// Feed the AAD data to GHASH, pad if necessary
void processAAD() {
if (aadBuffer != null && aadBuffer.size() > 0) {
byte[] aad = aadBuffer.toByteArray();
sizeOfAAD = aad.length;
aadBuffer = null;
int lastLen = aad.length % AES_BLOCK_SIZE;
if (lastLen != 0) {
ghashAllToS.update(aad, 0, aad.length - lastLen);
byte[] padded = expandToOneBlock(aad, aad.length - lastLen, lastLen);
ghashAllToS.update(padded);
} else {
ghashAllToS.update(aad);
}
}
}
/** Save the current content of this cipher. */
void save() {
processedSave = processed;
sizeOfAADSave = sizeOfAAD;
aadBufferSave = ((aadBuffer == null || aadBuffer.size() == 0) ? null : aadBuffer.toByteArray());
if (gctrPAndC != null) gctrPAndC.save();
if (ghashAllToS != null) ghashAllToS.save();
if (ibuffer != null) {
ibufferSave = ibuffer.toByteArray();
}
}
/**
* Performs decryption operation for the last time.
*
* <p>NOTE: For cipher feedback modes which does not perform special handling for the last few
* blocks, this is essentially the same as <code>encrypt(...)</code>. Given most modes do not do
* special handling, the default impl for this method is to simply call <code>decrypt(...)</code>.
*
* @param in the input buffer with the data to be decrypted
* @param inOfs the offset in <code>cipher</code>
* @param len the length of the input data
* @param out the buffer for the decryption result
* @param outOfs the offset in <code>plain</code>
* @return the number of bytes placed into the <code>out</code> buffer
*/
int decryptFinal(byte[] in, int inOfs, int len, byte[] out, int outOfs)
throws IllegalBlockSizeException, AEADBadTagException, ShortBufferException {
if (len < tagLenBytes) {
throw new AEADBadTagException("Input too short - need tag");
}
if (out.length - outOfs < ((ibuffer.size() + len) - tagLenBytes)) {
throw new ShortBufferException("Output buffer too small");
}
processAAD();
if (len != 0) {
ibuffer.write(in, inOfs, len);
}
// refresh 'in' to all buffered-up bytes
in = ibuffer.toByteArray();
inOfs = 0;
len = in.length;
ibuffer.reset();
byte[] tag = new byte[tagLenBytes];
// get the trailing tag bytes from 'in'
System.arraycopy(in, len - tagLenBytes, tag, 0, tagLenBytes);
len -= tagLenBytes;
if (len > 0) {
doLastBlock(in, inOfs, len, out, outOfs, false);
}
byte[] lengthBlock = getLengthBlock(sizeOfAAD * 8, processed * 8);
ghashAllToS.update(lengthBlock);
byte[] s = ghashAllToS.digest();
byte[] sOut = new byte[s.length];
GCTR gctrForSToTag = new GCTR(embeddedCipher, this.preCounterBlock);
gctrForSToTag.doFinal(s, 0, s.length, sOut, 0);
for (int i = 0; i < tagLenBytes; i++) {
if (tag[i] != sOut[i]) {
throw new AEADBadTagException("Tag mismatch!");
}
}
return len;
}
/**
* Performs encryption operation for the last time.
*
* @param in the input buffer with the data to be encrypted
* @param inOfs the offset in <code>in</code>
* @param len the length of the input data
* @param out the buffer for the encryption result
* @param outOfs the offset in <code>out</code>
* @return the number of bytes placed into the <code>out</code> buffer
*/
int encryptFinal(byte[] in, int inOfs, int len, byte[] out, int outOfs)
throws IllegalBlockSizeException, ShortBufferException {
if (out.length - outOfs < (len + tagLenBytes)) {
throw new ShortBufferException("Output buffer too small");
}
processAAD();
if (len > 0) {
doLastBlock(in, inOfs, len, out, outOfs, true);
}
byte[] lengthBlock = getLengthBlock(sizeOfAAD * 8, processed * 8);
ghashAllToS.update(lengthBlock);
byte[] s = ghashAllToS.digest();
byte[] sOut = new byte[s.length];
GCTR gctrForSToTag = new GCTR(embeddedCipher, this.preCounterBlock);
gctrForSToTag.doFinal(s, 0, s.length, sOut, 0);
System.arraycopy(sOut, 0, out, (outOfs + len), tagLenBytes);
return (len + tagLenBytes);
}
/**
* Performs encryption operation.
