libvncserver: don't give invalid fds to FD_* macros

re #655

Author: bk138

src/libvncserver/rfbserver.c

@@ -1575,6 +1575,10 @@ rfbBool rfbSendFileTransferChunk(rfbClientPtr cl)
     /* If not sending, or no file open...   Return as if we sent something! */
     if ((cl->fileTransfer.fd!=-1) && (cl->fileTransfer.sending==1))
     {
+        if(cl->sock == RFB_INVALID_SOCKET) {
+            errno = EBADF;
+            return FALSE;
+        }
 	FD_ZERO(&wfds);
         FD_SET(cl->sock, &wfds);
 

src/libvncserver/sockets.c

@@ -672,6 +672,10 @@ rfbReadExactTimeout(rfbClientPtr cl, char* buf, int len, int timeout)
     struct timeval tv;
 
     while (len > 0) {
+        if(sock == RFB_INVALID_SOCKET) {
+            errno = EBADF;
+            return -1;
+        }
 #ifdef LIBVNCSERVER_WITH_WEBSOCKETS
         if (cl->wsctx) {
             n = webSocketsDecode(cl, buf, len);
@@ -772,6 +776,10 @@ rfbPeekExactTimeout(rfbClientPtr cl, char* buf, int len, int timeout)
     struct timeval tv;
 
     while (len > 0) {
+        if(sock == RFB_INVALID_SOCKET) {
+            errno = EBADF;
+            return -1;
+        }
 #ifdef LIBVNCSERVER_WITH_WEBSOCKETS
 	if (cl->sslctx)
 	    n = rfbssl_peek(cl, buf, len);
@@ -888,6 +896,10 @@ rfbWriteExact(rfbClientPtr cl,
 
     LOCK(cl->outputMutex);
     while (len > 0) {
+        if(sock == RFB_INVALID_SOCKET) {
+            errno = EBADF;
+            return -1;
+        }
 #ifdef LIBVNCSERVER_WITH_WEBSOCKETS
         if (cl->sslctx)
 	    n = rfbssl_write(cl, buf, len);