path: root/tls/tlsIO.c

/*
 * Copyright (C) 1997-2000 Matt Newman <matt@novadigm.com>
 * Copyright (C) 2000 Ajuba Solutions
 *
 * $Header: /cvsroot/tls/tls/tlsIO.c,v 1.19 2015/06/06 09:07:08 apnadkarni Exp $
 *
 * TLS (aka SSL) Channel - can be layered on any bi-directional
 * Tcl_Channel (Note: Requires Trf Core Patch)
 *
 * This was built from scratch based upon observation of OpenSSL 0.9.2B
 *
 * Addition credit is due for Andreas Kupries (a.kupries@westend.com), for
 * providing the Tcl_ReplaceChannel mechanism and working closely with me
 * to enhance it to support full fileevent semantics.
 *
 * Also work done by the follow people provided the impetus to do this "right":
 *	tclSSL (Colin McCormack, Shared Technology)
 *	SSLtcl (Peter Antman)
 *
 */

#include "tlsInt.h"

/*
 * Forward declarations
 */

static int	TlsBlockModeProc _ANSI_ARGS_((ClientData instanceData,
			int mode));
static int	TlsCloseProc _ANSI_ARGS_ ((ClientData instanceData,
			Tcl_Interp *interp));
static int	TlsInputProc _ANSI_ARGS_((ClientData instanceData,
			char *buf, int bufSize, int *errorCodePtr));
static int	TlsOutputProc _ANSI_ARGS_((ClientData instanceData,
			CONST char *buf, int toWrite, int *errorCodePtr));
static int	TlsGetOptionProc _ANSI_ARGS_ ((ClientData instanceData,
			Tcl_Interp *interp, CONST84 char *optionName,
			Tcl_DString *dsPtr));
static void	TlsWatchProc _ANSI_ARGS_((ClientData instanceData, int mask));
static int	TlsGetHandleProc _ANSI_ARGS_ ((ClientData instanceData,
			int direction, ClientData *handlePtr));
static int	TlsNotifyProc _ANSI_ARGS_ ((ClientData instanceData,
			int mask));
static void	TlsChannelHandler _ANSI_ARGS_ ((ClientData clientData,
			int mask));
static void	TlsChannelHandlerTimer _ANSI_ARGS_ ((ClientData clientData));

/*
 * This structure describes the channel type structure for TCP socket
 * based IO.  These are what the structures should look like, but we
 * have to build them up at runtime to be correct depending on whether
 * we are loaded into an 8.2.0-8.3.1 or 8.3.2+ Tcl interpreter.
 */
#ifdef TLS_STATIC_STRUCTURES_NOT_USED
static Tcl_ChannelType tlsChannelType2 = {
    "tls",		/* Type name. */
    TCL_CHANNEL_VERSION_2,	/* A v2 channel (8.3.2+) */
    TlsCloseProc,	/* Close proc. */
    TlsInputProc,	/* Input proc. */
    TlsOutputProc,	/* Output proc. */
    NULL,		/* Seek proc. */
    NULL,		/* Set option proc. */
    TlsGetOptionProc,	/* Get option proc. */
    TlsWatchProc,	/* Initialize notifier. */
    TlsGetHandleProc,	/* Get file handle out of channel. */
    NULL,		/* Close2Proc. */
    TlsBlockModeProc,	/* Set blocking/nonblocking mode.*/
    NULL,		/* FlushProc. */
    TlsNotifyProc,	/* handlerProc. */
};

static Tcl_ChannelType tlsChannelType1 = {
    "tls",		/* Type name. */
    TlsBlockModeProc,	/* Set blocking/nonblocking mode.*/
    TlsCloseProc,	/* Close proc. */
    TlsInputProc,	/* Input proc. */
    TlsOutputProc,	/* Output proc. */
    NULL,		/* Seek proc. */
    NULL,		/* Set option proc. */
    TlsGetOptionProc,	/* Get option proc. */
    TlsWatchProc,	/* Initialize notifier. */
    TlsGetHandleProc,	/* Get file handle out of channel. */
};
#else
static Tcl_ChannelType *tlsChannelType = NULL;
#endif

