conversations-classic/src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java

package eu.siacs.conversations.crypto.axolotl;

import android.util.Base64;
import android.util.Log;

import org.whispersystems.libaxolotl.AxolotlAddress;
import org.whispersystems.libaxolotl.DuplicateMessageException;
import org.whispersystems.libaxolotl.IdentityKey;
import org.whispersystems.libaxolotl.IdentityKeyPair;
import org.whispersystems.libaxolotl.InvalidKeyException;
import org.whispersystems.libaxolotl.InvalidKeyIdException;
import org.whispersystems.libaxolotl.InvalidMessageException;
import org.whispersystems.libaxolotl.InvalidVersionException;
import org.whispersystems.libaxolotl.LegacyMessageException;
import org.whispersystems.libaxolotl.NoSessionException;
import org.whispersystems.libaxolotl.SessionBuilder;
import org.whispersystems.libaxolotl.SessionCipher;
import org.whispersystems.libaxolotl.UntrustedIdentityException;
import org.whispersystems.libaxolotl.ecc.Curve;
import org.whispersystems.libaxolotl.ecc.ECKeyPair;
import org.whispersystems.libaxolotl.ecc.ECPublicKey;
import org.whispersystems.libaxolotl.protocol.CiphertextMessage;
import org.whispersystems.libaxolotl.protocol.PreKeyWhisperMessage;
import org.whispersystems.libaxolotl.protocol.WhisperMessage;
import org.whispersystems.libaxolotl.state.AxolotlStore;
import org.whispersystems.libaxolotl.state.PreKeyBundle;
import org.whispersystems.libaxolotl.state.PreKeyRecord;
import org.whispersystems.libaxolotl.state.SessionRecord;
import org.whispersystems.libaxolotl.state.SignedPreKeyRecord;
import org.whispersystems.libaxolotl.util.KeyHelper;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Set;

import eu.siacs.conversations.Config;
import eu.siacs.conversations.entities.Account;
import eu.siacs.conversations.entities.Contact;
import eu.siacs.conversations.entities.Conversation;
import eu.siacs.conversations.parser.IqParser;
import eu.siacs.conversations.services.XmppConnectionService;
import eu.siacs.conversations.xml.Element;
import eu.siacs.conversations.xmpp.OnIqPacketReceived;
import eu.siacs.conversations.xmpp.jid.InvalidJidException;
import eu.siacs.conversations.xmpp.jid.Jid;
import eu.siacs.conversations.xmpp.stanzas.IqPacket;

public class AxolotlService {

	public static final String PEP_PREFIX = "eu.siacs.conversations.axolotl";
	public static final String PEP_DEVICE_LIST = PEP_PREFIX + ".devicelist";
	public static final String PEP_PREKEYS = PEP_PREFIX + ".prekeys";
	public static final String PEP_BUNDLE = PEP_PREFIX + ".bundle";

	private final Account account;
	private final XmppConnectionService mXmppConnectionService;
	private final SQLiteAxolotlStore axolotlStore;
	private final SessionMap sessions;
	private final BundleMap bundleCache;
	private int ownDeviceId;

	public static class SQLiteAxolotlStore implements AxolotlStore {

		public static final String PREKEY_TABLENAME = "prekeys";
		public static final String SIGNED_PREKEY_TABLENAME = "signed_prekeys";
		public static final String SESSION_TABLENAME = "sessions";
		public static final String ACCOUNT = "account";
		public static final String DEVICE_ID = "device_id";
		public static final String ID = "id";
		public static final String KEY = "key";
		public static final String NAME = "name";
		public static final String TRUSTED = "trusted";

		public static final String JSONKEY_IDENTITY_KEY_PAIR = "axolotl_key";
		public static final String JSONKEY_REGISTRATION_ID = "axolotl_reg_id";
		public static final String JSONKEY_CURRENT_PREKEY_ID = "axolotl_cur_prekey_id";

		private final Account account;
		private final XmppConnectionService mXmppConnectionService;

		private final IdentityKeyPair identityKeyPair;
		private final int localRegistrationId;
		private int currentPreKeyId = 0;


		private static IdentityKeyPair generateIdentityKeyPair() {
			Log.d(Config.LOGTAG, "Generating axolotl IdentityKeyPair...");
			ECKeyPair identityKeyPairKeys = Curve.generateKeyPair();
			IdentityKeyPair ownKey = new IdentityKeyPair(new IdentityKey(identityKeyPairKeys.getPublicKey()),
					identityKeyPairKeys.getPrivateKey());
			return ownKey;
		}

