[PATCH] netfilter: xt_pkttype: IPv6 has no broadcast

[PATCH] netfilter: xt_pkttype: IPv6 has no broadcast

[Phil Oester]

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As stated in RFC 4291:

   There are no broadcast addresses in IPv6, their function being
   superseded by multicast addresses.

As such, the pkttype match should not allow IPv6 rules to be added
which attempt to match broadcast packets.  The addrtype match already
rejects such attempts.

Phil

Signed-off-by: Phil Oester <kernel@linuxace.com>



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diff --git a/net/netfilter/xt_pkttype.c b/net/netfilter/xt_pkttype.c
index 5b645cb..4c0b0e1 100644
--- a/net/netfilter/xt_pkttype.c
+++ b/net/netfilter/xt_pkttype.c
@@ -42,13 +42,29 @@ pkttype_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	return (type == info->pkttype) ^ info->invert;
 }
 
+static int pkttype_mt_checkentry(const struct xt_mtchk_param *par)
+{
+	const struct xt_pkttype_info *info = par->matchinfo;
+
+#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
+	if (par->family == NFPROTO_IPV6) {
+		if (info->pkttype == PACKET_BROADCAST) {
+			pr_err("IPv6 does not support BROADCAST packets\n");
+			return -EINVAL;
+		}
+	}
+#endif
+	return 0;
+}
+
 static struct xt_match pkttype_mt_reg __read_mostly = {
-	.name      = "pkttype",
-	.revision  = 0,
-	.family    = NFPROTO_UNSPEC,
-	.match     = pkttype_mt,
-	.matchsize = sizeof(struct xt_pkttype_info),
-	.me        = THIS_MODULE,
+	.name		= "pkttype",
+	.revision	= 0,
+	.family		= NFPROTO_UNSPEC,
+	.checkentry	= pkttype_mt_checkentry,
+	.match		= pkttype_mt,
+	.matchsize	= sizeof(struct xt_pkttype_info),
+	.me		= THIS_MODULE,
 };
 
 static int __init pkttype_mt_init(void)

Re: [PATCH] netfilter: xt_pkttype: IPv6 has no broadcast

[Pablo Neira Ayuso]

Hi Phil,

On Thu, Jul 11, 2013 at 12:03:43PM -0700, Phil Oester wrote:
> As stated in RFC 4291:
> 
>    There are no broadcast addresses in IPv6, their function being
>    superseded by multicast addresses.
> 
> As such, the pkttype match should not allow IPv6 rules to be added
> which attempt to match broadcast packets.  The addrtype match already
> rejects such attempts.
> 
> Phil
> 
> Signed-off-by: Phil Oester <kernel@linuxace.com>
> 
> 
> diff --git a/net/netfilter/xt_pkttype.c b/net/netfilter/xt_pkttype.c
> index 5b645cb..4c0b0e1 100644
> --- a/net/netfilter/xt_pkttype.c
> +++ b/net/netfilter/xt_pkttype.c
> @@ -42,13 +42,29 @@ pkttype_mt(const struct sk_buff *skb, struct xt_action_param *par)
>  	return (type == info->pkttype) ^ info->invert;
>  }
>  
> +static int pkttype_mt_checkentry(const struct xt_mtchk_param *par)
> +{
> +	const struct xt_pkttype_info *info = par->matchinfo;
> +
> +#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
> +	if (par->family == NFPROTO_IPV6) {
> +		if (info->pkttype == PACKET_BROADCAST) {
> +			pr_err("IPv6 does not support BROADCAST packets\n");
> +			return -EINVAL;
> +		}
> +	}

pkttype is set from the ethernet layer, so it's still possible to
forge a packet using the ethernet broadcast address on IPv6 (even if
it's ilegal), we should allow our users to drop that from ip6tables.

> +#endif
> +	return 0;
> +}
> +
>  static struct xt_match pkttype_mt_reg __read_mostly = {
> -	.name      = "pkttype",
> -	.revision  = 0,
> -	.family    = NFPROTO_UNSPEC,
> -	.match     = pkttype_mt,
> -	.matchsize = sizeof(struct xt_pkttype_info),
> -	.me        = THIS_MODULE,
> +	.name		= "pkttype",
> +	.revision	= 0,
> +	.family		= NFPROTO_UNSPEC,
> +	.checkentry	= pkttype_mt_checkentry,
> +	.match		= pkttype_mt,
> +	.matchsize	= sizeof(struct xt_pkttype_info),
> +	.me		= THIS_MODULE,
>  };
>  
>  static int __init pkttype_mt_init(void)