jni/libzrtp/sources/clients/tivi/CtZrtpSession.cpp

/*
 * Tivi client glue code for ZRTP.
 * Copyright (c) 2012 Slient Circle LLC.  All rights reserved.
 *
 *
 * @author Werner Dittmann <Werner.Dittmann@t-online.de>
 */

#include <string>
#include <stdio.h>

#include <libzrtpcpp/ZIDCache.h>
#include <libzrtpcpp/ZRtp.h>

#include <CtZrtpStream.h>
#include <CtZrtpCallback.h>
#include <CtZrtpSession.h>

#include <common/Thread.h>

static CMutexClass sessionLock;

const char *getZrtpBuildInfo()
{
    return zrtpBuildInfo;
}
CtZrtpSession::CtZrtpSession() : mitmMode(false), signSas(false), enableParanoidMode(false), isReady(false),
    zrtpEnabled(true), sdesEnabled(true) {

    clientIdString = clientId;
    streams[AudioStream] = NULL;
    streams[VideoStream] = NULL;
}

int CtZrtpSession::initCache(const char *zidFilename) {
    ZIDCache* zf = getZidCacheInstance();
    if (!zf->isOpen()) {
        std::string fname;
        if (zidFilename == NULL) {
            char *home = getenv("HOME");
            std::string baseDir = (home != NULL) ? (std::string(home) + std::string("/."))
                                                    : std::string(".");
            fname = baseDir + std::string("GNUZRTP.zid");
            zidFilename = fname.c_str();
        }
        if (zf->open((char *)zidFilename) < 0) {
            return -1;
        }
    }
    return 1;
}

int CtZrtpSession::init(bool audio, bool video, ZrtpConfigure* config)
{
    int32_t ret = 1;

    synchEnter();

    ZrtpConfigure* configOwn = NULL;
    if (config == NULL) {
        config = configOwn = new ZrtpConfigure();
        setupConfiguration(config);
        config->setTrustedMitM(true);
    }
    config->setParanoidMode(enableParanoidMode);

    ZIDCache* zf = getZidCacheInstance();
    if (!zf->isOpen()) {
        ret = -1;
    }
    if (ret > 0) {
        const uint8_t* ownZid = zf->getZid();
        CtZrtpStream *stream;

        // Create CTZrtpStream object only once, they are availbe for the whole
        // lifetime of the session.
        if (audio) {
            if (streams[AudioStream] == NULL)
                streams[AudioStream] = new CtZrtpStream();
            stream = streams[AudioStream];
            stream->zrtpEngine = new ZRtp((uint8_t*)ownZid, stream, clientIdString, config, mitmMode, signSas);
            stream->type = Master;
            stream->index = AudioStream;
            stream->session = this;
        }
        if (video) {
            if (streams[VideoStream] == NULL)
                streams[VideoStream] = new CtZrtpStream();
            stream = streams[VideoStream];
            stream->zrtpEngine = new ZRtp((uint8_t*)ownZid, stream, clientIdString, config);
            stream->type = Slave;
            stream->index = VideoStream;
            stream->session = this;
        }
    }
    if (configOwn != NULL) {
        delete configOwn;
    }
    synchLeave();
    isReady = true;
    return ret;
}

CtZrtpSession::~CtZrtpSession() {

    delete streams[AudioStream];
    delete streams[VideoStream];
}

void zrtp_log(const char *tag, const char *buf);
void CtZrtpSession::setupConfiguration(ZrtpConfigure *conf) {

// Set _WITHOUT_TIVI_ENV to a real name that is TRUE if the Tivi client is compiled/built.
#ifdef _WITHOUT_TIVI_ENV
#define GET_CFG_I(RET,_KEY)
#else
void *findGlobalCfgKey(char *key, int iKeyLen, int &iSize, char **opt, int *type);
#define GET_CFG_I(RET,_KEY) {int *p=(int*)findGlobalCfgKey((char*)_KEY,sizeof(_KEY)-1,iSZ,&opt,&type);if(p && iSZ==4)RET=*p;else RET=-1;}
#endif


