diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h index 2a22bcbfe6e4..ff95434e50ca 100644 --- a/include/net/netfilter/nf_conntrack_extend.h +++ b/include/net/netfilter/nf_conntrack_extend.h @@ -9,8 +9,8 @@ enum nf_ct_ext_id { NF_CT_EXT_HELPER, #if defined(CONFIG_NF_NAT) || defined(CONFIG_NF_NAT_MODULE) NF_CT_EXT_NAT, - NF_CT_EXT_SEQADJ, #endif + NF_CT_EXT_SEQADJ, NF_CT_EXT_ACCT, #ifdef CONFIG_NF_CONNTRACK_EVENTS NF_CT_EXT_ECACHE, @@ -26,6 +26,9 @@ enum nf_ct_ext_id { #endif #ifdef CONFIG_NF_CONNTRACK_LABELS NF_CT_EXT_LABELS, +#endif +#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY) + NF_CT_EXT_SYNPROXY, #endif NF_CT_EXT_NUM, }; @@ -39,6 +42,7 @@ enum nf_ct_ext_id { #define NF_CT_EXT_TSTAMP_TYPE struct nf_conn_tstamp #define NF_CT_EXT_TIMEOUT_TYPE struct nf_conn_timeout #define NF_CT_EXT_LABELS_TYPE struct nf_conn_labels +#define NF_CT_EXT_SYNPROXY_TYPE struct nf_conn_synproxy /* Extensions: optional stuff which isn't permanently in struct. */ struct nf_ct_ext { diff --git a/include/net/netfilter/nf_conntrack_seqadj.h b/include/net/netfilter/nf_conntrack_seqadj.h index 30bfbbed9f47..f6177a5fe0ca 100644 --- a/include/net/netfilter/nf_conntrack_seqadj.h +++ b/include/net/netfilter/nf_conntrack_seqadj.h @@ -30,6 +30,8 @@ static inline struct nf_conn_seqadj *nfct_seqadj_ext_add(struct nf_conn *ct) return nf_ct_ext_add(ct, NF_CT_EXT_SEQADJ, GFP_ATOMIC); } +extern int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo, + s32 off); extern int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo, __be32 seq, s32 off); extern void nf_ct_tcp_seqadj_set(struct sk_buff *skb, diff --git a/include/net/netfilter/nf_conntrack_synproxy.h b/include/net/netfilter/nf_conntrack_synproxy.h new file mode 100644 index 000000000000..806f54a290d6 --- /dev/null +++ b/include/net/netfilter/nf_conntrack_synproxy.h @@ -0,0 +1,77 @@ +#ifndef _NF_CONNTRACK_SYNPROXY_H +#define _NF_CONNTRACK_SYNPROXY_H + +#include + +struct nf_conn_synproxy { + u32 isn; + u32 its; + u32 tsoff; +}; + +static inline struct nf_conn_synproxy *nfct_synproxy(const struct nf_conn *ct) +{ +#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY) + return nf_ct_ext_find(ct, NF_CT_EXT_SYNPROXY); +#else + return NULL; +#endif +} + +static inline struct nf_conn_synproxy *nfct_synproxy_ext_add(struct nf_conn *ct) +{ +#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY) + return nf_ct_ext_add(ct, NF_CT_EXT_SYNPROXY, GFP_ATOMIC); +#else + return NULL; +#endif +} + +struct synproxy_stats { + unsigned int syn_received; + unsigned int cookie_invalid; + unsigned int cookie_valid; + unsigned int cookie_retrans; + unsigned int conn_reopened; +}; + +struct synproxy_net { + struct nf_conn *tmpl; + struct synproxy_stats __percpu *stats; +}; + +extern int synproxy_net_id; +static inline struct synproxy_net *synproxy_pernet(struct net *net) +{ + return net_generic(net, synproxy_net_id); +} + +struct synproxy_options { + u8 options; + u8 wscale; + u16 mss; + u32 tsval; + u32 tsecr; +}; + +struct tcphdr; +struct xt_synproxy_info; +extern void synproxy_parse_options(const struct sk_buff *skb, unsigned int doff, + const struct tcphdr *th, + struct synproxy_options *opts); +extern unsigned int synproxy_options_size(const struct synproxy_options *opts); +extern void synproxy_build_options(struct tcphdr *th, + const struct synproxy_options *opts); + +extern void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info, + struct synproxy_options *opts); +extern void synproxy_check_timestamp_cookie(struct synproxy_options *opts); + +extern 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 */ diff --git a/include/uapi/linux/netfilter/xt_SYNPROXY.h b/include/uapi/linux/netfilter/xt_SYNPROXY.h new file mode 100644 index 000000000000..2d59fbaa93c6 --- /dev/null +++ b/include/uapi/linux/netfilter/xt_SYNPROXY.h @@ -0,0 +1,16 @@ +#ifndef _XT_SYNPROXY_H +#define _XT_SYNPROXY_H + +#define XT_SYNPROXY_OPT_MSS 0x01 +#define XT_SYNPROXY_OPT_WSCALE 0x02 +#define XT_SYNPROXY_OPT_SACK_PERM 0x04 +#define XT_SYNPROXY_OPT_TIMESTAMP 0x08 +#define XT_SYNPROXY_OPT_ECN 0x10 + +struct xt_synproxy_info { + __u8 options; + __u8 wscale; + __u16 mss; +}; + +#endif /* _XT_SYNPROXY_H */ diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig index 4e9028017428..1657e39b291f 100644 --- a/net/ipv4/netfilter/Kconfig +++ b/net/ipv4/netfilter/Kconfig @@ -110,6 +110,19 @@ config IP_NF_TARGET_REJECT To compile it as a module, choose M here. If unsure, say N. +config IP_NF_TARGET_SYNPROXY + tristate "SYNPROXY target support" + depends on NF_CONNTRACK && NETFILTER_ADVANCED + select NETFILTER_SYNPROXY + select SYN_COOKIES + help + The SYNPROXY target allows you to intercept TCP connections and + establish them using syncookies before they are passed on to the + server. This allows to avoid conntrack and server resource usage + during SYN-flood attacks. + + To compile it as a module, choose M here. If unsure, say N. + config IP_NF_TARGET_ULOG tristate "ULOG target support (obsolete)" default m if NETFILTER_ADVANCED=n diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile index 007b128eecc9..3622b248b6dd 100644 --- a/net/ipv4/netfilter/Makefile +++ b/net/ipv4/netfilter/Makefile @@ -46,6 +46,7 @@ obj-$(CONFIG_IP_NF_TARGET_CLUSTERIP) += ipt_CLUSTERIP.o obj-$(CONFIG_IP_NF_TARGET_ECN) += ipt_ECN.o obj-$(CONFIG_IP_NF_TARGET_MASQUERADE) += ipt_MASQUERADE.o obj-$(CONFIG_IP_NF_TARGET_REJECT) += ipt_REJECT.o +obj-$(CONFIG_IP_NF_TARGET_SYNPROXY) += ipt_SYNPROXY.o obj-$(CONFIG_IP_NF_TARGET_ULOG) += ipt_ULOG.o # generic ARP tables diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c new file mode 100644 index 000000000000..94371db6aecc --- /dev/null +++ b/net/ipv4/netfilter/ipt_SYNPROXY.c @@ -0,0 +1,472 @@ +/* + * Copyright (c) 2013 Patrick McHardy + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +static struct iphdr * +synproxy_build_ip(struct sk_buff *skb, u32 saddr, u32 daddr) +{ + struct iphdr *iph; + + skb_reset_network_header(skb); + iph = (struct iphdr *)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 = sysctl_ip_default_ttl; + iph->protocol = IPPROTO_TCP; + iph->check = 0; + iph->saddr = saddr; + iph->daddr = daddr; + + return iph; +} + +static void +synproxy_send_tcp(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(nskb, RTN_UNSPEC)) + goto free_nskb; + + if (nfct) { + nskb->nfct = nfct; + nskb->nfctinfo = ctinfo; + nf_conntrack_get(nfct); + } + + ip_local_out(nskb); + return; + +free_nskb: + kfree_skb(nskb); +} + +static void +synproxy_send_client_synack(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(nskb, iph->daddr, iph->saddr); + + skb_reset_transport_header(nskb); + nth = (struct tcphdr *)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(skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY, + niph, nth, tcp_hdr_size); +} + +static void +synproxy_send_server_syn(const struct synproxy_net *snet, + const struct sk_buff *skb, const struct tcphdr *th, + const struct synproxy_options *opts, u32 recv_seq) +{ + 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(nskb, iph->saddr, iph->daddr); + + skb_reset_transport_header(nskb); + nth = (struct tcphdr *)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(skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW, + niph, nth, tcp_hdr_size); +} + +static void +synproxy_send_server_ack(const struct synproxy_net *snet, + 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(nskb, iph->daddr, iph->saddr); + + skb_reset_transport_header(nskb); + nth = (struct tcphdr *)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(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size); +} + +static void +synproxy_send_client_ack(const struct synproxy_net *snet, + 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(nskb, iph->saddr, iph->daddr); + + skb_reset_transport_header(nskb); + nth = (struct tcphdr *)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 = ntohs(htons(th->window) >> opts->wscale); + nth->check = 0; + nth->urg_ptr = 0; + + synproxy_build_options(nth, opts); + + synproxy_send_tcp(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size); +} + +static bool +synproxy_recv_client_ack(const struct synproxy_net *snet, + const struct sk_buff *skb, const struct tcphdr *th, + struct synproxy_options *opts, u32 recv_seq) +{ + 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; + + if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP) + synproxy_check_timestamp_cookie(opts); + + synproxy_send_server_syn(snet, skb, th, opts, recv_seq); + return true; +} + +static unsigned int +synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par) +{ + const struct xt_synproxy_info *info = par->targinfo; + struct synproxy_net *snet = synproxy_pernet(dev_net(par->in)); + struct synproxy_options opts = {}; + struct tcphdr *th, _th; + + if (nf_ip_checksum(skb, par->hooknum, par->thoff, IPPROTO_TCP)) + return NF_DROP; + + th = skb_header_pointer(skb, par->thoff, sizeof(_th), &_th); + if (th == NULL) + return NF_DROP; + + synproxy_parse_options(skb, par->thoff, th, &opts); + + if (th->syn && !th->ack) { + /* Initial SYN from client */ + this_cpu_inc(snet->stats->syn_received); + + if (th->ece && th->cwr) + opts.options |= XT_SYNPROXY_OPT_ECN; + + opts.options &= info->options; + if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) + synproxy_init_timestamp_cookie(info, &opts); + else + opts.options &= ~(XT_SYNPROXY_OPT_WSCALE | + XT_SYNPROXY_OPT_SACK_PERM | + XT_SYNPROXY_OPT_ECN); + + synproxy_send_client_synack(skb, th, &opts); + } else if (th->ack && !(th->fin || th->rst)) + /* ACK from client */ + synproxy_recv_client_ack(snet, skb, th, &opts, ntohl(th->seq)); + + return NF_DROP; +} + +static unsigned int ipv4_synproxy_hook(unsigned int hooknum, + struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + int (*okfn)(struct sk_buff *)) +{ + struct synproxy_net *snet = synproxy_pernet(dev_net(in ? : out)); + 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)) + 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: + synproxy_parse_options(skb, thoff, th, &opts); + + 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(snet, skb, th, &opts, + ntohl(th->seq) + 1)) + this_cpu_inc(snet->stats->cookie_retrans); + + return NF_DROP; + } + + synproxy->isn = ntohl(th->ack_seq); + if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) + synproxy->its = opts.tsecr; + break; + case TCP_CONNTRACK_SYN_RECV: + if (!th->syn || !th->ack) + break; + + synproxy_parse_options(skb, thoff, th, &opts); + if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) + synproxy->tsoff = opts.tsval - synproxy->its; + + opts.options &= ~(XT_SYNPROXY_OPT_MSS | + XT_SYNPROXY_OPT_WSCALE | + XT_SYNPROXY_OPT_SACK_PERM); + + swap(opts.tsval, opts.tsecr); + synproxy_send_server_ack(snet, state, skb, th, &opts); + + nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq)); + + swap(opts.tsval, opts.tsecr); + synproxy_send_client_ack(snet, skb, th, &opts); + + consume_skb(skb); + return NF_STOLEN; + default: + break; + } + + synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy); + return NF_ACCEPT; +} + +static int synproxy_tg4_check(const struct xt_tgchk_param *par) +{ + const struct ipt_entry *e = par->entryinfo; + + if (e->ip.proto != IPPROTO_TCP || + e->ip.invflags & XT_INV_PROTO) + return -EINVAL; + + return nf_ct_l3proto_try_module_get(par->family); +} + +static void synproxy_tg4_destroy(const struct xt_tgdtor_param *par) +{ + nf_ct_l3proto_module_put(par->family); +} + +static struct xt_target synproxy_tg4_reg __read_mostly = { + .name = "SYNPROXY", + .family = NFPROTO_IPV4, + .target = synproxy_tg4, + .targetsize = sizeof(struct xt_synproxy_info), + .checkentry = synproxy_tg4_check, + .destroy = synproxy_tg4_destroy, + .me = THIS_MODULE, +}; + +static struct nf_hook_ops ipv4_synproxy_ops[] __read_mostly = { + { + .hook = ipv4_synproxy_hook, + .owner = THIS_MODULE, + .pf = NFPROTO_IPV4, + .hooknum = NF_INET_LOCAL_IN, + .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1, + }, + { + .hook = ipv4_synproxy_hook, + .owner = THIS_MODULE, + .pf = NFPROTO_IPV4, + .hooknum = NF_INET_POST_ROUTING, + .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1, + }, +}; + +static int __init synproxy_tg4_init(void) +{ + int err; + + err = nf_register_hooks(ipv4_synproxy_ops, + ARRAY_SIZE(ipv4_synproxy_ops)); + if (err < 0) + goto err1; + + err = xt_register_target(&synproxy_tg4_reg); + if (err < 0) + goto err2; + + return 0; + +err2: + nf_unregister_hooks(ipv4_synproxy_ops, ARRAY_SIZE(ipv4_synproxy_ops)); +err1: + return err; +} + +static void __exit synproxy_tg4_exit(void) +{ + xt_unregister_target(&synproxy_tg4_reg); + nf_unregister_hooks(ipv4_synproxy_ops, ARRAY_SIZE(ipv4_synproxy_ops)); +} + +module_init(synproxy_tg4_init); +module_exit(synproxy_tg4_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Patrick McHardy "); diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index c45fc1a60e0d..62a171ab204f 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -408,6 +408,9 @@ config NF_NAT_TFTP depends on NF_CONNTRACK && NF_NAT default NF_NAT && NF_CONNTRACK_TFTP +config NETFILTER_SYNPROXY + tristate + endif # NF_CONNTRACK config NETFILTER_XTABLES diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index 89a9c1658f5e..c3a0a12907f6 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -61,6 +61,9 @@ obj-$(CONFIG_NF_NAT_IRC) += nf_nat_irc.o obj-$(CONFIG_NF_NAT_SIP) += nf_nat_sip.o obj-$(CONFIG_NF_NAT_TFTP) += nf_nat_tftp.o +# SYNPROXY +obj-$(CONFIG_NETFILTER_SYNPROXY) += nf_synproxy_core.o + # generic X tables obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 00a7a94d4132..5d892febd64c 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -48,6 +48,7 @@ #include #include #include +#include #include #include #include @@ -799,6 +800,11 @@ init_conntrack(struct net *net, struct nf_conn *tmpl, if (IS_ERR(ct)) return (struct nf_conntrack_tuple_hash *)ct; + if (tmpl && nfct_synproxy(tmpl)) { + nfct_seqadj_ext_add(ct); + nfct_synproxy_ext_add(ct); + } + timeout_ext = tmpl ? nf_ct_timeout_find(tmpl) : NULL; if (timeout_ext) timeouts = NF_CT_TIMEOUT_EXT_DATA(timeout_ext); diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index 984a8d1a3359..44d1ea32570a 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include #include @@ -946,6 +947,21 @@ static int tcp_packet(struct nf_conn *ct, "state %s ", tcp_conntrack_names[old_state]); return NF_ACCEPT; case