1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991001011021031041051061071081091101111121131141151161171181191201211221231241251261271281291301311321331341351361371381391401411421431441451461471481491501511521531541551561571581591601611621631641651661671681691701711721731741751761771781791801811821831841851861871881891901911921931941951961971981992002012022032042052062072082092102112122132142152162172182192202212222232242252262272282292302312322332342352362372382392402412422432442452462472482492502512522532542552562572582592602612622632642652662672682692702712722732742752762772782792802812822832842852862872882892902912922932942952962972982993003013023033043053063073083093103113123133143153163173183193203213223233243253263273283293303313323333343353363373383393403413423433443453463473483493503513523533543553563573583593603613623633643653663673683693703713723733743753763773783793803813823833843853863873883893903913923933943953963973983994004014024034044054064074084094104114124134144154164174184194204214224234244254264274284294304314324334344354364374384394404414424434444454464474484494504514524534544554564574584594604614624634644654664674684694704714724734744754764774784794804814824834844854864874884894904914924934944954964974984995005015025035045055065075085095105115125135145155165175185195205215225235245255265275285295305315325335345355365375385395405415425435445455465475485495505515525535545555565575585595605615625635645655665675685695705715725735745755765775785795805815825835845855865875885895905915925935945955965975985996006016026036046056066076086096106116126136146156166176186196206216226236246256266276286296306316326336346356366376386396406416426436446456466476486496506516526536546556566576586596606616626636646656666676686696706716726736746756766776786796806816826836846856866876886896906916926936946956966976986997007017027037047057067077087097107117127137147157167177187197207217227237247257267277287297307317327337347357367377387397407417427437447457467477487497507517527537547557567577587597607617627637647657667677687697707717727737747757767777787797807817827837847857867877887897907917927937947957967977987998008018028038048058068078088098108118128138148158168178188198208218228238248258268278288298308318328338348358368378388398408418428438448458468478488498508518528538548558568578588598608618628638648658668678688698708718728738748758768778788798808818828838848858868878888898908918928938948958968978988999009019029039049059069079089099109119129139149159169179189199209219229239249259269279289299309319329339349359369379389399409419429439449459469479489499509519529539549559569579589599609619629639649659669679689699709719729739749759769779789799809819829839849859869879889899909919929939949959969979989991000100110021003100410051006100710081009101010111012101310141015101610171018101910201021102210231024102510261027102810291030103110321033103410351036103710381039104010411042104310441045104610471048104910501051105210531054105510561057105810591060106110621063106410651066106710681069107010711072107310741075107610771078107910801081108210831084108510861087108810891090109110921093109410951096109710981099110011011102110311041105110611071108110911101111111211131114111511161117111811191120112111221123112411251126112711281129113011311132113311341135113611371138113911401141114211431144114511461147114811491150115111521153115411551156115711581159116011611162116311641165116611671168116911701171117211731174117511761177117811791180118111821183118411851186118711881189119011911192119311941195119611971198119912001201120212031204120512061207120812091210121112121213121412151216121712181219122012211222122312241225122612271228122912301231123212331234123512361237123812391240124112421243 |
- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
- */
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <asm/unaligned.h>
- #include <net/tcp.h>
- #include <net/netns/generic.h>
- #include <linux/proc_fs.h>
- #include <linux/netfilter_ipv6.h>