		private static int generateRegistrationId() {
			Log.d(Config.LOGTAG, "Generating axolotl registration ID...");
			int reg_id = KeyHelper.generateRegistrationId(false);
			return reg_id;
		}

		public SQLiteAxolotlStore(Account account, XmppConnectionService service) {
			this.account = account;
			this.mXmppConnectionService = service;
			this.identityKeyPair = loadIdentityKeyPair();
			this.localRegistrationId = loadRegistrationId();
			this.currentPreKeyId = loadCurrentPreKeyId();
			for( SignedPreKeyRecord record:loadSignedPreKeys()) {
				Log.d(Config.LOGTAG, "Got Axolotl signed prekey record:" + record.getId());
			}
		}

		public int getCurrentPreKeyId() {
			return currentPreKeyId;
		}

		// --------------------------------------
		// IdentityKeyStore
		// --------------------------------------

		private IdentityKeyPair loadIdentityKeyPair() {
			String serializedKey = this.account.getKey(JSONKEY_IDENTITY_KEY_PAIR);
			IdentityKeyPair ownKey;
			if( serializedKey != null ) {
				try {
					ownKey = new IdentityKeyPair(Base64.decode(serializedKey,Base64.DEFAULT));
					return ownKey;
				} catch (InvalidKeyException e) {
					Log.d(Config.LOGTAG, "Invalid key stored for account " + account.getJid() + ": " + e.getMessage());
//                    return null;
				}
			} //else {
				Log.d(Config.LOGTAG, "Could not retrieve axolotl key for account " + account.getJid());
				ownKey = generateIdentityKeyPair();
				boolean success = this.account.setKey(JSONKEY_IDENTITY_KEY_PAIR, Base64.encodeToString(ownKey.serialize(), Base64.DEFAULT));
				if(success) {
					mXmppConnectionService.databaseBackend.updateAccount(account);
				} else {
					Log.e(Config.LOGTAG, "Failed to write new key to the database!");
				}
			//}
			return ownKey;
		}

		private int loadRegistrationId() {
			String regIdString = this.account.getKey(JSONKEY_REGISTRATION_ID);
			int reg_id;
			if (regIdString != null) {
				reg_id = Integer.valueOf(regIdString);
			} else {
				Log.d(Config.LOGTAG, "Could not retrieve axolotl registration id for account " + account.getJid());
				reg_id = generateRegistrationId();
				boolean success = this.account.setKey(JSONKEY_REGISTRATION_ID,""+reg_id);
				if(success) {
					mXmppConnectionService.databaseBackend.updateAccount(account);
				} else {
					Log.e(Config.LOGTAG, "Failed to write new key to the database!");
				}
			}
			return reg_id;
		}

		private int loadCurrentPreKeyId() {
			String regIdString = this.account.getKey(JSONKEY_CURRENT_PREKEY_ID);
			int reg_id;
			if (regIdString != null) {
				reg_id = Integer.valueOf(regIdString);
			} else {
				Log.d(Config.LOGTAG, "Could not retrieve current prekey id for account " + account.getJid());
				reg_id = 0;
			}
			return reg_id;
		}


		/**
		 * Get the local client's identity key pair.
		 *
		 * @return The local client's persistent identity key pair.
		 */
		@Override
		public IdentityKeyPair getIdentityKeyPair() {
			return identityKeyPair;
		}

		/**
		 * Return the local client's registration ID.
		 * <p/>
		 * Clients should maintain a registration ID, a random number
		 * between 1 and 16380 that's generated once at install time.
		 *
		 * @return the local client's registration ID.
		 */
		@Override
		public int getLocalRegistrationId() {
			return localRegistrationId;
		}

		/**
		 * Save a remote client's identity key
		 * <p/>
		 * Store a remote client's identity key as trusted.
		 *
		 * @param name        The name of the remote client.
		 * @param identityKey The remote client's identity key.
		 */
		@Override
		public void saveIdentity(String name, IdentityKey identityKey) {
			try {
				Jid contactJid = Jid.fromString(name);
				Conversation conversation = this.mXmppConnectionService.find(this.account, contactJid);
				if (conversation != null) {
					conversation.getContact().addAxolotlIdentityKey(identityKey);
					mXmppConnectionService.updateConversationUi();
					mXmppConnectionService.syncRosterToDisk(conversation.getAccount());
				}
			} catch (final InvalidJidException e) {
				Log.e(Config.LOGTAG, "Failed to save identityKey for contact name " + name + ": " + e.toString());
			}
		}

