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* published by the Free Software Foundation. Oracle designates this
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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package com.sun.crypto.provider;
import java.security.InvalidKeyException;
/**
* This class represents ciphers in cipher block chaining (CBC) mode.
*
* <p>This mode is implemented independently of a particular cipher.
* Ciphers to which this mode should apply (e.g., DES) must be
* <i>plugged-in</i> using the constructor.
*
* <p>NOTE: This class does not deal with buffering or padding.
*
* @author Gigi Ankeny
*/
class CipherBlockChaining extends FeedbackCipher {
/*
* random bytes that are initialized with iv
*/
protected byte[] r;
/*
* output buffer
*/
private byte[] k;
// variables for save/restore calls
private byte[] rSave = null;
CipherBlockChaining(SymmetricCipher embeddedCipher) {
super(embeddedCipher);
k = new byte[blockSize];
r = new byte[blockSize];
}
/**
* Gets the name of this feedback mode.
*
* @return the string <code>CBC</code>
*/
String getFeedback() {
return "CBC";
}
/**
* Initializes the cipher in the specified mode with the given key
* and iv.
*
* @param decrypting flag indicating encryption or decryption
* @param algorithm the algorithm name
* @param key the key
* @param iv the iv
*
* @exception InvalidKeyException if the given key is inappropriate for
* initializing this cipher
*/
void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
throws InvalidKeyException {
if ((key == null) || (iv == null) || (iv.length != blockSize)) {
throw new InvalidKeyException("Internal error");
}
this.iv = iv;
reset();
embeddedCipher.init(decrypting, algorithm, key);
}
/**
* Resets the iv to its original value.
* This is used when doFinal is called in the Cipher class, so that the
* cipher can be reused (with its original iv).
*/
void reset() {
System.arraycopy(iv, 0, r, 0, blockSize);
}
/**
* Save the current content of this cipher.
*/
void save() {
if (rSave == null) {
rSave = new byte[blockSize];
}
System.arraycopy(r, 0, rSave, 0, blockSize);
}
/**
* Restores the content of this cipher to the previous saved one.
*/
void restore() {
System.arraycopy(rSave, 0, r, 0, blockSize);
}
/**
* Performs encryption operation.
*
* <p>The input plain text <code>plain</code>, starting at
* <code>plainOffset</code> and ending at
* <code>(plainOffset + len - 1)</code>, is encrypted.
* The result is stored in <code>cipher</code>, starting at
* <code>cipherOffset</code>.
*
* <p>It is the application's responsibility to make sure that
* <code>plainLen</code> is a multiple of the embedded cipher's block size,
* as any excess bytes are ignored.
*
* @param plain the buffer with the input data to be encrypted
* @param plainOffset the offset in <code>plain</code>
* @param plainLen the length of the input data
* @param cipher the buffer for the result
* @param cipherOffset the offset in <code>cipher</code>
*/
void encrypt(byte[] plain, int plainOffset, int plainLen,
byte[] cipher, int cipherOffset)
{
int i;
int endIndex = plainOffset + plainLen;
for (; plainOffset < endIndex;
plainOffset+=blockSize, cipherOffset += blockSize) {
for (i=0; i<blockSize; i++) {
k[i] = (byte)(plain[i+plainOffset] ^ r[i]);
}
embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
}
}
/**
* Performs decryption operation.
*
* <p>The input cipher text <code>cipher</code>, starting at
* <code>cipherOffset</code> and ending at
* <code>(cipherOffset + len - 1)</code>, is decrypted.
* The result is stored in <code>plain</code>, starting at
* <code>plainOffset</code>.
*
* <p>It is the application's responsibility to make sure that
* <code>cipherLen</code> is a multiple of the embedded cipher's block
* size, as any excess bytes are ignored.
*
* <p>It is also the application's responsibility to make sure that
* <code>init</code> has been called before this method is called.
* (This check is omitted here, to avoid double checking.)
*
* @param cipher the buffer with the input data to be decrypted
* @param cipherOffset the offset in <code>cipherOffset</code>
* @param cipherLen the length of the input data
* @param plain the buffer for the result
* @param plainOffset the offset in <code>plain</code>
*
* @exception IllegalBlockSizeException if input data whose length does
* not correspond to the embedded cipher's block size is passed to the
* embedded cipher
*/
void decrypt(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset)
{
int i;
byte[] cipherOrig=null;
int endIndex = cipherOffset + cipherLen;
if (cipher==plain && (cipherOffset >= plainOffset)
&& ((cipherOffset - plainOffset) < blockSize)) {
// Save the original ciphertext blocks, so they can be
// stored in the feedback register "r".
// This is necessary because in this constellation, a
// ciphertext block (or parts of it) will be overridden by
// the plaintext result.
cipherOrig = cipher.clone();
}
for (; cipherOffset < endIndex;
cipherOffset += blockSize, plainOffset += blockSize) {
embeddedCipher.decryptBlock(cipher, cipherOffset, k, 0);
for (i = 0; i < blockSize; i++) {
plain[i+plainOffset] = (byte)(k[i] ^ r[i]);
}
if (cipherOrig==null) {
System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
} else {
System.arraycopy(cipherOrig, cipherOffset, r, 0, blockSize);
}
}
}
}