if (forWrapping) {
throw new IllegalStateException("Not set for unwrapping");
}
if (in == null) {
throw new InvalidCipherTextException("Null pointer as ciphertext");
}
if (inLen % engine.getBlockSize() != 0) {
throw new InvalidCipherTextException("Ciphertext not multiple of "
+ engine.getBlockSize());
}
/*
// Check if the length of the cipher text is reasonable given the key
// type. It must be 40 bytes for a 168 bit key and either 32, 40, or
// 48 bytes for a 128, 192, or 256 bit key. If the length is not supported
// or inconsistent with the algorithm for which the key is intended,
// return error.
//
// we do not accept 168 bit keys. it has to be 192 bit.
int lengthA = (estimatedKeyLengthInBit / 8) + 16;
int lengthB = estimatedKeyLengthInBit % 8;
if ((lengthA != keyToBeUnwrapped.length) || (lengthB != 0)) {
throw new XMLSecurityException("empty");
}
*/
// Decrypt the cipher text with TRIPLedeS in CBC mode using the KEK
// and an initialization vector (IV) of 0x4adda22c79e82105. Call the output TEMP3.
ParametersWithIV param2 = new ParametersWithIV(this.param, IV2);
this.engine.init(false, param2);
byte TEMP3[] = new byte[inLen];
System.arraycopy(in, inOff, TEMP3, 0, inLen);
for (int i = 0; i < (TEMP3.length / engine.getBlockSize()); i++) {
int currentBytePos = i * engine.getBlockSize();
engine.processBlock(TEMP3, currentBytePos, TEMP3, currentBytePos);
}
// Reverse the order of the octets in TEMP3 and call the result TEMP2.
byte[] TEMP2 = new byte[TEMP3.length];
for (int i = 0; i < TEMP3.length; i++) {
TEMP2[i] = TEMP3[TEMP3.length - (i + 1)];
}
// Decompose TEMP2 into IV, the first 8 octets, and TEMP1, the remaining octets.
this.iv = new byte[8];
byte[] TEMP1 = new byte[TEMP2.length - 8];
System.arraycopy(TEMP2, 0, this.iv, 0, 8);
System.arraycopy(TEMP2, 8, TEMP1, 0, TEMP2.length - 8);
// Decrypt TEMP1 using TRIPLedeS in CBC mode using the KEK and the IV
// found in the previous step. Call the result WKCKS.
this.paramPlusIV = new ParametersWithIV(this.param, this.iv);
this.engine.init(false, this.paramPlusIV);
byte[] WKCKS = new byte[TEMP1.length];
System.arraycopy(TEMP1, 0, WKCKS, 0, TEMP1.length);
for (int i = 0; i < (WKCKS.length / engine.getBlockSize()); i++) {
int currentBytePos = i * engine.getBlockSize();
engine.processBlock(WKCKS, currentBytePos, WKCKS, currentBytePos);
}
// Decompose WKCKS. CKS is the last 8 octets and WK, the wrapped key, are
// those octets before the CKS.
byte[] result = new byte[WKCKS.length - 8];
byte[] CKStoBeVerified = new byte[8];
System.arraycopy(WKCKS, 0, result, 0, WKCKS.length - 8);
System.arraycopy(WKCKS, WKCKS.length - 8, CKStoBeVerified, 0, 8);
// Calculate a CMS Key Checksum, (section 5.6.1), over the WK and compare
// with the CKS extracted in the above step. If they are not equal, return error.
if (!checkCMSKeyChecksum(result, CKStoBeVerified)) {
throw new InvalidCipherTextException(
"Checksum inside ciphertext is corrupted");
}
// WK is the wrapped key, now extracted for use in data decryption.
return result;