Java Security

1
George Blank University Lecturer
2
Java Security
3
Overview of Java Security features

• Java Technology uses three mechanisms to ensure
  safety.
• Language design features(bounds checking on
  arrays,legal type conversions etc).
• An access control mechanism that controls what
  the code can do(file access, network access etc).
• Code signing code authors can use standard
  cryptographic algorithms to authenticate java
  programming language code. Users of the code can
  determine who created the code and whether the
  code is altered or not after it was signed.

4
Java 2 Security Architecture
5
Byte Code Verifier

• Checks a classfile for validity
• Code should have only valid instructions and
  register use.
• Code does not overflow/underflow stack.
• Does not convert data types illegally.
• Accesses objects correct types.
• Method calls use correct number and types of
  parameters.
• References to other classes use legal names.

6
Class Loaders

• Is an important link in security chain and loads
  java byte codes into the JVM.
• It works in conjunction with the security manager
  and access controller to enforce security rules.
• It is involved in enforcing some security
  decisions earlier in an objects lifetime than the
  security manager.
• Information about the URL from which the code is
  originated and the codes signers is initially
  available to the ClassLoader.

7
Class Loaders

• Customized ClassLoader or a subclass from
  java.security.SecureClassLoader provides security
  features beyond the standard Java2 security
  model.
• ClassLoader loads classes into VM and is
  responsible for the namespaces at runtime.
  Namespaces as identically named identifiers can
  reference different objects.
• Primordial class loader loads bootstrap classes
  in a platform-dependent manner.
• System classes, some classes in java. package
  are essential to the JVM and the runtime system
  are loaded by System ClassLoader.

8
Code Source

• Java Code is downloaded over a network, so the
  code's signature and author are critical to
  maintain a secure environment.
• The object java.security.CodeSource describes a
  piece of code.
• CodeSource encapsulates the code's origin, which
  is specified as an URL.
• Set of digital certificates containing public
  keys corresponding to the set of private keys are
  used to sign the code

9
Security Policy Files

• SecureClassLoader assigns permissions when
  loading classes, by asking policy object to look
  up the permissions for the code source of each
  class.
• Own Policy class can be installed to carry out
  mapping from code sources to permissions.

10
Security Policy Files

• Example of a policy file
• grant codebase www.horstmann.com/classes
• permission java.io.Filepermission /tmp/ ,
  read, write
• The above file grants permission to read and
  write files in the /tmp directory to all code
  that was downloaded from
• www.horstmann.com/classes

11
Security Policy Files

• Policy files can be installed in standard
  locations and the two default locations are
• The file java.policy in the java platform home
  directory.
• The file .java.policy in the user home directory.
• The locations of these files in the
  java.security configuration files can be changed

12
Security Policy Files

• During testing standard files are not modified
  and hence policy file is required for each
  application.
• For this purpose place permissions into a
  separate file such as MyApp.policy and start the
  interpreter as
• java Djava.security.policyMyApp.policy MyApp
• For applets
• appletviewer J-Djava.security.policyMyApplet.po
  licy
• 
  MyApplet.html

13
Security Policy Files

• In the previous example MyApp.policy file is
  added to other policies in effect. If you add a
  second equal sign, such as
• java Djava.security.policyMyApp.policy MyApp
• then your application uses only the specified
  policy file and standard policy files are ignored.

14
Security Policy Files

• Policy file contains a sequence of grant entries.
  Each entry has the following form.
• grant codesource
• permission_1
• permission_2
• ..
• The code source contains a code base and the
  names of trusted certificate signers.
• The code base is specified as Codebase url

15
Security Policy Files

• If the code base url ends with a /, it refers to
  a directory, otherwise it is taken as a JAR file.
• grant codebase www.horstmann.com/classes/
• grant codebase www.horstmann.com/classes/MyApp
  .jar
• The code base is an url and should always contain
  forward slashes as file separators, even for
  urls in windows.

16
Permissions

• Permission classes represent access to various
  system resources such as files, sockets and so
  on.
• Collection of permissions can be construed as a
  customizable security policy for an installation.
• Permission classes represent approvals, but not
  denials.
• Permissions granted to a ProtectionDomain also
  called "privileges"

17
Permission Subclasses

• File permission class.
• Gives rights to local files/directories.
• Path name/pattern.
• Specific pathfile,directory,directory/file.
• All files in directory directory/.
• All files recursively in directory
  directory/-.
• For current directory, omit "directory/."
• For all files (dangerous), "ltltAll Filesgtgt."
• Rights set (1) read,write,execute,delete.

