Dissecting Java Server Faces for Penetration Testing

Dissecting Java Server Faces for Penetration
Testing

Aditya K Sood (Cigital Labs) & Krishna Raja (Security Compass)

Version 0.1
August 25, 2011

Abstract
This paper sheds light on the findings of security testing of Java Server
Faces (JSF). JSF has been widely used as an open source web framework
for developing efficient applications using J2EE. JSF is compared with
ASP.NET framework to unearth potential security flaws.

1

Contents
1 Acknowledgments 3

2 Overview 4

3 Inside JSF Framework 5
3.1 JSF Security Architecture . . . . . . . . . . . . . . . . . . . . . . 5
3.1.1 JSF Faces-Config.xml and Web.xml . . . . . . . . . . . . 6

4 Penetration Testing JSF Framework 7
4.1 JSF ViewState Anatomy . . . . . . . . . . . . . . . . . . . . . . 7
4.1.1 Differential Behavior - ViewState in ASP.NET and JSF . 7
4.2 Scrutinizing Padding - Testing Oracle . . . . . . . . . . . . . . . 9
4.2.1 Experiment - Fuzzing Oracle . . . . . . . . . . . . . . . . 11
4.3 JSF Anti CSRF - Truth Behind the Scenes . . . . . . . . . . . . 11
4.3.1 Implementing CSRF Protection - The Right Way . . . . . 13
4.4 Security Descriptors Fallacy - Configuration . . . . . . . . . . . 14
4.4.1 Secure Way of Configuring Security Descriptors . . . . . . 15
4.5 JSF Version Tracking and Disclosure . . . . . . . . . . . . . . . . 16
4.6 JSF Data Validation . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.6.1 JSF 1.2 Validation . . . . . . . . . . . . . . . . . . . . . . 16
4.6.2 JSF 2.0 Validation . . . . . . . . . . . . . . . . . . . . . . 17
4.6.3 Custom Validations . . . . . . . . . . . . . . . . . . . . . 18

5 Conclusion 20

6 About the Authors 21

7 References 22

2

1 Acknowledgments
We would like to thank couple of our friends and security researchers who helped
us in shaping this paper.

• Giorge Maone (NoScript)
• Juliano Rizzo (Netifera)

In addition, we would also like to thank Gary McGraw for providing useful
insight into the paper. A sincere gratitude to all the researchers who are engaged
in constructive research for the security community. Lastly, we sincerely want
to thank our security teams at SecNiche Security Labs and Security Compass
respectively for supporting us in doing security research.

3

2 Overview
In present times, software security has become an indispensable part of software
development life cycle. The penetration testing approach varies with respect to
web development frameworks and platforms. With the advent of advanced level
of attacks, it has become crucial to raise the standards of penetration testing.
An aggressive security testing approach is required to detect the inherent vulner-
abilities and to develop robust security solutions in order to thwart sophisticated
attacks. Owing to the seamless pace of security research, a plethora of vulnera-
bilities are being unearthed in web frameworks and software. Thus, for effective
penetration testing, the security model and web framework architecture should
be dissected appropriately.

OWASP has been used widely as the de facto standard of penetration testing
of web applications and frameworks with its Top 10 attack vectors. However,
the penetration testing methodology should not be constrained to this standard
and must cover the advanced set of attack vectors that should be tested to val-
idate the strength of web frameworks.

This paper is divided into two parts. In the first part, we discuss the internals
of JSF, a Java based web application framework and its inherent security model.
In the second part, we discuss about the security weaknesses and applied security
features in the JSF. In addition, we also raise a flag on the security issues present
in JSF in order to conduct effective penetration testing.

4

3 Inside JSF Framework
Java Server Faces (JSF) is an industry standard and a framework for building
component-based user interfaces for web applications. JSF has certain standards
and is implemented using Reference Implementation (RI) by Sun Microsystems,
Apache MyFaces and Oracles ADF Faces. JSF primarily consists of Java Beans,
Event Driven development and JSF component tree.

