diff options
author | Florian Westphal <fw@strlen.de> | 2015-02-16 18:54:04 +0100 |
---|---|---|
committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2015-03-03 02:10:35 +0100 |
commit | ee586bbc28fb7128133457cf711880d13a3b7ce4 (patch) | |
tree | d1e1991b5d622b588c11608b9164499a96869e51 /net | |
parent | b898441f4ece44933af90b116b467f7864dd1ae7 (diff) | |
download | op-kernel-dev-ee586bbc28fb7128133457cf711880d13a3b7ce4.zip op-kernel-dev-ee586bbc28fb7128133457cf711880d13a3b7ce4.tar.gz |
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')
-rw-r--r-- | net/ipv4/netfilter/ipt_REJECT.c | 17 | ||||
-rw-r--r-- | net/ipv4/netfilter/nf_reject_ipv4.c | 23 | ||||
-rw-r--r-- | net/ipv4/netfilter/nft_reject_ipv4.c | 3 | ||||
-rw-r--r-- | net/ipv6/netfilter/nf_reject_ipv6.c | 35 | ||||
-rw-r--r-- | net/netfilter/nft_reject_inet.c | 6 |
5 files changed, 73 insertions, 11 deletions
diff --git a/net/ipv4/netfilter/ipt_REJECT.c b/net/ipv4/netfilter/ipt_REJECT.c index 8f48f55..87907d4 100644 --- a/net/ipv4/netfilter/ipt_REJECT.c +++ b/net/ipv4/netfilter/ipt_REJECT.c @@ -34,31 +34,32 @@ static unsigned int reject_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ipt_reject_info *reject = par->targinfo; + int hook = par->hooknum; switch (reject->with) { case IPT_ICMP_NET_UNREACHABLE: - nf_send_unreach(skb, ICMP_NET_UNREACH); + nf_send_unreach(skb, ICMP_NET_UNREACH, hook); break; case IPT_ICMP_HOST_UNREACHABLE: - nf_send_unreach(skb, ICMP_HOST_UNREACH); + nf_send_unreach(skb, ICMP_HOST_UNREACH, hook); break; case IPT_ICMP_PROT_UNREACHABLE: - nf_send_unreach(skb, ICMP_PROT_UNREACH); + nf_send_unreach(skb, ICMP_PROT_UNREACH, hook); break; case IPT_ICMP_PORT_UNREACHABLE: - nf_send_unreach(skb, ICMP_PORT_UNREACH); + nf_send_unreach(skb, ICMP_PORT_UNREACH, hook); break; case IPT_ICMP_NET_PROHIBITED: - nf_send_unreach(skb, ICMP_NET_ANO); + nf_send_unreach(skb, ICMP_NET_ANO, hook); break; case IPT_ICMP_HOST_PROHIBITED: - nf_send_unreach(skb, ICMP_HOST_ANO); + nf_send_unreach(skb, ICMP_HOST_ANO, hook); break; case IPT_ICMP_ADMIN_PROHIBITED: - nf_send_unreach(skb, ICMP_PKT_FILTERED); + nf_send_unreach(skb, ICMP_PKT_FILTERED, hook); break; case IPT_TCP_RESET: - nf_send_reset(skb, par->hooknum); + nf_send_reset(skb, hook); case IPT_ICMP_ECHOREPLY: /* Doesn't happen. */ break; diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c index 536da7b..b7405eb 100644 --- a/net/ipv4/netfilter/nf_reject_ipv4.c +++ b/net/ipv4/netfilter/nf_reject_ipv4.c @@ -164,4 +164,27 @@ void nf_send_reset(struct sk_buff *oldskb, int hook) } EXPORT_SYMBOL_GPL(nf_send_reset); +void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) +{ + struct iphdr *iph = ip_hdr(skb_in); + u8 proto; + + if (skb_in->csum_bad || iph->frag_off & htons(IP_OFFSET)) + return; + + if (skb_csum_unnecessary(skb_in)) { + icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); + return; + } + + if (iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP) + proto = iph->protocol; + else + proto = 0; + + if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0) + icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); +} +EXPORT_SYMBOL_GPL(nf_send_unreach); + MODULE_LICENSE("GPL"); diff --git a/net/ipv4/netfilter/nft_reject_ipv4.c b/net/ipv4/netfilter/nft_reject_ipv4.c index d729542..16a5d4d 100644 --- a/net/ipv4/netfilter/nft_reject_ipv4.c +++ b/net/ipv4/netfilter/nft_reject_ipv4.c @@ -27,7 +27,8 @@ static void nft_reject_ipv4_eval(const struct nft_expr *expr, switch (priv->type) { case NFT_REJECT_ICMP_UNREACH: - nf_send_unreach(pkt->skb, priv->icmp_code); + nf_send_unreach(pkt->skb, priv->icmp_code, + pkt->ops->hooknum); break; case NFT_REJECT_TCP_RST: nf_send_reset(pkt->skb, pkt->ops->hooknum); diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c index d05b364..68e0bb4 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"); diff --git a/net/netfilter/nft_reject_inet.c b/net/netfilter/nft_reject_inet.c index 7b5f9d5..9287711 100644 --- a/net/netfilter/nft_reject_inet.c +++ b/net/netfilter/nft_reject_inet.c @@ -28,14 +28,16 @@ static void nft_reject_inet_eval(const struct nft_expr *expr, case NFPROTO_IPV4: switch (priv->type) { case NFT_REJECT_ICMP_UNREACH: - nf_send_unreach(pkt->skb, priv->icmp_code); + nf_send_unreach(pkt->skb, priv->icmp_code, + pkt->ops->hooknum); break; case NFT_REJECT_TCP_RST: nf_send_reset(pkt->skb, pkt->ops->hooknum); break; case NFT_REJECT_ICMPX_UNREACH: nf_send_unreach(pkt->skb, - nft_reject_icmp_code(priv->icmp_code)); + nft_reject_icmp_code(priv->icmp_code), + pkt->ops->hooknum); break; } break; |