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/**
* Copyright (C) 2014-2015 Open Whisper Systems
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.whispersystems.libaxolotl.groups;
import org.whispersystems.libaxolotl.DecryptionCallback;
import org.whispersystems.libaxolotl.DuplicateMessageException;
import org.whispersystems.libaxolotl.InvalidKeyIdException;
import org.whispersystems.libaxolotl.InvalidMessageException;
import org.whispersystems.libaxolotl.LegacyMessageException;
import org.whispersystems.libaxolotl.NoSessionException;
import org.whispersystems.libaxolotl.groups.ratchet.SenderChainKey;
import org.whispersystems.libaxolotl.groups.ratchet.SenderMessageKey;
import org.whispersystems.libaxolotl.groups.state.SenderKeyRecord;
import org.whispersystems.libaxolotl.groups.state.SenderKeyState;
import org.whispersystems.libaxolotl.groups.state.SenderKeyStore;
import org.whispersystems.libaxolotl.protocol.SenderKeyMessage;
import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
/**
* The main entry point for axolotl group encrypt/decrypt operations.
*
* Once a session has been established with {@link org.whispersystems.libaxolotl.groups.GroupSessionBuilder}
* and a {@link org.whispersystems.libaxolotl.protocol.SenderKeyDistributionMessage} has been
* distributed to each member of the group, this class can be used for all subsequent encrypt/decrypt
* operations within that session (ie: until group membership changes).
*
* @author Moxie Marlinspike
*/
public class GroupCipher {
static final Object LOCK = new Object();
private final SenderKeyStore senderKeyStore;
private final SenderKeyName senderKeyId;
public GroupCipher(SenderKeyStore senderKeyStore, SenderKeyName senderKeyId) {
this.senderKeyStore = senderKeyStore;
this.senderKeyId = senderKeyId;
}
/**
* Encrypt a message.
*
* @param paddedPlaintext The plaintext message bytes, optionally padded.
* @return Ciphertext.
* @throws NoSessionException
*/
public byte[] encrypt(byte[] paddedPlaintext) throws NoSessionException {
synchronized (LOCK) {
try {
SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId);
SenderKeyState senderKeyState = record.getSenderKeyState();
SenderMessageKey senderKey = senderKeyState.getSenderChainKey().getSenderMessageKey();
byte[] ciphertext = getCipherText(senderKey.getIv(), senderKey.getCipherKey(), paddedPlaintext);
SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyState.getKeyId(),
senderKey.getIteration(),
ciphertext,
senderKeyState.getSigningKeyPrivate());
senderKeyState.setSenderChainKey(senderKeyState.getSenderChainKey().getNext());
senderKeyStore.storeSenderKey(senderKeyId, record);
return senderKeyMessage.serialize();
} catch (InvalidKeyIdException e) {
throw new NoSessionException(e);
}
}
}
/**
* Decrypt a SenderKey group message.
*
* @param senderKeyMessageBytes The received ciphertext.
* @return Plaintext
* @throws LegacyMessageException
* @throws InvalidMessageException
* @throws DuplicateMessageException
*/
public byte[] decrypt(byte[] senderKeyMessageBytes)
throws LegacyMessageException, DuplicateMessageException, InvalidMessageException, NoSessionException
{
return decrypt(senderKeyMessageBytes, new NullDecryptionCallback());
}
/**
* Decrypt a SenderKey group message.
*
* @param senderKeyMessageBytes The received ciphertext.
* @param callback A callback that is triggered after decryption is complete,
* but before the updated session state has been committed to the session
* DB. This allows some implementations to store the committed plaintext
* to a DB first, in case they are concerned with a crash happening between
* the time the session state is updated but before they're able to store
* the plaintext to disk.
* @return Plaintext
* @throws LegacyMessageException
* @throws InvalidMessageException
* @throws DuplicateMessageException
*/
public byte[] decrypt(byte[] senderKeyMessageBytes, DecryptionCallback callback)
throws LegacyMessageException, InvalidMessageException, DuplicateMessageException,
NoSessionException
{
synchronized (LOCK) {
try {
SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId);
if (record.isEmpty()) {
throw new NoSessionException("No sender key for: " + senderKeyId);
}
SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyMessageBytes);
SenderKeyState senderKeyState = record.getSenderKeyState(senderKeyMessage.getKeyId());
senderKeyMessage.verifySignature(senderKeyState.getSigningKeyPublic());
SenderMessageKey senderKey = getSenderKey(senderKeyState, senderKeyMessage.getIteration());
byte[] plaintext = getPlainText(senderKey.getIv(), senderKey.getCipherKey(), senderKeyMessage.getCipherText());
callback.handlePlaintext(plaintext);
senderKeyStore.storeSenderKey(senderKeyId, record);
return plaintext;
} catch (org.whispersystems.libaxolotl.InvalidKeyException | InvalidKeyIdException e) {
throw new InvalidMessageException(e);
}
}
}
private SenderMessageKey getSenderKey(SenderKeyState senderKeyState, int iteration)
throws DuplicateMessageException, InvalidMessageException
{
SenderChainKey senderChainKey = senderKeyState.getSenderChainKey();
if (senderChainKey.getIteration() > iteration) {
if (senderKeyState.hasSenderMessageKey(iteration)) {
return senderKeyState.removeSenderMessageKey(iteration);
} else {
throw new DuplicateMessageException("Received message with old counter: " +
senderChainKey.getIteration() + " , " + iteration);
}
}
if (senderChainKey.getIteration() - iteration > 2000) {
throw new InvalidMessageException("Over 2000 messages into the future!");
}
while (senderChainKey.getIteration() < iteration) {
senderKeyState.addSenderMessageKey(senderChainKey.getSenderMessageKey());
senderChainKey = senderChainKey.getNext();
}
senderKeyState.setSenderChainKey(senderChainKey.getNext());
return senderChainKey.getSenderMessageKey();
}
private byte[] getPlainText(byte[] iv, byte[] key, byte[] ciphertext)
throws InvalidMessageException
{
try {
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), ivParameterSpec);
return cipher.doFinal(ciphertext);
} catch (NoSuchAlgorithmException | NoSuchPaddingException | java.security.InvalidKeyException |
InvalidAlgorithmParameterException e)
{
throw new AssertionError(e);
} catch (IllegalBlockSizeException | BadPaddingException e) {
throw new InvalidMessageException(e);
}
}
private byte[] getCipherText(byte[] iv, byte[] key, byte[] plaintext) {
try {
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"), ivParameterSpec);
return cipher.doFinal(plaintext);
} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidAlgorithmParameterException |
IllegalBlockSizeException | BadPaddingException | java.security.InvalidKeyException e)
{
throw new AssertionError(e);
}
}
private static class NullDecryptionCallback implements DecryptionCallback {
@Override
public void handlePlaintext(byte[] plaintext) {}
}
}
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