/*
 *-------------------------------------------------------------------
 *
 * Tls_ChannelType --
 *
 *	Return the correct TLS channel driver info
 *
 * Results:
 *	The correct channel driver for the current version of Tcl.
 *
 * Side effects:
 *	None.
 *
 *-------------------------------------------------------------------
 */
Tcl_ChannelType *Tls_ChannelType()
{
    /*
     * Initialize the channel type if necessary
     */
    if (tlsChannelType == NULL) {
	/*
	 * Allocation of a new channeltype structure is not easy, because of
	 * the various verson of the core and subsequent changes to the
	 * structure. The main challenge is to allocate enough memory for
	 * odern versions even if this extyension is compiled against one
	 * of the older variant!
	 *
	 * (1) Versions before stubs (8.0.x) are simple, because they are
	 *     supported only if the extension is compiled against exactly
	 *     that version of the core.
	 *
	 * (2) With stubs we just determine the difference between the older
	 *     and modern variant and overallocate accordingly if compiled
	 *     against an older variant.
	 */

	unsigned int size = sizeof(Tcl_ChannelType); /* Base size */

	/*
	 * Size of a procedure pointer. We assume that all procedure
	 * pointers are of the same size, regardless of exact type
	 * (arguments and return values).
	 *
	 * 8.2.   First version containing close2proc. Baseline.
	 * 8.3.2  Three additional vectors. Moved blockMode, new flush- and
	 *        handlerProc's.
	 *
	 * => Compilation against earlier version has to overallocate three
	 *    procedure pointers.
	 */

#ifdef EMULATE_CHANNEL_VERSION_2
	size += 3 * procPtrSize;
#endif

	tlsChannelType = (Tcl_ChannelType *) ckalloc(size);
	memset((VOID *) tlsChannelType, 0, size);

	/*
	 * Common elements of the structure (no changes in location or name)
	 * close2Proc, seekProc, setOptionProc stay NULL.
	 */

	tlsChannelType->typeName	= "tls";
	tlsChannelType->closeProc	= TlsCloseProc;
	tlsChannelType->inputProc	= TlsInputProc;
	tlsChannelType->outputProc	= TlsOutputProc;
	tlsChannelType->getOptionProc	= TlsGetOptionProc;
	tlsChannelType->watchProc	= TlsWatchProc;
	tlsChannelType->getHandleProc	= TlsGetHandleProc;

	/*
	 * blockModeProc is a twister.  We have to make some runtime-choices,
	 * depending on the version we compiled against.
	 */

#ifdef EMULATE_CHANNEL_VERSION_2
	/*
	 * We are compiling against an 8.3.1- core.  We have to create some
	 * definitions for the new elements as the compiler does not know them
	 * by name.
	 */

	if (channelTypeVersion == TLS_CHANNEL_VERSION_1) {
	    /*
	     * The 'version' element of 8.3.2 is in the the place of the
	     * blockModeProc. For 8.2.0-8.3.1 we have to set our blockModeProc
	     * into this place.
	     */
	    tlsChannelType->blockModeProc = TlsBlockModeProc;
	} else /* channelTypeVersion == TLS_CHANNEL_VERSION_2 */ {
	    /*
	     * For the 8.3.2 core we present ourselves as a version 2
	     * driver. This means a special value in version (ex
	     * blockModeProc), blockModeProc in a different place and of
	     * course usage of the handlerProc.  The last two have to
	     * referenced with pointer magic because they aren't defined
	     * otherwise.
	     */

	    tlsChannelType->blockModeProc =
		(Tcl_DriverBlockModeProc*) TLS_CHANNEL_VERSION_2;
	    (*((Tcl_DriverBlockModeProc**)(&(tlsChannelType->close2Proc)+1)))
		= TlsBlockModeProc;
	    (*((TlsDriverHandlerProc**)(&(tlsChannelType->close2Proc)+3)))
		= TlsNotifyProc;
	}
#else
	/*
	 * Compiled against 8.3.2+. Direct access to all elements possible. Use
	 * channelTypeVersion information to select the values to use.
	 */

	if (channelTypeVersion == TLS_CHANNEL_VERSION_1) {
	    /*
	     * The 'version' element of 8.3.2 is in the the place of the
	     * blockModeProc. For the original patch in 8.1.x and the firstly
	     * included (8.2) we have to set our blockModeProc into this
	     * place.
	     */
	    tlsChannelType->version = (Tcl_ChannelTypeVersion)TlsBlockModeProc;
	} else /* channelTypeVersion == TLS_CHANNEL_VERSION_2 */ {
	    /*
	     * For the 8.3.2 core we present ourselves as a version 2
	     * driver. This means a special value in version (ex
	     * blockModeProc), blockModeProc in a different place and of
	     * course usage of the handlerProc.
	     */

	    tlsChannelType->version       = TCL_CHANNEL_VERSION_2;
	    tlsChannelType->blockModeProc = TlsBlockModeProc;
	    tlsChannelType->handlerProc   = TlsNotifyProc;
	}
#endif
    }
    return tlsChannelType;
}

