static Tcl_Mutex *locks = NULL;
static int locksCount = 0;
static Tcl_Mutex init_mx;
#endif /* OPENSSL_THREADS */
#endif /* TCL_THREADS */


/********************/
/* Callbacks        */
/********************/


/*
 *-------------------------------------------------------------------
 *
 * Eval Callback Command --
 *
 *	Eval callback command and catch any errors
 *

 *	monitors SSL connection process
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Calls callback (if defined)
 *
 *-------------------------------------------------------------------
 */
static void
InfoCallback(const SSL *ssl, int where, int ret) {
    State *statePtr = (State*)SSL_get_app_data((SSL *)ssl);
    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;

	if (where & SSL_CB_READ)		minor = "read";
	else if (where & SSL_CB_WRITE)		minor = "write";
	else if (where & SSL_CB_LOOP)		minor = "loop";
	else if (where & SSL_CB_EXIT)		minor = "exit";
	else					minor = "unknown";
    }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->callback);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("info", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr,
	    Tcl_NewStringObj(Tcl_GetChannelName(statePtr->self), -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(major, -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(minor, -1));

 *				  failure alert to peer, and terminate handshake.
 *	    1			- the certificate is deemed valid, continue with handshake.
 *	    empty string	- no change to certificate validation
 *
 * Side effects:
 *	The err field of the currently operative State is set
 *	  to a string describing the SSL negotiation failure reason
 *
 *-------------------------------------------------------------------
 */
static int
VerifyCallback(int ok, X509_STORE_CTX *ctx) {
    Tcl_Obj *cmdPtr;
    SSL   *ssl		= (SSL*)X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
    X509  *cert		= X509_STORE_CTX_get_current_cert(ctx);

	if (statePtr->vflags & SSL_VERIFY_FAIL_IF_NO_PEER_CERT) {
	    return ok;
	} else {
	    return 1;
	}
    }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->vcmd);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("verify", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr,
	Tcl_NewStringObj(Tcl_GetChannelName(statePtr->self), -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewIntObj(depth));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tls_NewX509Obj(interp, cert));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewIntObj(ok));
    Tcl_ListObjAppendElement(interp, cmdPtr,
	Tcl_NewStringObj((char*)X509_verify_cert_error_string(err), -1));

    statePtr->flags |= TLS_TCL_CALLBACK;

    /* Eval callback command */
    Tcl_IncrRefCount(cmdPtr);
    ok = EvalCallback(interp, statePtr, cmdPtr);
    Tcl_DecrRefCount(cmdPtr);

    statePtr->flags &= ~(TLS_TCL_CALLBACK);
    return(ok);	/* By default, leave verification unchanged. */
}

/*
 *-------------------------------------------------------------------
 *
 * Tls_Error --
 *
 *	Calls callback with $fd and $msg - so the callback can decide
 *	what to do with errors.
 *
 * Side effects:
 *	The err field of the currently operative State is set
 *	  to a string describing the SSL negotiation failure reason
 *
 *-------------------------------------------------------------------
 */
void
Tls_Error(State *statePtr, char *msg) {
    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;

 *
 * KeyLogCallback --
 *
 *	Write received key data to log file.
 *
 * Side effects:
 *	none
 *
 *-------------------------------------------------------------------
 */
void KeyLogCallback(const SSL *ssl, const char *line) {
    char *str = getenv(SSLKEYLOGFILE);
    FILE *fd;
    if (str) {
	fd = fopen(str, "a");
	fprintf(fd, "%s\n",line);
	fclose(fd);
    }
}

/*
 *-------------------------------------------------------------------
 *
 * Password Callback --
 *
 *	Called when a password is needed to unpack RSA and PEM keys.
 *	Evals any bound password script and returns the result as
 *	the password string.
 *
 *-------------------------------------------------------------------
 */
static int
PasswordCallback(char *buf, int size, int verify, void *udata) {
    State *statePtr	= (State *) udata;
    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;

	    strncpy(buf, ret, (size_t) size);
	    return (int)strlen(ret);
	} else {
	    return -1;
	}
    }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->password);

