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netfilter: synproxy: extract SYNPROXY infrastructure from {ipt, ip6t}_SYNPROXY

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Add common functions into nf_synproxy_core.c to prepare for nftables support.
The prototypes of the functions used by {ipt, ip6t}_SYNPROXY are in the new
file nf_synproxy.h

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Fernando Fernandez Mancera 2019-06-07 02:36:07 +02:00 committed by Pablo Neira Ayuso
parent 3006a5224f
commit d7f9b2f18e
5 changed files with 920 additions and 847 deletions
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13
include/net/netfilter/nf_conntrack_synproxy.h
View File

@ -72,21 +72,12 @@ struct synproxy_options {
};
struct tcphdr;
struct xt_synproxy_info;
struct nf_synproxy_info;
bool synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
const struct tcphdr *th,
struct synproxy_options *opts);
unsigned int synproxy_options_size(const struct synproxy_options *opts);
void synproxy_build_options(struct tcphdr *th,
const struct synproxy_options *opts);
void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info,
void synproxy_init_timestamp_cookie(const struct nf_synproxy_info *info,
struct synproxy_options *opts);
void synproxy_check_timestamp_cookie(struct synproxy_options *opts);
unsigned int synproxy_tstamp_adjust(struct sk_buff *skb, unsigned int protoff,
struct tcphdr *th, struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
const struct nf_conn_synproxy *synproxy);
#endif /* _NF_CONNTRACK_SYNPROXY_H */

44
include/net/netfilter/nf_synproxy.h Normal file
View File

@ -0,0 +1,44 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _NF_SYNPROXY_SHARED_H
#define _NF_SYNPROXY_SHARED_H
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ip6_checksum.h>
#include <net/ip6_route.h>
#include <net/tcp.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_synproxy.h>
void synproxy_send_client_synack(struct net *net, const struct sk_buff *skb,
const struct tcphdr *th,
const struct synproxy_options *opts);
bool synproxy_recv_client_ack(struct net *net,
const struct sk_buff *skb,
const struct tcphdr *th,
struct synproxy_options *opts, u32 recv_seq);
unsigned int ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *nhs);
int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net);
void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net);
#if IS_ENABLED(CONFIG_IPV6)
void synproxy_send_client_synack_ipv6(struct net *net,
const struct sk_buff *skb,
const struct tcphdr *th,
const struct synproxy_options *opts);
bool synproxy_recv_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
const struct tcphdr *th,
struct synproxy_options *opts, u32 recv_seq);
unsigned int ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *nhs);
int nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net);
void nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net);
#endif /* CONFIG_IPV6 */
#endif /* _NF_SYNPROXY_SHARED_H */

