ethical hacking -webapplicationsecurity

8/7/2019 Ethical Hacking -Webapplicationsecurity

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Web & Desktop

Application SecurityRafel Ivgi

Security-Art

1 Web & Desktop Application Security


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Who am I?

Over 12 years in development, technology and informationsecurity.

Published more than 100 articles in the field of informationsecurity including MS04-025, MS05-005 .

Was Head of information security research team MCRC at

Finjan in 2004.

Graduate of 8200 technological unit, two times winningpartner of the Israel Defense Award.

Web & Desktop Application Security2


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Who am I?



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Who am I?



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Who am I?



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Table Of Contents XSS Introduction (Reflected XSS)

XSS Introduction (Stored XSS) XSS-Shell

XSS Worms Introduction XSS Worms - the future of SPAM XSS Worms - D.o.S attacks XSS Worms - Automated exploiting bots

Request Validation

White-list vs. Black-list filtering

SQL Injection Introduction

SQL Injection The Practice SQL Injection Taking over the SQL injection as a lead to other vulnerabilities SQL injection Harvesting tools SQL injection Prevention



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Table Of Contents CSRF - Introduction

CSRF The risks and common uses Tokens vs. Personal Information as a solution for CSRF

Un-validated Redirects and Forwards - Introduction Un-validated Redirects and Forwards Common uses and

Risks Validating Redirects and Forwards

Introduction to browser security History stealing using CSS IE 8 anti XSS, is it really safe? Exploiting the Browser Exploiting the Browser Logical exploits

Exploiting the Browser 3rd party extensions

Smart D.o.S

0-day, Hotmail Stored XSS



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Penetration Test Methods

Black box In this type of penetration test, the attackerhave no information regarding the system under

observation.

Gray box in this type of penetration test, the attacker havesome initial information regarding the system, such as:

User and password combination to access inner parts of thesystem.

Network architecture scheme.



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Penetration Test Methods

White box in this type of penetration test, the attacker hasall the information regarding the system, such as:

Source code.

DB access.

Network architecture scheme.

Admin user and password combination.



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XSS Introduction

(Reflected XSS)

XSS is a vulnerability which exists on the server side, butposes a risk only for the servers clients

The attack occurs when a web server replies the user withthe exact raw data received from the user.

In order to exploit the vulnerability:

the attacker supplies the user with a link once clicked, the user sends data to the server the server replies it the browser executes it



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XSS Introduction

(Reflected XSS)

The attacker may send malicious JS code that will execute inthe context of the given site.

This code is able to: Exploit the browser Steal cookies Perform GET and POST requests using the user`s credentials

Perform content spoofing attacks Deface the site



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XSS Introduction

(Stored XSS)

Another vector of this attack is called Stored XSS, unlikethe previous vector, in this attack there is no need to

navigate the user to a specially crafted URL.

This attack requires the attacker to find a permanent placewithin the application that can store his code, for example: blog`s comments

user`s profile settings etc



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XSS-Shell

XSS-Shell is an attack platform designed to be launchedfrom an XSS vector.

The usage of this platform is as following: The attacker sends the user a link referring to a vulnerable site Upon clicking this link the client`s browser runs the JS code of

the XSS-Shell platform

This code hijacks the browser and starts receiving commandsfrom the server The attacker can send new commands that will be evaluated in

the client`s browser as long as this attack is active The client can stop the attack in two ways:

Manually navigate to the different site using the navigation bar

Closing the browser completely



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XSS Worms

In the age of social networks and mash web sites, a singleXSS attack in a major site can be turned into an army of

computers, just waiting for commands from the attacker.

Using the power of JS code there is even no need to try andexploit the browser, most uses of Bot-nets today are D.O.Sand SPAM attacks.



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XSS Worms

The Future of SPAM

While SPAM attacks are still hard to launch using JS, thereare several ways attackers use to achieve this goal.

