1   /*
2    * Copyright (c) 2003, 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  
26  package sun.security.provider;
27  
28  import java.util.Arrays;
29  
30  /**
31   * Implementation for the MD2 algorithm, see RFC1319. It is very slow and
32   * not particular secure. It is only supported to be able to verify
33   * RSA/Verisign root certificates signed using MD2withRSA. It should not
34   * be used for anything else.
35   *
36   * @since   1.5
37   * @author  Andreas Sterbenz
38   */
39  public final class MD2 extends DigestBase {
40  
41      // state, 48 ints
42      private final int[] X;
43  
44      // checksum, 16 ints. they are really bytes, but byte arithmetic in
45      // the JVM is much slower that int arithmetic.
46      private final int[] C;
47  
48      // temporary store for checksum C during final digest
49      private final byte[] cBytes;
50  
51      /**
52       * Create a new MD2 digest. Called by the JCA framework
53       */
54      public MD2() {
55          super("MD2", 16, 16);
56          X = new int[48];
57          C = new int[16];
58          cBytes = new byte[16];
59      }
60  
61      private MD2(MD2 base) {
62          super(base);
63          this.X = base.X.clone();
64          this.C = base.C.clone();
65          cBytes = new byte[16];
66      }
67  
68      public Object clone() {
69          return new MD2(this);
70      }
71  
72      // reset state and checksum
73      void implReset() {
74          Arrays.fill(X, 0);
75          Arrays.fill(C, 0);
76      }
77  
78      // finish the digest
79      void implDigest(byte[] out, int ofs) {
80          int padValue = 16 - ((int)bytesProcessed & 15);
81          engineUpdate(PADDING[padValue], 0, padValue);
82          for (int i = 0; i < 16; i++) {
83              cBytes[i] = (byte)C[i];
84          }
85          implCompress(cBytes, 0);
86          for (int i = 0; i < 16; i++) {
87              out[ofs + i] = (byte)X[i];
88          }
89      }
90  
91      // one iteration of the compression function
92      void implCompress(byte[] b, int ofs) {
93          for (int i = 0; i < 16; i++) {
94              int k = b[ofs + i] & 0xff;
95              X[16 + i] = k;
96              X[32 + i] = k ^ X[i];
97          }
98  
99          // update the checksum
100         int t = C[15];
101         for (int i = 0; i < 16; i++) {
102             t = (C[i] ^= S[X[16 + i] ^ t]);
103         }
104 
105         t = 0;
106         for (int i = 0; i < 18; i++) {
107             for (int j = 0; j < 48; j++) {
108                 t = (X[j] ^= S[t]);
109             }
110             t = (t + i) & 0xff;
111         }
112     }
113 
114     // substitution table derived from Pi. Copied from the RFC.
115     private final static int[] S = new int[] {
116         41, 46, 67, 201, 162, 216, 124, 1, 61, 54, 84, 161, 236, 240, 6,
117         19, 98, 167, 5, 243, 192, 199, 115, 140, 152, 147, 43, 217, 188,
118         76, 130, 202, 30, 155, 87, 60, 253, 212, 224, 22, 103, 66, 111, 24,
119         138, 23, 229, 18, 190, 78, 196, 214, 218, 158, 222, 73, 160, 251,
120         245, 142, 187, 47, 238, 122, 169, 104, 121, 145, 21, 178, 7, 63,
121         148, 194, 16, 137, 11, 34, 95, 33, 128, 127, 93, 154, 90, 144, 50,
122         39, 53, 62, 204, 231, 191, 247, 151, 3, 255, 25, 48, 179, 72, 165,
123         181, 209, 215, 94, 146, 42, 172, 86, 170, 198, 79, 184, 56, 210,
124         150, 164, 125, 182, 118, 252, 107, 226, 156, 116, 4, 241, 69, 157,
125         112, 89, 100, 113, 135, 32, 134, 91, 207, 101, 230, 45, 168, 2, 27,
126         96, 37, 173, 174, 176, 185, 246, 28, 70, 97, 105, 52, 64, 126, 15,
127         85, 71, 163, 35, 221, 81, 175, 58, 195, 92, 249, 206, 186, 197,
128         234, 38, 44, 83, 13, 110, 133, 40, 132, 9, 211, 223, 205, 244, 65,
129         129, 77, 82, 106, 220, 55, 200, 108, 193, 171, 250, 36, 225, 123,
130         8, 12, 189, 177, 74, 120, 136, 149, 139, 227, 99, 232, 109, 233,
131         203, 213, 254, 59, 0, 29, 57, 242, 239, 183, 14, 102, 88, 208, 228,
132         166, 119, 114, 248, 235, 117, 75, 10, 49, 68, 80, 180, 143, 237,
133         31, 26, 219, 153, 141, 51, 159, 17, 131, 20,
134     };
135 
136     // digest padding. 17 element array.
137     // padding[0] is null
138     // padding[i] is an array of i time the byte value i (i = 1..16)
139     private final static byte[][] PADDING;
140 
141     static {
142         PADDING = new byte[17][];
143         for (int i = 1; i < 17; i++) {
144             byte[] b = new byte[i];
145             Arrays.fill(b, (byte)i);
146             PADDING[i] = b;
147         }
148     }
149 
150 }