TCP_CONNTRACK_MAX: + /* Special case for SYN proxy: when the SYN to the server or + * the SYN/ACK from the server is lost, the client may transmit + * a keep-alive packet while in SYN_SENT state. This needs to + * be associated with the original conntrack entry in order to + * generate a new SYN with the correct sequence number. + */ + if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT && + index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL && + ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL && + ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) { + pr_debug("nf_ct_tcp: SYN proxy client keep alive\n"); + spin_unlock_bh(&ct->lock); + return NF_ACCEPT; + } + /* Invalid packet */ pr_debug("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n", dir, get_conntrack_index(th), old_state); diff --git a/net/netfilter/nf_conntrack_seqadj.c b/net/netfilter/nf_conntrack_seqadj.c index 483eb9ce3216..5f9bfd060dea 100644 --- a/net/netfilter/nf_conntrack_seqadj.c +++ b/net/netfilter/nf_conntrack_seqadj.c @@ -6,6 +6,26 @@ #include #include +int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo, + s32 off) +{ + enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + struct nf_conn_seqadj *seqadj; + struct nf_ct_seqadj *this_way; + + if (off == 0) + return 0; + + set_bit(IPS_SEQ_ADJUST_BIT, &ct->status); + + seqadj = nfct_seqadj(ct); + this_way = &seqadj->seq[dir]; + this_way->offset_before = off; + this_way->offset_after = off; + return 0; +} +EXPORT_SYMBOL_GPL(nf_ct_seqadj_init); + int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo, __be32 seq, s32 off) { diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c new file mode 100644 index 000000000000..d23dc791aca7 --- /dev/null +++ b/net/netfilter/nf_synproxy_core.c @@ -0,0 +1,432 @@ +/* + * Copyright (c) 2013 Patrick McHardy + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include + +int synproxy_net_id; +EXPORT_SYMBOL_GPL(synproxy_net_id); + +void +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; + + ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf); + BUG_ON(ptr == NULL); + + opts->options = 0; + while (length > 0) { + int opcode = *ptr++; + int opsize; + + switch (opcode) { + case TCPOPT_EOL: + return; + case TCPOPT_NOP: + length--; + continue; + default: + opsize = *ptr++; + if (opsize < 2) + return; + if (opsize > length) + return; + + switch (opcode) { + case TCPOPT_MSS: + if (opsize == TCPOLEN_MSS) { + opts->mss = get_unaligned_be16(ptr); + opts->options |= XT_SYNPROXY_OPT_MSS; + } + break; + case TCPOPT_WINDOW: + if (opsize == TCPOLEN_WINDOW) { + opts->wscale = *ptr; + if (opts->wscale > 14) + opts->wscale = 14; + opts->options |= XT_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 |= XT_SYNPROXY_OPT_TIMESTAMP; + } + break; + case TCPOPT_SACK_PERM: + if (opsize == TCPOLEN_SACK_PERM) + opts->options |= XT_SYNPROXY_OPT_SACK_PERM; + break; + } + + ptr += opsize - 2; + length -= opsize; + } + } +} +EXPORT_SYMBOL_GPL(synproxy_parse_options); + +unsigned int synproxy_options_size(const struct synproxy_options *opts) +{ + unsigned int size = 0; + + if (opts->options & XT_SYNPROXY_OPT_MSS) + size += TCPOLEN_MSS_ALIGNED; + if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP) + size += TCPOLEN_TSTAMP_ALIGNED; + else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) + size += TCPOLEN_SACKPERM_ALIGNED; + if (opts->options & XT_SYNPROXY_OPT_WSCALE) + size += TCPOLEN_WSCALE_ALIGNED; + + return size; +} +EXPORT_SYMBOL_GPL(synproxy_options_size); + +void +synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts) +{ + __be32 *ptr = (__be32 *)(th + 1); + u8 options = opts->options; + + if (options & XT_SYNPROXY_OPT_MSS) + *ptr++ = htonl((TCPOPT_MSS << 24) | + (TCPOLEN_MSS << 16) | + opts->mss); + + if (options & XT_SYNPROXY_OPT_TIMESTAMP) { + if (options & XT_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 & XT_SYNPROXY_OPT_SACK_PERM) + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_SACK_PERM << 8) | + TCPOLEN_SACK_PERM); + + if (options & XT_SYNPROXY_OPT_WSCALE) + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_WINDOW << 16) | + (TCPOLEN_WINDOW << 8) | + opts->wscale); +} +EXPORT_SYMBOL_GPL(synproxy_build_options); + +void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info, + struct synproxy_options *opts) +{ + opts->tsecr = opts->tsval; + opts->tsval = tcp_time_stamp & ~0x3f; + + if (opts->options & XT_SYNPROXY_OPT_WSCALE) + opts->tsval |= info->wscale; + else + opts->tsval |= 0xf; + + if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) + opts->tsval |= 1 << 4; + + if (opts->options & XT_SYNPROXY_OPT_ECN) + opts->tsval |= 1 << 5; +} +EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie); + +void synproxy_check_timestamp_cookie(struct synproxy_options *opts) +{ + opts->wscale = opts->tsecr & 0xf; + if (opts->wscale != 0xf) + opts->options |= XT_SYNPROXY_OPT_WSCALE; + + opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0; + + opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0; +} +EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie); + +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; + u32 *ptr, old; + + if (synproxy->tsoff == 0) + return 1; + + optoff = protoff + sizeof(struct tcphdr); + optend = protoff + th->doff * 4; + + if (!skb_make_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 = (u32 *)&op[2]; + old = *ptr; + *ptr = htonl(ntohl(*ptr) - + synproxy->tsoff); + } else { + ptr = (u32 *)&op[6]; + old = *ptr; + *ptr = htonl(ntohl(*ptr) + + synproxy->tsoff); + } + inet_proto_csum_replace4(&th->check, skb, + old, *ptr, 0); + return 1; + } + optoff += op[1]; + } + } + return 1; +} +EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust); + +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); + } + + 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_printf(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 synproxy_cpu_seq_open(struct inode *inode, struct file *file) +{ + return seq_open_net(inode, file, &synproxy_cpu_seq_ops, + sizeof(struct seq_net_private)); +} + +static const struct file_operations synproxy_cpu_seq_fops = { + .owner = THIS_MODULE, + .open = synproxy_cpu_seq_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release_net, +}; + +static int __net_init synproxy_proc_init(struct net *net) +{ + if (!proc_create("synproxy", S_IRUGO, net->proc_net_stat, + &synproxy_cpu_seq_fops)) + 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_conntrack_tuple t; + struct nf_conn *ct; + int err = -ENOMEM; + + memset(&t, 0, sizeof(t)); + ct = nf_conntrack_alloc(net, 0, &t, &t, GFP_KERNEL); + if (IS_ERR(ct)) { + err = PTR_ERR(ct); + goto err1; + } + + __set_bit(IPS_TEMPLATE_BIT, &ct->status); + __set_bit(IPS_CONFIRMED_BIT, &ct->status); + if (!nfct_seqadj_ext_add(ct)) + goto err2; + if (!nfct_synproxy_ext_add(ct)) + goto err2; + + 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_conntrack_free(ct); +err1: + return err; +} + +static void __net_exit synproxy_net_exit(struct net *net) +{ + struct synproxy_net *snet = synproxy_pernet(net); + + nf_conntrack_free(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); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Patrick McHardy ");