394
net/ipv4/netfilter/ipt_SYNPROXY.c
View File

@ -6,258 +6,11 @@
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_SYNPROXY.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_synproxy.h>
#include <net/netfilter/nf_conntrack_ecache.h>
static struct iphdr *
synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
__be32 daddr)
{
struct iphdr *iph;
skb_reset_network_header(skb);
iph = skb_put(skb, sizeof(*iph));
iph->version = 4;
iph->ihl = sizeof(*iph) / 4;
iph->tos = 0;
iph->id = 0;
iph->frag_off = htons(IP_DF);
iph->ttl = net->ipv4.sysctl_ip_default_ttl;
iph->protocol = IPPROTO_TCP;
iph->check = 0;
iph->saddr = saddr;
iph->daddr = daddr;
return iph;
}
static void
synproxy_send_tcp(struct net *net,
const struct sk_buff *skb, struct sk_buff *nskb,
struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
struct iphdr *niph, struct tcphdr *nth,
unsigned int tcp_hdr_size)
{
nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
nskb->ip_summed = CHECKSUM_PARTIAL;
nskb->csum_start = (unsigned char *)nth - nskb->head;
nskb->csum_offset = offsetof(struct tcphdr, check);
skb_dst_set_noref(nskb, skb_dst(skb));
nskb->protocol = htons(ETH_P_IP);
if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
goto free_nskb;
if (nfct) {
nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
nf_conntrack_get(nfct);
}
ip_local_out(net, nskb->sk, nskb);
return;
free_nskb:
kfree_skb(nskb);
}
static void
synproxy_send_client_synack(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts)
{
struct sk_buff *nskb;
struct iphdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
u16 mss = opts->mss;
iph = ip_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->dest;
nth->dest = th->source;
nth->seq = htonl(__cookie_v4_init_sequence(iph, th, &mss));
nth->ack_seq = htonl(ntohl(th->seq) + 1);
tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
if (opts->options & XT_SYNPROXY_OPT_ECN)
tcp_flag_word(nth) |= TCP_FLAG_ECE;
nth->doff = tcp_hdr_size / 4;
nth->window = 0;
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
}
static void
synproxy_send_server_syn(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts, u32 recv_seq)
{
struct synproxy_net *snet = synproxy_pernet(net);
struct sk_buff *nskb;
struct iphdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
iph = ip_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->source;
nth->dest = th->dest;
nth->seq = htonl(recv_seq - 1);
/* ack_seq is used to relay our ISN to the synproxy hook to initialize
* sequence number translation once a connection tracking entry exists.
*/
nth->ack_seq = htonl(ntohl(th->ack_seq) - 1);
tcp_flag_word(nth) = TCP_FLAG_SYN;
if (opts->options & XT_SYNPROXY_OPT_ECN)
tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
nth->doff = tcp_hdr_size / 4;
nth->window = th->window;
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
niph, nth, tcp_hdr_size);
}
static void
synproxy_send_server_ack(struct net *net,
const struct ip_ct_tcp *state,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts)
{
struct sk_buff *nskb;
struct iphdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
iph = ip_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->dest;
nth->dest = th->source;
nth->seq = htonl(ntohl(th->ack_seq));
nth->ack_seq = htonl(ntohl(th->seq) + 1);
tcp_flag_word(nth) = TCP_FLAG_ACK;
nth->doff = tcp_hdr_size / 4;
nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
}
static void
synproxy_send_client_ack(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts)
{
struct sk_buff *nskb;
struct iphdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
iph = ip_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->source;
nth->dest = th->dest;
nth->seq = htonl(ntohl(th->seq) + 1);
nth->ack_seq = th->ack_seq;
tcp_flag_word(nth) = TCP_FLAG_ACK;
nth->doff = tcp_hdr_size / 4;
nth->window = htons(ntohs(th->window) >> opts->wscale);
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
}
static bool
synproxy_recv_client_ack(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
struct synproxy_options *opts, u32 recv_seq)
{
struct synproxy_net *snet = synproxy_pernet(net);
int mss;
mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
if (mss == 0) {
this_cpu_inc(snet->stats->cookie_invalid);
return false;
}
this_cpu_inc(snet->stats->cookie_valid);
opts->mss = mss;
opts->options |= XT_SYNPROXY_OPT_MSS;