With the advent of JSF, the control has been handed over to the devel-
opers for implementing security features such as authorization. As a result of
this change, it has become more crucial for the developers to understand the
implementation of security controls in JSF framework. A good security design
practice requires that authorization (security controls) should be handled at a
central location (Servlet Filter associated with the application front controller).
JSF has built-in extension points provided by the JSF architecture. As JSF
has no proprietary security architecture, the security has to be imposed in a
customized fashion. This is usually done in two ways

• The developer can design a custom ViewHandler that adds security checks
for createView and restoreView. However, it is not considered as the best
security practice because there is no guarantee that the custom security
ViewHandler is executed before the default ViewHandler. This leads to
security exceptions while handling requests from the web clients
• The developer can design a phaseListener that adds security definitions to
restoreView and invokeAction phases. This can be implemented in JSF
faces-config.xml file or the developer can do it dynamically by writing a
customPhase listener.

3.1 JSF Security Architecture
JSF is used for designing web based rich internet applications over the J2EE
framework. Java applications are mostly designed using Model, View, and Con-
troller (MVC) architecture due to the need for real time deployment. J2EE
security can be implemented through Java Authentication and Authorization
Service (JAAS) and container-managed security. JAAS implements fine-grained
access control through external Java permission classes, which provides user with
a list of resources and allowed actions. Before J2EE, the security controls were
implemented within the logic itself. J2EE framework has a declarative security
mechanism in which security controls are applied through web.xml deployment
descriptors which in turn are handled by the J2EE container at runtime. In
container managed security, controls are applied using authorization which is
explicitly enforced on the URL patterns (requests that are issued by the web
client).
Generally, the controller is responsible for implementing security controls
whereas the view and model part are used for hiding information and applying
logic based on the access roles of the user respectively. However, a good design

5

practice suggests that the security should be implemented over all three layers.
as presented in figure 1.

Figure 1: MVC - Model View and Controller Architecture

JSF has implemented the concept of validators which can be used to verify
user input at a view level and model level.

3.1.1 JSF Faces-Config.xml and Web.xml
The rich life cycle of various individual phases are explicitly specified in the faces-
config.xml file. Some of the events included in the file are Restore View, Apply
Request Values, Process Validation, Update Model Values, Invoke Application,
and Render Response. Developers should always consider the fact that faces-
config.xml file has no mention of security and all security constraints must be
specified in web.xml file.

6

4 Penetration Testing JSF Framework
In this section, we are going to present the variation in the applied security
model in JSF frameworks, security weaknesses and the right way to test them.

4.1 JSF ViewState Anatomy
JSF uses ViewState functionality as similar to ASP.NET. However, there are
certain differences in the way JSF and ASP.NET handle ViewState. Generally,
as we all know, the ViewState parameter is used to maintain the state of HTTP
request specific to a web page. This functionality proves beneficial, but it re-
quires appropriate implementation in the deployed environment. It has been
noticed that ViewState analysis of ASP.NET and JSF is misunderstood.

4.1.1 Differential Behavior - ViewState in ASP.NET and JSF
There are number of differences in ViewState implementation in JSF and ASP.NET
which should be taken into consideration while performing analysis of the View-
State. These are discussed as follows

• JSF does not encrypt the ViewState parameters by default. JSF works on
the concept of serialization and compression. In general scenarios, once the
information is serialized, it is compressed using the GZIP algorithm before
being pushed onto a base-64 encoder. Mojarra displays this behavior,
whereas latest versions of Apache My faces perform encryption by default
but MAC is not enabled (prone to padding oracle attack).
• Compression plays a critical role in optimizing requests in JSF and this
is primarily implemented through the ”com.sun.faces.compressViewState”
context parameter. JSF also uses the ”com.sun.faces.compressJavaScript”
context parameter to remove the whitespaces in rendering JavaScript.
However, this parameter does not have much impact on security testing.
• In Apache JSF and Mojarra (SUNs RI), the encryption of ViewState is
only possible through explicit declaration in the Java Naming and Dec-
laration Interface (JNDI) using a password string as presented in listing
1.
<env−e n t r y >
<env−e n t r y −name>com . sun . f a c e s . C l i e n t S t a t e S a v i n g P a s s w o r d </env−
e n t r y −name>
<env−e n t r y −type>j a v a . l a n g . S t r i n g </env−e n t r y −type>
<env−e n t r y −v a l u e >[ P r o v i d e Random Value ] </ env−e n t r y −v a l u e >
</env−e n t r y >
Listing 1: Implementing Encryption using JNDI

