Re: [PATCH v3 1/1] iptables: Fix crash on malformed iptables-restore

[Florian Westphal <fw@strlen.de>]

Oliver Ford <ojford@gmail.com> wrote:
> On Fri, May 19, 2017 at 11:04 AM, Florian Westphal <fw@strlen.de> wrote:
> > Oliver Ford <ojford@gmail.com> wrote:
> >> Filter a beginning '--t'. Because the getopt_long function allows abbreviations,
> >> any parameter beginning with '--t' will be treated as '--table'.
> >
> > No, thats not correct:
> > --t is treated as --table.
> > --tfoo is an invalid option.
> > --ttl is ttl.
> >
> > So this:
> >
> >> +                             || !strncmp(param_buffer, "--t", 3)) {
> >>                               xtables_error(PARAMETER_PROBLEM,
> >> +                                     "The -t option (seen in line %u) cannot be "
> >> +                                     "used in ip6tables-restore.\n", line);
> >
> > .. rejects rules like
> >
> > -A INPUT -m ttl --ttl 32
> 
> Would strncmp(param_buffer, "--ta", 4) work? I don't think there are
> any options that begin with --ta other than --table.

That won't catch '--t'.

It will also add trouble later if any module adds an option like --tap,
--tail, --target, etc.

Whats wrong with:

if ((param_buffer[0] == '-' && param_buffer[1] != '-' &&
     strchr(param_buffer, 't') ||
     (!strncmp(param_buffer, "--t", 3) &&
      !strncmp(param_buffer, "--table", strlen(param_buffer)))) {

?