if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
synproxy_check_timestamp_cookie(opts);
synproxy_send_server_syn(net, skb, th, opts, recv_seq);
return true;
}
#include <net/netfilter/nf_synproxy.h>
static unsigned int
synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
@ -309,135 +62,6 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
return XT_CONTINUE;
}
static unsigned int ipv4_synproxy_hook(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *nhs)
{
struct net *net = nhs->net;
struct synproxy_net *snet = synproxy_pernet(net);
enum ip_conntrack_info ctinfo;
struct nf_conn *ct;
struct nf_conn_synproxy *synproxy;
struct synproxy_options opts = {};
const struct ip_ct_tcp *state;
struct tcphdr *th, _th;
unsigned int thoff;
ct = nf_ct_get(skb, &ctinfo);
if (ct == NULL)
return NF_ACCEPT;
synproxy = nfct_synproxy(ct);
if (synproxy == NULL)
return NF_ACCEPT;
if (nf_is_loopback_packet(skb) ||
ip_hdr(skb)->protocol != IPPROTO_TCP)
return NF_ACCEPT;
thoff = ip_hdrlen(skb);
th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
if (th == NULL)
return NF_DROP;
state = &ct->proto.tcp;
switch (state->state) {
case TCP_CONNTRACK_CLOSE:
if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
ntohl(th->seq) + 1);
break;
}
if (!th->syn || th->ack ||
CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
break;
/* Reopened connection - reset the sequence number and timestamp
* adjustments, they will get initialized once the connection is
* reestablished.
*/
nf_ct_seqadj_init(ct, ctinfo, 0);
synproxy->tsoff = 0;
this_cpu_inc(snet->stats->conn_reopened);
/* fall through */
case TCP_CONNTRACK_SYN_SENT:
if (!synproxy_parse_options(skb, thoff, th, &opts))
return NF_DROP;
if (!th->syn && th->ack &&
CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
/* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
* therefore we need to add 1 to make the SYN sequence
* number match the one of first SYN.
*/
if (synproxy_recv_client_ack(net, skb, th, &opts,
ntohl(th->seq) + 1)) {
this_cpu_inc(snet->stats->cookie_retrans);
consume_skb(skb);
return NF_STOLEN;
} else {
return NF_DROP;
}
}
synproxy->isn = ntohl(th->ack_seq);
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
synproxy->its = opts.tsecr;
nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
break;
case TCP_CONNTRACK_SYN_RECV:
if (!th->syn || !th->ack)
break;
if (!synproxy_parse_options(skb, thoff, th, &opts))
return NF_DROP;
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) {
synproxy->tsoff = opts.tsval - synproxy->its;
nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
}
opts.options &= ~(XT_SYNPROXY_OPT_MSS |
XT_SYNPROXY_OPT_WSCALE |
XT_SYNPROXY_OPT_SACK_PERM);
swap(opts.tsval, opts.tsecr);
synproxy_send_server_ack(net, state, skb, th, &opts);
nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
nf_conntrack_event_cache(IPCT_SEQADJ, ct);
swap(opts.tsval, opts.tsecr);
synproxy_send_client_ack(net, skb, th, &opts);
consume_skb(skb);
return NF_STOLEN;
default:
break;
}
synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
return NF_ACCEPT;
}
static const struct nf_hook_ops ipv4_synproxy_ops[] = {
{
.hook = ipv4_synproxy_hook,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_LOCAL_IN,
.priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
},
{
.hook = ipv4_synproxy_hook,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_POST_ROUTING,
.priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
},
};
static int synproxy_tg4_check(const struct xt_tgchk_param *par)
{
struct synproxy_net *snet = synproxy_pernet(par->net);
@ -452,13 +76,10 @@ static int synproxy_tg4_check(const struct xt_tgchk_param *par)
if (err)
return err;
if (snet->hook_ref4 == 0) {
err = nf_register_net_hooks(par->net, ipv4_synproxy_ops,
ARRAY_SIZE(ipv4_synproxy_ops));
if (err) {
nf_ct_netns_put(par->net, par->family);
return err;
}
err = nf_synproxy_ipv4_init(snet, par->net);
if (err) {
nf_ct_netns_put(par->net, par->family);
return err;
}
snet->hook_ref4++;
@ -469,10 +90,7 @@ static void synproxy_tg4_destroy(const struct xt_tgdtor_param *par)
{
struct synproxy_net *snet = synproxy_pernet(par->net);
snet->hook_ref4--;
if (snet->hook_ref4 == 0)
nf_unregister_net_hooks(par->net, ipv4_synproxy_ops,
ARRAY_SIZE(ipv4_synproxy_ops));
nf_synproxy_ipv4_fini(snet, par->net);
nf_ct_netns_put(par->net, par->family);
}

