libjava/classpath/gnu/javax/net/ssl/provider/TLSHMac.java

   1 /* TLSHMac.java -- HMAC used in TLS.
   2    Copyright (C) 2001, 2002, 2003, 2006  Free Software Foundation, Inc.
   3
   4 This file is a part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or (at
   9 your option) any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19 USA
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version.  */
  37
  38
  39 package gnu.javax.net.ssl.provider;
  40
  41 import java.security.InvalidKeyException;
  42 import java.util.Map;
  43
  44 import gnu.java.security.hash.IMessageDigest;
  45 import gnu.javax.crypto.mac.HMac;
  46
  47 /**
  48  * The operation of this HMac is identical to normal HMacs, but this one
  49  * allows keys with short lengths (including zero).
  50  */
  51 class TLSHMac extends HMac
  52 {
  53
  54   // Constants.
  55   // -------------------------------------------------------------------------
  56
  57   private static final byte IPAD_BYTE = 0x36;
  58   private static final byte OPAD_BYTE = 0x5C;
  59
  60   // Constructor.
  61   // -------------------------------------------------------------------------
  62
  63   TLSHMac(IMessageDigest hash)
  64   {
  65     super(hash);
  66   }
  67
  68   // Instance methods.
  69   // -------------------------------------------------------------------------
  70
  71   public void init(Map attributes)
  72     throws InvalidKeyException, IllegalStateException
  73   {
  74     Integer ts = (Integer) attributes.get(TRUNCATED_SIZE);
  75     truncatedSize = (ts == null ? macSize : ts.intValue());
  76     if (truncatedSize < (macSize / 2)) {
  77       throw new IllegalArgumentException("Truncated size too small");
  78     } else if (truncatedSize < 10) {
  79       throw new IllegalArgumentException("Truncated size less than 80 bits");
  80     }
  81
  82     // we dont use/save the key outside this method
  83     byte[] K = (byte[]) attributes.get(MAC_KEY_MATERIAL);
  84     if (K == null) { // take it as an indication to re-use previous key if set
  85       if (ipadHash == null)
  86         {
  87           throw new InvalidKeyException("Null key");
  88         }
  89       // we already went through the motions; ie. up to step #4.  re-use
  90       underlyingHash = (IMessageDigest) ipadHash.clone();
  91       return;
  92     }
  93
  94     if (K.length > blockSize)
  95       {
  96         // (0) replace K with HASH(K) if K is larger than the hash's
  97         //     block size. Then pad with zeros until it is the correct
  98         //     size (the next `if').
  99         underlyingHash.update(K, 0, K.length);
 100         K = underlyingHash.digest();
 101       }
 102     if (K.length < blockSize)
 103       {
 104         // (1) append zeros to the end of K to create a B byte string
 105         //     (e.g., if K is of length 20 bytes and B=64, then K will be
 106         //     appended with 44 zero bytes 0x00)
 107         int limit = (K.length > blockSize) ? blockSize : K.length;
 108         byte[] newK = new byte[blockSize];
 109         System.arraycopy(K, 0, newK, 0, limit);
 110         K = newK;
 111       }
 112
 113     underlyingHash.reset();
 114     opadHash = (IMessageDigest) underlyingHash.clone();
 115     if (ipad == null)
 116       {
 117         ipad = new byte[blockSize];
 118       }
 119     // (2) XOR (bitwise exclusive-OR) the B byte string computed in step
 120     //     (1) with ipad
 121     // (3) append the stream of data 'text' to the B byte string resulting
 122     //     from step (2)
 123     // (4) apply H to the stream generated in step (3)
 124     for (int i = 0; i < blockSize; i++)
 125       {
 126         ipad[i] = (byte)(K[i] ^ IPAD_BYTE);
 127       }
 128     for (int i = 0; i < blockSize; i++)
 129       {
 130         opadHash.update((byte)(K[i] ^ OPAD_BYTE));
 131       }
 132
 133     underlyingHash.update(ipad, 0, blockSize);
 134     ipadHash = (IMessageDigest) underlyingHash.clone();
 135     K = null;
 136   }
 137 }