		/**
		 * Verify a remote client's identity key.
		 * <p/>
		 * Determine whether a remote client's identity is trusted.  Convention is
		 * that the TextSecure protocol is 'trust on first use.'  This means that
		 * an identity key is considered 'trusted' if there is no entry for the recipient
		 * in the local store, or if it matches the saved key for a recipient in the local
		 * store.  Only if it mismatches an entry in the local store is it considered
		 * 'untrusted.'
		 *
		 * @param name        The name of the remote client.
		 * @param identityKey The identity key to verify.
		 * @return true if trusted, false if untrusted.
		 */
		@Override
		public boolean isTrustedIdentity(String name, IdentityKey identityKey) {
			try {
				Jid contactJid = Jid.fromString(name);
				Conversation conversation = this.mXmppConnectionService.find(this.account, contactJid);
				if (conversation != null) {
					List<IdentityKey> trustedKeys = conversation.getContact().getAxolotlIdentityKeys();
					return trustedKeys.isEmpty() || trustedKeys.contains(identityKey);
				} else {
					return false;
				}
			} catch (final InvalidJidException e) {
				Log.e(Config.LOGTAG, "Failed to save identityKey for contact name" + name + ": " + e.toString());
				return false;
			}
		}

		// --------------------------------------
		// SessionStore
		// --------------------------------------

		/**
		 * Returns a copy of the {@link SessionRecord} corresponding to the recipientId + deviceId tuple,
		 * or a new SessionRecord if one does not currently exist.
		 * <p/>
		 * It is important that implementations return a copy of the current durable information.  The
		 * returned SessionRecord may be modified, but those changes should not have an effect on the
		 * durable session state (what is returned by subsequent calls to this method) without the
		 * store method being called here first.
		 *
		 * @param address The name and device ID of the remote client.
		 * @return a copy of the SessionRecord corresponding to the recipientId + deviceId tuple, or
		 * a new SessionRecord if one does not currently exist.
		 */
		@Override
		public SessionRecord loadSession(AxolotlAddress address) {
			SessionRecord session = mXmppConnectionService.databaseBackend.loadSession(this.account, address);
			return (session!=null)?session:new SessionRecord();
		}

		/**
		 * Returns all known devices with active sessions for a recipient
		 *
		 * @param name the name of the client.
		 * @return all known sub-devices with active sessions.
		 */
		@Override
		public List<Integer> getSubDeviceSessions(String name) {
			return mXmppConnectionService.databaseBackend.getSubDeviceSessions(account,
					new AxolotlAddress(name,0));
		}

		/**
		 * Commit to storage the {@link SessionRecord} for a given recipientId + deviceId tuple.
		 *
		 * @param address the address of the remote client.
		 * @param record  the current SessionRecord for the remote client.
		 */
		@Override
		public void storeSession(AxolotlAddress address, SessionRecord record) {
			mXmppConnectionService.databaseBackend.storeSession(account, address, record);
		}

		/**
		 * Determine whether there is a committed {@link SessionRecord} for a recipientId + deviceId tuple.
		 *
		 * @param address the address of the remote client.
		 * @return true if a {@link SessionRecord} exists, false otherwise.
		 */
		@Override
		public boolean containsSession(AxolotlAddress address) {
			return mXmppConnectionService.databaseBackend.containsSession(account, address);
		}

		/**
		 * Remove a {@link SessionRecord} for a recipientId + deviceId tuple.
		 *
		 * @param address the address of the remote client.
		 */
		@Override
		public void deleteSession(AxolotlAddress address) {
			mXmppConnectionService.databaseBackend.deleteSession(account, address);
		}

		/**
		 * Remove the {@link SessionRecord}s corresponding to all devices of a recipientId.
		 *
		 * @param name the name of the remote client.
		 */
		@Override
		public void deleteAllSessions(String name) {
			mXmppConnectionService.databaseBackend.deleteAllSessions(account,
					new AxolotlAddress(name, 0));
		}

		public boolean isTrustedSession(AxolotlAddress address) {
			return mXmppConnectionService.databaseBackend.isTrustedSession(this.account, address);
		}

		public void setTrustedSession(AxolotlAddress address, boolean trusted) {
			mXmppConnectionService.databaseBackend.setTrustedSession(this.account, address,trusted);
		}

		// --------------------------------------
		// PreKeyStore
		// --------------------------------------

