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Dan Sedlacek CTO, Systems Management Group Sterling Software Java Security and Encryption.

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Presentation on theme: "Dan Sedlacek CTO, Systems Management Group Sterling Software Java Security and Encryption."— Presentation transcript:

1 Dan Sedlacek CTO, Systems Management Group Sterling Software Java Security and Encryption

2 What is the level of security provided by Java technology? What’s NOT provided for in Java How Java implements security How to extend Java security

3 Agenda Java Security Overview Applications and Applets Java Language Security Java Class Loaders Security Manager Access Controller Security Policies Authentication Encryption

4 Java Security Overview What is Security? Virus Protection System Resource Access Control Authentication of Author and Data Data Privacy Encryption Auditing Orange Book (C2, B1)

5 Java Security Overview What is Java Security? Virus Protection - Yes System Resource Access Control - Yes Authentication of Author and Data - Yes Data Privacy - Yes & No Encryption - Optional Auditing - Not Built-in Orange Book (C2, B1) - No

6 Applets and Applications Applets –Run Under Control of a Browser –Are Subject to the Browser Security Policy Applications –Establish their Own Security Policy –Default is No Security Manager

7 Applets Very Restricted Browser Security Manager

8 Applications Allowed to Play Optional Security Manager

9 How Does Java Provide Security? Java Language Security Java Class Loaders Digital Signatures Java Security Manager Java Access Controller Encryption

10 Java Language Security Objects have access levels: –private: Accessible by defining class –package (default): Accessible by classes in the same package –protected: Same as package, with addition of access by any subclass –public: Accessible by any class

11 Java Language Security Access methods are strictly adhered to No pointers (no access to arbitrary memory and automatic garbage collection) “final” methods or variables cannot be changed Variables MUST be initialized before use Array bounds are enforced Strict object casting rules

12 Java Language Security Object serialization can be a problem –Objects are externalized as series of bytes –Data may be tampered with before the object is reconstructed Some solutions: –objects must be declared “serializable” –“private transient” disallows serialization –writeObject() and readObject() methods let you implement your own encryption

13 Java Language Security Enforcement Enforcement happens at different times –Compile time enforcement –Class load time enforcement –Runtime enforcement It’s easy to get around compile-time enforcement - build your own classes for the JVM Class loader and runtime enforcement are more difficult to get around

14 Java Language Security Enforcement Java Source Java Compiler Bytecode Class Loader Bytecode Verifier Java Virtual Machine Runtime

15 Java Language Security Compile Time Enforcement Java Source Java Compiler Bytecode Class Loader Bytecode Verifier Java Virtual Machine Runtime

16 Java Language Security Compile Time Enforcement Validate language syntax Enforce method and variable access rules Enforce variable initialization Enforce some casting operations

17 Java Language Security Class Load Time Enforcement Java Source Java Compiler Bytecode Class Loader Bytecode Verifier Java Virtual Machine Runtime

18 Java Language Security Class Load Time Enforcement Bytecode verifier is part of the VM Bytecode verification –Verifies class file format –Final classes are not subclassed –Final methods are not overridden –Every class has a single superclass (except Object, of course)

19 Java Language Security Class Load Time Enforcement Bytecode verification (continued) –Verify that casting legality checks are in place –No operand stack overflows or underflows –All field and method accesses are legal Bytecode verification may be delayed in some implementations

20 Java Language Security Runtime Enforcement Java Source Java Compiler Bytecode Class Loader Bytecode Verifier Java Virtual Machine Runtime

21 Java Language Security Runtime Enforcement Array bounds checking –Throws ArrayIndexOutOfBoundsException Object casting –Throws ClassCastException Security Manager –Throws SecurityException –Depends on the Access Controller

22 Java Class Loaders Read bytecode into the JVM Convert into class definitions Works in conjunction with Security Manager and Access Controller Knows where the class originated Understands signed Jar files Enforces namespace rules

23 Java Class Loaders Java applications can create and use different class loaders Java applets use the browser- provided class loader

24 Java Class Loaders Namespaces Used to eliminate ambiguity between classes with the same name Full name of a Java class is qualified by the name of the package: –java.lang.String – Default package

25 Java Class Loaders Namespaces Classes with different CODEBASEs are loaded by different instances of the class loader Even if fully qualified class names are the same, namespaces make them unique Namespaces enforce package protection

26 Java Class Loaders How they Work Previously loaded classes are cached Class loader optionally consults the Security Manager to see if the program is allowed to access the class Internal class loader attempts to load the class from CLASSPATH Class loader reads in an array of bytes Bytecode verification is performed

27 Java Class Loaders How they Work A class object is constructed from the bytecodes Resulting class name is verified to be the requested class name Base classes and classes referenced by static initializers are also loaded Other referenced classes are loaded when the class references them

28 Java Class Loaders How they Work An internal class loader (part of the JVM) loads the Java API classes when the VM starts up In 1.1 internal class loader also loads all CLASSPATH classes In 1.2 an instance of URLClassLoader loads classes from CLASSPATH Browsers load classes for the applets from the applet’s CODEBASE using URL class

29 Other Java Class Loaders An RMI class loader (RMIClassLoader) is similar to an applet class loader –Uses HTTP to load classes from a remote host Secure class loader associates protection domains with each class it loads – –Makes use of the access controller facilities URL class loader (URLClassLoader) - general purpose class loader

30 Java Class Loaders and JAR files Java Archive files, or JAR files are Zip files with some additional information JAR files contain many class files, and other files needed by an application All classes in a JAR files are loaded at once Signed classes must be in JAR files

31 Java Class Loaders Security Implications Class loaders are integral to Java’s security –Class loaders enforce namespace separation –Security Manager depends on the class loader to keep track of the class origin –Custom class loaders may be developed to handle load protocols other than HTTP, to implement class file encryption, and to implement special security policies.