    Tcl_Preserve((ClientData) interp);
    Tcl_Preserve((ClientData) statePtr);

    /* Eval callback and success for ok, abort for error, continue for continue */
    Tcl_IncrRefCount(cmdPtr);

    if (statePtr->callback == (Tcl_Obj*)NULL) {
	return SSL_TLSEXT_ERR_OK;
    } else if (ssl == NULL) {
	return SSL_TLSEXT_ERR_NOACK;
    }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->callback);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("session", -1));

    /* Session id */
    session_id = SSL_SESSION_get_id(session, &ulen);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewByteArrayObj(session_id, (int) ulen));

	res = SSL_TLSEXT_ERR_NOACK;
    }

    if (statePtr->vcmd == (Tcl_Obj*)NULL) {
	return res;
    }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->vcmd);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("alpn", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(*out, -1));

    /* Eval callback command */
    Tcl_IncrRefCount(cmdPtr);
    if ((code = EvalCallback(interp, statePtr, cmdPtr)) > 1) {

#endif

/*
 *-------------------------------------------------------------------
 *
 * SNI Callback for Servers --
 *
 *	Perform server-side SNI hostname selection after receiving SNI extension
 *	in Client Hello. Called after hello callback but before ALPN callback.
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Calls callback (if defined)
 *

    dprintf("Called");

    if (ssl == NULL || arg == NULL) {
	return SSL_TLSEXT_ERR_NOACK;
    }

    /* Only works for TLS 1.2 and earlier */
    servername = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
    if (!servername || servername[0] == '\0') {
	return SSL_TLSEXT_ERR_NOACK;
    }

    if (statePtr->vcmd == (Tcl_Obj*)NULL) {
	return SSL_TLSEXT_ERR_OK;
    }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->vcmd);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("sni", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(servername , -1));

    /* Eval callback command */
    Tcl_IncrRefCount(cmdPtr);
    if ((code = EvalCallback(interp, statePtr, cmdPtr)) > 1) {

    } else if (ssl == NULL || arg == NULL) {
	return SSL_CLIENT_HELLO_ERROR;
    }

    /* Get names */
    if (!SSL_client_hello_get0_ext(ssl, TLSEXT_TYPE_server_name, &p, &remaining) || remaining <= 2) {
	*alert = SSL_R_SSLV3_ALERT_ILLEGAL_PARAMETER;
	return SSL_CLIENT_HELLO_ERROR;
    }

    /* Extract the length of the supplied list of names. */
    len = (*(p++) << 8);
    len += *(p++);
    if (len + 2 != remaining) {
	*alert = SSL_R_SSLV3_ALERT_ILLEGAL_PARAMETER;
	return SSL_CLIENT_HELLO_ERROR;
    }
    remaining = len;

    /* The list in practice only has a single element, so we only consider the first one. */
    if (remaining == 0 || *p++ != TLSEXT_NAMETYPE_host_name) {
	*alert = SSL_R_TLSV1_ALERT_INTERNAL_ERROR;
	return SSL_CLIENT_HELLO_ERROR;
    }
    remaining--;

    /* Now we can finally pull out the byte array with the actual hostname. */
    if (remaining <= 2) {
	*alert = SSL_R_TLSV1_ALERT_INTERNAL_ERROR;
	return SSL_CLIENT_HELLO_ERROR;
    }
    len = (*(p++) << 8);
    len += *(p++);
    if (len + 2 > remaining) {
	*alert = SSL_R_TLSV1_ALERT_INTERNAL_ERROR;
	return SSL_CLIENT_HELLO_ERROR;
    }
    remaining = len;
    servername = (const char *)p;

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->vcmd);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("hello", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(servername, (int) len));

    /* Eval callback command */
    Tcl_IncrRefCount(cmdPtr);
    if ((code = EvalCallback(interp, statePtr, cmdPtr)) > 1) {

