defenses• Remove XSS and header injection everywhere.• Get browsers to treat .state.**.us as a top-level

domain. This is non-trivial as http://state.**.us is sometimes an actual site.• Use different domains, not just subdomains.• Referer checking and a URL token on every page.• Referer checking on every page enforces going to the

login page first and stops the attacker from forwarding the victim to a logged in page. It also breaks things.• URL tokens stop session switching, where the victim is

logged into their own account and also into the attacker’s account (but only for a specific path).


Defenses (cont.)• Protect special actions by requiring the user to

submit their password along with the request.• This request under the attacker’s account would fail.• The attacker could still force the victim into their

account for other portions of the site.

• Make blatant the account that the user is logged in to and put everything under one path/url and track navigation through the query string.• Lots of bad ideas. So maybe just fix the XSS issues.


How Login Should Work

Browser Servergood.com

1. Get Login Page


2. Submit Credentials


3. Get Redirected Past Login


How CSRF Login Works

Browser Serverevil.com

1. Go To Attacker’s URL

Browser Servergood.com2. Submit Attacker’s Credentials


3. Get Redirected Past Login


Login CSRF Defenses• Standard CSRF protection is not sufficient. An

attacker could get an anti-csrf token and force the victim to send it with the attacker’s credentials.• A pre-login cookie tied to the anti-csrf token would

stop this.• If the attacker can set the pre-login cookie on the

victim’s browser, then it would still work.• Referer header checking is usually not

recommended for CSRF protection. It could work here where common cookie/token methods don’t. • The Referer has to match the domain exactly.


Conclusions• But why?!• Tell me your secrets (dropbox, tax prep)• Do my homework (fiverr.com, online poker)• I was framed! (HR scandals, repudiation)

• How?• Cookie based (can be path specific)• Login Cross Site Request Forgery (whole site)

• I would notice!• Cookie based can target a single POST page where the

user sees nothing.

• What do I do? • Protect your entire domain from XSS• Specifically stop Login CSRF


Questions & Discussion

Date post:	22-Jun-2015
Category:	Internet
Upload:	benlbroussard
View:	203 times
Download:	0 times

Account entrapment

Internet