1. COSC 4301 - Assignment 3 - Part 1
Java Security
Susan Kovacs
19 April 2019
COSC Assignment 3 - Part 1

2. COSC 4301 - Assignment 3 - Part 1
Topics of Discussion
Why is security an issue?
Types of security breaches
Java’s approach
the Language
the Libraries
Browsers
Conclusion
19 April 2019
COSC Assignment 3 - Part 1

3. Why is security an issue?
4/19/2019
Why is security an issue?
What is an applet?
A Java program that is run from inside a web browser. The html page loaded into the web browser contains an <applet> tag, which tells the browser where to find the Java .class files. For example,
Ask if anyone can define what an applet is.
Explain what it is.
Example.
Ask why we use applets. Answer: Executable Content
Define executable content: the idea of sending around data that is actually code to be executed.
This is exciting because it provides power and expressiveness.
Html tags & scripts that run on servers are extremely limited.
Java’s portability property make it the perfect candidate.
appletviewer
19 April 2019
COSC Assignment 3 - Part 1

4. Why is security an issue?
4/19/2019
Why is security an issue?
The class files for an applet are automatically downloaded when a user goes to the containing Web page in a browser. It is therefore likely that a user will encounter applets from untrusted sources. Without any security, this would be a convenient way to spread viruses.
19 April 2019
COSC Assignment 3 - Part 1

5. COSC 4301 - Assignment 3 - Part 1
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Types of breaches
Integrity Attacks
Availability Attacks
Disclosure Attacks
Annoyance Attacks
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COSC Assignment 3 - Part 1

6. COSC 4301 - Assignment 3 - Part 1
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Types of breaches
Integrity Attacks
Deletion / modification of files
Modification of memory currently in use
Killing processes / threads
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COSC Assignment 3 - Part 1

7. COSC 4301 - Assignment 3 - Part 1
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Types of breaches
Availability Attacks
Allocating large amounts of memory
Creating thousands of windows
Creating high priority process / threads
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COSC Assignment 3 - Part 1

8. COSC 4301 - Assignment 3 - Part 1
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Types of breaches
Disclosure Attacks
Mailing information about your machine
/etc/passwd
Sending personal or company files to an adversary or competitor over the network
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COSC Assignment 3 - Part 1

9. COSC 4301 - Assignment 3 - Part 1
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Types of breaches
Annoyance Attacks
Displaying obscene pictures on your screen
Playing unwanted sounds over your computer
19 April 2019
COSC Assignment 3 - Part 1

10. COSC 4301 - Assignment 3 - Part 1
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Java’s Approach ...
The Language
The Libraries
Browsers
19 April 2019
COSC Assignment 3 - Part 1

11. COSC 4301 - Assignment 3 - Part 1
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The Language
Access control
Type-safe
Absence of pointers
Garbage collection
Packages
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COSC Assignment 3 - Part 1

12. COSC 4301 - Assignment 3 - Part 1
4/19/2019
The Language
Access control
public
private
final
Access to methods and variables is controlled via keywords
public
private
final
for example the File object - has a public method that can be called by anyone and a low level private method. The public method first performs security checks and then calls the private method
final prevents a malicious programmer from subclassing a critical library class or overriding the methods of a class
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COSC Assignment 3 - Part 1

13. COSC 4301 - Assignment 3 - Part 1
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The Language
Type-safe
The compile time type and runtime type of variables are guaranteed to be compatible.
Prevents the forging of access to objects to get around access control.
File example: prevents the malicious code from casting a File object to the malicious code’s MyFile type which has the same layout as the File type but with all methods public.
19 April 2019
COSC Assignment 3 - Part 1

14. COSC 4301 - Assignment 3 - Part 1
4/19/2019
The Language
Absence of pointers
Pointers cannot be directly manipulated by user code.
Prevents both malicious and accidental misuse of pointers.
19 April 2019
COSC Assignment 3 - Part 1

15. COSC 4301 - Assignment 3 - Part 1
4/19/2019
The Language
Garbage collection
Manual deallocation provides a round-about way of illegally casting.
Java uses garbage collection to recover unused memory instead of relying on explicit user deallocation.
Example:
malicious code creates a new object of type MyFile,
deallocates the memmory used by that object, keeping the pointer
malicious code creates a File object which has the same size
the new pointer can be made to be the same as the MyFile pointer
malicious code can now access the private methods of the File object
19 April 2019
COSC Assignment 3 - Part 1