#endif
	case TLS_TLS1_3:
#if defined(NO_TLS1_3) || defined(OPENSSL_NO_TLS1_3)
	    Tcl_AppendResult(interp, protocols[index], ": protocol not supported", NULL);
	    return TCL_ERROR;
#else
	    ctx = SSL_CTX_new(TLS_method());
	    SSL_CTX_set_min_proto_version(ctx, TLS1_3_VERSION);
	    SSL_CTX_set_max_proto_version(ctx, TLS1_3_VERSION);
	    break;
#endif
	default:
	    break;
    }
    if (ctx == NULL) {

    }

    objPtr = Tcl_NewListObj(0, NULL);

#if OPENSSL_VERSION_NUMBER < 0x10100000L && !defined(NO_SSL2) && !defined(OPENSSL_NO_SSL2)
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(protocols[TLS_SSL2], -1));
#endif
#if !defined(NO_SSL3) && !defined(OPENSSL_NO_SSL3) && !defined(OPENSSL_NO_SSL3_METHOD)
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(protocols[TLS_SSL3], -1));
#endif
#if !defined(NO_TLS1) && !defined(OPENSSL_NO_TLS1) && !defined(OPENSSL_NO_TLS1_METHOD)
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(protocols[TLS_TLS1], -1));
#endif
#if !defined(NO_TLS1_1) && !defined(OPENSSL_NO_TLS1_1) && !defined(OPENSSL_NO_TLS1_1_METHOD)
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(protocols[TLS_TLS1_1], -1));
#endif
#if !defined(NO_TLS1_2) && !defined(OPENSSL_NO_TLS1_2) && !defined(OPENSSL_NO_TLS1_2_METHOD)
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(protocols[TLS_TLS1_2], -1));
#endif
#if !defined(NO_TLS1_3) && !defined(OPENSSL_NO_TLS1_3)
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(protocols[TLS_TLS1_3], -1));
#endif

    Tcl_SetObjResult(interp, objPtr);

	if (opt[0] != '-')
	    break;

	OPTOBJ("-alpn", alpn);
	OPTSTR("-cadir", CAdir);
	OPTSTR("-cafile", CAfile);
	OPTBYTE("-cert", cert, cert_len);
	OPTSTR("-certfile", certfile);
	OPTSTR("-cipher", ciphers);
	OPTSTR("-ciphers", ciphers);
	OPTSTR("-ciphersuites", ciphersuites);
	OPTOBJ("-command", script);
	OPTSTR("-dhparams", DHparams);
	OPTBYTE("-key", key, key_len);
	OPTSTR("-keyfile", keyfile);
	OPTSTR("-model", model);
	OPTOBJ("-password", password);
	OPTBOOL("-post_handshake", post_handshake);

	OPTBOOL("-request", request);
	OPTBOOL("-require", require);
	OPTINT("-securitylevel", level);
	OPTBOOL("-server", server);
	OPTSTR("-servername", servername);
	OPTSTR("-session_id", session_id);
	OPTBOOL("-ssl2", ssl2);
	OPTBOOL("-ssl3", ssl3);
	OPTBOOL("-tls1", tls1);
	OPTBOOL("-tls1.1", tls1_1);
	OPTBOOL("-tls1.2", tls1_2);
	OPTBOOL("-tls1.3", tls1_3);
	OPTOBJ("-validatecommand", vcmd);
	OPTOBJ("-vcmd", vcmd);



	OPTBAD("option", "-alpn, -cadir, -cafile, -cert, -certfile, -cipher, -ciphersuites, -command, -dhparams, -key, -keyfile, -model, -password, -post_handshake, -request, -require, -securitylevel, -server, -servername, -session_id, -ssl2, -ssl3, -tls1, -tls1.1, -tls1.2, -tls1.3, or -validatecommand");

	return TCL_ERROR;
    }
    if (request)		verify |= SSL_VERIFY_CLIENT_ONCE | SSL_VERIFY_PEER;
    if (request && require)	verify |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
    if (request && post_handshake)	verify |= SSL_VERIFY_POST_HANDSHAKE;
    if (verify == 0)		verify = SSL_VERIFY_NONE;