*
* <p>The input plain text <code>in</code>, starting at <code>inOff</code> and ending at <code>
* (inOff + len - 1)</code>, is encrypted. The result is stored in <code>out</code>, starting at
* <code>outOfs</code>.
*
* @param in the buffer with the input data to be encrypted
* @param inOfs the offset in <code>in</code>
* @param len the length of the input data
* @param out the buffer for the result
* @param outOfs the offset in <code>out</code>
* @exception ProviderException if <code>len</code> is not a multiple of the block size
* @return the number of bytes placed into the <code>out</code> buffer
*/
int encrypt(byte[] in, int inOfs, int len, byte[] out, int outOfs) {
if ((len % blockSize) != 0) {
throw new ProviderException("Internal error in input buffering");
}
processAAD();
if (len > 0) {
gctrPAndC.update(in, inOfs, len, out, outOfs);
processed += len;
ghashAllToS.update(out, outOfs, len);
}
return len;
}
/**
* Resets the cipher object to its original state. This is used when doFinal is called in the
* Cipher class, so that the cipher can be reused (with its original key and iv).
*/
void reset() {
if (aadBuffer == null) {
aadBuffer = new ByteArrayOutputStream();
} else {
aadBuffer.reset();
}
if (gctrPAndC != null) gctrPAndC.reset();
if (ghashAllToS != null) ghashAllToS.reset();
processed = 0;
sizeOfAAD = 0;
if (ibuffer != null) {
ibuffer.reset();
}
}
// Utility to process the last block; used by encryptFinal and decryptFinal
void doLastBlock(byte[] in, int inOfs, int len, byte[] out, int outOfs, boolean isEncrypt)
throws IllegalBlockSizeException {
// process data in 'in'
gctrPAndC.doFinal(in, inOfs, len, out, outOfs);
processed += len;
byte[] ct;
int ctOfs;
if (isEncrypt) {
ct = out;
ctOfs = outOfs;
} else {
ct = in;
ctOfs = inOfs;
}
int lastLen = len % AES_BLOCK_SIZE;
if (lastLen != 0) {
ghashAllToS.update(ct, ctOfs, len - lastLen);
byte[] padded = expandToOneBlock(ct, (ctOfs + len - lastLen), lastLen);
ghashAllToS.update(padded);
} else {
ghashAllToS.update(ct, ctOfs, len);
}
}
/** Restores the content of this cipher to the previous saved one. */
void restore() {
processed = processedSave;
sizeOfAAD = sizeOfAADSave;
if (aadBuffer != null) {
aadBuffer.reset();
if (aadBufferSave != null) {
aadBuffer.write(aadBufferSave, 0, aadBufferSave.length);
}
}
if (gctrPAndC != null) gctrPAndC.restore();
if (ghashAllToS != null) ghashAllToS.restore();
if (ibuffer != null) {
ibuffer.reset();
ibuffer.write(ibufferSave, 0, ibufferSave.length);
}
}
private static byte[] getJ0(byte[] iv, byte[] subkeyH) {
byte[] j0;
if (iv.length == 12) { // 96 bits
j0 = expandToOneBlock(iv, 0, iv.length);
j0[AES_BLOCK_SIZE - 1] = 1;
} else {
GHASH g = new GHASH(subkeyH);
int lastLen = iv.length % AES_BLOCK_SIZE;
if (lastLen != 0) {
g.update(iv, 0, iv.length - lastLen);
byte[] padded = expandToOneBlock(iv, iv.length - lastLen, lastLen);
g.update(padded);
} else {
g.update(iv);
}
byte[] lengthBlock = getLengthBlock(iv.length * 8);
g.update(lengthBlock);
j0 = g.digest();
}
return j0;
}