/*
 *-------------------------------------------------------------------
 *
 * TlsBlockModeProc --
 *
 *	This procedure is invoked by the generic IO level
 *       to set blocking and nonblocking modes
 * Results:
 *	0 if successful, errno when failed.
 *
 * Side effects:
 *	Sets the device into blocking or nonblocking mode.
 *
 *-------------------------------------------------------------------
 */

static int
TlsBlockModeProc(ClientData instanceData,	/* Socket state. */
                 int mode)			/* The mode to set. Can be one of
						* TCL_MODE_BLOCKING or
						* TCL_MODE_NONBLOCKING. */
{
    State *statePtr = (State *) instanceData;

    if (mode == TCL_MODE_NONBLOCKING) {
	statePtr->flags |= TLS_TCL_ASYNC;
    } else {
	statePtr->flags &= ~(TLS_TCL_ASYNC);
    }
    if (channelTypeVersion == TLS_CHANNEL_VERSION_2) {
	return 0;
    } else {
	return Tcl_SetChannelOption(statePtr->interp, Tls_GetParent(statePtr),
		"-blocking", (mode == TCL_MODE_NONBLOCKING) ? "0" : "1");
    }
}

/*
 *-------------------------------------------------------------------
 *
 * TlsCloseProc --
 *
 *	This procedure is invoked by the generic IO level to perform
 *	channel-type-specific cleanup when a SSL socket based channel
 *	is closed.
 *
 *	Note: we leave the underlying socket alone, is this right?
 *
 * Results:
 *	0 if successful, the value of Tcl_GetErrno() if failed.
 *
 * Side effects:
 *	Closes the socket of the channel.
 *
 *-------------------------------------------------------------------
 */
static int
TlsCloseProc(ClientData instanceData,	/* The socket to close. */
             Tcl_Interp *interp)	/* For error reporting - unused. */
{
    State *statePtr = (State *) instanceData;

    dprintf(stderr,"\nTlsCloseProc(0x%x)", (unsigned int) statePtr);

    if (channelTypeVersion == TLS_CHANNEL_VERSION_1) {
	/*
	 * Remove event handler to underlying channel, this could
	 * be because we are closing for real, or being "unstacked".
	 */

	Tcl_DeleteChannelHandler(Tls_GetParent(statePtr),
		TlsChannelHandler, (ClientData) statePtr);
    }

    Tls_Clean(statePtr);
    Tcl_EventuallyFree((ClientData)statePtr, Tls_Free);
    return TCL_OK;
}

/*
 *-------------------------------------------------------------------
 *
 * TlsInputProc --
 *
 *	This procedure is invoked by the generic IO level
 *       to read input from a SSL socket based channel.
 *
 * Results:
 *	The number of bytes read is returned or -1 on error. An output
 *	argument contains the POSIX error code on error, or zero if no
 *	error occurred.
 *
 * Side effects:
 *	Reads input from the input device of the channel.
 *
 *-------------------------------------------------------------------
 */

static int
TlsInputProc(ClientData instanceData,	/* Socket state. */
	char *buf,			/* Where to store data read. */
	int bufSize,			/* How much space is available
					 * in the buffer? */
	int *errorCodePtr)		/* Where to store error code. */
{
    State *statePtr = (State *) instanceData;
    int bytesRead;			/* How many bytes were read? */