		/**
		 * Load a local PreKeyRecord.
		 *
		 * @param preKeyId the ID of the local PreKeyRecord.
		 * @return the corresponding PreKeyRecord.
		 * @throws InvalidKeyIdException when there is no corresponding PreKeyRecord.
		 */
		@Override
		public PreKeyRecord loadPreKey(int preKeyId) throws InvalidKeyIdException {
			PreKeyRecord record = mXmppConnectionService.databaseBackend.loadPreKey(account, preKeyId);
			if(record == null) {
				throw new InvalidKeyIdException("No such PreKeyRecord: " + preKeyId);
			}
			return record;
		}

		/**
		 * Store a local PreKeyRecord.
		 *
		 * @param preKeyId the ID of the PreKeyRecord to store.
		 * @param record   the PreKeyRecord.
		 */
		@Override
		public void storePreKey(int preKeyId, PreKeyRecord record) {
			mXmppConnectionService.databaseBackend.storePreKey(account, record);
			currentPreKeyId = preKeyId;
			boolean success = this.account.setKey(JSONKEY_CURRENT_PREKEY_ID,Integer.toString(preKeyId));
			if(success) {
				mXmppConnectionService.databaseBackend.updateAccount(account);
			} else {
				Log.e(Config.LOGTAG, "Failed to write new prekey id to the database!");
			}
		}

		/**
		 * @param preKeyId A PreKeyRecord ID.
		 * @return true if the store has a record for the preKeyId, otherwise false.
		 */
		@Override
		public boolean containsPreKey(int preKeyId) {
			return mXmppConnectionService.databaseBackend.containsPreKey(account, preKeyId);
		}

		/**
		 * Delete a PreKeyRecord from local storage.
		 *
		 * @param preKeyId The ID of the PreKeyRecord to remove.
		 */
		@Override
		public void removePreKey(int preKeyId) {
			mXmppConnectionService.databaseBackend.deletePreKey(account, preKeyId);
		}

		// --------------------------------------
		// SignedPreKeyStore
		// --------------------------------------

		/**
		 * Load a local SignedPreKeyRecord.
		 *
		 * @param signedPreKeyId the ID of the local SignedPreKeyRecord.
		 * @return the corresponding SignedPreKeyRecord.
		 * @throws InvalidKeyIdException when there is no corresponding SignedPreKeyRecord.
		 */
		@Override
		public SignedPreKeyRecord loadSignedPreKey(int signedPreKeyId) throws InvalidKeyIdException {
			SignedPreKeyRecord record = mXmppConnectionService.databaseBackend.loadSignedPreKey(account, signedPreKeyId);
			if(record == null) {
				throw new InvalidKeyIdException("No such SignedPreKeyRecord: " + signedPreKeyId);
			}
			return record;
		}

		/**
		 * Load all local SignedPreKeyRecords.
		 *
		 * @return All stored SignedPreKeyRecords.
		 */
		@Override
		public List<SignedPreKeyRecord> loadSignedPreKeys() {
			return mXmppConnectionService.databaseBackend.loadSignedPreKeys(account);
		}

		/**
		 * Store a local SignedPreKeyRecord.
		 *
		 * @param signedPreKeyId the ID of the SignedPreKeyRecord to store.
		 * @param record         the SignedPreKeyRecord.
		 */
		@Override
		public void storeSignedPreKey(int signedPreKeyId, SignedPreKeyRecord record) {
			mXmppConnectionService.databaseBackend.storeSignedPreKey(account, record);
		}

		/**
		 * @param signedPreKeyId A SignedPreKeyRecord ID.
		 * @return true if the store has a record for the signedPreKeyId, otherwise false.
		 */
		@Override
		public boolean containsSignedPreKey(int signedPreKeyId) {
			return mXmppConnectionService.databaseBackend.containsSignedPreKey(account, signedPreKeyId);
		}

		/**
		 * Delete a SignedPreKeyRecord from local storage.
		 *
		 * @param signedPreKeyId The ID of the SignedPreKeyRecord to remove.
		 */
		@Override
		public void removeSignedPreKey(int signedPreKeyId) {
			mXmppConnectionService.databaseBackend.deleteSignedPreKey(account, signedPreKeyId);
		}
	}

	public static class XmppAxolotlSession {
		private SessionCipher cipher;
		private boolean isTrusted = false;
		private SQLiteAxolotlStore sqLiteAxolotlStore;
		private AxolotlAddress remoteAddress;

		public XmppAxolotlSession(SQLiteAxolotlStore store, AxolotlAddress remoteAddress) {
			this.cipher = new SessionCipher(store, remoteAddress);
			this.remoteAddress = remoteAddress;
			this.sqLiteAxolotlStore = store;
			this.isTrusted = sqLiteAxolotlStore.isTrustedSession(remoteAddress);
		}

