Handle cases of no tunnels and no auth types for TightVNC

nselib/vnc.lua

@@ -377,32 +377,42 @@ VNC = {
       return false, "Failed to get number of tunnels"
     end
     local pos, ntunnels = bin.unpack(">I", buf)
+    local tight = {
+      tunnels = {},
+      types = {}
+    }
+    if ntunnels > 0 then
       status, buf = self.socket:receive_buf(match.numbytes(16 * ntunnels), true)
       if not status then
         return false, "Failed to get list of tunnels"
       end
 
+      local have_none_tunnel = false
       pos = 1
-    local tight = {
-      tunnels = {},
-      types = {}
-    }
       for i=1, ntunnels do
         local tunnel = {}
         pos, tunnel.code, tunnel.vendor, tunnel.signature = bin.unpack(">IA4A8", buf, pos)
+        if tunnel.code == 0 then
+          have_none_tunnel = true
+        end
         tight.tunnels[#tight.tunnels+1] = tunnel
       end
 
-    if ntunnels > 0 then
+      if have_none_tunnel then
+        -- Try the "NOTUNNEL" tunnel, for simplicity, if it's available.
+        self.socket:send(bin.pack(">I", 0))
+      else
         -- for now, just return the first one. TODO: choose a supported tunnel type
         self.socket:send(bin.pack(">I", tight.tunnels[1].code))
       end
+    end
 
     status, buf = self.socket:receive_buf(match.numbytes(4), true)
     if not status then
       return false, "Failed to get number of Tight auth types"
     end
     local pos, nauth = bin.unpack(">I", buf)
+    if nauth > 0 then
       status, buf = self.socket:receive_buf(match.numbytes(16 * nauth), true)
       if not status then
         return false, "Failed to get list of Tight auth types"
@@ -414,6 +424,7 @@ VNC = {
         pos, auth.code, auth.vendor, auth.signature = bin.unpack(">IA4A8", buf, pos)
         tight.types[#tight.types+1] = auth
       end
+    end
 
     self.tight = tight