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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.7. Note: this package includes the IDEA and NTRU encryption algorithms.
package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.modes.gcm.GCMExponentiator;
import org.bouncycastle.crypto.modes.gcm.GCMMultiplier;
import org.bouncycastle.crypto.modes.gcm.GCMUtil;
import org.bouncycastle.crypto.modes.gcm.Tables1kGCMExponentiator;
import org.bouncycastle.crypto.modes.gcm.Tables8kGCMMultiplier;
import org.bouncycastle.crypto.params.AEADParameters;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.Pack;
/**
* Implements the Galois/Counter mode (GCM) detailed in
* NIST Special Publication 800-38D.
*/
public class GCMBlockCipher
implements AEADBlockCipher
{
private static final int BLOCK_SIZE = 16;
// not final due to a compiler bug
private BlockCipher cipher;
private GCMMultiplier multiplier;
private GCMExponentiator exp;
// These fields are set by init and not modified by processing
private boolean forEncryption;
private boolean initialised;
private int macSize;
private byte[] lastKey;
private byte[] nonce;
private byte[] initialAssociatedText;
private byte[] H;
private byte[] J0;
// These fields are modified during processing
private byte[] bufBlock;
private byte[] macBlock;
private byte[] S, S_at, S_atPre;
private byte[] counter;
private int blocksRemaining;
private int bufOff;
private long totalLength;
private byte[] atBlock;
private int atBlockPos;
private long atLength;
private long atLengthPre;
public GCMBlockCipher(BlockCipher c)
{
this(c, null);
}
public GCMBlockCipher(BlockCipher c, GCMMultiplier m)
{
if (c.getBlockSize() != BLOCK_SIZE)
{
throw new IllegalArgumentException(
"cipher required with a block size of " + BLOCK_SIZE + ".");
}
if (m == null)
{
// TODO Consider a static property specifying default multiplier
m = new Tables8kGCMMultiplier();
}
this.cipher = c;
this.multiplier = m;
}
public BlockCipher getUnderlyingCipher()
{
return cipher;
}
public String getAlgorithmName()
{
return cipher.getAlgorithmName() + "/GCM";
}
/**
* NOTE: MAC sizes from 32 bits to 128 bits (must be a multiple of 8) are supported. The default is 128 bits.
* Sizes less than 96 are not recommended, but are supported for specialized applications.
*/
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException
{
this.forEncryption = forEncryption;
this.macBlock = null;
this.initialised = true;
KeyParameter keyParam;
byte[] newNonce = null;
if (params instanceof AEADParameters)
{
AEADParameters param = (AEADParameters)params;
newNonce = param.getNonce();
initialAssociatedText = param.getAssociatedText();
int macSizeBits = param.getMacSize();
if (macSizeBits < 32 || macSizeBits > 128 || macSizeBits % 8 != 0)
{
throw new IllegalArgumentException("Invalid value for MAC size: " + macSizeBits);
}
macSize = macSizeBits / 8;
keyParam = param.getKey();
}
else if (params instanceof ParametersWithIV)
{
ParametersWithIV param = (ParametersWithIV)params;
newNonce = param.getIV();
initialAssociatedText = null;
macSize = 16;
keyParam = (KeyParameter)param.getParameters();
}
else
{
throw new IllegalArgumentException("invalid parameters passed to GCM");
}
int bufLength = forEncryption ? BLOCK_SIZE : (BLOCK_SIZE + macSize);
this.bufBlock = new byte[bufLength];
if (newNonce == null || newNonce.length < 1)
{
throw new IllegalArgumentException("IV must be at least 1 byte");
}
if (forEncryption)
{
if (nonce != null && Arrays.areEqual(nonce, newNonce))
{
if (keyParam == null)
{
throw new IllegalArgumentException("cannot reuse nonce for GCM encryption");
}
if (lastKey != null && Arrays.areEqual(lastKey, keyParam.getKey()))
{
throw new IllegalArgumentException("cannot reuse nonce for GCM encryption");
}
}
}
nonce = newNonce;
if (keyParam != null)
{
lastKey = keyParam.getKey();
}
// TODO Restrict macSize to 16 if nonce length not 12?
// Cipher always used in forward mode
// if keyParam is null we're reusing the last key.
