package org.spongycastle.crypto.engines;
import java.security.SecureRandom;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.Digest;
import org.spongycastle.crypto.InvalidCipherTextException;
import org.spongycastle.crypto.Wrapper;
import org.spongycastle.crypto.digests.SHA1Digest;
import org.spongycastle.crypto.modes.CBCBlockCipher;
import org.spongycastle.crypto.params.ParametersWithIV;
import org.spongycastle.crypto.params.ParametersWithRandom;
import org.spongycastle.util.Arrays;
/**
* Wrap keys according to RFC 3217 - RC2 mechanism
*/
public class RC2WrapEngine
implements Wrapper
{
/** Field engine */
private CBCBlockCipher engine;
/** Field param */
private CipherParameters param;
/** Field paramPlusIV */
private ParametersWithIV paramPlusIV;
/** Field iv */
private byte[] iv;
/** Field forWrapping */
private boolean forWrapping;
private SecureRandom sr;
/** Field IV2 */
private static final byte[] IV2 = { (byte) 0x4a, (byte) 0xdd, (byte) 0xa2,
(byte) 0x2c, (byte) 0x79, (byte) 0xe8,
(byte) 0x21, (byte) 0x05 };
//
// checksum digest
//
Digest sha1 = new SHA1Digest();
byte[] digest = new byte[20];
/**
* Method init
*
* @param forWrapping
* @param param
*/
public void init(boolean forWrapping, CipherParameters param)
{
this.forWrapping = forWrapping;
this.engine = new CBCBlockCipher(new RC2Engine());
if (param instanceof ParametersWithRandom)
{
ParametersWithRandom pWithR = (ParametersWithRandom)param;
sr = pWithR.getRandom();
param = pWithR.getParameters();
}
else
{
sr = new SecureRandom();
}
if (param instanceof ParametersWithIV)
{
this.paramPlusIV = (ParametersWithIV)param;
this.iv = this.paramPlusIV.getIV();
this.param = this.paramPlusIV.getParameters();
if (this.forWrapping)
{
if ((this.iv == null) || (this.iv.length != 8))
{
throw new IllegalArgumentException("IV is not 8 octets");
}
}
else
{
throw new IllegalArgumentException(
"You should not supply an IV for unwrapping");
}
}
else
{
this.param = param;
if (this.forWrapping)
{
// Hm, we have no IV but we want to wrap ?!?
// well, then we have to create our own IV.
this.iv = new byte[8];
sr.nextBytes(iv);
this.paramPlusIV = new ParametersWithIV(this.param, this.iv);
}
}
}
/**
* Method getAlgorithmName
*
* @return the algorithm name "RC2".
*/
public String getAlgorithmName()
{
return "RC2";
}
/**
* Method wrap
*
* @param in
* @param inOff
* @param inLen
* @return the wrapped bytes.
*/
public byte[] wrap(byte[] in, int inOff, int inLen)
{
if (!forWrapping)
{
throw new IllegalStateException("Not initialized for wrapping");
}
int length = inLen + 1;
if ((length % 8) != 0)
{
length += 8 - (length % 8);
}
byte keyToBeWrapped[] = new byte[length];
keyToBeWrapped[0] = (byte)inLen;
System.arraycopy(in, inOff, keyToBeWrapped, 1, inLen);
byte[] pad = new byte[keyToBeWrapped.length - inLen - 1];
if (pad.length > 0)
{
sr.nextBytes(pad);
System.arraycopy(pad, 0, keyToBeWrapped, inLen + 1, pad.length);
}
// Compute the CMS Key Checksum, (section 5.6.1), call this CKS.
byte[] CKS = calculateCMSKeyChecksum(keyToBeWrapped);
// Let WKCKS = WK || CKS where || is concatenation.
byte[] WKCKS = new byte[keyToBeWrapped.length + CKS.length];
System.arraycopy(keyToBeWrapped, 0, WKCKS, 0, keyToBeWrapped.length);
System.arraycopy(CKS, 0, WKCKS, keyToBeWrapped.length, CKS.length);
// Encrypt WKCKS in CBC mode using KEK as the key and IV as the
// initialization vector. Call the results TEMP1.
