using System;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Security;
namespace Org.BouncyCastle.Crypto.Paddings{
/**
* 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
: BufferedBlockCipher
{
private readonly IBlockCipherPadding 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(
IBlockCipher cipher,
IBlockCipherPadding 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(
IBlockCipher cipher)
: this(cipher, new Pkcs7Padding()) { }
/**
* initialise the cipher.
*
* @param forEncryption if true the cipher is initialised for
* encryption, if false for decryption.
* @param param the key and other data required by the cipher.
* @exception ArgumentException if the parameters argument is
* inappropriate.
*/
public override void Init(
bool forEncryption,
ICipherParameters parameters)
{
this.forEncryption = forEncryption;
SecureRandom initRandom = null;
if (parameters is ParametersWithRandom)
{
ParametersWithRandom p = (ParametersWithRandom)parameters;
initRandom = p.Random;
parameters = p.Parameters;
}
Reset();
padding.Init(initRandom);
cipher.Init(forEncryption, parameters);
}
/**
* 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 override int GetOutputSize(
int length)
{
int total = length + 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 override int GetUpdateOutputSize(
int length)
{
int total = length + bufOff;
int leftOver = total % buf.Length;
if (leftOver == 0)
{
return 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 InvalidOperationException if the cipher isn't initialised.
*/
public override int ProcessByte(
byte input,
byte[] output,
int outOff)
{
int resultLen = 0;
if (bufOff == buf.Length)
{
resultLen = cipher.ProcessBlock(buf, 0, output, outOff);
bufOff = 0;
}
buf[bufOff++] = input;
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 InvalidOperationException if the cipher isn't initialised.
*/
public override int ProcessBytes(
byte[] input,
int inOff,
int length,
byte[] output,
int outOff)
{
if (length < 0)
{
throw new ArgumentException("Can't have a negative input length!");
}
int blockSize = GetBlockSize();
int outLength = GetUpdateOutputSize(length);
if (outLength > 0)
{
if ((outOff + outLength) > output.Length)
{
throw new DataLengthException("output buffer too short");
}
}
int resultLen = 0;
int gapLen = buf.Length - bufOff;
if (length > gapLen)
{
Array.Copy(input, inOff, buf, bufOff, gapLen);
resultLen += cipher.ProcessBlock(buf, 0, output, outOff);
bufOff = 0;
length -= gapLen;
inOff += gapLen;
while (length > buf.Length)
{
resultLen += cipher.ProcessBlock(input, inOff, output, outOff + resultLen);
length -= blockSize;
inOff += blockSize;
}
}
Array.Copy(input, inOff, buf, bufOff, length);
bufOff += length;
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 InvalidOperationException if the underlying cipher is not
* initialised.
* @exception InvalidCipherTextException if padding is expected and not found.
*/
public override int DoFinal(
byte[] output,
int outOff)
{
int blockSize = cipher.GetBlockSize();
int resultLen = 0;
if (forEncryption)
{
if (bufOff == blockSize)
{
if ((outOff + 2 * blockSize) > output.Length)
{
Reset();
throw new DataLengthException("output buffer too short");
}
resultLen = cipher.ProcessBlock(buf, 0, output, outOff);
bufOff = 0;
}
padding.AddPadding(buf, bufOff);
resultLen += cipher.ProcessBlock(buf, 0, output, 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);
Array.Copy(buf, 0, output, outOff, resultLen);
}
finally
{
Reset();
}
}
return resultLen;
}
}
}
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