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package com.sun.crypto.provider;

import java.util.Arrays;

import java.nio.ByteBuffer;

import javax.crypto.MacSpi;
import javax.crypto.SecretKey;
import java.security.*;
import java.security.spec.*;

This class constitutes the core of HMAC- algorithms, where can be SHA1 or MD5, etc. See RFC 2104 for spec. It also contains the implementation classes for SHA-224, SHA-256, SHA-384, and SHA-512 HMACs.
Author:Jan Luehe
/** * This class constitutes the core of HMAC-<MD> algorithms, where * <MD> can be SHA1 or MD5, etc. See RFC 2104 for spec. * * It also contains the implementation classes for SHA-224, SHA-256, * SHA-384, and SHA-512 HMACs. * * @author Jan Luehe */
abstract class HmacCore extends MacSpi implements Cloneable { private MessageDigest md; private byte[] k_ipad; // inner padding - key XORd with ipad private byte[] k_opad; // outer padding - key XORd with opad private boolean first; // Is this the first data to be processed? private final int blockLen;
Standard constructor, creates a new HmacCore instance using the specified MessageDigest object.
/** * Standard constructor, creates a new HmacCore instance using the * specified MessageDigest object. */
HmacCore(MessageDigest md, int bl) { this.md = md; this.blockLen = bl; this.k_ipad = new byte[blockLen]; this.k_opad = new byte[blockLen]; first = true; }
Standard constructor, creates a new HmacCore instance instantiating a MessageDigest of the specified name.
/** * Standard constructor, creates a new HmacCore instance instantiating * a MessageDigest of the specified name. */
HmacCore(String digestAlgorithm, int bl) throws NoSuchAlgorithmException { this(MessageDigest.getInstance(digestAlgorithm), bl); }
Returns the length of the HMAC in bytes.
Returns:the HMAC length in bytes.
/** * Returns the length of the HMAC in bytes. * * @return the HMAC length in bytes. */
protected int engineGetMacLength() { return this.md.getDigestLength(); }
Initializes the HMAC with the given secret key and algorithm parameters.
Params:
  • key – the secret key.
  • params – the algorithm parameters.
Throws:
/** * Initializes the HMAC with the given secret key and algorithm parameters. * * @param key the secret key. * @param params the algorithm parameters. * * @exception InvalidKeyException if the given key is inappropriate for * initializing this MAC. * @exception InvalidAlgorithmParameterException if the given algorithm * parameters are inappropriate for this MAC. */
protected void engineInit(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException { if (params != null) { throw new InvalidAlgorithmParameterException ("HMAC does not use parameters"); } if (!(key instanceof SecretKey)) { throw new InvalidKeyException("Secret key expected"); } byte[] secret = key.getEncoded(); if (secret == null) { throw new InvalidKeyException("Missing key data"); } // if key is longer than the block length, reset it using // the message digest object. if (secret.length > blockLen) { byte[] tmp = md.digest(secret); // now erase the secret Arrays.fill(secret, (byte)0); secret = tmp; } // XOR k with ipad and opad, respectively for (int i = 0; i < blockLen; i++) { int si = (i < secret.length) ? secret[i] : 0; k_ipad[i] = (byte)(si ^ 0x36); k_opad[i] = (byte)(si ^ 0x5c); } // now erase the secret Arrays.fill(secret, (byte)0); secret = null; engineReset(); }
Processes the given byte.
Params:
  • input – the input byte to be processed.
/** * Processes the given byte. * * @param input the input byte to be processed. */
protected void engineUpdate(byte input) { if (first == true) { // compute digest for 1st pass; start with inner pad md.update(k_ipad); first = false; } // add the passed byte to the inner digest md.update(input); }
Processes the first len bytes in input, starting at offset.
Params:
  • input – the input buffer.
  • offset – the offset in input where the input starts.
  • len – the number of bytes to process.
/** * Processes the first <code>len</code> bytes in <code>input</code>, * starting at <code>offset</code>. * * @param input the input buffer. * @param offset the offset in <code>input</code> where the input starts. * @param len the number of bytes to process. */
protected void engineUpdate(byte input[], int offset, int len) { if (first == true) { // compute digest for 1st pass; start with inner pad md.update(k_ipad); first = false; } // add the selected part of an array of bytes to the inner digest md.update(input, offset, len); }
Processes the input.remaining() bytes in the ByteBuffer input.
Params:
  • input – the input byte buffer.
/** * Processes the <code>input.remaining()</code> bytes in the ByteBuffer * <code>input</code>. * * @param input the input byte buffer. */
protected void engineUpdate(ByteBuffer input) { if (first == true) { // compute digest for 1st pass; start with inner pad md.update(k_ipad); first = false; } md.update(input); }
Completes the HMAC computation and resets the HMAC for further use, maintaining the secret key that the HMAC was initialized with.
Returns:the HMAC result.
/** * Completes the HMAC computation and resets the HMAC for further use, * maintaining the secret key that the HMAC was initialized with. * * @return the HMAC result. */
protected byte[] engineDoFinal() { if (first == true) { // compute digest for 1st pass; start with inner pad md.update(k_ipad); } else { first = true; } try { // finish the inner digest byte[] tmp = md.digest(); // compute digest for 2nd pass; start with outer pad md.update(k_opad); // add result of 1st hash md.update(tmp); md.digest(tmp, 0, tmp.length); return tmp; } catch (DigestException e) { // should never occur throw new ProviderException(e); } }
Resets the HMAC for further use, maintaining the secret key that the HMAC was initialized with.
/** * Resets the HMAC for further use, maintaining the secret key that the * HMAC was initialized with. */
protected void engineReset() { if (first == false) { md.reset(); first = true; } } /* * Clones this object. */ public Object clone() throws CloneNotSupportedException { HmacCore copy = (HmacCore) super.clone(); copy.md = (MessageDigest) md.clone(); copy.k_ipad = k_ipad.clone(); copy.k_opad = k_opad.clone(); return copy; } // nested static class for the HmacSHA224 implementation public static final class HmacSHA224 extends HmacCore { public HmacSHA224() throws NoSuchAlgorithmException { super("SHA-224", 64); } } // nested static class for the HmacSHA256 implementation public static final class HmacSHA256 extends HmacCore { public HmacSHA256() throws NoSuchAlgorithmException { super("SHA-256", 64); } } // nested static class for the HmacSHA384 implementation public static final class HmacSHA384 extends HmacCore { public HmacSHA384() throws NoSuchAlgorithmException { super("SHA-384", 128); } } // nested static class for the HmacSHA512 implementation public static final class HmacSHA512 extends HmacCore { public HmacSHA512() throws NoSuchAlgorithmException { super("SHA-512", 128); } } }