Re: [NSE][patch] Bug in broadcast-dns-service-discovery and dnssd.lua

[Daniel Miller <bonsaiviking () gmail com>]

Hey all,

Djalal's patch fixed the strange results, but the script (and probably
others that use upnp and dnssd libraries) still crashes when run with -6.
The patch in my original message will fix this issue.

Dan

On Thu, Jun 9, 2011 at 8:50 AM, Daniel Miller <bonsaiviking () gmail com>wrote:

> Hey list,
>
> I've been playing with IPv6 scanning, and I discovered a bug when running
> the broadcast-dns-service-discovery script with the -6 flag:
>
> > $ nmap --script broadcast-dns-service-discovery.nse -6 -d
> >
> > Starting Nmap 5.52.IPv6.Beta2 ( http://nmap.org ) at 2011-06-09 08:24 CDT
> > Warning: File ./nmap-services exists, but Nmap is using
> > /usr/local/bin/../share/nmap/nmap-services for security and consistency
> > reasons.  set NMAPDIR=. to give priority to files in your local directory
> > (may affect the other data files too).
> > PORTS: Using top 1000 ports found open (TCP:1000, UDP:0, SCTP:0)
> > --------------- Timing report ---------------
> >  hostgroups: min 1, max 100000
> >  rtt-timeouts: init 1000, min 100, max 10000
> >  max-scan-delay: TCP 1000, UDP 1000, SCTP 1000
> >  parallelism: min 0, max 0
> >  max-retries: 10, host-timeout: 0
> >  min-rate: 0, max-rate: 0
> > ---------------------------------------------
> > NSE: Loaded 1 scripts for scanning.
> > NSE: Starting runlevel 1 (of 1) scan.
> > NSE: Starting broadcast-dns-service-discovery.
> > NSE: Script Pre-scanning.
> > Initiating NSE at 08:24
> > NSE: Finished broadcast-dns-service-discovery.
> > NSE: Finished broadcast-dns-service-discovery.
> > NSE: dns.findNiceAdditional() found zero answers in a response, but got an
> > unexpected flags.replycode
> > NSE: dns.findNiceAdditional() found zero answers in a response, but got an
> > unexpected flags.replycode
> > NSE: dns.findNiceAdditional() found zero answers in a response, but got an
> > unexpected flags.replycode
> > NSE: dns.findNiceAdditional() found zero answers in a response, but got an
> > unexpected flags.replycode
> > NSE: broadcast-dns-service-discovery threw an error!
> > /usr/local/bin/../share/nmap/nselib/dnssd.lua:53: attempt to perform
> > arithmetic on local 'o1' (a nil value)
> > stack traceback:
> >    /usr/local/bin/../share/nmap/nselib/dnssd.lua:53: in function
> > 'ipToNumber'
> >    /usr/local/bin/../share/nmap/nselib/dnssd.lua:62: in function
> > </usr/local/bin/../share/nmap/nselib/dnssd.lua:61>
> >    [C]: in function 'sort'
> >    /usr/local/bin/../share/nmap/nselib/dnssd.lua:392: in function
> > 'queryServices'
> >    ...are/nmap/scripts/broadcast-dns-service-discovery.nse:52: in function
> > <...are/nmap/scripts/broadcast-dns-service-discovery.nse:48>
> >    (tail call): ?
> >
> > Completed NSE at 08:24, 7.25s elapsed
> > NSE: Starting runlevel 1 (of 1) scan.
> > Read from /usr/local/bin/../share/nmap: nmap-services.
> > WARNING: No targets were specified, so 0 hosts scanned.
> > Nmap done: 0 IP addresses (0 hosts up) scanned in 7.61 seconds
>
> So I dug into it and found that dnssd.lua and wsdd.lua both had a custom
> ipCompare function used for sorting IPv4 addresses that couldn't handle IPv6
> addresses. I rewrote them both to use ipOps.compare_ip(), but that function
> couldn't compare IPv4 to IPv6.
>
> Based on some previous work with the Perl Nmap::Parser module, I patched
> ipOps to compare IPv4 to IPv6 by using IPv4-mapped IPv6 addresses. This
> involved adding a new function, ipOps.ip_to_str() that converts addresses to
> an opaque 4- or 16-byte string representation of the address, so that a
> straight string comparison could be done instead of the bit-by-bit
> comparison that was used before. This also simplified the logic for
> performing the proper comparison for the operator given.
>
> The patch also makes a minor change to ntp-monlist to take advantage of
> IPv6 sorting. Even though v4 and v6 addresses can be sorted together now, I
> kept it separate to avoid breaking something, especially since the code
> involves column widths which vary from one to the other.
>
> There was one more issue that I was not able to address: With the patch
> applied, broadcast-dns-service-discovery does not error out, but the results
> it returns are very strange:
>
> > Pre-scan script results:
> > | broadcast-dns-service-discovery:
> > |   ::a00:8cee:0:0
> > |     9/tcp workstation
> > |       Address=192.168.1.14 2002:62be:b3c6:0:211:2fff:fed7:d902
> > |     9/tcp workstation
> > |       Address=192.168.1.17 2002:62be:b3c6:0:224:81fd:fe60:9b3
> > |     9/tcp workstation
> > |       Address=192.168.1.19 fe80:0:0:0:a800:4ff:fe01:a04
> > |     9/tcp workstation
> > |       Address=192.168.1.18 fe80:0:0:0:225:b3ff:fe6c:7986
> > |   ::a00:c3e5:0:0
> > |     22/tcp udisks-ssh
> > |_      Address=192.168.1.18 fe80:0:0:0:225:b3ff:fe6c:7986
> I can't explain those ::a00:XXXX:0:0 addresses. They change every time the
> script is invoked, but the results are always grouped according to
> port/service, rather than IP, as they should be.
>
> Patch attached.
> Dan
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