if (keyParam != null)
{
cipher.init(true, keyParam);
this.H = new byte[BLOCK_SIZE];
cipher.processBlock(H, 0, H, 0);
// GCMMultiplier tables don't change unless the key changes (and are expensive to init)
multiplier.init(H);
exp = null;
}
else if (this.H == null)
{
throw new IllegalArgumentException("Key must be specified in initial init");
}
this.J0 = new byte[BLOCK_SIZE];
if (nonce.length == 12)
{
System.arraycopy(nonce, 0, J0, 0, nonce.length);
this.J0[BLOCK_SIZE - 1] = 0x01;
}
else
{
gHASH(J0, nonce, nonce.length);
byte[] X = new byte[BLOCK_SIZE];
Pack.longToBigEndian((long)nonce.length * 8, X, 8);
gHASHBlock(J0, X);
}
this.S = new byte[BLOCK_SIZE];
this.S_at = new byte[BLOCK_SIZE];
this.S_atPre = new byte[BLOCK_SIZE];
this.atBlock = new byte[BLOCK_SIZE];
this.atBlockPos = 0;
this.atLength = 0;
this.atLengthPre = 0;
this.counter = Arrays.clone(J0);
this.blocksRemaining = -2; // page 8, len(P) <= 2^39 - 256, 1 block used by tag but done on J0
this.bufOff = 0;
this.totalLength = 0;
if (initialAssociatedText != null)
{
processAADBytes(initialAssociatedText, 0, initialAssociatedText.length);
}
}
public byte[] getMac()
{
if (macBlock == null)
{
return new byte[macSize];
}
return Arrays.clone(macBlock);
}
public int getOutputSize(int len)
{
int totalData = len + bufOff;
if (forEncryption)
{
return totalData + macSize;
}
return totalData < macSize ? 0 : totalData - macSize;
}
public int getUpdateOutputSize(int len)
{
int totalData = len + bufOff;
if (!forEncryption)
{
if (totalData < macSize)
{
return 0;
}
totalData -= macSize;
}
return totalData - totalData % BLOCK_SIZE;
}
public void processAADByte(byte in)
{
checkStatus();
atBlock[atBlockPos] = in;
if (++atBlockPos == BLOCK_SIZE)
{
// Hash each block as it fills
gHASHBlock(S_at, atBlock);
atBlockPos = 0;
atLength += BLOCK_SIZE;
}
}
public void processAADBytes(byte[] in, int inOff, int len)
{
checkStatus();
for (int i = 0; i < len; ++i)
{
atBlock[atBlockPos] = in[inOff + i];
if (++atBlockPos == BLOCK_SIZE)
{
// Hash each block as it fills
gHASHBlock(S_at, atBlock);
atBlockPos = 0;
atLength += BLOCK_SIZE;
}
}
}
private void initCipher()
{
if (atLength > 0)
{
System.arraycopy(S_at, 0, S_atPre, 0, BLOCK_SIZE);
atLengthPre = atLength;
}
// Finish hash for partial AAD block
if (atBlockPos > 0)
{
gHASHPartial(S_atPre, atBlock, 0, atBlockPos);
atLengthPre += atBlockPos;
}
if (atLengthPre > 0)
{
System.arraycopy(S_atPre, 0, S, 0, BLOCK_SIZE);
}
}
public int processByte(byte in, byte[] out, int outOff)
throws DataLengthException
{
checkStatus();
bufBlock[bufOff] = in;
if (++bufOff == bufBlock.length)
{
outputBlock(out, outOff);
return BLOCK_SIZE;
}
return 0;
}
public int processBytes(byte[] in, int inOff, int len, byte[] out, int outOff)
throws DataLengthException
{
checkStatus();
if (in.length < (inOff + len))
{
throw new DataLengthException("Input buffer too short");
}
int resultLen = 0;
for (int i = 0; i < len; ++i)
{
bufBlock[bufOff] = in[inOff + i];
if (++bufOff == bufBlock.length)
{
outputBlock(out, outOff + resultLen);
resultLen += BLOCK_SIZE;
}
}
return resultLen;
}
private void outputBlock(byte[] output, int offset)
{
if (output.length < (offset + BLOCK_SIZE))
{
throw new OutputLengthException("Output buffer too short");
}
if (totalLength == 0)
{
initCipher();
}
gCTRBlock(bufBlock, output, offset);
if (forEncryption)
{
bufOff = 0;
}
else
{
System.arraycopy(bufBlock, BLOCK_SIZE, bufBlock, 0, macSize);
bufOff = macSize;
}
}
public int doFinal(byte[] out, int outOff)
throws IllegalStateException, InvalidCipherTextException
{
checkStatus();
if (totalLength == 0)
{
initCipher();
}
int extra = bufOff;
if (forEncryption)
{
if (out.length < (outOff + extra + macSize))
{
throw new OutputLengthException("Output buffer too short");
}
}
else
{
if (extra < macSize)
{
throw new InvalidCipherTextException("data too short");
}
extra -= macSize;
if (out.length < (outOff + extra))
{
throw new OutputLengthException("Output buffer too short");
}
}
if (extra > 0)
{
gCTRPartial(bufBlock, 0, extra, out, outOff);
}
atLength += atBlockPos;
if (atLength > atLengthPre)
{
/*
* Some AAD was sent after the cipher started. We determine the difference b/w the hash value
* we actually used when the cipher started (S_atPre) and the final hash value calculated (S_at).
* Then we carry this difference forward by multiplying by H^c, where c is the number of (full or
* partial) cipher-text blocks produced, and adjust the current hash.
