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authorFlorian Westphal <fw@strlen.de>2015-02-16 18:54:04 +0100
committerPablo Neira Ayuso <pablo@netfilter.org>2015-03-03 02:10:35 +0100
commitee586bbc28fb7128133457cf711880d13a3b7ce4 (patch)
treed1e1991b5d622b588c11608b9164499a96869e51 /net/ipv6
parentb898441f4ece44933af90b116b467f7864dd1ae7 (diff)
downloadlinux-ee586bbc28fb7128133457cf711880d13a3b7ce4.tar.bz2
netfilter: reject: don't send icmp error if csum is invalid
tcp resets are never emitted if the packet that triggers the reject/reset has an invalid checksum. For icmp error responses there was no such check. It allows to distinguish icmp response generated via iptables -I INPUT -p udp --dport 42 -j REJECT and those emitted by network stack (won't respond if csum is invalid, REJECT does). Arguably its possible to avoid this by using conntrack and only using REJECT with -m conntrack NEW/RELATED. However, this doesn't work when connection tracking is not in use or when using nf_conntrack_checksum=0. Furthermore, sending errors in response to invalid csums doesn't make much sense so just add similar test as in nf_send_reset. Validate csum if needed and only send the response if it is ok. Reference: http://bugzilla.redhat.com/show_bug.cgi?id=1169829 Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/netfilter/nf_reject_ipv6.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c
index d05b36440e8b..68e0bb4db1bf 100644
--- a/net/ipv6/netfilter/nf_reject_ipv6.c
+++ b/net/ipv6/netfilter/nf_reject_ipv6.c
@@ -208,4 +208,39 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
}
EXPORT_SYMBOL_GPL(nf_send_reset6);
+static bool reject6_csum_ok(struct sk_buff *skb, int hook)
+{
+ const struct ipv6hdr *ip6h = ipv6_hdr(skb);
+ int thoff;
+ __be16 fo;
+ u8 proto;
+
+ if (skb->csum_bad)
+ return false;
+
+ if (skb_csum_unnecessary(skb))
+ return true;
+
+ proto = ip6h->nexthdr;
+ thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
+
+ if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
+ return false;
+
+ return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
+}
+
+void nf_send_unreach6(struct net *net, struct sk_buff *skb_in,
+ unsigned char code, unsigned int hooknum)
+{
+ if (!reject6_csum_ok(skb_in, hooknum))
+ return;
+
+ if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
+ skb_in->dev = net->loopback_dev;
+
+ icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
+}
+EXPORT_SYMBOL_GPL(nf_send_unreach6);
+
MODULE_LICENSE("GPL");