		public void trust() {
			sqLiteAxolotlStore.setTrustedSession(remoteAddress, true);
			this.isTrusted = true;
		}

		public boolean isTrusted() {
			return this.isTrusted;
		}

		public byte[] processReceiving(XmppAxolotlMessage.XmppAxolotlMessageHeader incomingHeader) {
			byte[] plaintext = null;
			try {
				try {
					PreKeyWhisperMessage message = new PreKeyWhisperMessage(incomingHeader.getContents());
					Log.d(Config.LOGTAG,"PreKeyWhisperMessage ID:" + message.getSignedPreKeyId() + "/" + message.getPreKeyId());
					plaintext = cipher.decrypt(message);
				} catch (InvalidMessageException|InvalidVersionException e) {
					WhisperMessage message = new WhisperMessage(incomingHeader.getContents());
					plaintext = cipher.decrypt(message);
				} catch (InvalidKeyException|InvalidKeyIdException| UntrustedIdentityException e) {
					Log.d(Config.LOGTAG, "Error decrypting axolotl header: " + e.getMessage());
				}
			} catch (LegacyMessageException|InvalidMessageException e) {
				Log.d(Config.LOGTAG, "Error decrypting axolotl header: " + e.getMessage());
			} catch (DuplicateMessageException|NoSessionException e) {
				Log.d(Config.LOGTAG, "Error decrypting axolotl header: " + e.getMessage());
			}
			return plaintext;
		}

		public XmppAxolotlMessage.XmppAxolotlMessageHeader processSending(byte[] outgoingMessage) {
			CiphertextMessage ciphertextMessage = cipher.encrypt(outgoingMessage);
			XmppAxolotlMessage.XmppAxolotlMessageHeader header =
					new XmppAxolotlMessage.XmppAxolotlMessageHeader(remoteAddress.getDeviceId(),
							ciphertextMessage.serialize());
			return header;
		}
	}

	private static class AxolotlAddressMap<T> {
		protected Map<String, Map<Integer,T>> map;
		protected final Object MAP_LOCK = new Object();

		public AxolotlAddressMap() {
			this.map = new HashMap<>();
		}

		public void put(AxolotlAddress address, T value) {
			synchronized (MAP_LOCK) {
				Map<Integer, T> devices = map.get(address.getName());
				if (devices == null) {
					devices = new HashMap<>();
					map.put(address.getName(), devices);
				}
				devices.put(address.getDeviceId(), value);
			}
		}

		public T get(AxolotlAddress address) {
			synchronized (MAP_LOCK) {
				Map<Integer, T> devices = map.get(address.getName());
				if(devices == null) {
					return null;
				}
				return devices.get(address.getDeviceId());
			}
		}

		public Map<Integer, T> getAll(AxolotlAddress address) {
			synchronized (MAP_LOCK) {
				Map<Integer, T> devices = map.get(address.getName());
				if(devices == null) {
					return new HashMap<>();
				}
				return devices;
			}
		}

		public boolean hasAny(AxolotlAddress address) {
			synchronized (MAP_LOCK) {
				Map<Integer, T> devices = map.get(address.getName());
				return devices != null && !devices.isEmpty();
			}
		}


	}

	private static class SessionMap extends AxolotlAddressMap<XmppAxolotlSession> {

		public SessionMap(SQLiteAxolotlStore store, Account account) {
			super();
			this.fillMap(store, account);
		}

		private void fillMap(SQLiteAxolotlStore store, Account account) {
			for(Contact contact:account.getRoster().getContacts()){
				Jid bareJid = contact.getJid().toBareJid();
				if(bareJid == null) {
					continue; // FIXME: handle this?
				}
				String address = bareJid.toString();
				List<Integer> deviceIDs = store.getSubDeviceSessions(address);
				for(Integer deviceId:deviceIDs) {
					AxolotlAddress axolotlAddress = new AxolotlAddress(address, deviceId);
					this.put(axolotlAddress, new XmppAxolotlSession(store, axolotlAddress));
				}
			}
		}