- #include <linux/netfilter/nf_synproxy.h>
- #include <net/netfilter/nf_conntrack.h>
- #include <net/netfilter/nf_conntrack_ecache.h>
- #include <net/netfilter/nf_conntrack_extend.h>
- #include <net/netfilter/nf_conntrack_seqadj.h>
- #include <net/netfilter/nf_conntrack_synproxy.h>
- #include <net/netfilter/nf_conntrack_zones.h>
- #include <net/netfilter/nf_synproxy.h>
- unsigned int synproxy_net_id;
- EXPORT_SYMBOL_GPL(synproxy_net_id);
- bool
- synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
- const struct tcphdr *th, struct synproxy_options *opts)
- {
- int length = (th->doff * 4) - sizeof(*th);
- u8 buf[40], *ptr;
- if (unlikely(length < 0))
- return false;
- ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
- if (ptr == NULL)
- return false;
- opts->options = 0;
- while (length > 0) {
- int opcode = *ptr++;
- int opsize;
- switch (opcode) {
- case TCPOPT_EOL:
- return true;
- case TCPOPT_NOP:
- length--;
- continue;
- default:
- if (length < 2)
- return true;
- opsize = *ptr++;
- if (opsize < 2)
- return true;
- if (opsize > length)
- return true;
- switch (opcode) {
- case TCPOPT_MSS:
- if (opsize == TCPOLEN_MSS) {
- opts->mss_option = get_unaligned_be16(ptr);
- opts->options |= NF_SYNPROXY_OPT_MSS;
- }
- break;
- case TCPOPT_WINDOW:
- if (opsize == TCPOLEN_WINDOW) {
- opts->wscale = *ptr;
- if (opts->wscale > TCP_MAX_WSCALE)
- opts->wscale = TCP_MAX_WSCALE;
- opts->options |= NF_SYNPROXY_OPT_WSCALE;
- }
- break;
- case TCPOPT_TIMESTAMP:
- if (opsize == TCPOLEN_TIMESTAMP) {
- opts->tsval = get_unaligned_be32(ptr);
- opts->tsecr = get_unaligned_be32(ptr + 4);
- opts->options |= NF_SYNPROXY_OPT_TIMESTAMP;
- }
- break;
- case TCPOPT_SACK_PERM:
- if (opsize == TCPOLEN_SACK_PERM)
- opts->options |= NF_SYNPROXY_OPT_SACK_PERM;
- break;
- }
- ptr += opsize - 2;
- length -= opsize;
- }
- }
- return true;
- }
- EXPORT_SYMBOL_GPL(synproxy_parse_options);
- static unsigned int
- synproxy_options_size(const struct synproxy_options *opts)
- {
- unsigned int size = 0;
- if (opts->options & NF_SYNPROXY_OPT_MSS)
- size += TCPOLEN_MSS_ALIGNED;
- if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
- size += TCPOLEN_TSTAMP_ALIGNED;
- else if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
- size += TCPOLEN_SACKPERM_ALIGNED;
- if (opts->options & NF_SYNPROXY_OPT_WSCALE)
- size += TCPOLEN_WSCALE_ALIGNED;
- return size;
- }
- static void
- synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts)
- {
- __be32 *ptr = (__be32 *)(th + 1);
- u8 options = opts->options;
- if (options & NF_SYNPROXY_OPT_MSS)
- *ptr++ = htonl((TCPOPT_MSS << 24) |
- (TCPOLEN_MSS << 16) |
- opts->mss_option);
- if (options & NF_SYNPROXY_OPT_TIMESTAMP) {
- if (options & NF_SYNPROXY_OPT_SACK_PERM)
- *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
- (TCPOLEN_SACK_PERM << 16) |
- (TCPOPT_TIMESTAMP << 8) |
- TCPOLEN_TIMESTAMP);
- else
- *ptr++ = htonl((TCPOPT_NOP << 24) |
- (TCPOPT_NOP << 16) |
- (TCPOPT_TIMESTAMP << 8) |
- TCPOLEN_TIMESTAMP);
- *ptr++ = htonl(opts->tsval);
- *ptr++ = htonl(opts->tsecr);
- } else if (options & NF_SYNPROXY_OPT_SACK_PERM)
- *ptr++ = htonl((TCPOPT_NOP << 24) |
- (TCPOPT_NOP << 16) |
- (TCPOPT_SACK_PERM << 8) |
- TCPOLEN_SACK_PERM);
- if (options & NF_SYNPROXY_OPT_WSCALE)
- *ptr++ = htonl((TCPOPT_NOP << 24) |
- (TCPOPT_WINDOW << 16) |
- (TCPOLEN_WINDOW << 8) |
- opts->wscale);
- }
- void synproxy_init_timestamp_cookie(const struct nf_synproxy_info *info,
- struct synproxy_options *opts)
- {
- opts->tsecr = opts->tsval;
- opts->tsval = tcp_time_stamp_raw() & ~0x3f;
- if (opts->options & NF_SYNPROXY_OPT_WSCALE) {
- opts->tsval |= opts->wscale;
- opts->wscale = info->wscale;
- } else
- opts->tsval |= 0xf;
- if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
- opts->tsval |= 1 << 4;
- if (opts->options & NF_SYNPROXY_OPT_ECN)
- opts->tsval |= 1 << 5;
- }
- EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
- static void
- synproxy_check_timestamp_cookie(struct synproxy_options *opts)
- {
- opts->wscale = opts->tsecr & 0xf;
