Java Web Programming [9/9] : Web Application Security

Module 9: Web Application
Security

Thanisa Kruawaisayawan
Thanachart Numnonda
www.imcinstitute.com

Objectives

General security issues

Authentication

Authorization

Data Integrity

Confidentiality

Web-tier Authentication Schemes
 BASIC
 DIGEST
 FORM
 CLIENT-CERT

Declarative Authorization
2

General Security Issues

Authentication for identity verification
Making sure a user is who he claims he is

Authorization (Access control)
Making sure resources are accessible only to users who have access
privilege

The user has to be authenticated first

Data Integrity
- Making suere that information has not been modified by a third party
while in transit.

Confidentiality (Privacy)
Protecting the sensitive data from prying eyes while it is on the wire 3

Security Requirements at Web-Tier

Preventing unauthorized users from accessing “access controlled”
web resource
If an unauthenticated user tries to access “access
controlled” web resource, web container will automatically
ask the user to authenticate himself first
Once the user authenticated, web container (and/or web
components) then enforces access control

Preventing attackers from changing or reading sensitive data while it
is on the wire
Data can be protected via SSL
4

Web-Tier Security Scheme Should
Address “Authentication”
1. Collecting user identity information from an end user
typically through browser interface
user identity information usually means username and
password
this is called “logging in”

1. Transporting collected user identity information to
the web server
unsecurely (HTTP) or securely (HTTP over SSL)
5

Address “Authentication” (cont.)
1. Performing identity checking with backend “security
database” (Realms)
Web container checks if collected user identity matches with the one in
the backend “security database”
These backend “security database” are called Realms
Realms maintain

Username, password, roles, etc.
How these realms are organized and managed are product and operational
environment dependent

LDAP, RDBMS, Flat-file, Solaris PAM, Windows AD
6

Address “Authentication” (cont.)
1. Web container keep track of previously
authenticated users for further HTTP operations
Using internally maintained session state, web container knows if the
caller of subsequent HTTP requests has been authenticated
Web container also creates HttpServletRequest object for subsequent
HTTP requests

HttpServletRequest object contains “security context”
information
Principal, Role, Username

7

Address “Access control”

Web application developer and/or deployer
specifies access control to web resources
Declarative and/or Programmatic access control

8

Address “Data confidentiality”

Providing confidentiality of the sensitive data
that is being transported over the wire
Between browser and web server
Example: Credit card number
Using SSL

9

Web-tier Authentication Schemes
1. HTTP Basic Authentication
2. HTTP Digest Authentication
3. Form-based Authentication
4. HTTPS Client Authentication

10

1. HTTP Basic Authentication

Web server collects user identification (user
name and password) through a browser
provided dialog box

Not secure since user name and password are
in “easily decode'able” form over the wire
Encoding scheme is Base64
Someone can easily decode it
Not encrypted


Would need SSL for encrypting password
11

Steps for Basic Authentication-based
Web-tier Security
1. Set up username, passwords, and roles (realms)
2. Tell web container that you are using Basic authentication
3. Specify which URLs (web resources) should be access-
controlled (password-protected)
4. Specify which URLs should be available only with SSL
(data integrity and confidentiality protected)

12

Step 1: Set up username, passwords,
and roles (Realms)

Schemes, APIs, and tools for setting up usernames, passwords,
and roles (realms) are web container and operational environment
specific
Flat-file based, Database, LDAP server
Passwords could be in either encrypted or unencrypted form

Tomcat 4.0 can work with the following realms
default: file, unencrypted form
Relational database (via JDBCRealm)
LDAP server (via LDAPRealm)
13

Example: Tomcat's default

<install-dir>/conf/tomcat-users.xml

Unencrypted: not secure but easy to set up and
maintain
<?xml version='1.0' encoding='utf-8'?>
<tomcat-users>
<role rolename="manager"/>
<role rolename="admin"/>
<role rolename="user"/>
<user username="kmitl" password="kmitl" roles="user" />
<user username="root" password="root" roles="manager,admin" />
</tomcat-users>
14

Step 2: Tell web container that you are
using Basic authentication

In web.xml file of your web application
<web-app>
...
<security-constraint>...</security-constraint>
<login-config>
<auth-method>BASIC</auth-method>
<realm-name>realm name</realm-name>
</login-config>
...
</web-app>
15

Step 3: Specify which URLs should
be access-controlled
<web-app>
...
<security-constraint>
<web-resource-collection>
<web-resource-name>WRCollection</web-resource-name>
<url-pattern>/loadpricelist</url-pattern>
<http-method>GET</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>admin</role-name>
</auth-constraint>
<user-data-constraint>
<transport-guarantee>CONFIDENTIAL</transport-guarantee>
</user-data-constraint>
</security-constraint>
<login-config>
<auth-method>BASIC</auth-method> <realm-name></realm-name>
</login-config>
...
</web-app>
16

Step 4: Specify which URLs should be
available only with SSL
<web-app>
...
<auth-constraint>
</auth-constraint>
<login-config>
<auth-method>BASIC</auth-method> <realm-name></realm-name>
</login-config>
... 17
</web-app>

2. HTTP Digest Authentication
 HTTP digest authentication
 The HTTP digest authentication also gets the
username/password details in a manner similar to that
of basic authentication.
 However, the authentication is performed by
transmitting the password in an encrypted form.
 Only some Web browsers and containers support it.