	}

	private static class BundleMap extends AxolotlAddressMap<PreKeyBundle> {

	}

	public AxolotlService(Account account, XmppConnectionService connectionService) {
		this.mXmppConnectionService = connectionService;
		this.account = account;
		this.axolotlStore = new SQLiteAxolotlStore(this.account, this.mXmppConnectionService);
		this.sessions = new SessionMap(axolotlStore, account);
		this.bundleCache = new BundleMap();
		this.ownDeviceId = axolotlStore.getLocalRegistrationId();
	}

	public void trustSession(AxolotlAddress counterpart) {
		XmppAxolotlSession session = sessions.get(counterpart);
		if(session != null) {
			session.trust();
		}
	}

	public boolean isTrustedSession(AxolotlAddress counterpart) {
		XmppAxolotlSession session = sessions.get(counterpart);
		return session != null && session.isTrusted();
	}

	private AxolotlAddress getAddressForJid(Jid jid) {
		return new AxolotlAddress(jid.toString(), 0);
	}

	private Set<XmppAxolotlSession> findOwnSessions() {
		AxolotlAddress ownAddress = getAddressForJid(account.getJid());
		Set<XmppAxolotlSession> ownDeviceSessions = new HashSet<>(this.sessions.getAll(ownAddress).values());
		return ownDeviceSessions;
	}

	private Set<XmppAxolotlSession> findSessionsforContact(Contact contact) {
		AxolotlAddress contactAddress = getAddressForJid(contact.getJid());
		Set<XmppAxolotlSession> sessions = new HashSet<>(this.sessions.getAll(contactAddress).values());
		return sessions;
	}

	private boolean hasAny(Contact contact) {
		AxolotlAddress contactAddress = getAddressForJid(contact.getJid());
		return sessions.hasAny(contactAddress);
	}

	public int getOwnDeviceId() {
		return ownDeviceId;
	}

	public void fetchBundleIfNeeded(final Contact contact, final Integer deviceId) {
		final AxolotlAddress address = new AxolotlAddress(contact.getJid().toString(), deviceId);
		if (sessions.get(address) != null) {
			return;
		}

		synchronized (bundleCache) {
			PreKeyBundle bundle = bundleCache.get(address);
			if (bundle == null) {
				bundle = new PreKeyBundle(0, deviceId, 0, null, 0, null, null, null);
				bundleCache.put(address, bundle);
			}

			if(bundle.getPreKey() == null) {
				Log.d(Config.LOGTAG, "No preKey in cache, fetching...");
				IqPacket prekeysPacket = mXmppConnectionService.getIqGenerator().retrievePreKeysForDevice(contact.getJid(), deviceId);
				mXmppConnectionService.sendIqPacket(account, prekeysPacket, new OnIqPacketReceived() {
					@Override
					public void onIqPacketReceived(Account account, IqPacket packet) {
						synchronized (bundleCache) {
							Log.d(Config.LOGTAG, "Received preKey IQ packet, processing...");
							final IqParser parser = mXmppConnectionService.getIqParser();
							final PreKeyBundle bundle = bundleCache.get(address);
							final List<PreKeyBundle> preKeyBundleList = parser.preKeys(packet);
							if (preKeyBundleList.isEmpty()) {
								Log.d(Config.LOGTAG, "preKey IQ packet invalid: " + packet);
								return;
							}
							Random random = new Random();
							final PreKeyBundle newBundle = preKeyBundleList.get(random.nextInt(preKeyBundleList.size()));
							if (bundle == null || newBundle == null) {
								//should never happen
								return;
							}

							final PreKeyBundle mergedBundle = new PreKeyBundle(bundle.getRegistrationId(),
									bundle.getDeviceId(), newBundle.getPreKeyId(), newBundle.getPreKey(),
									bundle.getSignedPreKeyId(), bundle.getSignedPreKey(),
									bundle.getSignedPreKeySignature(), bundle.getIdentityKey());

							bundleCache.put(address, mergedBundle);
						}
					}
				});
			}
			if(bundle.getIdentityKey() == null) {
				Log.d(Config.LOGTAG, "No bundle in cache, fetching...");
				IqPacket bundlePacket = mXmppConnectionService.getIqGenerator().retrieveBundleForDevice(contact.getJid(), deviceId);
				mXmppConnectionService.sendIqPacket(account, bundlePacket, new OnIqPacketReceived() {
					@Override
					public void onIqPacketReceived(Account account, IqPacket packet) {
						synchronized (bundleCache) {
							Log.d(Config.LOGTAG, "Received bundle IQ packet, processing...");
							final IqParser parser = mXmppConnectionService.getIqParser();
							final PreKeyBundle bundle = bundleCache.get(address);
							final PreKeyBundle newBundle = parser.bundle(packet);
							if( bundle == null || newBundle == null ) {
								Log.d(Config.LOGTAG, "bundle IQ packet invalid: " + packet);
								//should never happen
								return;
							}