Mime injections is an uprising attack that allows an attackerto inject text into the mime headers of an outgoing mail andchange the values of those headers before being sent.

The vulnerability is mostly common in Contact Us forms

which lack input validation on fields such as: From To Subject Date and so on



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XSS Worms

the future of SPAM

Correct usage of this vulnerability will allow the attacker tocraft their own email and send it to their victims using the

vulnerable third party site.

This method of SPAM will also bypass the Secure DomainTokens that validates the senders domain.

The attacker can use a XSS worm to take advantage of suchInject-able sites in order to produce a SPAM network with noTrojan Horses or any kind of backdoor tools.



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XSS Worms

the future of SPAM


Original message

Manipulated message oldemail headers becomes hidden

text


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XSS Worms

Information Gathering

Beyond malicious attacks on third party sites, the attackermay use their worm to gather sensitive information from their

victims

The attacker can harvest the following details using the XSSalone: Password (using a perfect phishing attack)

Name Age Email Friend list (that will also be attacked to become future victims)



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XSS Worms

Automated exploiting bots

Another usage of an XSS worm is to automatically scan andexploit other vulnerabilities.

In order to achieve this goal the attacker needs to exploitone of the victim`s browser and execute a backdoor that willact as the server.

The server will then be used by all the other victims or,Fetchers.



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XSS Worms


The Fetchers will send a request to the server asking for anew list to attack.

The server will then use Google or any other search engineto get a list of sites that suit the attack and return it to thefetcher.

The fetcher now asks the server for the content of a certainsite on the list.

Once the value returns, the fetcher parse out the inner linkfrom this page.



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XSS Worms


The fetcher checks for patterns on those links for knownvulnerabilities such as SQL Injections.

For each pattern found, the fetcher tries to exploit themachine using preset values.

Successful exploitations will cause the attacked machine toreport itself to the attacker thus entering to the attack circle.

This may have a low ratio of success but when talking aboutan XSS Worm in the sufficient magnitude and consideringthe fact that this process is fully automatic the result is highlysatisfying for the attacker



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Request Validation

One way of preventing these attacks is to use automatedtools like Request Validation from Microsoft.

This tool blocks HTML characters on every GET and POSTrequest to the server.

While such tools seemingly pose a good solution, the

attacker only has to break them once.



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Request Validation

By Googling how to break .NET request validation onesolution using inline CSS to run JS pops up.

However, in most cases the attacker cannot get to the stagewhere they write inline CSS because the input is notreflected within a HTML tag.



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White-list vs. Black-list filtering Automated tools cannot be trusted on their own, the

application must have a built in inner filtering mechanism.

There are two concepts when talking about filteringmechanisms: Black list White list



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Black-list filtering goes over the input and checks to see ifany preset Bad Keywords appear.

If so, the application either removes them from the input orthrows an exception saying the input is invalid.

The problem with this mechanism is that it`s not 100% proof.

The application will never cover all types of encoding themethods of attacks.



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White list filtering on the other hand sets a template for eachtype of field in the system.

Every input is then compared to the template using regularexpression.

The incompatible parts of the input are removed and the

application is left with a clean value that is known to be safe.



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Vulnerable

Secure



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SQL Injection Introduction

SQL Injection is a vulnerability which exists on the serverside and poses a risk to the Database server of the

application.

The attack occurs when a web server passes the exact rawdata received from the user to the Database server.

In order to exploit the vulnerability: The attacker must identify an input to the application that isinvolved in a database query

Once found, the attacker can manipulate this argument in orderto change the nature of the original query



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SQL Injection Introduction The following VB code generates a SQL statement using a

parameter from the user

In case the value is in the correct template, the application willwork as planned

Select lname, fname FROM users WHERE id=1

Dim SSN as String

Dim SqlQuery as StringSSN = Request.QueryString(ID")SqlQuery = "SELECT lname, fname FROM users WHERE id = '" + ID + "'"

Select lname, fname FROM users WHERE id=1



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SQL Injection Introduction On the other hand, the following input will completelychange the nature of this query:1 or 1=1

The statement will appear as following:

The outcome of the last statement will always result in the

value: true.

