Re: [RFC][patch] XML structured script output (Nmap-script-XML as of 15 July)

[Patrick Donnelly <batrick () batbytes com>]

On Fri, Jul 20, 2012 at 11:00 AM, David Fifield <david () bamsoftware com> wrote:
> On Fri, Jul 20, 2012 at 10:54:32AM -0400, Patrick Donnelly wrote:
> > On Thu, Jul 19, 2012 at 7:08 PM, David Fifield <david () bamsoftware com> wrote:
> > > I can deal with the field names being lower-case and identifier-like;
> > > maybe people will even prefer them that way. But the fact that "md5" and
> > > "sha1" are not on adjacent lines is galling. Maybe a special kind of
> > > table format that keeps order (i.e., an array of name-value pairs)? That
> > > would seem to require a higher-level function with which to set output
> > > values.
> >
> > You can get an ordered dictionary in Lua with some metamethod magic:
>
> Right, thanks for that. I don't doubt that it can be done. I'm asking if
> it's a reasonable model for setting script output.

I think so, yes.

> I'm attaching a copy of ssl-cert.nse modified to return a structured
> table. It's the same one used to create the most recent output example
> on the wiki page. This, I think, is about as nice as setting structured
> output is going to get, and it would be nice if this method could
> provide nice ordered output.
>
> -- Convert a cert (which is a kind of userdata object) into a normal Lua table.
> local function to_table(cert)
>     return {
>         subject = cert.subject,
>         issuer = cert.issuer,
>         pubkey = cert.pubkey,
>         validity = cert.validity,
>         md5 = stdnse.tohex(cert:digest("md5")),
>         sha1 = stdnse.tohex(cert:digest("sha1")),
>         -- pem = cert.pem,
>     }
> end

If the table is going to be an ordered dictionary, the above can't be
done within a table constructor as the table keys are set before the
metamethods are set. I think this is just as reasonable:

-- Convert a cert (which is a kind of userdata object) into a normal Lua table.
local function to_table(cert)
    local ordict = stdnse.script_output.ordered_dictionary()
        ordict.subject = cert.subject,
        ordict.issuer = cert.issuer,
        ordict.pubkey = cert.pubkey,
        ordict.validity = cert.validity,
        ordict.md5 = stdnse.tohex(cert:digest("md5")),
        ordict.sha1 = stdnse.tohex(cert:digest("sha1")),
        -- ordict.pem = cert.pem,
end

The ordered dictionary detail can be hidden away if we encourage the
use of some function for constructing output tables (all script output
tables should be ordered dictionaries?).

-- 
- Patrick Donnelly
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