32 Java Security Manager Security Manager is the sandbox guard Default security manager provided by browsers to protect local system resources Applications have a null security manager by default Use the -usepolicy option to utilize the default security manager (that in turn uses the Access Controller)

33 Java Security Manager Class File Bytecode VerificationClass LoaderSecurity Manager Instantiated Object Core Java API Access Controller

34 Java Security Manager java.lang.SecurityManager Programs perform operations through the core Java API Methods are invoked by the core Java API to check if an operation is allowable A SecurityException is thrown if the operation is not allowable

35 Java Security Manager Trusted Classes In general: –Core API classes are trusted –Classes that are loaded via the CLASSPATH are trusted Specific permissions may be granted based on signature and codebase Access Controller is called by the Security Manager to ascertain if a class is trust-worthy

36 Java Security Manager Methods Protection for the Java Virtual Machine System resource protection –File system access –Network access –Printing –Accessing the clipboard –Event queue access

37 Java Security Manager Methods Access to security related operations Protection against manipulating thread groups that were created by another entity

38 Access Controller Added in release 1.2 Used by the security manager to determine security policy Allows security policy to be configured without writing a custom security manager System security file: –$JAVAHOME/lib/security/ Security Manager still works with pre- version 1.2 classes

39 Access Controller System Security File $JAVAHOME/lib/security/ policy.expandProperties=true policy.allowSystemProperty=true policy.url.1=file:${java.home}/lib/security/java.policy policy.url.2=file:${user.home}/.java.policy These policy files map code sources to sets of permissions

40 Access Controller Roles Used by the security manager to determine access to resources May be used by a program to check application-specific permissions Used only if a security manager is being used

41 Access Controller Concepts Code sources - Where the class comes from Permissions - Ability to perform an operation Policies - Set of permissions by code source Protection domains - Permissions granted to classes from a particular code source

42 Access Controller Code Sources CodeSource(URL url, PublicKey[] key[]) public boolean equals(Object obj) public final URL getLocation() public final PublicKey[] getKeys()

43 Access Controller Permissions Permission properties: –Type (e.g. FilePermission) –Name (e.g. name of the file - supports wildcards) –Actions (e.g. read)

44 Access Controller Permissions Java API permissions –Access controller is automatically called if a security manager is active Arbitrary user-defined permissions –Name (e.g. CorporatePayroll) –Actions (e.g. read) –Access controller must be explicitly called

45 Access Controller Java API Permissions Java API permissions –FilePermission (e.g. /etc/passwd, read) –SocketPermission (IP:port, accept, connect, listen, resolve) –PropertyPermission (e.g. java.version, read) –RuntimePermission (Runtime class operations, e.g. exit) –AWTPermission - Access to windowing resources

46 Access Controller Java API Permissions Java API permissions –NetPermission - Multicast and HTTP authentication –SecurityPermission - Permission to use the security package –SerializablePermission - Object serialization –ReflectPermission - Reflection API –UnresolvedPermission - External permissions –AllPermission - Superuser

47 Security Policies Ties code sources to permissions Default policy is provided in the system security file Methods: Permissions evaluate(CodeSource cs) void refresh()

48 Default Security Policy Policy files specified by the system security file Policy files specified by the: policy.url.n entries General format: grant [signedBy ] [,codeBase ] { permission [ [, ]]; … permission [ [, ]]; };

49 Protection Domains public ProtectionDomain(CodeSource cs, Permissions p) public CodeSource getCodeSource() public Permissions getPermissions() public boolean implies(Permission p) Represents one “grant” entry in the file

50 Authentication It’s a wide open Internet System resources need to be protected from viruses and other attacks Need for authentication –Author authentication Where did the class come from –Data authentication Was the class content modified?

51 Authentication The signed JAR file is the mechanism Enables the class loader to know definitively where the class came from, and if it has been tampered with. Does NOT imply that Java should trust all signed JAR files Does NOT protect the privacy of the information in the JAR file - for that you need encryption

52 Encryption javax.crypto.Cipher - the encryption engine Perform encryption and decryption of arbitrary data Implements named algorithms Supplied by security providers Sun supports DES, multiple DES, and PBEWithMD5andDES

53 Encryption Used internally by class loader –Public and private keys –Message digests –Signed JAR files General purpose encryption

54 Encryption Signed JAR files Originator generates digital signature –Produce a message digest –Encrypt the digest with private key Recipient –Decrypt the signature using public key to reproduce the message digest –Match the decrypted and calculated digests

55 Encryption of Signed JAR files JAR file Message Digest Engine 451350228534... Digital Signature Engine Private 9728016828... Digital Signature Message Digest

56 Decryption of Signed JAR files Digital Signature Engine Public 9728016828... Digital Signature 451350228534... Message Digest JAR file Message Digest Engine

57 Java Security Summary Java Security Features –Java Language Security –Java Class Loaders –Security Manager and Access Controller –Security Policies –Authentication and Encryption Java Security is Both Configurable and Extendable

58 Java Security and Encryption Questions and Answers Dan Sedlacek CTO, Systems Management Group Sterling Software

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