    *errorCodePtr = 0;

    dprintf(stderr,"\nBIO_read(%d)", bufSize);

    if (statePtr->flags & TLS_TCL_CALLBACK) {
       /* don't process any bytes while verify callback is running */
       bytesRead = 0;
       goto input;
    }

    if (!SSL_is_init_finished(statePtr->ssl)) {
	bytesRead = Tls_WaitForConnect(statePtr, errorCodePtr);
	if (bytesRead <= 0) {
	    if (*errorCodePtr == ECONNRESET) {
		/* Soft EOF */
		*errorCodePtr = 0;
		bytesRead = 0;
	    }
	    goto input;
	}
    }
    if (statePtr->flags & TLS_TCL_INIT) {
	statePtr->flags &= ~(TLS_TCL_INIT);
    }
    /*
     * We need to clear the SSL error stack now because we sometimes reach
     * this function with leftover errors in the stack.  If BIO_read
     * returns -1 and intends EAGAIN, there is a leftover error, it will be
     * misconstrued as an error, not EAGAIN.
     *
     * Alternatively, we may want to handle the <0 return codes from
     * BIO_read specially (as advised in the RSA docs).  TLS's lower level BIO
     * functions play with the retry flags though, and this seems to work
     * correctly.  Similar fix in TlsOutputProc. - hobbs
     */
    ERR_clear_error();
    bytesRead = BIO_read(statePtr->bio, buf, bufSize);
    dprintf(stderr,"\nBIO_read -> %d", bytesRead);

    if (bytesRead < 0) {
	int err = SSL_get_error(statePtr->ssl, bytesRead);

	if (err == SSL_ERROR_SSL) {
	    Tls_Error(statePtr, SSL_ERROR(statePtr->ssl, bytesRead));
	    *errorCodePtr = ECONNABORTED;
	} else if (BIO_should_retry(statePtr->bio)) {
	    dprintf(stderr,"RE! ");
	    *errorCodePtr = EAGAIN;
	} else {
	    *errorCodePtr = Tcl_GetErrno();
	    if (*errorCodePtr == ECONNRESET) {
		/* Soft EOF */
		*errorCodePtr = 0;
		bytesRead = 0;
	    }
	}
    }
    input:
    dprintf(stderr, "\nInput(%d) -> %d [%d]", bufSize, bytesRead, *errorCodePtr);
    return bytesRead;
}

/*
 *-------------------------------------------------------------------
 *
 * TlsOutputProc --
 *
 *	This procedure is invoked by the generic IO level
 *       to write output to a SSL socket based channel.
 *
 * Results:
 *	The number of bytes written is returned. An output argument is
 *	set to a POSIX error code if an error occurred, or zero.
 *
 * Side effects:
 *	Writes output on the output device of the channel.
 *
 *-------------------------------------------------------------------
 */

static int
TlsOutputProc(ClientData instanceData,	/* Socket state. */
              CONST char *buf,		/* The data buffer. */
              int toWrite,		/* How many bytes to write? */
              int *errorCodePtr)	/* Where to store error code. */
{
    State *statePtr = (State *) instanceData;
    int written, err;

    *errorCodePtr = 0;

    dprintf(stderr,"\nBIO_write(0x%x, %d)", (unsigned int) statePtr, toWrite);

    if (statePtr->flags & TLS_TCL_CALLBACK) {
       /* don't process any bytes while verify callback is running */
       written = -1;
       *errorCodePtr = EAGAIN;
       goto output;
    }

