/*
* Copyright 2003-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.apache.ws.security.conversation.dkalgo;
/**
*
<pre>
P_SHA-1 DEFINITION
==================
<b>P_SHA-1(secret, seed)</b> =
HMAC_SHA-1(secret, A(1) + seed) +
HMAC_SHA-1(secret, A(2) + seed) +
HMAC_SHA-1(secret, A(3) + seed) + ...
<i>Where + indicates concatenation.</i>
<br>
A() is defined as:
A(0) = seed
A(i) = HMAC_SHA-1(secret, A(i-1))
<br>
<i>Source : RFC 2246 - The TLS Protocol Version 1.0
Section 5. HMAC and the pseudorandom function</i>
</pre>
*
* @author Ruchith Fernando
*/
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import org.apache.ws.security.conversation.ConversationException;
public class P_SHA1
implements DerivationAlgorithm {
public byte[] createKey(byte[] secret, byte[] seed, int offset,
long length) throws ConversationException {
try {
Mac mac = Mac.getInstance("HmacSHA1");
byte[] tempBytes = P_hash(secret, seed, mac,
(offset + (int) length));
byte[] key = new byte[(int) length];
for (int i = 0; i < key.length; i++)
key[i] = tempBytes[i + offset];
return key;
} catch (Exception ex) {
throw new ConversationException("Key Derivation : P_SHA-1: "
+ ex.getMessage());
}
}
/**
* From WSUsernameToken :-)
*
* @param secret
* @param seed
* @param mac
* @param required
* @return
* @throws java.lang.Exception
*/
private static byte[] P_hash(byte[] secret, byte[] seed, Mac mac,
int required) throws Exception {
byte[] out = new byte[required];
int offset = 0, tocpy;
byte[] A, tmp;
A = seed;
while (required > 0) {
SecretKeySpec key = new SecretKeySpec(secret, "HMACSHA1");
mac.init(key);
mac.update(A);
A = mac.doFinal();
mac.reset();
mac.init(key);
mac.update(A);
mac.update(seed);
tmp = mac.doFinal();
tocpy = min(required, tmp.length);
System.arraycopy(tmp, 0, out, offset, tocpy);
offset += tocpy;
required -= tocpy;
}
return out;
}
private static int min(int a, int b) {
return (a > b) ? b : a;
}
}