Re: [PATCH nftables v2 1/2] src: add ability to set/get secmarks to/from connection

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

Hi Christian,

On Sat, Nov 23, 2019 at 05:22:39PM +0100, Christian Göttsche wrote:
[...]
> v2: - incorporate changes suggested by Pablo Neira Ayuso
>     - invalidate setting ct secmark to a constant value, like:
>         ct secmark set 12
>       Note:
>       statements setting the meta secmark, like
>         meta secmark set 12
>       must accept constant values, cause the secmark object identifier
>       is a string
>         meta secmark set "icmp_client"

This is represented as a object reference statement from the parser.

It should be safe to do the same check from stmt_evaluate_meta() that
this patch does for stmt_evaluate_ct().

>       12 is probably not a used secmark object identifier, so it will
>       fail:
>         nft add rule inet filter input meta secmark set 12
>         Error: Could not process rule: No such file or directory
>         add rule inet filter input meta secmark set 12
>         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>  src/ct.c           |  2 ++
>  src/evaluate.c     | 24 ++++++++++++++++++++++--
>  src/meta.c         |  2 ++
>  src/parser_bison.y | 14 +++++++++++---
>  4 files changed, 37 insertions(+), 5 deletions(-)
> 
> diff --git a/src/ct.c b/src/ct.c
> index ed458e6b..9e6a8351 100644
> --- a/src/ct.c
> +++ b/src/ct.c
> @@ -299,6 +299,8 @@ const struct ct_template ct_templates[__NFT_CT_MAX] = {
>  					      BYTEORDER_BIG_ENDIAN, 128),
>  	[NFT_CT_DST_IP6]	= CT_TEMPLATE("ip6 daddr", &ip6addr_type,
>  					      BYTEORDER_BIG_ENDIAN, 128),
> +	[NFT_CT_SECMARK]	= CT_TEMPLATE("secmark", &integer_type,
> +					      BYTEORDER_HOST_ENDIAN, 32),
>  };
>  
>  static void ct_print(enum nft_ct_keys key, int8_t dir, uint8_t nfproto,
> diff --git a/src/evaluate.c b/src/evaluate.c
> index e54eaf1a..a865902c 100644
> --- a/src/evaluate.c
> +++ b/src/evaluate.c
> @@ -1784,6 +1784,18 @@ static int expr_evaluate_relational(struct eval_ctx *ctx, struct expr **expr)
>  					 left->dtype->desc,
>  					 right->dtype->desc);
>  
> +	/*
> +	 * Statements like 'ct secmark 12' are parsed as relational,
> +	 * disallow constant value on the right hand side.
> +	 */
> +	if (((left->etype == EXPR_META &&
> +	      left->meta.key == NFT_META_SECMARK) ||
> +	     (left->etype == EXPR_CT &&
> +	      left->ct.key == NFT_CT_SECMARK)) &&
> +	    right->flags & EXPR_F_CONSTANT)
> +		return expr_binary_error(ctx->msgs, right, left,
> +					 "Cannot be used with right hand side constant value");
> +
>  	switch (rel->op) {
>  	case OP_EQ:
>  	case OP_IMPLICIT:
> @@ -2319,11 +2331,19 @@ static int stmt_evaluate_meta(struct eval_ctx *ctx, struct stmt *stmt)
>  
>  static int stmt_evaluate_ct(struct eval_ctx *ctx, struct stmt *stmt)
>  {
> -	return stmt_evaluate_arg(ctx, stmt,
> +	if (stmt_evaluate_arg(ctx, stmt,
>  				 stmt->ct.tmpl->dtype,
>  				 stmt->ct.tmpl->len,
>  				 stmt->ct.tmpl->byteorder,
> -				 &stmt->ct.expr);
> +				 &stmt->ct.expr) < 0)
> +		return -1;
> +
> +	if (stmt->ct.key == NFT_CT_SECMARK &&
> +	    expr_is_constant(stmt->ct.expr))
> +		return stmt_error(ctx, stmt,
> +				  "ct secmark must not be set to constant value");
> +
> +	return 0;
>  }
>  
>  static int reject_payload_gen_dependency_tcp(struct eval_ctx *ctx,
> diff --git a/src/meta.c b/src/meta.c
> index 69a897a9..796d8e94 100644
> --- a/src/meta.c
> +++ b/src/meta.c
> @@ -698,6 +698,8 @@ const struct meta_template meta_templates[] = {
>  	[NFT_META_TIME_HOUR]	= META_TEMPLATE("hour", &hour_type,
>  						4 * BITS_PER_BYTE,
>  						BYTEORDER_HOST_ENDIAN),
> +	[NFT_META_SECMARK]	= META_TEMPLATE("secmark", &integer_type,
> +						32, BYTEORDER_HOST_ENDIAN),
>  };
>  
>  static bool meta_key_is_unqualified(enum nft_meta_keys key)
> diff --git a/src/parser_bison.y b/src/parser_bison.y
> index 631b7d68..707f4671 100644
> --- a/src/parser_bison.y
> +++ b/src/parser_bison.y
> @@ -4190,9 +4190,16 @@ meta_stmt		:	META	meta_key	SET	stmt_expr
>  			{
>  				switch ($2) {
>  				case NFT_META_SECMARK:
> -					$$ = objref_stmt_alloc(&@$);
> -					$$->objref.type = NFT_OBJECT_SECMARK;
> -					$$->objref.expr = $4;
> +					switch ($4->etype) {
> +					case EXPR_CT:
> +						$$ = meta_stmt_alloc(&@$, $2, $4);
> +						break;
> +					default:
> +						$$ = objref_stmt_alloc(&@$);
> +						$$->objref.type = NFT_OBJECT_SECMARK;
> +						$$->objref.expr = $4;
> +						break;
> +					}
>  					break;
>  				default:
>  					$$ = meta_stmt_alloc(&@$, $2, $4);
> @@ -4388,6 +4395,7 @@ ct_key			:	L3PROTOCOL	{ $$ = NFT_CT_L3PROTOCOL; }
>  			|	PROTO_DST	{ $$ = NFT_CT_PROTO_DST; }
>  			|	LABEL		{ $$ = NFT_CT_LABELS; }
>  			|	EVENT		{ $$ = NFT_CT_EVENTMASK; }
> +			|	SECMARK		{ $$ = NFT_CT_SECMARK; }
>  			|	ct_key_dir_optional
>  			;
>  
> -- 
> 2.24.0
>