    if (!SSL_is_init_finished(statePtr->ssl)) {
	written = Tls_WaitForConnect(statePtr, errorCodePtr);
	if (written <= 0) {
	    goto output;
	}
    }
    if (statePtr->flags & TLS_TCL_INIT) {
	statePtr->flags &= ~(TLS_TCL_INIT);
    }
    if (toWrite == 0) {
	dprintf(stderr, "zero-write\n");
	BIO_flush(statePtr->bio);
	written = 0;
	goto output;
    } else {
	/*
	 * We need to clear the SSL error stack now because we sometimes reach
	 * this function with leftover errors in the stack.  If BIO_write
	 * returns -1 and intends EAGAIN, there is a leftover error, it will be
	 * misconstrued as an error, not EAGAIN.
	 *
	 * Alternatively, we may want to handle the <0 return codes from
	 * BIO_write specially (as advised in the RSA docs).  TLS's lower level
	 * BIO functions play with the retry flags though, and this seems to
	 * work correctly.  Similar fix in TlsInputProc. - hobbs
	 */
	ERR_clear_error();
	written = BIO_write(statePtr->bio, buf, toWrite);
	dprintf(stderr,"\nBIO_write(0x%x, %d) -> [%d]",
		(unsigned int) statePtr, toWrite, written);
    }
    if (written <= 0) {
	switch ((err = SSL_get_error(statePtr->ssl, written))) {
	    case SSL_ERROR_NONE:
		if (written < 0) {
		    written = 0;
		}
		break;
	    case SSL_ERROR_WANT_WRITE:
		dprintf(stderr," write W BLOCK");
		break;
	    case SSL_ERROR_WANT_READ:
		dprintf(stderr," write R BLOCK");
		break;
	    case SSL_ERROR_WANT_X509_LOOKUP:
		dprintf(stderr," write X BLOCK");
		break;
	    case SSL_ERROR_ZERO_RETURN:
		dprintf(stderr," closed\n");
		written = 0;
		break;
	    case SSL_ERROR_SYSCALL:
		*errorCodePtr = Tcl_GetErrno();
		dprintf(stderr," [%d] syscall errr: %d",
			written, *errorCodePtr);
		written = -1;
		break;
	    case SSL_ERROR_SSL:
		Tls_Error(statePtr, SSL_ERROR(statePtr->ssl, written));
		*errorCodePtr = ECONNABORTED;
		written = -1;
		break;
	    default:
		dprintf(stderr," unknown err: %d\n", err);
		break;
	}
    }
    output:
    dprintf(stderr, "\nOutput(%d) -> %d", toWrite, written);
    return written;
}

/*
 *-------------------------------------------------------------------
 *
 * TlsGetOptionProc --
 *
 *	Computes an option value for a SSL socket based channel, or a
 *	list of all options and their values.
 *
 * Results:
 *	A standard Tcl result. The value of the specified option or a
 *	list of all options and	their values is returned in the
 *	supplied DString.
 *
 * Side effects:
 *	None.
 *
 *-------------------------------------------------------------------
 */
static int
TlsGetOptionProc(ClientData instanceData,	/* Socket state. */
	Tcl_Interp *interp,		/* For errors - can be NULL. */
	CONST84 char *optionName,	/* Name of the option to
					 * retrieve the value for, or
					 * NULL to get all options and
					 * their values. */
	Tcl_DString *dsPtr)		/* Where to store the computed value
					 * initialized by caller. */
{
    State *statePtr = (State *) instanceData;

    if (channelTypeVersion == TLS_CHANNEL_VERSION_2) {
	Tcl_Channel downChan = Tls_GetParent(statePtr);
	Tcl_DriverGetOptionProc *getOptionProc;

	getOptionProc = Tcl_ChannelGetOptionProc(Tcl_GetChannelType(downChan));
	if (getOptionProc != NULL) {
	    return (*getOptionProc)(Tcl_GetChannelInstanceData(downChan),
		    interp, optionName, dsPtr);
	} else if (optionName == (char*) NULL) {
	    /*
	     * Request is query for all options, this is ok.
	     */
	    return TCL_OK;
	}
	/*
	 * Request for a specific option has to fail, we don't have any.
	 */
	return TCL_ERROR;
    } else {
	size_t len = 0;

	if (optionName != (char *) NULL) {
	    len = strlen(optionName);
	}
#if 0
	if ((len == 0) || ((len > 1) && (optionName[1] == 'c') &&
		(strncmp(optionName, "-cipher", len) == 0))) {
	    if (len == 0) {
		Tcl_DStringAppendElement(dsPtr, "-cipher");
	    }
	    Tcl_DStringAppendElement(dsPtr, SSL_get_cipher(statePtr->ssl));
	    if (len) {
		return TCL_OK;
	    }
	}
#endif
	return TCL_OK;
    }
}

/*
 *-------------------------------------------------------------------
 *
 * TlsWatchProc --
 *
 *	Initialize the notifier to watch Tcl_Files from this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Sets up the notifier so that a future event on the channel
 *	will be seen by Tcl.
 *
 *-------------------------------------------------------------------
 */

static void
TlsWatchProc(ClientData instanceData,	/* The socket state. */
             int mask)			/* Events of interest; an OR-ed
                                         * combination of TCL_READABLE,
                                         * TCL_WRITABLE and TCL_EXCEPTION. */
{
    State *statePtr = (State *) instanceData;

    dprintf(stderr, "TlsWatchProc(0x%x)\n", mask);

