org.thoughtcrime.securesms.crypto.KeyExchangeProcessor.java Source code

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Here is the source code for org.thoughtcrime.securesms.crypto.KeyExchangeProcessor.java

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/** 
 * Copyright (C) 2011 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.thoughtcrime.securesms.crypto;

import java.util.LinkedList;
import java.util.List;

import org.bouncycastle.util.Arrays;
import org.thoughtcrime.securesms.database.LocalKeyRecord;
import org.thoughtcrime.securesms.database.RemoteKeyRecord;
import org.thoughtcrime.securesms.database.SessionRecord;
import org.thoughtcrime.securesms.protocol.Message;
import org.thoughtcrime.securesms.recipients.Recipient;
import org.thoughtcrime.securesms.recipients.Recipients;
import org.thoughtcrime.securesms.service.KeyCachingService;
import org.thoughtcrime.securesms.sms.MessageSender;
import org.thoughtcrime.securesms.util.Conversions;

import android.content.Context;
import android.content.Intent;
import android.util.Log;

/**
 * This class processes key exchange interactions.
 * 
 * @author Moxie Marlinspike
 */

public class KeyExchangeProcessor {

    public static final String SECURITY_UPDATE_EVENT = "org.thoughtcrime.securesms.KEY_EXCHANGE_UPDATE";

    private Context context;
    private Recipient recipient;
    private MasterSecret masterSecret;
    private LocalKeyRecord localKeyRecord;
    private RemoteKeyRecord remoteKeyRecord;
    private SessionRecord sessionRecord;

    public KeyExchangeProcessor(Context context, MasterSecret masterSecret, Recipient recipient) {
        this.context = context;
        this.recipient = recipient;
        this.masterSecret = masterSecret;

        this.remoteKeyRecord = new RemoteKeyRecord(context, recipient);
        this.localKeyRecord = new LocalKeyRecord(context, masterSecret, recipient);
        this.sessionRecord = new SessionRecord(context, masterSecret, recipient);
    }

    public boolean hasCompletedSession() {
        return sessionRecord.getLocalFingerprint() != null;
    }

    public boolean hasSameSessionIdentity(KeyExchangeMessage message) {
        return (this.sessionRecord.getIdentityKey() != null) && (message.getIdentityKey() != null)
                && (this.sessionRecord.getIdentityKey().equals(message.getIdentityKey())
                        && !isRemoteKeyExchangeForExistingSession(message));
    }

    public boolean hasInitiatedSession() {
        return localKeyRecord.getCurrentKeyPair() != null;
    }

    private boolean needsResponseFromUs() {
        return !hasInitiatedSession() || remoteKeyRecord.getCurrentRemoteKey() != null;
    }

    public boolean isRemoteKeyExchangeForExistingSession(KeyExchangeMessage message) {
        return Arrays.areEqual(message.getPublicKey().getFingerprintBytes(), sessionRecord.getRemoteFingerprint());
    }

    public boolean isLocalKeyExchangeForExistingSession(KeyExchangeMessage message) {
        return Arrays.areEqual(message.getPublicKey().getFingerprintBytes(), sessionRecord.getLocalFingerprint());
    }

    public boolean isStale(KeyExchangeMessage message) {
        int responseKeyId = Conversions.highBitsToMedium(message.getPublicKey().getId());

        Log.w("KeyExchangeProcessor", "Key Exchange High ID Bits: " + responseKeyId);

        return responseKeyId != 0 && (localKeyRecord.getCurrentKeyPair() != null
                && localKeyRecord.getCurrentKeyPair().getId() != responseKeyId);
    }

    public boolean processKeyExchangeMessage(KeyExchangeMessage message, long threadId) {
        int initiateKeyId = Conversions.lowBitsToMedium(message.getPublicKey().getId());
        message.getPublicKey().setId(initiateKeyId);

        if (needsResponseFromUs()) {
            List<Recipient> recipients = new LinkedList<Recipient>();
            recipients.add(recipient);

            localKeyRecord = KeyUtil.initializeRecordFor(recipient, context, masterSecret);
            KeyExchangeMessage ourMessage = new KeyExchangeMessage(context, masterSecret,
                    Math.min(Message.SUPPORTED_VERSION, message.getMaxVersion()), localKeyRecord, initiateKeyId);
            Log.w("KeyExchangeProcessor", "Responding with key exchange message fingerprint: "
                    + ourMessage.getPublicKey().getFingerprint());
            Log.w("KeyExchangeProcessor", "Which has a local key record fingerprint: "
                    + localKeyRecord.getCurrentKeyPair().getPublicKey().getFingerprint());
            MessageSender.send(context, masterSecret, new Recipients(recipients), threadId, ourMessage.serialize(),
                    false);
        }

        remoteKeyRecord.setCurrentRemoteKey(message.getPublicKey());
        remoteKeyRecord.setLastRemoteKey(message.getPublicKey());
        remoteKeyRecord.save();

        sessionRecord.setSessionId(localKeyRecord.getCurrentKeyPair().getPublicKey().getFingerprintBytes(),
                remoteKeyRecord.getCurrentRemoteKey().getFingerprintBytes());
        sessionRecord.setIdentityKey(message.getIdentityKey());
        sessionRecord.setSessionVersion(Math.min(Message.SUPPORTED_VERSION, message.getMaxVersion()));

        Log.w("KeyExchangeUtil",
                "Setting session version: " + Math.min(Message.SUPPORTED_VERSION, message.getMaxVersion()));

        sessionRecord.save();

        DecryptingQueue.scheduleRogueMessages(context, masterSecret, recipient);

        Intent intent = new Intent(SECURITY_UPDATE_EVENT);
        intent.putExtra("thread_id", threadId);
        intent.setPackage(context.getPackageName());
        context.sendBroadcast(intent, KeyCachingService.KEY_PERMISSION);

        return true;
    }

}