linux-kernel - Re: [PATCH] audit: log nftables configuration change events once per table

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Message-ID: <20210318163032.GS5298@orbyte.nwl.cc>
Date:   Thu, 18 Mar 2021 17:30:32 +0100
From:   Phil Sutter <phil@....cc>
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>,
        Eric Paris <eparis@...isplace.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Florian Westphal <fw@...len.de>, twoerner@...hat.com,
        tgraf@...radead.org, dan.carpenter@...cle.com,
        Jones Desougi <jones.desougi+netfilter@...il.com>
Subject: Re: [PATCH] audit: log nftables configuration change events once per
 table

Hi,

On Thu, Mar 18, 2021 at 11:39:52AM -0400, Richard Guy Briggs wrote:
> Reduce logging of nftables events to a level similar to iptables.
> Restore the table field to list the table, adding the generation.

This looks much better, a few remarks below:

[...]
> +static const u8 nft2audit_op[] = { // enum nf_tables_msg_types
> +	/* NFT_MSG_NEWTABLE	*/	AUDIT_NFT_OP_TABLE_REGISTER,
> +	/* NFT_MSG_GETTABLE	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELTABLE	*/	AUDIT_NFT_OP_TABLE_UNREGISTER,
> +	/* NFT_MSG_NEWCHAIN	*/	AUDIT_NFT_OP_CHAIN_REGISTER,
> +	/* NFT_MSG_GETCHAIN	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELCHAIN	*/	AUDIT_NFT_OP_CHAIN_UNREGISTER,
> +	/* NFT_MSG_NEWRULE	*/	AUDIT_NFT_OP_RULE_REGISTER,
> +	/* NFT_MSG_GETRULE	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELRULE	*/	AUDIT_NFT_OP_RULE_UNREGISTER,
> +	/* NFT_MSG_NEWSET	*/	AUDIT_NFT_OP_SET_REGISTER,
> +	/* NFT_MSG_GETSET	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELSET	*/	AUDIT_NFT_OP_SET_UNREGISTER,
> +	/* NFT_MSG_NEWSETELEM	*/	AUDIT_NFT_OP_SETELEM_REGISTER,
> +	/* NFT_MSG_GETSETELEM	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELSETELEM	*/	AUDIT_NFT_OP_SETELEM_UNREGISTER,
> +	/* NFT_MSG_NEWGEN	*/	AUDIT_NFT_OP_GEN_REGISTER,
> +	/* NFT_MSG_GETGEN	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_TRACE	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_NEWOBJ	*/	AUDIT_NFT_OP_OBJ_REGISTER,
> +	/* NFT_MSG_GETOBJ	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELOBJ	*/	AUDIT_NFT_OP_OBJ_UNREGISTER,
> +	/* NFT_MSG_GETOBJ_RESET	*/	AUDIT_NFT_OP_OBJ_RESET,
> +	/* NFT_MSG_NEWFLOWTABLE	*/	AUDIT_NFT_OP_FLOWTABLE_REGISTER,
> +	/* NFT_MSG_GETFLOWTABLE	*/	AUDIT_NFT_OP_INVALID,
> +	/* NFT_MSG_DELFLOWTABLE	*/	AUDIT_NFT_OP_FLOWTABLE_UNREGISTER,
> +	/* NFT_MSG_MAX		*/	AUDIT_NFT_OP_INVALID,
> +};

NFT_MSG_MAX is itself not a valid message, it serves merely as an upper
bound for arrays, loops or sanity checks. You will never see it in
trans->msg_type.

Since enum nf_tables_msg_types contains consecutive values from 0 to
NFT_MSG_MAX, you could write the above more explicitly:

| static const u8 nft2audit_op[NFT_MSG_MAX] = {
| 	[NFT_MSG_NEWTABLE]	= AUDIT_NFT_OP_TABLE_REGISTER,
| 	[NFT_MSG_GETTABLE]	= AUDIT_NFT_OP_INVALID,
| 	[NFT_MSG_DELTABLE]	= AUDIT_NFT_OP_TABLE_UNREGISTER,
(And so forth.)

Not a must, but it clarifies the 1:1 mapping between index and said
enum. Sadly, AUDIT_NFT_OP_INVALID is non-zero. Otherwise one could skip
all uninteresting ones.

[...]
> @@ -6278,12 +6219,11 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
>  			    filter->type != NFT_OBJECT_UNSPEC &&
>  			    obj->ops->type->type != filter->type)
>  				goto cont;
> -
>  			if (reset) {
>  				char *buf = kasprintf(GFP_ATOMIC,
> -						      "%s:%llu;?:0",
> +						      "%s:%u",
>  						      table->name,
> -						      table->handle);
> +						      net->nft.base_seq);
>  
>  				audit_log_nfcfg(buf,
>  						family,

Why did you leave the object-related logs in place? They should reappear
at commit time just like chains and sets for instance, no?

Thanks, Phil