byte TEMP1[] = new byte[WKCKS.length];
System.arraycopy(WKCKS, 0, TEMP1, 0, WKCKS.length);
int noOfBlocks = WKCKS.length / engine.getBlockSize();
int extraBytes = WKCKS.length % engine.getBlockSize();
if (extraBytes != 0)
{
throw new IllegalStateException("Not multiple of block length");
}
engine.init(true, paramPlusIV);
for (int i = 0; i < noOfBlocks; i++)
{
int currentBytePos = i * engine.getBlockSize();
engine.processBlock(TEMP1, currentBytePos, TEMP1, currentBytePos);
}
// Left TEMP2 = IV || TEMP1.
byte[] TEMP2 = new byte[this.iv.length + TEMP1.length];
System.arraycopy(this.iv, 0, TEMP2, 0, this.iv.length);
System.arraycopy(TEMP1, 0, TEMP2, this.iv.length, TEMP1.length);
// Reverse the order of the octets in TEMP2 and call the result TEMP3.
byte[] TEMP3 = new byte[TEMP2.length];
for (int i = 0; i < TEMP2.length; i++)
{
TEMP3[i] = TEMP2[TEMP2.length - (i + 1)];
}
// Encrypt TEMP3 in CBC mode using the KEK and an initialization vector
// of 0x 4a dd a2 2c 79 e8 21 05. The resulting cipher text is the
// desired
// result. It is 40 octets long if a 168 bit key is being wrapped.
ParametersWithIV param2 = new ParametersWithIV(this.param, IV2);
this.engine.init(true, param2);
for (int i = 0; i < noOfBlocks + 1; i++)
{
int currentBytePos = i * engine.getBlockSize();
engine.processBlock(TEMP3, currentBytePos, TEMP3, currentBytePos);
}
return TEMP3;
}
/**
* Method unwrap
*
* @param in
* @param inOff
* @param inLen
* @return the unwrapped bytes.
* @throws InvalidCipherTextException
*/
public byte[] unwrap(byte[] in, int inOff, int inLen)
throws InvalidCipherTextException
{
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[] LCEKPADICV = new byte[TEMP1.length];
System.arraycopy(TEMP1, 0, LCEKPADICV, 0, TEMP1.length);
for (int i = 0; i < (LCEKPADICV.length / engine.getBlockSize()); i++)
{
int currentBytePos = i * engine.getBlockSize();
engine.processBlock(LCEKPADICV, currentBytePos, LCEKPADICV,
currentBytePos);
}
// Decompose LCEKPADICV. CKS is the last 8 octets and WK, the wrapped
// key, are
// those octets before the CKS.
byte[] result = new byte[LCEKPADICV.length - 8];
byte[] CKStoBeVerified = new byte[8];
System.arraycopy(LCEKPADICV, 0, result, 0, LCEKPADICV.length - 8);
System.arraycopy(LCEKPADICV, LCEKPADICV.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");
}
if ((result.length - ((result[0] & 0xff) + 1)) > 7)
{
throw new InvalidCipherTextException("too many pad bytes ("
+ (result.length - ((result[0] & 0xff) + 1)) + ")");
}
// CEK is the wrapped key, now extracted for use in data decryption.
byte[] CEK = new byte[result[0]];
System.arraycopy(result, 1, CEK, 0, CEK.length);
return CEK;
}
/**
* Some key wrap algorithms make use of the Key Checksum defined
* in CMS [CMS-Algorithms]. This is used to provide an integrity
* check value for the key being wrapped. The algorithm is
*
* - Compute the 20 octet SHA-1 hash on the key being wrapped.
* - Use the first 8 octets of this hash as the checksum value.
*
* @param key
* @return
* @throws RuntimeException
* @see http://www.w3.org/TR/xmlenc-core/#sec-CMSKeyChecksum
*/
private byte[] calculateCMSKeyChecksum(
byte[] key)
{
byte[] result = new byte[8];
sha1.update(key, 0, key.length);
sha1.doFinal(digest, 0);
System.arraycopy(digest, 0, result, 0, 8);
return result;
}
/**
* @param key
* @param checksum
* @return
* @see http://www.w3.org/TR/xmlenc-core/#sec-CMSKeyChecksum
*/
private boolean checkCMSKeyChecksum(
byte[] key,
byte[] checksum)
{
return Arrays.constantTimeAreEqual(calculateCMSKeyChecksum(key), checksum);
}
}