/* CipherAdapter.java -- 
   Copyright (C) 2002, 2003, 2006  Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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USA

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.jce.cipher;

import gnu.java.security.Registry;
import gnu.javax.crypto.cipher.CipherFactory;
import gnu.javax.crypto.cipher.IBlockCipher;
import gnu.javax.crypto.jce.spec.BlockCipherParameterSpec;
import gnu.javax.crypto.mode.IMode;
import gnu.javax.crypto.mode.ModeFactory;
import gnu.javax.crypto.pad.IPad;
import gnu.javax.crypto.pad.PadFactory;
import gnu.javax.crypto.pad.WrongPaddingException;

import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.CipherSpi;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.IvParameterSpec;

/**
 * The implementation of a generic {@link Cipher} <i>Adapter</i> class to wrap
 * GNU cipher instances.
 * <p>
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>) for
 * the {@link Cipher} class, which provides the functionality of symmetric-key
 * block ciphers, such as the AES.
 * <p>
 * This base class defines all of the abstract methods in {@link CipherSpi},
 * but does not define the (non-abstract) key wrapping functions that extended
 * the base cipher SPI, and these methods thus immediately throw an
 * {@link UnsupportedOperationException}. If a cipher implementation provides
 * this functionality, or if it in fact accepts parameters other than the key
 * and the initialization vector, the subclass should override those methods.
 * Otherwise a subclass need only call the {@link #CipherAdapter(String)}
 * constructor with the name of the cipher.
 */
class CipherAdapter
    extends CipherSpi
{
  /** Our cipher instance. */
  protected IBlockCipher cipher;
  /** Our mode instance. */
  protected IMode mode;
  /** Our padding instance. */
  protected IPad pad;
  /** The current key size. */
  protected int keyLen;
  /** Our attributes map. */
  protected Map attributes;
  /** An incomplete block. */
  protected byte[] partBlock;
  /** The number of bytes in {@link #partBlock}. */
  protected int partLen;
  /** The length of blocks we are processing. */
  protected int blockLen;

  /**
   * Protected constructor to be called by subclasses. The cipher name argument
   * should be the appropriate one listed in {@link Registry}. The basic cipher
   * instance is created, along with an instance of the
   * {@link gnu.javax.crypto.mode.ECB} mode and no padding.
   * 
   * @param cipherName The cipher to instantiate.
   * @param blockLen The block length to use.
   */
  protected CipherAdapter(String cipherName, int blockLen)
  {
    cipher = CipherFactory.getInstance(cipherName);
    attributes = new HashMap();
    this.blockLen = blockLen;
    mode = ModeFactory.getInstance("ECB", cipher, blockLen);
    attributes.put(IBlockCipher.CIPHER_BLOCK_SIZE, Integer.valueOf(blockLen));
  }

  /**
   * Creates a new cipher adapter with the default block size.
   * 
   * @param cipherName The cipher to instantiate.
   */
  protected CipherAdapter(String cipherName)
  {
    cipher = CipherFactory.getInstance(cipherName);
    blockLen = cipher.defaultBlockSize();
    attributes = new HashMap();
    mode = ModeFactory.getInstance("ECB", cipher, blockLen);
    attributes.put(IBlockCipher.CIPHER_BLOCK_SIZE, Integer.valueOf(blockLen));
  }

  protected void engineSetMode(String modeName) throws NoSuchAlgorithmException
  {
    if (modeName.length() >= 3
        && modeName.substring(0, 3).equalsIgnoreCase("CFB"))
      {
        if (modeName.length() > 3)
          {
            try
              {
                int bs = Integer.parseInt(modeName.substring(3));
                attributes.put(IMode.MODE_BLOCK_SIZE, Integer.valueOf(bs / 8));
              }
            catch (NumberFormatException nfe)
              {
                throw new NoSuchAlgorithmException(modeName);
              }
            modeName = "CFB";
          }
      }
    else
      attributes.remove(IMode.MODE_BLOCK_SIZE);
    mode = ModeFactory.getInstance(modeName, cipher, blockLen);
    if (mode == null)
      throw new NoSuchAlgorithmException(modeName);
  }