// The next three vars are used in case of a real Tivi compile, see macro above.
    int iSZ;
    char *opt;
    int type;
    void zrtp_log( const char *tag, const char *buf);

    int b32sas = 0, iDisableDH2K = 0, iDisableAES256 = 0, iPreferDH2K = 0;
    int iDisableECDH256 = 0, iDisableECDH384 = 0, iEnableSHA384 = 1;
    int iDisableSkein = 0, iDisableTwofish = 0, iPreferNIST = 0;
    int iDisableSkeinHash = 0, iDisableBernsteinCurve25519 = 0, iDisableBernsteinCurve3617 = 0;

    GET_CFG_I(b32sas, "iDisable256SAS");
    GET_CFG_I(iDisableAES256, "iDisableAES256");
    GET_CFG_I(iDisableDH2K, "iDisableDH2K");
    GET_CFG_I(iPreferDH2K, "iPreferDH2K");

    GET_CFG_I(iDisableECDH256, "iDisableECDH256");
    GET_CFG_I(iDisableECDH384, "iDisableECDH384");
    GET_CFG_I(iEnableSHA384, "iEnableSHA384");
    GET_CFG_I(iDisableSkein, "iDisableSkein");
    GET_CFG_I(iDisableTwofish, "iDisableTwofish");
    GET_CFG_I(iPreferNIST, "iPreferNIST");

    GET_CFG_I(iDisableSkeinHash, "iDisableSkeinHash");
    GET_CFG_I(iDisableBernsteinCurve25519, "iDisableBernsteinCurve25519");
    GET_CFG_I(iDisableBernsteinCurve3617, "iDisableBernsteinCurve3617");

    conf->clear();

    /*
     * Setting the selection policy is a more generic policy than the iPreferNIST
     * configuration set by the user. The selection policy is a decision of the
     * client, not the user
     */
    conf->setSelectionPolicy(ZrtpConfigure::PreferNonNist);

    /*
     * Handling of iPreferNIST: if this is false (== 0) then we add the non-NIST algorithms
     * to the configuration and place them in front of the NIST algorithms. Refer to RFC6189
     * section 4.1.2 regarding selection of the public key algorithm.
     * 
     * With the configuration flags we can enable/disable each ECC PK algorithm separately.
     * 
     */
    if (iPreferNIST == 0) {
        if (iDisableBernsteinCurve3617 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("E414"));
        if (iDisableECDH384 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("EC38"));
    }
    else {
        if (iDisableECDH384 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("EC38"));
        if (iDisableBernsteinCurve3617 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("E414"));
    }

    if (iPreferNIST == 0) {
        if (iDisableBernsteinCurve25519 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("E255"));
        if (iDisableECDH256 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("EC25"));
    }
    else {
        if (iDisableECDH256 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("EC25"));
        if (iDisableBernsteinCurve25519 == 0)
            conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("E255"));
    }

    // DH2K handling: if DH2K not disabled and prefered put it infrom of DH3K,
    // If not preferred and not disabled put if after DH3K. Don't use DH2K if
    // it's not enabled at all (iDisableDH2K == 1)
    if (iPreferDH2K && iDisableDH2K == 0) {
        conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("DH2k"));
    }
    conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("DH3k"));
    if (iPreferDH2K == 0 && iDisableDH2K == 0)
        conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("DH2k"));

    conf->addAlgo(PubKeyAlgorithm, zrtpPubKeys.getByName("Mult"));


    // Handling of Hash algorithms: similar to PK, if PreferNIST is false
    // then put Skein in fromt oF SHA. Regardless if the Hash is enabled or
    // not: if configuration enables a large curve then also use the large
    // hashes.
    if (iPreferNIST == 0) {
        if (iDisableSkeinHash == 0 || iDisableBernsteinCurve3617 == 0)
            conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("SKN3"));
        if (iEnableSHA384 == 1 || iDisableECDH384 == 0) 
            conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("S384"));
    }
    else {
        if (iEnableSHA384 == 1 || iDisableECDH384 == 0) 
            conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("S384"));
        if (iDisableSkeinHash == 0 || iDisableBernsteinCurve3617 == 0)
            conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("SKN3"));
    }

    if (iPreferNIST == 0) {
        if (iDisableSkeinHash == 0)
            conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("SKN2"));
        conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("S256"));
    }
    else {
        conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("S256"));
        if (iDisableSkeinHash == 0)
            conf->addAlgo(HashAlgorithm, zrtpHashes.getByName("SKN2"));
    }