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Socket Permission

• Host.
• Local Machine "local host."
• Given machine IP address or hostname.
• All hosts in a domain .domain.
• All hosts .
• Portrange.
• Single port portnumber.
• Port range port1-port2, port1-,-port2.
• Actions(1) accept,connect,listen,resolve.

19
PropertyPermission

• Gives rights to properties.
• Similar to OS environment variables.
• Target.
• Specific property os.name.
• Pattern java..
• Actions (1) read,write.

20
Other Permission SubClasses

• Runtime Permission string with permission name
• - createClassLoader
• - getClassLoader
• - setSecurityManager
• - exitVM

21
Policy Files for Homework

• On your homework assignments, you will want to
  think about permissions for the client and
  server, and make sure you give permissions for
  both the host name or IP address and the port
  number. You may also need access to ports on the
  local host to access utilities like HTTP for an
  applet. Example
• grant
• permission java.net.SocketPermission
• "afs1.njit.edu1950-2000","connect,accept,resolve"
  
• permission java.net.SocketPermission
• "afs1.njit.edu80","connect"

22
Security Manager

• The class java.lang.SecurityManager is the focal
  point of authorization.
• SecurityManager is concrete, with a public
  constructor and appropriate checks in place to
  ensure that it can be invoked in an authorized
  manner.
• It consists of a number of check methods.
• eg CheckPermission method is used to check to
  see if the requested access has the given
  permission based on policy.

23
AccessController

• The java.security.AccessController class is
  used for three purposes.
• To decide whether access to a critical system
  resource should be allowed or denied, based on
  the security policy currently in effect.
• To mark code as privileged, thus affecting
  subsequent access determinations.
• To obtain a snapshot of the current calling
  context, so access-control decisions from a
  different context can be made with respect to the
  saved context.

24
Keystore

• Keystore is a password-protected database that
  holds private keys and certificates.
• The password is selected at the time of creation.
• Each database entry can be guarded by its own
  password for extra security.
• Certificates accepted into the keystore are
  considered to be trusted.

25
Core Security

• Java 2's security pieces reside primarily in
• java.lang
• java.security
• java.security.cert
• java.security.interfaces
• java.security.spec

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Core Security

• Java.lang.
• Contains the SecurityManager class, which allows
  applications to implement a security policy.
• The SecurityManager determines the operation's
  identity and whether it can be performed in its
  security context.

27
Core security

• java.lang
• The manager contains many methods that begin with
  the word check.
• Eg.
• SecurityManager security System.getSecurityMa
  nager()    if (security ! null)
          security.checkXXX(argument,  . . .
  )    

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Core security

• java.security.
• Contains most security classes and interfaces.
• It contains classes for access control,
  parameters for the various cryptographic
  algorithms, code source, guarded objects, key
  management, message digests, permission, policy,
  protection domains, providers, secure class
  loaders, random number generators, and digital
  signatures.
• The following Java code can be used to produce a
  permission to read files in the /tmp directory.
• FilePermission p new FilePermission("/tmp/",
  "read")

29
Core Security

• java.security.
• Entries in the policy file can also be used
  to achieve similar results. The following is a
  sample entry in the policy file that indicates
  the granularity of providing access.
• // Sample policy filegrant signedBy
  "signer_names", codeBase "URL"     permission
  permission_class_name "target_name",
  "action",    signedBy "signer_names"    

30
Core Security

• Many classes provide a Service Provider Interface
  (SPI) for providers to plug in their
  implementations. Examples include MessageDigest,
  Signature, KeyPairGenerator, and so on.
• The MessageDigest class supports the MD5 and SHA
  algorithms.

31
Core Security

• The getInstance() method is invoked to select the
  appropriate algorithm.
• The method update() is called to ready the input
  buffer, while the digest() method generates a
  message digest, the size of which (in this case,
  128 bits, or 16 bytes) depends on the algorithm
  (in this case, MD5).
• The digest() method would generate 160 bits (20
  bytes) for the digest if the SHA algorithm was
  used.

32
Core Security

• The java.security.cert package deals with
  certificates. It provides, for instance, an
  abstract class to import, generate, and verify
  X.509 certificates.
• The java.security.interfaces package is a set of
  interfaces used to generate DSA and RSA key
  pairs.
• The java.security.spec package may be used to
  control the parameters for various algorithms,
  like DSA or RSA, and their corresponding keys.

33
Authentication

• Authentication is tremendously important in
  computer applications.
• The program or person you communicate with may be
  in the next room or on another continent you
  have none of the usual visual or aural clues that
  are helpful in everyday transactions.
• Public key cryptography offers some powerful
  tools for proving identity.

34
Web Authentication

• There are several different ways that
  authentication normally occurs on the Internet.
• The next slide lists five methods, with slides
  following it to describe those methods.

35
Understanding Login Authentication

• When you try to access a protected web resource,
  the web container activates the authentication
  mechanism that has been configured for that
  resource. You can specify the following
  authentication mechanisms
• HTTP basic authentication
• Form-based login authentication
• Client certificate authentication
• Mutual authentication
• Digest authentication

36
HTTP Authentication

• With basic authentication, the following things
  occur
• A client requests access to a protected resource.
• The web server returns a dialog box that requests
  the user name and password.
• The client submits the user name and password to
  the server.
• The server validates the credentials and, if
  successful, returns the requested resource.

37
Form Authentication

• With form-based authentication, the following
  things occur
• A client requests access to a protected resource.
• If the client is unauthenticated, the server
  redirects the client to a login page.
• The client submits the login form to the server.
• If the login succeeds, the server redirects the
  client to the resource. If the login fails, the
  client is redirected to an error page.

38
Certificate Authentication

• In certificate-based authentication, the
  following things occur
• A client requests access to a protected resource.
• The web server presents its certificate to the
  client.
• The client verifies the server's certificate.
• If successful, the client sends its certificate
  to the server.
• The server verifies the client's credentials.
• If successful, the server grants access to the
  protected resource requested by the client.

39
Password Authentication

• In user name- and password-based mutual
  authentication, the following things occur
• A client requests access to a protected resource.
• The web server presents its certificate to the
  client.
• The client verifies the server's certificate.
• If successful, the client sends its user name and
  password to the server, which verifies the
  client's credentials.
• If the verification is successful, the server
  grants access to the protected resource requested
  by the client.

40
Digest Authentication

• Like HTTP basic authentication, HTTP digest
  authentication authenticates a user based on a
  user name and a password. However, the
  authentication is performed by transmitting the
  password in an encrypted form which is much more
  secure than the simple base64 encoding used by
  basic authentication. Digest authentication is
  not currently in widespread use.

41
Cryptographic Concepts

• Message digests produce a small "fingerprint" of
  a larger set of data.
• Digital signatures can be used to prove the
  integrity of data.
• Certificates are used as cryptographically safe
  containers for public keys.

42
Message Digest

• A message is used to avoid transmitting a
  password in clear text from a client to a server.
• A message digest takes an arbitrary amount of
  input data and produces a short, digested version
  of the data.
• Java Cryptography Architecture (JCA) makes it
  easy to use message digests.
• The java.security.Message Digest class
  encapsulates a cryptographic message digest.

43
Protected Password Login

• A basic problem in client/server applications is
  that the server wants to know who its clients
  are.
• The obvious solution is to send the user's name
  and password directly to the server.
• Most computer networks, are highly susceptible to
  eavesdropping, so this is not a very secure
  solution.
• To avoid passing a clear text password from
  client to server, we can send a message digest of
  the password instead.

44
Protected Password Login

• The server can create a message digest of its
  copy of the password. If the two message digests
  are equal, then the client is authenticated.
• This simple procedure is vulnerable to a replay
  attack.
• To avoid this problem some session specific
  information like random number and a time stamp
  are added to the message digest.
• The server can use them to calculate a matching
  digest value.

