package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.macs.CBCBlockCipherMac;
import org.bouncycastle.crypto.params.CCMParameters;
import org.bouncycastle.crypto.params.ParametersWithIV;
/**
* Implements the Counter with Cipher Block Chaining mode (CCM) detailed in
* NIST Special Publication 800-38C.
* <p>
* <b>Note</b>: this mode is a packet mode - it needs all the data up front.
*/
public class CCMBlockCipher
{
private BlockCipher cipher = null;
private int blockSize;
private boolean forEncryption;
private CCMParameters params;
private byte[] macBlock;
/**
* Basic constructor.
*
* @param c the block cipher to be used.
*/
public CCMBlockCipher(BlockCipher c)
{
this.cipher = c;
this.blockSize = c.getBlockSize();
this.macBlock = new byte[blockSize];
if (blockSize != 16)
{
throw new IllegalArgumentException("cipher required with a block size of 16.");
}
}
/**
* return the underlying block cipher that we are wrapping.
*
* @return the underlying block cipher that we are wrapping.
*/
public BlockCipher getUnderlyingCipher()
{
return cipher;
}
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException
{
if (!(params instanceof CCMParameters))
{
throw new IllegalArgumentException("parameters need to be CCMParameters");
}
this.forEncryption = forEncryption;
this.params = (CCMParameters)params;
}
public String getAlgorithmName()
{
return cipher.getAlgorithmName() + "/CCM";
}
/**
* Returns a byte array containing the mac calculated as part of the
* last encrypt or decrypt operation.
*
* @return the last mac calculated.
*/
public byte[] getMac()
{
byte[] mac = new byte[params.getMacSize() / 8];
System.arraycopy(macBlock, 0, mac, 0, mac.length);
return mac;
}
public byte[] processPacket(byte[] in, int inOff, int inLen)
throws IllegalStateException, InvalidCipherTextException
{
if (params == null)
{
throw new IllegalStateException("CCM cipher unitialized.");
}
BlockCipher ctrCipher = new SICBlockCipher(cipher);
byte[] iv = new byte[blockSize];
byte[] nonce = params.getNonce();
int macSize = params.getMacSize() / 8;
byte[] out;
iv[0] = (byte)(((15 - nonce.length) - 1) & 0x7);
System.arraycopy(nonce, 0, iv, 1, nonce.length);
ctrCipher.init(forEncryption, new ParametersWithIV(params.getKey(), iv));
if (forEncryption)
{
int index = inOff;
int outOff = 0;
out = new byte[inLen + macSize];
calculateMac(in, inOff, inLen, macBlock);
ctrCipher.processBlock(macBlock, 0, macBlock, 0); // S0
while (index < inLen - blockSize) // S1...
{
ctrCipher.processBlock(in, index, out, outOff);
outOff += blockSize;
index += blockSize;
}
byte[] block = new byte[blockSize];
System.arraycopy(in, index, block, 0, inLen - index);
ctrCipher.processBlock(block, 0, block, 0);
System.arraycopy(block, 0, out, outOff, inLen - index);
outOff += inLen - index;
System.arraycopy(macBlock, 0, out, outOff, out.length - outOff);
}
else
{
int index = inOff;
int outOff = 0;
out = new byte[inLen - macSize];
System.arraycopy(in, inOff + inLen - macSize, macBlock, 0, macSize);
ctrCipher.processBlock(macBlock, 0, macBlock, 0);
for (int i = macSize; i != macBlock.length; i++)
{
macBlock[i] = 0;
}
while (outOff < out.length - blockSize)
{
ctrCipher.processBlock(in, index, out, outOff);
outOff += blockSize;
index += blockSize;
}
byte[] block = new byte[blockSize];
System.arraycopy(in, index, block, 0, out.length - outOff);
ctrCipher.processBlock(block, 0, block, 0);
System.arraycopy(block, 0, out, outOff, out.length - outOff);
byte[] calculatedMacBlock = new byte[blockSize];
calculateMac(out, 0, out.length, calculatedMacBlock);
if (!areEqual(macBlock, calculatedMacBlock))
{
throw new InvalidCipherTextException("mac check in CCM failed");
}
}
return out;
}
private int calculateMac(byte[] data, int dataOff, int dataLen, byte[] macBlock)
{
Mac cMac = new CBCBlockCipherMac(cipher, params.getMacSize());
byte[] nonce = params.getNonce();
byte[] associatedText = params.getAssociatedText();
cMac.init(params.getKey());
//
// build b0
//
byte[] b0 = new byte[16];
if (associatedText != null && associatedText.length != 0)
{
b0[0] |= 0x40;
}
b0[0] |= (((cMac.getMacSize() - 2) / 2) & 0x7) << 3;
b0[0] |= ((15 - nonce.length) - 1) & 0x7;
System.arraycopy(nonce, 0, b0, 1, nonce.length);
int q = dataLen;
int count = 1;
while (q > 0)
{
b0[b0.length - count] = (byte)(q & 0xff);
q >>>= 8;
count++;
}
cMac.update(b0, 0, b0.length);
//
// process associated text
//
if (associatedText != null)
{
int extra;
if (associatedText.length < ((1 << 16) - (1 << 8)))
{
cMac.update((byte)(associatedText.length >> 8));
cMac.update((byte)associatedText.length);
extra = 2;
}
else // can't go any higher than 2^32
{
cMac.update((byte)0xff);
cMac.update((byte)0xfe);
cMac.update((byte)(associatedText.length >> 24));
cMac.update((byte)(associatedText.length >> 16));
cMac.update((byte)(associatedText.length >> 8));
cMac.update((byte)associatedText.length);
extra = 6;
}
cMac.update(associatedText, 0, associatedText.length);
extra = (extra + associatedText.length) % 16;
if (extra != 0)
{
for (int i = 0; i != 16 - extra; i++)
{
cMac.update((byte)0x00);
}
}
}
//
// add the text
//
cMac.update(data, dataOff, dataLen);
return cMac.doFinal(macBlock, 0);
}
/**
* compare two byte arrays.
*/
private boolean areEqual(
byte[] a,
byte[] b)
{
if (a.length != b.length)
{
return false;
}
for (int i = 0; i != b.length; i++)
{
if (a[i] != b[i])
{
return false;
}
}
return true;
}
}
|
