Re: Checking non-privileged access to port < 1024

[David Fifield <david () bamsoftware com>]

On Thu, Apr 29, 2010 at 06:05:41AM -1000, William Pursell wrote:
> I've recently discovered ncat.  A very nice replacement
> for the venerable nc.  Thanks to all who have
> contributed to make ncat happen.
>
> One observation, best shown with a patch:
>
> diff --git a/ncat/ncat_main.c b/ncat/ncat_main.c
> index 2e05bd7..859dfd0 100644
> --- a/ncat/ncat_main.c
> +++ b/ncat/ncat_main.c
> @@ -716,10 +716,6 @@ static int ncat_listen_mode(void) {
>      if (o.idletimeout != 0)
>          bye("An idle timeout only works in connect mode.");
>
> -    /* If a non-root user tries to bind to a privileged port, Exit. */
> -    if (o.portno < 1024 && !ncat_checkuid())
> -        bye("Attempted a non-root bind() to a port <1024.");
> -
>      if (o.broker && o.cmdexec != NULL)
>          bye("Invalid option combination: --broker and -e.");
>
>
>
> It strikes me as inelegant to have the application check
> whether or not bind will fail.  If the user doesn't
> have access, then let bind fail.

You're absolutely right. I removed that code and now the error message
looks like this:

$ ./ncat -l 345
Ncat: bind to 0.0.0.0:345: Permission denied. QUITTING.

David Fifield
_______________________________________________
Sent through the nmap-dev mailing list
http://cgi.insecure.org/mailman/listinfo/nmap-dev
Archived at http://seclists.org/nmap-dev/