• In ASP.NET applications, session state is enabled by default which re-
quires session cookies to navigate through browser sessions, which is well

7

understood. In ASP.Net, the ”ViewStateEncryptionMode.Auto” mode is
set by default which decides whether a specific web page has to have an
encrypted ViewState or not in order to reduce the processing load. How-
ever, it is always advised to encrypt the full ViewState in every webpage
by declaring the ”<%@Page ViewStateEncryptionMode=”Always” %>”
property. This ensures that ViewState data could not be retrieved.
• In ASP.NET, Message Authentication Code (MAC) is also computed by
default and appended in the base 64 encoding in order to avoid the tam-
pering of ViewState with arbitrary data. The biggest problem in imple-
menting MAC is that it has to be explicitly specified on the webpage with
the ”enabledViewStateMac” parameter to be true otherwise MAC is not
enabled by default. It is advised that the MAC key should be larger in size
in order to reduce the attack surface. Usually, the GUID of the machine
is used as a MAC key.

Some of the generic ViewState decoders which fail in JSF may work fine in
ASP.NET ViewState decoding. ViewState decoder designed by plural-sight [2]
fails for JSF and works fine for ASP.NET as it only works in .NET environment.
Figure 2 shows that tool raises red alert while handling JSF ViewState and
should not be used for the analysis of JSF ViewState.

Figure 2: ViewState Decoder Fails for JSF

8

Netifera group has also released a tool termed as POET [3] which should
be used for testing ViewState in JSF. Figure 2 shows the successful decoding
of ViewState in JSF. However, some of the data is gzipped which can be fur-
ther unzipped fully. Even this information raises an alert about the insecure
implementation of ViewState in JSF.

Figure 3: Successful Decoding of ViewState

One can also use the Deface [4],[5] tool for testing ViewState in JSF which
is released by SpiderLabs for aggressive testing of JSF framework.

4.2 Scrutinizing Padding - Testing Oracle
With the advent of new technologies, more sophisticated attack patterns are
being noticed in the routine life. Last year, the discovery of padding oracle at-
tacks [6] has dismantled the implementation of encryption in web frameworks.

9

Due to the padding problem, it is possible to decrypt the ViewState effectively.
In certain versions of ASP.NET, it is possible to download the web.config file on
the local machine by decrypting the content of files using padding oracle attacks.
This is implemented by exploiting the encrypted string that is passed to Scrip-
tResource.axd and WebResource.axd and padding it appropriately. Microsoft
released patches for the insecure cryptographic implementation in ASP.NET due
to padding oracle attacks [10]. It was noticed that some of the applied patches
were not correct and robust. Figure 3 shows how exactly the robustness of
applied patch can be verified.
As demonstrated at IEEE Security Symposium this year, it is possible to
build rogue requests using padding oracle which can be further exploited to
query sensitive information from the web server. This has proved the fact that
erroneous implementation of cryptography [7] can seriously dismantle the system
and the web is no exception.

Figure 4: Checking Validity of Applied Patch [WebResource.axd/ ScriptRe-
source.axd]

This can be successfully done through Padbuster [8] tool in ASP.NET.
However, this tool and its variant successfully work for vulnerable versions of
ASP.NET, provided insecure encryption is applied. This tool has also been
added in the latest version of Backtrack penetration testing framework.

The padding oracle attacks can be successfully conducted in JSF. The first
step is that encryption is not applied in ViewState by default (Mojarra frame-
works). Even if encryption is applied in certain deployed JSF frameworks
(Apache MyFaces) , the integrity is not protected using MAC as discussed
earlier by default. This is the most frivolous flaw that is impacting JSF at

10

a large scale. A number of websites using JSF in a real time environment are
still vulnerable and are running in default insecure state. The ViewState en-
cryption strength in JSF can be checked using POET as discussed. The tool
verifies whether the encryption is applied or not. If it is applied, then it has an
inbuilt module to decrypt the ViewState using oracle padding. The tool follows
the concept of tampering a single byte in the encrypted JSF ViewState (last
block) to verify whether ViewState padding is done appropriately or not based
on HTTP error fingerprinting. JSF usually ignores the inserted block during
serialization which helps the tool to go on decrypting the ViewState without
any hassles. The practical usage of tool can be seen here [9].

