Re: Nmap 4.69beta1 assertion failure

[David Fifield <david () bamsoftware com>]

On Mon, Sep 08, 2008 at 07:42:18AM +0200, LevelZero wrote:
> On Sun, 7 Sep 2008 16:17:19 -0600, David Fifield <david () bamsoftware com>
> wrote:
> > On Mon, Sep 08, 2008 at 12:05:13AM +0200, LevelZero wrote:
> > > I was poking around on nmap 4.69beta1 today on my XPSP3 box and while
> > doing
> > > a basic TCP connect scan, I keep getting assertion failures. I tested
> > both
> > > on one of my own boxes and on scanme.nmap.org
> > >
> > > Below a sample output:
> > >
> > > nmap -v -v -v -v -d -d -sT scanme.nmap.org
> > > <parts cut that run normally>
> > > Initiating Connect Scan at 23:53
> > > Scanning scanme.nmap.org (64.13.134.52) [1000 ports]
> > > Discovered open port 53/tcp on 64.13.134.52
> > > Discovered open port 80/tcp on 64.13.134.52
> > > Assertion failed: USI->scantype != CONNECT_SCAN, file ..\scan_engine.cc,
> > > line 2843
> >
> > Can you find lines in the output that start with "Changing ping
> > technique"? If so, please send what they say. You need -d2 or -d -d to
> > see them.
>
> Initiating Ping Scan at 07:39
> Scanning 64.13.134.52 [2 ports]
> Packet capture filter (device eth0): dst host 10.40.85.35 and (icmp or
> ((tcp or udp) and (src host 64.13.134.52)))
> We got a TCP ping packet back from 64.13.134.52 port 80 (trynum = 0)
> ultrascan_host_probe_update called for machine 64.13.134.52 state UNKNOWN
> -> HOST_UP (trynum 0 time: 0)
> Changing ping technique for 64.13.134.52 to tcp to port 80; flags: A
> Completed Ping Scan at 07:39, 0.36s elapsed (1 total hosts)
>
> So indeed, it does change ping technique.

Thanks, you found a bona fide bug, which has now been fixed. The problem
wasn't that the ping technique changed to TCP ACK, that's normal, but
that ping type should have been considered inappropriate for a TCP
connect scan and not been used.

David Fifield

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