George Blank University Lecturer

Java Security

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.

Java 2 Security Architecture Bootstrap class files System class files User class files Bytecode Verifier Bootstrap ClassLoader System ClassLoader Security ManagerProtection Domains AccessController Operating System Hardware Permissions Keystore CodeSource(URL, Certificates) Policy Database

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.

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 code’s signers is initially available to the ClassLoader.

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.

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

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.

Security Policy Files Example of a policy file: grant codebase { 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

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

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.policy=MyApp.policy MyApp For applets appletviewer –J-Djava.security.policy=MyApplet.policy MyApplet.html

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.policy==MyApp.policy MyApp then your application uses only the specified policy file and standard policy files are ignored.

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”

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 “ grant codebase “ {…} The code base is an url and should always contain forward slashes as file separators, even for url’s in windows.

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"

Permission Subclasses File permission class. Gives rights to local files/directories. Path name/pattern. Specific path:file,directory,directory/file. All files in directory: directory/*. All files recursively in directory: directory/-. For current directory, omit "directory/." For all files (dangerous), " >." Rights set (1+): read,write,execute,delete.

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.

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

Other Permission SubClasses Runtime Permission: string with permission name - createClassLoader - getClassLoader - setSecurityManager - exitVM

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.edu: ","connect,accept,resolve"; permission java.net.SocketPermission "afs1.njit.edu:80","connect"; };

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.

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.

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.

Core Security Java 2's security pieces reside primarily in: java.lang java.security java.security.cert java.security.interfaces java.security.spec

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.

Core security java.lang The manager contains many methods that begin with the word check. Eg. SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkXXX(argument,... ); }

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");

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 file grant signedBy "signer_names", codeBase "URL" { permission permission_class_name "target_name", "action", signedBy "signer_names"; };

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.

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.

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.

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.

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.

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

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. HTTP 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. Form 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. Certificate 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. Password Authentication

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.

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.

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.

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.

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.

Message Digest Password

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

Double-Strength Password Login

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.Signature represents cryptographic signatures.

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.

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.

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.

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

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

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).

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.

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.

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.

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

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.

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.

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. J2EE Security classifications

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