Mozilla-JSS JCA Provider notes

The Mozilla-JSS JCA Provider

Newsgroup: mozilla.dev.tech.crypto

Overview

This document describes the JCA Provider shipped with JSS. The provider's name is "Mozilla-JSS". It implements cryptographic operations in native code using the NSS libraries.

Contents

• Signed JAR file
• Installing the Provider
• Specifying the CryptoToken
• Supported Classes
• What's Not Supported

Signed JAR file

JSS implements several JCE (Java Cryptography Extension) algorithms. These algorithms have at various times been export-controlled by the US government. JRE therefore requires that JAR files implementing JCE algorithms be digitally signed by an approved organization. The maintainers of JSS, Sun, Red Hat, and Mozilla, have this approval and signs the official builds of jss4.jar. At runtime, the JRE automatically verifies this signature whenever a JSS class is loaded that implements a JCE algorithm. The verification is transparent to the application (unless it fails and throws an exception). If you are curious, you can verify the signature on the JAR file using the jarsigner tool, which is distributed with the JDK.

If you build JSS yourself from source instead of using binaries downloaded from mozilla.org, your JAR file will not have a valid signature. This means you will not be able to use the JSS provider for JCE algorithms. You have two choices.

1. Use the binary release of JSS from mozilla.org.
2. Apply for your own JCE code-signing certificate following the procedure at How to Implement a Provider for the Java^TM Cryptography Extension. Then you can sign your own JSS JAR file.

Installing the Provider

In order to use any part of JSS, including the JCA provider, you must first call CryptoManager.initialize(). By default, the JCA provider will be installed in the list of providers maintained by the java.security.Security class. If you do not wish the provider to be installed, create a CryptoManager.InitializationValues object, set its installJSSProvider field to false, and pass the InitializationValues object to CryptoManager.initialize().

Specifying the CryptoToken

All cryptographic operations in JSS and NSS occur on a particular PKCS #11 token, implemented in software or hardware. There is no clean way to specify this token through the JCA API. By default, the JSS provider carries out all operations except MessageDigest on the Internal Key Storage Token, a software token included in JSS/NSS. MessageDigest operations take place by default on the Internal Crypto Token, another internal software token in JSS/NSS. There is no good design reason for this difference, but it is necessitated by a quirk in the NSS implementation.

In order to use a different token, use CryptoManager.setThreadToken(). This sets the token to be used by the JSS JCA provider in the current thread. When you call getInstance() on a JCA class, the JSS provider checks the current per-thread default token (by calling CryptoManager.getThreadToken()) and instructs the new object to use that token for cryptographic operations. The per-thread default token setting is only consulted inside getInstance(). Once a JCA object has been created it will continue to use the same token, even if the application later changes the per-thread default token.

Whenever a new thread is created, its token is initialized to the default, the Internal Key Storage Token. Thus, the thread token is not inherited from the parent thread.

The following example shows how you can specify which token is used for various JCA operations:

// Lookup PKCS #11 tokens
CryptoManager manager = CryptoManager.getInstance();
CryptoToken tokenA = manager.getTokenByName("TokenA");
CryptoToken tokenB = manager.getTokenByName("TokenB");

// Create an RSA KeyPairGenerator using TokenA
manager.setThreadToken(tokenA);
KeyPairGenerator rsaKpg = KeyPairGenerator.getInstance("Mozilla-JSS", "RSA");

// Create a DSA KeyPairGenerator using TokenB
manager.setThreadToken(tokenB);
KeyPairGenerator dsaKpg  = KeyPairGenerator.getInstance("Mozilla-JSS", "DSA");

// Generate an RSA KeyPair. This will happen on TokenA because TokenA
// was the per-thread default token when rsaKpg was created.
rsaKpg.initialize(1024);
KeyPair rsaPair = rsaKpg.generateKeyPair();

// Generate a DSA KeyPair. This will happen on TokenB because TokenB
// was the per-thread default token when dsaKpg was created.
dsaKpg.initialize(1024);
KeyPair dsaPair = dsaKpg.generateKeyPair();

Supported Classes

• Cipher
• DSAPrivateKey
• DSAPublicKey
• KeyFactory
• KeyGenerator
• KeyPairGenerator
• Mac
• MessageDigest
• RSAPrivateKey
• RSAPublicKey
• SecretKeyFactory
• SecretKey
• SecureRandom
• Signature

Cipher

Supported Algorithms

Notes

• AES
• DES
• DESede (DES3)
• RC2
• RC4
• RSA
  • The following modes and padding schemes are supported:

    Algorithm	Mode	Padding
    DES	ECB	NoPadding
    	CBC	NoPadding
    		PKCS5 Padding
    DESede DES3	ECB	NoPadding
    	CBC	NoPadding
    		PKCS5 Padding
    AES	ECB	NoPadding
    	CBC	NoPadding
    		PKCS5 Padding
    RC4	None	None
    RC2	CBC	NoPadding
    		PKCS5Padding

  • The SecureRandom argument passed to initSign() and initVerify() is ignored, because NSS does not support specifying an external source of randomness.

DSAPrivateKey

• getX() is not supported because NSS does not support extracting data from private keys.

