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package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.params.ParametersWithIV;
/**
* Implements OpenPGP's rather strange version of Cipher-FeedBack (CFB) mode on top of a simple cipher. For further info see RFC 2440.
*/
public class PGPCFBBlockCipher
implements BlockCipher
{
private byte[] IV;
private byte[] FR;
private byte[] FRE;
private byte[] tmp;
private BlockCipher cipher;
private int count;
private int blockSize;
private boolean forEncryption;
private boolean inlineIv; // if false we don't need to prepend an IV
/**
* Basic constructor.
*
* @param cipher the block cipher to be used as the basis of the
* feedback mode.
* @param inlineIv if true this is for PGP CFB with a prepended iv.
*/
public PGPCFBBlockCipher(
BlockCipher cipher,
boolean inlineIv)
{
this.cipher = cipher;
this.inlineIv = inlineIv;
this.blockSize = cipher.getBlockSize();
this.IV = new byte[blockSize];
this.FR = new byte[blockSize];
this.FRE = new byte[blockSize];
this.tmp = new byte[blockSize];
}
/**
* return the underlying block cipher that we are wrapping.
*
* @return the underlying block cipher that we are wrapping.
*/
public BlockCipher getUnderlyingCipher()
{
return cipher;
}
/**
* return the algorithm name and mode.
*
* @return the name of the underlying algorithm followed by "/PGPCFB"
* and the block size in bits.
*/
public String getAlgorithmName()
{
if (inlineIv)
{
return cipher.getAlgorithmName() + "/PGPCFBwithIV";
}
else
{
return cipher.getAlgorithmName() + "/PGPCFB";
}
}
/**
* return the block size we are operating at.
*
* @return the block size we are operating at (in bytes).
*/
public int getBlockSize()
{
return cipher.getBlockSize();
}
/**
* Process one block of input from the array in and write it to
* the out array.
*
* @param in the array containing the input data.
* @param inOff offset into the in array the data starts at.
* @param out the array the output data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or
* space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
public int processBlock(
byte[] in,
int inOff,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if (inlineIv)
{
return (forEncryption) ? encryptBlockWithIV(in, inOff, out, outOff) : decryptBlockWithIV(in, inOff, out, outOff);
}
else
{
return (forEncryption) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff);
}
}
/**
* reset the chaining vector back to the IV and reset the underlying
* cipher.
*/
public void reset()
{
count = 0;
for (int i = 0; i != FR.length; i++)
{
if (inlineIv)
{
FR[i] = 0;
}
else
{
FR[i] = IV[i]; // if simple mode, key is IV (even if this is zero)
}
}
cipher.reset();
}
/**
* Initialise the cipher and, possibly, the initialisation vector (IV).
* If an IV isn't passed as part of the parameter, the IV will be all zeros.
* An IV which is too short is handled in FIPS compliant fashion.
*
* @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;
if (params instanceof ParametersWithIV)
{
ParametersWithIV ivParam = (ParametersWithIV)params;
byte[] iv = ivParam.getIV();
if (iv.length < IV.length)
{
// prepend the supplied IV with zeros (per FIPS PUB 81)
System.arraycopy(iv, 0, IV, IV.length - iv.length, iv.length);
for (int i = 0; i < IV.length - iv.length; i++)
{
IV[i] = 0;
}
}
else
{
System.arraycopy(iv, 0, IV, 0, IV.length);
}
reset();
cipher.init(true, ivParam.getParameters());
}
else
{
reset();
cipher.init(true, params);
}
}
/**
* Encrypt one byte of data according to CFB mode.
* @param data the byte to encrypt
* @param blockOff where am i in the current block, determines when to resync the block
* @returns the encrypted byte
*/
private byte encryptByte(byte data, int blockOff)
{
return (byte)(FRE[blockOff] ^ data);
}
/**
* Do the appropriate processing for CFB IV mode encryption.
*
* @param in the array containing the data to be encrypted.
* @param inOff offset into the in array the data starts at.
