/* * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ 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() {        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;    } }