Re: [iptables PATCH] xshared: Fix response to unprivileged users

[Phil Sutter <phil@nwl.cc>]

Hi Pablo,

On Thu, Jan 27, 2022 at 05:28:39PM +0100, Pablo Neira Ayuso wrote:
> On Thu, Jan 20, 2022 at 11:16:53AM +0100, Phil Sutter wrote:
> > Expected behaviour in both variants is:
> > 
> > * Print help without error, append extension help if -m and/or -j
> >   options are present
> > * Indicate lack of permissions in an error message for anything else
> > 
> > With iptables-nft, this was broken basically from day 1. Shared use of
> > do_parse() then somewhat broke legacy: it started complaining about
> > inability to create a lock file.
> > 
> > Fix this by making iptables-nft assume extension revision 0 is present
> > if permissions don't allow to verify. This is consistent with legacy.
> > 
> > Second part is to exit directly after printing help - this avoids having
> > to make the following code "nop-aware" to prevent privileged actions.
> 
> On top of this patch, it should be possible to allow for some
> nfnetlink command to be used from unpriviledged process.
> 
> I'm attaching a sketch patch, it skips module autoload which is should
> not be triggered by an unpriviledged process.
> 
> This should allow for better help with -m/-j if the module is present.

That's interesting. What's the use-case? With my patch, extension help
text printing works fine as unprivileged user. Does it allow to drop the
"revision == 0 && EPERM" hack?

Thanks, Phil