OpenWrt – Rev 4
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From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Sat, 30 Dec 2017 22:41:46 +0100
Subject: [PATCH] netfilter: remove defensive check on malformed packets from
raw sockets
Users cannot forge malformed IPv4/IPv6 headers via raw sockets that they
can inject into the stack. Specifically, not for IPv4 since 55888dfb6ba7
("AF_RAW: Augment raw_send_hdrinc to expand skb to fit iphdr->ihl
(v2)"). IPv6 raw sockets also ensure that packets have a well-formed
IPv6 header available in the skbuff.
At quick glance, br_netfilter also validates layer 3 headers and it
drops malformed both IPv4 and IPv6 packets.
Therefore, let's remove this defensive check all over the place.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
--- a/net/ipv4/netfilter/iptable_filter.c
+++ b/net/ipv4/netfilter/iptable_filter.c
@@ -38,12 +38,6 @@ static unsigned int
iptable_filter_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
- if (state->hook == NF_INET_LOCAL_OUT &&
- (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr)))
- /* root is playing with raw sockets. */
- return NF_ACCEPT;
-
return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
}
--- a/net/ipv4/netfilter/iptable_mangle.c
+++ b/net/ipv4/netfilter/iptable_mangle.c
@@ -49,11 +49,6 @@ ipt_mangle_out(struct sk_buff *skb, cons
u_int32_t mark;
int err;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
-
/* Save things which could affect route */
mark = skb->mark;
iph = ip_hdr(skb);
--- a/net/ipv4/netfilter/iptable_raw.c
+++ b/net/ipv4/netfilter/iptable_raw.c
@@ -26,12 +26,6 @@ static unsigned int
iptable_raw_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
- if (state->hook == NF_INET_LOCAL_OUT &&
- (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr)))
- /* root is playing with raw sockets. */
- return NF_ACCEPT;
-
return ipt_do_table(skb, state, state->net->ipv4.iptable_raw);
}
--- a/net/ipv4/netfilter/iptable_security.c
+++ b/net/ipv4/netfilter/iptable_security.c
@@ -43,12 +43,6 @@ static unsigned int
iptable_security_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
- if (state->hook == NF_INET_LOCAL_OUT &&
- (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr)))
- /* Somebody is playing with raw sockets. */
- return NF_ACCEPT;
-
return ipt_do_table(skb, state, state->net->ipv4.iptable_security);
}
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -154,11 +154,6 @@ static unsigned int ipv4_conntrack_local
struct sk_buff *skb,
const struct nf_hook_state *state)
{
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
-
if (ip_is_fragment(ip_hdr(skb))) { /* IP_NODEFRAG setsockopt set */
enum ip_conntrack_info ctinfo;
struct nf_conn *tmpl;
--- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
@@ -355,11 +355,6 @@ nf_nat_ipv4_out(void *priv, struct sk_bu
#endif
unsigned int ret;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
-
ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
#ifdef CONFIG_XFRM
if (ret != NF_DROP && ret != NF_STOLEN &&
@@ -395,11 +390,6 @@ nf_nat_ipv4_local_fn(void *priv, struct
unsigned int ret;
int err;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
-
ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
if (ret != NF_DROP && ret != NF_STOLEN &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
--- a/net/ipv4/netfilter/nf_tables_ipv4.c
+++ b/net/ipv4/netfilter/nf_tables_ipv4.c
@@ -30,21 +30,6 @@ static unsigned int nft_do_chain_ipv4(vo
return nft_do_chain(&pkt, priv);
}
-static unsigned int nft_ipv4_output(void *priv,
- struct sk_buff *skb,
- const struct nf_hook_state *state)
-{
- if (unlikely(skb->len < sizeof(struct iphdr) ||
- ip_hdr(skb)->ihl < sizeof(struct iphdr) / 4)) {
- if (net_ratelimit())
- pr_info("nf_tables_ipv4: ignoring short SOCK_RAW "
- "packet\n");
- return NF_ACCEPT;
- }
-
- return nft_do_chain_ipv4(priv, skb, state);
-}
-
static struct nft_af_info nft_af_ipv4 __read_mostly = {
.family = NFPROTO_IPV4,
.nhooks = NF_INET_NUMHOOKS,
@@ -91,7 +76,7 @@ static const struct nf_chain_type filter
(1 << NF_INET_POST_ROUTING),
.hooks = {
[NF_INET_LOCAL_IN] = nft_do_chain_ipv4,
- [NF_INET_LOCAL_OUT] = nft_ipv4_output,
+ [NF_INET_LOCAL_OUT] = nft_do_chain_ipv4,
[NF_INET_FORWARD] = nft_do_chain_ipv4,
