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package com.sun.crypto.provider;
import java.security.*;
import java.security.spec.AlgorithmParameterSpec;
import javax.crypto.*;
/**
* Implementation of the ARCFOUR cipher, an algorithm apparently compatible
* with RSA Security's RC4(tm) cipher. The description of this algorithm was
* taken from Bruce Schneier's book Applied Cryptography, 2nd ed.,
* section 17.1.
*
* We support keys from 40 to 1024 bits. ARCFOUR would allow for keys shorter
* than 40 bits, but that is too insecure for us to permit.
*
* Note that we subclass CipherSpi directly and do not use the CipherCore
* framework. That was designed to simplify implementation of block ciphers
* and does not offer any advantages for stream ciphers such as ARCFOUR.
*
* @since 1.5
* @author Andreas Sterbenz
*/
public final class ARCFOURCipher extends CipherSpi {
// state array S, 256 entries. The entries are 8-bit, but we use an int[]
// because int arithmetic is much faster than in Java than bytes.
private final int[] S;
// state indices i and j. Called is and js to avoid collision with
// local variables. 'is' is set to -1 after a call to doFinal()
private int is, js;
// the bytes of the last key used (if any)
// we need this to re-initialize after a call to doFinal()
private byte[] lastKey;
// called by the JCE framework
public ARCFOURCipher() {
SunJCE.ensureIntegrity(getClass());
S = new int[256];
}
// core key setup code. initializes S, is, and js
// assumes key is non-null and between 40 and 1024 bit
private void init(byte[] key) {
// initialize S[i] to i
for (int i = 0; i < 256; i++) {
S[i] = i;
}
// we avoid expanding key to 256 bytes and instead keep a separate
// counter ki = i mod key.length.
for (int i = 0, j = 0, ki = 0; i < 256; i++) {
int Si = S[i];
j = (j + Si + key[ki]) & 0xff;
S[i] = S[j];
S[j] = Si;
ki++;
if (ki == key.length) {
ki = 0;
}
}
// set indices to 0
is = 0;
js = 0;
}
// core crypt code. OFB style, so works for both encryption and decryption
private void crypt(byte[] in, int inOfs, int inLen, byte[] out, int outOfs) {
if (is < 0) {
// doFinal() was called, need to reset the cipher to initial state
init(lastKey);
}
while (inLen-- > 0) {
is = (is + 1) & 0xff;
int Si = S[is];
js = (js + Si) & 0xff;
int Sj = S[js];
S[is] = Sj;
S[js] = Si;
out[outOfs++] = (byte)(in[inOfs++] ^ S[(Si + Sj) & 0xff]);
}
}
// Modes do not make sense with stream ciphers, but allow ECB
// see JCE spec.
protected void engineSetMode(String mode) throws NoSuchAlgorithmException {
if (mode.equalsIgnoreCase("ECB") == false) {
throw new NoSuchAlgorithmException("Unsupported mode " + mode);
}
}
// Padding does not make sense with stream ciphers, but allow NoPadding
// see JCE spec.
protected void engineSetPadding(String padding)
throws NoSuchPaddingException {
if (padding.equalsIgnoreCase("NoPadding") == false) {
throw new NoSuchPaddingException("Padding must be NoPadding");
}
}
// Return 0 to indicate stream cipher
// see JCE spec.
protected int engineGetBlockSize() {
return 0;
}
// output length is always the same as input length
// see JCE spec
protected int engineGetOutputSize(int inputLen) {
return inputLen;
}
// no IV, return null
// see JCE spec
protected byte[] engineGetIV() {
return null;
}
// no parameters
// see JCE spec
protected AlgorithmParameters engineGetParameters() {
return null;
}
// see JCE spec
protected void engineInit(int opmode, Key key, SecureRandom random)
throws InvalidKeyException {
init(opmode, key);
}
// see JCE spec
protected void engineInit(int opmode, Key key,
AlgorithmParameterSpec params, SecureRandom random)
throws InvalidKeyException, InvalidAlgorithmParameterException {
if (params != null) {
throw new InvalidAlgorithmParameterException
("Parameters not supported");
}
init(opmode, key);
}
// see JCE spec
protected void engineInit(int opmode, Key key,
AlgorithmParameters params, SecureRandom random)
throws InvalidKeyException, InvalidAlgorithmParameterException {
if (params != null) {
throw new InvalidAlgorithmParameterException
("Parameters not supported");
}
init(opmode, key);
}
// init method. Check opmode and key, then call init(byte[]).
private void init(int opmode, Key key) throws InvalidKeyException {
if ((opmode < Cipher.ENCRYPT_MODE) || (opmode > Cipher.UNWRAP_MODE)) {
throw new InvalidKeyException("Unknown opmode: " + opmode);
}
lastKey = getEncodedKey(key);
init(lastKey);
}
// return the encoding of key if key is a valid ARCFOUR key.
// otherwise, throw an InvalidKeyException
private static byte[] getEncodedKey(Key key) throws InvalidKeyException {
String keyAlg = key.getAlgorithm();
if (!keyAlg.equals("RC4") && !keyAlg.equals("ARCFOUR")) {
throw new InvalidKeyException("Not an ARCFOUR key: " + keyAlg);
}
if ("RAW".equals(key.getFormat()) == false) {
throw new InvalidKeyException("Key encoding format must be RAW");
}
byte[] encodedKey = key.getEncoded();
if ((encodedKey.length < 5) || (encodedKey.length > 128)) {
throw new InvalidKeyException
("Key length must be between 40 and 1024 bit");
}
return encodedKey;
}
// see JCE spec
protected byte[] engineUpdate(byte[] in, int inOfs, int inLen) {
byte[] out = new byte[inLen];
crypt(in, inOfs, inLen, out, 0);
return out;
}
// see JCE spec
protected int engineUpdate(byte[] in, int inOfs, int inLen,
byte[] out, int outOfs) throws ShortBufferException {
if (out.length - outOfs < inLen) {
throw new ShortBufferException("Output buffer too small");
}
crypt(in, inOfs, inLen, out, outOfs);
return inLen;
}
// see JCE spec
protected byte[] engineDoFinal(byte[] in, int inOfs, int inLen) {
byte[] out = engineUpdate(in, inOfs, inLen);
is = -1;
return out;
}
// see JCE spec
protected int engineDoFinal(byte[] in, int inOfs, int inLen,
byte[] out, int outOfs) throws ShortBufferException {
int outLen = engineUpdate(in, inOfs, inLen, out, outOfs);
is = -1;
return outLen;
}
// see JCE spec
protected byte[] engineWrap(Key key) throws IllegalBlockSizeException,
InvalidKeyException {
byte[] encoded = key.getEncoded();
if ((encoded == null) || (encoded.length == 0)) {
throw new InvalidKeyException("Could not obtain encoded key");
}
return engineDoFinal(encoded, 0, encoded.length);
}
// see JCE spec
protected Key engineUnwrap(byte[] wrappedKey, String algorithm,
int type) throws InvalidKeyException, NoSuchAlgorithmException {
byte[] encoded = engineDoFinal(wrappedKey, 0, wrappedKey.length);
return ConstructKeys.constructKey(encoded, algorithm, type);
}
// see JCE spec
protected int engineGetKeySize(Key key) throws InvalidKeyException {
byte[] encodedKey = getEncodedKey(key);
return encodedKey.length << 3;
}
}