linux-kernel - Re: [PATCH ghak124 v3] audit: log nftables configuration change events

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Message-ID: <20200624130304.GA549@salvia>
Date:   Wed, 24 Jun 2020 15:03:04 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        netfilter-devel@...r.kernel.org, Paul Moore <paul@...l-moore.com>,
        sgrubb@...hat.com, omosnace@...hat.com, fw@...len.de,
        twoerner@...hat.com, eparis@...isplace.org, tgraf@...radead.org
Subject: Re: [PATCH ghak124 v3] audit: log nftables configuration change
 events

On Wed, Jun 24, 2020 at 08:34:23AM -0400, Richard Guy Briggs wrote:
> On 2020-06-24 12:03, Pablo Neira Ayuso wrote:
> > On Thu, Jun 04, 2020 at 09:20:49AM -0400, Richard Guy Briggs wrote:
[...]
> > > diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> > > index 3558e76e2733..b9e7440cc87d 100644
> > > --- a/net/netfilter/nf_tables_api.c
> > > +++ b/net/netfilter/nf_tables_api.c
> > > @@ -12,6 +12,7 @@
> > >  #include <linux/netlink.h>
> > >  #include <linux/vmalloc.h>
> > >  #include <linux/rhashtable.h>
> > > +#include <linux/audit.h>
> > >  #include <linux/netfilter.h>
> > >  #include <linux/netfilter/nfnetlink.h>
> > >  #include <linux/netfilter/nf_tables.h>
> > > @@ -693,6 +694,16 @@ static void nf_tables_table_notify(const struct nft_ctx *ctx, int event)
> > >  {
> > >  	struct sk_buff *skb;
> > >  	int err;
> > > +	char *buf = kasprintf(GFP_KERNEL, "%s:%llu;?:0",
> > > +			      ctx->table->name, ctx->table->handle);
> > > +
> > > +	audit_log_nfcfg(buf,
> > > +			ctx->family,
> > > +			ctx->table->use,
> > > +			event == NFT_MSG_NEWTABLE ?
> > > +				AUDIT_NFT_OP_TABLE_REGISTER :
> > > +				AUDIT_NFT_OP_TABLE_UNREGISTER);
> > > +	kfree(buf);
> > 
> > As a follow up: Would you wrap this code into a function?
> > 
> >         nft_table_audit()
> > 
> > Same thing for other pieces of code below.
> 
> If I'm guessing right, you are asking for a supplementary follow-up
> cleanup patch to this one (or are you nacking this patch)?

No nack, it's just that I'd prefer to see this wrapped in a function.
I think your patch is already in the audit tree.

> Also, I gather you would like to see the kasprintf and kfree hidden in
> nft_table_audit(), handing this function at least 8 parameters?  This
> sounds pretty messy given the format of the table field.

I think you can pass ctx and the specific object, e.g. table, in most
cases? There is also event and the gfp_flags. That counts 4 here, but
maybe I'm overlooking something.

Thanks.