- if (opts->wscale != 0xf)
- opts->options |= NF_SYNPROXY_OPT_WSCALE;
- opts->options |= opts->tsecr & (1 << 4) ? NF_SYNPROXY_OPT_SACK_PERM : 0;
- opts->options |= opts->tsecr & (1 << 5) ? NF_SYNPROXY_OPT_ECN : 0;
- }
- static 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)
- {
- unsigned int optoff, optend;
- __be32 *ptr, old;
- if (synproxy->tsoff == 0)
- return 1;
- optoff = protoff + sizeof(struct tcphdr);
- optend = protoff + th->doff * 4;
- if (skb_ensure_writable(skb, optend))
- return 0;
- while (optoff < optend) {
- unsigned char *op = skb->data + optoff;
- switch (op[0]) {
- case TCPOPT_EOL:
- return 1;
- case TCPOPT_NOP:
- optoff++;
- continue;
- default:
- if (optoff + 1 == optend ||
- optoff + op[1] > optend ||
- op[1] < 2)
- return 0;
- if (op[0] == TCPOPT_TIMESTAMP &&
- op[1] == TCPOLEN_TIMESTAMP) {
- if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
- ptr = (__be32 *)&op[2];
- old = *ptr;
- *ptr = htonl(ntohl(*ptr) -
- synproxy->tsoff);
- } else {
- ptr = (__be32 *)&op[6];
- old = *ptr;
- *ptr = htonl(ntohl(*ptr) +
- synproxy->tsoff);
- }
- inet_proto_csum_replace4(&th->check, skb,
- old, *ptr, false);
- return 1;
- }
- optoff += op[1];
- }
- }
- return 1;
- }
- static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
- .len = sizeof(struct nf_conn_synproxy),
- .align = __alignof__(struct nf_conn_synproxy),
- .id = NF_CT_EXT_SYNPROXY,
- };
- #ifdef CONFIG_PROC_FS
- static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
- {
- struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
- int cpu;
- if (*pos == 0)
- return SEQ_START_TOKEN;
- for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
- if (!cpu_possible(cpu))
- continue;
- *pos = cpu + 1;
- return per_cpu_ptr(snet->stats, cpu);
- }
- return NULL;
- }
- static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
- {
- struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
- int cpu;
- for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
- if (!cpu_possible(cpu))
- continue;
- *pos = cpu + 1;
- return per_cpu_ptr(snet->stats, cpu);
- }
- (*pos)++;
- return NULL;
- }
- static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
- {
- return;
- }
- static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
- {
- struct synproxy_stats *stats = v;
- if (v == SEQ_START_TOKEN) {
- seq_puts(seq, "entries\t\tsyn_received\t"
- "cookie_invalid\tcookie_valid\t"
- "cookie_retrans\tconn_reopened\n");
- return 0;
- }
- seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
- stats->syn_received,
- stats->cookie_invalid,
- stats->cookie_valid,
- stats->cookie_retrans,
- stats->conn_reopened);
- return 0;
- }
- static const struct seq_operations synproxy_cpu_seq_ops = {
- .start = synproxy_cpu_seq_start,
- .next = synproxy_cpu_seq_next,
- .stop = synproxy_cpu_seq_stop,
- .show = synproxy_cpu_seq_show,
- };
- static int __net_init synproxy_proc_init(struct net *net)
- {
- if (!proc_create_net("synproxy", 0444, net->proc_net_stat,
- &synproxy_cpu_seq_ops, sizeof(struct seq_net_private)))
- return -ENOMEM;
- return 0;
- }
- static void __net_exit synproxy_proc_exit(struct net *net)
- {
- remove_proc_entry("synproxy", net->proc_net_stat);
- }
- #else
- static int __net_init synproxy_proc_init(struct net *net)
- {
- return 0;
- }
- static void __net_exit synproxy_proc_exit(struct net *net)
- {
- return;
- }
- #endif /* CONFIG_PROC_FS */
- static int __net_init synproxy_net_init(struct net *net)
- {
- struct synproxy_net *snet = synproxy_pernet(net);
- struct nf_conn *ct;
- int err = -ENOMEM;
- ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL);
- if (!ct)
- goto err1;
- if (!nfct_seqadj_ext_add(ct))
- goto err2;
- if (!nfct_synproxy_ext_add(ct))
- goto err2;
- __set_bit(IPS_CONFIRMED_BIT, &ct->status);
- nf_conntrack_get(&ct->ct_general);
- snet->tmpl = ct;
- snet->stats = alloc_percpu(struct synproxy_stats);
- if (snet->stats == NULL)
- goto err2;
- err = synproxy_proc_init(net);
- if (err < 0)
- goto err3;
- return 0;