KeyFactory

Supported Algorithms

Notes

• DSA
• RSA
• The following transformations are supported for generatePublic() and generatePrivate():

  From	To
  RSAPublicKeySpec	RSAPublicKey
  DSAPublicKeySpec	DSAPublicKey
  X509EncodedKeySpec	RSAPublicKey DSAPublicKey
  RSAPrivateCrtKeySpec	RSAPrivateKey
  DSAPrivateKeySpec	DSAPrivateKey
  PKCS8EncodedKeySpec	RSAPrivateKey DSAPrivateKey

• getKeySpec() is not supported. This method exports key material in plaintext and is therefore insecure. Note that a public key's data can be accessed directly from the key.
• translateKey() simply gets the encoded form of the given key and then tries to import it by calling generatePublic() or generatePrivate(). Only X509EncodedKeySpec is supported for public keys, and only PKCS8EncodedKeySpec is supported for private keys.

KeyGenerator

Supported Algorithms

Notes

• AES
• DES
• DESede (DES3)
• RC4
• The SecureRandom argument passed to init() is ignored, because NSS does not support specifying an external source of randomness.
• None of the key generation algorithms accepts an AlgorithmParameterSpec.

KeyPairGenerator

Supported Algorithms

Notes

• DSA
• RSA

• The SecureRandom argument passed to initialize() is ignored, because NSS does not support specifying an external source of randomness.

Mac

Supported Algorithms

Notes

• HmacSHA1 (Hmac-SHA1)

• Any secret key type (AES, DES, etc.) can be used as the MAC key, but it must be a JSS key. That is, it must be an instanceof org.mozilla.jss.crypto.SecretKeyFacade.
• The params passed to init() are ignored.

MessageDigest

Supported Algorithms

• MD5
• MD2
• SHA-1 (SHA1, SHA)

RSAPrivateKey

Notes

• getModulus() is not supported because NSS does not support extracting data from private keys.
• getPrivateExponent() is not supported because NSS does not support extracting data from private keys.

SecretKeyFactory

Supported Algorithms

Notes

• AES
• DES
• DESede (DES3)
• PBAHmacSHA1
• PBEWithMD5AndDES
• PBEWithSHA1AndDES
• PBEWithSHA1AndDESede (PBEWithSHA1AndDES3)
• PBEWithSHA1And128RC4
• RC4

• generateSecret supports the following transformations:

  KeySpec Class	Key Algorithm
  PBEKeySpec org.mozilla.jss.crypto.PBEKeyGenParams	Using the appropriate PBE algorithm: DES DESede RC4
  DESedeKeySpec	DESede
  DESKeySpec	DES
  SecretKeySpec	AES DES DESede RC4

• getKeySpec supports the following transformations:

  Key Algorithm	KeySpec Class
  DESede	DESedeKeySpec
  DES	DESKeySpec
  DESede DES AES RC4	SecretKeySpec

• For increased security, some SecretKeys may not be extractable from their PKCS #11 token. In this case, the key should be wrapped (encrypted with another key), and then the encrypted key might be extractable from the token. This policy varies across PKCS #11 tokens.
• translateKey tries two approaches to copying keys. First, it tries to copy the key material directly using NSS calls to PKCS #11. If that fails, it calls getEncoded() on the source key, and then tries to create a new key on the target token from the encoded bits. Both of these operations will fail if the source key is not extractable.
• The class java.security.spec.PBEKeySpec in JDK versions earlier than 1.4 does not contain the salt and iteration fields, which are necessary for PBE key generation. These fields were added in JDK 1.4. If you are using a JDK (or JRE) version earlier than 1.4, you cannot use class java.security.spec.PBEKeySpec. Instead, you can use org.mozilla.jss.crypto.PBEKeyGenParams. If you are using JDK (or JRE) 1.4 or later, you can use java.security.spec.PBEKeySpec or org.mozilla.jss.crypto.PBEKeyGenParams.

SecretKey

Supported Algorithms

Notes

• AES
• DES
• DESede (DES3)
• HmacSHA1
• RC2
• RC4

• SecretKey is implemented by the class org.mozilla.jss.crypto.SecretKeyFacade, which acts as a wrapper around the JSS class SymmetricKey. Any SecretKeys handled by JSS will actually be SecretKeyFacades. This should usually be transparent.

SecureRandom

Supported Algorithms

Notes

• pkcs11prng

• This invokes the NSS internal pseudorandom number generator.

Signature

Supported Algorithms

Notes

• SHA1withDSA (DSA, DSS, SHA/DSA, SHA-1/DSA, SHA1/DSA, DSAWithSHA1, SHAwithDSA)
• SHA-1/RSA (SHA1/RSA, SHA1withRSA)
• MD5/RSA (MD5withRSA)
• MD2/RSA

• The SecureRandom argument passed to initSign() and initVerify() is ignored, because NSS does not support specifying an external source of randomness.

What's Not Supported

The following classes don't work very well:

• KeyStore: There are many serious problems mapping the JCA keystore interface onto NSS's model of PKCS #11 modules. The current implementation is almost useless. Since these problems lie deep in the NSS design and implementation, there is no clear timeframe for fixing them. Meanwhile, the org.mozilla.jss.crypto.CryptoStore class can be used for some of this functionality.