package org.bouncycastle.crypto;
/**
* A wrapper class that allows block ciphers to be used to process data in
* a piecemeal fashion. The BufferedBlockCipher outputs a block only when the
* buffer is full and more data is being added, or on a doFinal.
* <p>
* Note: in the case where the underlying cipher is either a CFB cipher or an
* OFB one the last block may not be a multiple of the block size.
*/
public class BufferedBlockCipher
{
protected byte[] buf;
protected int bufOff;
protected boolean forEncryption;
protected BlockCipher cipher;
protected boolean partialBlockOkay;
protected boolean pgpCFB;
/**
* constructor for subclasses
*/
protected BufferedBlockCipher()
{
}
/**
* Create a buffered block cipher without padding.
*
* @param cipher the underlying block cipher this buffering object wraps.
*/
public BufferedBlockCipher(
BlockCipher cipher)
{
this.cipher = cipher;
buf = new byte[cipher.getBlockSize()];
bufOff = 0;
//
// check if we can handle partial blocks on doFinal.
//
String name = cipher.getAlgorithmName();
int idx = name.indexOf('/') + 1;
pgpCFB = (idx > 0 && name.startsWith("PGP", idx));
if (pgpCFB)
{
partialBlockOkay = true;
}
else
{
partialBlockOkay = (idx > 0 && (name.startsWith("CFB", idx) || name.startsWith("OFB", idx) || name.startsWith("OpenPGP", idx) || name.startsWith("SIC", idx) || name.startsWith("GCTR", idx)));
}
}
/**
* return the cipher this object wraps.
*
* @return the cipher this object wraps.
*/
public BlockCipher getUnderlyingCipher()
{
return cipher;
}
/**
* 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();
cipher.init(forEncryption, params);
}
/**
* return the blocksize for the underlying cipher.
*
* @return the blocksize for the underlying cipher.
*/
public int getBlockSize()
{
return cipher.getBlockSize();
}
/**
* 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;
if (pgpCFB)
{
leftOver = total % buf.length - (cipher.getBlockSize() + 2);
}
else
{
leftOver = total % buf.length;
}
return total - leftOver;
}
/**
* return the 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;
if (pgpCFB)
{
leftOver = total % buf.length - (cipher.getBlockSize() + 2);
}
else
{
leftOver = total % buf.length;
if (leftOver == 0)
{
return total;
}
}
return total - leftOver + buf.length;
}
/**
* 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;
buf[bufOff++] = in;
if (bufOff == buf.length)
{
resultLen = cipher.processBlock(buf, 0, out, outOff);
bufOff = 0;
}
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 DataLengthException("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;
if (bufOff == buf.length)
{
resultLen += cipher.processBlock(buf, 0, out, outOff + resultLen);
bufOff = 0;
}
return resultLen;
}
/**
* Process the last block in the buffer.
*
* @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 the input is not block size aligned and should be.
* @exception IllegalStateException if the underlying cipher is not
* initialised.
* @exception InvalidCipherTextException if padding is expected and not found.
* @exception DataLengthException if the input is not block size
* aligned.
*/
public int doFinal(
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException, InvalidCipherTextException
{
int resultLen = 0;
if (outOff + bufOff > out.length)
{
throw new DataLengthException("output buffer too short for doFinal()");
}
if (bufOff != 0 && partialBlockOkay)
{
cipher.processBlock(buf, 0, buf, 0);
resultLen = bufOff;
bufOff = 0;
System.arraycopy(buf, 0, out, outOff, resultLen);
}
else if (bufOff != 0)
{
throw new DataLengthException("data not block size aligned");
}
reset();
return resultLen;
}
/**
* Reset the buffer and cipher. After resetting the object is in the same
* state as it was after the last init (if there was one).
*/
public void reset()
{
//
// clean the buffer.
//
for (int i = 0; i < buf.length; i++)
{
buf[i] = 0;
}
bufOff = 0;
//
// reset the underlying cipher.
//
cipher.reset();
}
}
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