// SPDX-License-Identifier: GPL-2.0-only
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2004 Netfilter Core Team <[email protected]>
*/
#include <linux/module.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/ip6_fib.h>
#include <net/ip6_checksum.h>
#include <net/netfilter/ipv6/nf_reject.h>
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter_bridge.h>
static bool nf_reject_v6_csum_ok(struct sk_buff *skb, int hook)
{
const struct ipv6hdr *ip6h = ipv6_hdr(skb);
int thoff;
__be16 fo;
u8 proto = ip6h->nexthdr;
if (skb_csum_unnecessary(skb))
return true;
if (ip6h->payload_len &&
pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
return false;
ip6h = ipv6_hdr(skb);
thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
return false;
if (!nf_reject_verify_csum(skb, thoff, proto))
return true;
return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
}
static int nf_reject_ip6hdr_validate(struct sk_buff *skb)
{
struct ipv6hdr *hdr;
u32 pkt_len;
if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
return 0;
hdr = ipv6_hdr(skb);
if (hdr->version != 6)
return 0;
pkt_len = ntohs(hdr->payload_len);
if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
return 0;
return 1;
}
struct sk_buff *nf_reject_skb_v6_tcp_reset(struct net *net,
struct sk_buff *oldskb,
const struct net_device *dev,
int hook)
{
struct sk_buff *nskb;
const struct tcphdr *oth;
struct tcphdr _oth;
unsigned int otcplen;
struct ipv6hdr *nip6h;
if (!nf_reject_ip6hdr_validate(oldskb))
return NULL;
oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
if (!oth)
return NULL;
nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
LL_MAX_HEADER, GFP_ATOMIC);
if (!nskb)
return NULL;
nskb->dev = (struct net_device *)dev;
skb_reserve(nskb, LL_MAX_HEADER);
nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
READ_ONCE(net->ipv6.devconf_all->hop_limit));
nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
return nskb;
}
EXPORT_SYMBOL_GPL(nf_reject_skb_v6_tcp_reset);
struct sk_buff *nf_reject_skb_v6_unreach(struct net *net,
struct sk_buff *oldskb,
const struct net_device *dev,
int hook, u8 code)
{
struct sk_buff *nskb;
struct ipv6hdr *nip6h;
struct icmp6hdr *icmp6h;
unsigned int len;
if (!nf_reject_ip6hdr_validate(oldskb))
return NULL;
/* Include "As much of invoking packet as possible without the ICMPv6
* packet exceeding the minimum IPv6 MTU" in the ICMP payload.
*/
len = min_t(unsigned int, 1220, oldskb->len);
if (!pskb_may_pull(oldskb, len))
return NULL;
if (!nf_reject_v6_csum_ok(oldskb, hook))
return NULL;
nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr) +
LL_MAX_HEADER + len, GFP_ATOMIC);
if (!nskb)
return NULL;
nskb->dev = (struct net_device *)dev;
skb_reserve(nskb, LL_MAX_HEADER);
nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
READ_ONCE(net->ipv6.devconf_all->hop_limit));
skb_reset_transport_header(nskb);
icmp6h = skb_put_zero(nskb, sizeof(struct icmp6hdr));
icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
icmp6h->icmp6_code = code;
skb_put_data(nskb, skb_network_header(oldskb), len);
nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
icmp6h->icmp6_cksum =
csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
nskb->len - sizeof(struct ipv6hdr),
IPPROTO_ICMPV6,
csum_partial(icmp6h,
nskb->len - sizeof(struct ipv6hdr),
0));
return nskb;
}
EXPORT_SYMBOL_GPL(nf_reject_skb_v6_unreach);
const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
struct tcphdr *otcph,
unsigned int *otcplen, int hook)
{
const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
u8 proto;
__be16 frag_off;
int tcphoff;
proto = oip6h->nexthdr;
tcphoff = ipv6_skip_exthdr(oldskb, ((u8 *)(oip6h + 1) - oldskb->data),
&proto, &frag_off);
if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
pr_debug("Cannot get TCP header.\n");
return NULL;
}
*otcplen = oldskb->len - tcphoff;
/* IP header checks: fragment, too short. */
if (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) {
pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
proto, *otcplen);
return NULL;
}
otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
otcph);
if (otcph == NULL)
return NULL;
/* No RST for RST. */
if (otcph->rst) {
pr_debug("RST is set\n");
return NULL;
}
/* Check checksum. */
if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
pr_debug("TCP checksum is invalid\n");
return NULL;
}
return otcph;
}
EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);
struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb,
const struct sk_buff *oldskb,
__u8 protocol, int hoplimit)
{
struct ipv6hdr *ip6h;
const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
#define DEFAULT_TOS_VALUE 0x0U
const __u8 tclass = DEFAULT_TOS_VALUE;