    // Handling of Symmetric algorithms: always prefer twofish (regardless
    // of NIST setting) if it is not disabled. iDisableAES256 means: disable
    // large ciphers
    if (iDisableAES256 == 0) {
        if (iDisableTwofish == 0)
            conf->addAlgo(CipherAlgorithm, zrtpSymCiphers.getByName("2FS3"));
        conf->addAlgo(CipherAlgorithm, zrtpSymCiphers.getByName("AES3"));
    }

    if (iDisableTwofish == 0)
        conf->addAlgo(CipherAlgorithm, zrtpSymCiphers.getByName("2FS1"));
    conf->addAlgo(CipherAlgorithm, zrtpSymCiphers.getByName("AES1"));

    if (b32sas == 1) {
        conf->addAlgo(SasType, zrtpSasTypes.getByName("B32 "));
    }
    else {
        conf->addAlgo(SasType, zrtpSasTypes.getByName("B256"));
        conf->addAlgo(SasType, zrtpSasTypes.getByName("B32 "));
    }

    if (iPreferNIST == 0) {
        if (iDisableSkein == 0) {
            conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("SK32"));
            conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("SK64"));
        }
        conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("HS32"));
        conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("HS80"));
    }
    else {
        conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("HS32"));
        conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("HS80"));
        if (iDisableSkein == 0) {
            conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("SK32"));
            conf->addAlgo(AuthLength, zrtpAuthLengths.getByName("SK64"));
        }
    }
}

void CtZrtpSession::setUserCallback(CtZrtpCb* ucb, streamName streamNm) {
    if (!(streamNm >= 0 && streamNm <= AllStreams && streams[streamNm] != NULL))
        return;

    if (streamNm == AllStreams) {
        for (int sn = 0; sn < AllStreams; sn++)
            streams[sn]->setUserCallback(ucb);
    }
    else
        streams[streamNm]->setUserCallback(ucb);
}

void CtZrtpSession::setSendCallback(CtZrtpSendCb* scb, streamName streamNm) {
    if (!(streamNm >= 0 && streamNm <= AllStreams && streams[streamNm] != NULL))
        return;

    if (streamNm == AllStreams) {
        for (int sn = 0; sn < AllStreams; sn++)
            streams[sn]->setSendCallback(scb);
    }
    else
        streams[streamNm]->setSendCallback(scb);

}

void CtZrtpSession::masterStreamSecure(CtZrtpStream *masterStream) {
    // Here we know that the AudioStream is the master and VideoStream the slave.
    // Otherwise we need to loop and find the Master stream and the Slave streams.

    multiStreamParameter = masterStream->zrtpEngine->getMultiStrParams();
    CtZrtpStream *strm = streams[VideoStream];
    if (strm->enableZrtp) {
        strm->zrtpEngine->setMultiStrParams(multiStreamParameter);
        strm->zrtpEngine->startZrtpEngine();
        strm->started = true;
        strm->tiviState = eLookingPeer;
        if (strm->zrtpUserCallback != 0)
            strm->zrtpUserCallback->onNewZrtpStatus(this, NULL, strm->index);

    }
}

int CtZrtpSession::startIfNotStarted(unsigned int uiSSRC, int streamNm) {
    if (!(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return 0;

    if ((streamNm == VideoStream && !isSecure(AudioStream)) || streams[streamNm]->started)
        return 0;

    start(uiSSRC, streamNm == VideoStream ? CtZrtpSession::VideoStream : CtZrtpSession::AudioStream);
    return 0;
}

void CtZrtpSession::start(unsigned int uiSSRC, CtZrtpSession::streamName streamNm) {
    if (!zrtpEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return;

