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/**
* Copyright (C) 2014 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.protocol;
import com.google.protobuf.ByteString;
import com.google.protobuf.InvalidProtocolBufferException;
import org.whispersystems.libaxolotl.IdentityKey;
import org.whispersystems.libaxolotl.InvalidKeyException;
import org.whispersystems.libaxolotl.InvalidMessageException;
import org.whispersystems.libaxolotl.LegacyMessageException;
import org.whispersystems.libaxolotl.ecc.Curve;
import org.whispersystems.libaxolotl.ecc.ECPublicKey;
import org.whispersystems.libaxolotl.util.ByteUtil;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.ParseException;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
public class WhisperMessage implements CiphertextMessage {
private static final int MAC_LENGTH = 8;
private final int messageVersion;
private final ECPublicKey senderRatchetKey;
private final int counter;
private final int previousCounter;
private final byte[] ciphertext;
private final byte[] serialized;
public WhisperMessage(byte[] serialized) throws InvalidMessageException, LegacyMessageException {
try {
byte[][] messageParts = ByteUtil.split(serialized, 1, serialized.length - 1 - MAC_LENGTH, MAC_LENGTH);
byte version = messageParts[0][0];
byte[] message = messageParts[1];
byte[] mac = messageParts[2];
if (ByteUtil.highBitsToInt(version) <= CiphertextMessage.UNSUPPORTED_VERSION) {
throw new LegacyMessageException("Legacy message: " + ByteUtil.highBitsToInt(version));
}
if (ByteUtil.highBitsToInt(version) > CURRENT_VERSION) {
throw new InvalidMessageException("Unknown version: " + ByteUtil.highBitsToInt(version));
}
WhisperProtos.WhisperMessage whisperMessage = WhisperProtos.WhisperMessage.parseFrom(message);
if (!whisperMessage.hasCiphertext() ||
!whisperMessage.hasCounter() ||
!whisperMessage.hasRatchetKey())
{
throw new InvalidMessageException("Incomplete message.");
}
this.serialized = serialized;
this.senderRatchetKey = Curve.decodePoint(whisperMessage.getRatchetKey().toByteArray(), 0);
this.messageVersion = ByteUtil.highBitsToInt(version);
this.counter = whisperMessage.getCounter();
this.previousCounter = whisperMessage.getPreviousCounter();
this.ciphertext = whisperMessage.getCiphertext().toByteArray();
} catch (InvalidProtocolBufferException | InvalidKeyException | ParseException e) {
throw new InvalidMessageException(e);
}
}
public WhisperMessage(int messageVersion, SecretKeySpec macKey, ECPublicKey senderRatchetKey,
int counter, int previousCounter, byte[] ciphertext,
IdentityKey senderIdentityKey,
IdentityKey receiverIdentityKey)
{
byte[] version = {ByteUtil.intsToByteHighAndLow(messageVersion, CURRENT_VERSION)};
byte[] message = WhisperProtos.WhisperMessage.newBuilder()
.setRatchetKey(ByteString.copyFrom(senderRatchetKey.serialize()))
.setCounter(counter)
.setPreviousCounter(previousCounter)
.setCiphertext(ByteString.copyFrom(ciphertext))
.build().toByteArray();
byte[] mac = getMac(messageVersion, senderIdentityKey, receiverIdentityKey, macKey,
ByteUtil.combine(version, message));
this.serialized = ByteUtil.combine(version, message, mac);
this.senderRatchetKey = senderRatchetKey;
this.counter = counter;
this.previousCounter = previousCounter;
this.ciphertext = ciphertext;
this.messageVersion = messageVersion;
}
public ECPublicKey getSenderRatchetKey() {
return senderRatchetKey;
}
public int getMessageVersion() {
return messageVersion;
}
public int getCounter() {
return counter;
}
public byte[] getBody() {
return ciphertext;
}
public void verifyMac(int messageVersion, IdentityKey senderIdentityKey,
IdentityKey receiverIdentityKey, SecretKeySpec macKey)
throws InvalidMessageException
{
byte[][] parts = ByteUtil.split(serialized, serialized.length - MAC_LENGTH, MAC_LENGTH);
byte[] ourMac = getMac(messageVersion, senderIdentityKey, receiverIdentityKey, macKey, parts[0]);
byte[] theirMac = parts[1];
if (!MessageDigest.isEqual(ourMac, theirMac)) {
throw new InvalidMessageException("Bad Mac!");
}
}
private byte[] getMac(int messageVersion,
IdentityKey senderIdentityKey,
IdentityKey receiverIdentityKey,
SecretKeySpec macKey, byte[] serialized)
{
try {
Mac mac = Mac.getInstance("HmacSHA256");
mac.init(macKey);
if (messageVersion >= 3) {
mac.update(senderIdentityKey.getPublicKey().serialize());
mac.update(receiverIdentityKey.getPublicKey().serialize());
}
byte[] fullMac = mac.doFinal(serialized);
return ByteUtil.trim(fullMac, MAC_LENGTH);
} catch (NoSuchAlgorithmException | java.security.InvalidKeyException e) {
throw new AssertionError(e);
}
}
@Override
public byte[] serialize() {
return serialized;
}
@Override
public int getType() {
return CiphertextMessage.WHISPER_TYPE;
}
public static boolean isLegacy(byte[] message) {
return message != null && message.length >= 1 &&
ByteUtil.highBitsToInt(message[0]) <= CiphertextMessage.UNSUPPORTED_VERSION;
}
}
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