Re: Assertion failure with dns-zone-transfer.nse / tab.lua

[David Fifield <david () bamsoftware com>]

On Sun, Feb 22, 2009 at 07:51:22AM +0000, Brandon Enright wrote:
> A few of our DNS servers are causing the DNS zone transfer script to
> cause tab.lua to error out:
>
> NSE (55.651s): dns-zone-transfer against 132.239.1.52:53 ended with error: 
> /home/bmenrigh/flexmap/nmap/svn/nmap//nselib/tab.lua:45: assertion failed!
>
> I haven't worked on getting a backtrace yet so if the problem isn't
> immediately obvious I'll hack the traceback script up to provide one.
> I might also be able to provide a pcap of the error, depending on the
> privacy of the data contained in the pcap.

I guess that the next call up is

        -- answer domain
        offset, line = parse_domain(data, offset)
        tab.add(table, 1, line)

parse_domain (actually dns.decStr) returns nil when too many pointers
are needed to decompress a message. This is to prevent the infinite
recursion bug. The limit is 3, but maybe that needs to be higher. A
packet capture of the DNS message would be helpful.

David Fifield

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