Re: ncat broadcast support?

[Daniel Miller <bonsaiviking () gmail com>]

Well, since my patch applies to the Nsock library instead of just Ncat, 
it probably does affect other things. I figured that checking if the 
connection is to INADDR_BROADCAST would prevent most complications. I'm 
pretty sure we wouldn't want SO_BROADCAST on every socket, since it (I 
think) affects the way the socket receives responses from the network. 
Again, any tips for what interactions to check for or a test suite to 
run would be great.

Dan

On 05/12/2010 09:21 AM, Ron wrote:
> Hey Daniel,
>
> Do you know if this can potentially affect anything else in the application? In other words, is there any reason that we 
> *wouldn't* want SO_BROADCAST on every connection?
>
> If there is, you might want to add a commandline argument --broadcast that sets SO_BROADCAST rather than setting it in every 
> case. But, if there's no side effect, then setting it in every case is probably ok (not that it's my call to make :) ).
>
> Ron
>
> On Wed, 12 May 2010 09:16:50 -0500 Daniel Miller
> <bonsaiviking () gmail com>  wrote:
>    
> > Thanks for the tip, Ron! Here's what I came up with, which works for
> > me for this particular application.
> >
> > --- nmap.orig/nsock/src/nsock_connect.c    2010-05-12
> > 09:09:20.663173832 -0500
> > +++ nmap/nsock/src/nsock_connect.c    2010-05-11 16:32:33.347640392
> > -0500 @@ -120,6 +120,14 @@ void nsock_connect_internal(mspool *ms,
> >          }
> >        }
> >
> > +    if (sin->sin_addr.s_addr == INADDR_BROADCAST) {
> > +      int rval;
> > +      if (setsockopt(iod->sd, SOL_SOCKET, SO_BROADCAST, (void*)
> > &rval, sizeof(int)) == -1) {
> > +        if (ms->tracelevel>  0)
> > +          nsock_trace(ms, "Setting of SO_BROADCAST failed (IOD #%li)
> > EID %li", iod->id, nse->id);
> > +      }
> > +    }
> > +
> >        if (connect(iod->sd, (struct sockaddr *) ss, sslen) == -1) {
> >          int err = socket_errno();
> >
> >
> > I'd like to make it part of the official distribution, but I know I'm
> > missing some critical pieces:
> >
> > 1. I don't think this supports IPv6
> > 2. It will probably do the same thing for TCP, which may break or not
> > work as expected
> > 3. I don't have a good test suite to make sure I didn't break anything
> > 4. I only tested on Ubuntu 10.04 with g++ 4.4.3
> >
> > Any hints as to what my next step would be?
> >
> > Thanks,
> > Dan
> >
> > On 05/11/2010 03:31 PM, Ron wrote:
> >      
> > > I believe what you need to do is find out where it calls Socket()
> > > and add a call to Setsockopt() with SO_BROADCAST set to 1.
> > >
> > > Search udp.c in my nbtool codebase for 'SO_BROADCAST':
> > > http://svn.skullsecurity.org:81/ron/security/nbtool/udp.c
> > >
> > > To see an example.
> > >
> > > Hope that helps!
> > >
> > > On Tue, 11 May 2010 15:00:22 -0500 Daniel Miller
> > > <bonsaiviking () gmail com>   wrote:
> > >
> > >        
> > > > I would like to use ncat in UDP mode to send broadcast datagrams,
> > > > but I get "permission denied" errors, even running as root. I
> > > > understand that there are differences in how to call the
> > > > underlying system calls when connecting to broadcast, and I'm
> > > > willing to attempt a patch, but I don't know where to start. Could
> > > > someone give me a quick pointer to the files I'd have to change to
> > > > get this to work?
> > > >
> > > > doesnotwork# ncat -vvvvv --udp 192.168.1.255 161
> > > > Ncat: Version 5.30BETA1 ( http://nmap.org/ncat )
> > > > NSOCK (0.0010s) UDP connection requested to 255.255.255.255:161
> > > > (IOD
> > > > #1) EID 8
> > > > NSOCK (0.0010s) Callback: CONNECT ERROR [Permission denied (13)]
> > > > for EID 8 [255.255.255.255:161]
> > > > Ncat: Permission denied.
> > > >
> > > > Thanks for any assistance (or "No, that's a bad idea," as the case
> > > > may be)
> > > >
> > > > Dan
> > > > _______________________________________________
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> > > >
> > > >          
> > >
> > >
> > >
> > > _______________________________________________
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> > >        
> > _______________________________________________
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> >      
>
>    
>
>
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