    proto |= (ssl2 ? TLS_PROTO_SSL2 : 0);
    proto |= (ssl3 ? TLS_PROTO_SSL3 : 0);
    proto |= (tls1 ? TLS_PROTO_TLS1 : 0);
    proto |= (tls1_1 ? TLS_PROTO_TLS1_1 : 0);
    proto |= (tls1_2 ? TLS_PROTO_TLS1_2 : 0);
    proto |= (tls1_3 ? TLS_PROTO_TLS1_3 : 0);

	Tls_Free((char *) statePtr);
	return TCL_ERROR;
    }

    /* Set host server name */
    if (servername) {
	/* Sets the server name indication (SNI) in ClientHello extension */
	/* Per RFC 6066, hostname is a ASCII encoded string. */
	if (!SSL_set_tlsext_host_name(statePtr->ssl, servername) && require) {
	    Tcl_AppendResult(interp, "setting TLS host name extension failed", (char *) NULL);
	    Tls_Free((char *) statePtr);
	    return TCL_ERROR;
	}

	/* Configure server host name checks in the SSL client. Set DNS hostname to
	   name for peer certificate checks. SSL_set1_host has limitations. */
	if (!SSL_add1_host(statePtr->ssl, servername)) {
	    Tcl_AppendResult(interp, "setting DNS host name failed", (char *) NULL);
	    Tls_Free((char *) statePtr);
	    return TCL_ERROR;
	}
    }

    /* Resume session id */
    if (session_id && strlen(session_id) <= SSL_MAX_SID_CTX_LENGTH) {
	/* SSL_set_session() */
	if (!SSL_SESSION_set1_id_context(SSL_get_session(statePtr->ssl), session_id, (unsigned int) strlen(session_id))) {

	/* Server callbacks */
	SSL_CTX_set_tlsext_servername_arg(statePtr->ctx, (void *)statePtr);
	SSL_CTX_set_tlsext_servername_callback(statePtr->ctx, SNICallback);
	SSL_CTX_set_client_hello_cb(statePtr->ctx, HelloCallback, (void *)statePtr);
	if (statePtr->protos != NULL) {
	    SSL_CTX_set_alpn_select_cb(statePtr->ctx, ALPNCallback, (void *)statePtr);
#ifdef USE_NPN
	    if (tls1_2 == 0 && tls1_3 == 0) {
		SSL_CTX_set_next_protos_advertised_cb(statePtr->ctx, NPNCallback, (void *)statePtr);
	    }
#endif
	}

	/* Enable server to send cert request after handshake (TLS 1.3 only) */
	/* A write operation must take place for the Certificate Request to be
	   sent to the client, this can be done with SSL_do_handshake(). */
	if (request && post_handshake) {
	    SSL_verify_client_post_handshake(statePtr->ssl);
	}

	/* Set server mode */
	statePtr->flags |= TLS_TCL_SERVER;
	SSL_set_accept_state(statePtr->ssl);
    } else {
	/* Client callbacks */

#ifdef USE_NPN
	if (statePtr->protos != NULL && tls1_2 == 0 && tls1_3 == 0) {
	    SSL_CTX_set_next_proto_select_cb(statePtr->ctx, ALPNCallback, (void *)statePtr);
	}
#endif

	/* Session caching */
	SSL_CTX_set_session_cache_mode(statePtr->ctx, SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_NO_INTERNAL_STORE);
	SSL_CTX_sess_set_new_cb(statePtr->ctx, SessionCallback);

	/* Enable post handshake Authentication extension. TLS 1.3 only, not http/2. */
	if (request && post_handshake) {
	    SSL_set_post_handshake_auth(statePtr->ssl, 1);
	}

	/* Set client mode */
	SSL_set_connect_state(statePtr->ssl);
    }
    SSL_set_bio(statePtr->ssl, statePtr->p_bio, statePtr->p_bio);
    BIO_set_ssl(statePtr->bio, statePtr->ssl, BIO_NOCLOSE);