18

3. Form-based Authentication

Web application collects user identification
(user name, password, and other information)
through a custom login page

Not secure since user name and password are
in “easily decode'able” form over the wire
Encoding scheme is Base64
Someone can easily decode it
Not encrypted


Would need SSL for encrypting password
19

Form-Based Auth. Control Flow
Request Response
Page
Login Error Page
Form
1 7 4 5 9
Protected Login.jsp j_security_check Error.html
2 Resource

3
6 8

1. Request made by client 6. Authentication Login succeeded,
2. Is client authenticated? redirected to resource
7. Authorization Permission tested,
3. Unauthenticated client result returned
redirected
8. Login failed, redirect to error page
4 . L og i n f or m r et u r n ed t o cl i en t
9. Error page returned to client
5. Client submits login form
20

Steps for Form-based Authentication based
Web-tier Security
1. Set up username, passwords, and roles (realms): Same as in
Basic-authentication
2. Tell web container that you are using Form-based authentication
3. Create custom “Login page”
4. Create custom “Error page”
5. Specify which URLs (web resources) should be access-
controlled (password-protected)
6. Specify which URLs should be available only with SSL (data
integrity and confidentiality protected)

21

Step 2: Tell web container that you are
using Form-based authentication

In web.xml file of your web application
<web-app>
...
<security-constraint>...</security-constraint>
<login-config>
<auth-method>FORM</auth-method>
<realm-name>realm name</realm-name>
</login-config>
...
</web-app>
22

Step 3: Create custom “Login Page”

Can be HTML or JSP page

Contains HTML form like following

<FORM ACTION="j_security_check" METHOD="POST">
<INPUT TYPE="TEXT" NAME="j_username">
<INPUT TYPE="PASSWORD" NAME="j_password">
</FORM>

23

Step 4: Create Error page

Can be HTML or JSP page

No specific content is mandated

24

Step 5: Specify which URLs should be access-
controlled (Same as Basic Auth)
<web-app>
...
<auth-constraint>
</auth-constraint>
<login-config>
<auth-method>FORM</auth-method> <realm-name></realm-name>
</login-config>
...
</web-app> 25

Step 6: Specify which URLs should be available only
with SSL (Same as Basic Auth)
<web-app>
...
<auth-constraint>
</auth-constraint>
<login-config>
<auth-method>FORM</auth-method> <realm-name></realm-name>
</login-config>
...
</web-app>
26

Basic and Form-based
Form-based

Basic Form-based
• Uses “browser provided • Uses “web application
dialog box” to get provided login page” to
username and get username and
password password
• Only username and • Custom data can be
password can be collected
collected • Can enforce consistent
• Might result in different look and feel
look and feel • Form data is used to
• HTTP Authentication convey username and
header is used to password
convey username and • Can enter a new user
password name via login page
• No good way to enter a 27

4. HTTPS Client Authentication

 HTTPS client authentication
 End-user authentication using HTTP over SSL
(HTTPS) requires the user to possess a public key
certificate (PKC).
 All the data is transmitted after incorporating public
key encryption.
 It is the most secure authentication type.
 It is supported by all the common browsers.

28

Confidentiality of Passwords
 For Basic and Form-based authentication, unless explicitly
specified, the password gets transported in unencrypted form
(Base64)

 The <transport-guarantee> element can contain any of three
values:
 NONE means no transport guarantee
 INTEGRAL means data cannot be changed in transit
 CONFIDENTIAL means the contents of a transmission cannot be
observed
 Example:
<description> Integral Transmission </description>
<transport-guarantee>INTEGRAL</transport-guarantee>
29

Steps for Declarative Authorization at
Web-tier
1. Deployer maps actual user identities to security roles using
vendor specific tools
2. Deployer declares security roles in the deployment
descriptor
3. Deployer declares URL permissions in the deployment
descriptor for each security role

This is already covered above under “Web-tier security
schemes” segment!
30

Declarative and Programmatic
Authorization (Access Control)

They are usually used together
Declarative access control for role-based access
control
Programmatic access control for user instance-
based and business logic based access control

User instance

Time of the day

Parameters of the request

Internal state of the web component 31

Steps for Programmatic
Authorization at Web-tier
1. Set up username, passwords, and roles (realms)
2. Servlet programmer writes programmatic
authorization logic inside the Servlet code using
abstract security roles
3. Deployer maps abstract security roles to actual roles
(for a particular operational environment) in the
web.xml

32

Step 2: Servlet Programmer writes
programmatic authorization logic
public interface javax.servlet.http.HTTPServletRequest{
...
// Find out who is accessing your web resource
public java.security.Principal getUserPrincipal();
public String getRemoteUser();

// Is the caller in a particular role?
public boolean isUserInRole(String role);
...
}

33

Example: “Employees” can only access
their own Salary Information
public double getSalary(String employeeId) {
java.security.Principal userPrincipal =
request.getUserPrincipal();
String callerId = userPrincipal.getName();

// “manager” role can read employee salary information
// employee can read only his/her own salary information
if ( (request.isUserInRole(“manager”)) ||
((request.isUserInRole(“employee”)) &&
(callerId == employeeId)) ) {
// return Salary information for the
employee
getSalaryInformationSomehow(employeeId);
} else {
throw new SecurityException(“access
denied”);
} 34

Acknowledgement
Most contents are borrowed from the
presentation slides of Sang Shin, Java™
Technology Evangelist, Sun Microsystems,
Inc.

Thank you

thananum@gmail.com
www.facebook.com/imcinstitute
www.imcinstitute.com

36

Java Web Programming [9/9] : Web Application Security

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