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package org.bouncycastle.crypto.paddings;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.BufferedBlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.params.ParametersWithRandom;
/**
* A wrapper class that allows block ciphers to be used to process data in
* a piecemeal fashion with padding. The PaddedBufferedBlockCipher
* outputs a block only when the buffer is full and more data is being added,
* or on a doFinal (unless the current block in the buffer is a pad block).
* The default padding mechanism used is the one outlined in PKCS5/PKCS7.
*/
public class PaddedBufferedBlockCipher
extends BufferedBlockCipher
{
BlockCipherPadding padding;
/**
* Create a buffered block cipher with the desired padding.
*
* @param cipher the underlying block cipher this buffering object wraps.
* @param padding the padding type.
*/
public PaddedBufferedBlockCipher(
BlockCipher cipher,
BlockCipherPadding padding)
{
this.cipher = cipher;
this.padding = padding;
buf = new byte[cipher.getBlockSize()];
bufOff = 0;
}
/**
* Create a buffered block cipher PKCS7 padding
*
* @param cipher the underlying block cipher this buffering object wraps.
*/
public PaddedBufferedBlockCipher(
BlockCipher cipher)
{
this(cipher, new PKCS7Padding());
}
/**
* initialise the cipher.
*
* @param forEncryption if true the cipher is initialised for
* encryption, if false for decryption.
* @param params the key and other data required by the cipher.
* @exception IllegalArgumentException if the params argument is
* inappropriate.
*/
public void init(
boolean forEncryption,
CipherParameters params)
throws IllegalArgumentException
{
this.forEncryption = forEncryption;
reset();
if (params instanceof ParametersWithRandom)
{
ParametersWithRandom p = (ParametersWithRandom)params;
padding.init(p.getRandom());
cipher.init(forEncryption, p.getParameters());
}
else
{
padding.init(null);
cipher.init(forEncryption, params);
}
}
/**
* return the minimum size of the output buffer required for an update
* plus a doFinal with an input of len bytes.
*
* @param len the length of the input.
* @return the space required to accommodate a call to update and doFinal
* with len bytes of input.
*/
public int getOutputSize(
int len)
{
int total = len + bufOff;
int leftOver = total % buf.length;
if (leftOver == 0)
{
if (forEncryption)
{
return total + buf.length;
}
return total;
}
return total - leftOver + buf.length;
}
/**
* return the size of the output buffer required for an update
* an input of len bytes.
*
* @param len the length of the input.
* @return the space required to accommodate a call to update
* with len bytes of input.
*/
public int getUpdateOutputSize(
int len)
{
int total = len + bufOff;
int leftOver = total % buf.length;
if (leftOver == 0)
{
return Math.max(0, total - buf.length);
}
return total - leftOver;
}
/**
* process a single byte, producing an output block if neccessary.
*
* @param in the input byte.
* @param out the space for any output that might be produced.
* @param outOff the offset from which the output will be copied.
* @return the number of output bytes copied to out.
* @exception DataLengthException if there isn't enough space in out.
* @exception IllegalStateException if the cipher isn't initialised.
*/
public int processByte(
byte in,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
int resultLen = 0;
if (bufOff == buf.length)
{
resultLen = cipher.processBlock(buf, 0, out, outOff);
bufOff = 0;
}
buf[bufOff++] = in;
return resultLen;
}
/**
* process an array of bytes, producing output if necessary.
*
* @param in the input byte array.
* @param inOff the offset at which the input data starts.
* @param len the number of bytes to be copied out of the input array.
* @param out the space for any output that might be produced.
* @param outOff the offset from which the output will be copied.
* @return the number of output bytes copied to out.
* @exception DataLengthException if there isn't enough space in out.
* @exception IllegalStateException if the cipher isn't initialised.
*/
public int processBytes(
byte[] in,
int inOff,
int len,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if (len < 0)
{
throw new IllegalArgumentException("Can't have a negative input length!");
}
int blockSize = getBlockSize();
int length = getUpdateOutputSize(len);
if (length > 0)
{
if ((outOff + length) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
}
int resultLen = 0;
int gapLen = buf.length - bufOff;
if (len > gapLen)
{
System.arraycopy(in, inOff, buf, bufOff, gapLen);
resultLen += cipher.processBlock(buf, 0, out, outOff);
bufOff = 0;
len -= gapLen;
inOff += gapLen;
while (len > buf.length)
{
resultLen += cipher.processBlock(in, inOff, out, outOff + resultLen);
len -= blockSize;
inOff += blockSize;
}
}
System.arraycopy(in, inOff, buf, bufOff, len);
bufOff += len;
return resultLen;
}
/**
* Process the last block in the buffer. If the buffer is currently
* full and padding needs to be added a call to doFinal will produce
* 2 * getBlockSize() bytes.
*
* @param out the array the block currently being held is copied into.
* @param outOff the offset at which the copying starts.
* @return the number of output bytes copied to out.
* @exception DataLengthException if there is insufficient space in out for
* the output or we are decrypting and the input is not block size aligned.
* @exception IllegalStateException if the underlying cipher is not
* initialised.
* @exception InvalidCipherTextException if padding is expected and not found.
*/
public int doFinal(
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException, InvalidCipherTextException
{
int blockSize = cipher.getBlockSize();
int resultLen = 0;
if (forEncryption)
{
if (bufOff == blockSize)
{
if ((outOff + 2 * blockSize) > out.length)
{
reset();
throw new OutputLengthException("output buffer too short");
}
resultLen = cipher.processBlock(buf, 0, out, outOff);
bufOff = 0;
}
padding.addPadding(buf, bufOff);
resultLen += cipher.processBlock(buf, 0, out, outOff + resultLen);
reset();
}
else
{
if (bufOff == blockSize)
{
resultLen = cipher.processBlock(buf, 0, buf, 0);
bufOff = 0;
}
else
{
reset();
throw new DataLengthException("last block incomplete in decryption");
}
try
{
resultLen -= padding.padCount(buf);
System.arraycopy(buf, 0, out, outOff, resultLen);
}
finally
{
reset();
}
}
return resultLen;
}
}