    /* Pretend to be dead as long as the verify callback is running. 
     * Otherwise that callback could be invoked recursively. */
    if (statePtr->flags & TLS_TCL_CALLBACK) { return; }

    if (channelTypeVersion == TLS_CHANNEL_VERSION_2) {
	Tcl_Channel     downChan;

	statePtr->watchMask = mask;

	/* No channel handlers any more. We will be notified automatically
	 * about events on the channel below via a call to our
	 * 'TransformNotifyProc'. But we have to pass the interest down now.
	 * We are allowed to add additional 'interest' to the mask if we want
	 * to. But this transformation has no such interest. It just passes
	 * the request down, unchanged.
	 */

	downChan = Tls_GetParent(statePtr);

	(Tcl_GetChannelType(downChan))
	    ->watchProc(Tcl_GetChannelInstanceData(downChan), mask);

	/*
	 * Management of the internal timer.
	 */

	if (statePtr->timer != (Tcl_TimerToken) NULL) {
	    Tcl_DeleteTimerHandler(statePtr->timer);
	    statePtr->timer = (Tcl_TimerToken) NULL;
	}
	if ((mask & TCL_READABLE) && Tcl_InputBuffered(statePtr->self) > 0) {
	    /*
	     * There is interest in readable events and we actually have
	     * data waiting, so generate a timer to flush that.
	     */
	    statePtr->timer = Tcl_CreateTimerHandler(TLS_TCL_DELAY,
		    TlsChannelHandlerTimer, (ClientData) statePtr);
	}
    } else {
	if (mask == statePtr->watchMask)
	    return;

	if (statePtr->watchMask) {
	    /*
	     * Remove event handler to underlying channel, this could
	     * be because we are closing for real, or being "unstacked".
	     */

	    Tcl_DeleteChannelHandler(Tls_GetParent(statePtr),
		    TlsChannelHandler, (ClientData) statePtr);
	}
	statePtr->watchMask = mask;
	if (statePtr->watchMask) {
	    /*
	     * Setup active monitor for events on underlying Channel.
	     */

	    Tcl_CreateChannelHandler(Tls_GetParent(statePtr),
		    statePtr->watchMask, TlsChannelHandler,
		    (ClientData) statePtr);
	}
    }
}

/*
 *-------------------------------------------------------------------
 *
 * TlsGetHandleProc --
 *
 *	Called from Tcl_GetChannelFile to retrieve o/s file handler
 *	from the SSL socket based channel.
 *
 * Results:
 *	The appropriate Tcl_File or NULL if not present. 
 *
 * Side effects:
 *	None.
 *
 *-------------------------------------------------------------------
 */
static int
TlsGetHandleProc(ClientData instanceData,	/* The socket state. */
                 int direction,		/* Which Tcl_File to retrieve? */
                 ClientData *handlePtr)	/* Where to store the handle.  */
{
    State *statePtr = (State *) instanceData;

    return Tcl_GetChannelHandle(Tls_GetParent(statePtr), direction, handlePtr);
}

/*
 *-------------------------------------------------------------------
 *
 * TlsNotifyProc --
 *
 *	Handler called by Tcl to inform us of activity
 *	on the underlying channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May process the incoming event by itself.
 *
 *-------------------------------------------------------------------
 */

static int
TlsNotifyProc(instanceData, mask)
    ClientData	   instanceData; /* The state of the notified transformation */
    int		   mask;       /* The mask of occuring events */
{
    State *statePtr = (State *) instanceData;

    /*
     * An event occured in the underlying channel.  This
     * transformation doesn't process such events thus returns the
     * incoming mask unchanged.
     */

    if (statePtr->timer != (Tcl_TimerToken) NULL) {
	/*
	 * Delete an existing timer. It was not fired, yet we are
	 * here, so the channel below generated such an event and we
	 * don't have to. The renewal of the interest after the
	 * execution of channel handlers will eventually cause us to
	 * recreate the timer (in WatchProc).
	 */