  protected void engineSetPadding(String padName) throws NoSuchPaddingException
  {
    if (padName.equalsIgnoreCase("NoPadding"))
      {
        pad = null;
        return;
      }
    pad = PadFactory.getInstance(padName);
    if (pad == null)
      throw new NoSuchPaddingException(padName);
  }

  protected int engineGetBlockSize()
  {
    if (cipher != null)
      return blockLen;
    return 0;
  }

  protected int engineGetOutputSize(int inputLen)
  {
    final int blockSize = mode.currentBlockSize();
    return ((inputLen + partLen) / blockSize) * blockSize;
  }

  protected byte[] engineGetIV()
  {
    byte[] iv = (byte[]) attributes.get(IMode.IV);
    if (iv == null)
      return null;
    return (byte[]) iv.clone();
  }

  protected AlgorithmParameters engineGetParameters()
  {
    byte[] iv = (byte[]) attributes.get(IMode.IV);
    int cipherBlockSize = cipher.currentBlockSize();
    BlockCipherParameterSpec spec = new BlockCipherParameterSpec(iv,
                                                                 cipherBlockSize,
                                                                 keyLen);
    AlgorithmParameters params;
    try
      {
        params = AlgorithmParameters.getInstance("BlockCipherParameters");
        params.init(spec);
      }
    catch (NoSuchAlgorithmException nsae)
      {
        return null;
      }
    catch (InvalidParameterSpecException ipse)
      {
        return null;
      }
    return params;
  }

  protected void engineInit(int opmode, Key key, SecureRandom random)
      throws InvalidKeyException
  {
    try
      {
        engineInit(opmode, key, (AlgorithmParameterSpec) null, random);
      }
    catch (InvalidAlgorithmParameterException e)
      {
        throw new InvalidKeyException(e.getMessage(), e);
      }
  }

  /**
   * Executes initialization logic after all parameters have been handled by the
   * engineInit()s.
   * 
   * @param opmode the desired mode of operation for this instance.
   * @param key the key material to use for initialization.
   * @param random a source of randmoness to use if/when needed.
   * @throws InvalidKeyException if <code>key</code> is invalid or the cipher
   *           needs extra parameters which can not be derived from
   *           <code>key</code>; e.g. an IV.
   */
  private void engineInitHandler(int opmode, Key key, SecureRandom random)
      throws InvalidKeyException
  {
    switch (opmode)
      {
      case Cipher.ENCRYPT_MODE:
        attributes.put(IMode.STATE, Integer.valueOf(IMode.ENCRYPTION));
        break;
      case Cipher.DECRYPT_MODE:
        attributes.put(IMode.STATE, Integer.valueOf(IMode.DECRYPTION));
        break;
      }
    if (! key.getFormat().equalsIgnoreCase("RAW"))
      throw new InvalidKeyException("bad key format " + key.getFormat());
    byte[] kb = key.getEncoded();
    int kbLength = kb.length;
    if (keyLen == 0)
      {
        // no key-size given; instead key-material is provided in kb --which
        // can be more than what we need.  if we don't cull this down to what
        // the cipher likes/wants we may get an InvalidKeyException.
        //
        // try to find the largest key-size value that is less than or equal
        // to kbLength
        for (Iterator it = cipher.keySizes(); it.hasNext();)
          {
            int aKeySize = ((Integer) it.next()).intValue();
            if (aKeySize == kbLength)
              {
                keyLen = aKeySize;
                break;
              }
            else if (aKeySize < kbLength)
              keyLen = aKeySize;
            else // all remaining key-sizes are longer than kb.length
              break;
          }
      }
    if (keyLen == 0)
      {
        // we were unable to find a key-size, among those advertised by the
        // cipher, that is less than or equal to the length of the kb array.
        // set keyLen to kbLength.  either the cipher implementation will throw
        // an InvalidKeyException, or it is implemented in a way which can deal
        // with an unsupported key-size. 
        keyLen = kbLength;
      }
    if (keyLen < kbLength)
      {
        byte[] kbb = kb;
        kb = new byte[keyLen];
        System.arraycopy(kbb, 0, kb, 0, keyLen);
      }
    attributes.put(IBlockCipher.KEY_MATERIAL, kb);
    reset();
  }

