Re: nmap.bind to set NSE socket source address

[Patrick Donnelly <batrick () batbytes com>]

On Thu, Oct 15, 2009 at 6:45 PM, David Fifield <david () bamsoftware com> wrote:
> The DHCP server in my router sends back a unicast DHCP offer in response
> to DHCPDISCOVER, so it must not be every server that does that.
>
> I think what you would normally do is make a socket bound to
> 255.255.255.255:67 and try to receive on it. In Python this works:
>
> import socket
> s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
> s.bind("255.255.255.255", 67)
> print s.recv()
>
> But that currently won't work in NSE, because the socket descriptor
> isn't created until a connection is attempted. There's no way to create
> a socket without also connecting it. Something about the connection
> keeps the receive from working. This is what I tried:
>
> s = nmap.new_socket()
> assert(s:bind("255.255.255.255", 67))
> assert(s:connect(host.ip, 68, "udp"))
> status, data = s:receive()
>
> So we would have to rearchitect part of Nsock to allocate a socket on
> nsi_new, which I think is pretty reasonable.

Funnily enough, if we do actually assign a socket using nsi_new when
nmap.new_socket is called, we no longer need to have the reconnect_ssl
method. We could simply add the extra case to the connect method.
Perhaps this is worth doing just so we can get rid of that extra
method now, and so bind works before the call to connect?


-- 
-Patrick Donnelly

"Let all men know thee, but no man know thee thoroughly: Men freely
ford that see the shallows."

- Benjamin Franklin

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