4.2.1 Experiment - Fuzzing Oracle
We conducted a number of tests on one of the vulnerable websites to show the
impacts of the padding oracle. The tests are based on manual fuzzing. The aim
is to present the variation in the error responses when encrypted ViewState is
tampered. One thing that should be taken into account while performing this
test is that ViewState has to be encrypted. The test should not be executed
against ViewState that is compressed using GZIP. In addition, the ViewState
should be fuzzed using multiples of 8 because the block size that is used in CBC
encryption has a similar technique. The nature of a response to a padded buffer
varies between applications.

Step 1: Injecting random buffer in ViewState as a multiple of 8. Figure 5
shows how the application reacts.

Step 2: At this point, we got a crypto padding error in step 2, on contin-
uous playing around with padding in ViewState; we received different error as
presented in figure 6.

Considering this scenario, one can continue fuzzing the request, until it is
accepted by the application. There is a typical way of doing padding in CBC
and that can be used in all scenarios as discussed here [11]. One can opt for
various methods to pad CBC encryption.

4.3 JSF Anti CSRF - Truth Behind the Scenes
In reality, JSF does not have an aggressive built-in CSRF protection. Anti
CSRF support is required for protection against Cross Site Request Forging
(CSRF) attacks. However, the implementation of anti CSRF depends a lot on
the design of he in the required framework. ViewState is used for preserving the
state of web pages and can be used in conjunction with another configuration
parameters to prevent CSRF attacks. However, one can perform certain logic
tests to initially detect whether the application is vulnerable to CSRF attacks
or not.

11

Figure 5: Fuzzing Request / Error in Block Size

Generally, if the ViewState is implemented on the server side, then it is a
good security practice that the application should send a ViewState ID token as
a hidden element in the HTML tag so that it can accompany legitimate requests
from the client side. If the application is only implementing ViewState on the
server side and is not using any ViewState ID, then it is possible that CSRF is
not handled appropriately. Tokens generated by using ”javax.faces.ViewState”
(sequential) are easy to guess if not encrypted properly.

<i n p u t t y p e=” h id de n ” name=” j a v a x . f a c e s . ViewState ” i d=” j a v a x . f a c e s .
ViewState ” v a l u e=” j i d 2 ”/>
Listing 2: Implementing ViewState Tracking on Server Side

As presented in listing 2, the j id2 parameter is set for the ViewState track-
ing on the server side. The attacker designs the next request in that session with
ViewState id as j id3, j id4 and so on which will be treated as legitimate by the
server. In Apache MyFaces ”org.apache.myfaces.NUMBER OF VIEWS IN SESSION”
has a default value of 20 where as IBM Web sphere ”com.sun.faces.numberOfViewsInSession”
has 15. These parameters specify the number of views that are stored in the
session when server side state saving is used.

NOTE: In JSF, it is considered that ViewState can be used to prevent CSRF

12

Figure 6: Fuzzing Request / Error in Last Block

attacks when collaboratively used with the JSESSIONID. As we have been dis-
cussing, ViewState implementation matters a lot. Now it has become possible to
re encrypt the tampered ViewState and deliver it back to the server. Encrypting
ViewState and sending data over HTTPS are not the protection mechanisms
against CSRF attacks. This has been widely misunderstood in the developer
community.