  protected void engineInit(int opmode, Key key, AlgorithmParameterSpec params,
                            SecureRandom random) throws InvalidKeyException,
      InvalidAlgorithmParameterException
  {
    if (params == null)
      {
        // All cipher modes require parameters (like an IV) except ECB. When
        // these cant be derived from the given key then it must be generated
        // randomly if in ENCRYPT or WRAP mode. Parameters that have defaults
        // for our cipher must be set to these defaults.
        if (! mode.name().toLowerCase().startsWith(Registry.ECB_MODE + "("))
          {
            switch (opmode)
              {
              case Cipher.ENCRYPT_MODE:
              case Cipher.WRAP_MODE:
                byte[] iv = new byte[blockLen];
                random.nextBytes(iv);
                attributes.put(IMode.IV, iv);
                break;
              default:
                throw new InvalidAlgorithmParameterException(
                    "Required algorithm parameters are missing for mode: "
                    + mode.name());
              }
          }
        // Add default for block length etc.
        blockLen = cipher.defaultBlockSize();
        attributes.put(IBlockCipher.CIPHER_BLOCK_SIZE,
                       Integer.valueOf(blockLen));
        keyLen = 0;
      }
    else if (params instanceof BlockCipherParameterSpec)
      {
        BlockCipherParameterSpec bcps = (BlockCipherParameterSpec) params;
        blockLen = bcps.getBlockSize();
        attributes.put(IBlockCipher.CIPHER_BLOCK_SIZE, Integer.valueOf(blockLen));
        attributes.put(IMode.IV, bcps.getIV());
        keyLen = bcps.getKeySize();
      }
    else if (params instanceof IvParameterSpec)
      {
        // The size of the IV must match the block size
        if (((IvParameterSpec) params).getIV().length != cipher.defaultBlockSize())
          {
            throw new InvalidAlgorithmParameterException();
          }
        
        attributes.put(IMode.IV, ((IvParameterSpec) params).getIV());
        blockLen = cipher.defaultBlockSize();
        attributes.put(IBlockCipher.CIPHER_BLOCK_SIZE, Integer.valueOf(blockLen));
        keyLen = 0;
      }
    engineInitHandler(opmode, key, random);
  }

  protected void engineInit(int opmode, Key key, AlgorithmParameters params,
                            SecureRandom random) throws InvalidKeyException,
      InvalidAlgorithmParameterException
  {
    AlgorithmParameterSpec spec = null;
    try
      {
        if (params != null)
          spec = params.getParameterSpec(BlockCipherParameterSpec.class);
      }
    catch (InvalidParameterSpecException ignored)
      {
      }
    engineInit(opmode, key, spec, random);
  }

  protected byte[] engineUpdate(byte[] input, int inOff, int inLen)
  {
    if (inLen == 0) // nothing to process
      return new byte[0];
    final int blockSize = mode.currentBlockSize();
    int blockCount = (partLen + inLen) / blockSize;

    // always keep data for unpadding in padded decryption mode;
    // might even be a complete block
    if (pad != null
        && ((Integer) attributes.get(IMode.STATE)).intValue() == IMode.DECRYPTION
        && (partLen + inLen) % blockSize == 0)
      blockCount--;

    final byte[] out = new byte[blockCount * blockSize];
    try
      {
        engineUpdate(input, inOff, inLen, out, 0);
      }
    catch (ShortBufferException x) // should not happen
      {
        x.printStackTrace(System.err);
      }
    return out;
  }

  protected int engineUpdate(byte[] in, int inOff, int inLen, byte[] out,
                             int outOff) throws ShortBufferException
  {
    if (inLen == 0) // nothing to process
      return 0;
    final int blockSize = mode.currentBlockSize();
    int blockCount = (partLen + inLen) / blockSize;