    CtZrtpStream *stream = streams[streamNm];

    stream->ownSSRC = uiSSRC;
    stream->enableZrtp = true;
    if (stream->type == Master) {
        stream->zrtpEngine->startZrtpEngine();
        stream->started = true;
        stream->tiviState = eLookingPeer;
        if (stream->zrtpUserCallback != 0)
            stream->zrtpUserCallback->onNewZrtpStatus(this, NULL, stream->index);
        return;
    }
    // Process a Slave stream.
    if (!multiStreamParameter.empty()) {        // Multi-stream parameters available
        stream->zrtpEngine->setMultiStrParams(multiStreamParameter);
        stream->zrtpEngine->startZrtpEngine();
        stream->started = true;
        stream->tiviState = eLookingPeer;
        if (stream->zrtpUserCallback != 0)
            stream->zrtpUserCallback->onNewZrtpStatus(this, NULL, stream->index);
    }
}

void CtZrtpSession::stop(streamName streamNm) {
    if (!(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return;

    streams[streamNm]->isStopped = true;
}

void CtZrtpSession::release() {
    release(AudioStream);
    release(VideoStream);
}

void CtZrtpSession::release(streamName streamNm) {
    if (!(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return;

    CtZrtpStream *stream = streams[streamNm];
    stream->stopStream();                      // stop and reset stream
}

void CtZrtpSession::setLastPeerNameVerify(const char *name, int iIsMitm) {
    CtZrtpStream *stream = streams[AudioStream];

    if (!isReady || !stream || stream->isStopped)
        return;

    uint8_t peerZid[IDENTIFIER_LEN];
    std::string nm(name);
    stream->zrtpEngine->getPeerZid(peerZid);
    getZidCacheInstance()->putPeerName(peerZid, nm);
    setVerify(1);
}

int CtZrtpSession::isSecure(streamName streamNm) {
    if (!(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return 0;

    CtZrtpStream *stream = streams[streamNm];
    return stream->isSecure();
}

bool CtZrtpSession::processOutoingRtp(uint8_t *buffer, size_t length, size_t *newLength, streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return false;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return false;

    return stream->processOutgoingRtp(buffer, length, newLength);
}

int32_t CtZrtpSession::processIncomingRtp(uint8_t *buffer, size_t length, size_t *newLength, streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return fail;

    return stream->processIncomingRtp(buffer, length, newLength);
}

bool CtZrtpSession::isStarted(streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return false;

    return streams[streamNm]->isStarted();
}

bool CtZrtpSession::isEnabled(streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return false;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return false;

    return stream->isEnabled();
}

CtZrtpSession::tiviStatus CtZrtpSession::getCurrentState(streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return eWrongStream;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return eWrongStream;

    return stream->getCurrentState();
}

CtZrtpSession::tiviStatus CtZrtpSession::getPreviousState(streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return eWrongStream;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return eWrongStream;

    return stream->getPreviousState();
}

bool CtZrtpSession::isZrtpEnabled() {
    return zrtpEnabled;
}

bool CtZrtpSession::isSdesEnabled() {
    return sdesEnabled;
}

void CtZrtpSession::setZrtpEnabled(bool yesNo) {
    zrtpEnabled = yesNo;
}

void CtZrtpSession::setSdesEnabled(bool yesNo) {
    sdesEnabled = yesNo;
}

int CtZrtpSession::getSignalingHelloHash(char *helloHash, streamName streamNm, int32_t index) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return 0;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return 0;

    return stream->getSignalingHelloHash(helloHash, index);
}

void CtZrtpSession::setSignalingHelloHash(const char *helloHash, streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return;

    stream->setSignalingHelloHash(helloHash);
}

void CtZrtpSession::setVerify(int iVerified) {
    CtZrtpStream *stream = streams[AudioStream];

    if (!isReady || !stream || stream->isStopped)
        return;

    if (iVerified) {
        stream->zrtpEngine->SASVerified();
        stream->sasVerified = true;
    }
    else {
        stream->zrtpEngine->resetSASVerified();
        stream->sasVerified = false;
    }
}

int CtZrtpSession::getInfo(const char *key, uint8_t *buffer, size_t maxLen, streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    return stream->getInfo(key, (char*)buffer, (int)maxLen);
}

int CtZrtpSession::enrollAccepted(char *p) {
    if (!isReady || !(streams[AudioStream] != NULL))
        return fail;

