Re: [nft PATCH] evaluate: Reject quoted strings containing only wildcard

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Sep 28, 2020 at 10:19:25AM +0200, Phil Sutter wrote:
> On Thu, Sep 24, 2020 at 07:06:39PM +0200, Phil Sutter wrote:
> > Fix for an assertion fail when trying to match against an all-wildcard
> > interface name:
> > 
> > | % nft add rule t c iifname '"*"'
> > | nft: expression.c:402: constant_expr_alloc: Assertion `(((len) + (8) - 1) / (8)) > 0' failed.
> > | zsh: abort      nft add rule t c iifname '"*"'
> > 
> > Fix this by detecting the string in expr_evaluate_string() and returning
> > an error message:
> > 
> > | % nft add rule t c iifname '"*"'
> > | Error: All-wildcard strings are not supported
> > | add rule t c iifname "*"
> > |                      ^^^
> > 
> 
> Note that all this is pretty inconsistent: The above happens only for
> quoted asterisks. Unquoted ones cause a different error (at least no
> assertion fail):
> 
> | % nft add rule t c iifname '*'
> | Error: datatype mismatch, expected network interface name, expression has type integer
> | add rule t c iifname *
> |              ~~~~~~~ ^
> 
> What puzzles me is that we have:
> 
> | wildcard_expr           :       ASTERISK
> |                         {
> |                                 struct expr *expr;
> | 
> |                                 expr = constant_expr_alloc(&@$, &integer_type,
> |                                                            BYTEORDER_HOST_ENDIAN,
> |                                                            0, NULL);
> |                                 $$ = prefix_expr_alloc(&@$, expr, 0);
> |                         }
> |                         ;
> 
> Yet when trying to use it as a prefix, it is rejected:
> 
> | % nft add rule t c ip saddr '*'
> | Error: datatype mismatch, expected IPv4 address, expression has type integer
> | add rule t c ip saddr *
> |              ~~~~~~~~ ^
> 
> So is this wildcard_expr simply broken or didn't I find correct way to use it
> yet?

This looks like some preliminary support for wildcard matching in set
elements, but my impression is that this is broken. I don't remember
to have seen any tests covering this.