* @param out the array the encrypted data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or
* space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
private int encryptBlockWithIV(
byte[] in,
int inOff,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if ((inOff + blockSize) > in.length)
{
throw new DataLengthException("input buffer too short");
}
if (count == 0)
{
if ((outOff + 2 * blockSize + 2) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize; n++)
{
out[outOff + n] = encryptByte(IV[n], n);
}
System.arraycopy(out, outOff, FR, 0, blockSize);
cipher.processBlock(FR, 0, FRE, 0);
out[outOff + blockSize] = encryptByte(IV[blockSize - 2], 0);
out[outOff + blockSize + 1] = encryptByte(IV[blockSize - 1], 1);
System.arraycopy(out, outOff + 2, FR, 0, blockSize);
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize; n++)
{
out[outOff + blockSize + 2 + n] = encryptByte(in[inOff + n], n);
}
System.arraycopy(out, outOff + blockSize + 2, FR, 0, blockSize);
count += 2 * blockSize + 2;
return 2 * blockSize + 2;
}
else if (count >= blockSize + 2)
{
if ((outOff + blockSize) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize; n++)
{
out[outOff + n] = encryptByte(in[inOff + n], n);
}
System.arraycopy(out, outOff, FR, 0, blockSize);
}
return blockSize;
}
/**
* Do the appropriate processing for CFB IV mode decryption.
*
* @param in the array containing the data to be decrypted.
* @param inOff offset into the in array the data starts at.
* @param out the array the encrypted data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or
* space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
private int decryptBlockWithIV(
byte[] in,
int inOff,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if ((inOff + blockSize) > in.length)
{
throw new DataLengthException("input buffer too short");
}
if ((outOff + blockSize) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
if (count == 0)
{
for (int n = 0; n < blockSize; n++)
{
FR[n] = in[inOff + n];
}
cipher.processBlock(FR, 0, FRE, 0);
count += blockSize;
return 0;
}
else if (count == blockSize)
{
// copy in buffer so that this mode works if in and out are the same
System.arraycopy(in, inOff, tmp, 0, blockSize);
System.arraycopy(FR, 2, FR, 0, blockSize - 2);
FR[blockSize - 2] = tmp[0];
FR[blockSize - 1] = tmp[1];
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize - 2; n++)
{
out[outOff + n] = encryptByte(tmp[n + 2], n);
}
System.arraycopy(tmp, 2, FR, 0, blockSize - 2);
count += 2;
return blockSize - 2;
}
else if (count >= blockSize + 2)
{
// copy in buffer so that this mode works if in and out are the same
System.arraycopy(in, inOff, tmp, 0, blockSize);
out[outOff + 0] = encryptByte(tmp[0], blockSize - 2);
out[outOff + 1] = encryptByte(tmp[1], blockSize - 1);
System.arraycopy(tmp, 0, FR, blockSize - 2, 2);
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize - 2; n++)
{
out[outOff + n + 2] = encryptByte(tmp[n + 2], n);
}
System.arraycopy(tmp, 2, FR, 0, blockSize - 2);
}
return blockSize;
}
/**
* Do the appropriate processing for CFB mode encryption.
*
* @param in the array containing the data to be encrypted.
* @param inOff offset into the in array the data starts at.
* @param out the array the encrypted data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or
* space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
private int encryptBlock(
byte[] in,
int inOff,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if ((inOff + blockSize) > in.length)
{
throw new DataLengthException("input buffer too short");
}
if ((outOff + blockSize) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize; n++)
{
out[outOff + n] = encryptByte(in[inOff + n], n);
}
for (int n = 0; n < blockSize; n++)
{
FR[n] = out[outOff + n];
}
return blockSize;
}
/**
* Do the appropriate processing for CFB mode decryption.
*
* @param in the array containing the data to be decrypted.
* @param inOff offset into the in array the data starts at.
* @param out the array the encrypted data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or
* space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
private int decryptBlock(
byte[] in,
int inOff,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if ((inOff + blockSize) > in.length)
{
throw new DataLengthException("input buffer too short");
}
if ((outOff + blockSize) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
cipher.processBlock(FR, 0, FRE, 0);
for (int n = 0; n < blockSize; n++)
{
out[outOff + n] = encryptByte(in[inOff + n], n);
}
for (int n = 0; n < blockSize; n++)
{
FR[n] = in[inOff + n];
}
return blockSize;
}
}