skb_put(nskb, sizeof(struct ipv6hdr));
skb_reset_network_header(nskb);
ip6h = ipv6_hdr(nskb);
ip6_flow_hdr(ip6h, tclass, 0);
ip6h->hop_limit = hoplimit;
ip6h->nexthdr = protocol;
ip6h->saddr = oip6h->daddr;
ip6h->daddr = oip6h->saddr;
nskb->protocol = htons(ETH_P_IPV6);
return ip6h;
}
EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put);
void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
const struct sk_buff *oldskb,
const struct tcphdr *oth, unsigned int otcplen)
{
struct tcphdr *tcph;
skb_reset_transport_header(nskb);
tcph = skb_put_zero(nskb, sizeof(struct tcphdr));
/* Truncate to length (no data) */
tcph->doff = sizeof(struct tcphdr)/4;
tcph->source = oth->dest;
tcph->dest = oth->source;
if (oth->ack) {
tcph->seq = oth->ack_seq;
} else {
tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
otcplen - (oth->doff<<2));
tcph->ack = 1;
}
tcph->rst = 1;
/* Adjust TCP checksum */
tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
&ipv6_hdr(nskb)->daddr,
sizeof(struct tcphdr), IPPROTO_TCP,
csum_partial(tcph,
sizeof(struct tcphdr), 0));
}
EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put);
static int nf_reject6_fill_skb_dst(struct sk_buff *skb_in)
{
struct dst_entry *dst = NULL;
struct flowi fl;
memset(&fl, 0, sizeof(struct flowi));
fl.u.ip6.daddr = ipv6_hdr(skb_in)->saddr;
nf_ip6_route(dev_net(skb_in->dev), &dst, &fl, false);
if (!dst)
return -1;
skb_dst_set(skb_in, dst);
return 0;
}
void nf_send_reset6(struct net *net, struct sock *sk, struct sk_buff *oldskb,
int hook)
{
struct sk_buff *nskb;
struct tcphdr _otcph;
const struct tcphdr *otcph;
unsigned int otcplen, hh_len;
const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
struct dst_entry *dst = NULL;
struct flowi6 fl6;
if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
(!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
pr_debug("addr is not unicast.\n");
return;
}
otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
if (!otcph)
return;
memset(&fl6, 0, sizeof(fl6));
fl6.flowi6_proto = IPPROTO_TCP;
fl6.saddr = oip6h->daddr;
fl6.daddr = oip6h->saddr;
fl6.fl6_sport = otcph->dest;
fl6.fl6_dport = otcph->source;
if (hook == NF_INET_PRE_ROUTING || hook == NF_INET_INGRESS) {
nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
if (!dst)
return;
skb_dst_set(oldskb, dst);
}
fl6.flowi6_oif = l3mdev_master_ifindex(skb_dst(oldskb)->dev);
fl6.flowi6_mark = IP6_REPLY_MARK(net, oldskb->mark);
security_skb_classify_flow(oldskb, flowi6_to_flowi_common(&fl6));
dst = ip6_route_output(net, NULL, &fl6);
if (dst->error) {
dst_release(dst);
return;
}
dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
if (IS_ERR(dst))
return;
hh_len = (dst->dev->hard_header_len + 15)&~15;
nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
+ sizeof(struct tcphdr) + dst->trailer_len,
GFP_ATOMIC);
if (!nskb) {
net_dbg_ratelimited("cannot alloc skb\n");
dst_release(dst);
return;
}
skb_dst_set(nskb, dst);
nskb->mark = fl6.flowi6_mark;
skb_reserve(nskb, hh_len + dst->header_len);
nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP, ip6_dst_hoplimit(dst));
nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen);
nf_ct_attach(nskb, oldskb);
nf_ct_set_closing(skb_nfct(oldskb));
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
/* If we use ip6_local_out for bridged traffic, the MAC source on
* the RST will be ours, instead of the destination's. This confuses
* some routers/firewalls, and they drop the packet. So we need to
* build the eth header using the original destination's MAC as the
* source, and send the RST packet directly.
*/
if (nf_bridge_info_exists(oldskb)) {
struct ethhdr *oeth = eth_hdr(oldskb);
struct ipv6hdr *ip6h = ipv6_hdr(nskb);
struct net_device *br_indev;
br_indev = nf_bridge_get_physindev(oldskb, net);
if (!br_indev) {
kfree_skb(nskb);
return;
}
nskb->dev = br_indev;
nskb->protocol = htons(ETH_P_IPV6);
ip6h->payload_len = htons(sizeof(struct tcphdr));
if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
oeth->h_source, oeth->h_dest, nskb->len) < 0) {
kfree_skb(nskb);
return;
}
dev_queue_xmit(nskb);
} else
#endif
ip6_local_out(net, sk, nskb);
}
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_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;
if (!nf_reject_verify_csum(skb, thoff, proto))
return true;
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;
if ((hooknum == NF_INET_PRE_ROUTING || hooknum == NF_INET_INGRESS) &&
nf_reject6_fill_skb_dst(skb_in) < 0)
return;
icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
}
EXPORT_SYMBOL_GPL(nf_send_unreach6);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IPv6 packet rejection core");
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