    /*
     * End of SSL Init

#if !defined(NO_TLS1_3) && !defined(OPENSSL_NO_TLS1_3)
	off |= (ENABLED(proto, TLS_PROTO_TLS1_3) ? 0 : SSL_OP_NO_TLSv1_3);
#endif
	break;
    }

    ERR_clear_error();


    ctx = SSL_CTX_new(method);
    if (!ctx) {
	return(NULL);
    }

    if (getenv(SSLKEYLOGFILE)) {
	SSL_CTX_set_keylog_callback(ctx, KeyLogCallback);
    }

#if OPENSSL_VERSION_NUMBER < 0x10101000L
    SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);	/* handle new handshakes in background. On by default in OpenSSL 1.1.1. */
#endif
    SSL_CTX_sess_set_cache_size(ctx, 128);

    /* Set user defined ciphers, cipher suites, and security level */
    if ((ciphers != NULL) && !SSL_CTX_set_cipher_list(ctx, ciphers)) {
	Tcl_AppendResult(interp, "Set ciphers failed: No valid ciphers", (char *) NULL);
	SSL_CTX_free(ctx);
	return NULL;
    }
    if ((ciphersuites != NULL) && !SSL_CTX_set_ciphersuites(ctx, ciphersuites)) {
	Tcl_AppendResult(interp, "Set cipher suites failed: No valid ciphers", (char *) NULL);
	SSL_CTX_free(ctx);
	return NULL;
    }

    /* Set security level */
    if (level > -1 && level < 6) {
	/* SSL_set_security_level */
	SSL_CTX_set_security_level(ctx, level);
    }

    chan = Tcl_GetTopChannel(chan);
    if (Tcl_GetChannelType(chan) != Tls_ChannelType()) {
	Tcl_AppendResult(interp, "bad channel \"", Tcl_GetChannelName(chan),
		"\": not a TLS channel", NULL);
	return TCL_ERROR;
    }
    statePtr = (State *) Tcl_GetChannelInstanceData(chan);

    /* Get certificate for peer or self */
    if (objc == 2) {
	peer = SSL_get_peer_certificate(statePtr->ssl);
    } else {
	peer = SSL_get_certificate(statePtr->ssl);
    }
    if (peer) {
	objPtr = Tls_NewX509Obj(interp, peer);

	bits = SSL_CIPHER_get_bits(cipher, &alg_bits);
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("bits", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewIntObj(bits));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("secret_bits", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewIntObj(alg_bits));
	/* alg_bits is actual key secret bits. If use bits and secret (algorithm) bits differ,
	   the rest of the bits are fixed, i.e. for limited export ciphers (bits < 56) */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("min_version", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(SSL_CIPHER_get_version(cipher), -1));

	/* Get OpenSSL-specific ID, not IANA ID */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("id", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewIntObj((int) SSL_CIPHER_get_id(cipher)));

    static int initialized = 0;
    int status = TCL_OK;
#if defined(OPENSSL_THREADS) && defined(TCL_THREADS)
    size_t num_locks;
#endif

    if (uninitialize) {
	if (!initialized) {
	    dprintf("Asked to uninitialize, but we are not initialized");

	    return(TCL_OK);
	}

	dprintf("Asked to uninitialize");

#if defined(OPENSSL_THREADS) && defined(TCL_THREADS)
	Tcl_MutexLock(&init_mx);

	if (locks) {
	    free(locks);
	    locks = NULL;
	    locksCount = 0;
	}
#endif
	initialized = 0;

#if defined(OPENSSL_THREADS) && defined(TCL_THREADS)
	Tcl_MutexUnlock(&init_mx);
#endif

	return(TCL_OK);
    }

    if (initialized) {
	dprintf("Called, but using cached value");
	return(status);
    }

    dprintf("Called");

#if defined(OPENSSL_THREADS) && defined(TCL_THREADS)
    Tcl_MutexLock(&init_mx);
#endif