An attacker does the same manipulation in the login SQLstatement.

By making sure the statement will always result in true, theattacker is able to instantly log in to the system.


Select lname, fname FROM users WHERE id=1 or 1=1


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SQL Injection The Practice In addition to login credentials the attacker can also go after

the information within the Database itself, for example Credit

Cards.

The attacker can use several vectors when trying to readdata from the SQL server.



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SQL Injection The Practice

Error Based SQL Injection When comparing columns of different types, the SQL server

throws an exception.

In this exception it explains exactly why the statement failed,for example: the attacker can compare the value of the @@version

parameter, which is string, to an integer value

the server in response will say the value of @@version (and

the value itself!) cannot be treated as an integer.



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Error Based SQL Injection



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Union Based SQL Injection In case the server does not output errors or if the attacker

would like a faster way to get the data out of the server theSQL Union statement comes to hand

The following query will act as the test case:

select name from users where user_id=100

the attacker can control the value of user_id and may

manipulate the query as following:

select name from users where user_id=-1 union all selectpassword from users where user_name=admin

instead of the name of the current user logged in, the

application will output the password of the admin user.



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SQL Injection Taking Over the

Machine

An attacker can do more than just read, insert and modifyrecords into the Database.

With the right permissions, an attacker is able to run binarycode on the actual server running the SQL engine.

For example, in MSSQL the procedure xp_cmdshell can be

used to run the code it gets as a parameter with thepermissions of the user running the SQL Server.



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SQL Injection Taking over the machine

In SQL Server 2005 the function was disabled for securityissues, but of course Microsoft left a Reconfigure function

that can turn it back on.

The SQL query will look as following:

; EXEC sp_configure 'xp_cmdshell',1;

RECONFIGURE;EXEC master.dbo.xp_cmdshell 'cmd.exe dir c:';



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SQL Injection Taking over the machine

Another form of action is to use the msiexec function thatdownloads a MSI package and installs it using system

privileges.

Once the attacker has control over the machine they canthen use it as a Bot in order to automatically exploit othervulnerable sites.



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SQL injection as a lead to other

vulnerabilities

Once the attacker has control over the Database server theycan with great ease manipulate the system and create

additional security holes.

For example, the attacker can change data in the SQLServer to bypass all of the input validations against XSSattacks.

This is why the application must always filter the input it gets,and should not consider certain sources as safe.



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SQL injection Harvesting tools

There are a few key applications that make the usage ofSQL injections practically automated.

The number one application will be Pangolin.

Pangolin is designed to extract data from almost every typeof SQL server: MSSQL

MySQL Oracle DB2 and more



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In addition to data extraction Pangolin has the ability to: Execute code on the remote machine

Write files to the remote host Directory and file manager Registry editor Custom SQL statements and more



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SQL injection Prevention

Just like with XSS, there are plug-ins that attempt to preventthese attacks, along with many WAF products in the market.

The problem with these products remains the same, itcannot be a single line of defense. These products getbroken.

The application must have a filtering module that preventsthese attacks on its own.

In the case of SQL Injection the most important part is toencode the parameter before sending it to the SQL Serverso that characters like will have no affect.



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A common problem is the parameters that are not bound byquotes, like integers, these parameters must be validated asan integer before sent further on in the application.

Another vector of prevention is the use of parameterizedqueries inside stored procedures.

This way the variables cannot be treated as SQL CODE butonly as values of those variables.

Once this is done, no matter what the attacker sends as aninput, it could never be parsed as a part of the SQLstatement.



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To add another layer of security, it is recommended to breakdown the stored procedures into smaller units of code.

Each with its own permissions, to avoid a scenario of onestored procedure having both read and write permissions.

In addition, the parameters should be sanitized inside thestored procedures as a last line of defense.