	Tcl_DeleteTimerHandler(statePtr->timer);
	statePtr->timer = (Tcl_TimerToken) NULL;
    }

    if (statePtr->flags & TLS_TCL_CALLBACK) {
	return 0;
    }

    if (statePtr->flags & TLS_TCL_INIT
	    && !SSL_is_init_finished(statePtr->ssl)) {
	int errorCode;
	if (Tls_WaitForConnect(statePtr, &errorCode) <= 0
		&& errorCode == EAGAIN) {
	    return 0;
	}
    }

    return mask;
}

/*
 *------------------------------------------------------*
 *
 *      TlsChannelHandler --
 *
 *      ------------------------------------------------*
 *      Handler called by Tcl as a result of
 *      Tcl_CreateChannelHandler - to inform us of activity
 *      on the underlying channel.
 *      ------------------------------------------------*
 *
 *      Sideeffects:
 *              May generate subsequent calls to
 *              Tcl_NotifyChannel.
 *
 *      Result:
 *              None.
 *
 *------------------------------------------------------*
 */

static void
TlsChannelHandler (clientData, mask)
    ClientData     clientData;
    int            mask;
{
    State *statePtr = (State *) clientData;

dprintf(stderr, "HANDLER(0x%x)\n", mask);
    Tcl_Preserve( (ClientData)statePtr);

    if (mask & TCL_READABLE) {
	BIO_set_flags(statePtr->p_bio, BIO_FLAGS_READ);
    } else {
	BIO_clear_flags(statePtr->p_bio, BIO_FLAGS_READ);
    }

    if (mask & TCL_WRITABLE) {
	BIO_set_flags(statePtr->p_bio, BIO_FLAGS_WRITE);
    } else {
	BIO_clear_flags(statePtr->p_bio, BIO_FLAGS_WRITE);
    }

    mask = 0;
    if (BIO_wpending(statePtr->bio)) {
	mask |= TCL_WRITABLE;
    }
    if (BIO_pending(statePtr->bio)) {
	mask |= TCL_READABLE;
    }

    /*
     * The following NotifyChannel calls seems to be important, but
     * we don't know why.  It looks like if the mask is ever non-zero
     * that it will enter an infinite loop.
     *
     * Notify the upper channel of the current BIO state so the event
     * continues to propagate up the chain.
     *
     * stanton: It looks like this could result in an infinite loop if
     * the upper channel doesn't cause ChannelHandler to be removed
     * before Tcl_NotifyChannel calls channel handlers on the lower channel.
     */
    
    Tcl_NotifyChannel(statePtr->self, mask);
    
    if (statePtr->timer != (Tcl_TimerToken)NULL) {
	Tcl_DeleteTimerHandler(statePtr->timer);
	statePtr->timer = (Tcl_TimerToken)NULL;
    }
    if ((mask & TCL_READABLE) && Tcl_InputBuffered(statePtr->self) > 0) {
	/*
	 * Data is waiting, flush it out in short time
	 */
	statePtr->timer = Tcl_CreateTimerHandler(TLS_TCL_DELAY,
		TlsChannelHandlerTimer, (ClientData) statePtr);
    }
    Tcl_Release( (ClientData)statePtr);
}

/*
 *------------------------------------------------------*
 *
 *	TlsChannelHandlerTimer --
 *
 *	------------------------------------------------*
 *	Called by the notifier (-> timer) to flush out
 *	information waiting in channel buffers.
 *	------------------------------------------------*
 *
 *	Sideeffects:
 *		As of 'TlsChannelHandler'.
 *
 *	Result:
 *		None.
 *
 *------------------------------------------------------*
 */

static void
TlsChannelHandlerTimer (clientData)
ClientData clientData; /* Transformation to query */
{
    State *statePtr = (State *) clientData;
    int mask = 0;

    statePtr->timer = (Tcl_TimerToken) NULL;

    if (BIO_wpending(statePtr->bio)) {
	mask |= TCL_WRITABLE;
    }
    if (BIO_pending(statePtr->bio)) {
	mask |= TCL_READABLE;
    }
    Tcl_NotifyChannel(statePtr->self, mask);
}