							final PreKeyBundle mergedBundle = new PreKeyBundle(bundle.getRegistrationId(),
									bundle.getDeviceId(), bundle.getPreKeyId(), bundle.getPreKey(),
									newBundle.getSignedPreKeyId(), newBundle.getSignedPreKey(),
									newBundle.getSignedPreKeySignature(), newBundle.getIdentityKey());

							axolotlStore.saveIdentity(contact.getJid().toBareJid().toString(), newBundle.getIdentityKey());
							bundleCache.put(address, mergedBundle);
						}
					}
				});
			}
		}
	}

	public void publishOwnDeviceIdIfNeeded() {
		IqPacket packet = mXmppConnectionService.getIqGenerator().retrieveDeviceIds(account.getJid().toBareJid());
		mXmppConnectionService.sendIqPacket(account, packet, new OnIqPacketReceived() {
			@Override
			public void onIqPacketReceived(Account account, IqPacket packet) {
				Element item = mXmppConnectionService.getIqParser().getItem(packet);
				List<Integer> deviceIds = mXmppConnectionService.getIqParser().deviceIds(item);
				if(deviceIds == null) {
					deviceIds = new ArrayList<>();
				}
				if(!deviceIds.contains(getOwnDeviceId())) {
					Log.d(Config.LOGTAG, "Own device " + getOwnDeviceId() + " not in PEP devicelist. Publishing...");
					deviceIds.add(getOwnDeviceId());
					IqPacket publish = mXmppConnectionService.getIqGenerator().publishDeviceIds(deviceIds);
					mXmppConnectionService.sendIqPacket(account, publish, new OnIqPacketReceived() {
						@Override
						public void onIqPacketReceived(Account account, IqPacket packet) {
							// TODO: implement this!
						}
					});
				}
			}
		});
	}

	public void publishBundleIfNeeded() {
		IqPacket packet = mXmppConnectionService.getIqGenerator().retrieveBundleForDevice(account.getJid().toBareJid(), ownDeviceId);
		mXmppConnectionService.sendIqPacket(account, packet, new OnIqPacketReceived() {
			@Override
			public void onIqPacketReceived(Account account, IqPacket packet) {
				PreKeyBundle bundle = mXmppConnectionService.getIqParser().bundle(packet);
				if(bundle == null) {
					Log.d(Config.LOGTAG, "Bundle " + getOwnDeviceId() + " not in PEP. Publishing...");
					int numSignedPreKeys = axolotlStore.loadSignedPreKeys().size();
					try {
						SignedPreKeyRecord signedPreKeyRecord = KeyHelper.generateSignedPreKey(
								axolotlStore.getIdentityKeyPair(), numSignedPreKeys + 1);
						axolotlStore.storeSignedPreKey(signedPreKeyRecord.getId(), signedPreKeyRecord);
						IqPacket publish = mXmppConnectionService.getIqGenerator().publishBundle(
								signedPreKeyRecord, axolotlStore.getIdentityKeyPair().getPublicKey(),
								ownDeviceId);
						mXmppConnectionService.sendIqPacket(account, publish, new OnIqPacketReceived() {
							@Override
							public void onIqPacketReceived(Account account, IqPacket packet) {
								// TODO: implement this!
								Log.d(Config.LOGTAG, "Published bundle, got: " + packet);
							}
						});
					} catch (InvalidKeyException e) {
						Log.e(Config.LOGTAG, "Failed to publish bundle " + getOwnDeviceId() + ", reason: " + e.getMessage());
					}
				}
			}
		});
	}

	public void publishPreKeysIfNeeded() {
		IqPacket packet = mXmppConnectionService.getIqGenerator().retrievePreKeysForDevice(account.getJid().toBareJid(), ownDeviceId);
		mXmppConnectionService.sendIqPacket(account, packet, new OnIqPacketReceived() {
			@Override
			public void onIqPacketReceived(Account account, IqPacket packet) {
				Map<Integer, ECPublicKey> keys = mXmppConnectionService.getIqParser().preKeyPublics(packet);
				if(keys == null || keys.isEmpty()) {
					Log.d(Config.LOGTAG, "Prekeys " + getOwnDeviceId() + " not in PEP. Publishing...");
					List<PreKeyRecord> preKeyRecords = KeyHelper.generatePreKeys(
							axolotlStore.getCurrentPreKeyId(), 100);
					for(PreKeyRecord record : preKeyRecords) {
						axolotlStore.storePreKey(record.getId(), record);
					}
					IqPacket publish = mXmppConnectionService.getIqGenerator().publishPreKeys(
							preKeyRecords, ownDeviceId);

