libtdevnc/libvncserver/auth.c

/*
 * auth.c - deal with authentication.
 *
 * This file implements the VNC authentication protocol when setting up an RFB
 * connection.
 */

/*
 *  Copyright (C) 2005 Rohit Kumar, Johannes E. Schindelin
 *  OSXvnc Copyright (C) 2001 Dan McGuirk <mcguirk@incompleteness.net>.
 *  Original Xvnc code Copyright (C) 1999 AT&T Laboratories Cambridge.  
 *  All Rights Reserved.
 *
 *  This is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This software is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this software; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
 *  USA.
 */

#include <rfb/rfb.h>

/*
 * Handle security types
 */

static rfbSecurityHandler* securityHandlers = NULL;

void
rfbRegisterSecurityHandler(rfbSecurityHandler* handler)
{
	rfbSecurityHandler* last = handler;

	while(last->next)
		last = last->next;

	last->next = securityHandlers;
	securityHandlers = handler;
}


/*
 * Send the authentication challenge.
 */

static void
rfbVncAuthSendChallenge(rfbClientPtr cl)
{
	
    /* 4 byte header is alreay sent. Which is rfbSecTypeVncAuth 
       (same as rfbVncAuth). Just send the challenge. */
    rfbRandomBytes(cl->authChallenge);
    if (rfbWriteExact(cl, (char *)cl->authChallenge, CHALLENGESIZE) < 0) {
        rfbLogPerror("rfbAuthNewClient: write");
        rfbCloseClient(cl);
        return;
    }
    
    /* Dispatch client input to rfbVncAuthProcessResponse. */
    cl->state = RFB_AUTHENTICATION;
}


/*
 * Advertise the supported security types (protocol 3.7). Here before sending 
 * the list of security types to the client one more security type is added 
 * to the list if primaryType is not set to rfbSecTypeInvalid. This security
 * type is the standard vnc security type which does the vnc authentication
 * or it will be security type for no authentication.
 * Different security types will be added by applications using this library.
 */

static void
rfbSendSecurityTypeList(rfbClientPtr cl, int primaryType)
{
    /* The size of the message is the count of security types +1,
     * since the first byte is the number of types. */
    int size = 1;
    rfbSecurityHandler* handler;
#define MAX_SECURITY_TYPES 255
    uint8_t buffer[MAX_SECURITY_TYPES+1];

    /* Fill in the list of security types in the client structure. */
    if (primaryType != rfbSecTypeInvalid) {
	rfbSecurityHandler* handler = calloc(sizeof(rfbSecurityHandler),1);
	handler->type = primaryType;
	handler->handler = rfbVncAuthSendChallenge;
	handler->next = NULL;
	rfbRegisterSecurityHandler(handler);
    }

    for (handler = securityHandlers;
	    handler && size<MAX_SECURITY_TYPES; handler = handler->next) {
	buffer[size] = handler->type;
	size++;
    }
    buffer[0] = (unsigned char)size-1;

    /* Send the list. */
    if (rfbWriteExact(cl, (char *)buffer, size) < 0) {
	rfbLogPerror("rfbSendSecurityTypeList: write");
	rfbCloseClient(cl);
	return;
    }

    /*
      * if count is 0, we need to send the reason and close the connection.
      */
    if(size <= 1) {
	/* This means total count is Zero and so reason msg should be sent */
	/* The execution should never reach here */
	char* reason = "No authentication mode is registered!";

	rfbClientConnFailed(cl, reason);
	return;
    }

    /* Dispatch client input to rfbProcessClientSecurityType. */
    cl->state = RFB_SECURITY_TYPE;
}




/*
 * Tell the client what security type will be used (protocol 3.3).
 */
static void
rfbSendSecurityType(rfbClientPtr cl, int32_t securityType)
{
    uint32_t value32;

    /* Send the value. */
    value32 = Swap32IfLE(securityType);
    if (rfbWriteExact(cl, (char *)&value32, 4) < 0) {
	rfbLogPerror("rfbSendSecurityType: write");
	rfbCloseClient(cl);
	return;
    }

