public byte[] encodePlaintext(short type, byte[] plaintext, int offset, int len) {
int blocksize = encryptCipher.getBlockSize();
int padding_length = blocksize - 1 - ((len + writeMac.getSize()) % blocksize);
boolean isTls =
context.getServerVersion().getFullVersion() >= ProtocolVersion.TLSv10.getFullVersion();
if (isTls) {
// Add a random number of extra blocks worth of padding
int maxExtraPadBlocks = (255 - padding_length) / blocksize;
int actualExtraPadBlocks = chooseExtraPadBlocks(context.getSecureRandom(), maxExtraPadBlocks);
padding_length += actualExtraPadBlocks * blocksize;
}
int totalsize = len + writeMac.getSize() + padding_length + 1;
byte[] outbuf = new byte[totalsize];
System.arraycopy(plaintext, offset, outbuf, 0, len);
byte[] mac = writeMac.calculateMac(type, plaintext, offset, len);
System.arraycopy(mac, 0, outbuf, len, mac.length);
int paddoffset = len + mac.length;
for (int i = 0; i <= padding_length; i++) {
outbuf[i + paddoffset] = (byte) padding_length;
}
for (int i = 0; i < totalsize; i += blocksize) {
encryptCipher.processBlock(outbuf, i, outbuf, i);
}
return outbuf;
}
protected int checkPaddingConstantTime(byte[] buf, int off, int len, int blockSize, int macSize) {
int end = off + len;
byte lastByte = buf[end - 1];
int padlen = lastByte & 0xff;
int totalPad = padlen + 1;
int dummyIndex = 0;
byte padDiff = 0;
boolean isTls =
context.getServerVersion().getFullVersion() >= ProtocolVersion.TLSv10.getFullVersion();
if ((!isTls && totalPad > blockSize) || (macSize + totalPad > len)) {
totalPad = 0;
} else {
int padPos = end - totalPad;
do {
padDiff |= (buf[padPos++] ^ lastByte);
} while (padPos < end);
dummyIndex = totalPad;
if (padDiff != 0) {
totalPad = 0;
}
}
// Run some extra dummy checks so the number of checks is always constant
{
byte[] dummyPad = randomData;
while (dummyIndex < 256) {
padDiff |= (dummyPad[dummyIndex++] ^ lastByte);
}
// Ensure the above loop is not eliminated
dummyPad[0] ^= padDiff;
}
return totalPad;
}