- err3:
- free_percpu(snet->stats);
- err2:
- nf_ct_tmpl_free(ct);
- err1:
- return err;
- }
- static void __net_exit synproxy_net_exit(struct net *net)
- {
- struct synproxy_net *snet = synproxy_pernet(net);
- nf_ct_put(snet->tmpl);
- synproxy_proc_exit(net);
- free_percpu(snet->stats);
- }
- static struct pernet_operations synproxy_net_ops = {
- .init = synproxy_net_init,
- .exit = synproxy_net_exit,
- .id = &synproxy_net_id,
- .size = sizeof(struct synproxy_net),
- };
- static int __init synproxy_core_init(void)
- {
- int err;
- err = nf_ct_extend_register(&nf_ct_synproxy_extend);
- if (err < 0)
- goto err1;
- err = register_pernet_subsys(&synproxy_net_ops);
- if (err < 0)
- goto err2;
- return 0;
- err2:
- nf_ct_extend_unregister(&nf_ct_synproxy_extend);
- err1:
- return err;
- }
- static void __exit synproxy_core_exit(void)
- {
- unregister_pernet_subsys(&synproxy_net_ops);
- nf_ct_extend_unregister(&nf_ct_synproxy_extend);
- }
- module_init(synproxy_core_init);
- module_exit(synproxy_core_exit);
- 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->sk, 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);
- }
- 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_encode;
- 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)
- 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 & NF_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);
- }
- EXPORT_SYMBOL_GPL(synproxy_send_client_synack);
- 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)
- 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 & NF_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)
- 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)
- 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);
- }
- 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_option = mss;
- opts->options |= NF_SYNPROXY_OPT_MSS;
- if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
- synproxy_check_timestamp_cookie(opts);
- synproxy_send_server_syn(net, skb, th, opts, recv_seq);
- return true;
- }
- EXPORT_SYMBOL_GPL(synproxy_recv_client_ack);
- 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)
- return NF_ACCEPT;
- synproxy = nfct_synproxy(ct);
- if (!synproxy)
- 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)
- return NF_DROP;
- state = &ct->proto.tcp;
- switch (state->state) {
- case TCP_CONNTRACK_CLOSE:
- if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
- 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);
- fallthrough;
- 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 & NF_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 & NF_SYNPROXY_OPT_TIMESTAMP) {
- synproxy->tsoff = opts.tsval - synproxy->its;
- nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
- }
- opts.options &= ~(NF_SYNPROXY_OPT_MSS |
- NF_SYNPROXY_OPT_WSCALE |
- NF_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;
- }
- EXPORT_SYMBOL_GPL(ipv4_synproxy_hook);
- 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,
- },
- };
- int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net)
- {
- int err;
- if (snet->hook_ref4 == 0) {
- err = nf_register_net_hooks(net, ipv4_synproxy_ops,
- ARRAY_SIZE(ipv4_synproxy_ops));
- if (err)
- return err;
- }
- snet->hook_ref4++;
- return 0;
- }
- EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_init);
- void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net)
- {
- snet->hook_ref4--;
- if (snet->hook_ref4 == 0)
- nf_unregister_net_hooks(net, ipv4_synproxy_ops,
- ARRAY_SIZE(ipv4_synproxy_ops));
- }
- EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_fini);
- #if IS_ENABLED(CONFIG_IPV6)
- static struct ipv6hdr *
- synproxy_build_ip_ipv6(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_ipv6(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;
- int err;
- 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));
- err = nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
- if (err) {
- 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);
- }
- void