    /* Decide what to do next. */
    switch (securityType) {
    case rfbSecTypeNone:
	/* Dispatch client input to rfbProcessClientInitMessage. */
	cl->state = RFB_INITIALISATION;
	break;
    case rfbSecTypeVncAuth:
	/* Begin the standard VNC authentication procedure. */
	rfbVncAuthSendChallenge(cl);
	break;
    default:
	/* Impossible case (hopefully). */
	rfbLogPerror("rfbSendSecurityType: assertion failed");
	rfbCloseClient(cl);
    }
}



/*
 * rfbAuthNewClient is called right after negotiating the protocol
 * version. Depending on the protocol version, we send either a code
 * for authentication scheme to be used (protocol 3.3), or a list of
 * possible "security types" (protocol 3.7).
 */

void
rfbAuthNewClient(rfbClientPtr cl)
{
    int32_t securityType = rfbSecTypeInvalid;

    if (!cl->screen->authPasswdData || cl->reverseConnection) {
	/* chk if this condition is valid or not. */
	securityType = rfbSecTypeNone;
    } else if (cl->screen->authPasswdData) {
 	    securityType = rfbSecTypeVncAuth;
    }

    if (cl->protocolMinorVersion < 7) {
	/* Make sure we use only RFB 3.3 compatible security types. */
	if (securityType == rfbSecTypeInvalid) {
	    rfbLog("VNC authentication disabled - RFB 3.3 client rejected\n");
	    rfbClientConnFailed(cl, "Your viewer cannot handle required "
				"authentication methods");
	    return;
	}
	rfbSendSecurityType(cl, securityType);
    } else {
	/* Here it's ok when securityType is set to rfbSecTypeInvalid. */
	rfbSendSecurityTypeList(cl, securityType);
    }
}

/*
 * Read the security type chosen by the client (protocol 3.7).
 */

void
rfbProcessClientSecurityType(rfbClientPtr cl)
{
    int n;
    uint8_t chosenType;
    rfbSecurityHandler* handler;

    /* Read the security type. */
    n = rfbReadExact(cl, (char *)&chosenType, 1);
    if (n <= 0) {
	if (n == 0)
	    rfbLog("rfbProcessClientSecurityType: client gone\n");
	else
	    rfbLogPerror("rfbProcessClientSecurityType: read");
	rfbCloseClient(cl);
	return;
    }

    if(chosenType == rfbSecTypeNone) {
       cl->state = RFB_INITIALISATION;
	return;
    }
	

    /* Make sure it was present in the list sent by the server. */
    for (handler = securityHandlers; handler;
	    handler = handler->next)
	if (chosenType == handler->type) {
	    handler->handler(cl);
	    return;
	}

    rfbLog("rfbProcessClientSecurityType: wrong security type requested\n");
    rfbCloseClient(cl);
}



/*
 * rfbAuthProcessClientMessage is called when the client sends its
 * authentication response.
 */

void
rfbAuthProcessClientMessage(rfbClientPtr cl)
{
    int n;
    uint8_t response[CHALLENGESIZE];
    uint32_t authResult;

    if ((n = rfbReadExact(cl, (char *)response, CHALLENGESIZE)) <= 0) {
        if (n != 0)
            rfbLogPerror("rfbAuthProcessClientMessage: read");
        rfbCloseClient(cl);
        return;
    }

    if(!cl->screen->passwordCheck(cl,(const char*)response,CHALLENGESIZE)) {
        rfbErr("rfbAuthProcessClientMessage: password check failed\n");
        authResult = Swap32IfLE(rfbVncAuthFailed);
        if (rfbWriteExact(cl, (char *)&authResult, 4) < 0) {
            rfbLogPerror("rfbAuthProcessClientMessage: write");
        }
        rfbCloseClient(cl);
        return;
    }

    authResult = Swap32IfLE(rfbVncAuthOK);

    if (rfbWriteExact(cl, (char *)&authResult, 4) < 0) {
        rfbLogPerror("rfbAuthProcessClientMessage: write");
        rfbCloseClient(cl);
        return;
    }

    cl->state = RFB_INITIALISATION;
}