Signing, Sealing, and Guarding JavaTM Objects

Li Gong and Roland Schemers

Javasoft, Sun Microsystems, Inc.

“In This Paper, We Describe a Few New Constructs for Signing, Sealing, and Guarding Java Objects. These Constructs Enrich the Existing Java Security APIs So That a Wide Range of Security-aware Application Can Be Significantly Easier to Build.”

Presented by Yongqiang Li

A Tutorial of Three Java Security Classes:

• java.security.SignedObject• java.security.GuardedObject• javax.crypto.SealedObject

Outline Introduction Signing Java Objects Sealing Java Objects Guarding Java Objects Conclusion Questions

Introduction Java language is widely used to build applications

– JDK: JVM, javac, APIs, simplicity “…the base platform provides a consistent security model that supports…”

– policy based– configurable– extensible– fine-grained access control

Protection provided by the underlying object orientation– Data encapsulation– Object name space partition– Type safety

Distributed Java application– “…protect the state of an object for integrity and confidentiality”

• Runtime system• Transit• Stored externally

Introduction 2 java.security.SignedObject java.security.GuardedObject Javax.crypto.SealedObject

} JDK1.2

- JCE1.2

Signing Java Objects 1 Protect object integrity A serializable object - original object SignedObject

– Signed Object• Deep copy of original• In serialized form

– Signature• Sign algorithm

– DSA(Digital Signature Algorithm) (NIST FIPS 186) – SHA-1(RFC 1321) message digest algorithm– MD5(NIST FIPS 180-1) message digest algorithm

– Immutable

signature

Original object SignedObject

What is the difference between object signing and code signing ?

Signing Java Objects 2 Potential applications of a SignObject

– as an unforgeable authorization token in any Java runtime

– “…transmitted across JVMs and authenticity an still be verified”

– “… to sign and serialize an object for storage outside the java runtime”

– “A series of nested SignedObject can be used to construct a logical sequence of signatures”

Signing Java Objects 3 API Design

– Class SignedObject• public SignedObject(Serializable object, PrivateKey signingKey, Signature signingEngine)

• public final void sign(PrivateKey signingKey, Signature signingEngine);

• public final Object getContent();• public final byte[] getSignature();• public final String getAlgorithm();• public final boolean verify(PublicKey verificationKey, Signature verificationEngine);

Examples– Signing

Signature signingEngine = Signature.getInstance(algorithm, provider);

SignedObject so = new SignedObject(myobject, privatekey, signingEngine);

Signing Java Objects 4

– VerifyingSignature verificationEngine = Signature.getInstance(algorithm, provider);

if(so.verify(publicKey, verificationEngine))try {

Object myobj = so.getContent();} catch (ClassNotFoundException e) {};

Signing Java Objects 5 Performance

Object size

(bytes)

Serialization

(ms)

512-bit SHA-1/DSA 1024-bit SHA-1/DSA

Signing

(ms)

Verification

(ms)

Signing

(ms)

Verification

(ms)

10 0 25 43 80 151

100 0 26 44 83 157

10K 1 134 153 189 260

100K 9 1119 1138 1168 1237

-JDK1.2beta , 166MHZ Sun Sparc Ultra-1 ,Solaris 2.5.1, 1000 rounds

Sealing Java Objects 1 Protect object confidentiality A serializable object A cryptographic algorithm

– A bulk(symmetric key) encryption algorithm -DES, IDEA, RC4

Encryption Decryption Deserialization

cipher text

Original object

SealedObject

Sealing Java Objects 2

cipher text

Original object

SignedObject andSealedObject

Using both SignedObject and SealedObject provides integrity and confidentiality– First create SignedObject

– Then create SealedObject

Signature

Why is blindly signing encrypted data sometimes dangerous?

Sealing Java Objects 3

– DecryptionCipher.init(Cipher.DECRYPT_MODE), desKey);

try {String s =

(String)so.getContent(cipher);

} catch (ClassNotFoundException e) {};

Examples– Encryption

KenGenerator keyGen = KeyGenerator.getInstance(“DES”);SecretKey desKey = keyGen.generateKey();Cipher cipher = Cipher.getInstance(“DES”);Cipher.init(Cipher.ENCRYPT_MODE, desKey);String s = new String(“Greeting”);SealedObject so = new SealedObject(s, cipher);

API design– Class SealedObject

• public SealedObject(Serializable object, Cipher c);• public final Object getContent(Cipher c);

Guarding Java Objects 1

IBM Compatible

IBM Compatible

IBM Compatible

IBM CompatibleRequest object

return object

return guardedObject

Request object

Check permissionReturn object

Check permission

Provider

Consumer

Consumer

Provider

•Don’t know what information needed by provider

•Don’t want a dialog for each request

•Information too security sensitive

•“… too much information to pass on”

Guarding Java Objects 2 What is the GuardedObject

– “A GuardedObject is an object that is used to protect access to another object”

requester

Protected object

GuardedObject

Guard object

1.Request access go.getObjedct()

2. Check guardg.checkGuard() 3. Return reference

Guarding Java Objects 3 Benefits of using GuardedObject

– “… access to a protected object is guaranteed to occur in a context where the protection mechanism would allow it”

– Simplify sever programs– Replace access control lists with object stores– “A guarded object class itself does not need to know its

own protection semantics”– “…encapsulate protection mechanisms for an object,

which can differ for its different method invocations, all inside a guard.”

Guarding Java Objects 4 API design

– Interface Guard• public abstract void checkGuard(Object object);

– Class GuardedObject• public GuardedObject(Object object, Guard guard);• public Object getObject();

Guarding Java Objects 5 Examples

– Encapulate an objects protection semeantics inside a guardFileInputStream fis = new FileInputStream(“/a/b/c”);

– Provider sidePublic abstract Permission implements Guard{

…Public void checkGuard{

AccessController.checkPermission(this);}

}FileInputStream fis = new FileInputStream(“/a/b/c”);FilePermission = new FilePermission(“/a/b/c”, “read”);GuardedObject g = new GuardedObject(fis,p);

– Consumer sideFileInputStream fis = (FileInputStream)g.getObject();

Conclusion “The constructs enrich the existing Java

security APIs so that security-aware application can be much easier to build.”

“The constructs are practical and usable in commercial products.”

Question?