4.3.1 Implementing CSRF Protection - The Right Way
Strong CSRF implementation in JSF can be implemented as

• Applying Anti CSRF filters such as ”org.apache.catalina.filters.CsrfPreventionFilter”.
The inbuilt class uses the ”java.util.Random” if explicitly specified by the
developer otherwise ”java.security.SecureRandom” will be used by default.
One can also use OWASP CSRF Guard to integrate third party filters into
JSF.
• If the ViewState session Id is to be used with every request then it must
be strongly encrypted and an appropriate MAC should be applied in order

13

to preserve integrity.
• It is also possible to design custom CSRF filters with strong functions
that generate random tokens. This is possible by creating a CSRF Session
listener class that overrides every request with HTTP listener class and
appends a random token in every request for a particular session. There
is also a possibility of adding <s: token> an element in <h:form> the
tag that automatically initiates the CSRF protection. Framework that
supports <s: token> are Apache Shale, MyFaces and JBOSS Seam.
• The real world examples will look like as presented in listing 3
<i n p u t t y p e=” h id de n ” name=” j i d t 7 : j idt7 CSRFToken ” v a l u e=” 0
c 7 7 6 0 4 0 f f 7 7 d 3 a f 5 a c c e 4 d 4 c 5 9 a 5 1 4 1 1 e b 9 6 0 b d ” />
Listing 3: Implementing CSRF Tokens in JSF

4.4 Security Descriptors Fallacy - Configuration
The declaration of security parameters in web.xml are imperative especially the
security elements that are used for preserving the confidentiality and integrity
of the ViewState. It has been noticed that declaration of ”ALGORTIHM” in
uppercase in ”org.apache.myfaces.ALGORITHM” does not initialize the Initial-
ization Vector (IV) in Apache MyFaces. This is a bad design practice and could
have devastative impacts on the security of a JSF application. The source code
of the ”utils.StateUItils” class (which holds security configuration elements) as
presented in listing 4 which clearly reflects that these parameters have to be ap-
plied in lower case but the documentation of various JSF versions is not written
appropriately and is not inline with the real code. In other words, the docu-
mentation is misleading.

p u b l i c s t a t i c f i n a l S t r i n g INIT PREFIX = ” o r g . apache . my f ac e s . ” ;
p u b l i c s t a t i c f i n a l S t r i n g INIT ALGORITHM = INIT PREFIX + ”
ALGORITHM” ;
p r i v a t e s t a t i c String findAlgorithm ( ExternalContext ctx ) {

S t r i n g a l g o r i t h m = c t x . g e t I n i t P a r a m e t e r (INIT ALGORITHM) ;
i f ( a l g o r i t h m == n u l l )
{
a l g o r i t h m = c t x . g e t I n i t P a r a m e t e r (INIT ALGORITHM .
toLowerCase ( ) ) ;
}
return findAlgorithm ( algorithm ) ;
}

. . Truncated ..
Listing 4: Explicit Specification - Implementing to Lower Case

14

4.4.1 Secure Way of Configuring Security Descriptors
The best practice is to declare the configuration parameters in web.xml as pre-
sented in listing 5.
<c o n t e x t −param>
<param−name>j a v a x . f a c e s . STATE SAVING METHOD</param−name>
<param−v a l u e >c l i e n t </param−v a l u e >
</c o n t e x t −param>

<param−name>o r g . apache . my f ac es . s e c r e t </param−name>
<param−v a l u e >MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIz</param−
value>

<param−name>o r g . apache . my f ac es . a l g o r i t h m </param−name>
<param−v a l u e >AES</param−v a l u e >

<param−name>o r g . apache . my f ac es . a l g o r i t h m . p a r a m e t e r s </param−name
>
<param−v a l u e >CBC/PKCS5Padding</param−v a l u e >

<param−name>o r g . apache . my f ac es . a l g o r i t h m . i v </param−name>
<param−v a l u e >NzY1NDMyMTA3NjU0MzIxMA==</param−v a l u e >

<param−name>o r g . apache . my f ac es . s e c r e t . cache </param−name>
<param−v a l u e >f a l s e </param−v a l u e >

</web−app>
Listing 5: Secure Way of Declaring Encryption Parameters in JSF

This point should be taken into account while doing penetration testing so that
enhanced attacks can be tested against the inappropriate implementation of
JSF security.

NOTE: It has been noticed that JSF framework only encrypts ViewState in
order to provide confidentiality but there is no standard implementation of MAC
by default so that the integrity of ViewState is preserved. While we know that
JSF security greatly depends on the web.xml file, the MAC functionality is also
introduced in it. The developer has to explicitly specify the MAC algorithm,
key and caching.
The parameters that are used nowadays are ”org.apache.myfaces.MAC ALGORITHM”,
”org.apache.myfaces.MAC SECRET” and ” org.apache.myfaces.MAC SECRET.CACHE”
respectively. Always declare all of these parameters in lower case.