420
net/ipv6/netfilter/ip6t_SYNPROXY.c
View File

@ -6,272 +6,11 @@
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ip6_checksum.h>
#include <net/ip6_route.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_SYNPROXY.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_synproxy.h>
#include <net/netfilter/nf_conntrack_ecache.h>
static struct ipv6hdr *
synproxy_build_ip(struct net *net, struct sk_buff *skb,
const struct in6_addr *saddr,
const struct in6_addr *daddr)
{
struct ipv6hdr *iph;
skb_reset_network_header(skb);
iph = skb_put(skb, sizeof(*iph));
ip6_flow_hdr(iph, 0, 0);
iph->hop_limit = net->ipv6.devconf_all->hop_limit;
iph->nexthdr = IPPROTO_TCP;
iph->saddr = *saddr;
iph->daddr = *daddr;
return iph;
}
static void
synproxy_send_tcp(struct net *net,
const struct sk_buff *skb, struct sk_buff *nskb,
struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
struct ipv6hdr *niph, struct tcphdr *nth,
unsigned int tcp_hdr_size)
{
struct dst_entry *dst;
struct flowi6 fl6;
nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
nskb->ip_summed = CHECKSUM_PARTIAL;
nskb->csum_start = (unsigned char *)nth - nskb->head;
nskb->csum_offset = offsetof(struct tcphdr, check);
memset(&fl6, 0, sizeof(fl6));
fl6.flowi6_proto = IPPROTO_TCP;
fl6.saddr = niph->saddr;
fl6.daddr = niph->daddr;
fl6.fl6_sport = nth->source;
fl6.fl6_dport = nth->dest;
security_skb_classify_flow((struct sk_buff *)skb, flowi6_to_flowi(&fl6));
dst = ip6_route_output(net, NULL, &fl6);
if (dst->error) {
dst_release(dst);
goto free_nskb;
}
dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
if (IS_ERR(dst))
goto free_nskb;
skb_dst_set(nskb, dst);
if (nfct) {
nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
nf_conntrack_get(nfct);
}
ip6_local_out(net, nskb->sk, nskb);
return;
free_nskb:
kfree_skb(nskb);
}
static void
synproxy_send_client_synack(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts)
{
struct sk_buff *nskb;
struct ipv6hdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
u16 mss = opts->mss;
iph = ipv6_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, &iph->daddr, &iph->saddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->dest;
nth->dest = th->source;
nth->seq = htonl(__cookie_v6_init_sequence(iph, th, &mss));
nth->ack_seq = htonl(ntohl(th->seq) + 1);
tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
if (opts->options & XT_SYNPROXY_OPT_ECN)
tcp_flag_word(nth) |= TCP_FLAG_ECE;
nth->doff = tcp_hdr_size / 4;
nth->window = 0;
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
}
static void
synproxy_send_server_syn(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts, u32 recv_seq)
{
struct synproxy_net *snet = synproxy_pernet(net);
struct sk_buff *nskb;
struct ipv6hdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
iph = ipv6_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, &iph->saddr, &iph->daddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->source;
nth->dest = th->dest;
nth->seq = htonl(recv_seq - 1);
/* ack_seq is used to relay our ISN to the synproxy hook to initialize
* sequence number translation once a connection tracking entry exists.
*/
nth->ack_seq = htonl(ntohl(th->ack_seq) - 1);
tcp_flag_word(nth) = TCP_FLAG_SYN;
if (opts->options & XT_SYNPROXY_OPT_ECN)
tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
nth->doff = tcp_hdr_size / 4;
nth->window = th->window;
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
niph, nth, tcp_hdr_size);
}
static void
synproxy_send_server_ack(struct net *net,
const struct ip_ct_tcp *state,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts)
{
struct sk_buff *nskb;
struct ipv6hdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
iph = ipv6_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, &iph->daddr, &iph->saddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->dest;
nth->dest = th->source;
nth->seq = htonl(ntohl(th->ack_seq));
nth->ack_seq = htonl(ntohl(th->seq) + 1);
tcp_flag_word(nth) = TCP_FLAG_ACK;
nth->doff = tcp_hdr_size / 4;
nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
}
static void
synproxy_send_client_ack(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
const struct synproxy_options *opts)
{
struct sk_buff *nskb;
struct ipv6hdr *iph, *niph;
struct tcphdr *nth;
unsigned int tcp_hdr_size;
iph = ipv6_hdr(skb);
tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
GFP_ATOMIC);
if (nskb == NULL)
return;
skb_reserve(nskb, MAX_TCP_HEADER);
niph = synproxy_build_ip(net, nskb, &iph->saddr, &iph->daddr);
skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
nth->source = th->source;
nth->dest = th->dest;
nth->seq = htonl(ntohl(th->seq) + 1);
nth->ack_seq = th->ack_seq;
tcp_flag_word(nth) = TCP_FLAG_ACK;
nth->doff = tcp_hdr_size / 4;
nth->window = htons(ntohs(th->window) >> opts->wscale);
nth->check = 0;
nth->urg_ptr = 0;
synproxy_build_options(nth, opts);
synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
}
static bool
synproxy_recv_client_ack(struct net *net,
const struct sk_buff *skb, const struct tcphdr *th,
struct synproxy_options *opts, u32 recv_seq)
{
struct synproxy_net *snet = synproxy_pernet(net);
int mss;
mss = __cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
if (mss == 0) {