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CSRF - Introduction

Cross Site Request Forgery (CSRF) is a client side attackthat takes advantage of insecure web applications.

To understand this vulnerability let us take a website thathas a user management section: The credentials for the site are saved in the cookie. The site has a Change Password form.



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CSRF - Introduction



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CSRF The risks and common uses

The form has one input, the new desired password.

The attacker also discovered an XSS vulnerability in a hightraffic third party site.

The attacker can use this XSS and cause the victim togenerate a post to the original form on the first site.

The browser will then send an HTTP POST request to thefirst server, it will automatically include the cookie that it hadsaved and the password will change as the attacker desired.



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The attacker can make the user post any form (rather GETor POST method) without the user having any way of

controlling the event.

The user has no way of knowing about the event occurring(without the use of sniffing or analysis tools).



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Most attackers choose the obvious forms to exploit: Password change Password reminder question change

Email change Money transfer



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Tokens vs. Personal Information as a

solution for CSRF

Tokens work in the following way: The user requests a page. The server generates a random token and appends it as a

hidden field to the form. The user fills out the form and submits it back to the server. The server can now compare the token it has saved and the

one received by the user in order to verify the submit processwas legitimate.



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Tokens vs. Personal Information as a

solution for CSRF

Personal Information is used to validate the request islegitimate and human generated.

Two ways are generally used in this method: Old password Security question

The problem with this method of action is that it is not 100%secure, personal information can be found out by theattacker and then the security mechanism has no meaning.

Combining both methods and adding a Captcha mechanismis the best way to defend against this type of attacks.


Unvalidated Redirects and


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Unvalidated Redirects and

Forwards - Introduction Many sites today use redirections and forwards to third party

sites.

Each unvalidated redirection or forward to third party sitesare potentially an attack vector waiting to be exploited.

There are a few risks when talking about

unvalidated referrals.



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Unvalidated Redirects and Forwards

Common uses and Risks The number one use of this unvalidated feature will be to

implement an XSS attack on a third party site.

This XSS cannot affect the referring site, it still uses thatsite`s credibility to unleash the attack.



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Common uses and Risks For example, the following link bypasses the Facebook

redirect checks:

Or coded to the more practical way:

In a more unobvious way:

http://www.facebook.com/l.php?u=http://attacker_site.com&h=781d3

http://www.facebook.com/l.php?u=%68%74%74%70%3a%2f%2f%61%74%74%61%63%6b%65%72%5f%73%69%74

%65%2e%63%6f%6d&h=781d3



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Common uses and Risks Another vector of attack is Content Spoofing.

If the attacker can control the content of a frame inside a

major news web server, they could then create false posts ofinformation that will endanger the credibility of the site inaddition to the profit generated to the attacker.



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Validating Redirects and Forwards The application must validate the URL before forwarding the

user thus assuring the link is safe.

In case the application cannot validate the URL it shouldprompt the user of the redirection before forwarding it.



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Introduction to browser security These days many attackers have realized that owning a

BotNet that can be used to send Spam or to Perform CreditCard frauds and Identity theft is highly profitable.

In order to create these BotNets the attacker uses a numberof methods to get the most off of the users they catch in theirwebs.


Hi t t li i CSS


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History stealing using CSS

One of the most sophisticated logical ways to focus yourattack and gather information on a victim is to steal thebrowser`s history.

This can be done quite easily by any Trojan Horse orSpyware software but what if the attacker does not want toinfect every user with his backdoor?

A good private 0-day vulnerability should not be wasted on

random victims. What if the attacker could know in advance if the potential

victim has a specific online bank account and only then usethe exploit and infect the machine


Hi t t li i CSS


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Stealing the entire history without running code on the

machine is currently not possible.

However it is possible to determine whether a user did or did

not visit a specific URL.