    CtZrtpStream *stream = streams[AudioStream];
    int ret = stream->enrollAccepted(p);
    setVerify(true);
    return ret;
}

int CtZrtpSession::enrollDenied() {
    if (!isReady || !(streams[AudioStream] != NULL))
        return fail;

    CtZrtpStream *stream = streams[AudioStream];
    int ret = stream->enrollDenied();
    setVerify(true);                        // TODO : Janis -> is that correct in this case?
    return ret;
}

void CtZrtpSession::setClientId(std::string id) {
    clientIdString = id;
}

bool CtZrtpSession::createSdes(char *cryptoString, size_t *maxLen, streamName streamNm, const sdesSuites suite) {

    if (!isReady || !sdesEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    return stream->createSdes(cryptoString, maxLen, static_cast<ZrtpSdesStream::sdesSuites>(suite));
}

bool CtZrtpSession::parseSdes(char *recvCryptoStr, size_t recvLength, char *sendCryptoStr,
                              size_t *sendLength, bool sipInvite, streamName streamNm) {

    if (!isReady || !sdesEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    return stream->parseSdes(recvCryptoStr, recvLength, sendCryptoStr, sendLength, sipInvite);
}

bool CtZrtpSession::getSavedSdes(char *sendCryptoStr, size_t *sendLength, streamName streamNm) {
    if (!isReady || !sdesEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    return stream->getSavedSdes(sendCryptoStr, sendLength);
}

bool CtZrtpSession::isSdesActive(streamName streamNm) {
    if (!isReady || !sdesEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    return stream->isSdesActive();
}

int CtZrtpSession::getCryptoMixAttribute(char *algoNames, size_t length, streamName streamNm) {
    if (!isReady || !sdesEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return 0;

    CtZrtpStream *stream = streams[streamNm];
    return stream->getCryptoMixAttribute(algoNames, length);
}

bool CtZrtpSession::setCryptoMixAttribute(const char *algoNames, streamName streamNm) {
    if (!isReady || !sdesEnabled || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return fail;

    CtZrtpStream *stream = streams[streamNm];
    return stream->setCryptoMixAttribute(algoNames);
}

void CtZrtpSession::resetSdesContext(streamName streamNm, bool force) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return;

    CtZrtpStream *stream = streams[streamNm];
    stream->resetSdesContext(force);
}


int32_t CtZrtpSession::getNumberSupportedVersions(streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return 0;

    CtZrtpStream *stream = streams[streamNm];
    return stream->getNumberSupportedVersions();
}

const char* CtZrtpSession::getZrtpEncapAttribute(streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return NULL;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return NULL;

    return stream->getZrtpEncapAttribute();
}

void CtZrtpSession::setZrtpEncapAttribute(const char *attribute, streamName streamNm) {
    if (!isReady || !(streamNm >= 0 && streamNm < AllStreams && streams[streamNm] != NULL))
        return;

    CtZrtpStream *stream = streams[streamNm];
    if (stream->isStopped)
        return;

    stream->setZrtpEncapAttribute(attribute);
}

void CtZrtpSession::setAuxSecret(const unsigned char *secret, int length) {
    if (!isReady || !(streams[AudioStream] != NULL))
        return;

    CtZrtpStream *stream = streams[AudioStream];
    if (stream->isStopped)
        return;

    stream->setAuxSecret(secret, length);
}

void CtZrtpSession::cleanCache() {
    getZidCacheInstance()->cleanup();
}

void CtZrtpSession::synchEnter() {
    sessionLock.Lock();
}

void CtZrtpSession::synchLeave() {
    sessionLock.Unlock();
}