this_cpu_inc(snet->stats->cookie_invalid);
return false;
}
this_cpu_inc(snet->stats->cookie_valid);
opts->mss = mss;
opts->options |= XT_SYNPROXY_OPT_MSS;
if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
synproxy_check_timestamp_cookie(opts);
synproxy_send_server_syn(net, skb, th, opts, recv_seq);
return true;
}
#include <net/netfilter/nf_synproxy.h>
static unsigned int
synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
@ -307,13 +46,14 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
XT_SYNPROXY_OPT_SACK_PERM |
XT_SYNPROXY_OPT_ECN);
synproxy_send_client_synack(net, skb, th, &opts);
synproxy_send_client_synack_ipv6(net, skb, th, &opts);
consume_skb(skb);
return NF_STOLEN;
} else if (th->ack && !(th->fin || th->rst || th->syn)) {
/* ACK from client */
if (synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq))) {
if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
ntohl(th->seq))) {
consume_skb(skb);
return NF_STOLEN;
} else {
@ -324,141 +64,6 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
return XT_CONTINUE;
}
static unsigned int ipv6_synproxy_hook(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *nhs)
{
struct net *net = nhs->net;
struct synproxy_net *snet = synproxy_pernet(net);
enum ip_conntrack_info ctinfo;
struct nf_conn *ct;
struct nf_conn_synproxy *synproxy;
struct synproxy_options opts = {};
const struct ip_ct_tcp *state;
struct tcphdr *th, _th;
__be16 frag_off;
u8 nexthdr;
int thoff;
ct = nf_ct_get(skb, &ctinfo);
if (ct == NULL)
return NF_ACCEPT;
synproxy = nfct_synproxy(ct);
if (synproxy == NULL)
return NF_ACCEPT;
if (nf_is_loopback_packet(skb))
return NF_ACCEPT;
nexthdr = ipv6_hdr(skb)->nexthdr;
thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
&frag_off);
if (thoff < 0 || nexthdr != IPPROTO_TCP)
return NF_ACCEPT;
th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
if (th == NULL)
return NF_DROP;
state = &ct->proto.tcp;
switch (state->state) {
case TCP_CONNTRACK_CLOSE:
if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
ntohl(th->seq) + 1);
break;
}
if (!th->syn || th->ack ||
CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
break;
/* Reopened connection - reset the sequence number and timestamp
* adjustments, they will get initialized once the connection is
* reestablished.
*/
nf_ct_seqadj_init(ct, ctinfo, 0);
synproxy->tsoff = 0;
this_cpu_inc(snet->stats->conn_reopened);
/* fall through */
case TCP_CONNTRACK_SYN_SENT:
if (!synproxy_parse_options(skb, thoff, th, &opts))
return NF_DROP;
if (!th->syn && th->ack &&
CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
/* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
* therefore we need to add 1 to make the SYN sequence
* number match the one of first SYN.
*/
if (synproxy_recv_client_ack(net, skb, th, &opts,
ntohl(th->seq) + 1)) {
this_cpu_inc(snet->stats->cookie_retrans);
consume_skb(skb);
return NF_STOLEN;
} else {
return NF_DROP;
}
}
synproxy->isn = ntohl(th->ack_seq);
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
synproxy->its = opts.tsecr;
nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
break;
case TCP_CONNTRACK_SYN_RECV:
if (!th->syn || !th->ack)
break;
if (!synproxy_parse_options(skb, thoff, th, &opts))
return NF_DROP;
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) {
synproxy->tsoff = opts.tsval - synproxy->its;
nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
}
opts.options &= ~(XT_SYNPROXY_OPT_MSS |
XT_SYNPROXY_OPT_WSCALE |
XT_SYNPROXY_OPT_SACK_PERM);
swap(opts.tsval, opts.tsecr);
synproxy_send_server_ack(net, state, skb, th, &opts);
nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
nf_conntrack_event_cache(IPCT_SEQADJ, ct);
swap(opts.tsval, opts.tsecr);
synproxy_send_client_ack(net, skb, th, &opts);
consume_skb(skb);
return NF_STOLEN;
default:
break;
}
synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
return NF_ACCEPT;
}
static const struct nf_hook_ops ipv6_synproxy_ops[] = {
{
.hook = ipv6_synproxy_hook,
.pf = NFPROTO_IPV6,
.hooknum = NF_INET_LOCAL_IN,
.priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
},
{
.hook = ipv6_synproxy_hook,
.pf = NFPROTO_IPV6,
.hooknum = NF_INET_POST_ROUTING,
.priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
},
};
static int synproxy_tg6_check(const struct xt_tgchk_param *par)
{
struct synproxy_net *snet = synproxy_pernet(par->net);
@ -474,16 +79,12 @@ static int synproxy_tg6_check(const struct xt_tgchk_param *par)
if (err)
return err;
if (snet->hook_ref6 == 0) {
err = nf_register_net_hooks(par->net, ipv6_synproxy_ops,
ARRAY_SIZE(ipv6_synproxy_ops));
if (err) {
nf_ct_netns_put(par->net, par->family);
return err;
}
err = nf_synproxy_ipv6_init(snet, par->net);
if (err) {
nf_ct_netns_put(par->net, par->family);
return err;
}
snet->hook_ref6++;
return err;
}
@ -491,10 +92,7 @@ static void synproxy_tg6_destroy(const struct xt_tgdtor_param *par)
{
struct synproxy_net *snet = synproxy_pernet(par->net);
snet->hook_ref6--;
if (snet->hook_ref6 == 0)
nf_unregister_net_hooks(par->net, ipv6_synproxy_ops,
ARRAY_SIZE(ipv6_synproxy_ops));
nf_synproxy_ipv6_fini(snet, par->net);
nf_ct_netns_put(par->net, par->family);
}

896
net/netfilter/nf_synproxy_core.c
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