All the attacker needs to do is to generate a list of specific

interesting URLs such as: Bank login pages Social network login pages Common search engines and search values


Histor stealing sing CSS


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Once the list is prepared the attacker can dynamically add anew HREF html tag referring to a link on the list.

It is known that once you click a link it changes color.

What is unknown is the fact that the color of the link can bechecked using CSS.

Then the attacker can simply define a JS loop that checksfor each link if the color is set to the default color or not, inother words - has it been visited or not.




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IE 8 anti XSS is it really safe?


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IE 8 anti XSS, is it really safe?

Microsoft created a mechanism that should protect the usersfrom class-1 XSS vulnerabilities.

The feature was broken in IE8 beta 2, by Mr. Rafel Ivgi, inseveral different ways.

The most critical method was fixed in the final release of theproduct but there are still ways to bypass this defense.




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One of these ways is CRLF.

CRLF (Carriage Return and Line Feed) is a very significant

sequence of characters for programmers.

These two special characters represent the End Of Headermarker (EOH) for many Internet protocols.

In the HTTP protocol, two sequences of these characters are

used as a separation between the headers and messagecontent.



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IE 8 anti XSS, is it really safe? CRLF is considered class-1 XSS.

The difference is that in CRLF you can manipulate the HTTP

headers in additions to the HTML page.

This means that the attacker can override the encodingheader of the original page and set it to UTF-7

Once this is done, the XSS can be encoded using UTF-7

and the XSS-filter does not block the request.

The browser of course renders the page and runs the XSSas it should.




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Exploiting the Browser Logical exploits

Logical exploits take advantage of insecure design rather

then exploiting a classic overflow vulnerabilities.

An example to a logical weakness would be the use of

NetBIOS through Internet Explorer

Allows reading files on the local machine, bypassing all the

domain restrictions and browser protections.

This was vulnerable up until 6 months ago on all windows

operating systems from 9x to windows 7 using any version of

Internet Explorer.


Exploiting the Browser 3rd party


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Exploiting the Browser 3 party

extensions Browser vendors are in an ongoing battle with security

researchers to keep the browser secure and unexploitable: Flash

Adobe acrobat reader Automated download acceleration software Network sniffing and analysis tools


Smart D o S


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Smart D.o.S

A new kind of D.o.S has started to spread.

This method uses a feature in the current web browsers that

is made to prevent users from surfing to malicious websites.

Firefox for example checks using Google's Safe Browsing

whether the site currently requested is safe or not.

In case the result determines that the site is malicious the

browser automatically blocks the connection to the site.


Smart D.o.S


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Smart D.o.S

An attacker can find a vulnerability in a competitive website

for example and plant a public malicious code within the

sites pages.

Within a short time, Google will index the site in question and

discover the exploiting code.

It will then automatically update the Google Safe Browsingdatabase

From now on every attempt to view the site will result with

the following sight:


Smart D.o.S


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Smart D.o.S


Smart D.o.S


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After the site has been indexed as malicious it is highlydifficult to undo the process: The webmaster must find all the instances of the appended

code and remove it. The vulnerability that was used must be blocked or fixing the

problem will only be affective for a short period of time. Contact Google and demand another indexation of the site.

Most webmasters dont have the skills to do the above whichthen requires the hiring of a specialist.

All in all the company under attack has lost a few days ofinternet activity and spent a lot of money dealing with the

outcome of the attack.


0-Day Exploit, Hotmail Stored XSS


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0 Day Exploit, Hotmail Stored XSS


0-Day Technique Bypassing Microsoft


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0 Day Technique, Bypassing MicrosoftRequest Validation

Extensive research leads us to another solution, apparentlyin the Unicode table the Characters appear twice: u001C and uFF1C for

The ones starting with FF are not filtered by Microsoft`s tool.

Meaning this line of defense is broken and every site using itis now vulnerable to the same attack.


Questions?


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Contact Information:


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Jody Keyser

[email protected]

www.aliadocorp.com

1-888-373-0680

Thank You


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