15

4.5 JSF Version Tracking and Disclosure
JSF configuration has inbuilt configuration parameters that are used to disclose
the version of the installed framework. However, it is always taken lightly and
is not fixed by the developers or administrators to avoid leakage of the informa-
tion in HTTP response headers. It has been noticed that version disclosure may
result in detecting critical flaws in JSF applications because publicly available
exploit databases can be used to fingerprint the security vulnerabilities present
in the installed JSF framework.

In Suns RI JSF implementation, the ”com.sun.faces.disableVersionTracking”
configuration parameter is defined explicitly. By default, it is set to false which
means application running on the web server will throw the JSF version into
the response headers when the web client queries for it. The collaborative
disclosure of web server version and framework version can be devastative from
the developers point of view but it is fruitful for pen testing purposes. JSF
is not immune to security vulnerabilities [12, 13, and 14] as seen in the recent
past. These security issues should be taken into consideration while deploying
JSF applications because information leakage is the basis of a number of web
attacks. We conducted generic tests on several websites that are using JSF and
found that more than 85% of the websites are throwing JSF version number
in their response headers out of which several of them were running old and
vulnerable versions.

4.6 JSF Data Validation
Anyone involved in security understands the importance of proper input vali-
dation. JSF offers a few different techniques for validation in order to prevent
web attacks such as Cross Site Scripting (XSS). Some of the input validation
modules have been available since JSF 1.2, and others are unique to JSF 2.0.

4.6.1 JSF 1.2 Validation
Apache MyFaces and the Apache Tomahawk library provide JSF components
that can allow for data validation within the UI page itself. One of the more
powerful ways of validating input is by leveraging regular expressions via the
¡t:validateRegExpr¿ tag provided by Tomahawk [15]. Consider an example
where we wish to validate a ZIP code. A MyFaces example of data validation
using Tomahawk [16] is presented in listing 6.

<% t a g l i b u r i=” h t t p : / / my fa c es . apache . o r g /tomahawk” p r e f i x=” t ” %
@ >

<h : o u t p u t L a b e l f o r=” z i p 1 ” v a l u e=” Zip ”/>
<t : i n p u t T e x t v a l u e=”#{o r d e r . zipCode } ” i d=” z i p 1 ”>
<t : v a l i d a t e R e g E x p r p a t t e r n=” d {5} ” message=”ZIP Code”/>
</t : inputText>
Listing 6: Generic MyFaces Example - Tomahawk

16

In this particular example, a regular expression is being used to limit the zip
code to ﬁve digits. Notice that you can include an error message as well, and all
of this is done within the .xhtml page itself. A similar example using Facelets
[17] is presented in listing 7.

<html . . . xmlns : u i=” h t t p : / / j a v a . sun . com/ j s f / f a c e l e t s ” xmlns : t=” h t t p
: / / my f ac es . apache . o r g /tomahawk”>

<h : i n p u t T e x t t y p e=” t e x t ” i d=” v a l
v a l u e=”#{ SimpleBean . v a l }” r e q u i r e d =” t r u e ”>
<t : v a l i d a t e R e g E x p r p a t t e r n=” [ a−zA−Z ] { 1 , 1 0 0 } ” />
</h : inputText>
Listing 7: Generic Facelets Example
The JSF Reference Implementation (RI), codenamed ”Mojarra”, comes with
its own tag library that also leverages regular expressions. Mojarra’s <mj:
regexValidator> will perform the same operation as discussed above. Further-
more, Mojarra’s tag library is armed with an <mj: creditCardValidator> to
validate the proper format of credit cards [18].

4.6.2 JSF 2.0 Validation
JSF 2.0 contains a collection of tags called validators. These are built in to the
JSF 2.0 core library. JSF developers will ﬁnd the following tags particularly
useful for data validation:

• <f:validateLength> : use this to validate that input falls between a mini-
mum and maximum length
• <f:validateLongRange> : use this to validate that numeric input falls
between a minimum and maximum value
• <f:validateDoubleRange> : similar to validateLongRange, but used for
double values
• <f:validateRegex> : use this to leverage regular expression validation

Here is an example of JSF validators in use as presented in listing 8.

