1/*
2 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package com.sun.crypto.provider;
27
28import java.security.*;
29import java.security.spec.AlgorithmParameterSpec;
30
31import javax.crypto.*;
32
33/**
34 * Implementation of the ARCFOUR cipher, an algorithm apparently compatible
35 * with RSA Security's RC4(tm) cipher. The description of this algorithm was
36 * taken from Bruce Schneier's book Applied Cryptography, 2nd ed.,
37 * section 17.1.
38 *
39 * We support keys from 40 to 1024 bits. ARCFOUR would allow for keys shorter
40 * than 40 bits, but that is too insecure for us to permit.
41 *
42 * Note that we subclass CipherSpi directly and do not use the CipherCore
43 * framework. That was designed to simplify implementation of block ciphers
44 * and does not offer any advantages for stream ciphers such as ARCFOUR.
45 *
46 * @since   1.5
47 * @author  Andreas Sterbenz
48 */
49public final class ARCFOURCipher extends CipherSpi {
50
51    // state array S, 256 entries. The entries are 8-bit, but we use an int[]
52    // because int arithmetic is much faster than in Java than bytes.
53    private final int[] S;
54
55    // state indices i and j. Called is and js to avoid collision with
56    // local variables. 'is' is set to -1 after a call to doFinal()
57    private int is, js;
58
59    // the bytes of the last key used (if any)
60    // we need this to re-initialize after a call to doFinal()
61    private byte[] lastKey;
62
63    // called by the JCE framework
64    public ARCFOURCipher() {
65        S = new int[256];
66    }
67
68    // core key setup code. initializes S, is, and js
69    // assumes key is non-null and between 40 and 1024 bit
70    private void init(byte[] key) {
71        // initialize S[i] to i
72        for (int i = 0; i < 256; i++) {
73            S[i] = i;
74        }
75
76        // we avoid expanding key to 256 bytes and instead keep a separate
77        // counter ki = i mod key.length.
78        for (int i = 0, j = 0, ki = 0; i < 256; i++) {
79            int Si = S[i];
80            j = (j + Si + key[ki]) & 0xff;
81            S[i] = S[j];
82            S[j] = Si;
83            ki++;
84            if (ki == key.length) {
85                ki = 0;
86            }
87        }
88
89        // set indices to 0
90        is = 0;
91        js = 0;
92    }
93
94    // core crypt code. OFB style, so works for both encryption and decryption
95    private void crypt(byte[] in, int inOfs, int inLen, byte[] out,
96            int outOfs) {
97        if (is < 0) {
98            // doFinal() was called, need to reset the cipher to initial state
99            init(lastKey);
100        }
101        while (inLen-- > 0) {
102            is = (is + 1) & 0xff;
103            int Si = S[is];
104            js = (js + Si) & 0xff;
105            int Sj = S[js];
106            S[is] = Sj;
107            S[js] = Si;
108            out[outOfs++] = (byte)(in[inOfs++] ^ S[(Si + Sj) & 0xff]);
109        }
110    }
111
112    // Modes do not make sense with stream ciphers, but allow ECB
113    // see JCE spec.
114    protected void engineSetMode(String mode) throws NoSuchAlgorithmException {
115        if (mode.equalsIgnoreCase("ECB") == false) {
116            throw new NoSuchAlgorithmException("Unsupported mode " + mode);
117        }
118    }
119
120    // Padding does not make sense with stream ciphers, but allow NoPadding
121    // see JCE spec.
122    protected void engineSetPadding(String padding)
123            throws NoSuchPaddingException {
124        if (padding.equalsIgnoreCase("NoPadding") == false) {
125            throw new NoSuchPaddingException("Padding must be NoPadding");
126        }
127    }
128
129    // Return 0 to indicate stream cipher
130    // see JCE spec.