[NF_INET_PRE_ROUTING] = nft_do_chain_ipv4,
[NF_INET_POST_ROUTING] = nft_do_chain_ipv4,
--- a/net/ipv4/netfilter/nft_chain_route_ipv4.c
+++ b/net/ipv4/netfilter/nft_chain_route_ipv4.c
@@ -33,11 +33,6 @@ static unsigned int nf_route_table_hook(
const struct iphdr *iph;
int err;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
-
nft_set_pktinfo(&pkt, skb, state);
nft_set_pktinfo_ipv4(&pkt, skb);
--- a/net/ipv6/netfilter/ip6table_mangle.c
+++ b/net/ipv6/netfilter/ip6table_mangle.c
@@ -42,14 +42,6 @@ ip6t_mangle_out(struct sk_buff *skb, con
u_int8_t hop_limit;
u_int32_t flowlabel, mark;
int err;
-#if 0
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr)) {
- net_warn_ratelimited("ip6t_hook: happy cracking\n");
- return NF_ACCEPT;
- }
-#endif
/* save source/dest address, mark, hoplimit, flowlabel, priority, */
memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
--- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
@@ -176,11 +176,6 @@ static unsigned int ipv6_conntrack_local
struct sk_buff *skb,
const struct nf_hook_state *state)
{
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct ipv6hdr)) {
- net_notice_ratelimited("ipv6_conntrack_local: packet too short\n");
- return NF_ACCEPT;
- }
return nf_conntrack_in(state->net, PF_INET6, state->hook, skb);
}
--- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
@@ -372,10 +372,6 @@ nf_nat_ipv6_out(void *priv, struct sk_bu
#endif
unsigned int ret;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct ipv6hdr))
- return NF_ACCEPT;
-
ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
#ifdef CONFIG_XFRM
if (ret != NF_DROP && ret != NF_STOLEN &&
@@ -411,10 +407,6 @@ nf_nat_ipv6_local_fn(void *priv, struct
unsigned int ret;
int err;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct ipv6hdr))
- return NF_ACCEPT;
-
ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
if (ret != NF_DROP && ret != NF_STOLEN &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
--- a/net/ipv6/netfilter/nf_tables_ipv6.c
+++ b/net/ipv6/netfilter/nf_tables_ipv6.c
@@ -28,20 +28,6 @@ static unsigned int nft_do_chain_ipv6(vo
return nft_do_chain(&pkt, priv);
}
-static unsigned int nft_ipv6_output(void *priv,
- struct sk_buff *skb,
- const struct nf_hook_state *state)
-{
- if (unlikely(skb->len < sizeof(struct ipv6hdr))) {
- if (net_ratelimit())
- pr_info("nf_tables_ipv6: ignoring short SOCK_RAW "
- "packet\n");
- return NF_ACCEPT;
- }
-
- return nft_do_chain_ipv6(priv, skb, state);
-}
-
static struct nft_af_info nft_af_ipv6 __read_mostly = {
.family = NFPROTO_IPV6,
.nhooks = NF_INET_NUMHOOKS,
@@ -88,7 +74,7 @@ static const struct nf_chain_type filter
(1 << NF_INET_POST_ROUTING),
.hooks = {
[NF_INET_LOCAL_IN] = nft_do_chain_ipv6,
- [NF_INET_LOCAL_OUT] = nft_ipv6_output,
+ [NF_INET_LOCAL_OUT] = nft_do_chain_ipv6,
[NF_INET_FORWARD] = nft_do_chain_ipv6,
[NF_INET_PRE_ROUTING] = nft_do_chain_ipv6,
[NF_INET_POST_ROUTING] = nft_do_chain_ipv6,
--- a/net/netfilter/nf_tables_inet.c
+++ b/net/netfilter/nf_tables_inet.c
@@ -38,38 +38,6 @@ static unsigned int nft_do_chain_inet(vo
return nft_do_chain(&pkt, priv);
}
-static unsigned int nft_inet_output(void *priv, struct sk_buff *skb,
- const struct nf_hook_state *state)
-{
- struct nft_pktinfo pkt;
-
- nft_set_pktinfo(&pkt, skb, state);
-
- switch (state->pf) {
- case NFPROTO_IPV4:
- if (unlikely(skb->len < sizeof(struct iphdr) ||
- ip_hdr(skb)->ihl < sizeof(struct iphdr) / 4)) {
- if (net_ratelimit())
- pr_info("ignoring short SOCK_RAW packet\n");
- return NF_ACCEPT;
- }
- nft_set_pktinfo_ipv4(&pkt, skb);
- break;
- case NFPROTO_IPV6:
- if (unlikely(skb->len < sizeof(struct ipv6hdr))) {
- if (net_ratelimit())
- pr_info("ignoring short SOCK_RAW packet\n");
- return NF_ACCEPT;
- }
- nft_set_pktinfo_ipv6(&pkt, skb);
- break;
- default:
- break;
- }
-
- return nft_do_chain(&pkt, priv);
-}
-
static struct nft_af_info nft_af_inet __read_mostly = {
.family = NFPROTO_INET,
.nhooks = NF_INET_NUMHOOKS,
@@ -116,7 +84,7 @@ static const struct nf_chain_type filter
(1 << NF_INET_POST_ROUTING),
.hooks = {
[NF_INET_LOCAL_IN] = nft_do_chain_inet,
- [NF_INET_LOCAL_OUT] = nft_inet_output,
+ [NF_INET_LOCAL_OUT] = nft_do_chain_inet,
[NF_INET_FORWARD] = nft_do_chain_inet,
[NF_INET_PRE_ROUTING] = nft_do_chain_inet,
[NF_INET_POST_ROUTING] = nft_do_chain_inet,