<t r >
<td>User ID : <td>User ID :
<h : i n p u t T e x t v a l u e=”#{bidBean2 . u s e r I D } ” r e q u i r e d=” t r u e ”
r e q u i r e d M e s s a g e=”You must e n t e r a u s e r ID”
v a l i d a t o r M e s s a g e=”ID must be 5 o r 6 c h a r s ” i d=” u s e r I D ”>

<f : v a l i d a t e L e n g t h minimum=” 5 ” maximum=” 6 ”/>
</h : inputText ></td>

<td><h : message f o r=” u s e r I D ” s t y l e C l a s s=” e r r o r ”/></td>
</t r >
Listing 8: Generic Usage of JSF Validators

17

Notice in the above example that the <h: inputText> contains a required,
requiredMessage and validatorMessage attribute. The required attribute indi-
cates that this value must be input by the end user and an error message is
displayed if it is not provided.

4.6.3 Custom Validations
All of the above approaches work well when the values are not tied closely to
business logic, or if these validators and tag libraries are suitable to perform
the validation we need. Sometimes there is a need to build custom validation
components for data types that arent supported by standard JSF validators
[19].
In this scenario, the validator attribute of the <h: inputText> tag references
a validator method that is deﬁned within the bean class [20] as presented in
listing 9.
<t r >
<td>Bid Amount : <td>Bid Amount : $<h : i n p u t T e x t v a l u e=”#{bidBean2 .
bidAmount} ” r e q u i r e d=” t r u e ”
r e q u i r e d M e s s a g e=”You must e n t e r an a m o u n t
c o n v e r t e r M e s s a g e=”Amount must be a number”
v a l i d a t o r=”#{ bidBean2 . v a l i d a t e B i d A m o u n t }”
i d=”amount”/>

</td>
<td><h : message f o r=”amount” s t y l e C l a s s=” e r r o r ”/></td>
</t r >
Listing 9: Example : Bid Bean Class

In the BidBean2 class, we would deﬁne our custom validation method as
presented in listing 10, validateBidAmount():
p u b l i c v o i d validateBidAmount ( F a c e s C o n t e x t c o n t e x t , UIComponent
componentToValidate ,
UIComponent componentToValidate , O b j e c t v a l u e ) throws
ValidatorException {

d o u b l e bidAmount = ( ( Double ) v a l u e ) . d o u b l e V a l u e ( ) ;
double previousHighestBid = currentHighestBid ( ) ;

i f ( bidAmount <= p r e v i o u s H i g h e s t B i d )
{
FacesMessage message =
new FacesMessage ( ” Bid must be h i g h e r than
current ”
+ new FacesMessage ( Bid must be h i g h e r than
current + ” h i g h e s t b i d ( $ ”
+ previousHighestBid + ”) . ”) ;
throw new V a l i d a t o r E x c e p t i o n ( message ) ;
}
}
Listing 10: Custom Bean Validator Class

18

As we can see, this approach allows more ﬂexibility while validating input
data. The validators play a signiﬁcant role in curing many security vulnerabili-
ties at the source level.

19

5 Conclusion
In this paper, we have presented the security issues in JSF architecture. Web
frameworks have unique semantics and security models. A thorough under-
standing of the internal architecture of the frameworks is imperative to under-
take productive penetration testing. We have discussed the advance features
that should be tested for complete and extensive penetration testing of JSF.
In general, JSF is similar to ASP.NET from security perspective but diﬀers in
deployment of inherent security controls. Every web framework is required to
be dissected so that step by step testing can be performed in a robust manner.

