/** 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);
}
}
/**
* Continues a multi-part update of the Additional Authentication Data (AAD), using a subset of
* the provided buffer. If this cipher is operating in either GCM or CCM mode, all AAD must be
* supplied before beginning operations on the ciphertext (via the {@code update} and {@code
* doFinal} methods).
*
* <p>NOTE: Given most modes do not accept AAD, default impl for this method throws
* IllegalStateException.
*
* @param src the buffer containing the AAD
* @param offset the offset in {@code src} where the AAD input starts
* @param len the number of AAD bytes
* @throws IllegalStateException if this cipher is in a wrong state (e.g., has not been
* initialized), does not accept AAD, or if operating in either GCM or CCM mode and one of the
* {@code update} methods has already been called for the active encryption/decryption
* operation
* @throws UnsupportedOperationException if this method has not been overridden by an
* implementation
* @since 1.8
*/
void updateAAD(byte[] src, int offset, int len) {
if (aadBuffer != null) {
aadBuffer.write(src, offset, len);
} else {
// update has already been called
throw new IllegalStateException("Update has been called; no more AAD data");
}
}
/**
* Performs decryption operation.
*
* <p>The input cipher text <code>in</code>, starting at <code>inOfs</code> and ending at <code>
* (inOfs + len - 1)</code>, is decrypted. The result is stored in <code>out</code>, starting at
* <code>outOfs</code>.
*
* @param in the buffer with the input data to be decrypted
* @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 decrypt(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) {
// store internally until decryptFinal is called because
// spec mentioned that only return recovered data after tag
// is successfully verified
ibuffer.write(in, inOfs, len);
}
return 0;
}
/**
* 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;
}
