Re: [nmap-svn] r31378 - nmap-exp/d33tah/ncat-env-conninfo/ncat

[Henri Doreau <henri.doreau () gmail com>]

2013/7/17 d33 tah <d33tah () gmail com>:
> Hi Henri,
>
> > > +    *env = (LPTSTR) safe_realloc(*env, *env_size+added_value_len);
> > > +
> > > +    Snprintf(*env + *env_size-1, added_value_len, "%s=%s", name, value);
> > > +
> > > +    *env_size += added_value_len;
> > > +    (*env)[*env_size] = '\0';
> > > +    (*env)[*env_size-1] = '\0';
> > Why do you zero the last *two* indices? Safety? You might want to
> > check/use Snprintf return value too.
>
> As Windows MSDN docs say, the environment description string contains
> a NULL-separated array of key=value strings. Its ending is marked by
> two NULL bytes - probably one for the end of string, and another to
> make next string zero-bytes long.
Thanks, I see.

> > > +}
> > > +
> > > +static void setup_environment(struct fdinfo *info, LPTSTR* env, int *env_size)
> > > +{
> > > +    char *dest_addr=NULL;
> > > +    char dest_port[10];
> > > +    union sockaddr_u su;
> > > +    unsigned short port;
> > > +    char str[16];
> > > +    char ip[4 * INET6_ADDRSTRLEN];
> > Why is ip 4*INET6_ADDRSTRLEN?
>
> No idea really. I copied it from here (line 1821):
> http://git.savannah.gnu.org/cgit/inetutils.git/tree/src/inetd.c
> I'll do some digging about what kind of buffers Ncat uses to represent
> IP's - if you know the answer already, I'd be happy to hear it.
There's a comment in inetd.c, according to which this
4*INET6_ADDRSTRLEN is a tradeoff between space and official max
hostname length (in their code, the buffer is susceptible to handle a
hostname too). I believe that INET6_ADDRSTRLEN is big enough in your
case, because you're requesting NI_NUMERICHOST and the getnameinfo
which is provided by nbase doesn't support IPv6... Why I'm insisting
on that is because this strange constant makes code hard to understand
("why 4 times something already larger than needed?"). I wouldn't want
that to end up being a line that noone dares touching, labeled with a
comment like: /* XXX: isn't this too big? */ :)

Finally, and way more important than sizing a buffer, please pay
attention to licensing issues. Nmap license isn't compatible with
GPLv3. I think BSD code is Ok (looks like this inetutils file has
both) but IIRC the BSD header has to be reproduced then. I let fyodor
or someone confirm but you might want to rewrite this code.

Regards

--
Henri
_______________________________________________
Sent through the dev mailing list
http://nmap.org/mailman/listinfo/dev
Archived at http://seclists.org/nmap-dev/