20

6 About the Authors
Aditya K Sood is a Senior Security Practitioner and PhD candidate at Michi-
gan State University. He has already worked in the security domain for Ar-
morize, COSEINC and KPMG. He is also a founder of SecNiche Security Labs,
an independent security research arena for cutting edge computer security re-
search. He has been an active speaker at industry conferences and already spo-
ken at RSA, HackInTheBox, ToorCon, HackerHalted, Source, TRISC, AAVAR,
EuSecwest, XCON, Troopers, OWASP AppSec USA, FOSS, CERT-IN, etc. He
has written content for Virus Bulletin, HITB Ezine, Hakin9, ISSA, ISACA,
CrossTalk, Usenix Login, and Elsevier Journals such as NESE and CFS. He is
also a co author for debugged magazine.

He is also associated with Cigital Labs for doing applied security research in the
field of software and application security.

Email: adi ks [at] secniche.org

Personal Website: http://www.secniche.org
Company Website : http://www.cigital.com

Krishna Raja is a Senior Application Security Consultant at Security Com-
pass with an extensive background in Java EE application development. He has
performed comprehensive security assessments for financial, government, and
health care organizations across Canada and the United States. Krishna has
carried out the role of security advisor, security analyst, project manager and
trainer. He has given lectures and taught courses at RSA, Source Boston, ISSA
Secure San Diego and OWASP AppSec DC. Krishna graduated from the Uni-
versity of Western Ontario in 2004 with an Honors BSc. in Computer Science
with Software Engineering specialization. He is also an ISC2 Certified Secure
Software Lifecycle Professional (CSSLP).

Email: krish [at] securitycompass.com
Company Website: http://www.securitycompass.com

21

7 References
[1] Apache Java Server Faces, http://myfaces.apache.org/

[2] ViewState Decoder, http://www.pluralsight-training.net/community/media/p/51688.aspx

[3] POET Tool, http://netifera.com/download/poet/poet-1.0.0-win32-x86.jar

[4] Deface Tool, https://github.com/SpiderLabs/deface

[5] Beware of Serialized GUI Objects Bearing Data, http://www.blackhat.com/presentations/bh-
dc-10/Byrne David/BlackHat-DC-2010-Byrne-SGUI-slides.pdf

[6] Padding Oracle Attacks, http://www.usenix.org/event/woot10/tech/full papers/Rizzo.pdf

[7] Cryptography in the Web: The Case of Cryptographic Design Flaws in
ASP.NET, http://www.ieee-security.org/TC/SP2011/PAPERS/2011/paper030.pdf

[8] Automated Padding Oracle Attacks with PadBuster, http://www.gdssecurity.com/l/b/2010/09/14/
automated-padding-oracle-attacks-with-padbuster/

[9] Cracking ViewState Encryption in JSF, http://www.youtube.com/watch?v=euujmKDxmC4

[10] Microsoft Patch Padding Oracle Attacks, http://www.microsoft.com/technet/security/bulletin/ms10-
070.mspx

[11] Using Padding in Encryption, http://www.di-mgt.com.au/cryptopad.html

[12] Sun Java Server Faces Cross-Site Scripting Vulnerability, http://www.securityfocus.com/bid/28192

[13] Apache MyFaces Tomahawk JSF Framework Cross-Site Scripting (XSS)
Vulnerability , http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=544

[14] Sun Glassﬁsh Enterprise Server - Multiple Linked XSS vulnerabilies,
http://dsecrg.com/pages/vul/show.php?id=134

[15] MyFaces Tomahawk, http://myfaces.apache.org/tomahawk/index.html

[16] Tomahawk ValidateRegExpr, http://www.developersbook.com/jsf/myfaces/tomahawk-
tag-reference/tomahawk-validateRegExpr.php#1

[17] Facelets, http://facelets.java.net/

[18] JSF Majorra Extension Tags Validation and Focus, http://java.sys-con.com/node/1031733

22

[19] JSF Validation Tutorial, http://www.mastertheboss.com/web-interfaces/293-
jsf-validation-tutorial.html?showall=1

[20] JSF: Validating User Input, http://courses.coreservlets.com/Course-Materials/pdf/jsf/08-
Validation.pdf

23

Dissecting Java Server Faces for Penetration Testing

More Related Content

What's hot (20)

Viewers also liked (8)

Similar to Dissecting Java Server Faces for Penetration Testing (20)

More from Aditya K Sood (20)

Recently uploaded (20)

Dissecting Java Server Faces for Penetration Testing