45
Message Digest Password
46
Double-Strength Password Login

• This is a stronger method for protecting password
  information using message digests.
• Why is it Required?
• A message digest is one way function
• It takes less time to test a single password
  using dictionary attack
• A dictionary attack is to try passwords one at a
  time and attempting to login each time
• It increases the time required for a dictionary
  attack

47
Double-Strength Password Login
48
Signatures

• A signature provides two security services,
  authentication and integrity.
• A signature is a message digest that is encrypted
  with the signer's private key.
• Only the signer's public key can decrypt the
  signature, which provides authentication.
• If the message digest of the message matches the
  decrypted message digest from the signature, then
  integrity is assured.
• The Java Security API class, java.security.Signatu
  re represents cryptographic signatures.

49
Signatures

• The basic procedure is very similar to the
  password based.
• The client generates a timestamp and a random
  number.
• The client creates a signature of this data and
  sends it to the server.
• The server can verify the signature with the
  client's public key.

50
Limitations with Signatures

• Signatures do not provide confidentiality. A
  signature accompanies a plain text message.
  Anyone can intercept and read the message.
• Creating and maintaining the public key database
  is difficult.
• The server needs to obtain these public keys in a
  secure way.
• Certificates solve this problem.

51
Certificates

• A certificate is a statement, signed by one
  person, that the public key of another person has
  a particular value.
• It's like a driver's license.
• The license is a document issued by your state
  government that matches your face to your name,
  address, and date of birth.
• Note that the license only has value because you
  and your local shopkeepers trust the authority of
  the state government.
• Digital certificates have the same property.

52
Certificates

• Certificate associates an identity with a public
  key.
• The identity is called the subject.
• The issuer that signs the certificate is the
  signer.

53
Elements of a Certificate

• Information about the subject.
• The subject's public key.
• Information about the issuer.
• The issuer's signature of the above information

54
Java Cryptography Overview

• The Java Cryptography Architecture is split into
  two different packages
• JDK
• Java Cryptology Extension
• Sun had to split the architecture due to US
  export laws which prohibits software encryption
  technology from being released outside of the
  United States or Canada (certain types of
  cryptographic software are considered "weapons"
  by the U.S. government).

55
Service Classes

• Signature Used to sign and verify digital
  signatures.
• Message Digest Used to calculate the message
  digest (hash) of specified data.
• KeyPairGenerator Generate a pair of public and
  private keys suitable for a specific algorithm.
• KeyFactory Converts cryptographic keys of type
  'key' into key specifications.
• AlgorithmParameterGenerator Generates
  parameters for a particular algorithm.

56
Service Classes in JDK1.2

• AlgorithmParameters Manages the parameters for
  a particular algorithm.
• KeyStore Used to create and manage a key store.
• SecureRandom Generates pseudo random numbers.

57
Java Cryptography Extension

• The JCE removes users from the implementation of
  cryptography, and the algorithms involved, making
  both easy to use.
• A programmer can specify algorithms, or the JCE
  architecture will choose the default algorithms.
• An application that uses an object that needs a
  specific CSP service or algorithm will run
  through the installed providers, and choose the
  first default provider with an appropriate
  service.
• Alternately programmers can choose specific
  providers for specific services.

58
Cryptographic Service Providers

• RSA Data Security Inc.
• eSec Limited (formally Australian Business Access
  )
• Forge Research.
• DSTC
• Entrust Technologies
• Cryptix
• IAIK

59
Enterprise Solutions

• This has been a rather basic introduction to Java
  Security. When you get to large applications
  with many users, there are additional concerns,
  normally at the level of Web servers and Java 2
  Enterprise Edition.
• The following slides introduce those concerns.

60
Too many users?

• Since Web Applications can have large numbers of
  users, it may not be convenient to control
  security at the user level.
• The following slide shows ways that this
  complexity can be managed.

61
J2EE Security classifications

• User An individual (or application program)
  identity that has been defined in the Application
  Server. Users can be associated with a group.
• Group A set of authenticated users, classified
  by common traits, defined in the Application
  Server.
• Role An abstract name for the permission to
  access a particular set of resources in an
  application. A role can be compared to a key that
  can open a lock. Many people might have a copy of
  the key. The lock doesn't care who you are, only
  that you have the right key.
• Realm A collection of users and groups that are
  controlled by the same authentication policy.

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References and Resources

• Inside Java 2 Platform Security, Li Gong, Addison
  Wesley, 1999.
• Java Cryptology, Jonathon Knudsen, O'reily and
  Associates, 1998.
• Java Security Handbook, Jamie Jaworski and Paul
  Perrone, SAMS Publishing, 2000.