    // always keep data for unpadding in padded decryption mode;
    // might even be a complete block
    if (pad != null
        && ((Integer) attributes.get(IMode.STATE)).intValue() == IMode.DECRYPTION
        && (partLen + inLen) % blockSize == 0)
      blockCount--;

    final int result = blockCount * blockSize;
    if (result > out.length - outOff)
      throw new ShortBufferException();
    if (blockCount == 0) // not enough bytes for even 1 block
      {
        System.arraycopy(in, inOff, partBlock, partLen, inLen);
        partLen += inLen;
        return 0;
      }
    final byte[] buf;
    // we have enough bytes for at least 1 block
    if (partLen == 0) // if no cached bytes use input
      buf = in;
    else // prefix input with cached bytes
      {
        buf = new byte[partLen + inLen];
        System.arraycopy(partBlock, 0, buf, 0, partLen);
        if (in != null && inLen > 0)
          System.arraycopy(in, inOff, buf, partLen, inLen);
        inOff = 0;
      }
    for (int i = 0; i < blockCount; i++) // update blockCount * blockSize
      {
        mode.update(buf, inOff, out, outOff);
        inOff += blockSize;
        outOff += blockSize;
      }
    partLen += inLen - result;
    if (partLen > 0) // cache remaining bytes from buf
      System.arraycopy(buf, inOff, partBlock, 0, partLen);
    return result;
  }

  protected byte[] engineDoFinal(byte[] input, int off, int len)
      throws IllegalBlockSizeException, BadPaddingException
  {
    final byte[] result;
    final byte[] buf = engineUpdate(input, off, len);
    if (pad != null)
      {
        switch (((Integer) attributes.get(IMode.STATE)).intValue())
          {
          case IMode.ENCRYPTION:
            byte[] padding = pad.pad(partBlock, 0, partLen);
            byte[] buf2 = engineUpdate(padding, 0, padding.length);
            result = new byte[buf.length + buf2.length];
            System.arraycopy(buf, 0, result, 0, buf.length);
            System.arraycopy(buf2, 0, result, buf.length, buf2.length);
            break;
          case IMode.DECRYPTION:
            int padLen;
            byte[] buf3 = new byte[buf.length + partLen];
            try
              {
                if (partLen != mode.currentBlockSize())
                  throw new WrongPaddingException();
                System.arraycopy(buf, 0, buf3, 0, buf.length);
                mode.update(partBlock, 0, buf3, buf.length);
                padLen = pad.unpad(buf3, 0, buf3.length);
              }
            catch (WrongPaddingException wpe)
              {
                throw new BadPaddingException(wpe.getMessage());
              }
            result = new byte[buf3.length - padLen];
            System.arraycopy(buf3, 0, result, 0, result.length);
            break;
          default:
            throw new IllegalStateException();
          }
      }
    else
      {
        if (partLen > 0)
          throw new IllegalBlockSizeException(partLen + " trailing bytes");
        result = buf;
      }

    try
      {
        reset();
      }
    catch (InvalidKeyException ike)
      {
        // Should not happen; if we initialized it with the current
        // parameters before, we should be able to do it again.
        throw new Error(ike);
      }
    return result;
  }

  protected int engineDoFinal(byte[] in, int inOff, int inLen, byte[] out,
                              int outOff) throws BadPaddingException,
      IllegalBlockSizeException, ShortBufferException
  {
    byte[] buf = engineDoFinal(in, inOff, inLen);
    if (out.length + outOff < buf.length)
      throw new ShortBufferException();
    System.arraycopy(buf, 0, out, outOff, buf.length);
    return buf.length;
  }

  private void reset() throws InvalidKeyException
  {
    mode.reset();
    mode.init(attributes);
    if (pad != null)
      {
        pad.reset();
        pad.init(blockLen);
      }
    partBlock = new byte[blockLen];
    partLen = 0;
  }
}