/*
 *------------------------------------------------------*
 *
 *	Tls_WaitForConnect --
 *
 *	Sideeffects:
 *		Issues SSL_accept or SSL_connect
 *
 *	Result:
 *		None.
 *
 *------------------------------------------------------*
 */
int
Tls_WaitForConnect( statePtr, errorCodePtr)
    State *statePtr;
    int *errorCodePtr;		/* Where to store error code. */
{
    int err;

    dprintf(stderr,"\nWaitForConnect(0x%x)", (unsigned int) statePtr);

    if (statePtr->flags & TLS_TCL_HANDSHAKE_FAILED) {
        /*
         * We choose ECONNRESET over ECONNABORTED here because some server
         * side code, on the wiki for example, sets up a read handler that
         * does a read and if eof closes the channel. There is no catch/try
         * around the reads so exceptions will result in potentially many
         * dangling channels hanging around that should have been closed.
         * (Backgroun: ECONNABORTED maps to a Tcl exception and 
         * ECONNRESET maps to graceful EOF).
         */
        *errorCodePtr = ECONNRESET;
        return -1;
    }

    for (;;) {
	/* Not initialized yet! */
	if (statePtr->flags & TLS_TCL_SERVER) {
	    err = SSL_accept(statePtr->ssl);
	} else {
	    err = SSL_connect(statePtr->ssl);
	}
	/*SSL_write(statePtr->ssl, (char*)&err, 0);	HACK!!! */
	if (err > 0) {
	    BIO_flush(statePtr->bio);
	}

	if (err <= 0) {
	    int rc = SSL_get_error(statePtr->ssl, err);

	    if (rc == SSL_ERROR_SSL) {
		Tls_Error(statePtr,
			(char *)ERR_reason_error_string(ERR_get_error()));
                statePtr->flags |= TLS_TCL_HANDSHAKE_FAILED;
		*errorCodePtr = ECONNABORTED;
		return -1;
	    } else if (BIO_should_retry(statePtr->bio)) {
		if (statePtr->flags & TLS_TCL_ASYNC) {
		    dprintf(stderr,"E! ");
		    *errorCodePtr = EAGAIN;
		    return -1;
		} else {
		    continue;
		}
	    } else if (err == 0) {
		dprintf(stderr,"CR! ");
		*errorCodePtr = ECONNRESET;
		return -1;
	    }
	    if (statePtr->flags & TLS_TCL_SERVER) {
		err = SSL_get_verify_result(statePtr->ssl);
		if (err != X509_V_OK) {
		    Tls_Error(statePtr,
			    (char *)X509_verify_cert_error_string(err));
                    statePtr->flags |= TLS_TCL_HANDSHAKE_FAILED;
		    *errorCodePtr = ECONNABORTED;
		    return -1;
		}
	    }
	    *errorCodePtr = Tcl_GetErrno();
	    dprintf(stderr,"ERR(%d, %d) ", rc, *errorCodePtr);
	    return -1;
	}
	dprintf(stderr,"R0! ");
	return 1;
    }
}

Tcl_Channel
Tls_GetParent( statePtr )
    State *statePtr;
{
    if (channelTypeVersion == TLS_CHANNEL_VERSION_2) {
	return Tcl_GetStackedChannel(statePtr->self);
    } else {
	/* The reason for the existence of this procedure is
	 * the fact that stacking a transform over another
	 * transform will leave our internal pointer unchanged,
	 * and thus pointing to the new transform, and not the
	 * Channel structure containing the saved state of this
	 * transform. This is the price to pay for leaving
	 * Tcl_Channel references intact. The only other solution
	 * is an extension of Tcl_ChannelType with another driver
	 * procedure to notify a Channel about the (un)stacking.
	 *
	 * It walks the chain of Channel structures until it
	 * finds the one pointing having 'ctrl' as instanceData
	 * and then returns the superceding channel to that. (AK)
	 */

	Tcl_Channel self = statePtr->self;
	Tcl_Channel next;

	while ((ClientData) statePtr != Tcl_GetChannelInstanceData (self)) {
	    next = Tcl_GetStackedChannel (self);
	    if (next == (Tcl_Channel) NULL) {
		/* 09/24/1999 Unstacking bug,
		 * found by Matt Newman <matt@sensus.org>.
		 *
		 * We were unable to find the channel structure for this
		 * transformation in the chain of stacked channel. This
		 * means that we are currently in the process of unstacking
		 * it *and* there were some bytes waiting which are now
		 * flushed. In this situation the pointer to the channel
		 * itself already refers to the parent channel we have to
		 * write the bytes into, so we return that.
		 */
		return statePtr->self;
	    }
	    self = next;
	}

	return Tcl_GetStackedChannel (self);
    }
}