*/
// Finish hash for partial AAD block
if (atBlockPos > 0)
{
gHASHPartial(S_at, atBlock, 0, atBlockPos);
}
// Find the difference between the AAD hashes
if (atLengthPre > 0)
{
GCMUtil.xor(S_at, S_atPre);
}
// Number of cipher-text blocks produced
long c = ((totalLength * 8) + 127) >>> 7;
// Calculate the adjustment factor
byte[] H_c = new byte[16];
if (exp == null)
{
exp = new Tables1kGCMExponentiator();
exp.init(H);
}
exp.exponentiateX(c, H_c);
// Carry the difference forward
GCMUtil.multiply(S_at, H_c);
// Adjust the current hash
GCMUtil.xor(S, S_at);
}
// Final gHASH
byte[] X = new byte[BLOCK_SIZE];
Pack.longToBigEndian(atLength * 8, X, 0);
Pack.longToBigEndian(totalLength * 8, X, 8);
gHASHBlock(S, X);
// T = MSBt(GCTRk(J0,S))
byte[] tag = new byte[BLOCK_SIZE];
cipher.processBlock(J0, 0, tag, 0);
GCMUtil.xor(tag, S);
int resultLen = extra;
// We place into macBlock our calculated value for T
this.macBlock = new byte[macSize];
System.arraycopy(tag, 0, macBlock, 0, macSize);
if (forEncryption)
{
// Append T to the message
System.arraycopy(macBlock, 0, out, outOff + bufOff, macSize);
resultLen += macSize;
}
else
{
// Retrieve the T value from the message and compare to calculated one
byte[] msgMac = new byte[macSize];
System.arraycopy(bufBlock, extra, msgMac, 0, macSize);
if (!Arrays.constantTimeAreEqual(this.macBlock, msgMac))
{
throw new InvalidCipherTextException("mac check in GCM failed");
}
}
reset(false);
return resultLen;
}
public void reset()
{
reset(true);
}
private void reset(
boolean clearMac)
{
cipher.reset();
// note: we do not reset the nonce.
S = new byte[BLOCK_SIZE];
S_at = new byte[BLOCK_SIZE];
S_atPre = new byte[BLOCK_SIZE];
atBlock = new byte[BLOCK_SIZE];
atBlockPos = 0;
atLength = 0;
atLengthPre = 0;
counter = Arrays.clone(J0);
blocksRemaining = -2;
bufOff = 0;
totalLength = 0;
if (bufBlock != null)
{
Arrays.fill(bufBlock, (byte)0);
}
if (clearMac)
{
macBlock = null;
}
if (forEncryption)
{
initialised = false;
}
else
{
if (initialAssociatedText != null)
{
processAADBytes(initialAssociatedText, 0, initialAssociatedText.length);
}
}
}
private void gCTRBlock(byte[] block, byte[] out, int outOff)
{
byte[] tmp = getNextCounterBlock();
GCMUtil.xor(tmp, block);
System.arraycopy(tmp, 0, out, outOff, BLOCK_SIZE);
gHASHBlock(S, forEncryption ? tmp : block);
totalLength += BLOCK_SIZE;
}
private void gCTRPartial(byte[] buf, int off, int len, byte[] out, int outOff)
{
byte[] tmp = getNextCounterBlock();
GCMUtil.xor(tmp, buf, off, len);
System.arraycopy(tmp, 0, out, outOff, len);
gHASHPartial(S, forEncryption ? tmp : buf, 0, len);
totalLength += len;
}
private void gHASH(byte[] Y, byte[] b, int len)
{
for (int pos = 0; pos < len; pos += BLOCK_SIZE)
{
int num = Math.min(len - pos, BLOCK_SIZE);
gHASHPartial(Y, b, pos, num);
}
}
private void gHASHBlock(byte[] Y, byte[] b)
{
GCMUtil.xor(Y, b);
multiplier.multiplyH(Y);
}
private void gHASHPartial(byte[] Y, byte[] b, int off, int len)
{
GCMUtil.xor(Y, b, off, len);
multiplier.multiplyH(Y);
}
private byte[] getNextCounterBlock()
{
if (blocksRemaining == 0)
{
throw new IllegalStateException("Attempt to process too many blocks");
}
blocksRemaining--;
int c = 1;
c += counter[15] & 0xFF; counter[15] = (byte)c; c >>>= 8;
c += counter[14] & 0xFF; counter[14] = (byte)c; c >>>= 8;
c += counter[13] & 0xFF; counter[13] = (byte)c; c >>>= 8;
c += counter[12] & 0xFF; counter[12] = (byte)c;
byte[] tmp = new byte[BLOCK_SIZE];
// TODO Sure would be nice if ciphers could operate on int[]
cipher.processBlock(counter, 0, tmp, 0);
return tmp;
}
private void checkStatus()
{
if (!initialised)
{
if (forEncryption)
{
throw new IllegalStateException("GCM cipher cannot be reused for encryption");
}
throw new IllegalStateException("GCM cipher needs to be initialised");
}
}
}
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