16. COSC 4301 - Assignment 3 - Part 1
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The Language
Packages
Provides namespace encapsulation.
Prevents downloaded code from shadowing system library code with malicious code.
Usefull because they allow downloaded code to be easily distinguished from local code
Java guarantees that when a class is referenced the system first looks in the local namespace and then in the namespace of the referencing class
19 April 2019
COSC Assignment 3 - Part 1

17. COSC 4301 - Assignment 3 - Part 1
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The Libraries
Security Manager
Class Loader
19 April 2019
COSC Assignment 3 - Part 1

18. COSC 4301 - Assignment 3 - Part 1
4/19/2019
The Libraries
Security Manager
Contains methods which are intended to be called to check specific types of actions.
It is intended to be subclassed and used to instantiate the desired security policy.
Will use security manager when creating library code for a potentially dangerous system resource
Examples: see sheet
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COSC Assignment 3 - Part 1

19. COSC 4301 - Assignment 3 - Part 1
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The Libraries
Security Manager
Example:
Public boolean mkdir(String path) throws IOException {
SecurityManager security = System.getSecurityManager();
if (security != null)
security.checkWrite(path);
return mkdir0(); }
Will use security manager when creating library code for a potentially dangerous system resource
Examples: see sheet
19 April 2019
COSC Assignment 3 - Part 1

20. COSC 4301 - Assignment 3 - Part 1
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The Libraries
Class Loader
Class loaders are responsible for importing binary data that defines the running program’s classes and interfaces.
Two type: primordial & object
To make applets as portable as possible, Java compiler doesn’t compile to machine code but only to bytecode.
That’s what the class loader deals with
difference between primordial & object:
the primordial is part of the JVM implementation & there’s only one of them
class loader objects are written in Java, compiled into class files, loaded into the virtual machine and instantiated
all applet windows come up with a warning - because they’re not trusted because they’re loaded by an object class loader
19 April 2019
COSC Assignment 3 - Part 1

21. COSC 4301 - Assignment 3 - Part 1
4/19/2019
The Libraries
Class Loader
Due to JVM’s approach to loading classes, classes can by default only see other classes that were loaded by the same class loader.
This allows for multiple name-spaces inside a single Java application
To make applets as portable as possible, Java compiler doesn’t compile to machine code but only to bytecode.
That’s what the class loader deals with
difference between primordial & object:
the primordial is part of the JVM implementation & there’s only one of them
class loader objects are written in Java, compiled into class files, loaded into the virtual machine and instantiated
read two other pages
19 April 2019
COSC Assignment 3 - Part 1

22. COSC 4301 - Assignment 3 - Part 1
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Browsers
The Web browser defines and implements a security policy for running downloaded Java code.
A Java enabled web browser includes:
Java interpreter and runtime libraries
classes to implement a Security Manager
various Class Loaders
It is in the browser that the class loaders & security managers become crucial.
19 April 2019
COSC Assignment 3 - Part 1

23. COSC 4301 - Assignment 3 - Part 1
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Examples
import java.awt.*;
import java.io.*;
import java.lang.*;
import java.applet.*;
public class exitTest extends Applet {
public void paint(Graphics g) {
try { Runtime.getRuntime().exit(-1); }
catch (SecurityException e) {
g.drawString("Caught security exception trying to quit", 10, 10); }
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COSC Assignment 3 - Part 1

24. COSC 4301 - Assignment 3 - Part 1
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Examples
Conclusion:
An applet can't kill the browser that loaded it, unless you load the applet from a directory on your CLASSPATH.
For further examples please visit
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COSC Assignment 3 - Part 1

25. COSC 4301 - Assignment 3 - Part 1
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Conclusion
In order for a program to be useful, it needs to access certain resources.
Therefore, the key is not to deny all access but rather to provide secured access in a controlled environment.
Though Java is not yet perfected, it’s features and properties have allowed for a good balance of power and security.
19 April 2019
COSC Assignment 3 - Part 1

26. COSC 4301 - Assignment 3 - Part 1
Questions ...
THANK YOU!
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COSC Assignment 3 - Part 1

27. COSC 4301 - Assignment 3 - Part 1
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References
Flanagan, David. Java in a Nutshell. 2nd Ed. O’Reilly, California, 1997
Bank, Joseph. Java Security March 2004
Venners, Bill. Security and the class loader architecutre March 2004
Applet Security March 2004.
19 April 2019
COSC Assignment 3 - Part 1