- synproxy_send_client_synack_ipv6(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_encode;
- 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)
- return;
- skb_reserve(nskb, MAX_TCP_HEADER);
- niph = synproxy_build_ip_ipv6(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(nf_ipv6_cookie_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 & NF_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_ipv6(net, skb, nskb, skb_nfct(skb),
- IP_CT_ESTABLISHED_REPLY, niph, nth,
- tcp_hdr_size);
- }
- EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);
- static void
- synproxy_send_server_syn_ipv6(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)
- return;
- skb_reserve(nskb, MAX_TCP_HEADER);
- niph = synproxy_build_ip_ipv6(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 & NF_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_ipv6(net, skb, nskb, &snet->tmpl->ct_general,
- IP_CT_NEW, niph, nth, tcp_hdr_size);
- }
- static void
- synproxy_send_server_ack_ipv6(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)
- return;
- skb_reserve(nskb, MAX_TCP_HEADER);
- niph = synproxy_build_ip_ipv6(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_ipv6(net, skb, nskb, NULL, 0, niph, nth,
- tcp_hdr_size);
- }
- static void
- synproxy_send_client_ack_ipv6(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)
- return;
- skb_reserve(nskb, MAX_TCP_HEADER);
- niph = synproxy_build_ip_ipv6(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_ipv6(net, skb, nskb, skb_nfct(skb),
- IP_CT_ESTABLISHED_REPLY, niph, nth,
- tcp_hdr_size);
- }
- 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)
- {
- struct synproxy_net *snet = synproxy_pernet(net);
- int mss;
- mss = nf_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_option = mss;
- opts->options |= NF_SYNPROXY_OPT_MSS;
- if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
- synproxy_check_timestamp_cookie(opts);
- synproxy_send_server_syn_ipv6(net, skb, th, opts, recv_seq);
- return true;
- }
- EXPORT_SYMBOL_GPL(synproxy_recv_client_ack_ipv6);
- 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)
- return NF_ACCEPT;
- synproxy = nfct_synproxy(ct);
- if (!synproxy)
- 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)
- return NF_DROP;
- state = &ct->proto.tcp;
- switch (state->state) {
- case TCP_CONNTRACK_CLOSE:
- if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
- 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);
- fallthrough;
- 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_ipv6(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 & NF_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 & NF_SYNPROXY_OPT_TIMESTAMP) {
- synproxy->tsoff = opts.tsval - synproxy->its;
- nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
- }
- opts.options &= ~(NF_SYNPROXY_OPT_MSS |
- NF_SYNPROXY_OPT_WSCALE |
- NF_SYNPROXY_OPT_SACK_PERM);
- swap(opts.tsval, opts.tsecr);
- synproxy_send_server_ack_ipv6(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_ipv6(net, skb, th, &opts);
- consume_skb(skb);
- return NF_STOLEN;
- default:
- break;
- }
- synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
- return NF_ACCEPT;
- }
- EXPORT_SYMBOL_GPL(ipv6_synproxy_hook);
- 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,
- },
- };
- int
- nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net)
- {
- int err;
- if (snet->hook_ref6 == 0) {
- err = nf_register_net_hooks(net, ipv6_synproxy_ops,
- ARRAY_SIZE(ipv6_synproxy_ops));
- if (err)
- return err;
- }
- snet->hook_ref6++;
- return 0;
- }
- EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_init);
- void
- nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net)
- {
- snet->hook_ref6--;
- if (snet->hook_ref6 == 0)
- nf_unregister_net_hooks(net, ipv6_synproxy_ops,
- ARRAY_SIZE(ipv6_synproxy_ops));
- }
- EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_fini);
- #endif /* CONFIG_IPV6 */
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
- MODULE_DESCRIPTION("nftables SYNPROXY expression support");
|