131    protected int engineGetBlockSize() {
132        return 0;
133    }
134
135    // output length is always the same as input length
136    // see JCE spec
137    protected int engineGetOutputSize(int inputLen) {
138        return inputLen;
139    }
140
141    // no IV, return null
142    // see JCE spec
143    protected byte[] engineGetIV() {
144        return null;
145    }
146
147    // no parameters
148    // see JCE spec
149    protected AlgorithmParameters engineGetParameters() {
150        return null;
151    }
152
153    // see JCE spec
154    protected void engineInit(int opmode, Key key, SecureRandom random)
155            throws InvalidKeyException {
156        init(opmode, key);
157    }
158
159    // see JCE spec
160    protected void engineInit(int opmode, Key key,
161            AlgorithmParameterSpec params, SecureRandom random)
162            throws InvalidKeyException, InvalidAlgorithmParameterException {
163        if (params != null) {
164            throw new InvalidAlgorithmParameterException
165                ("Parameters not supported");
166        }
167        init(opmode, key);
168    }
169
170    // see JCE spec
171    protected void engineInit(int opmode, Key key,
172            AlgorithmParameters params, SecureRandom random)
173            throws InvalidKeyException, InvalidAlgorithmParameterException {
174        if (params != null) {
175            throw new InvalidAlgorithmParameterException
176                ("Parameters not supported");
177        }
178        init(opmode, key);
179    }
180
181    // init method. Check opmode and key, then call init(byte[]).
182    private void init(int opmode, Key key) throws InvalidKeyException {
183        if ((opmode < Cipher.ENCRYPT_MODE) || (opmode > Cipher.UNWRAP_MODE)) {
184            throw new InvalidKeyException("Unknown opmode: " + opmode);
185        }
186        lastKey = getEncodedKey(key);
187        init(lastKey);
188    }
189
190    // return the encoding of key if key is a valid ARCFOUR key.
191    // otherwise, throw an InvalidKeyException
192    private static byte[] getEncodedKey(Key key) throws InvalidKeyException {
193        String keyAlg = key.getAlgorithm();
194        if (!keyAlg.equals("RC4") && !keyAlg.equals("ARCFOUR")) {
195            throw new InvalidKeyException("Not an ARCFOUR key: " + keyAlg);
196        }
197        if ("RAW".equals(key.getFormat()) == false) {
198            throw new InvalidKeyException("Key encoding format must be RAW");
199        }
200        byte[] encodedKey = key.getEncoded();
201        if ((encodedKey.length < 5) || (encodedKey.length > 128)) {
202            throw new InvalidKeyException
203                ("Key length must be between 40 and 1024 bit");
204        }
205        return encodedKey;
206    }
207
208    // see JCE spec
209    protected byte[] engineUpdate(byte[] in, int inOfs, int inLen) {
210        byte[] out = new byte[inLen];
211        crypt(in, inOfs, inLen, out, 0);
212        return out;
213    }
214
215    // see JCE spec
216    protected int engineUpdate(byte[] in, int inOfs, int inLen,
217            byte[] out, int outOfs) throws ShortBufferException {
218        if (out.length - outOfs < inLen) {
219            throw new ShortBufferException("Output buffer too small");
220        }
221        crypt(in, inOfs, inLen, out, outOfs);
222        return inLen;
223    }
224
225    // see JCE spec
226    protected byte[] engineDoFinal(byte[] in, int inOfs, int inLen) {
227        byte[] out = engineUpdate(in, inOfs, inLen);
228        is = -1;
229        return out;
230    }
231
232    // see JCE spec
233    protected int engineDoFinal(byte[] in, int inOfs, int inLen,
234            byte[] out, int outOfs) throws ShortBufferException {
235        int outLen = engineUpdate(in, inOfs, inLen, out, outOfs);
236        is = -1;
237        return outLen;
238    }
239
240    // see JCE spec
241    protected byte[] engineWrap(Key key) throws IllegalBlockSizeException,
242            InvalidKeyException {
243        byte[] encoded = key.getEncoded();
244        if ((encoded == null) || (encoded.length == 0)) {
245            throw new InvalidKeyException("Could not obtain encoded key");
246        }
247        return engineDoFinal(encoded, 0, encoded.length);
248    }
249
250    // see JCE spec
251    protected Key engineUnwrap(byte[] wrappedKey, String algorithm,
252            int type) throws InvalidKeyException, NoSuchAlgorithmException {
253        byte[] encoded = engineDoFinal(wrappedKey, 0, wrappedKey.length);
254        return ConstructKeys.constructKey(encoded, algorithm, type);
255    }
256
257    // see JCE spec
258    protected int engineGetKeySize(Key key) throws InvalidKeyException {
259        byte[] encodedKey = getEncodedKey(key);
260        return encodedKey.length << 3;
261    }
262
263}
264