					mXmppConnectionService.sendIqPacket(account, publish, new OnIqPacketReceived() {
						@Override
						public void onIqPacketReceived(Account account, IqPacket packet) {
							Log.d(Config.LOGTAG, "Published prekeys, got: " + packet);
							// TODO: implement this!
						}
					});
				}
			}
		});
	}


	public boolean isContactAxolotlCapable(Contact contact) {
		AxolotlAddress address = new AxolotlAddress(contact.getJid().toBareJid().toString(), 0);
		return sessions.hasAny(address) || bundleCache.hasAny(address);
	}

	public void initiateSynchronousSession(Contact contact) {

	}

	private void createSessionsIfNeeded(Contact contact) throws NoSessionsCreatedException {
		Log.d(Config.LOGTAG, "Creating axolotl sessions if needed...");
		AxolotlAddress address = new AxolotlAddress(contact.getJid().toBareJid().toString(), 0);
		for(Integer deviceId: bundleCache.getAll(address).keySet()) {
			Log.d(Config.LOGTAG, "Processing device ID: " + deviceId);
			AxolotlAddress remoteAddress = new AxolotlAddress(contact.getJid().toBareJid().toString(), deviceId);
			if(sessions.get(remoteAddress) == null) {
				Log.d(Config.LOGTAG, "Building new sesstion for " + deviceId);
				SessionBuilder builder = new SessionBuilder(this.axolotlStore, remoteAddress);
				try {
					builder.process(bundleCache.get(remoteAddress));
					XmppAxolotlSession session = new XmppAxolotlSession(this.axolotlStore, remoteAddress);
					sessions.put(remoteAddress, session);
				} catch (InvalidKeyException e) {
					Log.d(Config.LOGTAG, "Error building session for " + deviceId+ ": InvalidKeyException, " +e.getMessage());
				} catch (UntrustedIdentityException e) {
					Log.d(Config.LOGTAG, "Error building session for " + deviceId+ ": UntrustedIdentityException, " +e.getMessage());
				}
			} else {
				Log.d(Config.LOGTAG, "Already have session for " + deviceId);
			}
		}
		if(!this.hasAny(contact)) {
			Log.e(Config.LOGTAG, "No Axolotl sessions available!");
			throw new NoSessionsCreatedException(); // FIXME: proper error handling
		}
	}

	public XmppAxolotlMessage processSending(Contact contact, String outgoingMessage) throws NoSessionsCreatedException {
		XmppAxolotlMessage message = new XmppAxolotlMessage(contact, ownDeviceId, outgoingMessage);
		createSessionsIfNeeded(contact);
		Log.d(Config.LOGTAG, "Building axolotl foreign headers...");

		for(XmppAxolotlSession session : findSessionsforContact(contact)) {
//            if(!session.isTrusted()) {
				// TODO: handle this properly
  //              continue;
	//        }
			message.addHeader(session.processSending(message.getInnerKey()));
		}
		Log.d(Config.LOGTAG, "Building axolotl own headers...");
		for(XmppAxolotlSession session : findOwnSessions()) {
	//        if(!session.isTrusted()) {
				// TODO: handle this properly
	  //          continue;
		//    }
			message.addHeader(session.processSending(message.getInnerKey()));
		}

		return message;
	}

	public XmppAxolotlMessage.XmppAxolotlPlaintextMessage processReceiving(XmppAxolotlMessage message) {
		XmppAxolotlMessage.XmppAxolotlPlaintextMessage plaintextMessage = null;
		AxolotlAddress senderAddress = new AxolotlAddress(message.getContact().getJid().toBareJid().toString(),
				message.getSenderDeviceId());

		XmppAxolotlSession session = sessions.get(senderAddress);
		if (session == null) {
			Log.d(Config.LOGTAG, "No axolotl session found while parsing received message " + message);
			// TODO: handle this properly
			session = new XmppAxolotlSession(axolotlStore, senderAddress);

		}

		for(XmppAxolotlMessage.XmppAxolotlMessageHeader header : message.getHeaders()) {
			if (header.getRecipientDeviceId() == ownDeviceId) {
				Log.d(Config.LOGTAG, "Found axolotl header matching own device ID, processing...");
				byte[] payloadKey = session.processReceiving(header);
				if (payloadKey != null) {
					Log.d(Config.LOGTAG, "Got payload key from axolotl header. Decrypting message...");
					plaintextMessage = message.decrypt(session, payloadKey);
				}
			}
		}

		return plaintextMessage;
	}
}