user/2436: nc(1) reports wrong error message

[Alexander Yurchenko <grange@rt.mipt.ru>]

>Number:         2436
>Category:       user
>Synopsis:       nc(1) reports wrong error message
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bugs
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Tue Feb 26 12:00:03 MST 2002
>Last-Modified:
>Originator:     Alexander Yurchenko
>Organization:
>Release:        3.0-current
>Environment:
	System      : OpenBSD 3.0-current
	Architecture: OpenBSD.i386
	Machine     : i386
>Description:
An experiment:

$ nc -l 555
nc: Bad file descriptor

I think the real reason of the failure is that non-root process can't bind
privileged port and isn't that something's wrong with file descriptor.

The problem is here:
netcat.c:408
                if (bind(s, (struct sockaddr *)res0->ai_addr,
                    res0->ai_addrlen) == 0)
                        break;

                close(s);
                s = -1;
        } while ((res0 = res0->ai_next) != NULL);

        if (!uflag) {
                if (listen(s, 1) < 0)
                        errx(1, "%s", strerror(errno));
        }

If bind() fails socket will be -1 and then listen() will be called with
wittingly bad file descriptor.

>How-To-Repeat:
Run as non-root
nc -l 555

>Fix:
Index: src/usr.bin/nc/netcat.c
===================================================================
RCS file: /home/cvsup/OpenBSD/src/usr.bin/nc/netcat.c,v
retrieving revision 1.45
diff -u -r1.45 netcat.c
--- src/usr.bin/nc/netcat.c     19 Feb 2002 22:42:04 -0000      1.45
+++ src/usr.bin/nc/netcat.c     26 Feb 2002 12:37:56 -0000
@@ -506,7 +506,7 @@
                s = -1;
        } while ((res0 = res0->ai_next) != NULL);
 
-       if (!uflag) {
+       if (!uflag && s != -1) {
                if (listen(s, 1) < 0)
                        errx(1, "%s", strerror(errno));
        }


After patch applied:
$ nc -l 555
nc: Permission denied

That's more presice error message IMHO.

>Audit-Trail:
>Unformatted: